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WO2018151432A1 - Procédé de transmission ou de réception d'une trame de radio de réveil dans un système lan sans fil, et appareil associé - Google Patents

Procédé de transmission ou de réception d'une trame de radio de réveil dans un système lan sans fil, et appareil associé Download PDF

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Publication number
WO2018151432A1
WO2018151432A1 PCT/KR2018/001040 KR2018001040W WO2018151432A1 WO 2018151432 A1 WO2018151432 A1 WO 2018151432A1 KR 2018001040 W KR2018001040 W KR 2018001040W WO 2018151432 A1 WO2018151432 A1 WO 2018151432A1
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WIPO (PCT)
Prior art keywords
wur
sequence
sta
symbol
frame
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Ceased
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PCT/KR2018/001040
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English (en)
Korean (ko)
Inventor
임동국
박은성
최진수
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LG Electronics Inc
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LG Electronics Inc
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    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L27/00—Modulated-carrier systems
    • H04L27/02—Amplitude-modulated carrier systems, e.g. using on-off keying; Single sideband or vestigial sideband modulation
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L27/00—Modulated-carrier systems
    • H04L27/26—Systems using multi-frequency codes
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04W—WIRELESS COMMUNICATION NETWORKS
    • H04W52/00—Power management, e.g. Transmission Power Control [TPC] or power classes
    • H04W52/02—Power saving arrangements
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02D—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN INFORMATION AND COMMUNICATION TECHNOLOGIES [ICT], I.E. INFORMATION AND COMMUNICATION TECHNOLOGIES AIMING AT THE REDUCTION OF THEIR OWN ENERGY USE
    • Y02D30/00—Reducing energy consumption in communication networks
    • Y02D30/70—Reducing energy consumption in communication networks in wireless communication networks

Definitions

  • the present invention relates to a wireless LAN system, and more particularly, to a method and apparatus for transmitting or receiving a WUR frame through a wake up radio (WUR) to wake up a primary connectivity radio (PCR).
  • WUR wake up radio
  • PCR primary connectivity radio
  • IEEE 802.11a and b are described in 2.4. Using unlicensed band at GHz or 5 GHz, IEEE 802.11b provides a transmission rate of 11 Mbps and IEEE 802.11a provides a transmission rate of 54 Mbps.
  • IEEE 802.11g applies orthogonal frequency-division multiplexing (OFDM) at 2.4 GHz to provide a transmission rate of 54 Mbps.
  • IEEE 802.11n applies multiple input multiple output OFDM (MIMO-OFDM) to provide a transmission rate of 300 Mbps for four spatial streams. IEEE 802.11n supports channel bandwidths up to 40 MHz, in this case providing a transmission rate of 600 Mbps.
  • the WLAN standard uses a maximum of 160MHz bandwidth, supports eight spatial streams, and supports IEEE 802.11ax standard through an IEEE 802.11ac standard supporting a speed of up to 1Gbit / s.
  • An object of the present invention is to provide a method and apparatus therefor for more accurately and efficiently transmitting or receiving a WUR frame including a WUR preamble.
  • the present invention is not limited to the above-described technical problem and other technical problems can be inferred from the embodiments of the present invention.
  • the access point (AP) transmits a WUR (wake up radio) frame, in the time domain to the PN (pseudo noise) sequence Determining on / off of the plurality of on-off keying (OOK) symbols to be included in the WUR preamble based on the; Mapping the PN sequence to tones of each on symbol of the plurality of OOK symbols in a frequency domain; And transmitting a WUR frame including the WUR preamble, wherein the length of the PN sequence, the number of the plurality of OOK symbols, and the number of tones to which the WUR preamble is transmitted are equally set.
  • a binary sequence including a plurality of bits, and a OOK symbol corresponding to a bit having a value of 1 in the binary sequence may be determined as an on symbol.
  • an access point (AP) for transmitting a wake up radio (WUR) frame includes a plurality of on-off keyings (OOKs) to be included in a WUR preamble based on a pseudo noise (PN) sequence in a time domain.
  • a processor that determines on / off of symbols and maps the PN sequence to tones of each on symbol of the plurality of OOK symbols in a frequency domain;
  • a transmitter for transmitting a WUR frame including the WUR preamble under control of the processor, wherein the length of the PN sequence, the number of the plurality of OOK symbols, and the number of tones to which the WUR preamble is transmitted are the same.
  • the PN sequence is set to be a binary sequence including a plurality of bits, and a OOK symbol corresponding to a bit having a value of 1 in the binary sequence may be determined as an on symbol.
  • the OOK symbol corresponding to the bit having a zero value in the binary sequence is determined as an off symbol, and all zeros may be mapped to the tones of the off symbol.
  • the WUR preamble having the plurality of OOK symbols with the PN sequence or zero mapped in the frequency domain according to on / off may be transmitted through an orthogonal frequency divisional multiplex (OFDM) transmitter.
  • OFDM orthogonal frequency divisional multiplex
  • the PN sequence may be set differently for each BSS based on the identifier of the AP or the basic service set (BSS) color, or the PN sequence may be set differently for each STA based on an association identifier (API) or a partial AID (PAID). Can be.
  • API association identifier
  • PAID partial AID
  • the PN sequence may be assigned through an association procedure or a capability negotiation procedure on a primary connectivity radio (PCR).
  • PCR primary connectivity radio
  • the WUR frame may further include at least one measurement symbol that provides a criterion for the WUR STA receiving the WUR frame to determine on / off of each of the plurality of OOK symbols.
  • the at least one measurement symbol is all set to an on symbol and may be located before the WUR preamble.
  • the WUR preamble be generated by using the same PN sequence in the time domain and the frequency domain, but also time synchronization for the WUR frame can be performed accurately and efficiently.
  • FIG. 1 is a diagram illustrating an example of a configuration of a WLAN system.
  • FIG. 2 is a diagram illustrating another example of a configuration of a WLAN system.
  • 5 is a diagram for explaining hidden nodes and exposed nodes.
  • FIG. 6 is a diagram for explaining an RTS and a CTS.
  • FIG. 10 is a diagram for explaining an example of a frame structure used in an IEEE 802.11 system.
  • FIG. 11 is a diagram illustrating a WUR receiver usable in a WLAN system (e.g., 802.11).
  • FIG. 13 shows an example of a WUR packet.
  • FIG. 14 illustrates a waveform for a WUR packet.
  • FIG. 15 illustrates a WUR packet generated using an OFDM transmitter of a wireless LAN.
  • 16 illustrates the structure of a WUR receiver.
  • Figure 17 shows the frame format of the WUR signal to wake up the PCR.
  • FIG. 18 illustrates a WUR frame according to another embodiment of the present invention.
  • FIG. 20 shows a flow of a WUR frame transmission and reception method according to an embodiment of the present invention.
  • 21 is a view for explaining an apparatus according to an embodiment of the present invention.
  • the following description relates to a method and an apparatus therefor for efficiently utilizing a channel having a wide band in a WLAN system.
  • a WLAN system to which the present invention is applied will be described in detail.
  • the WLAN system includes one or more basic service sets (BSSs).
  • BSS is a set of stations (STAs) that can successfully synchronize and communicate with each other.
  • FIG. 2 is a diagram illustrating another example of a configuration of a WLAN system.
  • the DS is a mechanism for connecting a plurality of APs.
  • the DS is not necessarily a network, and there is no limitation on the form if it can provide a predetermined distribution service.
  • the DS may be a wireless network such as a mesh network or a physical structure that connects APs to each other.
  • the aforementioned entities interact in a variety of ways.
  • entities can interact by exchanging GET / SET primitives.
  • a primitive means a set of elements or parameters related to a particular purpose.
  • the XX-GET.request primitive is used to request the value of a given MIB attribute (management information based attribute information).
  • the XX-GET.confirm primitive is used to return the appropriate MIB attribute information value if the Status is "Success", otherwise it is used to return an error indication in the Status field.
  • the XX-SET.request primitive is used to request that the indicated MIB attribute be set to a given value. If the MIB attribute means a specific operation, this is to request that the operation be performed.
  • the XX-SET.confirm primitive confirms that the indicated MIB attribute is set to the requested value when status is "success", otherwise it is used to return an error condition in the status field. If the MIB attribute means a specific operation, this confirms that the operation has been performed.
  • FIG. 3 is a diagram illustrating a general link setup process.
  • the STA may perform a network discovery operation.
  • the network discovery operation may include a scanning operation of the STA. That is, in order for the STA to access the network, the STA must find a network that can participate. The STA must identify a compatible network before joining the wireless network. A network identification process existing in a specific area is called scanning.
  • the STA performing scanning transmits a probe request frame and waits for a response to discover which AP exists in the vicinity while moving channels.
  • the responder transmits a probe response frame to the STA that transmits the probe request frame in response to the probe request frame.
  • the responder may be an STA that last transmitted a beacon frame in the BSS of the channel being scanned.
  • the AP transmits a beacon frame, so the AP becomes a responder.
  • the responder is not constant.
  • an STA that transmits a probe request frame on channel 1 and receives a probe response frame on channel 1 stores the BSS-related information included in the received probe response frame and stores the next channel (eg, number 2).
  • Channel to perform scanning (i.e., probe request / response transmission and reception on channel 2) in the same manner.
  • the scanning operation may be performed by a passive scanning method.
  • passive scanning the STA performing scanning waits for a beacon frame while moving channels.
  • the beacon frame is one of management frames in IEEE 802.11.
  • the beacon frame is notified of the existence of a wireless network and is periodically transmitted to allow the STA performing scanning to find the wireless network and participate in the wireless network.
  • the AP periodically transmits a beacon frame
  • the IBSS STAs in the IBSS rotate and transmit a beacon frame.
  • the STA that performs the scanning receives the beacon frame, the STA stores the information on the BSS included in the beacon frame and records beacon frame information in each channel while moving to another channel.
  • the STA may store BSS related information included in the received beacon frame, move to the next channel, and perform scanning on the next channel in the same manner.
  • active scanning has the advantage of less delay and power consumption than passive scanning.
  • step S520 After the STA discovers the network, an authentication process may be performed in step S520.
  • This authentication process may be referred to as a first authentication process in order to clearly distinguish from the security setup operation of step S540 described later.
  • the STA may send an authentication request frame to the AP.
  • the AP may determine whether to allow authentication for the corresponding STA based on the information included in the received authentication request frame.
  • the AP may provide a result of the authentication process to the STA through an authentication response frame.
  • the association process includes a process in which the STA transmits an association request frame to the AP, and in response thereto, the AP transmits an association response frame to the STA.
  • the association request frame may include information related to various capabilities, beacon listening interval, service set identifier (SSID), supported rates, supported channels, RSN, mobility domain. Information about supported operating classes, TIM Broadcast Indication Map Broadcast request, interworking service capability, and the like.
  • a security setup process may be performed at step S540.
  • the security setup process of step S540 may be referred to as an authentication process through a Robust Security Network Association (RSNA) request / response.
  • the authentication process of step S520 is called a first authentication process, and the security setup process of step S540 is performed. It may also be referred to simply as the authentication process.
  • RSNA Robust Security Network Association
  • the security setup process of step S540 may include, for example, performing a private key setup through 4-way handshaking through an Extensible Authentication Protocol over LAN (EAPOL) frame. .
  • the security setup process may be performed according to a security scheme not defined in the IEEE 802.11 standard.
  • a basic access mechanism of MAC is a carrier sense multiple access with collision avoidance (CSMA / CA) mechanism.
  • the CSMA / CA mechanism is also called the Distributed Coordination Function (DCF) of the IEEE 802.11 MAC. It basically employs a "listen before talk" access mechanism.
  • the AP and / or STA may sense a radio channel or medium during a predetermined time period (e.g., during a DCF Inter-Frame Space (DIFS), before starting transmission.
  • DIFS DCF Inter-Frame Space
  • HCF hybrid coordination function
  • the PCF refers to a polling-based synchronous access scheme in which polling is performed periodically so that all receiving APs and / or STAs can receive data frames.
  • the HCF has an Enhanced Distributed Channel Access (EDCA) and an HCF Controlled Channel Access (HCCA).
  • EDCA is a competition based approach for providers to provide data frames to multiple users, and HCCA uses a non-competition based channel access scheme using a polling mechanism.
  • the HCF includes a media access mechanism for improving the quality of service (QoS) of the WLAN, and can transmit QoS data in both a contention period (CP) and a contention free period (CFP).
  • QoS quality of service
  • FIG. 4 is a diagram for describing a backoff process.
  • the random backoff count has a packet number value and may be determined as one of values ranging from 0 to CW.
  • CW is a contention window parameter value.
  • the CW parameter is given CWmin as an initial value, but may take a double value in case of transmission failure (eg, when an ACK for a transmitted frame is not received).
  • the STA continues to monitor the medium while counting down the backoff slots according to the determined backoff count value. If the medium is monitored as occupied, the countdown stops and waits; if the medium is idle, it resumes the remaining countdown.
  • the STA3 may confirm that the medium is idle as much as DIFS and transmit the frame immediately. Meanwhile, the remaining STAs monitor and wait for the medium to be busy. In the meantime, data may also be transmitted in each of STA1, STA2, and STA5, and each STA waits for DIFS when the medium is monitored idle, and then counts down the backoff slot according to a random backoff count value selected by the STA. Can be performed. In the example of FIG. 4, STA2 selects the smallest backoff count value, and STA1 selects the largest backoff count value.
  • the remaining backoff time of the STA5 is shorter than the remaining backoff time of the STA1 at the time when the STA2 finishes the backoff count and starts the frame transmission.
  • STA1 and STA5 stop counting for a while and wait for STA2 to occupy the medium.
  • the STA1 and the STA5 resume the stopped backoff count after waiting for DIFS. That is, the frame transmission can be started after counting down the remaining backoff slots by the remaining backoff time. Since the remaining backoff time of the STA5 is shorter than that of the STA1, the STA5 starts frame transmission. Meanwhile, while STA2 occupies the medium, data to be transmitted may also occur in STA4.
  • the STA4 waits for DIFS, performs a countdown according to a random backoff count value selected by the STA4, and starts frame transmission.
  • the remaining backoff time of STA5 coincides with an arbitrary backoff count value of STA4.
  • a collision may occur between STA4 and STA5. If a collision occurs, neither STA4 nor STA5 receive an ACK, and thus data transmission fails. In this case, STA4 and STA5 may double the CW value, select a random backoff count value, and perform a countdown.
  • the STA1 waits while the medium is occupied due to transmission of the STA4 and STA5, waits for DIFS when the medium is idle, and starts frame transmission after the remaining backoff time passes.
  • the CSMA / CA mechanism includes virtual carrier sensing in addition to physical carrier sensing in which the AP and / or STA directly sense the medium.
  • Virtual carrier sensing is intended to compensate for problems that may occur in media access, such as a hidden node problem.
  • the MAC of the WLAN system may use a network allocation vector (NAV).
  • the NAV is a value in which an AP and / or STA currently using or authorized to use a medium instructs another AP and / or STA how long to remain until the medium becomes available.
  • the value set to NAV corresponds to a period in which the medium is scheduled to be used by the AP and / or STA transmitting the corresponding frame, and the STA receiving the NAV value is prohibited from accessing the medium during the period.
  • the NAV may be set, for example, according to the value of the "duration" field of the MAC header of the frame.
  • 5 is a diagram for explaining hidden nodes and exposed nodes.
  • 5A illustrates an example of a hidden node, in which STA A and STA B are in communication and STA C has information to transmit.
  • STA A may be transmitting information to STA B, it may be determined that the medium is idle when STA C performs carrier sensing before sending data to STA B. This is because transmission of STA A (ie, media occupation) may not be sensed at the location of STA C.
  • STA B since STA B receives the information of STA A and STA C at the same time, a collision occurs.
  • STA A may be referred to as a hidden node of STA C.
  • FIG. 5B is an example of an exposed node
  • STA B is a case in which STA C has information to be transmitted from STA D while transmitting data to STA A.
  • FIG. 5B is an example of an exposed node
  • STA C is a case in which STA C has information to be transmitted from STA D while transmitting data to STA A.
  • FIG. 5B when STA C performs carrier sensing, it may be determined that the medium is occupied by the transmission of STA B. Accordingly, since STA C is sensed as a medium occupancy state even if there is information to be transmitted to STA D, it must wait until the medium becomes idle. However, since STA A is actually outside the transmission range of STA C, transmission from STA C and transmission from STA B may not collide with STA A's point of view, so STA C is unnecessary until STA B stops transmitting. To wait. At this time, STA C may be referred to as an exposed node of STA B.
  • the WLAN system channel sensing must be performed before the STA performs transmission and reception, and always sensing the channel causes continuous power consumption of the STA.
  • the power consumption in the receive state is not significantly different from the power consumption in the transmit state, and maintaining the receive state is also a great burden for the power limited STA (ie, operated by a battery). Therefore, if the STA maintains the reception standby state in order to continuously sense the channel, it inefficiently consumes power without any particular advantage in terms of WLAN throughput.
  • the WLAN system supports a power management (PM) mode of the STA.
  • PM power management
  • the power management mode of the STA is divided into an active mode and a power save (PS) mode.
  • the STA basically operates in the active mode.
  • the STA operating in the active mode maintains an awake state.
  • the awake state is a state in which normal operation such as frame transmission and reception or channel scanning is possible.
  • the STA operating in the PS mode operates by switching between a sleep state (or a doze state) and an awake state.
  • the STA operating in the sleep state operates at the minimum power, and does not perform frame scanning as well as channel scanning.
  • the AP may transmit a beacon frame to STAs in the BSS at regular intervals.
  • the beacon frame may include a traffic indication map (TIM) information element.
  • the TIM information element may include information indicating that the AP has buffered traffic for STAs associated with the AP and transmits a frame.
  • the TIM element includes a TIM used to inform unicast frames and a delivery traffic indication map (DTIM) used to inform multicast or broadcast frames.
  • DTIM delivery traffic indication map
  • 7 to 9 are diagrams for explaining in detail the operation of the STA receiving the TIM.
  • the STA may switch from the sleep state to the awake state to receive a beacon frame including the TIM from the AP, interpret the received TIM element, and know that there is buffered traffic to be transmitted to the AP. .
  • the STA may transmit a PS-Poll frame to request an AP to transmit a data frame.
  • the AP may transmit the frame to the STA.
  • the STA may receive a data frame and transmit an acknowledgment (ACK) frame thereto to the AP.
  • the STA may then go back to sleep.
  • ACK acknowledgment
  • the AP may operate according to an immediate response method of transmitting a data frame after a predetermined time (for example, a short inter-frame space (SIFS)) after receiving a PS-Poll frame from an STA. Can be. Meanwhile, when the AP fails to prepare a data frame to be transmitted to the STA during the SIFS time after receiving the PS-Poll frame, the AP may operate according to a deferred response method, which will be described with reference to FIG. 8.
  • a predetermined time for example, a short inter-frame space (SIFS)
  • SIFS short inter-frame space
  • the data field may include a SERVICE field, a physical layer service data unit (PSDU), a PPDU TAIL bit, and may also include a padding bit if necessary.
  • Some bits of the SERVICE field may be used for synchronization of the descrambler at the receiving end.
  • the PSDU corresponds to an MPDU (MAC Protocol Data Unit) defined in the MAC layer and may include data generated / used in an upper layer.
  • the PPDU TAIL bit can be used to return the encoder to zero.
  • the padding bit may be used to adjust the length of the data field in a predetermined unit.
  • the MAC header includes a frame control field, a duration / ID field, an address field, and the like.
  • the frame control field may include control information required for frame transmission / reception.
  • the duration / ID field may be set to a time for transmitting the corresponding frame.
  • the duration / ID field included in the MAC header may be set to 16 bits long (e.b., B0 to B15).
  • the content included in the period / ID field may vary depending on the frame type and subtype, whether the content is transmitted during the CFP (contention free period), the QoS capability of the transmitting STA, and the like.
  • the duration / ID field may include the AID of the transmitting STA (e.g., via 14 LSB bits), and 2 MSB bits may be set to one.
  • the frame control field of the MAC header may include Protocol Version, Type, Subtype, To DS, From DS, More Fragment, Retry, Power Management, More Data, Protected Frame, Order subfields.
  • the content of each subfield of the frame control field may refer to an IEEE 802.11 standard document.
  • PCR is used for data transmission and reception, and may be turned off when there is no data to transmit and receive. As such, when the PCR is turned off, the WURx of the STA may wake up the PCR when there is a packet to receive. Therefore, user data is transmitted and received through PCR.
  • WURx is not used for user data, it can only serve to wake up the PCR transceiver.
  • WURx can be in the form of a simple receiver without a transmitter and is active while PCR is off. It is desirable that the target power consumption of the WURx in the activated state does not exceed 100 microwatts (uW).
  • a simple modulation scheme for example, an on-off keying (OOK) scheme, may be used, and a narrow bandwidth (e.g., 4 MHz, 5 MHz) may be used.
  • the reception range (e.g., distance) that WURx targets may be equivalent to the current 802.11.
  • FIG. 12 is a diagram for explaining the design and operation of a WUR packet.
  • the WUR packet may include a PCR part 1200 and a WUR part 1205.
  • the PCR part 1200 is for coexistence with the legacy WLAN system, and the PCR part may be referred to as a WLAN preamble.
  • the PCR part may be referred to as a WLAN preamble.
  • at least one or more of L-STF, L-LTF, and L-SIG of the legacy WLAN may be included in the PCR part 1200.
  • the 3rd party legacy STA may know that the WUR packet is not intended for the user through the PCR part 1200 of the WUR packet, and that the medium of the PCR is occupied by another STA.
  • WURx does not decode the PCR part of the WUR packet. This is because WURx, which supports narrowband and OOK demodulation, does not support PCR signal reception.
  • At least a part of the WUR part 1205 may be modulated by an on-off keying (OOK) method.
  • the WUR part may include at least one of a WUR preamble, a MAC header (e.g., a recipient address, etc.), a frame body, and a frame check sequence (FCS).
  • OOK modulation may be performed by modifying the OFDM transmitter.
  • the WUR packet since the WUR packet needs to be designed to be compatible with the WLAN system, the WUR packet includes a preamble (eg, OFDM) and a new LP-WUR signal waveform (eg, OOK) of legacy WLAN. can do.
  • a preamble eg, OFDM
  • a new LP-WUR signal waveform eg, OOK
  • the WUR packet of FIG. 13 shows an example of a WUR packet.
  • the WUR packet of FIG. 13 includes a PCR part (e.g., legacy WLAN preamble) for coexistence with a legacy STA.
  • a PCR part e.g., legacy WLAN preamble
  • the legacy WLAN preamble may include L-STF, L-LTF, and L-SIG.
  • the WLAN STA e.g., 3rd Party
  • the L-SIG field may indicate the length of the payload (e.g., OOK modulated) of the WUR packet.
  • the WUR part may include at least one of a WUR preamble, a MAC header, a frame body, and an FCS.
  • the WUR preamble may include, for example, a PN sequence.
  • the MAC header may include the receiver address.
  • the frame body may contain other information needed for wake up.
  • the FCS may include a cyclic redundancy check (CRC).
  • FIG. 14 illustrates the waveform for the WUR packet of FIG. 13.
  • 1 bit may be transmitted per 1 OFDM symbol length (e.g., 4 usec).
  • the data rate of the WUR part may be 250 kbps.
  • FIG. 15 illustrates generation of a WUR packet using an OFDM transmitter of a wireless LAN.
  • a phase shift keying (PSK) -OFDM transmission scheme is used.
  • Generating a WUR packet by adding a separate OOK modulator for OOK modulation has a disadvantage of increasing an implementation cost of a transmitter. Therefore, a method of generating a OOK modulated WUR packet by reusing an OFDM transmitter will be described.
  • bit value 1 is a symbol (ie, on) in which any power in a symbol is loaded or has a power above a threshold
  • bit value 0 is a symbol in which no power in the symbol is loaded or has a power below a threshold. modulated to (ie, off).
  • bit value 1 it is also possible to define bit value 1 as power off.
  • OOK modulation scheme As described above, in the OOK modulation scheme, a bit value 1/0 is indicated through on / off of power at a corresponding symbol position.
  • Such a simple OOK modulation / demodulation scheme has an advantage of reducing power consumption and cost for realizing the signal detection / demodulation of the receiver.
  • OOK modulation for turning on / off a signal may be performed by reusing an existing OFDM transmitter.
  • the left graph of FIG. 15 shows real parts and imaginary parts of normalized amplitude during one symbol period (eg, 4 usec) for OOK modulated bit value 1 by reusing the OFDM transmitter of the existing WLAN. (imaginary) shows the part. Since the OOK modulation result for the bit value 0 corresponds to power off, illustration is omitted.
  • the right graph of FIG. 15 shows normalized power spectral density (PSD) in the frequency domain for OOK modulated bit value 1 by reusing an OFDM transmitter of an existing WLAN.
  • PSD power spectral density
  • a center 4 MHz in that band may be used for the WUR.
  • the WUR operates with a 4 MHz bandwidth.
  • a frequency bandwidth of another size may be used.
  • the subcarrier spacing (e.g., subcarrier spacing) is 312.5 kHz, and the bandwidth of the OOK pulse corresponds to 13 subcarriers.
  • CP cyclic prefix
  • the WUR packet may be referred to as a WUR signal, a WUR frame, or a WUR PPDU.
  • the WUR packet may be a packet for broadcast / multicast (e.g., WUR beacon) or a packet for unicast (e.g., a packet for terminating and waking up the WUR mode of a specific WUR STA).
  • the WURx may include an RF / analog front-end, a digital baseband processor, and a simple packet parser. 16 is an exemplary configuration, and the WUR receiver of the present invention is not limited to FIG.
  • a WLAN STA having a WUR receiver will be referred to simply as a WUR STA.
  • the proposed WUR signal is generated through OOK modulation to reduce the reception power consumption of the receiver and is transmitted using an OFDM transmitter using only some tones in the available band.
  • an embodiment of the present invention proposes a method for reducing a timing offset in a receiver when transmitting a WUR signal using OOK modulation.
  • Figure 17 shows the frame format of the WUR signal to wake up the PCR.
  • the WUR frame includes an L-Part before the WUR part for coexistence with PCR (e.g., legacy WLAN).
  • the WUR part may include a WUR-preamble, a WUR-SIG, and a WUR-body.
  • the WUR-Body may include control information rather than user data for the WUR STA.
  • the L-PART is for a third party STA (e.g., PCR STA), not a WUR receiver, and the WUR receiver may not decode the L-part.
  • a third party STA e.g., PCR STA
  • the WUR receiver may not decode the L-part.
  • the WUR part may be transmitted in narrow bandwidth on some of the available tones included in the band in which the L-part is transmitted.
  • the narrow band may be any one of 1,2,4,8,10 MHz.
  • narrowband 1,2,4,8,10 MHz correspond to 4,8,13,26,32 tones, respectively, and the length of the frequency sequence constituting the WUR ON symbol is each tone. May be equal to
  • the narrow bands 1,2,4,8,10 MHz correspond to 13, 26, 52, 103, and 128 tones, respectively.
  • the WUR receiver may detect the OOK modulated WUR signal through envelope detection (ED) of the received signal.
  • ED envelope detection
  • symbols of the WUR preamble may be used to set a threshold for envelop detection of a received signal.
  • the measurement symbol s for measuring the received signal may be additionally inserted into the WUR preamble.
  • the measurement symbols s may all be set as OOK on symbols.
  • the added measurement symbol may be used not only to measure the received signal but also to additionally indicate other information. For example, when the added measurement symbol is 6-symbol, BSS color information (i.e. 6-bit) may be transmitted through the corresponding symbols.
  • the measurement may be performed using symbols of the preamble designed for timing synchronization and packet detection without inserting additional symbols into the preamble. If the OFF symbol is present in the preamble, the measurement performance may be degraded due to the OFF symbol. To compensate for this, the measurement may be performed only through successive ON symbols in the preamble sequence.
  • the WUR STA may measure the threshold using only symbols corresponding to a predetermined order.
  • the preamble sequence may be set so that the corresponding symbol does not become an OFF symbol.
  • the preamble sequence may be set such that the preamble sequence does not have 0 in 1, 4, and 7th as [1 1 0 1 0 1 1 1 0].
  • the threshold measurement method of the present invention is not limited to the frame structure of FIG. 17, and the threshold value may be measured using another frame structure.
  • FIG. 18 illustrates a WUR frame according to another embodiment of the present invention.
  • a symbol for setting a threshold value for distinguishing whether information of a received signal is 1 or 0 may be transmitted before the WUR preamble.
  • the OOK symbol s for setting the WUR ED threshold may be transmitted before the WUR preamble in order to set the threshold for WUR ED (envelop detection).
  • the number of OOK symbols for setting the WUR ED threshold may be two or more.
  • all of the OOK symbols for setting the WUR ED threshold may be OOK ON symbols.
  • a OOK symbol for setting the WUR ED threshold shown in FIG. 18 may be included in the WUR preamble.
  • the OOK symbol for setting the WUR ED threshold is located at the head of the WUR preamble, and the preamble sequence may be divided into a sequence for measurement and a preamble sequence for synchronization and packet detection.
  • the present invention is not limited to a method of transmitting a symbol by adding a part for measuring a threshold value as shown in FIG. 18 or by adding corresponding sequence information to a preamble.
  • the measurement may be performed only with the preamble without additional symbols. Some or all of the preamble symbols may be used to measure the received signal. Alternatively, the measurement may be performed using only specific symbols of the preamble. In this case, a sequence may be set such that the corresponding symbol becomes a OOK on symbol.
  • the WUR preamble may be set to a known sequence for time synchronization of the WUR signal.
  • the preamble may be configured with the number of symbols corresponding to the sequence length.
  • a description of a symbol for threshold measurement is omitted, but a symbol for threshold measurement may be set before or after the WUR preamble proposed for time synchronization.
  • a fixed sequence may be used regardless of a broadcast / multicast / unicast transmission scheme or another sequence may be used depending on the transmission scheme. If a fixed sequence is used, the implementation is simple, but overhead for an indication of a transmission scheme may occur.
  • the WUR receiver may determine whether the WUR frame received through the WUR preamble is a broadcast / multicast / unicast scheme. In this case, overhead may be reduced since it is not necessary to transmit additional information to indicate whether the broadcast / multicast / unicast method is used.
  • the WUR preamble may be transmitted as follows.
  • a signal corresponding to 4,8,13,16,26,32 tones may be transmitted in one WUR symbol.
  • the information carried on the tones may correspond to a pseudo noise (PN) sequence.
  • PN pseudo noise
  • the length of the PN sequence may be equal to the number of available tones. If the number of available tones is 13, the length of the PN sequence may also be 13.
  • a known sequence (WPS, Preamble Sequence) for the WUR preamble is [1 1 1 0 1 0 1] in the time domain and a PN sequence of length 13 in the frequency domain is [1 0 1 1 0 1 0 0 1 1 1 0 1].
  • the signal carried in the preamble symbol k in the frequency domain may be represented by PS (k) * PN code.
  • PS is a binary code, but this is only an example. 1/0 of the binary code may be replaced with -1/1.
  • a WUR receiver receiving a WUR preamble transmitted by applying a predetermined PN sequence to a random PS performs cross correlation using a PN sequence and a received signal that are already known about a symbol corresponding to a length of the preamble. Timing synchronization can be performed.
  • the WUR receiver takes a cross correlation instead of auto correlation for the received signal for timing synchronization because of the following characteristics of the PN_sequence.
  • Tx_seq Data * PN_seq
  • the WUR receiver may perform time synchronization by windowing the length of the preamble with respect to the received signal and performing cross correlation with the PN_sequence corresponding to the window size for each window.
  • the frequency sequences for the PS and the OOK on symbols are set differently, but in the present embodiment, the PS may be set to be the same as the PN sequence.
  • the lengths of the PS and PN sequences are the same, and the number of available tones for transmitting the WUR signal is the same as the length of the PN sequence.
  • one PN sequence may be applied to both the time domain and the frequency domain of the WUR preamble.
  • the WUR preamble consists of the same number of symbols as the length of a predetermined PN seq.
  • the information carried in each symbol in the frequency domain is obtained by multiplying the bit value of PN_seq of the symbol by PN_seq, and the obtained information is mapped to each tone.
  • the WUR receiver receiving the WUR preamble configured through the above method performs cross correlation between the received signal and the PN sequence using a known PN sequence, and performs timing synchronization based on the cross correlation result.
  • different PN sequences may be used according to transmission modes, or different PN sequences may be used for each BSS.
  • different PN sequences may be determined for each BSS using BSS color and / or AP ID.
  • PN sequences may be used for each STA in order to reduce the influence of interference due to transmission of several WUR frames within one BSS.
  • the PN sequence may be assigned when the STA associates with the AP or when performing capability negotiation.
  • the PN sequence allocated to each STA may be determined by AID or P-AID.
  • the AP determines on / off of a plurality of on-off keying (OOK) symbols to be included in a WUR preamble based on a pseudo noise (PN) sequence in the time domain (2005).
  • OLK on-off keying
  • PN pseudo noise
  • the AP maps the PN sequence to tones of each on symbol of the plurality of OOK symbols in the frequency domain (2010).
  • the AP transmits a WUR frame including the WUR preamble (2015).
  • the length of the PN sequence, the number of OOK symbols, and the number of tones to which the WUR preamble is transmitted may all be set the same.
  • the PN sequence is a binary sequence including a plurality of bits, and a OOK symbol corresponding to a bit having a value of 1 in the binary sequence may be determined as an on symbol.
  • a OOK symbol corresponding to a bit having a zero value in a binary sequence is determined as an off symbol, and all zeros may be mapped to tones of the off symbol.
  • a WUR preamble having a PN sequence or a number of OOK symbols mapped to 0 in the frequency domain according to on / off may be transmitted through an orthogonal frequency divisional multiplex (OFDM) transmitter.
  • OFDM orthogonal frequency divisional multiplex
  • the PN sequence may be set differently for each BSS based on an identifier of an AP or a basic service set (BSS) color, or the PN sequence may be set differently for each STA based on an association identifier (AID) or a partial AID (PAID).
  • BSS basic service set
  • AID association identifier
  • PAID partial AID
  • the PN sequence may be assigned through an association procedure or a capability negotiation procedure on a primary connectivity radio (PCR).
  • PCR primary connectivity radio
  • the WUR frame may further include at least one measurement symbol that provides a criterion for the WUR STA receiving the WUR frame to determine on / off of each of the plurality of OOK symbols.
  • At least one measurement symbol is all set to an on symbol and may be located before the WUR preamble.
  • the WUR part includes a WUR preamble part and a control information part, and it has been described that the L-Part for PCR is included before the WUR part, but terms according to embodiments of the present invention are referred to by different names.
  • the WUR preamble part may be referred to as a WUR sync field
  • the control information part may also be referred to as a WUR data field.
  • the entirety including the WUR sync field and the L-Part (i.e., non-WUR part) for PCR may be referred to as a preamble.
  • multiple data rates may be supported for WUR frames.
  • data rates of 62.5 kbps and 250 kbps can be supported in the WUR frame.
  • the data rate actually used may be indicated via a synchronization sequence.
  • a data rate of 62.5 kbps may be used when the first sync sequence is used, and a data rate of 250 kbps may be used when the second sync sequence is used.
  • a plurality of WUR sync sequences may be supported.
  • 21 is a view for explaining an apparatus for implementing the method as described above.
  • the wireless device 100 of FIG. 21 may correspond to a specific STA of the above description, and the wireless device 850 may correspond to the AP of the above description.
  • the STA 100 may include a processor 110, a memory 120, and a transceiver 130, and the AP 150 may include a processor 160, a memory 170, and a transceiver 180.
  • the transceivers 130 and 180 transmit / receive wireless signals and may be implemented in a physical layer, such as IEEE 802.11 / 3GPP.
  • Processors 110 and 160 run at the physical layer and / or MAC layer and are coupled to transceivers 130 and 180.
  • Processors 110 and 160 may perform the aforementioned UL MU scheduling procedure.
  • Processors 110 and 160 and / or transceivers 130 and 180 may include application-specific integrated circuits (ASICs), other chipsets, logic circuits, and / or data processors.
  • the memories 120 and 170 may include read-only memory (ROM), random access memory (RAM), flash memory, memory cards, storage media and / or other storage units.
  • ROM read-only memory
  • RAM random access memory
  • flash memory memory cards
  • storage media storage media and / or other storage units.
  • the method described above can be executed as a module (eg, process, function) that performs the functions described above.
  • the module may be stored in the memories 120 and 170 and may be executed by the processors 110 and 160.
  • the memories 120 and 170 may be disposed inside or outside the processes 110 and 160, and may be connected to the processes 110 and 160 by well-known means.
  • the transceiver 130 of the STA may include a transmitter (not shown) and a receiver (not shown).
  • the receiver of the STA may include a main connected radio receiver for receiving a main connected radio signal (eg, a wireless LAN such as IEEE 802.11 a / b / g / n / ac / ax) and a WUR receiver for receiving a WUR signal.
  • the transmitter of the STA may include a primary connected radio transmitter for transmitting the primary connected radio signal.
  • the transceiver 180 of the AP may include a transmitter (not shown) and a receiver (not shown).
  • the transmitter of the AP may correspond to an OFDM transmitter.
  • the AP may transmit the WUR payload by the OOK scheme by reusing the OFDM transmitter. For example, as described above, the AP may OOK modulate the WUR payload through an OFDM transmitter.
  • the present invention can be applied to various wireless communication systems including IEEE 802.11.

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  • Engineering & Computer Science (AREA)
  • Computer Networks & Wireless Communication (AREA)
  • Signal Processing (AREA)
  • Mobile Radio Communication Systems (AREA)

Abstract

Un mode de réalisation de la présente invention concerne un procédé par lequel un point d'accès (AP) transmet une trame radio de réveil (WUR) dans un système LAN sans fil (WLAN).Le procédé comprend les étapes consistant à : déterminer, sur la base d'une séquence de pseudo-bruit (PN) dans un domaine temporel, l'activation/la désactivation de symboles « tout » ou « rien » (OOK) multiples devant être inclus dans un préambule WUR ; mapper la séquence PN sur des tonalités de symboles « tout » respectifs parmi les symboles OOK dans un domaine fréquentiel ; et transmettre la trame WUR contenant le préambule WUR. La totalité de la longueur de la séquence PN, le nombre de symboles OOK multiples, et le nombre de tonalités dans lesquelles le préambule WUR est transmis sont définis comme étant identiques. La séquence PN est une séquence binaire comprenant une pluralité de bits. Le symbole OOK correspondant à un bit ayant une valeur de 1 dans la séquence binaire peut être déterminé en tant que symbole « tout ».
PCT/KR2018/001040 2017-02-20 2018-01-24 Procédé de transmission ou de réception d'une trame de radio de réveil dans un système lan sans fil, et appareil associé Ceased WO2018151432A1 (fr)

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