JP7002507B2 - Wireless communication device and wireless communication method - Google Patents

Description

Embodiments of the present invention relate to wireless communication terminals and wireless communication methods.

Consider performing multi-user communication (multiplex communication) between a base station and a plurality of wireless communication terminals (hereinafter referred to as terminals). Uplink multi-user communication is described as UL-MU (UpLink Multi-User) communication, and downlink multi-user communication is described as DL-MU (DownLink Multi-User) communication.

As multi-user communication, consider frequency division multiplexing in which different frequency components are allocated to each terminal as communication resources, and transmission to multiple terminals or reception from multiple terminals is performed at the same time. Here, a resource unit including one or more subcarriers is defined as a frequency component, and the frequency component is assigned to a terminal as a minimum unit communication resource to transmit to or receive from a plurality of terminals. Consider a orthogonal frequency division multiple access (OFDMA; Orthogonal Frequency Division Access) that is performed at the same time. Simultaneous transmission from a base station to a plurality of terminals corresponds to downlink OFDMA (DL-OFDMA), and simultaneous transmission from a plurality of terminals to a base station corresponds to uplink OFDMA (UL-OFDMA). DL-OFDA is an example of DL-MU, and UL-OFDA is an example of UL-MU.

When performing UL-OFDMA, in order to align the timing of uplink transmission, it is conceivable that the base station transmits a trigger frame that specifies the terminal targeted for UL-OFDMA and the resource unit assigned to the terminal. Be done. In this method, the resource unit assigned to the specified terminal is not effectively used, such as when the specified terminal is in sleep mode or the specified terminal does not have a request for uplink transmission, and communication resources are used. There is a problem of reduced efficiency.

Alternatively, in the trigger frame, the terminal is not specified and only the resource unit to be used is specified. At this time, the terminal may be specified for some resource units and the terminal may not be specified for another resource unit. In either case, among the terminals that received the trigger frame, the terminal to which no resource unit is assigned is randomly selected from the resource unit (sometimes called "STA unspecified RU") for which no terminal is specified. Select and use the unit. A trigger frame including the designation of the STA undesignated RU in this way may be referred to as a random access trigger frame.

The following methods are available as a method of randomly selecting a resource unit. Every time a random access trigger frame is received, the value corresponding to the number of STA unspecified RUs is counted down from the random number (backoff value) selected from the contention window (CW) for random access. When the backoff value after the countdown becomes 0 or less, the access right to the STA undesignated RU is acquired, the resource unit is randomly selected from the STA undesignated RU, and the frame is transmitted by the selected resource unit. The CW for random access is different from the contention window used to determine the backoff time during carrier sense of CSMA / CA.

In the above method, when a plurality of terminals obtain access rights at the same time, these terminals may select the same STA undesignated RU and transmit a frame. In this case, the access points collide with the frames received from these terminals, and cannot normally decode each frame. Since these terminals do not receive the delivery confirmation response from the access point, it is determined that the frame transmitted by the own terminal has not been normally received. In that case, when the next random access trigger frame is received, these terminals select a random number from the newly set random access CW and perform the same processing. It is not clear whether to reselect. It would be unfair to select a random access CW under the same conditions as a terminal that succeeded in transmission (such as a terminal that did not select the same resource unit as another terminal). Also, it is not clear how to reselect CW for terminals that have received frames normally at the access point. As described above, this method lacks a protocol for repeatedly using the trigger frame for random access.

In particular, when a random access trigger frame is used to collect UL-MU allocation requests (uplink transmission requests) from terminals, the request does not reach the access point at the terminal that failed to transmit, so UL- It will not be selected as a target terminal for MU. On the other hand, the terminal that can normally transmit the UL-MU allocation request can be selected as the target terminal of UL-MU according to the request (the opportunity of transmission in UL-MU can be obtained). Therefore, it is unfair to select a random access CW under the same conditions as a terminal that has succeeded in transmission.

IEEE 802.11-15 / 1105 IEEE Std 802.11ac-2013 IEEE Std 802.11 (TM) -2012

An embodiment of the present invention aims to provide a plurality of wireless communication terminals with a fair transmission opportunity.

The wireless communication terminal as one aspect of the present invention includes at least one antenna, a receiving unit coupled to the antenna and receiving a frame, a transmitting unit coupled to the antenna and transmitting a frame, the receiving unit, and the receiving unit. A communication processing unit coupled to the transmission unit, a network processing unit coupled to the communication processing unit, transmitting data to the communication processing unit, and receiving data from another device, and a network processing unit combined with the network processing unit. It is provided with a memory and a memory for caching the first data. The transmission unit transmits a first frame containing information specifying a plurality of frequency components via the antenna, and the communication processing unit determines whether the second frame is received by each of the plurality of frequency components. The transmitting unit determines and uses the first information regarding the first value range according to the number of the frequency components received by the second frame, which is used for determining whether or not the response to the first frame is possible. The included third frame is transmitted via the antenna, and the first frame or the third frame includes the first data or information based on the first data cached in the memory.

The functional block diagram of the wireless communication apparatus which concerns on embodiment of this invention. Diagram to illustrate the allocation of resource units. The figure for demonstrating the form of a resource unit. The figure which shows the wireless communication group including a base station and a plurality of terminals. The figure which shows the basic format example of a MAC frame. The figure which shows the format example of an information element. The figure which shows the example of the basic operation sequence which concerns on embodiment of this invention. The figure which shows the format example of a physical packet. The figure which shows the format example of the trigger frame (including the case of the trigger frame for random access). The figure which shows the structural example of the RU / AID field. The supplementary explanatory diagram of the operation sequence of FIG. Explanatory drawing of Multi-STA BA frame. The figure which shows the schematic format example of the physical packet used for DL-OFDA transmission. The figure which shows the example of the operation sequence which concerns on embodiment of this invention. The supplementary explanatory diagram of the operation sequence of FIG. The figure which shows the state of the update of CWO (Constitution Window for UL-OFDA) schematically. The figure which shows the operation sequence example when the trigger frame is transmitted instead of the delivery confirmation response frame. The figure which shows typically the operation which concerns on modification 1 of CWO update. The figure which shows typically the operation which concerns on the modification 2 of CWO update. The figure which shows the sequence example of the operation of the base station which concerns on the modification 4 of CWO update. The figure which shows the flowchart of an example of the operation of the terminal which concerns on embodiment of this invention. The figure which shows the flowchart of an example of the operation of the base station which concerns on embodiment of this invention. The functional block diagram of the access point or the terminal which concerns on 2nd Embodiment. The figure which shows the whole configuration example of a terminal or a base station. The figure which shows the hardware configuration example of the wireless communication device mounted on a terminal or a base station. The perspective view of the wireless communication terminal which concerns on embodiment of this invention. The figure which shows the memory card which concerns on embodiment of this invention. The figure which shows an example of frame exchange in a contention period.

Hereinafter, embodiments of the present invention will be described with reference to the drawings. IEEE Std 802.11 (TM) -2012 and IEEE, known as wireless LAN standards
IEEE 802.11ac (TM) -2013 and the IEEE 802.11-15 specification framework document for the next-generation wireless LAN standard, IEEE 802.11ac (Specification Framework Document), dated September 22, 2015. / 0132r9 shall be incorporated herein by reference in its entirety.

(First Embodiment)
FIG. 1 shows a functional block diagram of the wireless communication device according to the first embodiment. This wireless communication device can be mounted on a wireless communication base station (hereinafter, base station or access point) or a wireless communication terminal (hereinafter, terminal) that communicates with the base station. A base station is a form of a wireless communication terminal because it basically has the same communication function as a terminal except that it mainly has a relay function. The operation of the functional block is basically the same for both, but there are some differences between the terminals of the base station and the terminals of the non-base station. In the following description, the term wireless communication terminal or terminal may refer to a base station unless it is necessary to distinguish between the two.

The wireless communication system according to the present embodiment includes a base station and a plurality of terminals on which the wireless communication device of FIG. 1 is mounted. In this system, OFDMA (Orthogonal Frequency Division Multiple Access: Orthogonal Frequency Division Multiple Access) is possible as multi-user communication (multiplex communication). Uplink OFDMA is described as UL-OFDMA. The downlink OFDMA is described as DL-OFDMA. In the system of this embodiment, at least UL-OFDMA can be implemented. Hereinafter, OFDMA will be described.

In OFDMA, a resource unit including one or a plurality of subcarriers is assigned to a terminal, and transmission / reception is performed simultaneously between the base station and a plurality of terminals on a resource unit basis. A resource unit is a frequency component that is the minimum unit of a resource for communication.

FIG. 2 shows resource units (RU # 1, RU # 2, ... RU # K) secured in a continuous frequency domain of one channel (described here as channel M). A plurality of subcarriers orthogonal to each other are arranged in the channel M, and a plurality of resource units including one or a plurality of subcarriers are defined in the channel M. One or more subcarriers (guard subcarriers) may be arranged between resource units, but guard subcarriers are not essential. Identification information for identifying the resource unit or subcarrier may be set in each resource unit or subcarrier in the channel. The bandwidth of one channel is, for example, 20 MHz, 40 MHz, 80 MHz, 160 MHz, and the like, but is not limited thereto. A plurality of 20 MHz channels may be combined into one channel. The number of subcarriers or resource units in the channel may vary depending on the bandwidth. OFDMA communication is realized by using different resource units simultaneously by a plurality of terminals.

The bandwidth (or the number of subcarriers) of the resource unit may be common to each resource unit, or the bandwidth (or the number of subcarriers) may be different for each resource unit. FIG. 3 schematically shows an example of an arrangement pattern of resource units in one channel. The horizontal direction corresponds to the frequency domain direction along the paper surface. FIG. 3A shows an example in which a plurality of resource units (RU # 1, RU # 2, ... RU # K) having the same bandwidth are arranged. FIG. 3B shows an example in which a plurality of resource units (RU # 11-1, RU # 11-2, ..., RU # 11-L) having a bandwidth larger than that of FIG. 3A are arranged. .. FIG. 3C shows an example in which resource units having three or more types of bandwidths are arranged. The resource unit (RU # 12-1, RU # 12-2) has the largest bandwidth, and the resource unit RU # 11- (L-1) has the same bandwidth and resources as the resource unit of FIG. 3 (B). The units (RU # K-1, RU # K) have the same bandwidth as the resource unit of FIG. 3 (A).

As an example, when the entire 20 MHz channel width is used, 26 resource units can be set for 256 subcarriers (tones) arranged within the 20 MHz channel width. That is, nine resource units are set in the 20 MHz channel width, and the bandwidth of the resource unit is smaller than the 2.5 MHz width. In the 40 MHz channel width, as an example, 18 resource units are set. In the 80 MHz channel width, as an example, 37 resource units are set. If this is developed, for example, in a 160 MHz channel width or an 80 + 80 MHz channel width, 74 resource units are set. Of course, the width of the resource unit is not limited to a specific value, and resource units of various sizes can be arranged.

The number of resource units used by each terminal is not limited to a specific value, and one or more resource units may be used. When a terminal uses a plurality of resource units, a plurality of frequency-continuous resource units may be bonded and used as one resource unit, or a plurality of resource units located at distant locations may be allowed to be used. May be good. The resource unit # 11-1 of FIG. 3B may be considered as an example of the resource unit obtained by bonding the resource units # 1 and # 2 of FIG. 3A.

The subcarriers in one resource unit may be continuous in the frequency domain, or the resource unit may be defined from a plurality of subcarriers arranged discontinuously. The channel used in OFDMA is not limited to one, and in addition to channel M, another channel (see channel N in FIG. 2) located at a remote position in the frequency domain may be similarly used as channel M. The resource unit may be secured and the resource unit in both the channel M and the channel N may be used. The method of arranging the resource units may be the same or different between the channel M and the channel N. As an example, the bandwidth of one channel is, but is not limited to, 20 MHz, 40 MHz, 80 MHz, 160 MHz, and the like, as described above. It is also possible to use three or more channels. It is also possible to consider channel M and channel N together as one channel.

The terminal that implements OFDMA is at least a channel with a basic channel width (20 MHz channel width if a terminal compatible with the IEEE802.11a / b / g / n / ac standard is a legacy terminal) in a legacy terminal that is subject to backward compatibility. It is assumed that the physical packet including the frame can be received and decoded (including demodulation and decoding of the error correction code). The carrier sense shall be performed in units of the basic channel width.

Career sense is the physical carrier sense (Physical Carrier) related to busy / idle of CCA (Clear Channel Assistance).
It may include both a Sense) and a virtual carrier sense based on the media reservation time described in the received frame. As in the latter case, the mechanism for virtually determining the medium to be busy, or the period for virtually determining the medium to be busy is called NAV (Network Allocation Vector). The carrier sense information based on CCA or NAV performed for each channel may be applied in common to all resource units in the channel. For example, all resource units belonging to a channel whose carrier sense information indicates an idle may be determined to be idle.

In addition to the resource unit-based OFDMA described above, the OFDMA can also be a channel-based OFDMA. The OFDMA in this case may be particularly referred to as MU-MC (Multi-User Multi-Channel). In MU-MC, access points allocate multiple channels (one channel width is, for example, 20 MHz) to multiple terminals, and the multiple channels are used simultaneously for simultaneous transmission to multiple terminals or simultaneous reception from multiple terminals. conduct. In the OFDMA described below, a resource unit-based OFDMA is assumed, but an embodiment of a channel-based OFDMA can also be realized by performing necessary replacements such as replacing the resource units described below with channels.

In the following description, a terminal having the ability to perform OFDMA may be referred to as an OFDMA compatible terminal or the like. A terminal that does not have this capability may be called a legacy terminal. When the ability to carry out OFDMA communication can be switched between enable and disable, a terminal in which the ability is enabled may be considered as an OFDMA-compatible terminal.

As shown in FIG. 1, the wireless communication devices mounted on the terminals (terminals of non-base stations and base stations) include a higher-level processing unit 90, a MAC processing unit 10, a PHY (Physical) processing unit 50, and a MAC /. It includes a PHY management unit 60, an analog processing unit 70 (analog processing units 1 to N), and an antenna 80 (antennas 1 to N). N is an integer of 1 or more. In the figure, N analog processing units and N antennas are connected in pairs, but the configuration is not necessarily limited to this. For example, the number of analog processing units is one, and two or more antennas may be commonly connected to the analog processing units.

The MAC processing unit 10, the MAC / PHY management unit 60, and the PHY processing unit 50 correspond to a form of a control unit or a baseband integrated circuit that performs processing related to communication with other terminals (including a base station). The analog processing unit 70 corresponds to, for example, a form of a wireless communication unit or an RF (Radio Frequency) integrated circuit that transmits / receives signals via an antenna 80. The integrated circuit for wireless communication according to the present embodiment includes at least the former of the baseband integrated circuit (control unit) and the RF integrated circuit. The function of the baseband integrated circuit may be performed by software (program) operating in a processor such as a CPU, may be performed by hardware, or may be performed by both software and hardware. The software may be stored in a memory such as a ROM or RAM, a storage medium such as a hard disk, or an SSD, read by a processor, and executed. The memory may be a volatile memory such as SRAM or DRAM, or a non-volatile memory such as NAND or MRAM.

The upper processing unit 90 performs processing for the upper layer on the MAC (Medium Access Control) layer. The upper processing unit 90 can exchange signals with the MAC processing unit 10. Typical examples of the upper layer include TCP / IP, UDP / IP, and an application layer on the upper layer, but the present embodiment is not limited to this. The upper processing unit 90 may include a buffer for exchanging data between the MAC layer and the upper layer. It may be connected to the wired infrastructure via the upper processing unit 90. The buffer may be a memory, an SSD, a hard disk, or the like. When the buffer is a memory, the memory may be a volatile memory such as SRAM or DRAM, or a non-volatile memory such as NAND or MRAM.

The MAC processing unit 10 performs processing for the MAC layer. As described above, the MAC processing unit 10 can exchange signals with the higher-level processing unit 90. Further, the MAC processing unit 10 can exchange signals with the PHY processing unit 50. The MAC processing unit 10 includes a MAC common processing unit 20, a transmission processing unit 30, and a reception processing unit 40.

The MAC common processing unit 20 performs processing common to transmission / reception in the MAC layer. The MAC common processing unit 20 is connected to a higher-level processing unit 90, a transmission processing unit 30, a reception processing unit 40, and a MAC / PHY management unit 60, and exchanges signals with each other.

The transmission processing unit 30 and the reception processing unit 40 are connected to each other. Further, the transmission processing unit 30 and the reception processing unit 40 are connected to the MAC common processing unit 20 and the PHY processing unit 50, respectively. The transmission processing unit 30 performs transmission processing on the MAC layer. The reception processing unit 40 performs reception processing on the MAC layer.

The PHY processing unit 50 performs processing for the physical layer (PHY layer). As described above, the PHY processing unit 50 can exchange signals with the MAC processing unit 10. The PHY processing unit 50 is connected to the antenna 80 via the analog processing unit 70.

The MAC / PHY management unit 60 is connected to the higher-level processing unit 90, the MAC processing unit 10 (more specifically, the MAC common processing unit 20), and the PHY processing unit 50, respectively. The MAC / PHY management unit 60 manages the MAC operation and the PHY operation in the wireless communication device.

The analog processing unit 70 includes an analog / digital and digital / analog (AD / DA) converter and an RF (Radio Frequency) circuit, and converts a digital signal from the PHY processing unit 50 into an analog signal having a desired frequency to be an analog signal. The high frequency analog signal transmitted from the 80 and received from the antenna 80 is converted into a digital signal. Here, the AD / DA conversion is performed by the analog processing unit 70, but a configuration in which the PHY processing unit 50 has an AD / DA conversion function is also possible.

The wireless communication device according to the present embodiment includes (integrates) the antenna 80 as a component in one chip, so that the mounting area of the antenna 80 can be kept small. Further, in the wireless communication device according to the present embodiment, as shown in FIG. 1, the transmission processing unit 30 and the reception processing unit 40 share N antennas 80. By sharing the N antennas 80 between the transmission processing unit 30 and the reception processing unit 40, the wireless communication device of FIG. 1 can be miniaturized. Of course, the wireless communication device according to the present embodiment may have a configuration different from that illustrated in FIG.

Upon receiving a signal from the wireless medium, the analog processing unit 70 converts the analog signal received by the antenna 80 into a baseband signal that can be processed by the PHY processing unit 50, and further converts it into a digital signal. The PHY processing unit 50 receives a digital reception signal from the analog processing unit 70 and detects the reception level thereof. The detected reception level is compared with the carrier sense level (threshold value), and if the reception level is equal to or higher than the carrier sense level, the PHY processing unit 50 indicates that the medium (CCA: Clear Channel Assessment) is busy. Is output to the MAC processing unit 10 (more accurately, the reception processing unit 40). If the reception level is less than the carrier sense level, the PHY processing unit 50 outputs a signal indicating that the medium (CCA) is idle to the MAC processing unit 10 (more accurately, the reception processing unit 40). ..

The PHY processing unit 50 extracts the payload by performing decoding (including demodulation, decoding of the error correction code, etc.) processing, processing for removing the physical header (PHY header) including the preamble, and the like on the received signal. According to the 802.11 standard, this payload is used on the PHY side as a PSDU (physical layer control procedure).
(PLCP) service data unit) is called. The PHY processing unit 50 passes the extracted payload to the reception processing unit 40, and the reception processing unit 40 treats this as a MAC frame. In the 802.11 standard, this MAC frame is referred to as MPDU (medium access protocol (MAC) protocol data).
It is called unit). In addition, the PHY processing unit 50 notifies the reception processing unit 40 when the reception signal is started, and notifies the reception processing unit 40 when the reception signal is received. Further, when the received signal can be normally decoded as a physical packet (PHY packet) (if no error is detected), the PHY processing unit 50 notifies the end of reception of the received signal and the medium is idle. The signal indicating the above is passed to the reception processing unit 40. When the PHY processing unit 50 detects an error in the received signal, the PHY processing unit 50 notifies the receiving processing unit 40 that the error has been detected with an appropriate error code corresponding to the error type. Further, when the PHY processing unit 50 determines that the medium has become idle, the PHY processing unit 50 notifies the reception processing unit 40 of a signal indicating that the medium is idle.

The MAC common processing unit 20 mediates the transfer of transmission data from the higher-level processing unit 90 to the transmission processing unit 30 and the transfer of received data from the reception processing unit 40 to the higher-level processing unit 90, respectively. In the 802.11 standard, the data in this MAC data frame is called MSDU (medium access control (MAC) service data unit). Further, the MAC common processing unit 20 once receives an instruction from the MAC / PHY management unit 60, converts the instruction into a transmission processing unit 30 and a reception processing unit 40, respectively, and outputs the instruction.

The MAC / PHY management unit 60 corresponds to, for example, SME (Station Management Entry) in the IEEE802.11 standard. In that case, the interface between the MAC / PHY management unit 60 and the MAC common processing unit 20 is the MLME SAP (MAC subLayer Management) in the 802.11 standard.
The interface between the MAC / PHY management unit 60 and the PHY processing unit 50 corresponds to the Entry Service Access Point), and the interface between the MAC / PHY management unit 60 and the PHY processing unit 50 is a PLME SAP (Physical Layer Management Element) in the IEEE802.11 wireless LAN (Local Area Network). Equivalent to.

In FIG. 1, the MAC / PHY management unit 60 is drawn as if the functional unit for MAC management and the functional unit for PHY management are integrated, but even if they are implemented separately. good.

The MAC / PHY management unit 60 holds a management information base (MIB). The MIB holds various information such as the ability of the own terminal and whether various functions are valid or invalid. For example, information on whether or not the own terminal supports OFDMA and whether or not the function of the ability to execute OFDMA when the terminal supports OFDMA may be held. The memory for holding and managing the MIB may be included in the MAC / PHY management unit 60, or may be separately provided without being included in the MAC / PHY management unit 60. When the memory for holding and managing the MIB is provided separately from the MAC / PHY management unit 60, the MAC / PHY management unit 60 can refer to the other memory and rewrite the rewritable parameters in the memory. It can be performed. The memory may be a volatile memory such as SRAM or DRAM, or a non-volatile memory such as NAND or MRAM. Further, instead of the memory, a storage device such as an SSD or a hard disk may be used. In a base station, such information of another terminal as a non-base station can also be acquired by notification from the terminal. In that case, the MAC / PHY management unit 60 can refer to and rewrite information about other terminals. Alternatively, the memory for storing information about these other terminals may be held and managed separately from the MIB. In that case, the MAC / PHY management unit 60 or the MAC common processing unit 20 can refer to and rewrite the other memory. Further, the MAC / PHY management unit 60 of the base station is a resource unit for OFDMA based on various information about the terminal as a non-base station or a request from the terminal in carrying out OFDMA (UL-OFDA or DL-OFDA). It may also have a selection function for selecting terminals to be assigned at the same time. Further, the MAC / PHY management unit 60 or the MAC processing unit 10 may manage the transmission rate applied to the MAC frame and the physical header to be transmitted. Further, the MAC / PHY management unit 60 of the base station may define and manage a support rate set which is a rate set supported by the base station. The support rate set may include rates that terminals connecting to the base station must support and optional rates.

The MAC processing unit 10 handles three types of MAC frames, a data frame, a control frame, and a management frame, and performs various processes defined in the MAC layer. Here, three types of MAC frames will be described.

The management frame is used for managing communication links with other terminals. As a management frame, for example, there is a beacon frame for notifying the attributes and synchronization information of the group in order to form a wireless communication group which is a Basic Service Set (BSS) in the 802.11 standard. There are also frames that are exchanged for authentication or for establishing communication links. Here, it is expressed that a communication link has been established in a state in which one terminal has exchanged information necessary for carrying out wireless communication with another terminal. Necessary information exchange includes, for example, notification of functions supported by the own terminal (for example, support for the OFDMA method, various abilities, etc.), negotiation regarding method setting, and the like. The management frame is generated by the transmission processing unit 30 based on an instruction received from the MAC / PHY management unit 60 via the MAC common processing unit 20.

In relation to the management frame, the transmission processing unit 30 has a notification means for notifying other terminals of various information via the management frame. for example. The notification means of the terminal as a non-base station is to send information as to whether it is compatible with an OFDMA compatible terminal, an IEEE802.11n compatible terminal, or an IEEE802.11ac compatible terminal in a management frame to the base station. You may notify the type of your terminal. As this management frame, for example, the association used in the association process, which is one of the procedures for the terminal to authenticate with the base station.
There are Request frames, or Response Request frames used in the rear association process. The notification means of the base station may notify the terminal of the non-base station of the information on whether or not the OFDMA communication is supported via the management frame. Examples of the management frame used for this include a Beacon frame and a Probe Response frame which is a response to a Probe Request frame transmitted by a non-base station terminal. The base station may have a function of grouping a group of terminals connected to its own device. The above-mentioned notification means of the base station may notify the group ID, which is the group identifier of the group to which each terminal belongs, via the management frame. As this management frame, for example, there is a Group ID Management frame.
The group ID is, for example, the group ID (6 bits) specified for downlink MU-MIMO (Multi-User Multi-Input Multi-Optut) (DL-MU-MIMO) in IEEE Std 802.11ac-2013. It may be extended so as to include the case of, or it may be a group ID defined by another method.

Here, the association ID (AID) will be described. The AID is an association process for connecting a terminal to a base station and allowing BSS under the base station to exchange data frames, and is an identifier (terminal identifier) of the terminal assigned by the base station. Specifically, the association process sends an Association Request frame from the terminal to the base station, sends an Association Response frame from the base station to the terminal, and the Terminal Status Code field in the Association Response frame is "0", that is, access. Is a successful process. Both the Association Request frame and the Association Response frame contain the communication capability (Capacity) of the transmitting terminal, so that both parties who receive the message grasp the communication capability of the other party. When the terminal Status Code field in the Association Response frame is "0", that is, access, the AID is extracted from the AID field (16 bits) in the same frame and used as the AID of the destination terminal. That is, at this point, the AID is assigned from the base station to the terminal, and the AID is valid for the terminal. In a state where the base station is associated with the terminal, the AID of the terminal is valid. On the other hand, when the base station transmits a Dissociation frame to the terminal and the terminal receives it, or when the terminal transmits a Dissociation frame to the base station, the AID of the terminal becomes invalid (null). Naturally, AID is invalid even for terminals that have not undergone the association process with any base station. The state in which the AID is invalid can also be said to be the state in which the AID is not specified.

The reception processing unit 40 has a receiving means for receiving various information from another terminal via a management frame. As an example, the receiving means of the base station may receive information on whether or not OFDMA is supported from the terminal as a non-base station. Further, when the terminal as the non-base station is a legacy terminal (IEEE802.11a / b / g / n / ac standard compatible terminal, etc.), information on the compatible channel width (maximum available channel width) can be obtained. You may receive it. The receiving means of the terminal may receive information on whether or not OFDMA is supported from the base station.

The example of information transmitted / received via the management frame described above is only an example, and various other information can be transmitted / received between terminals (including base stations) via the management frame. For example, an OFDMA-enabled terminal may use a resource unit, or channel, or both of which it desires to use in UL-OFDM transmission, as a carrier-sense, non-interfering channel, or non-interfering resource unit, or these. You may choose from both. The base station may then be informed of information about the selected resource unit and / or channel. In this case, the base station may allocate resource units for UL-OFDA communication to each OFDMA-compatible terminal based on the information. The channels used in OFDMA communication may be all channels that can be used as a wireless communication system, or may be some (one or a plurality) channels.

The data frame is used to transmit data to the other terminal in a state where a communication link is established with the other terminal. For example, a user's application operation generates data in the terminal, and the data is carried by a data frame. Specifically, the generated data is passed from the upper processing unit 90 to the transmission processing unit 30 via the MAC common processing unit 20, and the transmission processing unit 30 puts the data in the frame body field and puts the data in the frame body field. A data frame is generated by adding a MAC header. Then, the PHY processing unit 50 adds a physical header to the data frame to generate a physical packet, and the physical packet is transmitted via the analog processing unit 70 and the antenna 80. When the PHY processing unit 50 receives a physical packet, the physical layer is processed based on the physical header to extract a MAC frame (here, a data frame), and the data frame is passed to the reception processing unit 40. When the reception processing unit 40 receives a data frame (when it grasps that the received MAC frame is a data frame), the reception processing unit 40 extracts the information of the frame body field as data, and the extracted data is passed through the MAC common processing unit 20. And pass it to the upper processing unit 90. As a result, operations on the application such as writing and playing data occur.

The control frame is used for control when transmitting / receiving (exchanged) a management frame and a data frame with another wireless communication device. The control frame includes, for example, an RTS (Request to Send) frame and a CTS (Clear to) that are exchanged with another wireless communication device to reserve a wireless medium before starting the exchange of the management frame and the data frame. Send) There is a frame and so on. Further, as another control frame, there is a delivery confirmation response frame for confirming the delivery of the received management frame and data frame. Examples of the delivery acknowledgment frame include an ACK (Acknowledgement) frame and a BA (BlockACK) frame. Since the CTS frame is also transmitted as a response of the RTS frame, it can be said that it is a frame representing a delivery confirmation response. The CF-End frame is also one of the control frames. The CF-End frame is a frame that announces the end of CFP (Contention Free Period), that is, a frame that permits access to a wireless medium. These control frames are generated by the transmission processing unit 30. Regarding the control frame (CTS frame, ACK frame, BA frame, etc.) transmitted as a response to the received MAC frame, the reception processing unit 40 determines the necessity of transmitting the response frame (control frame) and generates the frame. Necessary information (control frame type, information to be set in RA (Receiver Address) field, etc.) is sent to the transmission processing unit 30 together with the transmission instruction. The transmission processing unit 30 generates an appropriate control frame based on the information necessary for the frame generation and the transmission instruction.

When the MAC processing unit 10 transmits a MAC frame based on CSMA / CA (Carrier Sense Multiple Access with Carrier Assistance), it is necessary to acquire an access right (transmission right) on the wireless medium. The transmission processing unit 30 measures the transmission timing based on the carrier sense information from the reception processing unit 40. The transmission processing unit 30 gives a transmission instruction to the PHY processing unit 50 according to the transmission timing, and further passes a MAC frame. In addition to the transmission instruction, the transmission processing unit 30 may instruct the modulation method and the coding method used for the transmission together. In addition to these, the transmission processing unit 30 may instruct the transmission power. When the MAC processing unit 10 obtains a time (Transmission Operation; TXOP) that can occupy the medium after acquiring the access right (transmission right), the MAC processing unit 10 is accompanied by restrictions such as a QoS (Quality of Service) attribute, but other wireless communication. MAC frames can be continuously exchanged with the device. TXOP is acquired, for example, when the wireless communication device transmits a predetermined frame (for example, RTS frame) based on CSMA / CA and correctly receives a response frame (for example, CTS frame) from another wireless communication device. When this predetermined frame is received by the other wireless communication device, the other wireless communication device transmits the response frame after the minimum frame interval (Short InterFrame Space; SIFS). Further, as a method of acquiring TXOP without using an RTS frame, for example, a data frame requesting transmission of a delivery acknowledgment frame by direct unicast (a frame having a shape in which frames are connected as described later, or a frame in which a payload is connected is connected). It may be a frame of a shaped shape) or a management frame may be transmitted and a delivery acknowledgment frame (ACK frame or BlockACK frame) for the management frame may be correctly received. Alternatively, if a frame that does not require another wireless communication device to transmit the delivery confirmation response frame and the duration / ID field of the frame is set to a period longer than the time required to transmit the frame is transmitted. , It may be interpreted that the TXOP for the period described in the Duration / ID field has been acquired from the stage when the frame is transmitted.

The reception processing unit 40 manages the carrier sense information described above. This carrier sense information is based on the physical carrier sense information regarding the busy / idle of the medium (CCA) input from the PHY processing unit 50 and the medium reservation time described in the reception frame. Includes both virtual carrier sense information. If either carrier sense information is busy, the medium is considered busy and transmission is prohibited during that time. In the 802.11 standard, the media reservation time is described in the Duration / ID field in the MAC header. When the MAC processing unit 10 receives a MAC frame addressed to another wireless communication device (not addressed to itself), the medium is virtually busy from the end of the physical packet containing the MAC frame to the media reservation time. Judge that there is. Such a mechanism for virtually determining the medium to be busy, or a period for virtually determining the medium to be busy is called NAV (Network Allocation Vector). It can be said that the media reservation time represents the length of the period for instructing the suppression of access to the wireless medium, that is, the length of the period for postponing the access to the wireless medium.

Here, the data frame may be configured to concatenate a plurality of MAC frames or payload portions of a plurality of MAC frames. The former is called A (Aggregated) -MPDU in the 802.11 standard, and the latter is called A (Aggregated) -MSDU (MAC service data unit). In the case of A-MPDU, a plurality of MPDUs are concatenated in the PSDU. In addition to data frames, management frames and control frames are also subject to concatenation. In the case of A-MSDU, MSDUs, which are a plurality of data payloads, are concatenated in the frame body of one MPDU. In both A-MPDU and A-MSDU, delimiter information (length information, etc.) is stored in a data frame so that the concatenation of multiple MPDUs and the concatenation of multiple MSDUs can be appropriately separated by the receiving terminal. Has been done. Both A-MPDU and A-MSDU may be used in combination. Further, the A-MPDU may target only one MAC frame instead of a plurality of MAC frames, and in this case as well, the delimiter information is stored in the data frame. When an A-MPDU or the like is received, the responses to a plurality of connected MAC frames are collectively transmitted. In the response in this case, a BA (BlockACK) frame is used instead of the ACK frame. In the following description and figures, the notation of MPDU may be used, but this also includes the case of A-MPDU or A-MSDU described above.

In the 802.11 standard, non-base station terminals join the BSS (this is called the Infrastructure BSS), which is mainly composed of base stations, so that data frames can be exchanged within the BSS. A plurality of procedures are defined step by step. For example, there is a procedure called association, and a terminal of a non-base station transmits an association request frame to a base station for which the terminal requests a connection. The base station transmits an ACK frame for the association request frame, and then transmits an association response frame, which is a response to the association request frame.

The terminal stores the capacity of its own terminal in the association request frame, and can notify the base station of the capacity of its own terminal by transmitting it. For example, the terminal may send information for identifying a channel or a resource unit that the terminal can support, or both of them, and a standard that the terminal supports in the association request frame. This information may also be set in a frame transmitted by a procedure called reassociation for reconnecting to another base station.
In this reassociation procedure, the terminal transmits a reassociation request frame to another base station requesting reconnection. The other base station transmits an ACK frame for the reassociation request frame, and then transmits a reassociation response frame, which is a response to the reassociation request frame.

As the management frame, a beacon frame, a probe response frame, or the like may be used in addition to the association request frame and the reassociation request frame. The beacon frame is basically transmitted by the base station, and can store parameters indicating the attributes of the BSS as well as parameters notifying the ability of the base station itself. Therefore, information on whether or not the base station can support OFDMA may be added as a parameter for notifying the capability of the base station itself. Further, as another parameter, information on the supported rate of the base station may be notified. The support rate may include a rate that the terminal participating in the BSS formed by the base station must support and an optional rate. The probe response frame is a frame that receives a probe request frame from a terminal that transmits a beacon frame and transmits it in response to the probe request frame. Since the probe response frame basically notifies the same content as the beacon frame, the base station notifies the terminal that transmitted the probe request frame of its own capability even if the probe response frame is used. be able to. By notifying the OFDMA-compatible terminal, the terminal may perform an operation such as enabling the OFDMA communication function of the own terminal, for example.

In addition, the terminal may notify the information of the rate that the own terminal can execute among the support rates of the base station as the information for notifying the base station about the ability of the own terminal. However, for the required rate among the support rates, the terminal connected to the base station shall have the ability to execute the required rate.

If some of the information handled above determines the content of another information by notifying one information, the notification can be omitted. For example, consider the case where an ability to comply with a new standard or specification is defined, and if it is compatible with it, the terminal is naturally OFDMA compatible. In this case, it is not necessary to explicitly notify the existence of the ability to correspond to the standard or the specification as the above-mentioned information, and explicitly notify that the terminal is an OFDMA-compatible terminal as the above-mentioned other information.

FIG. 4 shows a wireless communication system according to the present embodiment. This system includes a base station (AP: Access Point) 100 and a plurality of terminals (STA: STAtion) 1 to 8. BSS (Basic Service Set) 1 is formed by the base station 100 and the terminals 1 to 8 under the control. This system is a wireless LAN system conforming to the IEEE802.11 standard using CSMA / CA (Carrier Sense Multiple Access with Carrier Assistance). In addition, a legacy terminal (IEEE802.11a / b / g / n / ac standard compatible terminal, etc.) other than the terminal (OFDMA compatible terminal) according to the present embodiment may exist in BSS1.

FIG. 5A shows an example of a basic format of a MAC frame. The data frame, management frame, and control frame according to the present embodiment are based on such a frame format. The frame format includes MAC header, Frame body and FCS fields. As shown in FIG. 5B, the MAC header includes fields of Frame Control, Duration / ID, Addless1, Addless2, Addless3, Quality Control, QoS Control, and HT (High Throughput) control.

Not all of these fields need to be present, and some fields may not be present. For example, the Addless3 field may not exist. Also, the QoS Control and HT Control fields may or may not be present. It is also possible that the frame body field does not exist. There may also be other fields not shown in FIG. For example, there may be more Address4 fields. In the case of the trigger frame described later, the common information field and the terminal information field may exist in the frame body field or the MAC header.

The reception address (Receiver Address; RA) is entered in the field of Addlesss1, the source address (Transmitter Address; TA) is entered in the field of Address2, and the field of Addlesss3 is an identifier of BSS depending on the use of the frame. BSSID (Basic Service Set Identifier) or TA is entered. The BSSID may be a wildcard BSSID (all bits are 1) that targets all BSSIDs.

The Frame Control field includes two fields such as a type (Type) and a subtype (Subtype). The data frame, the management frame, and the control frame are roughly classified in the Type field, and the subtypes in the roughly classified frames are performed in the Subtype field. For example, the control frame includes a BA (Block Ac) frame, a BAR (Block Ac Request) frame, an RTS (Request to Send) frame, and a CTS (Clear to Send) frame, and the identification of these frames is Subtype. It is done in the field. Trigger frames, which will be described later, may also be distinguished by a combination of types and subtypes. As an example, trigger frames are classified as control frames (type "control").

The Duration / ID field describes the media reservation time, and when a MAC frame addressed to another terminal is received, the medium is virtually busy from the end of the physical packet containing the MAC frame to the media reservation time. Is determined. Such a mechanism for virtually determining the medium to be busy, or a period for virtually determining the medium to be busy is called NAV (Network Allocation Vector), as described above. The QoS field is used to perform QoS control for transmission in consideration of the priority of the frame. The HT Control field is a field introduced in IEEE802.11n.

In the management frame, the information element (Information element; IE) to which a unique Identifier ID (Identifier) is assigned is framed.
Set in the Body field. The frame body field can be set to one or more information elements after the unique field depending on the type of management frame. As shown in FIG. 6, the information element has each field of an Element ID field, a Length field, and an information field. Information elements are identified by an Element ID. The information field stores the content of the information to be notified, and the Length field stores the length information of the information field.

FCS (Frame Check Sequence) information is set in the FCS field as a checksum code used for frame error detection on the receiving side. As an example of FCS information, there is CRC (Cyclic Redundancy Code) and the like.

FIG. 7 shows an example of an operation sequence between a base station (AP) 101 according to the present embodiment and a plurality of terminals including terminals (STA) 1 to terminal (STA) 8. Terminals 1 to 8 are OFDMA compatible terminals. FIG. 7 shows a basic operation sequence according to the present embodiment, and the operation according to the feature of the present embodiment will be described later in another operation sequence example (see FIG. 14).

In this system, as a premise, communication (single user communication) is individually performed between the base station and a part or all of the terminals 1 to 8 on a CSMA / CA basis. In single-user communication, for example, communication is performed between a base station and a terminal on one channel having a basic channel width (for example, 20 MHz). As an example of single-user communication, when the terminal holds data for uplink transmission, the access right to the wireless medium is acquired according to CSMA / CA. Therefore, the terminal performs carrier sense during the carrier sense time (standby time) between DIFS / AIFS [AC] and the randomly determined backoff time, and when the medium (CCA) is determined to be idle, for example. Acquire the access right to send one frame. The terminal transmits a data frame containing the data to be transmitted (more specifically, a physical packet containing the data frame), and when the base station normally receives this data frame, the delivery is confirmed after SIFS time from the completion of receiving the data frame. It returns an ACK frame (more specifically, a physical packet containing the ACK frame) which is a response frame. By receiving the ACK frame, the terminal determines that the data frame transmission was successful. The data frame transmitted to the base station may be an aggregation frame (A-MPDU or the like), and the delivery confirmation response frame to which the base station responds may be a BA frame (the same applies hereinafter). The DIFS / AIFS [AC] time means the time of either DIFS or AIFS [AC]. When not compatible with QoS, it refers to the FIDS time, and when it is compatible with QoS, it refers to the AIFS [AC] time determined according to the access category (AC: Access Category) (described later) of the data to be transmitted. As shown in FIG. 8 to be described later, the basic configuration of the physical packet is a MAC frame stored in a data field with a physical header added.

The base station determines the start of UL-OFDMA at an arbitrary timing. In this example, it is assumed that UL-OFDMA transmission is performed on the same channel as single-user communication (one channel with a basic channel width of 20 MHz). That is, it is assumed that UL-OFDMA transmission is performed using a plurality of resource units defined in a channel having a basic channel width of 20 MHz. However, UL-OFDMA transmission can be performed with other channel widths such as 40 MHz and 80 MHz.

When the base station decides to start UL-OFDMA, it transmits a UL-OFDMA trigger frame, more particularly a random access trigger frame (more specifically, a physical packet containing a random access trigger frame) 501.

The random access trigger frame 501 allows the use of any terminal or multiple terminals for all or at least a portion of the plurality of resource units available in UL-OFDMA. No specific terminal is assigned to the resource unit (the terminal to be used is not limited to a specific terminal). Such a resource unit (RU) may be referred to as "STA undesignated RU". A specific terminal may be assigned to a resource unit other than the STA undesignated RU, and in that case, only the specific terminal uses the resource unit. That is, the STA undesignated RU is a resource unit that allows terminals to randomly select and use (uplink transmission). A trigger frame including the designation of STA undesignated RU for at least some resource units is called a random access trigger frame. The trigger frame for random access is expressed as "TF-R" in the figure.

Before transmitting the random access trigger frame 501, it is assumed that the base station has acquired the access right according to CSMA / CA. The random access trigger frame 501 is transmitted on a channel having a basic channel width of the same channel as the single user communication. A physical packet including a random access trigger frame has a physical header added to the beginning of the random access trigger frame. As an example, as shown in FIG. 8, the physical header includes L-STF (Legacy-Short Training Field), L-LTF (Legacy-Long Training Field), and L-SIG (Legacy Signal) defined in the 802.11 standard. Field), including. L-STF, L-LTF, and L-SIG are fields (legacy fields) that can be recognized by terminals of legacy standards such as IEEE802.11a, and are signal detection, frequency correction (propagation path estimation), and transmission speed, respectively. Information such as is stored.
Fields other than those described here (for example, fields that cannot be recognized by legacy standard terminals and can be recognized by OFDMA compatible terminals) may be included. The random access trigger frame 501 may be a frame that can be received and decoded by a legacy terminal as well as an OFDMA compatible terminal.

FIG. 9 shows an example of the format of the trigger frame (including the case of the trigger frame for random access). It is based on the general MAC frame format shown in FIG. 5, and has a Frame Control field, a Duration / ID field, an Addless1 field, an Addless2 field, a common information field (Common Info.) Field, and a plurality of terminal information (STA Info.). .) Includes fields and FCS fields. Specify that it is a trigger frame in Type and Subtype of the Frame Control field. Type is "control" as an example, and Subtype may define a new value corresponding to the trigger frame. However, a trigger frame in which Type is "managed" or "data" may be defined. Instead of defining a new value as Subtype, a field for notifying that it is a trigger frame may be expressed by using a reserved field in the MAC header. A broadcast address or a multicast address may be set as RA in the Address1 field. The MAC address (BSSID) of the base station may be set as TA in the Addlesss2 field. However, there may be cases where the Adress1 field, the Adress2 field, or both are omitted. In the common information field, information to be notified to a plurality of terminals in common is set. For example, information that specifies the format of the terminal information field, information that specifies the packet length to be transmitted in the response, information that indicates the purpose of the trigger frame, and information that specifies the type of the frame to be transmitted in the response may be set. Further, information on the number of terminal information fields may be set. In the plurality of terminal information fields, information to be individually notified to a plurality of terminals is set. A detailed configuration example of the terminal information fields 1 to n is shown in FIG. The terminal information fields 1 to n include a RU field and an AID field, respectively.

As an example, the terminal information fields 1 to n include a pair (pair) of a RU field (RU_1 to RU_n) and an AID field (AID_1 to AID_n), respectively. Set the identifier of the available resource unit in the RU field. In the AID field, the identifier (AID) of the terminal to which the resource unit is assigned is set, or the information indicating that the use is not specified for a specific terminal is set. In the present embodiment, the information that the use is not specified for a specific terminal is expressed by "X" which is an unused AID value. X is a value of AID that is not assigned to any terminal, and is a value defined in advance by the system or standard, or a value arbitrarily determined by the base station. The value of X may be notified in advance from the base station to each terminal by a management frame such as a beacon frame. The resource unit in which "X" is set is a resource unit that can be used by any terminal, that is, a resource unit for random access.

In addition, the terminal for which the identifier of the own terminal is set in any of the AID fields may or may not be permitted to use the resource unit for random access in addition to the resource unit specified to be used. It does not have to be. In the present embodiment, the terminal describes a mode in which the resource unit for random access is not used when the resource unit specified to be used exists, but the terminal is not limited to this.

It is also possible to limit the use of the resource unit for random access to a specific terminal group or a group having a specific group ID. In the latter case, a group ID may be set in the AID field. In the former case, a plurality of AIDs may be set in association with the RU field. A method other than that described here may be used.

Note that n (the number of pairs of RU field and AID field) may be fixed or variable. In the case of variable, the value of n may be set in the common information field, or a field for notifying the end of the RU / AID field may be provided. The field that notifies the end may be a field in which a special value that is not included in the combination of the resource unit identifier and the AID is set. The terminal information field may include fields other than the RU field and the AID field. For example, there may be a field for setting information that specifies the transmission power used by the terminal, MCS, and the like.

The following shows an example in which a plurality of terminals are randomly selected as a resource unit to perform frame transmission by using a frame format having such a RU / AID field configuration.

The random access trigger frame (TF-R) 501 transmitted from the base station is received by the terminals 1 to 8. In this example, in the random access trigger frame 501, four resource units (RU # 1, RU # 2, RU # 3, RU # 4) are specified, and "X" is set as the AID for each resource unit. Suppose you are. That is, RU # 1 to RU # 4 are STA undesignated RUs. However, more resource units may be specified in the random access trigger frame 501, or the AID of a specific terminal may be specified for some resource units.

On the terminals 1 to 8 side, the random access trigger frame 501 may be decoded, and the use of the own terminal may be specified among the four resource units of RU # 1, RU # 2, RU # 3, and RU # 4. Since AID "X" is set for any resource unit here, it is determined that all resource units are resource units for random access (STA unspecified RU). .. This determination is made by the MAC processing unit 10 (for example, the reception processing unit 30 or the MAC common processing unit 20) or the MAC / PHY management unit 60.

Terminals 1 to 8 hold a backoff value (UL-OFDMA Backoff (OBO) Count) randomly selected from the range below the content window for UL-OFDMA (CWO) value for UL-OFDMA. There is. More specifically, it holds a backoff value selected from a value range of 0 or more and CWO value or less. CWO corresponds to information about the value range. In this example, the magnitude of the value range is CWO-0 = CWO. However, the lower limit of the value range does not have to be 0. Here, the minimum value of CWO is described as CWOmin, and the maximum value of CWO is described as CWOmax. CWO is selected from the range of CWOmin or more and CWOmax or less. Here, it is assumed that "31" is selected as the CWO of the predetermined initial value. The CWO, backoff value (OBO value), CWOmin, and CWOmax may be managed by the MAC processing unit 10 or the MAC / PHY management unit 60 or the like, and the memory accessible from the MAC processing unit 10 or the MAC / PHY management unit 60 or the like. These values may be stored in.

The terminals 1 to 8 update the OBO by subtracting the number of STA unspecified RUs specified in the random access trigger frame 501 from the backoff value of the own terminal. When the updated OBO reaches a predetermined value, it is considered that there is a selection right, and the STA undesignated RU is selected. As a result, the access right to the selected STA undesignated RU is acquired. In this embodiment, the predetermined value is assumed to be 0. If the result of the subtraction is less than 0, the updated OBO is rounded up to 0. In this way, when the updated OBO value reaches 0, the selection right is acquired. In other words, when a random access trigger frame is received, 1 is subtracted from the OBO value (OBO value -1), and that value is the value obtained by subtracting 1 from the STA unspecified RU number of the random access trigger frame (OBO value -1). If the number of STA undesignated RUs is -1) or less, the option is acquired. In other words, if the OBO value (OBO value before subtraction) when the random access trigger frame is received is equal to or less than the number of STA unspecified RUs of the random access trigger frame, the selection right is acquired. The MAC processing unit 10 (for example, the MAC common processing unit 20 or the reception processing unit 40, etc.) or the MAC / PHY management unit 60 makes a determination to update the OBO and acquire the selection right.

Here, it is assumed that all the terminals 1 to 8 have an uplink transmission request. The terminal having the transmission request holds the backoff value selected from the range below the CWO value as described above. The first selection of the backoff value may be performed at the time when the transmission request is generated before the random access trigger frame 501 is received, or may be performed with the reception of the random access trigger frame 501 as a trigger. When another random access trigger frame is received before the random access trigger frame 501 is received, the subtracted OBO value at that time is used when the random access trigger frame 501 is received this time. It may be used as it is as an OBO value (OBO value before subtraction).

FIG. 11 is a supplementary diagram for explaining the sequence of FIG. 7, and corresponds to time in the horizontal direction and frequency in the vertical direction along the paper. The OBO values of terminals 1 to 8 (STA 1 to 8) are STA 1 OBO = 10 respectively.
STA 2 OBO = 3
STA 3 OBO = 5
STA 4 OBO = 4
STA 5 OBO = 1
STA 6 OBO = 8
STA 7 OBO = 8
STA 8 OBO = 10
In the random access trigger frame 501, the number of STA unspecified RUs is 4, so 4 is subtracted from each, and the updated (subtracted) OBO value is as follows. Values smaller than 0 are fixed at 0.
STA 1 OBO = 10-4 = 6
STA 2 OBO = 3-4 = -1 (→ 0)
STA 3 OBO = 5-4 = 1
STA 4 OBO = 4-4 = 0
STA 5 OBO = 1-4 = -3 (→ 0)
STA 6 OBO = 8-4 = 4
STA 7 OBO = 8-4 = 4
STA 8 OBO = 10-4 = 6

Since the updated OBO value reaches the predetermined value (= 0) in the terminals 2, 4, and 5, the terminals 2, 4, and 5 acquire the selection right. Terminals 2, 4, and 5 randomly select resource units from RU # 1 to RU # 4, which are STA undesignated RUs designated by the random access trigger frame 501. Here, it is assumed that RU # 4 is selected for the terminal 2, RU # 3 is selected for the terminal 4, and RU # 1 is selected for the terminal 5. It is assumed that one resource unit is selected, but two or more resource units may be allowed to be selected. Terminals other than terminals 2, 4, and 5 cannot acquire the selection right because the updated OBO value is larger than 0, and wait for the next random access trigger frame to be transmitted. The resource unit selection process may be performed by the MAC processing unit 10 (for example, the MAC common processing unit 20, the reception processing unit 40, the transmission processing unit 30, etc.) or the MAC / PHY management unit 60.

Terminals 2, 4, and 5 use RU # 4, RU # 3, and RU # 1, respectively, after a predetermined time (referred to as T1) from the completion of reception of the random access trigger frame 501, to use frames 512, 514, and 515, respectively. To send. The frame to be transmitted may be a predetermined type or a frame arbitrarily determined by each terminal. As an example of a predetermined type of frame, a UL-OFDMA allocation request frame (a frame for notifying that there is a request for receiving a resource unit allocation for the own terminal and transmitting data in a trigger frame) may be used. In this case, by using a fixed-length frame, the frame length transmitted by each terminal (more specifically, the packet length of the physical packet including the frame) can be unified. Further, parameter information such as packet length and MCS for each terminal is specified in the terminal information field or common information field of the random access trigger frame 501, and the terminal generates a frame according to the parameter information and the frame (more detailed). May send a physical packet containing a frame). If the packet length is less than the specified value, padding data may be added to adjust the packet length. Since RU # 2 was not selected for any terminal, transmission is not performed in RU # 2. If a resource unit other than RU # 1 to RU # 4 exists and the resource unit is designated as another terminal by the trigger frame 501 for random access, the terminal is framed by the specified resource unit. May be sent. In this case, the terminal and the terminals 2, 4, and 5 simultaneously perform uplink transmission (UL-OFDMA transmission). The frame transmitted by the terminals 2, 4, and 5 may be an aggregation frame (A-MPDU) in which a plurality of data frames and the like are aggregated.

As the time T1, a predefined IFS time [μs] can be used as an example. The predefined IFS time may be the SIFS time (= 16 μs), which is the time interval between frames specified in the MAC protocol specification of the 802.11 wireless LAN, or may be a larger time or a smaller time. The value of time T1 may be stored in the common information field of the trigger frame, the MAC header, or the like, and this value may be read and used by the terminal. In addition, the time T1 may be notified in advance by another method such as a beacon frame or another management frame.

The base station receives and decodes frames 515, 514, and 512 transmitted from terminals 5, 4, and 2 at RU # 1, RU # 3, and RU # 4, and performs FCS inspection (CRC inspection, etc.) on the decoded frames. By doing so, it is determined whether the frame has been successfully received. The base station generates and transmits (downlink response) the delivery confirmation response frame 502 according to the inspection result (successful reception) of each frame. Here, a single delivery confirmation response frame 502 representing all delivery confirmations of terminals 2, 4, and 5 is transmitted. The format of such a delivery acknowledgment frame may be newly defined, or a Multi-STA BA frame diverted from a BA (Block Ac) frame may be used. Here, it is assumed that the Multi-STA BA frame is transmitted.

Here, the Multi-STA BA frame will be described. The Multi-STA BA frame is a diverted Block Acck frame (BA frame) for confirming delivery to a plurality of terminals in one frame. The frame type may be Control, and the frame subtype may be BlockAck, as in the case of a normal BA frame. FIG. 12A shows a format example of the Multi-STA BA frame. FIG. 12B shows an example of the format of the BA Control field in the BA frame, and FIG. 12C shows an example of the format of the BA Information field in the BA frame. When reusing a BA frame, the BA is an extended BA frame format for notifying delivery acknowledgments for multiple terminals.
It may be shown in the Control field. For example, in the 802.11 standard, when the Multi-TID subfield is 1 and the Compressed Bitmap subfield is 0, the status is reserved. This may be used to indicate that it is an extended BA frame format for notifying delivery acknowledgments for multiple terminals. Alternatively, in FIG. 12B, the area of bits B3-B8 is a reserved subfield, but a part or all of this area is in an extended BA frame format for notifying a delivery acknowledgment for a plurality of terminals. It may be defined to indicate that it is. Alternatively, it is not necessary to explicitly give such a notification.

As an example, the RA field in the BA frame may be a broadcast address or a multicast address. In the Multi-User subfield of the BA Control field, the number of users (number of terminals) to be reported in the BA Information field may be set. The BA Information field includes a subfield for association ID, a Block Acack Starting Sequence Control subfield, and a Block Acck bitmap (Block) for each user (terminal).
Acck Bitmap) Places a subfield.

AID is set in the association ID subfield to identify the user. More specifically, as shown in FIG. 12C, as an example, a part of the Per TID Info field is used as a subfield for the association ID. Currently, 12 bits (B0 to B11) are reserved areas. The first 11 bits (B0-B10) are used as a subfield for the association ID. The Block Ack start sequence control subfield and the Block Ack bitmap subfield may be omitted if the frame transmitted by the terminal is a single data frame (not an aggregation frame). When the frame transmitted by the terminal is an aggregation frame, the Block Ack start sequence control subfield stores the sequence number of the first MSDU (medium access control (MAC) service data unit) of the delivery acknowledgment indicated by the Block Acck frame. do. In the Block Acck bitmap subfield, a bitmap (Block Acck bitmap) consisting of bits for success / failure of reception of each sequence number after the Block Acack start sequence number may be input.

The terminal receiving the Multi-STA BA frame 502 confirms the Type and Subtype of the frame control field. When it is detected that these are control and BlockAck, then the RA field is checked, and since this value is a broadcast address, etc., each data frame in the frame transmitted by the own terminal (in the case of an aggregation frame). The information of the delivery confirmation response (success or failure) to the user is specified from the Block Ack Bitmap field, and it is determined whether or not the transmission of each data frame is successful. For example, the TID Info subfield that stores the AID of the own terminal is set to BA.
Specify from within the Information field, specify the value (start sequence number) set in the Block Acack Starting Sequence Control subfield following the specified TID Info subfield, and confirm whether or not the transmission of each sequence number after the start sequence number is successful. Is specified from the Block Acc bitmap. The bit length of the AID may be shorter than the length of the TID Info subfield, and the AID is, for example, 11 bits from the beginning of a part of the TID Info subfield (for example, 2 octets (16 bits)) as described above. It is stored in B0-B10)).

When a plurality of terminals transmit a single frame in UL-OFDMA instead of an aggregation frame (this case is assumed in the sequence of FIG. 7), for example, the following may be performed. As shown in FIG. 12C, one bit in the TID Info subfield of each BA information field (for example, the 12th bit from the beginning of 2 octets (16 bits) (B11 if the head is B0)). Is used as a bit (ACK / BA bit) indicating whether it is ACK or BA, and a value indicating ACK is set in the bit. When a value indicating ACK is set, the Block Acack Starting Sequence Control subfield and the Block Acack Bitmap subfield are omitted.
This makes it possible to notify the ACK of a plurality of terminals in one BA frame. Since it is not necessary to notify ACK for a terminal whose inspection result fails, it is not necessary to notify the terminal in the Multi-STA BA frame. Since the receiving terminal does not have the ACK of its own terminal, it can be determined that the transmission has failed. In this way, regardless of whether the plurality of terminals transmit the aggregation frame or the single frame, the delivery confirmation to the plurality of terminals can be performed by the single delivery confirmation response frame diverted from the BA frame.

When transmitting the Multi-STA BA frame 502, the access point transmits the Multi-STA BA frame 502, for example, in the same frequency band as the random access trigger frame 501 or UL-OFDMA, or in the band with a basic channel width of 20 MHz. You may.

As a method other than transmitting the Multi-STA BA frame, a delivery acknowledgment frame (ACK frame, BA frame, etc.) may be transmitted individually for each terminal. At this time, the delivery confirmation response frame may be transmitted to a plurality of terminals at the same time by using DL-OFDMA.

FIG. 13 shows a configuration example of a physical packet when a delivery confirmation response frame is transmitted to a plurality of terminals by DL-OFDMA. The fields of L-STF, L-LTF, and L-SIG are transmitted with a channel width of 20 MHz as an example, and the same value (same symbol) is set in any of the delivery confirmation response frames for each terminal. The SIG1 field sets common information for a plurality of terminals, and specifies, for example, a resource unit used for reception for each terminal. For example, information in which the terminal identifier and the resource unit number (identifier) are associated with each other is set. The identifier of the terminal may be an association ID (AID) or a part of the AID (Partial).
It may be AID) or another identifier such as a MAC address. The SIG1 field is also transmitted, for example, with a channel width of 20 MHz. Each terminal can decode the SIG1 field. The SIG2 field is set individually for each resource unit, and as an example, information such as MCS required for decoding the corresponding data field may be set. Therefore, each terminal that receives the signal from the access point can grasp the resource unit to be decoded by its own terminal by decoding the SIG1 field. Each terminal receives a delivery confirmation response frame by decoding the signal of the designated resource unit. Note that the format example of FIG. 13 is an example, and one or more other fields may be arranged before and after the SIG2 field or before and after the SIG1 field. The other field may be a 20 MHz bandwidth or a resource unit width. Some or all of the other fields may be composed of known symbols as well as L-STF and L-LTF.

As a method other than transmitting the delivery confirmation response frame to a plurality of terminals by DL-OFDA, the delivery confirmation response frame may be transmitted to a plurality of terminals by downlink MU-MIMO.
DL-MU-MIMO uses a technique called beamforming to form and transmit spatially orthogonal beams to a plurality of terminals. DL-MU-MIMO is defined in the IEEE802.11ac standard, and may be executed in accordance with the standard.

After transmitting the Multi-STA BA frame 502, the base station transmits the random access trigger frame 503 at a predetermined timing or an arbitrary timing. In the configuration of the random access trigger frame 503, it is assumed that RU # 1 to RU # 4 are designated as STA undesignated RUs as in the random access trigger frame 501. Arbitrary communication may be performed between the transmission of the Multi-STA BA frame 502 and the transmission of the random access trigger frame 503. For example, UL-OFDMA communication may be performed using a normal trigger frame (a trigger frame that does not include the designation of the STA undesignated RU).

The terminals 1 to 8 hold the OBO value (backoff value) updated when the previous random access trigger frame 501 was received. However, since the terminals 2, 4 and 5 have been transmitted (random access) to the random access trigger frame 501, the OBO value is again taken from the range of 0 or more and CWO or less. Here, it is assumed that the CWO value is the same value 31 as the previous time. Then, it is assumed that terminals 2, 4, and 5 select 23, 7, and 18, respectively from [0, 31]. Therefore, the OBO values of the terminals 1 to 8 (STA1 to 8) are as follows.
STA 1 OBO = 6
STA 2 OBO = 23
STA 3 OBO = 1
STA 4 OBO = 7
STA 5 OBO = 18
STA 6 OBO = 4
STA 7 OBO = 4
STA 8 OBO = 6
In the random access trigger frame 503, the number of STA unspecified RUs is 4, so 4 is subtracted from each of the OBO values of each terminal, and the updated (subtracted) OBO is as follows. Values smaller than 0 are fixed at 0.
STA 1 OBO = 6-4 = 2
STA 2 OBO = 23-4 = 19
STA 3 OBO = 1-4 = -3 (→ 0)
STA 4 OBO = 7-4 = 3
STA 5 OBO = 18-4 = 14
STA 6 OBO = 4-4 = 0
STA 7 OBO = 4-4 = 0
STA 8 OBO = 6-4 = 2

Since it is the terminals 3, 6 and 7 that the updated OBO value reaches the predetermined value (= 0), the terminals 3, 6 and 7 acquire the selection right. Terminals 3, 6 and 7 randomly select resource units from RU # 1 to RU # 4, which are STA undesignated RUs designated by the random access trigger frame 503. Here, it is assumed that RU # 2 is selected for the terminal 3, RU # 4 is selected for the terminal 6, and RU # 1 is selected for the terminal 7. It is assumed that one resource unit is selected, but two or more resource units may be allowed to be selected. Terminals other than terminals 3, 6 and 7 cannot acquire the selection right because the updated OBO value is larger than 0, and wait for the next random access trigger frame to be transmitted.

The terminals 3, 6 and 7 transmit frames 523, 526 and 527 using RU # 2, RU # 4, and RU # 1, respectively, after a predetermined time from the completion of reception of the random access trigger frame 503. The frame to be transmitted may be a predetermined type or a frame arbitrarily determined by each terminal. Since RU # 3 was not selected for any terminal, transmission is not performed in RU # 3. If a resource unit other than RU # 1 to RU # 4 is designated as another terminal in the random access trigger frame 503, the terminal may transmit the frame in the designated resource unit. In this case, the terminal and the terminals 3, 6 and 7 simultaneously perform uplink transmission (UL-OFDMA transmission). The frame transmitted by the terminals 3, 6 and 7 may be an aggregation frame (A-MPDU) in which a plurality of data frames and the like are aggregated.

The base station receives and decodes frames 527, 523, and 526 transmitted from terminals 7, 3, and 6 at RU # 1, RU # 2, and RU # 4, and FCS inspection (CRC inspection, etc.) of the decoded frames. By doing so, it is determined whether the frame has been successfully received. The base station generates and transmits (downlink response) a delivery confirmation response frame according to the inspection result (successful reception) of each frame. Similar to the above, here, the Multi-STA BA frame 504 is transmitted as a single delivery confirmation response frame representing all delivery confirmations of terminals 3, 6 and 7. The operation of the terminal receiving the Multi-STA BA frame 504 is the same as that of the Multi-STA BA frame 502.

Based on the above description, the sequence of operations according to the features of the present embodiment will be described. FIG. 14 shows an example of this sequence. The same or corresponding elements as those in FIG. 7 are designated by the same reference numerals. FIG. 15 is a supplementary diagram for explaining the sequence of FIG. In the sequence example of FIG. 7, when a plurality of terminals that have acquired the selection right to the STA undesignated RU randomly select a resource unit, the resource unit selected by each terminal is different. Therefore, the frame transmitted from each terminal was normally received by the base station. On the other hand, in the sequence example of FIG. 14, it is assumed that the base station cannot normally receive the frames transmitted from the plurality of terminals because the plurality of terminals select the same resource unit. In such a case, one of the features of the present embodiment is to adjust the CWO value so as to raise the priority of acquiring the selection right of the terminal that failed to transmit (the CWO value is 31 in the sequence of FIG. 7). Was fixed to).
As an example, in this sequence, the terminal that fails to transmit makes the CWO value smaller than the previous CWO value. By such control, fairness between terminals is ensured. Hereinafter, the sequence of FIG. 14 will be described in detail. The difference from FIG. 7 will be mainly described, and the description overlapping with FIG. 7 will be omitted.

When the base station decides to start UL-OFDMA, it transmits a random access trigger frame (TF-R) 501. In the random access trigger frame 501, four resource units (RU # 1, RU # 2, RU # 3, RU # 4) are specified, and all resource units are set as STA undesignated RUs and AID " "X" is set.

Terminals 1 to 8 decode the random access trigger frame 501, and of the four resource units RU # 1, RU # 2, RU # 3, and RU # 4, the use of their own terminal may be specified. It is determined whether or not there is, and here, since AID "X" is set for any of the resource units, it is determined that all the resource units are resource units for random access.

Terminals 1 to 8 hold backoff values (OBO values) randomly selected from a range of 0 or more and CWO values or less. CWO is selected from the range of CWOmin and CWOmax. Here, it is assumed that the initial value CWOini (= 31) is selected for each terminal. The terminals 1 to 8 update the OBO value by subtracting the number of STA unspecified RUs in the random access trigger frame 501 from the backoff value of the own terminal. When the updated OBO value reaches a predetermined value (here, 0), the selection right to the STA undesignated RU is acquired.

Here, the OBO values of the terminals 1 to 8 (STA 1 to 8) are STA 1 OBO = 10 respectively.
STA 2 OBO = 3
STA 3 OBO = 5
STA 4 OBO = 4
STA 5 OBO = 1
STA 6 OBO = 8
STA 7 OBO = 2
STA 8 OBO = 10
Since the number of STA unspecified RUs is 4 in the random access trigger frame 501, 4 is subtracted from each, and the updated OBO value is as follows. Values smaller than 0 are fixed at 0.
STA 1 OBO = 10-4 = 6
STA 2 OBO = 3-4 = -1 (→ 0)
STA 3 OBO = 5-4 = 1
STA 4 OBO = 4-4 = 0
STA 5 OBO = 1-4 = -3 (→ 0)
STA 6 OBO = 8-4 = 4
STA 7 OBO = 2-4 = -2 (→ 0)
STA 8 OBO = 10-4 = 6

Since the updated OBO has reached the predetermined value (0) in the terminals 2, 4, 5, and 7, the terminals 2, 4, 5, and 7 acquire the selection right. Terminals 2, 4, 5, and 7 randomly select resource units from RU # 1 to RU # 4, which are STA undesignated RUs designated by the random access trigger frame 501. Here, it is assumed that RU # 4 is selected for the terminal 2, RU # 3 is selected for the terminal 4 and the terminal 7, and RU # 1 is selected for the terminal 5. Terminal 4 and terminal 7 have selected the same resource unit. Terminals other than terminals 2, 4, 5, and 7 cannot acquire the selection right because the updated OBO value is larger than 0, and wait for the next random access trigger frame to be transmitted.

Terminals 2, 4, 5, and 7 use RU # 4, RU # 3, RU # 1, and RU # 3, respectively, after a predetermined time from the completion of reception of the random access trigger frame 501, to use frames 512, 514, respectively. 515, 517 are transmitted. Frames are transmitted from the terminal 4 and the terminal 7 with the same resource unit (see the shaded area in FIG. 15).

The base station receives and decodes the frame 515 transmitted from the terminal 5 in the RU # 1, the frames 514 and 517 transmitted from the terminals 4 and 7 in the RU # 3, and the frame 512 transmitted from the terminal 2 in the RU # 4. Then, the decoded frame is inspected by FCS (CRC inspection or the like) to determine whether the frame has been successfully received. Succeeded in receiving the frame 515 of the terminal 5 received by RU # 1 and the frame 512 of the terminal 2 received by RU # 4, and failed to receive the frames 514 and 517 of the terminals 4 and 7 received by RU # 3. And.

The base station has succeeded in receiving frames 512 and 515 transmitted from terminals 2 and 5 as delivery confirmation response frames according to the inspection result (successful reception) of each frame. 507 is transmitted. Since the reception of frames 514 and 517 transmitted from terminals 4 and 7 failed, the ACK for terminals 4 and 7 is not included in the Multi-STA BA frame 507. When an aggregation frame containing a plurality of data frames is transmitted from terminals 4 and 7, if reception of all the aggregated data frames fails, the response to terminals 4 and 7 is Multi-STA.
Not included in BA frame 507. If a part of the data frame is successfully received, the Block Ack start sequence control subfield and the Block Ack bitmap subfield may be used to notify the data frame that has been partially received.

Among the terminals that received the Multi-STA BA frame 507, the terminals 2, 4, 5, and 7 indicate whether the Multi-STA BA frame 507 contains an ACK for the frames 512, 514, 515, and 517 transmitted by the terminal. confirm. The terminals 2 and 5 have detected that the ACK of the frames 512 and 515 transmitted by the own terminal is included, but the terminals 4 and 7 cannot confirm the ACK of the frames 514 and 517 transmitted by the own terminal. Judge that the transmission failed. Here, transmission failure means that multiple terminals in the same resource unit could not receive the frame normally at the base station that transmitted the frame (in this example), and in a certain resource unit, only one terminal. This includes the case where the frame is transmitted, but the base station fails to receive the frame due to the poor radio wave environment. If the downlink response frame such as the Multi-STA BA frame is not received within a certain time (SIFS time or the like) from the completion of the transmission of the frames 512, 514, 515, and 517, it may be determined that the transmission has failed. If the terminal transmits an aggregation frame that aggregates multiple data frames and succeeds in transmitting some data frames, as an example, the terminal determines that the transmission (random access) is successful, and all of them are If the transmission of the data frame of is unsuccessful, it may be determined that the transmission (random access) has failed.

After transmitting the Multi-STA BA frame 507, the base station transmits the random access trigger frame 503 at a predetermined timing or at an arbitrary timing. In the configuration of the random access trigger frame 503, it is assumed that RU # 1 to RU # 4 are designated as STA undesignated RUs as in the random access trigger frame 501. It should be noted that arbitrary communication may be performed between after the Multi-STA BA frame 505 and before the transmission of the random access trigger frame 503. For example, a communication is performed in which a base station transmits a normal trigger frame (a trigger frame in which a terminal is specified for each source unit), and each terminal performs uplink transmission (UL-OFDMA) using the specified resource unit. It doesn't matter.

The terminals 1 to 8 hold the OBO value (backoff value) updated when the previous random access trigger frame 501 was received. However, for terminals 2, 4, 5, and 7, since random access was performed to the random access trigger frame 501, the OBO value is selected again from the range of 0 or more and CWO or less. However, terminals 2 and 5 succeeded in transmission, and terminals 4 and 7 failed in transmission. Therefore, the present embodiment is characterized in that the CWO is selected as follows.

The terminals 4 and 7 that failed to transmit select a CWO smaller than the previous time (CWO = 31) in the range of CWOmin and CWOmax. CWO is gradually reduced to CWOmin each time transmission fails. If the transmission is successful, the process returns to the initial CWOini (for example, 31).

As an example, CWOmin = 1, CWOmax = 31, and the initial CWOini is 31 which is CWOmax. Each time the transmission fails, the CWO is gradually reduced from 31 to 1. A fixed value may be cumulatively subtracted from 31 each time a failure occurs, or a larger value may be cumulatively subtracted as the number of failures increases. As an example of the latter, 1 may be subtracted for the 1st failure, 2 for the 2nd failure, and 3 for the 3rd failure. In this case, if the CWO at the start is 31, the CWO after the first failure is 30 (= 31-1), the CWO after the second failure is 28 (= 30-2), and the CWO after the third failure is 25 (= 31-1). = 28-3) ... The adjustment amount of how much the CWO value is adjusted (decreased here) may be notified from the base station to the terminal. As the direction of notification, the same method as various notification methods described later may be used.

Alternatively, the calculation formula of CWO may be defined as "2 ^ P-1" by using the power part P, and the value of P may be reduced each time the failure is repeated. As an example, in the case of CWOmax, if P = 5, CWOmax = 2 ^ 5-1 = 31. In the case of CWOmin = 1, if P = 1, then CWOmin = 2 ^ 1-1 = 1. At the start, CWO is assumed to match CWOmax. In this case, the CWO is updated as follows every time the failure is repeated.
At the start 31 (= 2 ^ 5-1)
-<At the time of failure> → 15 (= 2 ^ 4-1)
-<At the time of failure> → 7 (= 2 ^ 3-1)
-<At the time of failure> → 3 (= 2 ^ 2-1)
-<At the time of failure> → 1 (= 2 ^ 1-1)
The state of this update is schematically shown in FIG. If the transmission is successful, CWO returns to CWOmax = 31. The value of P may be notified from the base station to the terminal. As the direction of notification, the same method as various notification methods described later may be used. The value of P is also an example of the adjustment amount.

When the latter method is used, in this sequence, if the terminals 4 and 7 are the first failures, the CWO is, for example, 15 (= 2 ^ 4-1), respectively. Since terminals 2 and 5 have succeeded in transmission, 31 (= 2 ^ 5-1), which is the initial CWOini (= CWOmax), is still used as the CWO.

It is assumed that the terminals 4 and 7 randomly select an OBO value (backoff value) from [0, 15], the terminal 4 selects 7, and the terminal 7 selects 4 (see FIG. 15). It is assumed that terminals 2 and 5 randomly select an OBO value (backoff value) from [0, 31], terminal 2 selects 23, and terminal 5 selects 18 (see FIG. 15). For terminals other than these, the OBO value currently held is used as it is.

Therefore, the OBO values of the terminals 1 to 8 (STA1 to 8) are as follows (as a result, the OBO values of the terminals are the same as in the sequence example of FIG. 7).
STA 1 OBO = 6
STA 2 OBO = 23
STA 3 OBO = 1
STA 4 OBO = 7
STA 5 OBO = 18
STA 6 OBO = 4
STA 7 OBO = 4
STA 8 OBO = 6

In the random access trigger frame 503, the number of STA unspecified RUs is 4, so 4 is subtracted from each of the OBO values of each terminal, and the updated OBO value is as follows. Values smaller than 0 are fixed to 0 (as a result, the OBO value of each terminal is the same as in the sequence example of FIG. 7).
STA 1 OBO = 6-4 = 2
STA 2 OBO = 23-4 = 19
STA 3 OBO = 1-4 = -3 (→ 0)
STA 4 OBO = 7-4 = 3
STA 5 OBO = 18-4 = 14
STA 6 OBO = 4-4 = 0
STA 7 OBO = 4-4 = 0
STA 8 OBO = 6-4 = 2

Since the updated OBO value reaches the predetermined value (0) at the terminals 3, 6 and 7, the terminals 3, 6 and 7 acquire the selection right. Terminals 3, 6 and 7 randomly select resource units from RU # 1 to RU # 4, which are STA undesignated RUs designated by the random access trigger frame 503. Here, it is assumed that RU # 2 is selected for the terminal 3, RU # 4 is selected for the terminal 6, and RU # 1 is selected for the terminal 7. Terminals other than terminals 3, 6 and 7 cannot acquire the selection right because the updated OBO value is larger than 0, and wait for the next random access trigger frame to be transmitted.

The terminals 3, 6 and 7 transmit frames 523, 526 and 527 using RU # 2, RU # 4, and RU # 1, respectively, after a predetermined time from the completion of reception of the random access trigger frame 503. Since RU # 3 was not selected for any terminal, transmission is not performed in RU # 3. The frame transmitted by the terminals 3, 6 and 7 may be an aggregation frame (A-MPDU) in which a plurality of data frames and the like are aggregated.

The base station receives and decodes frames 527, 523, and 526 transmitted from terminals 7, 3, and 6 at RU # 1, RU # 2, and RU # 4, and FCS inspection (CRC inspection, etc.) of the decoded frames. By doing so, it is determined whether the frame has been successfully received. The base station generates and transmits (downlink response) a delivery confirmation response frame according to the inspection result (successful reception) of each frame. Similar to the above, here, the Multi-STA BA frame 504 is transmitted as a single delivery confirmation response frame representing all delivery confirmations of terminals 3, 6 and 7. The operation of the terminal receiving the Multi-STA BA frame 504 is the same as that of the Multi-STA BA frame 502.

The values of CWOmax and CWOmin may be notified from the base station to the terminal group belonging to BSS by a beacon frame or a trigger frame (including a trigger frame for random access). When notifying by a trigger frame, a field for setting CWOmax and CWOmin may be provided in a common information field, a terminal information field, or the like. The initial value (CWOini) of CWO may be notified in the same manner, or may be predetermined by the system or standard.

The difference between the update of the CWO value according to the present embodiment and the update of the contention window (CW) used in the random backoff mechanism of CSMA / CA will be described. It is assumed that a terminal performs backoff (carrier sense) in CSMA / CA for a time based on CW, and transmits as a carrier sense idle. At this time, if the transmission with another terminal happens to be the same, the terminal determines that there is no ACK response by ACK Timeout and increases the CW value exponentially. The initial value of the CW value is CWmin, and the CW value is increased up to CWmax as the retransmission is performed. This is a measure for further variation on the time axis in order to avoid simultaneous transmission based on the judgment that the CW values used for competing terminals did not sufficiently vary. On the other hand, in the mechanism of the random access trigger frame of the present embodiment, there are two types of terminals that can acquire the STA undesignated RU and the terminals that cannot acquire the STA undesignated RU among the plurality of terminals that have acquired the selection right at the same time (CSMA). In the random backoff mechanism of / CA, the terminals that transmitted at the same time basically fail to transmit (there is no ACK response). This point is different from the random backoff mechanism on the time axis. At that time, it is unfair to use the same conditions for the acquisition of the STA undesignated RU in the next random access trigger frame between the terminal that could acquire the STA undesignated RU and the terminal that could not acquire the STA undesignated RU. Therefore, in the present embodiment, the CWO value of the terminal that has failed to be acquired is reduced each time the failure is repeated, so that the priority of acquisition is higher than that of the terminal that has succeeded in acquisition, thereby improving the fairness between the terminals. Secure.

In the above-described embodiment, the delivery confirmation response frame (Multi-STA BA frame) is transmitted as a downlink response to a plurality of terminals that have been successfully transmitted (randomly accessed), but instead of transmitting the delivery confirmation response frame, a delivery confirmation response frame is usually transmitted. It is also possible to send the trigger frame of. An example of the sequence in this case is shown in FIG.

The Multi-STA BA frames 507 and 504 of FIG. 14 replace the trigger frames 541 and 542. In the trigger frames 541 and 542 in this case, the terminal to be assigned to each resource unit is specified. The format of the trigger frame is basically the one shown in FIG. 9, and the configuration of the common information field, the terminal information field, or both of them may be different from that of the random access trigger frame. The terminal specified by the trigger frames 541 and 542 uplink-transmits a frame such as a data frame after a predetermined time from the completion of reception of the trigger frames 541 and 542 by using the resource unit assigned to the own terminal. .. The frame to be transmitted may be an aggregation frame in which a plurality of data frames and the like are aggregated.

When transmitting the trigger frames 541 and 542, the base station specifies a terminal that has succeeded in transmitting by random access to the random access trigger frames 501 and 503. As a result, the terminal that succeeds in transmission can grasp that the random access to the random access trigger frames 501 and 503 is successful by designating the own terminal in the trigger frames 541 and 542. Further, among the terminals that have been randomly accessed, the terminals that are not specified by the trigger frames 541 and 542 can be determined to have failed in the transmission of the own terminal. The frame transmitted by random access may be a frame for notifying the allocation request in the trigger frames 541 and 542. It is also possible to specify a terminal that has not been randomly accessed or a terminal that has failed to transmit with the trigger frames 541 and 542. In addition to the information for designating the resource unit and the terminal, the trigger frames 541 and 542 may further include information necessary for transmission by the terminal (packet length, transmission power, MCS, etc.). The terminal designated by the trigger frame may be selected by the MAC processing unit 10 (for example, the MAC common processing unit 20, the reception processing unit 40, the transmission processing unit 30, etc.) or the MAC / PHY management unit 60.

(Modification example 1 of CWO update)
In the above-described embodiment, the CWO value of the terminal is reduced each time the transmission fails, but in the modified example 1, in addition to this, the CWO value is increased each time the transmission is successful, and the initial value of CWO (CWOini) is set. , CWOmin and CWOmax. The value of CWOinit may be notified from the base station to the terminal by a beacon frame, a trigger frame, or the like.

The operation of the modified example 1 is schematically shown in FIG. First, the value of CWO is set to CWOinit. In this example, 2 ^ 3-1 = 7, which is the median value of CWOmin and CWOmax (the median value of the exponentiation part). If it succeeds, it goes up one step (power part P is added by 1), and if it fails, it goes back one step (power part P is subtracted by 1). Specific examples are shown below.
At the start 7
-<Successful transmission> → 15
-<Successful transmission> → 31
-<Send failure> → 7
-<Send failure> → 3

(Modification example 2 of CWO update)
Start the initial CWOini from CWOmin. In case of transmission failure, CWO is maintained, and in case of transmission success, CWO is gradually increased to CWOmax. The operation according to the second modification is schematically shown in FIG.

Initially, the value of CWO is set to CWOmin (2 ^ 3-1 = 7 in this example). If successful, increase by one step (add 1 to the power part P) and maintain the CWO value (maintain the value of the power part P). Specific examples are shown below.
At the start 7
-<Successful transmission> → 15
-<Successful transmission> → 31
-<Send failure> → 15
-<Send failure> → 7

This method is similar to the above-mentioned method for determining CW by the CSMA / CA random backoff mechanism, but differs in the following points. In this modification 2, the CWO value is increased each time it succeeds, whereas in the CSMA / CA random backoff mechanism, the CW is increased each time it fails. Therefore, both have the opposite behavior on failure and success.

(Modification example 3 of CWO update)
Modification 3 is used in combination with the above-described embodiment and the first and second modifications. In the third modification, the CWO value is changed when the same determination (success or failure) is made N times in a row. Otherwise, keep the same CWO. The value of N is a beacon frame, a trigger frame, or the like, and the base station notifies the terminal belonging to the BSS. As an example, N may be 2 or 3 or more.

For example, when this modification 3 is combined with a form in which the CWO is reduced when transmission fails, the CWO value is reduced when N consecutive failures occur. If the consecutive failures are interrupted (successful) by the N-1th time, the CWO value is not changed. Further, when combined with a form in which the CWO value is increased when the transmission is successful, the CWO value is increased when the transmission is successful N times in a row. If the success of the N-1th time is interrupted (failed), the CWO value is not changed.

(Modification example 4 of CWO update)
As an operation of the base station, the beacon frame notifies the time until the next random access trigger frame (TF-R) is transmitted, for example, as a target transition time. In the next random access trigger frame, it is notified whether or not the random access trigger frame is continuously transmitted. For example, Cascaded the more data field of the Frame Control field.
When it is used as an Incidation bit and it is notified that a subsequent random access trigger frame exists (planned), the bit is set to 1. To notify that the subsequent random access trigger frame does not exist (not scheduled), set the bit to 0. A Cascaded Incidation bit may be provided in a common information field of a random access trigger frame, a terminal information field, a reserved area of a MAC header, or the like.

FIG. 20 shows an example of a sequence of operations of the base station according to this modification. In the beacon frame 551, the time until the start of the next random access trigger frame 561 is set.
Notify as a transmission time. For example, an information element for notifying the target transition time may be newly defined. In the random access trigger frame 561, the subsequent random access trigger frame 562 is scheduled to be transmitted, so the Cascaded Incidation bit is set to 1. In the random access trigger frame 562, since the subsequent random access trigger frame 563 is scheduled, the Cascaded Incidation bit is set to 1. In the random access trigger frame 563, since the subsequent random access trigger frame is not scheduled, the Cascaded Incidation bit is set to 0. In FIG. 20, the illustration of other frames transmitted by the base station (for example, the illustration of the Multi-STA BA frame) is omitted.

In such a sequence, if a random access trigger frame with a Cascaded Incidation bit of 1 is received (followed by the next random access trigger frame), the terminal will set the CWO value according to previous embodiments or variants. , Update as needed. When a random access trigger frame with a Cascaded Incidation bit of 0 is received (when it is considered that it takes a long time to receive the next random access trigger frame), the CWO value is reset to the initial value (CWOini). return. In this sequence example, when a terminal in the power save mode exists, the terminal that has received the beacon frame 551 grasps the time until the next random access trigger frame 561, and shifts to the sleep mode during the time. You may. Further, after receiving the trigger frame 563 for random access in which the Cascaded Incidation bit is 0, random access may be performed as necessary, and then the sleep mode may be entered. It should be noted that this modification can also be applied to a normal terminal that is not in the power save mode. This modification can be used in combination with the above-described embodiment or other modifications.

(Variation example 5 of CWO update)
When the base station determines that there are many terminals that have failed in transmission in response to the random access trigger frame (UL-OFDMA), it may instruct to forcibly return the CWO value to CWOmax or CWOinit. For example, a bit (field) for notification is defined in the trigger frame for random access, and the bit is used to instruct to return the CWO value to CWOmax or the initial value (CWOinit). The bit may be provided in the common information field or the terminal information field, or the reserved area of the existing field may be used. Even if the terminal receiving the instruction fails to transmit, if the bit for the notification is 1 in the next random access trigger frame, the CWO is returned to the initial value or CWOmax (whether to return to the initial value or CWOmax). You may add a bit of pre-determined or which to choose). The timing for returning the CWO value to CWOmax or CWOinit may be the timing for updating the CWO value next (timing when transmission succeeds or fails), or it may be changed immediately and the backoff value (OBO value) may be used as the changed CWO value. ) May be taken again. As another example, an instruction for prohibiting the terminal from lowering the CWO value can be considered. By adjusting the CWO value as in this modification, the timing of random access of the terminal can be varied. It should be noted that the CWO value may be instructed to return to a value other than CWOmax or CWOini, for example, between CWOmax and CWOmin. The instruction to change the CWO value to CWOmax, CWOini, etc. may be applied to both the terminal that failed in transmission and the terminal that succeeded, or may be applied to at least one of them. In the latter case, a field for notifying the terminal that failed to transmit (notification field) and a notification field for the terminal that succeeded in transmitting may be defined, and instructions for changing the CWO value may be set separately for each.

Here, the determination that the number of terminals that have failed in transmission in the base station is large may be determined when the number of terminals that failed or the number of resource units that failed in transmission is equal to or greater than the threshold value. Alternatively, the ratio of the number of resource units that failed to receive to the number of STA unspecified RUs (or the total number of resource units that succeeded or failed to receive) specified in the trigger frame for random access may be greater than or equal to the threshold value. Method may be used. This modification can be used in combination with the above-described embodiment or other modifications.

(Variation example 6 of CWO update)
If there is no downlink response (response of delivery confirmation response frame such as Multi-STA BA frame) from the base station after the terminal sends a response to the trigger frame for random access (random access), CWO is set to CWOmax or the initial value. It may be returned to (CWOinit). In such a case, it is determined that there are many terminals that have failed in transmission. Therefore, by changing the CWO value in this way, the timing of random access of the terminals can be varied. Instead of setting the CWO value to CWOmax or the initial value (CWOinit), the previous CWO value may be maintained as it is. This modification can be used in combination with the above-described embodiment or other modifications.

Although a normal trigger frame (see 541 and 542 in FIG. 17) was transmitted as the downlink response, in the normal trigger frame, only the terminal already specified in the random access trigger frame is specified. If so, the terminal may be operated according to the case where there is no downlink response from the base station. In addition, if the terminal specified by the random access trigger frame does not exist, or if there is no uplink transmission from the specified terminal, the base station may not transmit the normal trigger frame. .. Also at this time, the operation may be performed according to the case where there is no downlink response.

Further, the terminal may operate as follows. When there is a downlink response (Multi-STA BA frame, etc.) from the base station, the number of terminals successfully transmitted in the STA undesignated RU is counted. If the transmission of the own terminal fails and the number of successful terminals is equal to or greater than the threshold value, or if the ratio of the number of successful terminals to the number of STA unspecified RUs is equal to or greater than the threshold value, the CWO value may be lowered, for example. good. Alternatively, the downlink response frame transmitted from the base station may be provided with a field of a notification bit instructing the CWO value to be lowered, and the base station may instruct the CWO value to be lowered by the bit. In this case, the terminal lowers the CWO value according to the bit. The method for lowering the CWO may follow the above-described embodiment or modification.

(Modified example of operation when transmission fails)
The terminal maintains and uses the OBO value (OBO value before subtracting the number of STA unspecified RUs) used when transmission in the STA unspecified RU fails for the next random access trigger frame. May be good.

On the other hand, on the base station side, it is determined by the response to the random access trigger frame (UL-OFDA) whether there are many terminals that have failed in transmission, and if it is determined that there are many terminals, the next random access trigger frame is used. The number of STA undesignated RUs may be increased.
This takes into consideration the possibility that additional terminals will be newly acquired.
Alternatively, a random access trigger frame that specifies only the terminal that failed to transmit as the target of random access may be defined, and the frame may be transmitted. For example, even if a notification bit that specifies only the terminal that failed to be transmitted as the target of random access is provided in the common information field, terminal information field, or MAC header, and the notification bit is turned on, a random access trigger frame is transmitted. good. The notification bit may utilize the reserved area of any field in the MAC header, or the used area may be reused for this purpose.

(Modified example of operation when transmission is successful)
The base station may give a limit on the number of waits or a waiting time for a terminal that has succeeded in transmission (successfully in random access) to be able to respond to a trigger frame for random access (random access is possible) from the next time onward.

The information of this restriction is sent to the downlink response after the base station receives the response (UL-OFDMA) to the trigger frame for random access, together with the information of the terminal that succeeded in receiving, via the notification field for the successful terminal. Just notify. When the downlink response is in BA format (such as when a Multi-STA BA frame is used), the notification field may be configured by using the reserved area of the BA format frame or reusing the used area. When a trigger frame is used as a downlink response, the notification field may be provided in a common information field, a terminal information field, a MAC header, or the like. In the trigger frame, it is assumed that the terminal that has succeeded in the above transmission is designated as the target of UL-OFDMA.

When the terminal detects that the transmission is successful due to the ACK of the own terminal or the designation of the own terminal in the frame of the downlink response, the restriction on the number of waits or the waiting time is restricted from the notification field of the frame of the downlink response. Is detected, and while the constraint is applied, it operates to refrain from transmission (random access).

When the constraint is the number of waits, the number of waits is decremented each time a random access trigger frame is received, and when it becomes 0, the operation related to random access (STA from the OBO value) from the subsequent reception of the random access trigger frame. Processing to subtract the number of unspecified RUs, etc.) is started. If the constraint is a waiting time, the device waits for a specified time and then starts the operation related to random access from the reception of the random access trigger frame.

While the above constraint is applied, the OBO value (OBO value before subtracting the number of STA unspecified RUs) when the previous transmission was successful is maintained, and the trigger for random access after the constraint is lifted. When the frame is received, the number of STA unspecified RUs is subtracted from the maintained OBO value, and when it reaches 0, the selection right is acquired and random access is performed. Instead of maintaining the OBO value, the OBO value may be newly taken from the current CWO.

(Modified example of response method of base station)
The base station measures the reception quality of the terminal that succeeded in transmission in response to the trigger frame for random access for the resource unit in which the transmission was performed. Examples of reception quality include, but are not limited to, receive RSSI (Received Signal Strength Indicator) or receive EVM (Error Vector Magnitude). For example, the signal-to-noise ratio (SN ratio) may be used. The base station determines whether the measured value is below or above a certain value or above a certain value, depending on the index used, and determines whether the reception quality meets the criteria required for the response (whether it is bad or not). ..

The base station determines that the radio wave environment of the terminal in the resource unit is bad for the terminal with poor reception quality, and does not make a downlink response (the Multi-STA BA frame does not include the ACK of the terminal, or the trigger frame. Do not specify the terminal in). As a result, the terminal is made to judge that the transmission (random access) has failed. The base station may make a downlink response even to a terminal having poor reception quality, and at this time, information specifying the reception quality may be added to the frame of the downlink response. If the terminal determines that the reception quality at the base station is poor although the transmission is successful based on the downlink response frame, another resource unit may be selected next time. The base station may notify the information specifying the reception quality by using the reserved area of the frame in BA format, or reuse the used area in the frame for the present purpose and notify the information. You may.

Here, the terminal selectively asks the base station whether it wants to respond regardless of the reception quality when the base station succeeds in reception, or does not want to respond when the reception quality is poor. You may be able to notify. A request bit (request field) is provided in the MAC header of the frame transmitted by the terminal, and if the reception quality is poor, the bit is set to 1, and if the response is desired regardless of the reception quality, the bit is set to 1. May be 0. The relationship between bits 1 and 0 may be reversed. The base station may switch the response operation when the reception is successful according to the request bit included in the frame.

(Modification example of random number range specification and selection of STA unspecified RU)
In the above-described embodiment or each modification, the OBO value becomes 0 or less as a result of subtracting the number of STA undesignated RUs from the OBO value, and the terminal that has obtained the selection right is an arbitrary resource unit from the STA undesignated RUs. Was selected. For example, a resource unit was randomly selected. In this modification, the resource unit to be selected is determined according to the OBO value at the time of waiting for the trigger frame for random access. For example, if the OBO value is 3 and the random access trigger frame is received and the number of STA unspecified RUs is 4, the OBO value becomes 3-4 = 1 (→ 0) and the selection right is acquired. In this case, since the OBO value during standby was 3, the resource unit corresponding to “3” (for example, RU # 3) is selected. The correspondence between the OBO value and the resource unit may be determined in advance. A plurality of resource units may be associated with one value. In this case, it may be randomly selected from the plurality of associated resource units.

As another example, every time a random access trigger frame is received, a CWO that is M (M is an integer of 1 or more) times the number of STA unspecified RUs is set. That is, the CWO is set according to the number of STA undesignated RUs. For example, if the number of STA undesignated RUs is 4 and M is 2, CWO = 8. Then, a random number (OBO value) is selected from the range from 0 to (CWO-1).
If the selected random number is less than or equal to the value obtained by subtracting 1 from the number of STA unspecified RUs (that is, "STA unspecified RU number-1"), the selection right is acquired and the resource unit is selected from the STA unspecified RUs. .. "Number of STA undesignated RU-1" is an example, and may be the number of STA undesignated RUs or another value. The resource unit may be selected by associating the OBO value with the resource unit in advance and following the association. However, it is also possible to select at random. After transmission based on the resource unit selected by the terminal, the terminal may adjust the value of M from the initial value depending on whether the transmission is successful or successful. The minimum value and the maximum value of the value of M may be defined and adjusted within the range. The method for adjusting M may be the same as that for changing the CWO in the above-described embodiment or each modification. When the CWO is made smaller, it corresponds to making M smaller, and when making the CWO larger, it corresponds to making M larger. It should be noted that setting the CWO according to the number of STA undesignated RUs described in this paragraph may be applied to other modifications.

The value of M (at least one of the initial value, the minimum value, and the maximum value) may be notified to the terminal by a beacon frame, a trigger frame (including a trigger frame for random access), or the like. An information element for notifying the value of M may be set in the beacon frame, or the value of M may be set by using the reserved area of any field of the beacon frame. Further, a field for notifying the value of M may be provided in the common information field or the terminal information field of the trigger frame, or the reserved area of the MAC header may be used, or the used area in the MAC header may be reused. Then, the value of M may be notified.

(Other variants)
In the above-described embodiment and each modification, the terminal that fails to transmit adjusts the CWO value by an autonomous judgment, but the base station may instruct the terminal to adjust the CWO value. As an example, in the trigger frame (see 541 and 542 in FIG. 14), in addition to the information specifying the terminal for each resource unit, at least one of the notification field to the terminal that failed to transmit and the notification field to the terminal that succeeded in transmitting. Information on how to adjust the CWO is set in. In the adjustment method, instructions such as making the CWO smaller, making it larger, returning it to the initial value, making it the maximum value, and making it the minimum value are set. When instructing to reduce or increase the CWO, the adjustment method may be determined in the same manner as the operation of the terminal described above. The notification field may be provided in the common information field or the terminal information field of the trigger frame. Alternatively, the notification field may be configured by using the reserved area of any field of the MAC header or by reusing the used area of the MAC header. For example, when the terminal detects that the own terminal is not specified in the trigger frame, the terminal updates the CWO value according to the adjustment method specified in the notification field for the failed terminal.

FIG. 21 shows a flowchart of an example of the operation of the terminal according to the embodiment of the present invention. The terminal receives a trigger frame (random access trigger frame) in which a plurality of STA undesignated RUs (random access resource units) are specified from the base station (S101). In the frame, the use of a specific terminal may be specified for some resource units. The terminal subtracts the number of STA unspecified RUs specified in the trigger frame for random access from the backoff value (OBO value) selected from the range below the CWO value, and the value after subtraction is a predetermined value (for example, 0). ) Is reached (S102). When the predetermined value is reached, it is determined that the selection right to the STA undesignated RU has been acquired (YES), and when the predetermined value has not been reached, it is determined that the selection right has not been acquired (NO). It should be noted that it is not necessary to actually perform subtraction, and as described above, for example, it is determined whether or not the selection right has been acquired from the magnitude relationship between the OBO value at the time of receiving the trigger frame for random access and the number of STA unspecified RUs. May be good. When the terminal acquires the selection right, the terminal transmits a frame using an arbitrary resource unit selected from the STA undesignated RU (S104). The type of the frame to be transmitted may be arbitrary, or may be a predetermined type (for example, a frame for notifying whether or not an uplink transmission is requested). The operation described here is only an example, and various operations are possible depending on the above-described embodiment and each modification.

FIG. 22 shows a flowchart of an example of the operation of the base station according to the embodiment of the present invention.
The base station transmits a trigger frame (random access trigger frame) in which a plurality of STA undesignated RUs (resource units for random access) are specified (S201). The frame may specify the use of a particular terminal for some resource units. The base station determines whether or not the frame has been received by the STA undesignated RU specified by the random access trigger frame within a certain time from the transmission (S202). More specifically, by decoding the radio signal received by each STA undesignated RU and inspecting the frame, it is determined whether or not the frame has been normally received. The base station downlinks and transmits a frame including information specifying a terminal that has normally received the frame (S203). The frame may be a Multi-STA BA frame as described above, or may be a trigger frame in which terminals are assigned to each resource unit to be used. In the case of a trigger frame, the specification of the terminal that was able to receive normally shall be included. The frame for downlink transmission may include information on a value range (CWO value) for controlling the determination of whether or not the terminal can respond to the random access trigger frame (whether or not random access is possible). As an example, information on the CWO value (initial value, minimum value or Information that specifies (such as setting instructions to the maximum value) may be included. Information about the CWO value may be set separately for each notification field for terminals that succeeded in transmission and terminals that failed to transmit, or a notification field for only one of the terminals is defined, and the information is applicable only for that terminal. Information may be set. In addition, the information described in each of the above-described modifications may be included in the frame for downlink transmission.

As described above, according to the embodiment of the present invention, fair transmission (random access) between terminals is performed by individually adjusting the CWO of each terminal according to the failure or success of transmission of each terminal to the trigger frame for random access. ) Can be provided.

In the present embodiment, the random access in the case of performing UL-OFDMA for the trigger frame for random access has been described, but the communication method combining UL-OFDMA and uplink MU-MIMO (UL-MU-MIMO) ( Random access is also possible when performing UL-OFDMA & UL-MU-MIMO). UL-MU-MIMO aims to improve the efficiency of uplink transmission by transmitting frames to a base station (spatial multiplex transmission) in the same frequency band by a plurality of terminals at the same timing. By including preamble signals that are orthogonal to each other in the physical headers of frames transmitted from multiple terminals, the base station can estimate the propagation path response of the uplink with each terminal based on these preamble signals and separate these frames. .. In UL-OFDMA & MU-MIMO, a plurality of terminals use the same resource unit for each resource unit to perform MU-MIMO transmission. At this time, a plurality of terminals using the same resource unit perform transmission using different preamble signals. This embodiment is also applicable to such a method.

(Second embodiment)
FIG. 23 is a functional block diagram of the base station (access point) 400 according to the second embodiment. This access point includes a communication processing unit 401, a transmitting unit 402, a receiving unit 403, antennas 42A, 42B, 42C, 42D, a network processing unit 404, a wired I / F 405, and a memory 406. .. The access point 400 is connected to the server 407 via a wired I / F 405. The communication processing unit 401 has the same function as the control unit 101 described in the first embodiment. The transmitting unit 402 and the receiving unit 403 have the same functions as the transmitting unit 102 and the receiving unit 102 described in the first embodiment.
The network processing unit 404 has the same function as the higher-level processing unit described in the first embodiment. Here, the communication processing unit 401 may internally hold a buffer for transferring data to and from the network processing unit 404. This buffer may be a volatile memory such as DRAM or a non-volatile memory such as NAND or MRAM.

The network processing unit 404 controls data exchange with the communication processing unit 401, data writing / reading with the memory 406, and communication with the server 407 via the wired I / F 405. The network processing unit 404 may perform communication processing higher than the MAC layer and processing of the application layer such as TCP / IP and UDP / IP. The operation of the network processing unit may be performed by processing software (program) by a processor such as a CPU, may be performed by hardware, or may be performed by both software and hardware.

As an example, the communication processing unit 401 corresponds to a baseband integrated circuit, and the transmitting unit 402 and the receiving unit 403 correspond to an RF integrated circuit that transmits and receives frames. The communication processing unit 401 and the network processing unit 404 may be configured by one integrated circuit (1 chip). The digital region processing portion and the analog region processing portion of the transmission unit 402 and the reception unit 403 may be configured by different chips. Further, the communication processing unit 401 may execute communication processing higher than the MAC layer such as TCP / IP and UDP / IP. Further, although the number of antennas is four here, it is sufficient that at least one antenna is provided.

The memory 406 stores the data received from the server 407 and the data received by the receiving unit 402. The memory 406 may be, for example, a volatile memory such as DRAM or a non-volatile memory such as NAND or MRAM. Further, SSD, HDD, SD card, eMMC and the like may be used. The memory 406 may be outside the base station 400.

The wired I / F 405 sends / receives data to / from the server 407. In the present embodiment, the communication with the server 407 is performed by wire, but the communication with the server 407 may be performed wirelessly. In this case, the wireless I / F may be used instead of the wired I / F405.

The server 407 is a communication device that receives a data transfer request requesting data transmission and returns a response including the requested data, and is assumed to be, for example, an HTTP server (Web server), an FTP server, or the like. However, it is not limited to this as long as it has a function of returning the requested data. It may be a communication device operated by a user such as a PC or a smartphone. Further, the base station 400 may be communicated wirelessly.

When the STA belonging to the BSS of the base station 400 issues a data transfer request to the server 407, a packet related to the data transfer request is transmitted to the base station 400. The base station 400 receives this packet via the antennas 42A to 42D, and the receiving unit 403 executes processing of the physical layer and the like, and the communication processing unit 401 performs processing of the MAC layer and the like.

The network processing unit 404 analyzes the packet received from the communication processing unit 401.
Specifically, check the destination IP address, destination port number, and the like. When the data of the packet is a data transfer request such as an HTTP GET request, the network processing unit 404 determines that the data requested by this data transfer request (for example, the data existing in the URL requested by the HTTP GET request) is Check if it is cached (stored) in memory 406. The memory 406 stores a table in which a URL (or its reduced representation, for example, a hash value or an alternative identifier) is associated with data. Here, the fact that the data is cached in the memory 406 is expressed as the existence of the cached data in the memory 406.

When the cache data does not exist in the memory 406, the network processing unit 404 transmits a data transfer request to the server 407 via the wired I / F 405. That is, the network processing unit 404 transmits a data transfer request to the server 407 on behalf of the STA. Specifically, the network processing unit 404 generates an HTTP request, performs protocol processing such as addition of a TCP / IP header, and passes the packet to the wired I / F 405.
The wired I / F 405 transmits the received packet to the server 407.

The wired I / F 405 receives a packet from the server 407 that is a response to the data transfer request. The network processing unit 404 grasps that the packet is addressed to the STA from the IP header of the packet received via the wired I / F 405, and passes the packet to the communication processing unit 401. The communication processing unit 401 executes the processing of the MAC layer for this packet, the transmission unit 402 executes the processing of the physical layer, and the like, and the packet addressed to the STA is transmitted from the antennas 42A to 42D.
Here, the network processing unit 404 associates the data received from the server 407 with the URL (or its reduced expression) and stores it in the memory 406 as cache data.

When the cache data exists in the memory 406, the network processing unit 404 reads the data requested by the data transfer request from the memory 406 and transmits this data to the communication processing unit 401. Specifically, an HTTP header or the like is added to the data read from the memory 406, protocol processing such as addition of a TCP / IP header is performed, and a packet is transmitted to the communication processing unit 401. At this time, as an example, the source IP address of the packet is set to the same IP address as the server, and the source port number is also set to the same port number as the server (the destination port number of the packet transmitted by the communication terminal). Therefore, from the viewpoint of STA, it looks as if it is communicating with the server 407. The communication processing unit 401 executes the processing of the MAC layer for this packet, the transmission unit 402 executes the processing of the physical layer, and the like, and the packet addressed to the STA is transmitted from the antennas 42A to 42D.

By such an operation, the frequently accessed data responds based on the cache data stored in the memory 406, and the traffic between the server 407 and the base station 400 can be reduced. The operation of the network processing unit 404 is not limited to the operation of the present embodiment. Any general cache proxy that fetches data from server 407 instead of STA, caches the data in memory 406, and responds to data transfer requests for the same data from the cached data in memory 406. For example, there is no problem with another operation.

The base station (access point) of the present embodiment can be applied as the base station of the first embodiment. The transmission of frames, data or packets used in the first embodiment described above may be performed using the cached data stored in the memory 406. Further, the information obtained by the frame, data or packet received by the base station of the first embodiment may be cached in the memory 406. In the first embodiment, the frame transmitted by the access point may include cached data or information based on the data.
The information based on the data may be, for example, information on the presence or absence of data addressed to the terminal, information on the size of the data, and information on the size of the packet required for transmitting the data. It may also be information such as a modulation method required for data transmission.

In the present embodiment, the base station having a cache function has been described, but a terminal (STA) having a cache function can also be realized with the same block configuration as in FIG. 23. The terminal referred to here is a terminal of a non-base station (as described above, a base station is also a form of a wireless communication terminal). In this case, the wired I / F 405 may be omitted. The transmission of frames, data or packets by the terminal in the first embodiment described above may be executed using the cached data stored in the memory 406. Further, the information obtained by the frame, data or packet received by the terminal of the first embodiment may be cached in the memory 406. In the first embodiment, the frame transmitted by the terminal may include cached data or information based on the data. The information based on the data may be, for example, information on the presence or absence of data to be transmitted, information on the size of the data, and information on the size of the packet required for transmitting the data. It may also be information such as a modulation method required for data transmission.

(Third embodiment)
FIG. 24 shows an example of the overall configuration of a terminal (a terminal of a non-base station) or a base station. This configuration example is an example, and the present embodiment is not limited thereto. The terminal or base station includes one or more antennas 1 to n (n is an integer of 1 or more), a wireless LAN module 148, and a host system 149. The wireless LAN module 148 corresponds to the wireless communication device according to the first embodiment. The wireless LAN module 148 includes a host interface, which is connected to the host system 149. In addition to being connected to the host system 149 via a connection cable, it may be directly connected to the host system 149. Further, the wireless LAN module 148 can be mounted on the board by solder or the like and connected to the host system 149 via the wiring of the board. The host system 149 communicates with an external device by using the wireless LAN module 148 and the antennas 1 to n according to an arbitrary communication protocol. The communication protocol may include TCP / IP and a higher layer protocol. Alternatively, TCP / IP may be mounted on the wireless LAN module 148, and the host system 149 may execute only the protocol of the upper layer thereof. In this case, the configuration of the host system 149 can be simplified. This terminal is, for example, a mobile terminal, TV, digital camera, wearable device, tablet, smartphone, game device, network storage device, monitor, digital audio player, Web camera, video camera, project, navigation system, external adapter, internal It may be an adapter, a set-top box, a gateway, a printer server, a mobile access point, a router, an enterprise / service provider access point, a portable device, a handheld device, a car, or the like.
In addition to IEEE802.11, the wireless LAN module 148 (or wireless communication device) may have functions of other wireless communication standards such as LTE (Long Term Evolution) or LTE-Advanced (standards for mobile phones). ..

FIG. 25 shows a hardware configuration example of the wireless LAN module. This configuration is applicable when the wireless communication device is mounted on either a non-base station terminal or a base station. That is, it can be applied as an example of a specific configuration of the wireless communication device shown in FIG. In this configuration example, the number of antennas is only one, but two or more antennas may be provided. In this case, a plurality of sets of a transmission system (216, 222 to 225), a reception system (217, 232 to 235), a PLL 242, a crystal oscillator (reference signal source) 243, and a switch 245 are arranged corresponding to each antenna. Each set may be connected to the control circuit 212. The PLL 242, the crystal oscillator 243, or both correspond to the oscillator according to this embodiment.

The wireless LAN module (wireless communication device) is a baseband IC (Integrated).
It includes a Circuit) 211, an RF (Radio Frequency) IC 221, a balun 225, a switch 245, and an antenna 247.

The baseband IC 211 includes a baseband circuit (control circuit) 212, a memory 213, a host interface 214, a CPU 215, a DAC (Digital to Analog Controller) 216, and an ADC (Analog to Digital Converter) 217.

The baseband IC 211 and the RF IC 221 may be formed on the same substrate. Further, the baseband IC 211 and the RF IC 221 may be configured by one chip. DAC216 and / or ADC217 may be located in the RF IC 221 or in another IC. Further, the memory 213 and / or the CPU 215 may be arranged in an IC different from the baseband IC.

The memory 213 stores data to be transferred to and from the host system. Further, the memory 213 stores information notified to the terminal or the base station, information notified from the terminal or the base station, or both of them. Further, the memory 213 may store a program necessary for executing the CPU 215 and may be used as a work area when the CPU 215 executes the program. The memory 213 may be a volatile memory such as SRAM or DRAM, or a non-volatile memory such as NAND or MRAM.

The host interface 214 is an interface for connecting to the host system. The interface may be anything such as UART, SPI, SDIO, USB, PCI Express and the like.

The CPU 215 is a processor that controls the baseband circuit 212 by executing a program. The baseband circuit 212 mainly processes the MAC layer and the physical layer. The baseband circuit 212, CPU 215, or both correspond to a communication control device that controls communication, or a control unit that controls communication.

At least one of the baseband circuit 212 and the CPU 215 includes a clock generation unit that generates a clock, and the internal time may be managed by the clock generated by the clock generation unit.

The baseband circuit 212 performs physical header addition, coding, encryption, modulation processing, etc. on the frame to be transmitted as physical layer processing, for example, two types of digital baseband signals (hereinafter, digital I signal and digital Q). Signal) is generated.

The DAC 216 performs DA conversion of the signal input from the baseband circuit 212. More specifically, the DAC 216 converts a digital I signal into an analog I signal and a digital Q signal into an analog Q signal. It should be noted that there may be a case where the signal of one system is transmitted as it is without quadrature modulation. When a plurality of antennas are provided and transmission signals of one system or a plurality of systems are distributed and transmitted by the number of antennas, a number of DACs or the like corresponding to the number of antennas may be provided.

The RF IC 221 is, for example, an RF analog IC, a high frequency IC, or both of them. The RF IC 221 includes a filter 222, a mixer 223, a preamplifier (PA) 224, a PLL (Phase Locked Loop) 242, a low noise amplifier (LNA), a balun 235, a mixer 233, and a filter 232.
Some of these elements may be located on baseband IC211 or another IC. The filters 222 and 232 may be a band pass filter or a low pass filter.

The filter 222 extracts a signal in a desired band from each of the analog I signal and the analog Q signal input from the DAC 216. The PLL 242 uses an oscillating signal input from the crystal oscillator 243, and divides or multiplies the oscillating signal, or both, to generate a signal having a constant frequency synchronized with the phase of the input signal. The PLL 242 includes a VCO (Voltage Controlled Oscillator), and obtains a signal having the constant frequency by performing feedback control using the VCO based on the oscillation signal input from the crystal oscillator 243. The generated constant frequency signal is input to the mixer 223 and the mixer 233. The PLL 242 corresponds to an example of an oscillator that generates a signal having a constant frequency.

The mixer 223 up-converts the analog I signal and the analog Q signal that have passed through the filter 222 to a radio frequency by using a signal having a constant frequency supplied from the PLL 242. The preamplifier (PA) amplifies the analog I signal and analog Q signal of the radio frequency generated by the mixer 223 to the desired output power. The balun 225 is a converter for converting a balanced signal (differential signal) into an unbalanced signal (single-ended signal). The RF IC 221 handles balanced signals, but since the unbalanced signals are handled from the output of the RF IC 221 to the antenna 247, the balun 225 performs these signal conversions.

The switch 245 is connected to the transmitting side balun 225 at the time of transmission, and is connected to the receiving side balun 234 or RF IC221 at the time of receiving. The control of the switch 245 may be performed by the baseband IC211 or the RF IC221, or another circuit for controlling the switch 245 may exist, and the switch 245 may be controlled from the circuit.

The analog I signal and analog Q signal of the radio frequency amplified by the preamplifier 224 are balanced-unbalanced converted by the balun 225, and then radiated as radio waves from the antenna 247 into space.

The antenna 247 may be a chip antenna, an antenna formed by wiring on a printed circuit board, or an antenna formed by using a linear conductor element.

The LNA 234 in the RF IC 221 amplifies the signal received from the antenna 247 via the switch 245 to a level that can be demodulated while keeping the noise low. The balun 235 performs an unbalanced-equilibrium conversion of the signal amplified by the low noise amplifier (LNA) 234. The mixer 233 down-converts the received signal converted into the balanced signal by the balun 235 to the baseband using the signal of a constant frequency input from the PLL 242. More specifically, the mixer 233 has means for generating carriers that are 90 ° out of phase with each other based on the constant frequency signal input from the PLL 242, and the received signals converted by the balun 235 are 90 ° to each other. Orthogonal demodulation is performed by the out-of-phase carrier to generate an I (In-phase) signal having the same phase as the received signal and a Q (Quad-phase) signal having a phase delayed by 90 ° from the I (In-phase) signal. The filter 232 extracts a signal having a desired frequency component from these I signal and Q signal. The I signal and Q signal extracted by the filter 232 are output from the RF IC 221 after the gain is adjusted.

The ADC 217 in the baseband IC 211 AD-converts the input signal from the RF IC 221. More specifically, the ADC 217 converts the I signal into a digital I signal and the Q signal into a digital Q signal. In some cases, only one system of signals may be received without orthogonal demodulation.

When a plurality of antennas are provided, the number of ADCs may be provided according to the number of antennas. Based on the digital I signal and the digital Q signal, the baseband circuit 212 performs demodulation processing, error correction code processing, physical header processing, and other physical layer processing to obtain a frame. The baseband circuit 212 processes the MAC layer on the frame. If the baseband circuit 212 implements TCP / IP, the baseband circuit 212 can also be configured to perform TCP / IP processing.

Since the details of the processing of each part described above are obvious from the description of FIG. 1, duplicated description will be omitted.

(Fourth Embodiment)
26 (A) and 26 (B) are perspective views of the wireless terminal according to the fourth embodiment, respectively. The wireless terminal of FIG. 26 (A) is a notebook PC 301, and the wireless terminal of FIG. 26 (B) is a mobile terminal 321. The notebook PC 301 and the mobile terminal 321 are equipped with wireless communication devices 305 and 315, respectively. As the wireless communication devices 305 and 315, the wireless communication device mounted on the wireless terminal described above, the wireless communication device mounted on the base station 11, or both of them can be used. The wireless terminal equipped with the wireless communication device is not limited to a notebook PC or a mobile terminal. For example, TVs, digital cameras, wearable devices, tablets, smartphones, game devices, network storage devices, monitors, digital audio players, web cameras, video cameras, projects, navigation systems, external adapters, internal adapters, set-top boxes, gateways, etc. It can also be installed in printer servers, mobile access points, routers, enterprise / service provider access points, portable devices, handheld devices, automobiles, and the like.

Further, the wireless communication device mounted on the wireless terminal, the base station 11, or both of them can also be mounted on the memory card. FIG. 27 shows an example in which the wireless communication device is mounted on a memory card. The memory card 331 includes a wireless communication device 355 and a memory card main body 332. The memory card 331 utilizes a wireless communication device 335 for wireless communication with an external device (radio terminal, base station 11, or both). In addition, in FIG. 27, the description of other elements (for example, memory etc.) in the memory card 331 is omitted.

(Fifth Embodiment)
In the fifth embodiment, in addition to the configuration of the wireless communication device (base station wireless communication device, wireless terminal wireless communication device, or both) according to the above-described embodiment, the bus, the processor unit, and the external interface. It has a part. The processor unit and the external interface unit are connected to the external memory (buffer) via the bus. Firmware operates in the processor section. By including the firmware in the wireless communication device in this way, it is possible to easily change the function of the wireless communication device by rewriting the firmware. The processor unit on which the firmware operates may be a control unit or a processor that performs processing of the control unit according to the present embodiment, or may be another processor that performs processing related to function expansion or modification of the processing. good. The processor unit on which the firmware operates may be provided by the base station, the wireless terminal, or both of them according to the present embodiment. Alternatively, the processor unit may be provided with an integrated circuit in a wireless communication device mounted on a base station or an integrated circuit in a wireless communication device mounted on a wireless terminal.

(Sixth Embodiment)
A sixth embodiment includes a clock generator in addition to the configuration of the wireless communication device (base station wireless communication device, wireless terminal wireless communication device, or both) according to the above-described embodiment. The clock generator generates a clock and outputs the clock from the output terminal to the outside of the wireless communication device. In this way, the clock generated inside the wireless communication device is output to the outside, and the host side is operated by the clock output to the outside, so that the host side and the wireless communication device side can be operated in synchronization with each other. It will be possible.

(7th Embodiment)
In the seventh embodiment, in addition to the configuration of the wireless communication device (wireless communication device of the base station or wireless communication device of the wireless terminal) according to the above-described embodiment, the power supply unit, the power supply control unit, and the wireless power supply unit are provided. include. The power supply control unit is connected to the power supply unit and the wireless power supply unit, and controls to select the power supply to be supplied to the wireless communication device. In this way, by providing the wireless communication device with a power source, it is possible to perform a low power consumption operation in which the power source is controlled.

(8th Embodiment)
The eighth embodiment includes a SIM card in addition to the configuration of the wireless communication device according to the above-described embodiment. The SIM card is connected to, for example, a control unit in a wireless communication device. As described above, by providing the SIM card in the wireless communication device, the authentication process can be easily performed.

(9th embodiment)
The ninth embodiment includes a moving image compression / decompression unit in addition to the configuration of the wireless communication device according to the above-described embodiment. The moving image compression / decompression section is connected to the bus. As described above, by providing the moving image compression / decompression unit in the wireless communication device, it is possible to easily transmit the compressed moving image and decompress the received compressed moving image.

(10th Embodiment)
In the tenth embodiment, in addition to the configuration of the wireless communication device (the wireless communication device of the base station, the wireless communication device of the wireless terminal, or both) according to the above-described embodiment, the LED unit is included. The LED unit is connected to a transmitting unit, a receiving unit, a control unit, or a plurality of these. By providing the LED unit in the wireless communication device in this way, it is possible to easily notify the user of the operating state of the wireless communication device.

(11th Embodiment)
The eleventh embodiment includes a vibrator unit in addition to the configuration of the wireless communication device (the wireless communication device of the base station, the wireless communication device of the wireless terminal, or both) according to the above-described embodiment. The vibrator unit is connected to, for example, a control unit in a wireless communication device. By providing the vibrator unit in the wireless communication device in this way, it is possible to easily notify the user of the operating state of the wireless communication device.

(12th Embodiment)
A twelfth embodiment includes a display in addition to the configuration of the wireless communication device (base station wireless communication device, wireless terminal wireless communication device, or both) according to the above-described embodiment. The display may be connected to the control unit of the wireless communication device via a bus (not shown). By providing the display in this way and displaying the operating state of the wireless communication device on the display, it is possible to easily notify the user of the operating state of the wireless communication device.

(13th Embodiment)
In this embodiment, [1] a frame type in a wireless communication system, [2] a method of disconnecting a connection between wireless communication devices, [3] an access method of a wireless LAN system, and [4] a frame interval of a wireless LAN will be described.
[1] Frame type in communication system Generally, as described above, the frames handled on the wireless access protocol in a wireless communication system are roughly classified into three frames: a data frame, a management frame, and a control frame. It can be divided into types. These types are usually indicated by a header portion commonly provided between frames. As a display method of the frame type, one field may be capable of distinguishing three types, or a combination of two fields may be used to distinguish between the three types. In the IEEE802.11 standard, the frame type is identified by two fields, Type and Subtype in the Frame Control field in the frame header part of the MAC frame. The data frame, the management frame, and the control frame are roughly classified in the Type field, and the subtypes in the roughly classified frames, for example, the Beacon frame in the management frame, are identified in the Subtype field.

The management frame is a frame used for managing a physical communication link with another wireless communication device. For example, there are frames used for setting communication with other wireless communication devices, frames for releasing (that is, disconnecting) communication links, and frames related to power save operation in wireless communication devices. ..

A data frame is a frame in which data generated inside a wireless communication device is transmitted to another wireless communication device after a physical communication link is established with the other wireless communication device. The data is generated in the upper layer of the present embodiment, and is generated by, for example, a user operation.

The control frame is a frame used for control when transmitting / receiving (exchanged) a data frame with another wireless communication device. When the wireless communication device receives a data frame or a management frame, the response frame transmitted for confirmation of delivery belongs to the control frame. The response frame is, for example, an ACK frame or a BlockACK frame. The RTS frame and CTS frame are also control frames.

These three types of frames are processed as necessary in the physical layer and transmitted as physical packets via the antenna. In addition, the IEEE802.11 standard (the above-mentioned IEEE Std)
In (including extended standards such as 802.11ac-2013), there is an association process as one of the procedures for establishing a connection, but the Association Request frame and the ACTION Response frame used in it are the management frames, and the Association Request frame. Since the frame and the Association Response frame are unicast management frames, the receiving wireless communication terminal is requested to transmit the ACK frame which is the response frame, and this ACK frame is the control frame as described above.

[2] Method of disconnecting the connection between wireless communication devices There are an explicit method and an implicit method for disconnecting the connection (release). As an explicit method, one of the wireless communication devices having established a connection transmits a frame for disconnection. In the IEEE802.11 standard, the Delivery frame corresponds to this and is classified as a management frame. Normally, the wireless communication device on the side of transmitting the frame that disconnects the connection disconnects the connection when the frame is transmitted, and the wireless communication device on the side that receives the frame that disconnects the connection receives the frame. judge. After that, if it is a non-base station wireless communication terminal, it returns to the initial state in the communication phase, for example, the state of searching for a BSS to be connected. When a wireless communication base station disconnects from a certain wireless communication terminal, for example, if the wireless communication base station has a connection management table that manages wireless communication terminals that subscribe to its own BSS, the connection management is performed. Delete the information related to the wireless communication terminal from the table. For example, when an AID is assigned at the stage where a wireless communication base station permits a connection to each wireless communication terminal that subscribes to its own BSS in the association process, the holding information associated with the AID of the wireless communication terminal that disconnected the connection is used. May be deleted and the AID may be released so that it can be assigned to another newly subscribed wireless communication terminal.

On the other hand, as an implicit method, frame transmission (transmission of data frame and management frame, or transmission of response frame to the frame transmitted by the own device) is detected from the wireless communication device of the connection partner that has established the connection for a certain period of time. If not, the connection status is determined to be disconnected. There is such a method because, in the situation where the disconnection of the connection is determined as described above, the communication distance from the wireless communication device of the connection destination is long and the wireless signal cannot be received or decoded. This is because it is possible that the wireless link cannot be secured. That is, the reception of the frame that disconnects the connection cannot be expected.

A timer is used as a specific example of determining the disconnection by an implicit method. For example, when transmitting a data frame requesting a delivery confirmation response frame, a first timer (for example, a retransmission timer for a data frame) that limits the retransmission period of the frame is activated until the first timer expires (that is,). If the delivery confirmation response frame to the frame is not received (until the desired retransmission period elapses), retransmission is performed. The first timer is stopped when the delivery confirmation response frame to the frame is received.

On the other hand, when the first timer expires without receiving the delivery confirmation response frame, for example, it is confirmed whether the wireless communication device of the connection partner still exists (in the communication range) (in other words, whether the wireless link can be secured). At the same time, a second timer (for example, a retransmission timer for the management frame) that limits the retransmission period of the frame is activated. Similar to the first timer, the second timer retransmits if the delivery confirmation response frame to the frame is not received until the second timer expires, and when the second timer expires, it is determined that the connection is disconnected. .. When it is determined that the connection has been disconnected, a frame for disconnecting the connection may be transmitted.

Alternatively, when a frame is received from the wireless communication device of the connection partner, the third timer is activated, and each time a frame is newly received from the wireless communication device of the connection partner, the third timer is stopped and the frame is started again from the initial value. When the third timer expires, a management frame is sent to check whether the wireless communication device of the connection partner still exists (in other words, whether the wireless link is secured) as described above. At the same time, a second timer (for example, a retransmission timer for the management frame) that limits the retransmission period of the frame is activated. In this case as well, if the delivery confirmation response frame to the frame is not received until the second timer expires, the retransmission is performed, and when the second timer expires, it is determined that the connection is disconnected. In this case as well, the frame for disconnecting the connection may be transmitted at the stage when it is determined that the connection has been disconnected.
The latter management frame for confirming whether the wireless communication device of the connection partner still exists may be different from the management frame in the former case. Further, as the timer for limiting the retransmission of the management frame in the latter case, the same timer as in the former case is used here as the second timer, but a different timer may be used.

[3] Access method of wireless LAN system For example, there is a wireless LAN system that assumes communication or competition with a plurality of wireless communication devices. In the IEEE802.11 wireless LAN, CSMA / CA (Carrier Sense Multiple Access with Carrier Sense) is the basis of the access method. In the method of grasping the transmission of a certain wireless communication device and transmitting after a fixed time from the end of the transmission, the transmission is simultaneously performed by a plurality of wireless communication devices that have grasped the transmission of the wireless communication device, and as a result. , Radio signals collide and frame transmission fails. By grasping the transmission of a certain wireless communication device and waiting for a random time from the end of the transmission, the transmission by a plurality of wireless communication devices grasping the transmission of the wireless communication device is stochastically dispersed. Therefore, if there is only one wireless communication device obtained by subtracting the earliest time in the random time, the frame transmission of the wireless communication device is successful, and frame collision can be prevented. Since the acquisition of transmission rights is fair among a plurality of wireless communication devices based on a random value, the method adopting Carrier Availability is said to be a method suitable for sharing a wireless medium among a plurality of wireless communication devices. be able to.

[4] Wireless LAN frame interval The 802.11 wireless LAN frame interval will be described. The frame intervals used in the IEEE802.11 wireless LAN are distributed codeintion interface interface (DIFS), arbitration interframe space (AIFS), point codeination interface , Reduced interframe space (RIFS) and the like.

The definition of the frame interval is defined in the IEEE 802.11 wireless LAN as a continuous period in which the carrier sense idle should be confirmed and opened before transmission, and the exact period from the previous frame is not discussed. Therefore, in the description of the 802.11 wireless LAN system here, the definition is followed. In the 802.11 wireless LAN, the time to wait for random access based on CSMA / CA is the sum of the fixed time and the random time, and it can be said that this definition is used to clarify the fixed time.

DIFS and AIFS are frame intervals used when attempting to start frame exchange during a contention period that competes with other wireless communication devices based on CSMA / CA. DIFS is used when there is no distinction of priority by traffic type, and AIFS is used when priority by traffic type (TID) is provided.

Since the operations related to DIFS and AIFS are similar, they will be described mainly using AIFS below. In the 802.11 wireless LAN, access control including the start of frame exchange is performed at the MAC layer. Further, when QoS (Quality of Service) is supported when the data is passed from the upper layer, the traffic type is notified together with the data, and the data is classified into the priority at the time of access based on the traffic type. This access class is called an access category (AC). Therefore, the AIFS value is provided for each access category.

PIFS is a frame interval for allowing access with priority over other competing wireless communication devices, and has a shorter period than either DIFS or AIFS value. SIFS is a frame interval that can be used when transmitting a control frame of a response system or when frame exchange is continued in a burst after acquiring an access right once. EIFS is a frame interval that is activated when frame reception fails (it is determined that the received frame is an error).

RIFS is a frame interval that can be used when a plurality of frames are continuously transmitted to the same wireless communication device in a burst after the access right is once acquired, and while RIFS is used, the transmission partner's wireless communication device can be used. Does not request a response frame for.

Here, FIG. 28 shows an example of frame exchange during a conflict period based on random access in the 802.11 wireless LAN.

It is assumed that when a data frame (W_DATA1) transmission request is generated in a certain wireless communication device, the medium is recognized as busy medium as a result of carrier sense. In this case, the AIFS for a fixed time is vacated from the time when the carrier sense becomes idle, and then the data frame W_DATA1 is transmitted to the communication partner at a vacant random time (random backoff). If, as a result of the carrier sense, it is recognized that the medium is not busy, that is, the medium is idle, a fixed time AIFS is set from the time when the carrier sense is started, and the data frame W_DATA1 is communicated with the communication partner. Send to.

Random time is a pseudo-random integer derived from a uniform distribution between the Contention Window (CW) given as an integer from 0, multiplied by the slot time. Here, the CW multiplied by the slot time is called the CW time width.
The initial value of CW is given by CWmin, and each time it is retransmitted, the value of CW is increased until it reaches CWmax. Both CWmin and CWmax have values for each access category as in AIFS. In the wireless communication device of the transmission destination of W_DATA1, if the data frame is successfully received and the data frame is a frame requesting the transmission of the response frame, the occupation of the physical packet containing the data frame ends on the wireless medium. The response frame (W_ACK1) is transmitted after the SIFS time from the time point. When the wireless communication device that has transmitted W_DATA1 receives W_ACK1, it transmits the next frame (for example, W_DATA2) after SIFS time from the time when the physical packet containing W_ACK1 is occupied on the wireless medium within the transmission burst time limit. can do.

AIFS, DIFS, PIFS and AIFS are functions of SIFS and slot time, but SIFS and slot time are defined for each physical layer. In addition, parameters such as AIFS, CWmin, and CWmax for which values are provided for each access category can be set for each communication group (Basic Service Set (BSS) in the IEEE802.11 wireless LAN), but default values are set. ..

For example, in the standardization of 802.11ac, SIFS is 16 μs and slot time is 9 μs, so that PIFS is 25 μs, DIFS is 34 μs, and the default value of the frame interval of access category BACKGROUND (AC_BK) in AIFS is 79 μs. The default frame spacing of BEST EFFORT (AC_BE) is 43 μs, the default frame spacing of VIDEO (AC_VI) and VOICE (AC_VO) is 34 μs, and the default values of CWmin and CWmax are 31 and 1023 for AC_BK and AC_BE, respectively. , AC_VI is 15 and 31, and AC_VO is 7 and 15. Note that EIFFS is basically the sum of SIFS and DIFS and the time length of the response frame when transmitting at the slowest essential physical rate. In a wireless communication device that can efficiently take EIFS, the occupancy time length of the physical packet carrying the response frame to the physical packet that activated EIFS can be estimated, and the sum of SIFS, DIFS, and the estimated time can be used. can.

The frame described in each embodiment may refer to an IEEE802.11 standard or a compliant standard such as Null Data Packet, which is called a packet.

Further, the frames transmitted by the plurality of terminals in multiplex may be frames having different contents or frames having the same contents. As a general expression, when it is expressed that a plurality of terminals transmit or receive the Xth frame, the contents of these Xth frames may be the same or different. X is an arbitrary value.

The terms used in this embodiment should be broadly interpreted. For example, the term "processor" may include general purpose processors, central processing units (CPUs), microprocessors, digital signal processors (DSPs), controllers, microcontrollers, state machines, and the like. In some circumstances, the "processor" may refer to an application-specific integrated circuit, field programmable gate array (FPGA), programmable logic circuit (PLD), and the like. "Processor" may refer to a combination of processing devices such as multiple microprocessors, a combination of DSPs and microprocessors, and one or more microprocessors that work with a DSP core.

As another example, the term "memory" may include any electronic component capable of storing electronic information. "Memory" includes random access memory (RAM), read-only memory (ROM), programmable read-only memory (PROM), erasable programmable read-only memory (EPROM), electrically erasable PROM (EEPROM), and non-volatile. It may refer to random access memory (NVRAM), flash memory, magnetic or optical data storage, which can be read by a processor. If the processor reads and writes information to the memory, or both, then the memory can be said to communicate electrically with the processor. The memory may be integrated into the processor, again, it can be said that the memory is electrically communicating with the processor. Further, the circuit may be a plurality of circuits arranged on a single chip, or may be one or more circuits distributed on a plurality of chips or a plurality of devices.

Further, in the present specification, "at least one of a, b and c" is referred to as a, b, c, ab, and so on.
Includes not only combinations of ac, bc, abc, but also multiple combinations of the same elements such as aa, abb, aa-b-bc-c. It is an expression. Further, it is an expression that covers a configuration including elements other than a, b, and c, such as a combination of abcd.

It should be noted that the present invention is not limited to the above embodiment as it is, and at the implementation stage, the components can be modified and embodied within a range that does not deviate from the gist thereof. In addition, various inventions can be formed by an appropriate combination of the plurality of components disclosed in the above-described embodiment. For example, some components may be removed from all the components shown in the embodiments. In addition, components across different embodiments may be combined as appropriate.

The following is a description of the scope of claims at the time of filing the patent application of the original application.
[Item 1]
With at least one antenna,
A receiver that is coupled to the antenna and receives a frame,
A transmitter that is coupled to the antenna and transmits a frame,
A communication processing unit coupled to the receiving unit and the transmitting unit,
A network processing unit that is coupled to the communication processing unit, transmits data to the communication processing unit, and receives data from another device.
A memory that is coupled to the network processing unit and caches the first data,
Equipped with
The transmitter transmits a first frame containing information specifying a plurality of frequency components via the antenna.
The communication processing unit determines whether or not the second frame has been received for each of the plurality of frequency components, and determines whether or not the second frame has been received.
The transmitter includes a third information regarding a first value range according to the number of frequency components received by the second frame, which is used for determining whether or not the response to the first frame is possible. The frame is transmitted via the antenna and
The first frame or the third frame includes the first data cached in the memory or information based on the first data.
Wireless communication terminal.
[Item 2]
The wireless communication terminal according to item 1, wherein the first information includes an instruction to set the size of the first value range to an initial value.
[Item 3]
The wireless communication terminal according to item 2, wherein the initial value is an intermediate value between a minimum value and a maximum value in the first value range.
[Item 4]
The wireless communication terminal according to item 1, wherein the first information includes an instruction to set the size of the first value range to the maximum value.
[Item 5]
The wireless communication terminal according to any one of items 1 to 4, wherein the first information includes information for designating at least one of a minimum value and a maximum value in the first value range.
[Item 6]
The wireless communication terminal according to item 1, wherein the first information includes information indicating an adjustment amount of the first value range.
[Item 7]
The third frame includes a first field for notification to a terminal for which the second frame has not been received.
The wireless communication terminal according to any one of items 1 to 6 set in the first field in the third frame.
[Item 8]
The third frame includes a second field for notification to the terminal in which the second frame is received.
The wireless communication terminal according to any one of items 1 to 7 set in the second field in the third frame.
[Item 9]
The communication processing unit adjusts the number of frequency components specified in the first frame to be transmitted next according to the number of frequency components received by the second frame. Any one of items 1 to 8. The wireless communication terminal described in.
[Item 10]
The third frame includes a third field for notification to the terminal in which the second frame is received.
The communication processing unit provides second information in the third frame, which specifies the number of times the first frame is received waiting for a response to the first frame or the time for waiting for a response to the first frame. 3 The wireless communication terminal according to any one of items 1 to 9 to be set in the field.
[Item 11]
The communication processing unit measures the communication quality of the second frame and determines the communication quality.
The third frame includes the identifier of the terminal that transmitted the second frame whose communication quality meets the standard, and does not include the identifier of the terminal that transmitted the second frame whose communication quality does not meet the standard. The wireless communication terminal according to any one of 10.
[Item 12]
The first frame specifies that at least one second frequency component designated for use by a particular terminal and the plurality of frequency components are allowed to be used by any terminal. Including information,
The wireless communication terminal according to any one of items 1 to 11.
[Item 13]
The wireless communication terminal according to any one of items 1 to 12, which controls communication in accordance with the 802.11 standard.
[Item 14]
The wireless communication terminal according to any one of items 1 to 13, which is a base station.
[Item 15]
It is a wireless communication method using a wireless communication terminal.
Cache the first data in memory
Send the first frame containing information that specifies multiple frequency components,
It is determined whether the second frame is received in each of the plurality of frequency components, and it is determined.
A third frame containing the first information regarding the first value range according to the number of the frequency components received in the second frame, which is used for determining whether or not the response to the first frame is possible, is transmitted.
The first frame or the third frame is a wireless communication method including information based on the first data or the first data cached in the memory.

Claims (3)

OFDMA (Orthogonal Frequency Division Multiple Access) A transmitter that transmits the first frame, which is a trigger frame containing information that specifies multiple frequency components for random access, to multiple terminals.
A receiver that receives at least one second frame transmitted via at least one of the plurality of frequency components specified in the information of the first frame.
A control unit for managing the minimum value and the maximum value used for determining the first value range is provided.
The first value range is used to determine a first value used to determine whether transmission is performed on one of the plurality of frequency components, and the first value is the first value. Randomly selected from the value range of
The minimum value and the maximum value are used by the terminal that manages the result state of the success or failure of the transmission of the second frame.
The transmission unit transmits a third frame containing the minimum value and the maximum value, and transmits the third frame.
The transmitter transmits a fourth frame, which is a trigger frame containing information specifying a plurality of frequency components for the OFDMA random access.
The terminal that has received the fourth frame selects from the first value range updated based on the minimum and maximum values and the result state of success or failure of transmission of the second frame. A wireless communication device in which a transmission right for responding to the fourth frame is acquired based on the second value. The wireless communication device according to claim 1, further comprising at least one antenna. OFDMA (Orthogonal Frequency Division Multiple Access) A first frame, which is a trigger frame containing information that specifies multiple frequency components for random access, is transmitted to multiple terminals.
Receives at least one second frame transmitted via at least one of the plurality of frequency components specified in the information of the first frame.
Manages the minimum and maximum values used to determine the first value range
The first value range is used to determine a first value used to determine whether transmission is performed on one of the plurality of frequency components, and the first value is the first value. Randomly selected from the value range of
The minimum value and the maximum value are used by the terminal that manages the result state of the success or failure of the transmission of the second frame.
A third frame containing the minimum value and the maximum value is transmitted, and the third frame is transmitted.
A fourth frame, which is a trigger frame containing information specifying a plurality of frequency components for OFDMA random access, is transmitted.
The terminal that has received the fourth frame selects from the first value range updated based on the minimum and maximum values and the result state of success or failure of transmission of the second frame. A wireless communication method in which a transmission right for responding to the fourth frame is acquired based on the second value.

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