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WO2016175439A1 - Procédé et dispositif de transmission de données dans un système de communications sans fil - Google Patents

Procédé et dispositif de transmission de données dans un système de communications sans fil Download PDF

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Publication number
WO2016175439A1
WO2016175439A1 PCT/KR2016/001790 KR2016001790W WO2016175439A1 WO 2016175439 A1 WO2016175439 A1 WO 2016175439A1 KR 2016001790 W KR2016001790 W KR 2016001790W WO 2016175439 A1 WO2016175439 A1 WO 2016175439A1
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Prior art keywords
sta
field
ppdu
symbol
boundary
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English (en)
Korean (ko)
Inventor
김진민
조한규
이욱봉
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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
    • H04L1/00—Arrangements for detecting or preventing errors in the information received
    • 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

Definitions

  • the present invention relates to a wireless communication system, and more particularly, to add a padding symbol to secure a signal processing time of a receiver according to an increase in the FFT size of data transmitted in a wireless local area network (LAN) communication system.
  • the present invention relates to a transmitting STA device and a data transmission method thereof.
  • Wi-Fi is a Wireless Local Area Network (WLAN) technology that allows devices to access the Internet in the 2.4 GHz, 5 GHz, or 6 GHz frequency bands.
  • WLAN Wireless Local Area Network
  • WLANs are based on the Institute of Electrical and Electronic Engineers (IEEE) 802.11 standard.
  • IEEE 802.11 The Wireless Next Generation Standing Committee (WNG SC) of IEEE 802.11 is an ad hoc committee that considers the next generation wireless local area network (WLAN) in the medium to long term.
  • WNG SC Wireless Next Generation Standing Committee
  • IEEE 802.11n aims to increase the speed and reliability of networks and to extend the operating range of wireless networks. More specifically, IEEE 802.11n supports High Throughput (HT), which provides up to 600 Mbps data rate, and also supports both transmitter and receiver to minimize transmission errors and optimize data rates. It is based on Multiple Inputs and Multiple Outputs (MIMO) technology using multiple antennas.
  • HT High Throughput
  • MIMO Multiple Inputs and Multiple Outputs
  • IEEE 802.11ac supports data processing speeds of 1 Gbps and higher via 80 MHz bandwidth transmission and / or higher bandwidth transmission (eg 200 MHz) and operates primarily in the 5 GHz band.
  • IEEE 802.11ax often discussed in the next-generation WLAN study group called IEEE 802.11ax or High Efficiency (HEW) WLAN, is: 1) 802.11 physical layer and MAC in the 2.4 GHz and 5 GHz bands. (medium access control) layer enhancement, 2) spectral efficiency and area throughput improvement, 3) environments with interference sources, dense heterogeneous network environments, and high user loads. Such as improving performance in real indoor environments and outdoor environments, such as the environment.
  • IEEE 802.11ax High Efficiency
  • IEEE 802.11ax Scenarios considered mainly in IEEE 802.11ax are dense environments with many access points (APs) and stations (STAs), and IEEE 802.11ax discusses spectral efficiency and area throughput improvement in such a situation. . In particular, there is an interest in improving the performance of the indoor environment as well as the outdoor environment, which is not much considered in the existing WLAN.
  • IEEE 802.11ax we are interested in scenarios such as wireless office, smart home, stadium, hotspot, and building / apartment. There is a discussion about improving system performance in dense environments with many STAs.
  • IEEE 802.11ax improves system performance in outdoor basic service set (OBSS) environment, outdoor environment performance, and cellular offloading rather than single link performance in one basic service set (BSS). Discussion is expected to be active.
  • the directionality of IEEE 802.11ax means that next-generation WLANs will increasingly have a technology range similar to that of mobile communication. Considering the situation where mobile communication and WLAN technology are recently discussed in the small cell and direct-to-direct communication area, the technical and business of next-generation WLAN and mobile communication based on IEEE 802.11ax Convergence is expected to become more active.
  • the symbol throughput is 4 times longer than legacy 802.11 systems (802.11a, 802.11n, 802.11ac, etc.) for average throughput enhancement and robust transmission in the outdoor. That is, the STA may apply a FFT size four times larger when performing OFDM modulation.
  • the number of subcarriers of the transmission signal is increased compared to the 802.11 legacy system signal, thereby improving throughput.
  • the time required to process data may be increased. Therefore, if the predefined SIFS time is used as it is, the receiving STA may not transmit the ACK frame after the determined SIFS time.
  • a physical protocol data unit (PPDU) including a physical preamble and a data field is generated.
  • the physical preamble includes a legacy preamble, and the DFT / IDFT (Discrete Fourier Transform / Inverse Discrete Fourier Transform) period of the data field is four times the DFT / IDFT period of the legacy preamble.
  • the PPDU generating step includes adding a packet extension (PE) field to the end of the PPDU based on capability information of a receiving STA and a constellation level of transmission data.
  • the PE field includes at least one PE symbol, and when the PPDU includes the PE field, tail bits for returning a convolutional encoder of the STA to a zero state include the PPDU. It may be included in the last data symbol of.
  • the last data symbol of the PPDU may include a payload as an OFDM symbol in front of the PE field.
  • the payload may include coded bits, pre-FEC padding bits and tail bits.
  • the length of the payload is at a boundary of one of a quarter boundary, 2/4 boundary, 3/4 boundary, or 4/4 boundary of the last data symbol. This may be the case.
  • the part after the payload may be filled with post FEC padding bits.
  • the length of the PE field may be adjusted according to the length of the post FEC padding bits.
  • the physical preamble indicates one of a quarter boundary, a 2/4 boundary, a 3/4 boundary, and a 4/4 boundary of the last data symbol. It may include decoding boundary information.
  • the PE field may be added to each of the plurality of receiving STAs, and the plurality of PEs may be added.
  • the length of the fields may be determined as the length of the longest PE field of the PE fields for the plurality of receiving STAs.
  • An STA (Station) device of a WLAN (Wireless LAN) system for solving the above technical problem includes: a radio frequency (RF) unit for transmitting and receiving a radio signal; And a processor for controlling the RF unit, the processor generating a physical protocol data unit (PPDU) including a physical preamble and a data field, and transmitting the PPDU;
  • the physical preamble includes a legacy preamble, and the DFT / IDFT (Discrete Fourier Transform / Inverse Discrete Fourier Transform) period of the data field is four times the DFT / IDFT period of the legacy preamble.
  • a PE Packet Extension field is added to the end of the PPDU based on the capability information and the constellation level of the transmission data, wherein the PE field includes at least one PE symbol, and the PPDU includes the PE field.
  • tail bits returning the convolutional encoder of the STA to zero state are the last data symbols of the PPDU. It may be included.
  • the receiver can secure the data decoding time, thereby solving the problem of lack of SIFS time due to the expansion of the FFT size.
  • legacy transmission and reception procedures that rely on SIFS can be applied to 11ac systems to improve compatibility with existing systems.
  • the present invention adds a padding symbol in consideration of the MCS level or data rate of transmission data, the performance of the receiver, and the like.
  • the present invention may determine the number of padding symbols to add based on the performance of the receiver. Therefore, the burden of redundancy due to the addition of the padding symbol can be minimized.
  • the implementation burden of the receiver according to the use of the 4x FFT size of the 802.11ax system can be reduced.
  • tail bits in the last data symbol instead of the last symbol (PE symbol) of the PPDU, encoding performance may be improved and latency and processing performance degradation due to encoding of unnecessary bits may be reduced.
  • the pre-FEC padding is used in a quarter of 4 to 4/4 by dividing the last data symbol, and post-FEC padding is used for a portion other than the boundary, thereby improving processing time of an additional receiver. It can be secured.
  • the length of the PE field can be reduced by the processing time required for additional receivers, thereby minimizing system redundancy.
  • the receiver can quickly identify and decode the payload.
  • the present invention can secure the received data processing time of all the receiving STAs while constantly adjusting the length of the PPDU by adjusting the length of the PE field for the plurality of receiving STAs to the length of the longest PE field during MU transmission.
  • FIG. 1 is a diagram illustrating an example of an IEEE 802.11 system to which the present invention can be applied.
  • FIG. 2 is a diagram illustrating a structure of a layer architecture of an IEEE 802.11 system to which the present invention may be applied.
  • FIG. 3 illustrates a non-HT format PPDU and a HT format PPDU of a wireless communication system to which the present invention can be applied.
  • FIG. 4 illustrates a VHT format PPDU format of a wireless communication system to which the present invention can be applied.
  • FIG. 5 is a diagram illustrating a constellation for distinguishing a format of a PPDU of a wireless communication system to which the present invention can be applied.
  • FIG. 6 illustrates a MAC frame format of an IEEE 802.11 system to which the present invention can be applied.
  • FIG. 7 is a diagram illustrating a Frame Control field in a MAC frame in a wireless communication system to which the present invention can be applied.
  • FIG. 8 illustrates the VHT format of the HT Control field in a wireless communication system to which the present invention can be applied.
  • FIG. 9 is a diagram for explaining an arbitrary backoff period and a frame transmission procedure in a wireless communication system to which the present invention can be applied.
  • FIG. 10 is a diagram illustrating an IFS relationship in a wireless communication system to which the present invention can be applied.
  • FIG. 11 is a diagram illustrating a downlink MU-MIMO transmission process in a wireless communication system to which the present invention can be applied.
  • HE 12 illustrates a High Efficiency (HE) format PPDU according to an embodiment of the present invention.
  • FIG. 13 is a diagram illustrating an HE format PPDU according to an embodiment of the present invention.
  • FIG. 14 is a diagram illustrating an HE format PPDU according to an embodiment of the present invention.
  • FIG. 15 is a diagram illustrating a HE format PPDU according to an embodiment of the present invention.
  • FIG. 16 shows an HE frame structure according to an embodiment of the present invention.
  • FIG 17 illustrates a VHT performance element according to an embodiment of the invention.
  • 19 illustrates a PPDU including tail bits according to an embodiment of the present invention.
  • FIG. 20 illustrates a configuration of a PPDU including a tail field according to an embodiment of the present invention.
  • FIG. 21 illustrates a configuration and available processing time of a PPDU according to an embodiment of the present invention.
  • FIG. 22 illustrates a configuration and available processing time of a PPDU according to an additional embodiment of the present invention.
  • FIG. 23 is a PPDU configuration method according to an embodiment of the present invention, and particularly, a configuration method of the last data symbol.
  • FIG. 24 illustrates a method for a receiving STA to obtain a length of a payload using a length field of an L-SIG according to an embodiment of the present invention.
  • FIG 25 illustrates an STA apparatus according to an embodiment of the present invention.
  • 26 shows a data transmission method of an STA apparatus according to an embodiment of the present invention.
  • CDMA code division multiple access
  • FDMA frequency division multiple access
  • TDMA time division multiple access
  • OFDMA orthogonal frequency division multiple access
  • SC-FDMA single carrier frequency division multiple access
  • GSM global system for mobile communications
  • GPRS general packet radio service
  • EDGE enhanced data rates for GSM evolution
  • OFDMA can be implemented with wireless technologies such as Institute of Electrical and Electronics Engineers (IEEE) 802.11 (Wi-Fi), IEEE 802.20 (WiMAX), IEEE 802-20, evolved UTRA (E-UTRA), and the like.
  • UTRA is part of a universal mobile telecommunications system (UMTS).
  • 3rd generation partnership project (3GPP) long term evolution (LTE) is a part of evolved UMTS (E-UMTS) using E-UTRA, and employs OFDMA in downlink and SC-FDMA in uplink.
  • LTE-A evolution of 3GPP LTE.
  • Embodiments of the present invention may be supported by standard documents disclosed in at least one of the wireless access systems IEEE 802, 3GPP and 3GPP2. That is, steps or parts which are not described to clearly reveal the technical spirit of the present invention among the embodiments of the present invention may be supported by the above documents. In addition, all terms disclosed in the present document can be described by the above standard document.
  • FIG. 1 is a diagram illustrating an example of an IEEE 802.11 system to which the present invention can be applied.
  • the IEEE 802.11 structure may be composed of a plurality of components, and a wireless communication system supporting a station (STA) station mobility that is transparent to a higher layer may be provided by their interaction.
  • STA station
  • a basic service set (BSS) may correspond to a basic building block in an IEEE 802.11 system.
  • FIG. 1 there are three BSSs (BSS 1 to BSS 3) and two STAs are included as members of each BSS (STA 1 and STA 2 are included in BSS 1, and STA 3 and STA 4 are BSS 2. Included in, and STA 5 and STA 6 are included in BSS 3) by way of example.
  • an ellipse representing a BSS may be understood to represent a coverage area where STAs included in the BSS maintain communication. This area may be referred to as a basic service area (BSA).
  • BSA basic service area
  • the most basic type of BSS in an IEEE 802.11 system is an independent BSS (IBSS).
  • the IBSS may have a minimal form consisting of only two STAs.
  • BSS 3 of FIG. 1, which is the simplest form and other components are omitted, may correspond to a representative example of the IBSS. This configuration is possible when STAs can communicate directly.
  • this type of LAN may not be configured in advance, but may be configured when a LAN is required, which may be referred to as an ad-hoc network.
  • the membership of the STA in the BSS may be dynamically changed by turning the STA on or off, the STA entering or exiting the BSS region, or the like.
  • the STA may join the BSS using a synchronization process.
  • the STA In order to access all services of the BSS infrastructure, the STA must be associated with the BSS. This association may be set up dynamically and may include the use of a Distribution System Service (DSS).
  • DSS Distribution System Service
  • the direct STA-to-STA distance in an 802.11 system may be limited by physical layer (PHY) performance. In some cases, this distance limit may be sufficient, but in some cases, communication between STAs over longer distances may be required.
  • a distribution system (DS) may be configured to support extended coverage.
  • the DS refers to a structure in which BSSs are interconnected. Specifically, instead of the BSS independently as shown in FIG. 1, the BSS may exist as an extended type component of a network composed of a plurality of BSSs.
  • DS is a logical concept and can be specified by the characteristics of the Distribution System Medium (DSM).
  • DSM Distribution System Medium
  • the IEEE 802.11 standard logically distinguishes between wireless medium (WM) and distribution system medium (DSM). Each logical medium is used for a different purpose and is used by different components.
  • the definition of the IEEE 802.11 standard does not limit these media to the same or to different ones.
  • the plurality of media are logically different, and thus the flexibility of the structure of the IEEE 802.11 system (DS structure or other network structure) can be described. That is, the IEEE 802.11 system structure can be implemented in various ways, the corresponding system structure can be specified independently by the physical characteristics of each implementation.
  • the DS may support mobile devices by providing seamless integration of multiple BSSs and providing logical services for handling addresses to destinations.
  • the AP means an entity that enables access to the DS through the WM to the associated STAs and has STA functionality. Data movement between the BSS and the DS may be performed through the AP.
  • STA 2 and STA 3 illustrated in FIG. 1 have a functionality of STA, and provide a function of allowing associated STAs STA 1 and STA 4 to access the DS.
  • all APs basically correspond to STAs, all APs are addressable entities.
  • the address used by the AP for communication on the WM and the address used by the AP for communication on the DSM need not necessarily be the same.
  • Data transmitted from one of the STAs associated with an AP to the STA address of that AP may always be received at an uncontrolled port and processed by an IEEE 802.1X port access entity.
  • transmission data (or frame) may be transmitted to the DS.
  • a wireless network of arbitrary size and complexity may be composed of DS and BSSs.
  • this type of network is referred to as an extended service set (ESS) network.
  • the ESS may correspond to a set of BSSs connected to one DS. However, the ESS does not include a DS.
  • the ESS network is characterized by what appears to be an IBSS network at the Logical Link Control (LLC) layer. STAs included in the ESS may communicate with each other, and mobile STAs may move from one BSS to another BSS (within the same ESS) transparently to the LLC.
  • LLC Logical Link Control
  • BSSs can be partially overlapped, which is the form generally used to provide continuous coverage.
  • the BSSs may not be physically connected, and logically there is no limit to the distance between the BSSs.
  • the BSSs can be located at the same physical location, which can be used to provide redundancy.
  • one (or more) IBSS or ESS networks may be physically present in the same space as one or more ESS networks. This may be necessary if the ad-hoc network is operating at the location of the ESS network, if the IEEE 802.11 networks are physically overlapped by different organizations, or if two or more different access and security policies are required at the same location. It may correspond to an ESS network type in a case.
  • an STA is a device that operates according to Medium Access Control (MAC) / PHY regulations of IEEE 802.11. As long as the function of the STA is not distinguished from the AP individually, the STA may include an AP STA and a non-AP STA. However, when communication is performed between the STA and the AP, the STA may be understood as a non-AP STA. In the example of FIG. 1, STA 1, STA 4, STA 5, and STA 6 correspond to non-AP STAs, and STA 2 and STA 3 correspond to AP STAs.
  • MAC Medium Access Control
  • Non-AP STAs generally correspond to devices that users directly handle, such as laptop computers and mobile phones.
  • a non-AP STA includes a wireless device, a terminal, a user equipment (UE), a mobile station (MS), a mobile terminal, and a wireless terminal.
  • WTRU wireless transmit / receive unit
  • MTC machine-type communication
  • M2M machine-to-machine
  • the AP is a base station (BS), Node-B (Node-B), evolved Node-B (eNB), and Base Transceiver System (BTS) in other wireless communication fields.
  • BS base station
  • Node-B Node-B
  • eNB evolved Node-B
  • BTS Base Transceiver System
  • downlink means communication from the AP to the non-AP STA
  • uplink means communication from the non-AP STA to the AP.
  • the transmitter may be part of an AP and the receiver may be part of a non-AP STA.
  • a transmitter may be part of a non-AP STA and a receiver may be part of an AP.
  • FIG. 2 is a diagram illustrating a structure of a layer architecture of an IEEE 802.11 system to which the present invention may be applied.
  • the layer architecture of the IEEE 802.11 system may include a MAC sublayer and a PHY sublayer.
  • the PHY sublayer may be divided into a Physical Layer Convergence Procedure (PLCP) entity and a Physical Medium Dependent (PMD) entity.
  • PLCP Physical Layer Convergence Procedure
  • PMD Physical Medium Dependent
  • the PLCP entity plays a role of connecting a data frame with a MAC sublayer
  • the PMD entity plays a role of wirelessly transmitting and receiving data with two or more STAs.
  • Both the MAC sublayer and the PHY sublayer may include a management entity, which may be referred to as a MAC sublayer management entity (MLME) and a PHY sublayer management entity (PLME), respectively.
  • MLME MAC sublayer management entity
  • PLME PHY sublayer management entity
  • These management entities provide layer management service interfaces through the operation of layer management functions.
  • the MLME may be connected to the PLME to perform management operations of the MAC sublayer, and likewise the PLME may be connected to the MLME to perform management operations of the PHY sublayer.
  • a Station Management Entity may be present in each STA.
  • the SME is a management entity independent of each layer.
  • the SME collects layer-based state information from MLME and PLME or sets values of specific parameters of each layer.
  • the SME can perform these functions on behalf of general system management entities and implement standard management protocols.
  • the XX-GET.request primitive is used to request the value of a Management Information Base attribute (MIB attribute), and the XX-GET.confirm primitive, if the status is 'SUCCESS', returns the value of that MIB attribute. Otherwise, it returns with an error indication in the status field.
  • MIB attribute Management Information Base attribute
  • the XX-SET.request primitive is used to request that a specified MIB attribute be set to a given value. If the MIB attribute is meant for a particular action, this request requests the execution of that particular action. And, if the state is 'SUCCESS' XX-SET.confirm primitive, it means that the specified MIB attribute is set to the requested value. In other cases, the status field indicates an error condition. If this MIB attribute means a specific operation, this primitive can confirm that the operation was performed.
  • MIB attribute Management Information Base attribute
  • XX-GET.confirm primitive if the status is 'SUCCESS', returns the value of that MIB attribute. Otherwise, it returns with
  • the MAC sublayer includes a MAC header and a frame check sequence (FCS) in a MAC Service Data Unit (MSDU) or a fragment of an MSDU received from an upper layer (eg, an LLC layer).
  • FCS frame check sequence
  • MSDU MAC Service Data Unit
  • MPDU MAC Protocol Data Unit
  • A-MSDU aggregated MSDU
  • a plurality of MSDUs may be merged into a single A-MSDU (aggregated MSDU).
  • the MSDU merging operation may be performed at the MAC upper layer.
  • the A-MSDU is delivered to the PHY sublayer as a single MPDU (if not fragmented).
  • the PHY sublayer generates a physical protocol data unit (PPDU) by adding an additional field including information required by a physical layer transceiver to a physical service data unit (PSDU) received from the MAC sublayer. . PPDUs are transmitted over wireless media.
  • PPDU physical protocol data unit
  • the PSDU is substantially the same as the MPDU since the PHY sublayer is received from the MAC sublayer and the MPDU is transmitted by the MAC sublayer to the PHY sublayer.
  • A-MPDU aggregated MPDU
  • a plurality of MPDUs may be merged into a single A-MPDU.
  • the MPDU merging operation may be performed at the MAC lower layer.
  • A-MPDUs may be merged with various types of MPDUs (eg, QoS data, Acknowledge (ACK), Block ACK (BlockAck), etc.).
  • the PHY sublayer receives the A-MPDU as a single PSDU from the MAC sublayer. That is, the PSDU is composed of a plurality of MPDUs.
  • A-MPDUs are transmitted over the wireless medium in a single PPDU.
  • PPDU Physical Protocol Data Unit
  • IEEE 802.11 WLAN system to which the present invention can be applied.
  • FIG. 3 illustrates a non-HT format PPDU and a HT format PPDU of a wireless communication system to which the present invention can be applied.
  • Non-HT PPDUs may also be referred to as legacy PPDUs.
  • the non-HT format PPDU includes an L-STF (Legacy (or Non-HT) Short Training field), L-LTF (Legacy (or, Non-HT) Long Training field) and It consists of a legacy format preamble and a data field composed of L-SIG (Legacy (or Non-HT) SIGNAL) field.
  • L-STF Legacy (or Non-HT) Short Training field
  • L-LTF Legacy (or, Non-HT) Long Training field
  • L-SIG Legacy (or Non-HT) SIGNAL
  • the L-STF may include a short training orthogonal frequency division multiplexing symbol (OFDM).
  • L-STF can be used for frame timing acquisition, automatic gain control (AGC), diversity detection, and coarse frequency / time synchronization. .
  • the L-LTF may include a long training orthogonal frequency division multiplexing symbol.
  • L-LTF may be used for fine frequency / time synchronization and channel estimation.
  • the L-SIG field may be used to transmit control information for demodulation and decoding of the data field.
  • the L-SIG field consists of a 4-bit Rate field, 1-bit Reserved bit, 12-bit Length field, 1-bit parity bit, and 6-bit Signal Tail field. Can be.
  • the rate field contains rate information, and the length field indicates the number of octets of the PSDU.
  • FIG. 3B illustrates an HT-mixed format PPDU (HTDU) for supporting both an IEEE 802.11n system and an IEEE 802.11a / g system.
  • HTDU HT-mixed format PPDU
  • the HT mixed format PPDU includes a legacy format preamble including an L-STF, L-LTF, and L-SIG fields, an HT-SIG (HT-Signal) field, and an HT-STF (HT Short). Training field), HT-formatted preamble and data field including HT-LTF (HT Long Training field).
  • L-STF, L-LTF, and L-SIG fields mean legacy fields for backward compatibility, they are the same as non-HT formats from L-STF to L-SIG fields. Even if the L-STA receives the HT mixed PPDU, the L-STA may interpret the data field through the L-LTF, L-LTF and L-SIG fields. However, the L-LTF may further include information for channel estimation that the HT-STA performs to receive the HT mixed PPDU and demodulate the L-SIG field and the HT-SIG field.
  • the HT-STA may know that it is an HT-mixed format PPDU using the HT-SIG field following the legacy field, and may decode the data field based on the HT-STA.
  • the HT-LTF field may be used for channel estimation for demodulation of the data field. Since IEEE 802.11n supports Single-User Multi-Input and Multi-Output (SU-MIMO), a plurality of HT-LTF fields may be configured for channel estimation for each data field transmitted in a plurality of spatial streams.
  • SU-MIMO Single-User Multi-Input and Multi-Output
  • the HT-LTF field includes data HT-LTF used for channel estimation for spatial streams and extension HT-LTF (additional used for full channel sounding). It can be configured as. Accordingly, the plurality of HT-LTFs may be equal to or greater than the number of spatial streams transmitted.
  • the L-STF, L-LTF, and L-SIG fields are transmitted first in order to receive the L-STA and acquire data. Thereafter, the HT-SIG field is transmitted for demodulation and decoding of data transmitted for the HT-STA.
  • the HT-SIG field is transmitted without performing beamforming so that the L-STA and HT-STA can receive the corresponding PPDU to acquire data, and then the HT-STF, HT-LTF and data fields transmitted are precoded. Wireless signal transmission is performed through.
  • the HT-STF field is transmitted to allow the STA to perform precoding to take into account the variable power due to precoding, and then the plurality of HT-LTF and data fields after that.
  • FIG. 3 (c) illustrates an HT-GF format PPDU (HT-GF) for supporting only an IEEE 802.11n system.
  • the HT-GF format PPDU includes HT-GF-STF, HT-LTF1, HT-SIG field, a plurality of HT-LTF2 and data fields.
  • HT-GF-STF is used for frame timing acquisition and AGC.
  • HT-LTF1 is used for channel estimation.
  • the HT-SIG field is used for demodulation and decoding of the data field.
  • HT-LTF2 is used for channel estimation for demodulation of data fields. Similarly, since HT-STA uses SU-MIMO, channel estimation is required for each data field transmitted in a plurality of spatial streams, and thus HT-LTF2 may be configured in plural.
  • the plurality of HT-LTF2 may be configured of a plurality of Data HT-LTF and a plurality of extended HT-LTF similarly to the HT-LTF field of the HT mixed PPDU.
  • the data field is a payload, and includes a service field, a SERVICE field, a scrambled PSDU field, tail bits, and padding bits. It may include. All bits of the data field are scrambled.
  • FIG. 3 (d) shows a service field included in a data field.
  • the service field has 20 bits. Each bit is assigned from 0 to 15, and transmitted sequentially from bit 0. Bits 0 to 6 are set to 0 and used to synchronize the descrambler in the receiver.
  • the IEEE 802.11ac WLAN system supports downlink multi-user multiple input multiple output (MU-MIMO) transmission in which a plurality of STAs simultaneously access a channel in order to efficiently use a wireless channel.
  • MU-MIMO downlink multi-user multiple input multiple output
  • the AP may simultaneously transmit packets to one or more STAs that are paired with MIMO.
  • DL MU transmission (downlink multi-user transmission) refers to a technology in which an AP transmits a PPDU to a plurality of non-AP STAs through the same time resource through one or more antennas.
  • the MU PPDU refers to a PPDU that delivers one or more PSDUs for one or more STAs using MU-MIMO technology or OFDMA technology.
  • the SU PPDU means a PPDU having a format in which only one PSDU can be delivered or in which no PSDU exists.
  • control information transmitted to the STA may be relatively large compared to the size of 802.11n control information for MU-MIMO transmission.
  • An example of control information additionally required for MU-MIMO support includes information indicating the number of spatial streams received by each STA, information related to modulation and coding of data transmitted to each STA, and the like. Can be.
  • the size of transmitted control information may be increased according to the number of receiving STAs.
  • control information required for MU-MIMO transmission is required separately for common control information common to all STAs and specific STAs.
  • the data may be transmitted by being divided into two types of information of dedicated control information.
  • FIG. 4 illustrates a VHT format PPDU format of a wireless communication system to which the present invention can be applied.
  • VHT format PPDU VHT format PPDU
  • a VHT format PPDU includes a legacy format preamble including a L-STF, L-LTF, and L-SIG fields, a VHT-SIG-A (VHT-Signal-A) field, and a VHT-STF ( A VHT format preamble and a data field including a VHT Short Training field (VHT-LTF), a VHT Long Training field (VHT-LTF), and a VHT-SIG-B (VHT-Signal-B) field.
  • VHT-LTF VHT Short Training field
  • VHT-LTF VHT Long Training field
  • VHT-SIG-B VHT-Signal-B
  • L-STF, L-LTF, and L-SIG mean legacy fields for backward compatibility, they are the same as non-HT formats from L-STF to L-SIG fields.
  • the L-LTF may further include information for channel estimation to be performed to demodulate the L-SIG field and the VHT-SIG-A field.
  • the L-STF, L-LTF, L-SIG field, and VHT-SIG-A field may be repeatedly transmitted in 20 MHz channel units. For example, when a PPDU is transmitted on four 20 MHz channels (i.e., 80 MHz bandwidth), the L-STF, L-LTF, L-SIG field, and VHT-SIG-A field are repeatedly transmitted on every 20 MHz channel. Can be.
  • the VHT-STA may know that it is a VHT format PPDU using the VHT-SIG-A field following the legacy field, and may decode the data field based on the VHT-STA.
  • the L-STF, L-LTF and L-SIG fields are transmitted first in order to receive the L-STA and acquire data. Thereafter, the VHT-SIG-A field is transmitted for demodulation and decoding of data transmitted for the VHT-STA.
  • the VHT-SIG-A field is a field for transmitting control information common to the AP and the MIMO paired VHT STAs, and includes control information for interpreting the received VHT format PPDU.
  • the VHT-SIG-A field may include a VHT-SIG-A1 field and a VHT-SIG-A2 field.
  • the VHT-SIG-A1 field includes information on channel bandwidth (BW) used, whether space time block coding (STBC) is applied, and group identification information for indicating a group of STAs grouped in MU-MIMO.
  • Group ID Group Identifier
  • NSTS space-time streams
  • Partial AID Partial Association Identifier
  • Transmit power save forbidden information can do.
  • the Group ID means an identifier assigned to the STA group to be transmitted to support MU-MIMO transmission, and may indicate whether the currently used MIMO transmission method is MU-MIMO or SU-MIMO.
  • the VHT-SIG-A2 field contains information on whether a short guard interval (GI) is used, forward error correction (FEC) information, information on modulation and coding scheme (MCS) for a single user, and multiple information.
  • GI short guard interval
  • FEC forward error correction
  • MCS modulation and coding scheme
  • Information on the type of channel coding for the user beamforming-related information, redundancy bits for cyclic redundancy checking (CRC), tail bits of convolutional decoder, and the like. Can be.
  • VHT-STF is used to improve the performance of AGC estimation in MIMO transmission.
  • VHT-LTF is used by the VHT-STA to estimate the MIMO channel. Since the VHT WLAN system supports MU-MIMO, the VHT-LTF may be set as many as the number of spatial streams in which a PPDU is transmitted. In addition, if full channel sounding is supported, the number of VHT-LTFs may be greater.
  • the VHT-SIG-B field includes dedicated control information required for a plurality of MU-MIMO paired VHT-STAs to receive a PPDU and acquire data. Therefore, the VHT-STA may be designed to decode the VHT-SIG-B field only when the common control information included in the VHT-SIG-A field indicates the MU-MIMO transmission currently received. . On the other hand, if the common control information indicates that the currently received PPDU is for a single VHT-STA (including SU-MIMO), the STA may be designed not to decode the VHT-SIG-B field.
  • the VHT-SIG-B field includes a VHT-SIG-B length field, a VHT-MCS field, a reserved field, and a tail field.
  • the VHT-SIG-B Length field indicates the length of the A-MPDU (before end-of-frame padding).
  • the VHT-MCS field includes information on modulation, encoding, and rate-matching of each VHT-STA.
  • the size of the VHT-SIG-B field may vary depending on the type of MIMO transmission (MU-MIMO or SU-MIMO) and the channel bandwidth used for PPDU transmission.
  • FIG. 4 (b) illustrates the VHT-SIG-B field according to the PPDU transmission bandwidth.
  • the VHT-SIG-B bits are repeated twice.
  • the VHT-SIG-B bits are repeated four times and pad bits set to zero are attached.
  • VHT-SIG-B bits are repeated four times, as with the 80 MHz transmission, and pad bits set to zero are attached. Then, all 117 bits are repeated again.
  • information indicating a bit size of a data field constituting the PPDU and / or indicating a bit stream size constituting a specific field May be included in the VHT-SIG-A field.
  • the L-SIG field may be used to effectively use the PPDU format.
  • a length field and a rate field included in the L-SIG field and transmitted may be used to provide necessary information.
  • MPDU MAC Protocol Data Unit
  • A-MPDU Aggregate MAC Protocol Data Unit
  • the data field is a payload and may include a service field, a scrambled PSDU, tail bits, and padding bits.
  • the STA Since the formats of various PPDUs are mixed and used as described above, the STA must be able to distinguish the formats of the received PPDUs.
  • the meaning of distinguishing a PPDU may have various meanings.
  • the meaning of identifying the PPDU may include determining whether the received PPDU is a PPDU that can be decoded (or interpreted) by the STA.
  • the meaning of distinguishing the PPDU may mean determining whether the received PPDU is a PPDU supported by the STA.
  • the meaning of distinguishing the PPDU may also be interpreted to mean what information is transmitted through the received PPDU.
  • FIG. 5 is a diagram illustrating a constellation for distinguishing a format of a PPDU of a wireless communication system to which the present invention can be applied.
  • FIG. 5 (a) illustrates the constellation of the L-SIG field included in the non-HT format PPDU
  • FIG. 5 (b) illustrates the phase rotation for HT mixed format PPDU detection
  • 5 (c) illustrates phase rotation for VHT format PPDU detection.
  • Phase is used. That is, the STA may distinguish the PPDU format based on the phase of the constellation of the OFDM symbol transmitted after the L-SIG field and / or the L-SIG field of the received PPDU.
  • binary phase shift keying (BPSK) is used for an OFDM symbol constituting the L-SIG field.
  • the STA determines whether it is an L-SIG field. That is, the STA tries to decode based on the constellation as shown in the example of FIG. If the STA fails to decode, it may be determined that the corresponding PPDU is an HT-GF format PPDU.
  • the phase of the constellation of OFDM symbols transmitted after the L-SIG field may be used. That is, the modulation method of OFDM symbols transmitted after the L-SIG field may be different, and the STA may distinguish the PPDU format based on the modulation method for the field after the L-SIG field of the received PPDU.
  • the phase of two OFDM symbols transmitted after the L-SIG field in the HT mixed format PPDU may be used.
  • the phases of OFDM symbol # 1 and OFDM symbol # 2 corresponding to the HT-SIG field transmitted after the L-SIG field in the HT mixed format PPDU are rotated by 90 degrees in the counterclockwise direction. That is, quadrature binary phase shift keying (QBPSK) is used as a modulation method for OFDM symbol # 1 and OFDM symbol # 2.
  • QBPSK constellation may be a constellation rotated by 90 degrees in a counterclockwise direction based on the BPSK constellation.
  • the STA attempts to decode the first OFDM symbol and the second OFDM symbol corresponding to the HT-SIG field transmitted after the L-SIG field of the received PPDU based on the properties as shown in the example of FIG. 5 (b). If the STA succeeds in decoding, it is determined that the corresponding PPDU is an HT format PPDU.
  • the phase of the constellation of the OFDM symbol transmitted after the L-SIG field may be used.
  • the phase of two OFDM symbols transmitted after the L-SIG field in the VHT format PPDU may be used.
  • phase of the OFDM symbol # 1 corresponding to the VHT-SIG-A field after the L-SIG field in the VHT format PPDU is not rotated, but the phase of the OFDM symbol # 2 is rotated by 90 degrees counterclockwise. . That is, BPSK is used for the modulation method for OFDM symbol # 1 and QBPSK is used for the modulation method for OFDM symbol # 2.
  • the STA attempts to decode the first OFDM symbol and the second OFDM symbol corresponding to the VHT-SIG field transmitted after the L-SIG field of the received PPDU based on the properties as illustrated in FIG. 5 (c). If the STA succeeds in decoding, it may be determined that the corresponding PPDU is a VHT format PPDU.
  • the STA may determine that the corresponding PPDU is a non-HT format PPDU.
  • FIG. 6 illustrates a MAC frame format of an IEEE 802.11 system to which the present invention can be applied.
  • a MAC frame (ie, an MPDU) includes a MAC header, a frame body, and a frame check sequence (FCS).
  • FCS frame check sequence
  • MAC Header includes Frame Control field, Duration / ID field, Address 1 field, Address 2 field, Address 3 field, Sequence control It is defined as an area including a Control field, an Address 4 field, a QoS Control field, and an HT Control field.
  • the Frame Control field includes information on the MAC frame characteristic. A detailed description of the Frame Control field will be given later.
  • the Duration / ID field may be implemented to have different values depending on the type and subtype of the corresponding MAC frame.
  • the Duration / ID field is an AID (association identifier) of the STA that transmitted the frame. It may be set to include. Otherwise, the Duration / ID field may be set to have a specific duration value according to the type and subtype of the corresponding MAC frame.
  • the Duration / ID fields included in the MAC header may be set to have the same value.
  • the Address 1 to Address 4 fields include a BSSID, a source address (SA), a destination address (DA), a transmission address (TA) indicating a transmission STA address, and a reception address indicating a destination STA address (TA).
  • SA source address
  • DA destination address
  • TA transmission address
  • TA reception address indicating a destination STA address
  • RA It is used to indicate Receiving Address.
  • the address field implemented as a TA field may be set to a bandwidth signaling TA value, in which case, the TA field may indicate that the corresponding MAC frame contains additional information in the scrambling sequence.
  • the bandwidth signaling TA may be represented by the MAC address of the STA transmitting the corresponding MAC frame, but the Individual / Group bit included in the MAC address may be set to a specific value (for example, '1'). Can be.
  • the Sequence Control field is set to include a sequence number and a fragment number.
  • the sequence number may indicate a sequence number allocated to the corresponding MAC frame.
  • the fragment number may indicate the number of each fragment of the corresponding MAC frame.
  • the QoS Control field contains information related to QoS.
  • the QoS Control field may be included when indicating a QoS data frame in a subtype subfield.
  • the HT Control field includes control information related to the HT and / or VHT transmission / reception schemes.
  • the HT Control field is included in the Control Wrapper frame. In addition, it exists in the QoS data frame and the management frame in which the order subfield value is 1.
  • the frame body is defined as a MAC payload, and data to be transmitted in a higher layer is located, and has a variable size.
  • the maximum MPDU size may be 11454 octets
  • the maximum PPDU size may be 5.484 ms.
  • FCS is defined as a MAC footer and is used for error detection of MAC frames.
  • the first three fields (Frame Control field, Duration / ID field and Address 1 field) and the last field (FCS field) constitute the minimum frame format and are present in every frame. Other fields may exist only in a specific frame type.
  • FIG. 7 is a diagram illustrating a Frame Control field in a MAC frame in a wireless communication system to which the present invention can be applied.
  • the Frame Control field includes a Protocol Version subfield, a Type subfield, a Subtype subfield, a To DS subfield, a From DS subfield, and more fragments.
  • the Protocol Version subfield may indicate the version of the WLAN protocol applied to the corresponding MAC frame.
  • the Type subfield and the Subtype subfield may be set to indicate information for identifying a function of a corresponding MAC frame.
  • the type of the MAC frame may include three frame types: a management frame, a control frame, and a data frame.
  • Each frame type may be further divided into subtypes.
  • control frames include request to send (RTS) frames, clear-to-send (CTS) frames, acknowledgment (ACK) frames, PS-Poll frames, content free (End) frames, CF End + CF-ACK frame, Block Acknowledgment request (BAR) frame, Block Acknowledgment (BA) frame, Control Wrapper (Control + HTcontrol) frame, VHT null data packet notification (NDPA) It may include a Null Data Packet Announcement and a Beamforming Report Poll frame.
  • Management frames include beacon frames, announcement traffic indication message (ATIM) frames, disassociation frames, association request / response frames, reassociation requests / responses Response frame, Probe Request / Response frame, Authentication frame, Deauthentication frame, Action frame, Action No ACK frame, Timing Advertisement It may include a frame.
  • ATIM announcement traffic indication message
  • disassociation frames association request / response frames
  • reassociation requests / responses Response frame Probe Request / Response frame
  • Authentication frame Deauthentication frame
  • Action frame Action No ACK frame
  • Timing Advertisement It may include a frame.
  • the To DS subfield and the From DS subfield may include information necessary to interpret the Address 1 field or the Address 4 field included in the corresponding MAC frame header.
  • both the To DS subfield and the From DS subfield are set to '0'.
  • the To DS subfield and the From DS subfield are set to '1' and '0' in order if the frame is a QoS Management frame (QMF), and in order if the frame is not QMF. Both can be set to '0', '0'.
  • QMF QoS Management frame
  • the More Fragments subfield may indicate whether there is a fragment to be transmitted following the corresponding MAC frame. If there is another fragment of the current MSDU or MMPDU, it may be set to '1', otherwise it may be set to '0'.
  • the Retry subfield may indicate whether the corresponding MAC frame is due to retransmission of a previous MAC frame. In case of retransmission of the previous MAC frame, it may be set to '1', otherwise it may be set to '0'.
  • the power management subfield may indicate a power management mode of the STA. If the value of the Power Management subfield is '1', the STA may indicate switching to the power save mode.
  • the More Data subfield may indicate whether there is an additional MAC frame to be transmitted. If there is an additional MAC frame to be transmitted, it may be set to '1', otherwise it may be set to '0'.
  • the Protected Frame subfield may indicate whether the frame body field is encrypted. If the Frame Body field includes information processed by the encryption encapsulation algorithm, it may be set to '1', otherwise it may be set to '0'.
  • each field described above corresponds to an example of fields that may be included in the MAC frame, but is not limited thereto. That is, each field described above may be replaced with another field or additional fields may be further included, and all fields may not be necessarily included.
  • FIG. 8 illustrates the VHT format of the HT Control field in a wireless communication system to which the present invention can be applied.
  • the HT Control field includes a VHT subfield, an HT Control Middle subfield, an AC Constraint subfield, and a Reverse Direction Grant (RDG) / More PPDU (More PPDU). It may consist of subfields.
  • RDG Reverse Direction Grant
  • More PPDU More PPDU
  • the HT Control field for the VHT may be referred to as a VHT Control field.
  • the HT Control Middle subfield may be implemented to have a different format according to the indication of the VHT subfield. A more detailed description of the HT Control Middle subfield will be given later.
  • the AC Constraint subfield indicates whether a mapped AC (Access Category) of a reverse direction (RD) data frame is limited to a single AC.
  • the RDG / More PPDU subfield may be interpreted differently depending on whether the corresponding field is transmitted by the RD initiator or the RD responder.
  • the RDG / More PPDU field When transmitted by the RD initiator, the RDG / More PPDU field is set to '1' if the RDG exists, and set to '0' if the RDG does not exist. When transmitted by the RD responder, it is set to '1' if the PPDU including the corresponding subfield is the last frame transmitted by the RD responder, and set to '0' when another PPDU is transmitted.
  • the HT Control Middle subfield may be implemented to have a different format according to the indication of the VHT subfield.
  • the HT Control Middle subfield of the HT Control field for VHT includes a reserved bit, a Modulation and Coding Scheme feedback request (MRQ) subfield, and an MRQ Sequence Identifier (MSI).
  • STBC Space-time block coding
  • MCS MCS feedback sequence identifier
  • LSB Least Significant Bit
  • MSB MCS Feedback
  • MSB Group ID Most Significant Bit
  • Coding Type Subfield Feedback Transmission Type (FB Tx Type: Feedback transmission type) subfield and a voluntary MFB (Unsolicited MFB) subfield.
  • the MFB subfield may include a VHT number of space time streams (NUM_STS) subfield, a VHT-MCS subfield, a bandwidth (BW) subfield, and a signal to noise ratio (SNR). It may include subfields.
  • NUM_STS VHT number of space time streams
  • BW bandwidth
  • SNR signal to noise ratio
  • the NUM_STS subfield indicates the number of recommended spatial streams.
  • the VHT-MCS subfield indicates a recommended MCS.
  • the BW subfield indicates bandwidth information related to the recommended MCS.
  • the SNR subfield indicates the average SNR value on the data subcarrier and spatial stream.
  • each field described above corresponds to an example of fields that may be included in the MAC frame, but is not limited thereto. That is, each field described above may be replaced with another field or additional fields may be further included, and all fields may not be necessarily included.
  • IEEE 802.11 communication is fundamentally different from the wired channel environment because the communication takes place over a shared wireless medium.
  • CSMA / CD carrier sense multiple access / collision detection
  • the channel environment does not change so much that the receiver does not experience significant signal attenuation.
  • detection was possible. This is because the power sensed by the receiver is instantaneously greater than the power transmitted by the transmitter.
  • a variety of factors e.g., large attenuation of the signal depending on distance, or instantaneous deep fading
  • the transmitter cannot accurately perform carrier sensing.
  • a carrier sense multiple access with collision avoidance (CSMA / CA) mechanism is introduced as a basic access mechanism of a MAC.
  • the CAMA / 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 interval (eg, DCF Inter-Frame Space (DIFS)) prior to starting transmission.
  • DIFS DCF Inter-Frame Space
  • CCA Clear Channel Assessment
  • the AP and / or STA does not start its own transmission and assumes that several STAs are already waiting to use the medium.
  • the frame transmission may be attempted after waiting longer for a delay time (eg, a random backoff period) for access.
  • the STAs are expected to have different backoff period values, so that they will wait for different times before attempting frame transmission. This can minimize collisions.
  • 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 a large number of users
  • HCCA is 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. 9 is a diagram for explaining an arbitrary backoff period and a frame transmission procedure in a wireless communication system to which the present invention can be applied.
  • the random backoff count has a pseudo-random integer value and may be determined as one of values uniformly distributed in the range of 0 to a contention window (CW).
  • CW is a contention window parameter value.
  • the CW parameter is given CW_min as an initial value, but may take a double value when transmission fails (eg, when an ACK for a transmitted frame is not received). If the CW parameter value is CW_max, data transmission can be attempted while maintaining the CW_max value until the data transmission is successful. If the CW parameter value is successful, the CW parameter value is reset to the CW_min value.
  • the STA counts down the backoff slot according to the determined backoff count value and continuously monitors the medium during the countdown. If the media is monitored as occupied, the countdown stops and waits, and when the media is idle the countdown resumes.
  • the STA 3 may confirm that the medium is idle as much as DIFS and transmit the frame immediately.
  • each STA monitors and wait for the medium to be busy.
  • data may be transmitted in each of STA 1, STA 2, and STA 5, and each STA waits for DIFS when the medium is monitored in an idle state, and then backoff slots according to a random backoff count value selected by each STA. Counts down.
  • STA 2 selects the smallest backoff count value and STA 1 selects the largest backoff count value. That is, at the time when STA 2 finishes the backoff count and starts frame transmission, the remaining backoff time of STA 5 is shorter than the remaining backoff time of STA 1.
  • STA 1 and STA 5 stop counting and wait while STA 2 occupies the medium.
  • the STA 1 and the STA 5 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 STA 5 is shorter than that of STA 1, frame transmission of STA 5 is started.
  • STA 2 occupies the medium
  • data to be transmitted may also occur in STA 4.
  • the STA 4 waits for DIFS and then counts down the backoff slot according to the random backoff count value selected by the STA.
  • the remaining backoff time of STA 5 coincides with an arbitrary backoff count value of STA 4, and in this case, a collision may occur between STA 4 and STA 5. If a collision occurs, neither STA 4 nor STA 5 receive an ACK, and thus data transmission fails. In this case, STA4 and STA5 select a random backoff count value after doubling the CW value and perform countdown of the backoff slot.
  • the STA 1 may wait while the medium is occupied due to the transmission of the STA 4 and the STA 5, wait for DIFS when the medium is idle, and then start frame transmission after the remaining backoff time passes.
  • the CSMA / CA mechanism also 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 uses a Network Allocation Vector (NAV).
  • the NAV is a value that indicates to the other AP and / or STA how long the AP and / or STA currently using or authorized to use the medium remain until the medium becomes available. Therefore, 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 frame, and the STA receiving the NAV value is prohibited from accessing the medium during the period.
  • the NAV may be set according to a value of a duration field of the MAC header of the frame.
  • the AP and / or STA may perform a procedure of exchanging a request to send (RTS) frame and a clear to send (CTS) frame to indicate that the AP and / or STA want to access the medium.
  • the RTS frame and the CTS frame include information indicating a time interval in which a wireless medium required for transmission and reception of an ACK frame is reserved when substantial data frame transmission and acknowledgment (ACK) are supported.
  • the other STA that receives the RTS frame transmitted from the AP and / or the STA to which the frame is to be transmitted or receives the CTS frame transmitted from the STA to which the frame is to be transmitted during the time period indicated by the information included in the RTS / CTS frame Can be set to not access the medium. This may be implemented by setting the NAV during the time interval.
  • the time interval between frames is defined as Interframe Space (IFS).
  • IFS Interframe Space
  • the STA may determine whether the channel is used during the IFS time interval through carrier sensing.
  • Multiple IFSs are defined to provide a priority level that occupies a wireless medium in an 802.11 WLAN system.
  • FIG. 10 is a diagram illustrating an IFS relationship in a wireless communication system to which the present invention can be applied.
  • All timings can be determined with reference to the physical layer interface primitives, namely the PHY-TXEND.confirm primitive, the PHYTXSTART.confirm primitive, the PHY-RXSTART.indication primitive and the PHY-RXEND.indication primitive.
  • Frame spacing according to IFS type is as follows.
  • IFS timing is defined as the time gap on the medium. Except for AIFS, IFS timing is fixed for each physical layer.
  • SIFS is a PPDU containing a ACK frame, a CTS frame, a Block ACK Request (BlockAckReq) frame, or a Block ACK (BlockAck) frame that is an immediate response to an A-MPDU, the second or consecutive MPDU of a fragment burst, or PCF. Used for transmission of the STA's response to polling by and has the highest priority. SIFS can also be used for point coordinator of frames regardless of the type of frame during non-competition interval (CFP) time. SIFS represents the time from the end of the last symbol of the previous frame or the signal extension (if present) to the start of the first symbol of the preamble of the next frame.
  • CCP non-competition interval
  • SIFS timing is achieved when the transmission of consecutive frames at the TxSIFS slot boundary begins.
  • SIFS is the shortest of the IFS between transmissions from different STAs.
  • the STA occupying the medium may be used when it is necessary to maintain the occupation of the medium during the period in which the frame exchange sequence is performed.
  • PIFS is used to gain priority in accessing media.
  • PIFS can be used in the following cases:
  • TIM Traffic Indication Map
  • Hybrid Coordinator initiating CFP or Transmission Opportunity (TXOP)
  • HC or non-AP QoS STA which is a polled TXOP holder for recovering from the absence of expected reception in a controlled access phase (CAP)
  • the STA using the PIFS starts transmission after the CS (carrier sense) mechanism that determines that the medium is idle at the TxPIFS slot boundary.
  • DIFS may be used by a STA operative to transmit a data frame (MPDU) and a management frame (MMPDU: MAC Management Protocol Data Unit) under DCF.
  • the STA using the DCF may transmit on the TxDIFS slot boundary if it is determined that the medium is idle through a carrier sense (CS) mechanism after a correctly received frame and backoff time expire.
  • the correctly received frame means a frame in which the PHY-RXEND.indication primitive does not indicate an error and the FCS indicates that the frame is not an error (error free).
  • SIFS time 'aSIFSTime' and slot time 'aSlotTime' may be determined for each physical layer.
  • the SIFS time has a fixed value, but the slot time may change dynamically according to a change in the air delay time (aAirPropagationTime).
  • FIG. 11 is a diagram illustrating a downlink MU-MIMO transmission process in a wireless communication system to which the present invention can be applied.
  • MU-MIMO is defined in downlink from the AP to the client (ie, non-AP STA).
  • client ie, non-AP STA.
  • a multi-user frame is simultaneously transmitted to multiple receivers, but acknowledgments should be transmitted separately in the uplink.
  • Block Ack Request is sent in response to a frame.
  • the AP transmits a VHT MU PPDU (ie, preamble and data) to all receivers (ie, STA 1, STA 2, and STA 3).
  • the VHT MU PPDU includes a VHT A-MPDU transmitted to each STA.
  • STA 1 Receiving a VHT MU PPDU from the AP, STA 1 transmits a block acknowledgment (BA) frame to the AP after SIFS.
  • BA block acknowledgment
  • the AP After receiving the BA from the STA 1, the AP transmits a block acknowledgment request (BAR) frame to the next STA 2 after SIFS, and the STA 2 transmits a BA frame to the AP after SIFS.
  • BAR block acknowledgment request
  • the AP receiving the BA frame from STA 2 transmits the BAR frame to STA 3 after SIFS, and STA 3 transmits the BA frame to AP after SIFS.
  • the AP transmits the next MU PPDU to all STAs.
  • next generation WLAN system is a next generation WIFI system, which may be described as an example of IEEE 802.11ax as an embodiment of the next generation WIFI system.
  • HE High Efficiency
  • frames, PPDUs, and the like of the system are referred to as HE frames, HE PPDUs, HE preambles, HE-SIG fields, HE-STFs, and HE-LTFs. May be referred to.
  • the description of the existing WLAN system such as the above-described VHT system may be applied to the HE system, which is not further described below.
  • VHT-SIG A field VHT-STF, VHT-LTF and VHT-SIG-B fields described above for the HE-SIG A field, HE-STF, HE-LTF and HE-SIG-B fields. Description may apply.
  • the HE frame and the preamble of the proposed HE system may be used only for other wireless communication or cellular systems.
  • the HE STA may be a non-AP STA or an AP STA as described above. Although referred to as STA in the following specification, such a STA device may represent an HE STA device.
  • HE 12 illustrates a High Efficiency (HE) format PPDU according to an embodiment of the present invention.
  • FIGS. 12 (a) to (d) illustrate a more specific structure of the HE format PPDU.
  • a HE format PPDU for an HEW may be largely composed of a legacy part (L-part), an HE part (HE-part), and a data field (HE-data).
  • L-part legacy part
  • HE-part HE part
  • HE-data data field
  • the L-part is composed of an L-STF field, an L-LTF field, and an L-SIG field in the same manner as the conventional WLAN system maintains.
  • the L-STF field, L-LTF field, and L-SIG field may be referred to as a legacy preamble.
  • the HE-part is a part newly defined for the 802.11ax standard and may include an HE-STF field, an HE-SIG field, and an HE-LTF field.
  • 12 (a) illustrates the order of the HE-STF field, the HE-SIG field, and the HE-LTF field, but may be configured in a different order.
  • HE-LTF may be omitted.
  • the HE-SIG field may be collectively referred to as HE-preamble.
  • the L-part, the HE-SIG field, and the HE-preamble may be collectively referred to as a physical preamble (PHY) / physical preamble.
  • the HE-SIG field may include information (eg, OFDMA, UL MU MIMO, enhanced MCS, etc.) for decoding the HE-data field.
  • information eg, OFDMA, UL MU MIMO, enhanced MCS, etc.
  • the L-part and the HE-part may have different fast fourier transform (FFT) sizes (ie, subcarrier spacing), and may use different cyclic prefixes (CP).
  • FFT fast fourier transform
  • CP cyclic prefixes
  • 802.11ax systems can use FFT sizes that are four times larger than legacy WLAN systems. That is, the L-part may have a 1 ⁇ symbol structure, and the HE-part (particularly, HE-preamble and HE-data) may have a 4 ⁇ symbol structure.
  • 1 ⁇ , 2 ⁇ , 4 ⁇ size FFTs represent relative sizes for legacy WLAN systems (eg, IEEE 802.11a, 802.11n, 802.11ac, etc.).
  • the FFT size used for the L-part is 64, 128, 256, and 512 at 20 MHz, 40 MHz, 80 MHz, and 200 MHz, respectively
  • the FFT size used for the HE-part is 256 at 20 MHz, 40 MHz, 80 MHz, and 200 MHz, respectively. , 512, 1024, 2048.
  • the number of subcarriers per unit frequency increases because the subcarrier frequency spacing becomes smaller, but the OFDM symbol length becomes longer.
  • the use of a larger FFT size means that the subcarrier spacing becomes narrower, and similarly, an Inverse Discrete Fourier Transform (IDFT) / Discrete Fourier Transform (DFT) period is increased.
  • IDFT Inverse Discrete Fourier Transform
  • DFT Discrete Fourier Transform
  • the IDFT / DFT period may mean a symbol length excluding the guard period (GI) in the OFDM symbol.
  • the subcarrier spacing of the HE-part is 1/4 of the subcarrier spacing of the L-part.
  • the ID-FT / DFT period of the HE-part is four times the IDFT / DFT period of the L-part.
  • the GI can be one of 0.8 ⁇ s, 1.6 ⁇ s, 3.2 ⁇ s, so the OFDM symbol length (or symbol interval) of the HE-part including the GI is 13.6 ⁇ s, 14.4 ⁇ s, 20 according to the GI. It can be
  • the HE-SIG field may be divided into an HE-SIG-A field and an HE-SIG-B field.
  • the HE-part of the HE format PPDU may include a HE-SIG-A field having a length of 12.8 kHz, a HE-STF field of 1 OFDM symbol, one or more HE-LTF fields, and a HE-SIG-B field of 1 OFDM symbol. It may include.
  • the FFT having a size four times larger than the existing PPDU may be applied from the HE-STF field. That is, FFTs of 256, 512, 1024, and 2048 sizes may be applied from the HE-STF field of the HE format PPDU of 20 MHz, 40 MHz, 80 MHz, and 200 MHz, respectively.
  • the HE-SIG when the HE-SIG is divided into the HE-SIG-A field and the HE-SIG-B field and transmitted as shown in FIG. 12 (b), the positions of the HE-SIG-A field and the HE-SIG-B field are shown in FIG. It may differ from 12 (b).
  • the HE-SIG-B field may be transmitted after the HE-SIG-A field
  • the HE-STF field and the HE-LTF field may be transmitted after the HE-SIG-B field.
  • an FFT of 4 times larger than a conventional PPDU may be applied from the HE-STF field.
  • the HE-SIG field may not be divided into an HE-SIG-A field and an HE-SIG-B field.
  • the HE-part of the HE format PPDU may include a HE-STF field of one OFDM symbol, a HE-SIG field of one OFDM symbol, and one or more HE-LTF fields.
  • the HE-part may be applied to an FFT four times larger than the existing PPDU. That is, FFTs of 256, 512, 1024, and 2048 sizes may be applied from the HE-STF field of the HE format PPDU of 20 MHz, 40 MHz, 80 MHz, and 200 MHz, respectively.
  • the HE-SIG field is not divided into an HE-SIG-A field and an HE-SIG-B field, and the HE-LTF field may be omitted.
  • the HE-part of the HE format PPDU may include a HE-STF field of 1 OFDM symbol and a HE-SIG field of 1 OFDM symbol.
  • the HE-part may be applied to an FFT four times larger than the existing PPDU. That is, FFTs of 256, 512, 1024, and 2048 sizes may be applied from the HE-STF field of the HE format PPDU of 20 MHz, 40 MHz, 80 MHz, and 200 MHz, respectively.
  • the HE format PPDU for the WLAN system according to the present invention may be transmitted on at least one 20 MHz channel.
  • an HE format PPDU can be transmitted in a 40 MHz, 80 MHz or 200 MHz frequency band using a total of four 20 MHz channels. This will be described in more detail with reference to the drawings below.
  • FIG. 13 is a diagram illustrating an HE format PPDU according to an embodiment of the present invention.
  • FIG. 13 illustrates a PPDU format when 80 MHz is allocated to one STA (or OFDMA resource units are allocated to a plurality of STAs within 80 MHz) or when different streams of 80 MHz are allocated to a plurality of STAs.
  • L-STF, L-LTF, and L-SIG may be transmitted as OFDM symbols generated based on 64 FFT points (or 64 subcarriers) in each 20MHz channel.
  • the HE-SIG-A field may include common control information that is commonly transmitted to STAs receiving a PPDU.
  • the HE-SIG-A field may be transmitted in one to three OFDM symbols.
  • the HE-SIG-A field is copied in units of 20 MHz and contains the same information.
  • the HE-SIG-A field informs the total bandwidth information of the system.
  • the HE-SIG-A field may include information as shown in Table 1 below.
  • each field described above corresponds to an example of fields that may be included in the PPDU, but is not limited thereto. That is, each field described above may be replaced with another field or additional fields may be further included, and all fields may not be necessarily included.
  • HE-STF is used to improve the performance of AGC (Automatic Gain Control) estimation in MIMO transmission.
  • HE-STF may be generated using a sequence of frequency domains for a particular band.
  • Long Trainig Field HE-LTF is a field used at the receiver to estimate the MIMO channel between the receive chains and the set of constellation mapper outputs.
  • the HE-SIG-B field may include user-specific information required for each STA to receive its own data (eg, PSDU).
  • PSDU user-specific information required for each STA to receive its own data
  • the HE-SIG-B field may be transmitted in one or two OFDM symbols.
  • the HE-SIG-B field may include information on the modulation and coding scheme (MCS) of the corresponding PSDU and the length of the corresponding PSDU.
  • MCS modulation and coding scheme
  • the L-STF, L-LTF, L-SIG, and HE-SIG-A fields may be repeatedly transmitted in units of 20 MHz channels. For example, when a PPDU is transmitted on four 20 MHz channels (i.e., 80 MHz band), the L-STF, L-LTF, L-SIG and HE-SIG-A fields may be repeatedly transmitted on every 20 MHz channel. have.
  • legacy STAs supporting legacy IEEE 802.11a / g / n / ac may not be able to decode the HE PPDU.
  • the L-STF, L-LTF, and L-SIG fields are transmitted through a 64 FFT on a 20 MHz channel so that the legacy STA can receive them.
  • the L-SIG field may occupy one OFDM symbol, one OFDM symbol time is 4 ms, and a GI may be 0.8 ms.
  • the FFT size for each frequency unit may be larger from the HE-STF (or HE-SIG-A). For example, 256 FFTs may be used in a 20 MHz channel, 512 FFTs may be used in a 40 MHz channel, and 1024 FFTs may be used in an 80 MHz channel. As the FFT size increases, the number of OFDM subcarriers per unit frequency increases because the interval between OFDM subcarriers becomes smaller, but the OFDM symbol time becomes longer. In order to improve the efficiency of the system, the length of the GI after the HE-STF may be set equal to the length of the GI of the HE-SIG-A.
  • the HE-SIG-A field may include information required for the HE STA to decode the HE PPDU.
  • the HE-SIG-A field may be transmitted through a 64 FFT in a 20 MHz channel so that both the legacy STA and the HE STA can receive it. This is because the HE STA can receive not only the HE format PPDU but also the existing HT / VHT format PPDU, and the legacy STA and the HE STA must distinguish between the HT / VHT format PPDU and the HE format PPDU.
  • FIG. 14 is a diagram illustrating an HE format PPDU according to an embodiment of the present invention.
  • the FFT size per unit frequency may be larger from the HE-STF (or HE-SIG-B).
  • 256 FFTs may be used in a 20 MHz channel
  • 512 FFTs may be used in a 40 MHz channel
  • 1024 FFTs may be used in an 80 MHz channel.
  • the HE-SIG-B field may include information specific to each STA, but may be encoded over the entire band (ie, indicated by the HE-SIG-A field). That is, the HE-SIG-B field includes information on all STAs and may be transmitted so that all STAs receive.
  • the HE-SIG-B field may inform frequency bandwidth information allocated to each STA and / or stream information in a corresponding frequency band.
  • the HE-SIG-B may be allocated 20 MHz for STA 1, 20 MHz for STA 2, 20 MHz for STA 3, and 20 MHz for STA 4.
  • STA 1 and STA 2 may allocate 40 MHz, and STA 3 and STA 4 may then allocate 40 MHz.
  • STA 1 and STA 2 may allocate different streams, and STA 3 and STA 4 may allocate different streams.
  • the HE-SIG C field may be added to the example of FIG. 14.
  • the HE-SIG-B field information on all STAs may be transmitted over the entire band, and control information specific to each STA may be transmitted in units of 20 MHz through the HE-SIG-C field.
  • the HE-SIG-C field may be transmitted after the HE-LTF field.
  • the HE-SIG-B field may be transmitted in units of 20 MHz in the same manner as the HE-SIG-A field without transmitting over the entire band. This will be described with reference to the drawings below.
  • FIG. 15 is a diagram illustrating a HE format PPDU according to an embodiment of the present invention.
  • the HE-SIG-B field is not transmitted over the entire band, but is transmitted in 20 MHz units in the same manner as the HE-SIG-A field. However, at this time, the HE-SIG-B is encoded and transmitted in 20 MHz units differently from the HE-SIG-A field, but may not be copied and transmitted in 20 MHz units.
  • the FFT size per unit frequency may be larger from the HE-STF (or HE-SIG-B).
  • 256 FFTs may be used in a 20 MHz channel
  • 512 FFTs may be used in a 40 MHz channel
  • 1024 FFTs may be used in an 80 MHz channel.
  • the HE-SIG-A field is duplicated and transmitted in units of 20 MHz.
  • the HE-SIG-B field may inform frequency bandwidth information allocated to each STA and / or stream information in a corresponding frequency band. Since the HE-SIG-B field includes information about each STA, information about each STA may be included for each HE-SIG-B field in units of 20 MHz. In this case, in the example of FIG. 15, 20 MHz is allocated to each STA. For example, when 40 MHz is allocated to the STA, the HE-SIG-B field may be copied and transmitted in units of 20 MHz.
  • the data field is a payload and may include a service field, a scrambled PSDU, tail bits, and padding bits.
  • the HE format PPDU as shown in FIGS. 13 to 15 may be identified through a RL-SIG (Repeated L-SIG) field, which is a repetitive symbol of the L-SIG field.
  • the RL-SIG field is inserted before the HE SIG-A field, and each STA may identify the format of the received PPDU as the HE format PPDU using the RL-SIG field.
  • FIG. 16 shows an HE frame structure according to an embodiment of the present invention.
  • the 802.11ax system intends to use symbol lengths four times longer than legacy 802.11 systems (802.11a, 802.11n, 802.11ac, etc.) for average throughput enhancement and robust transmission in the outdoor. . That is, the STA may apply a FFT size four times larger when performing OFDM modulation.
  • FIG. 16 illustrates an HE signal frame structure according to an embodiment.
  • a section four times longer in symbol length is represented by a four times (4x) FFT size.
  • the L-part or legacy preamble in the signal frame may use the same FFT size 1x as the legacy system.
  • a 1x FFT size may be applied to the HE-SIG field
  • a 4x FFT size may be applied to the HE-STF, HE-LTF, and HE-data parts.
  • the embodiment of FIG. 16 may be used in combination with the embodiment of FIGS. 12 to 15.
  • the number of subcarriers of the transmission signal is increased compared to the 802.11 legacy system signal, thereby improving throughput.
  • the time required to process data may be increased. Therefore, if the predefined SIFS time is used as it is, the receiving STA may not transmit the ACK frame after the determined SIFS time.
  • SIFSTime is as follows.
  • SIFSTime aRxPHYDelay + aMACPRocessingDelay + aTxPHYDelay + aRxTxSwitchTime + aTxRampOnTime
  • aRxPHYDelay The nominal time (in microseconds) that PHY uses to deliver the last bit of a received from the end of the last symbol on the air interface to the MAC layer. frame from end of the last symbol at the air interface to the MAC.
  • aMACProcessingDelay The maximum time (in microseconds) available for the MAC to issue a PHY-TXSTART.request primitive pursuant to PHY-RXEND .indication primitive (for response after SIFS) or PHY-CCA.indication (IDLE) primitive (for response at any slot boundary following a SIFS))
  • aTxPHYDelay The norminal time (in microseconds) that the PHY uses to deliver a symbol from the MAC interface to the air interface
  • aRxTxSwitchTime The nominal time (in microseconds) that PHY takes to switch form receive to transmit
  • aTxRampOnTime The maximum time (in microseconds) that the PHY takes to turn the Transmitter on.
  • the transmitting STA may determine that the receiving STA did not receive the data because the receiving STA did not receive the ACK after the SIFS time even though the receiving STA received the data well. Therefore, a description will now be given of a method of classifying the capability of the HE-STA, adding a padding symbol in association with the MCS level and data rate, and instructing the HE-STA about the padding symbol.
  • padding symbols may be referred to as dummy symbols, signal extension symbols, or packet extension symbols.
  • at least one PE (Packet Extension) symbol included in the PPDU may be referred to as a PE field.
  • the PE field may include at least one PE symbol.
  • the receiver may set the signal extension symbol interval to a processing time additionally necessary for data decoding without decoding the signal extension symbol.
  • the signal extension symbol is an OFDM symbol, and may be any signal that OBSS STAs can determine that the channel is occupied through energy detection. Alternatively, the STA may not transmit any signal in a specific section of the signal frame instead of transmitting the signal extension symbol. In this case, however, additional RF or baseband chains may be required to generate the signal.
  • a description will be given of an embodiment of using a dummy symbol, which is an OFDM symbol capable of setting an NAV until an increased signal processing time.
  • the dummy symbol Since the dummy symbol is inserted after the last data symbol, the dummy symbol may be referred to as a padding symbol.
  • the transmission signal since the transmission signal is extended by the addition of the dummy symbol, it may be referred to as a signal extension symbol or an extension signal.
  • the present invention intends to add a signal extension symbol in consideration of the performance of the STA, and therefore, the transmitting STA must know the performance of the receiving STA. Therefore, the following describes a method of classifying and signaling STA performance.
  • the performance of the HE STA may be classified into N.
  • the performance of the HE STA may be directly classified according to the decoding performance in the manufacturing process of the STA.
  • the HE STA may be indirectly classified by various parameters used when transmitting and receiving a signal.
  • Parameters that can be used to distinguish the performance of the HE STA may be represented as follows, and the performance may be distinguished through at least one of these parameters or a combination thereof. However, these parameters are embodiments, and thus, the entire parameters may be changed, such as an included parameter is excluded or another parameter is added.
  • four categories of STAs may be classified based on the maximum MCS level parameter and the maximum bandwidth size parameter supported by the STA.
  • Table 2 shows four categories of STAs thus classified.
  • the transmitting STA Since the classified STA category information is necessary to determine whether the signal extension symbol is padded and the amount of the signal extension symbol to be padded in the transmitting STA, the transmitting STA must acquire STA category information of the receiving STA. Therefore, STA category information should be included in the signals transmitted and received between the STAs.
  • the STA category information may be included in the HE Capability Element and transmitted.
  • the HE performance element may include a beacon frame of an AP or a probe response frame of an STA, an association request frame, an association response frame, a reassociation request frame, and a reassociation. It may be included in a Reassociatoin Response frame.
  • FIG 17 illustrates a VHT performance element according to an embodiment of the invention.
  • the HE performance element may be designed with the same or similar structure as the VHT performance element.
  • the HE STA may declare that it is the HE STA by transmitting an HE Capability Element.
  • the HE capability element may include an HE Capability Info field as shown in FIG. 17.
  • the embodiment of FIG. 17 employs the VHT capability information field as an example, and information included in the embodiment may be changed.
  • the last 30 to 31 bits of the HE performance information field are reserved bits, and the present invention may transmit STA category information using these reserved bits.
  • Maximum MPDU Length indicates the maximum MPDU length field.
  • Supported Channel Width Set Supported channel width set information and indicates a channel width supported by the corresponding STA.
  • Rx LDPC Receives LDPC information, indicating support for receiving LDPC encoded packets.
  • Short GI for 80MHz indicates short GI information for 80MHz and whether short GI is supported for received packets.
  • Short GI for 80 + 80MHz indicates short GI information about 80 + 80MHz and whether short GI is supported for received packets.
  • Tx STBC Transmission STBC information, indicating whether transmission of at least 2x1 STBC is supported
  • Rx STBC Receive STBC information, indicating whether PPDU using STBC is supported.
  • SU Beamformer Capable Indicates whether or not the SU beamformer performance information, such as SU beamformer (VHT sounding protocol), is supported.
  • SU Beamformee Capable Indicates whether or not the SU beamformee performance information, such as SU beamformee (VHT sounding protocol), is supported.
  • Beamformee STS capability Beamformee STS capability information, which indicates the maximum number of space-time streams that the STA can receive.
  • Number of Sounding Dimensions Number of sounding dimensions, indicating beamformer performance
  • -MU Beamformer Capable indicates whether or not the operation such as MU beamformer performance information and MU beamformer (VHT sounding protocol) are supported.
  • MU Beamformee Capable indicates whether or not operations such as MU beamformee performance information and MU beamformee (VHT sounding protocol) are supported.
  • VHT (HE) TXOP PS Indicates whether the AP supports the VHT (HE) TXOP power save mode or whether the VHT (HE) -TXOP power save mode of the non-AP STA is enabled.
  • HTC-VHT-Capable HTC-VHT (HE) performance information, indicating whether the STA supports reception of the VHT variable HT control field.
  • Maximum A-MPDU Length Exponent Maximum A-MPDU length exponent information, indicating the maximum length of the A-MPDU that the STA can receive.
  • VHT (HE) Link Adaptation Capable VHT (HE) link adaptation performance information, indicating whether the STA supports link adaptation using the VHT variable HT control field.
  • Rx Antenna Pattern Consistency indicates the possibility of changing the receiving antenna pattern
  • Tx Antenna Patern Consistency indicates the possibility of changing the transmit antenna pattern
  • the STA may use a method of separately indicating the STA category information by using the aforementioned reserved bits.
  • the STA may calculate the STA category using the information of the above-described subfields configuring the HE performance element or the VHT performance element without allocating additional bits.
  • the STA includes information included in the performance element Maximum MPDU length, supported channel width set, Rx LDPC, Beamformee STS capability, Number of Sounding Dimensions, Maximum A-MPDU length exponent, Rx MCS Map, Rx Highest Supported Long GI
  • An STA category may be obtained using at least one of information such as a data rate, a Tx MCS map, and a Tx Highest Supported Long GI Data Rate. That is, the STA may receive / acquire signaling information about the receiving STA and obtain category information of the receiving STA therefrom.
  • the STA category may be indirectly calculated as shown in Table 2. If the HE performance element is designed similar to the VHT performance element, the STA category may be indirectly calculated as shown in Table 2. At this time, 256QAM Support (MCS-8, 9) may be obtained from the received HE-MCS Map information, and 160MHz and 80 + 80MHz support may be obtained from an HE Capability Info Field.
  • MCS-8, 9 256QAM Support
  • 160MHz and 80 + 80MHz support may be obtained from an HE Capability Info Field.
  • the transmitting STA may pad the signal extension symbol based on the category of the receiving STA and the MCS level, constellation level, or data rate of the currently transmitted data frame.
  • the MCS level indicates the MCS level (constellation level) that the STA signals through the HE-SIG field of the physical preamble when transmitting data.
  • the MCS level includes the constellation level, and the present invention may perform an operation using only the constellation level in the MCS level.
  • the signal extension symbol may be generated in the same manner as a multiplexing method for transmitting data, but may be generated in consideration of dummy bits or dummy symbols.
  • Bits filling the signal extension symbol may be generated by using specific bit values without repeatedly inserting the same value in consideration of PAPR (Peak to Average Power Ratio) performance.
  • Random bit values may be used.
  • such random bits may be generated using a PN sequence, and the seed value may use a predefined value, but may use all or part of an AID, Partial AID, or Group ID.
  • Predefined bit sequences may be used.
  • the predefined sequence may be a sequence generated / applied in consideration of the PAPR performance of the system.
  • modulation symbols may be generated and used directly.
  • This signal extension symbol may be selected as a structure in consideration of the PAPR performance.
  • the modulation order may be QPSK.
  • a predetermined value may be used for the modulation order (e.g. BPSK, QPSK).
  • the STA may modulate the signal extension symbol using a modulation order defined in the L-SIG or HE-SIG field or used for data transmission.
  • the STA may use a predefined modulation order regardless of the modulation order defined in the L-SIG or HE-SIG field or used for data transmission.
  • the STA may modulate the padding symbol using the FFT size and CP length defined in the L-SIG or HE-SIG field or used for data transmission.
  • the STA may use the predefined FFT size and CP length regardless of the FFT size and CP length defined in the L-SIG or HE-SIG field or used for data transmission.
  • the signal extension symbol may be transmitted without inserting a CP in consideration of being a dummy symbol.
  • the length of the signal extension symbol may be set equal to the length of the data symbol.
  • the HE STA of the 802.11ax system may use an OFDM symbol that is four times longer than the OFDM symbol period (or FFT size) used in 802.11a / n / ac. Therefore, the 4x OFDM symbol, which is four times longer than the data symbol, may be used as the signal extension symbol.
  • the length of the signal extension symbol may be set differently from the length of the data symbol.
  • the HE STA of the 802.11ax system may use an OFDM symbol that is four times longer than the OFDM symbol period (or FFT size) used in 802.11a / n / ac.
  • a 1x / 2x / 3x OFDM symbol having a period 1, 2, or 3 times may be used, unlike a data symbol.
  • the STA sets the subcarrier spacing to be four times, two times, or four thirds larger than the data symbols, but only to have an FFT size to have the same system bandwidth. Can be set to 1/4, 2/4, and 3/4 times.
  • a signal extension symbol having periods of 1x, 2x, and 3x may be generated by using a point in which repetitive characteristics occur in the time domain. For example, using a subcarrier spacing applied to a data symbol and an FFT size, and inserting three zeros for each subcarrier, a signal repeated four times in the time domain is generated and one to three of the four samples are generated. By using the sample, signal extension symbols having a period of 1x to 3x can be generated.
  • 18 shows a signal extension symbol including samples repeated four times in the time domain.
  • 18 shows a signal repeated four times using s modulation symbols d (0), d (1), ..., d (K-1) and performing three zero insertions. , s (1), ..., s (N-1)).
  • signal extension symbols having a 1x period can be generated.
  • the STA may generate n OFDM symbols when the FFT size of the transmission data is 4x, and may not generate a padding symbol when the FFT size of the transmission data is 1x or 2x.
  • the number n of padding symbols may be determined by the aforementioned STA category.
  • the number of padding symbols of STA category 1 may be set to 3, the number of padding symbols of STA category 2 is 2, the number of padding symbols of STA category 3 is 1, and the number of padding symbols of STA category 4 is 0.
  • some STA categories include a padding symbol number of STA category 1, a padding symbol number of STA category 2, a padding symbol number of STA category 3 of 1, and a padding symbol number of STA category 4 of 0 in some STA categories.
  • the same number of padding symbols may be used for.
  • the STA may use the STBC scheme for data transmission and generate n padding symbols when the FFT size of the transmission data is 4x, and may not generate padding symbols when the FFT size of the transmission data is 2x and 1x.
  • the number n of padding symbols may be determined by the aforementioned STA category.
  • the number of padding symbols of STA category 1 may be set to 3, the number of padding symbols of STA category 2 is 2, the number of padding symbols of STA category 3 is 1, and the number of padding symbols of STA category 4 is 0.
  • some STA categories include a padding symbol number of STA category 1, a padding symbol number of STA category 2, a padding symbol number of STA category 3 of 1, and a padding symbol number of STA category 4 of 0 in some STA categories.
  • the same number of padding symbols may be used for.
  • the STA uses the STBC method for data transmission and generates 2n padding symbols when the FFT size of the transmission data is 4x, and generates n padding symbols when the FFT size of the transmission data is 2x, and the FFT size of the transmission data is In the case of 1x, the padding symbol may not be generated.
  • the number n of padding symbols may be determined by the aforementioned STA category.
  • the number of padding symbols of STA category 1 may be set to 3, the number of padding symbols of STA category 2 is 2, the number of padding symbols of STA category 3 is 1, and the number of padding symbols of STA category 4 is 0.
  • some STA categories include a padding symbol number of STA category 1, a padding symbol number of STA category 2, a padding symbol number of STA category 3 of 1, and a padding symbol number of STA category 4 of 0 in some STA categories.
  • the same number of padding symbols may be used for.
  • the STA may use the STBC scheme for data transmission and generate 2n padding symbols when the FFT size of the transmission data is 4x, and may not generate the padding symbol when the FFT size of the transmission data is 2x or 1x.
  • the number n of padding symbols may be determined by the aforementioned STA category.
  • the number of padding symbols of STA category 1 may be set to 3, the number of padding symbols of STA category 2 is 2, the number of padding symbols of STA category 3 is 1, and the number of padding symbols of STA category 4 is 0.
  • some STA categories include a padding symbol number of STA category 1, a padding symbol number of STA category 2, a padding symbol number of STA category 3 of 1, and a padding symbol number of STA category 4 of 0 in some STA categories.
  • the same number of padding symbols may be used for.
  • the transmission data may be transmitted in a non-STBC PPDU.
  • the transmitting STA may generate a padding symbol, that is, a signal extension symbol.
  • whether to insert the signal extension symbol in the transmission STA may be determined based on the STA category of the receiver, the MCS level for the transmission data, or the data generator.
  • the transmitting STA may determine whether to insert the signal extension symbol based on at least one of a category of the receiving STA, an MCS level of the transmission data, and a data rate of the transmission data.
  • the MCS level may include ten steps as shown in Table 3, but according to the embodiment, the MCS level of the 802.11ax system may be further added.
  • the STA may determine whether to insert the signal extension symbol based on the MCS level or may consider the data rate.
  • the transmitting STA may determine whether to add a padding symbol as shown in Tables 4 and 5.
  • Table 4 shows an embodiment of determining whether to add a signal extension symbol by using an STA category and an MCS level.
  • the receiving STA is the STA category 1
  • the MCS level is 3 to 9
  • the STA category 2 is the MCS level to 5 to 9
  • the STA category 3 is the MCS level to 8 to 9
  • the signal may be transmitted by adding a padding symbol.
  • Table 5 shows an embodiment of determining whether to add a padding symbol by using an STA category and a data rate.
  • the transmitting STA is STA category 3 when the receiving STA is STA category 1 and STA category 3 when the data rate is more than 2400 (Mb / s).
  • a signal may be transmitted by adding a padding symbol for a case where the data rate is more than 3600 (Mb / s).
  • the tail bit (s) may be used to initialize the state of the encoder.
  • the STA performs FEC coding during data processing, in which case a convolutional encoder may be used.
  • 19 illustrates a PPDU including tail bits according to an embodiment of the present invention.
  • a tail field may be inserted at the end of the last symbol of the PPDU.
  • the tail field may include six nonscrambled zero bits. These bits return the convolutional encoder to zero and may be referred to as tail bits.
  • the transmit signal includes the signal extension symbol
  • the receiving STA does not decode the signal extension symbol. Therefore, the receiver may not use the tail bits after the signal extension symbol, which may cause encoding / decoding performance degradation.
  • the present invention proposes a new position of the tail field.
  • FIG. 20 illustrates a configuration of a PPDU including a tail field according to an embodiment of the present invention.
  • the STA generates a PPDU, in which case the tail field (tail bits) may be located at the end of the last data symbol of the PPDU rather than the last symbol of the PPDU. Accordingly, the STA may secure signal processing time at the receiving side by adding a signal extension symbol while initializing the convolutional encoder state at the end of the data symbol to maintain encoding performance.
  • the information bits do not exactly match the number of bits that can be transmitted in one OFDM symbol.
  • Information bits may be referred to as coded bits or payload bits.
  • the STA may adjust the number of bits that can be transmitted in one OFDM symbol by performing PHY padding or MAC padding.
  • the STA adds MAC padding bits, PHY padding bits, and tail bits (in the case of a convolutional encoder use) to adjust the number of bits, i.e., the data size, so that all subcarriers of the last OFDM symbol can be used. I can fill it.
  • the receiving STA knows the number of information bits or the data length in one OFDM symbol, the remaining part (padding bits to fill the number of bits of the OFDM symbol) may not be decoded.
  • the padding bits can also be used as additional time for decoding, such as signal extension symbols.
  • the signal should include post-FEC padding bits. This is because post FEC padding does not cause any problem in received signal processing even without decoding.
  • the receiving STA uses both the padding bits and the signal extension symbol interval after the payload as an additional processing time for data decoding.
  • the receiving STA may utilize not only the interval of the signal extension symbol but also the interval of the padding bits of the last data symbol as an additional processing time.
  • the length of the signal extension symbol may be set shorter in consideration of the transmission interval of the padding bits. Therefore, it is possible to reduce the power consumption and overhead due to the transmission and reception of signal extension symbols from the system side.
  • the padding pits in FIG. 21 represent post-FEC padding bits.
  • FIG. 22 illustrates a configuration and available processing time of a PPDU according to an additional embodiment of the present invention.
  • the receiving STA may use the interval of the padding bits as an additional decoding time by excluding the corresponding padding bits from the FEC decoding.
  • the tail field is preferably located after the last information bits of the last data symbol instead of the last of the last data symbol, that is, at the end of the payload data. In Figure 22, the tail bits are located at the end of the payload of the last data symbol.
  • the receiver in order to use the section in which the padding bits are transmitted as the PHY processing time of the additional receiver, the receiver must know the length of the information bits (payload length).
  • payload length the length of the information bits
  • the transmitting STA may not directly signal the length of the information bits, and the receiving STA may calculate the length of the information bits using the received signaling information.
  • the STA may calculate the length of the information bits using the length field transmitted to the L-SIG and the length or number of signal extension symbols for performing the above-described decoding processing.
  • the payload length (or coded bits + pre-FEC padding + tail bits length) in the last OFDM symbol in the HE-SIG-A / B / C field
  • the length of the telegram bits can be calculated using the corresponding information and the length / number of signal extension symbols required for decoding processing.
  • the transmitting STA may determine a specific section of the last data symbol and transmit information on the section. For example, pre-FEC padding may be performed such that coded bits and tail bits that are transmitted in the last data symbol (12.8 ⁇ s) correspond to multiples of 3.2 ⁇ s. In other words, the transmitting STA may configure a signal such that the coded bits or the payload size occupy the boundary of one of the quadrants of the last data symbol. In an embodiment, the unit boundary may correspond to 1/2, 1/3, or 2/3 of the last data symbol.
  • FIG. 23 is a PPDU configuration method according to an embodiment of the present invention, and particularly, a configuration method of the last data symbol.
  • Figure 23 divides the last data symbol into quadrants of 3.2 ⁇ s and signals the payload, pre-FEC padding and tail bits to coincide with unit boundaries of 1/4, 2/4, 3/4 and 4/4. It shows how to construct.
  • the transmitting STA has a payload size at the end of the 3/4 boundary when the payload size (coded bits and tail bits) comes between 2/4 to 3/4 boundaries of the last data OFDAM symbol.
  • the pre-FEC padding bits can be inserted such that N is correct.
  • the transmitting STA may transmit information indicating a payload length (or coded bits + pre-FEC padding + tail bits) in an OFDM symbol through a HE-SIG field (HE-SIG A / B / C). have.
  • the information indicating the payload length may indicate boundary values corresponding to 1/4, 2/4, 3/4, and 4/4 points of the last data symbol as boundary information.
  • the boundary information may be used by 2 bits to indicate four values, that is, four boundaries as 00, 01, 10, and 11, respectively. In this case, when payload length is indicated by four boundary values, the boundary information indicates a symbol interval in a unit of 3.2 ⁇ s. Alternatively, the payload length may be indicated by two intervals. When the payload length is indicated in two intervals, the transmitting STA may use 1 bit and indicate the payload length in units of 6.4 ⁇ s.
  • the boundary information may be referred to as decoding boundary information.
  • the transmitting STA may insert pre-FEC padding bits and tail bits after bits coded such that the payload length fits into 1/4, 2/4, 3/4, and 4/4 boundaries. have. If the payload length corresponds to a boundary of 1/4, 2/4, or 3/4, the transmitting STA may fill the remaining portion of the last data symbol with padding bits. May correspond to FEC bits.
  • the transmitting STA may reduce the length of the signal extension symbol in consideration of the transmission time of the padding bits. That is, the transmitting STA may generate a new signal extension symbol with a shorter period by subtracting the transmission time of the padding bits from the n signal extension symbols. For example, a payload including pre-FEC padding, in which case four signal extension symbols having a 1x period (1/4 OFDM samples) must be added in order to secure a time for a specific STA to process a received signal. When the length of the 2/4 OFDM symbol period, the transmitting STA can transmit a signal by generating and adding only two signal extension symbols having a 1x period.
  • the transmitting STA may transmit a signal by generating and adding one signal extension symbol having a 2x period.
  • the length field of the L-SIG field of the transmitted signal may indicate a multiple of at least 4 ⁇ s longer than the length of the signal extension symbol (min (4 * i ⁇ s ⁇ PSDU duration). Insertion of the signal extension symbol Whether or not to insert the signal extension symbols calculated through the HE capability can be determined.
  • FIG. 24 illustrates a method for a receiving STA to obtain a length of a payload using a length field of an L-SIG according to an embodiment of the present invention.
  • the transmitting STA may indicate the length of the transmission signal in the length field of the L-SIG field.
  • the length field of the L-SIG field may indicate a minimum unit length of 4 ⁇ s longer than the signal extension symbol length.
  • the length field of the L-SIG field may indicate a value of 6 or a sixth unit of 4 ⁇ s.
  • the receiving STA if it does not explicitly indicate the payload length (or coded bits + pre-FEC padding + tail bits) in the last OFDM symbol in the HE-SIG-A / B / C field Can implicitly obtain the length / number of the signal extension symbol and the payload length (or coded bits + pre-FEC padding + tail bits).
  • the transmitting STA indicates the length information of the L-SIG to 6, that is, the sixth 4 ⁇ s unit boundary
  • the receiver implicitly indicates that there are two signal extension symbols having a predefined 1x period (1/4 OFDM samples). (implicitely) unknown.
  • the receiving STA obtains the payload length in the last data symbol by subtracting the number / period of the predefined signal extension symbols from the last data symbol length using the STA category information and the data rate or MCS level information of the currently received PPDU. can do. This is because a signal extension symbol for a specific STA is defined and the PSDU length indicated by the L-SIG is defined.
  • the largest number of signal extension symbols may be transmitted assuming the STA category having the worst performance. Therefore, ambiguity about the signal extension length and the number between STAs receiving the corresponding PPDU can be removed.
  • the transmitting STA may determine and transmit the number / length of signal determination symbols based on the STA category having the worst performance among the plurality of STAs. That is, the longest signal extension symbol (s) may be equally added to all STAs. As an example, as described above, extra time for additional receiving side processing may be secured, such as when padding bits are added in the last data symbol. In this case, the transmitting STA transmits the same length PPDU to all STAs based on the STA having the longest signal extension symbol or the longest PPDU length (the actual PPDU + signal extension symbol length) among the plurality of receiving STAs. The length of the signal extension symbol may be adjusted to make it possible.
  • FIG 25 illustrates an STA apparatus according to an embodiment of the present invention.
  • the STA apparatus may include a memory 25010, a processor 25020, and an RF unit 25030.
  • the STA device may be an AP or a non-AP STA as an HE STA device.
  • the RF unit 25030 may be connected to the processor 25020 to transmit / receive a radio signal.
  • the RF unit 25030 may upconvert data received from the processor into a transmission / reception band to transmit a signal.
  • the processor 25020 may be connected to the RF unit 25030 to implement a physical layer and / or a MAC layer according to the IEEE 802.11 system.
  • the processor 25030 may be configured to perform an operation according to various embodiments of the present disclosure according to the drawings and description described above.
  • a module for implementing the operation of the STA according to various embodiments of the present disclosure described above may be stored in the memory 25010 and executed by the processor 25020.
  • the processor 25020 may include a Forward Error Correction (FEC) encoder, and may also include a convulutional encoder.
  • FEC Forward Error Correction
  • the memory 25010 is connected to the processor 25020 and stores various information for driving the processor 25020.
  • the memory 25010 may be included in the processor 25020 or may be installed outside the processor 25020 and connected to the processor 25020 by known means.
  • the STA apparatus may include a single antenna or multiple antennas.
  • the specific configuration of the STA apparatus of FIG. 25 may be implemented so that the matters described in the aforementioned various embodiments of the present invention are applied independently or two or more embodiments are simultaneously applied.
  • 26 shows a data transmission method of an STA apparatus according to an embodiment of the present invention.
  • FIGS. 12 to 25 may be applied to all the descriptions of FIGS. 12 to 25.
  • the STA may generate a PPDU (S26010).
  • the generated PPDU has the above-described signal frame structure and includes a physical preamble and a data field, and the physical preamble may include a legacy preamble and an HE preamble.
  • the HE PPDU a FFT size of 4 times the FFT size used in the legacy preamble may be used for the data field.
  • the Discrete Fourier Transform / Inverse Discrete Fourier Transform (DFT) period of the data field may be four times the DFT / IDFT period of the legacy preamble portion.
  • DFT Inverse Discrete Fourier Transform
  • the PPDU generation step of the STA may further include adding a PE field to the end of the PPDU based on the capability information of the receiving STA and the constellation level of the transmission data.
  • the PE field may include at least one PE symbol. At least one PE symbol included in this PE field is not decoded by the receiving STA, but is used for securing a data decoding time of the receiving STA.
  • the performance information of the receiving STA may be received before the PPDU generation step.
  • the STA may receive and obtain performance information of the receiving STA, and the performance information may further include category information of the receiving STA.
  • the STA may determine whether to add a PE field (symbol) based on the category information of the receiving STA and the constellation level of the transmission data.
  • the category information of the receiving STA may indicate a constellation level that the receiving STA can process.
  • tail bits may be included in the last data symbol of the PPDU.
  • the tail field is included in the last symbol of the PPDU before the PE symbol addition, that is, the last data symbol of the PPDU, rather than the last symbol of the PPDU to which the PE field is added, that is, the PE symbol.
  • the STA may transmit the PPDU (S26020).
  • the last data symbol of the PPDU contains the payload as an OFDM symbol before the PE field.
  • the payload includes coded bits, pre-FEC padding bits and tail bits.
  • the length of the payload is that the last data symbol corresponds to a quarter boundary, two quarter boundary, three quarter boundary, or four quarter boundary. If the payload length corresponds to a quarter boundary, two quarter boundary, or three quarter boundary of the last data symbol, the remaining portion of the last data symbol is filled with post FEC padding bits. Accordingly, the STA may transmit the PPDU by filling the data size of the last data symbol.
  • the length of the PE field may be adjusted according to the length of the post FEC padding bits. For example, if the length of the post FEC padding bits ensures sufficient time for data processing of the receiving STA, the PE field may be omitted or the length of the PE field may be reduced. However, if the length of the added post FEC padding bits is short, the length of the PE field may be maintained.
  • the physical preamble may include decoding boundary information indicating at least one of a quarter boundary, a two quarter boundary, a three quarter boundary, or a fourth quarter boundary of the last data symbol.
  • the decoding boundary information may be included in the HE-SIG-A field of the physical preamble.
  • a PE field may be added for each of the plurality of receiving STAs, and the length of the plurality of PE fields is the longest PE of the PE fields for the plurality of receiving STAs. It can be determined by the length of the field. Accordingly, the longest length PE fields may be equally added to the plurality of receiving STAs.
  • the STA may determine whether to add the PE symbol based on at least one of the category information of the receiving STA, the MCS level of the data transmitted in the PPDU, and the data rate of the data transmitted in the PPDU.
  • the STA may receive category information of the receiving STA from the receiving STA or may be determined / obtained by the STA using other received information.
  • the STA may determine whether to add a padding symbol together with the MCS level or based on the constellation level instead of the MCS level.
  • the STA may add the PE symbol when the padding symbol addition is determined.
  • the method of generating and adding a PE symbol of the STA has been described in detail above.
  • the number of PE symbols added may be determined based on the category of the receiving STA.
  • the number of padding symbols added may be determined based on at least one of an MCS level, a data rate, a transmission bandwidth, and an amount of transmission data of the transmission data.
  • the added PE symbol may not be decoded at the receiving STA. That is, the PE symbol may correspond to a signal extension for a transmission signal including a PPDU.
  • the STA apparatus may include an FEC encoder, an interleaver, a segment parser, a mapper, an IDFT unit, and an analog / RF unit.
  • the FEC encoder, interleaver, segment parser, mapper, and IDFT unit may be included in the processor of FIG. 25, and the analog / RF unit may correspond to the RF unit of FIG. 25.
  • the STA device of FIG. 25 may perform the above-described operation of the HE STA. Briefly, this is as follows.
  • the STA may FEC encode the transmission data using the FEC encoder.
  • FEC encoding an STA may interleave transmission data using an interleaver.
  • the FEC encoder is an error correction code and may be implemented as a convolutional encoder, a turbo encoder, a low density parity check encoder (LDPC), or the like.
  • the FEC encoder is a convolutional encoder and may perform binary convolutional code (BCC) encoding.
  • BCC binary convolutional code
  • the STA may also map constellations using the mapper. There is no restriction on a modulation scheme in the mapper, and m-Phase Shift Keying (m-PSK) or m-Quardrature Amplitude Modulation (m-QAM) may be used.
  • m-PSK m-Phase Shift Keying
  • m-QAM m-Quardrature Amplitude Modulation
  • the STA may perform IDFT or IFFT processing of the transmission data using an IDFT unit.
  • the IDFT unit may perform IFFT or IDFT on modulation symbols output from the mapper to output an OFDM symbol in a time domain, and the STA may upconvert transmit data using an analog / RF unit. Can transmit the transmission signal.
  • the IDFT unit may apply different size FFTs to the first part and the second part of the transmission signal, and in particular, the second part may apply the FFT of the first part.
  • the symbol period of the second part may be four times the symbol period of the first part. This may be represented by a 4x IDFT / DFT period.
  • the analog / RF unit can up-convert the complex baseband waveform to transmit the RF signal.
  • the analog / RF unit may upconvert the processed data / signal in the baseband and transmit the transmission signal.
  • the data transmission and reception method has been described with reference to the example applied to the IEEE 802.11 system, but it is possible to apply to various wireless communication systems in addition to the IEEE 802.11 system.

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  • Computer Networks & Wireless Communication (AREA)
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Abstract

L'invention concerne un procédé de transmission de données d'un dispositif station (STA) dans un système LAN (LAN sans fil). Le procédé de transmission de données d'un dispositif STA, selon la présente invention, comprend les étapes consistant à: générer une unité de données de protocole physique (PPDU) contenant un préambule physique et un champ de données ; et transmettre la PPDU.
PCT/KR2016/001790 2015-04-27 2016-02-24 Procédé et dispositif de transmission de données dans un système de communications sans fil Ceased WO2016175439A1 (fr)

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