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WO2016195214A1 - Procédé de transmission de données dans un système de communication sans fil et son appareil - Google Patents

Procédé de transmission de données dans un système de communication sans fil et son appareil Download PDF

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Publication number
WO2016195214A1
WO2016195214A1 PCT/KR2016/001866 KR2016001866W WO2016195214A1 WO 2016195214 A1 WO2016195214 A1 WO 2016195214A1 KR 2016001866 W KR2016001866 W KR 2016001866W WO 2016195214 A1 WO2016195214 A1 WO 2016195214A1
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field
data
sta
stas
boundary
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Korean (ko)
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김진민
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 a data transmission method for supporting data transmission of a multi-user and a device supporting the same.
  • 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 60 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 160 MHz) and operates primarily in the 5 GHz band.
  • IEEE 802.11ax often discussed in the next-generation WLAN task group, also known as IEEE 802.11ax or High Efficiency (HEW) WLAN, includes: 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 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.
  • An object of the present invention is to propose a method for transmitting and receiving uplink / downlink multi-user data in a wireless communication system.
  • an AP device of a WLAN system and a data transmission method of the AP device according to an embodiment of the present invention are proposed.
  • the physical preamble includes: common boundary information indicating a common decoding boundary of data fields for the plurality of STAs, and an individual decoding boundary of each of the data fields for the plurality of STAs; It may include individual boundary information indicating.
  • the common boundary information indicates a 1/4, 2/4, 3/4 or 4/4 point of the last data symbol included in each of the data fields for the plurality of STAs as the common decoding boundary.
  • Individual boundary information may indicate the 4/4 point of the last data symbol included in each of the data fields for the plurality of STAs as the individual decoding boundary or may not indicate the 4/4 point.
  • the common boundary information is common to the HE-SIG field including common control information commonly required for the plurality of STAs.
  • the individual boundary information may be included in a user-specific field of the HE-SIG field including individual control information individually required for each of the plurality of STAs.
  • the last data symbol of at least one of the data fields for the plurality of STAs may include data bits and pre-FEC padding bits up to the common decoding boundary indicated by the common boundary information. have.
  • the common boundary information indicates the 1/4, 2/4, or 3/4 point of the last data symbol as the common decoding boundary
  • the individual boundary information indicates the last data symbol of the last decoding symbol as the respective decoding boundary.
  • the last data symbol of at least one of the data fields for the plurality of STAs may include a post-FEC padding bit.
  • a downlink (DL) multi-user (DL) for a plurality of STAs from an access point (AP) Receiving a physical protocol data unit (PPDU);
  • the DL MU PPDU includes a physical preamble and data fields for the plurality of STAs, and the physical preamble indicates a common decoding boundary of data fields included in the DL MU PPDU.
  • the common boundary information indicates a 1/4, 2/4, 3/4 or 4/4 point of the last data symbol included in each of the data fields for the plurality of STAs as the common decoding boundary.
  • Individual boundary information may indicate the 4/4 point of the last data symbol included in each of the data fields for the plurality of STAs as the individual decoding boundary or may not indicate the 4/4 point.
  • the data processing method of the STA is included in the data field for the STA when the individual boundary information indicates 4/4 points of the last data symbol included in the data field for the STA as the individual decoding boundary. Processing a last data symbol up to 4/4 points irrespective of the common boundary information; It may include.
  • the data processing method of the STA indicates that the individual boundary information is not the 4/4 point of the last data symbol included in the data field for the STA as the individual decoding boundary. Processing the last data symbol included to the point indicated by the common boundary information; It may include.
  • the common boundary information is common to the HE-SIG field including common control information commonly required for the plurality of STAs.
  • the individual boundary information may be included in a user-specific field of the HE-SIG field including individual control information individually required for each of the plurality of STAs.
  • An access point (AP) of a wireless LAN (WLAN) system according to another embodiment of the present invention, the RF unit for transmitting and receiving radio signals; And a processor for controlling the RF unit; Wherein the processor generates a DL MU Physical Protocol Data Unit (PPDU) including a physical preamble and data fields for a plurality of STAs, and transmits the DL MU PPDU;
  • the physical preamble indicates common boundary information indicating a common decoding boundary of data fields for the plurality of STAs, and indicates an individual decoding boundary of each of the data fields for the plurality of STAs. It may include individual boundary information.
  • the common boundary information indicates a 1/4, 2/4, 3/4 or 4/4 point of the last data symbol included in each of the data fields for the plurality of STAs as the common decoding boundary.
  • Individual boundary information may indicate the 4/4 point of the last data symbol included in each of the data fields for the plurality of STAs as the individual decoding boundary or may not indicate the 4/4 point.
  • the common boundary information is common to the HE-SIG field including common control information commonly required for the plurality of STAs.
  • the individual boundary information may be included in a user-specific field of the HE-SIG field including individual control information individually required for each of the plurality of STAs.
  • the last data symbol of at least one of the data fields for the plurality of STAs may include data bits and pre-FEC padding bits up to the common decoding boundary indicated by the common boundary information. have.
  • the common boundary information indicates the 1/4, 2/4, or 3/4 point of the last data symbol as the common decoding boundary
  • the individual boundary information indicates the last data symbol of the last decoding symbol as the respective decoding boundary.
  • the last data symbol of at least one of the data fields for the plurality of STAs may include a post-FEC padding bit.
  • the last data symbol of the data field for each STA included in one DL MU PPDU is padded to have a 4x symbol length, and the signal extension for each STA is collectively up to 4x symbol length.
  • the implementation is simple, and the overhead of signaling the DL MU PPDU is reduced.
  • the signal when the signal is extended based on the data length included in the last data symbol of the data field (or the length of the packet extension field is determined based on the data length included in the last data symbol). , The overhead is reduced due to efficient signal extension.
  • the overhead due to signaling of the decoding boundary is reduced.
  • 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 illustrates a MAC frame format of an IEEE 802.11 system to which the present invention can be applied.
  • FIG. 6 is a diagram illustrating a downlink multi-user PPDU format in a wireless communication system to which the present invention can be applied.
  • FIG. 7 is a diagram illustrating a downlink multi-user PPDU format in a wireless communication system to which the present invention can be applied.
  • FIG. 8 is a diagram illustrating a downlink MU-MIMO transmission process in a wireless communication system to which the present invention can be applied.
  • FIG. 9 is a diagram illustrating a High Efficiency (HE) format PPDU according to an embodiment of the present invention.
  • HE High Efficiency
  • FIGS. 10 through 12 are diagrams illustrating an HE format PPDU according to an embodiment of the present invention.
  • FIG. 13 is a table in which STAs are classified into four categories based on specific parameters to distinguish the performance of the STAs.
  • FIG. 14 is a table illustrating whether to add a packet extension field based on a data rate according to a category of an STA.
  • FIG. 15A is a diagram illustrating a padding and signal expansion method according to a first embodiment of the present invention.
  • FIG. 15B is a diagram illustrating a padding and signal expansion method according to a second embodiment of the present invention.
  • 16 to 22 illustrate an embodiment of signaling a decoding boundary value using an HE-SIG field.
  • 23 and 24 illustrate an embodiment of signaling a decoding boundary value using an L-SIG field.
  • 25 is a flowchart illustrating a method for controlling an STA according to an embodiment of the present invention.
  • 26 is a flowchart illustrating a method for controlling an AP according to an embodiment of the present invention.
  • 27 is a block diagram of each 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 may be implemented with wireless technologies such as Institute of Electrical and Electronics Engineers (IEEE) 802.11 (Wi-Fi), IEEE 802.16 (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.
  • Table 1 below is a table illustrating the HT-SIG field.
  • 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.
  • the service field has 16 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.
  • Table 2 is a table illustrating the VHT-SIG-A1 field.
  • 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.
  • Table 3 is a table illustrating the VHT-SIG-A2 field.
  • 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 decodes the VHT-SIG-B field only when common control information included in the VHT-SIG-A field indicates that the currently received PPDU indicates MU-MIMO transmission. It may be designed to. 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 For 160 MHz transmission and 80 + 80 MHz, first the 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 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.
  • Downlink MU- MIMO Frame (DL MU- MIMO Frame)
  • FIG. 6 is a diagram illustrating a downlink multi-user PPDU format in a wireless communication system to which the present invention can be applied.
  • a PPDU includes a preamble and a data field.
  • the data field may include a service field, a scrambled PSDU field, tail bits, and padding bits.
  • the AP may aggregate the MPDUs and transmit a data frame in an A-MPDU (aggregated MPDU) format.
  • the scrambled PSDU field may be configured as an A-MPDU.
  • An A-MPDU consists of a sequence of one or more A-MPDU subframes.
  • the A-MPDU is zero after the last A-MPDU subframe to fit the A-MPDU to the last octet of the PSDU. And three to three octets of an end-of-frame (EOF) pad.
  • EEF end-of-frame
  • the A-MPDU subframe consists of an MPDU delimiter, and optionally an MPDU may be included after the MPDU delimiter.
  • an MPDU may be included after the MPDU delimiter.
  • a pad octet is attached after the MPDU to make the length of each A-MPDU subframe a multiple of 4 octets.
  • the MPDU Delimiter is composed of a Reserved field, an MPDU Length field, a cyclic redundancy check (CRC) field, and a delimiter signature field.
  • CRC cyclic redundancy check
  • the MPDU Delimiter may further include an end-of-frame (EOF) field. If the MPDU Length field is 0 and the A-MPDU subframe used for padding or the A-MPDU subframe carrying the MPDU when the A-MPDU consists of only one MPDU, the EOF field is set to '1'. do. Otherwise it is set to '0'.
  • EEF end-of-frame
  • the MPDU Length field contains information about the length of the MPDU.
  • An A-MPDU subframe whose MPDU Length field has a value of '0' is used when padding the corresponding A-MPDU to match the A-MPDU to the octets available in the VHT PPDU.
  • the CRC field includes CRC information for error checking
  • the Delimiter Signature field includes pattern information used to search for an MPDU delimiter.
  • the MPDU is composed of a MAC header, a frame body, and a frame check sequence (FCS).
  • FCS frame check sequence
  • FIG. 7 is a diagram illustrating a downlink multi-user PPDU format in a wireless communication system to which the present invention can be applied.
  • the MU PPDU includes L-TFs field (L-STF field and L-LTF field), L-SIG field, VHT-SIG-A field, VHT-TFs field (VHT-STF field and VHT-LTF). Field), VHT-SIG-B field, Service field, one or more PSDU, padding field, and Tail bit. Since the L-TFs field, the L-SIG field, the VHT-SIG-A field, the VHT-TFs field, and the VHT-SIG-B field are the same as in the example of FIG. 4, detailed descriptions thereof will be omitted.
  • Information for indicating the duration of the PPDU may be included in the L-SIG field.
  • the PPDU duration indicated by the L-SIG field is the symbol assigned to the VHT-SIG-A field, the symbol assigned to the VHT-TFs field, the field assigned to the VHT-SIG-B field, and the Service field.
  • the STA receiving the PPDU may obtain information about the duration of the PPDU through the information indicating the duration of the PPDU included in the L-SIG field.
  • Group ID information and space-time stream number information per user are transmitted through the VHT-SIG-A, and a coding method and MCS information are transmitted through the VHT-SIG-B.
  • the beamformees may check the VHT-SIG-A and the VHT-SIG-B, and may know whether the beamformees belong to the MU MIMO frame. Therefore, the STA that is not a member STA of the corresponding Group ID or the member of the corresponding Group ID or the number of allocated streams is '0' reduces power consumption by setting to stop receiving the physical layer from the VHT-SIG-A field to the end of the PPDU. can do.
  • the Group ID can receive the Group ID Management frame transmitted by the Beamformer in advance, so that the MU group belonging to the Beamformee and the user of the group to which the Beamformee belongs, that is, the stream through which the PPDU is received.
  • each VHT A-MPDU may be transmitted in a different stream.
  • each A-MPDU may have a different bit size.
  • null padding may be performed such that the time when the transmission of the plurality of data frames transmitted by the beamformer is the same as the time when the transmission of the maximum interval transmission data frame is terminated.
  • the maximum interval transmission data frame may be a frame in which valid downlink data is transmitted by the beamformer for the longest period.
  • the valid downlink data may be downlink data that is not null padded.
  • valid downlink data may be included in the A-MPDU and transmitted.
  • Null padding may be performed on the remaining data frames except the maximum interval transmission data frame among the plurality of data frames.
  • the beamformer may encode and fill one or more A-MPDU subframes located in temporal order in the plurality of A-MPDU subframes in the A-MPDU frame with only the MPDU delimiter field.
  • An A-MPDU subframe having an MPDU length of 0 may be referred to as a null subframe.
  • the EOF field of the MPDU Delimiter is set to '1'. Accordingly, when the MAC layer of the receiving STA detects the EOF field set to 1, power consumption may be reduced by setting the physical layer to stop reception.
  • FIG. 8 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.
  • New frames for next-generation WLAN systems 802.11ax systems, with increasing attention from vendors in various fields for next-generation WiFi and increased demand for high throughput and quality of experience (QoE) after 802.11ac.
  • QoE quality of experience
  • IEEE 802.11ax is a next-generation WLAN system that supports higher data rates and handles higher user loads.
  • One of the recently proposed WLAN systems is known as high efficiency WLAN (HEW: High). Called Efficiency WLAN).
  • the IEEE 802.11ax WLAN system may operate in the 2.4 GHz frequency band and the 5 GHz frequency band like the existing WLAN system. It can also operate at higher 60 GHz frequency bands.
  • IEEE 802.11ax the existing IEEE 802.11 OFDM system (IEEE 802.11a, 802.11n) is used for outdoor throughput transmission for average throughput enhancement and inter-symbol interference in outdoor environment. , 4x larger FFT size for each bandwidth than 802.11ac. This will be described with reference to the drawings below.
  • the description of the non-HT format PPDU, the HT-mixed format PPDU, the HT-greenfield format PPDU, and / or the VHT format PPDU described above will be described in HE format unless otherwise noted. May be incorporated into the description of the PPDU.
  • FIG. 9 is a diagram illustrating a High Efficiency (HE) format PPDU according to an embodiment of the present invention.
  • HE High Efficiency
  • FIG. 9A illustrates a schematic structure of an HE format PPDU
  • FIGS. 9B to 9D illustrate more specific structures of an 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).
  • 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.
  • FIG. 25A the order of the HE-STF field, the HE-SIG field, and the HE-LTF field is illustrated, 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.
  • L-part and HE-part may be collectively referred to as a physical preamble (PHY).
  • PHY physical preamble
  • the HE-SIG may include information for decoding the HE-data field (eg, OFDMA, UL MU MIMO, Enhanced MCS, etc.).
  • information for decoding the HE-data field 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 FFT means relative size with respect to legacy WLAN system (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 160 MHz, respectively
  • the FFT size used for the HE-part is 256 at 20 MHz, 40 MHz, 80 MHz, and 160 MHz, respectively. , 512, 1024, 2048.
  • the FFT size is larger than that of the legacy WLAN system, the number of subcarriers per unit frequency is increased because the subcarrier frequency spacing is smaller, but the OFDM symbol length is 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, 16 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 160 MHz, respectively.
  • the HE-SIG when the HE-SIG is transmitted by being divided into the HE-SIG-A field and the HE-SIG-B field as shown in FIG. It may differ from 9 (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 160 MHz, respectively.
  • the HE-SIG field is not divided into the HE-SIG-A field and the 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 160 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.
  • the HE format PPDU may be transmitted in a 40 MHz, 80 MHz, or 160 MHz frequency band through a total of four 20 MHz channels. This will be described in more detail with reference to the drawings below.
  • FIG. 10 is a diagram illustrating a HE format PPDU according to an embodiment of the present invention.
  • FIG. 10 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 B field may be located after the HE-SIG A field.
  • the FFT size per unit frequency may be larger after 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 may include common control information that is commonly transmitted to STAs that receive 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 includes the same information.
  • the HE-SIG-A field informs the total bandwidth information of the system.
  • Table 4 is a table illustrating information included in the HE-SIG A field.
  • 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 estimation in MIMO transmission.
  • 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 (ie, an 80 MHz band), the L-STF, L-LTF, L-SIG, and HE-SIG A fields may be repeatedly transmitted on every 20 MHz channel. .
  • 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. 11 is a diagram illustrating a 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 is received by all STAs.
  • 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. 27.
  • 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-B field may be transmitted in units of 20 MHz similarly to the HE-SIG-A field without transmitting over the entire band. This will be described with reference to the drawings below.
  • FIG. 12 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. 12, 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. 10 to 12 may be distinguished 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.
  • DL MU transmission downlink multi-user transmission
  • UL MU transmission uplink multi-user transmission
  • Such DL MU transmission or UL MU transmission may be multiplexed in the frequency domain or the spatial domain.
  • different frequency resources eg, subcarriers or tones
  • OFDMA orthogonal frequency division multiplexing
  • different spatial streams may be allocated as downlink or uplink resources for each of the plurality of STAs.
  • a transmission expression through different spatial streams may be referred to as 'DL / UL MU MIMO' transmission.
  • overlap between frequency resources used for transmitting uplink data by a plurality of STAs may occur. For example, when oscillators of the plurality of STAs are different, frequency offsets may appear differently. If each of a plurality of STAs having different frequency offsets simultaneously performs uplink transmission through different frequency resources, some of frequency regions used by each of the plurality of STAs may overlap.
  • the AP may receive signals of different power from each of the plurality of STAs. In this case, a signal arriving at a weak power may be difficult to be detected by the AP relative to a signal arriving at a strong power.
  • 4x FFT size may be applied in the 802.11ax system. Accordingly, the number of symbols to be transmitted is increased compared to the existing system, thereby improving throughput, but data processing time for processing data at the receiver may be increased. As a result, a problem may occur in that short interframe space (SIFS) defined in an existing system cannot be applied to an 802.11ax system as it is.
  • SIFS short interframe space
  • data having a 4x FFT size may take longer than 16 ms, which is a processing time of data having a 1x FFT size of an 802.11ac system, and may take approximately 32 ms.
  • the HE-LTF may have a size of 2 ⁇ FFT, and in this case, the processing time of the HE-LTF may be approximately 24 ms.
  • 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, 16 ms.
  • the transmitter adds an additional packet extension field (or signal extension field) by an additional time necessary (or additional data processing time, additional decoding time) in addition to SIFS to allow the receiver to complete the data processing. I can send it.
  • the receiver processes the received data, thereby sufficiently securing the data processing time of the receiver.
  • the data processing performance of each receiver may vary according to the function and purpose of use of the receiver, and the time required for data processing may vary depending on the data processing performance of the receiver. For example, a STA having good data processing performance on the same data symbol (eg, a chatty device such as a mobile phone or a tablet PC) can process data quickly, but a STA having poor data processing performance. (Eg, a home device such as a refrigerator or an air conditioner), it may take longer to process data. Since the data processing time increases or decreases according to the data processing performance of the receiver, the transmitter may determine whether to transmit the packet extension field and, if so, the length of the packet extension field based on the data processing performance of the receiver. .
  • Receiver performance can be classified into N categories according to specific parameters such as the function of the receiver and the purpose of use (N is a natural number). This will be described later with reference to FIGS. 13 and 14.
  • FIG. 13 is a table in which STAs are classified into four categories based on specific parameters to distinguish the performance of the STAs.
  • STAs may be classified into four categories as follows based on the maximum supportable MCS level and bandwidth size.
  • STA category 1 does not support 256QAM (or MCS levels 8, 9) and does not support 160 MHz and 80 + 80 MHz bandwidths
  • STA category 2 Supports 256QAM (or MCS levels 8, 9) and does not support 160 MHz and 80 + 80 MHz bandwidths
  • STA category 3 does not support 256QAM (or MCS levels 8, 9) and supports 160 MHz and 80 + 80 MHz bandwidths
  • STA category 4 Supports 256QAM (or MCS levels 8, 9) and supports 160 MHz and 80 + 80 MHz bandwidths
  • the STA categories classified based on the MCS level and the bandwidth size may be interpreted as data processing performance (or decoding performance) of the STA. Therefore, it is not necessary to signal additionally (or separately) to classify the data processing capability of the STA by category.
  • FIG. 14 is a table illustrating whether to add a packet extension field based on a data rate for each category of an STA.
  • the transmitter determines whether to add and transmit a packet extension field according to the data rate (or constellation level) of the data (or data field or PPDU) to be transmitted and the performance of the receiver receiving the data. Can be.
  • the transmitter may determine that the receiver does not need additional time to process the data, and thus may not transmit the packet extension field. Conversely, if the data rate of the data (or PPDU) that the transmitter is trying to transmit exceeds 1200 Mb / s, the transmitter determines that the receiver needs additional time to process the data, so that the receiver can process the data. In order to secure the packet extension field may be transmitted. In this case, the length (or time) of the transmitted packet extension field may be 16 us.
  • the STA category of the receiver is ‘2’
  • the transmitter may determine that the receiver does not need additional time to process the data, and thus may not transmit the packet extension field. Conversely, if the data rate of the data (or PPDU) that the transmitter is trying to transmit exceeds 2400 Mb / s, the transmitter determines that the receiver needs additional time to process the data, so that the receiver can process the data. In order to secure the packet extension field may be transmitted. In this case, the length (or time) of the transmitted packet extension field may be 16 us.
  • the transmitter determines that the receiver does not need additional time to process the data, and thus may not transmit the packet extension field. Conversely, if the data rate of the data (or PPDU) that the transmitter is trying to transmit exceeds 3600 Mb / s, the transmitter determines that the receiver needs additional time to process the data, so that the receiver can process the data. In order to secure the packet extension field may be transmitted. In this case, the length (or time) of the transmitted packet extension field may be 16 us.
  • the transmitter may not transmit the packet extension field by determining that the receiver does not need additional time to process the data regardless of the data rate of the data (or PPDU) to be transmitted. have.
  • the transmitter may transmit a packet extension field based on the data rate of the PPDU to be transmitted and the STA category of the receiver that receives the PPDU.
  • the lengths of the data and packet extension fields received at each receiver may be different for each STA.
  • the length of the packet extension field may vary according to the performance of each receiver and the data rate (or constellation level) of data to be transmitted, as described above.
  • the total lengths of the data field and the packet extension field need to be equally adjusted for each receiving STA (length of the DL MU PPDU).
  • the receiving STA may indicate an STA receiving the data field and the packet extension field included in the DL MU PPDU. Therefore, hereinafter, a method of padding a data field and a method of inserting a packet extension field (or a signal extension method) in order to match the same length will be described in detail below.
  • the data symbol means an OFDM symbol including one or more data bits (or information bits and data), and may include padding bits in addition to the data bits.
  • the signal extension symbol may mean an OFDM symbol including one or more signal extension bits (or dummy bits). In this case, the signal extension symbol may be generated based on a general OFDM symbol generation method.
  • the PPDU includes both a single user (SU) PPDU and a multi-user (MU) PPDU.
  • SU PPDU means a PPDU carrying a single PSDU
  • MU PPDU means a PPDU carrying one or more PSDU (s) for one or more STAs using OFDMA and / or MU MIMO technology.
  • the processing time of the 4x symbol is 32 ms and the length of the 4x symbol is 12.8 ms except for the guard interval GI.
  • the present invention is not limited thereto. can be changed.
  • the padding method and the signal extension method can be classified into two types as follows. 15 is a diagram illustrating a padding and signal expansion method.
  • FIG. 15A is a diagram illustrating a padding and signal expansion method according to a first embodiment of the present invention.
  • padding bits may be inserted up to 4x symbol length (or symbol duration) in the case of a data field, and signal extension having a 4x symbol length in the case of a packet extension field. It can be created to contain a symbol and inserted after the data field.
  • the last data symbol may be filled with padding bits up to 4x symbol length (or padding bits may be inserted up to the last 4x symbol length in the last data symbol).
  • the padding bit inserted into the last data symbol may be a pre-FEC padding bit (or padding bit applied in an 802.11ac system).
  • the padding bit may not be inserted into the last data symbol.
  • the padding bits may or may not be additionally included.
  • the data fields included in one DL MU PPDU may have the same symbol length (for each receiving STA).
  • a packet extension field including a signal extension symbol having a 4x symbol length may be inserted in a batch.
  • the packet extension field included in one DL MU PPDU may have the same length (per receiving STA).
  • the last data symbol of the data field included in one DL MU PPDU is filled with padding bits up to 4x symbol length (but padding bits if the last data symbol is filled with data bits up to 4x symbol length). Since the packet extension field having a 4x symbol length is inserted in a batch, the total length of the data field and the packet extension field included in one DL MU PPDU may be the same.
  • the implementation is simple and has an advantage of less overhead in signaling the DL MU PPDU.
  • the STA may decode the last data symbol of the received data field up to 4x symbol length, and thus, may additionally decode the inserted padding bit (when a padding bit is inserted). ).
  • the transmitting STA since the lengths of the data field and the packet extension field are fixed to 4x symbol length, the transmitting STA does not need to separately signal the symbol lengths of the data field and the packet extension field and transmit them to the receiving STA.
  • FIG. 15B is a diagram illustrating a padding and signal expansion method according to a second embodiment of the present invention.
  • the last data symbol of a data field included in one DL MU PPDU is padded with bits up to 4x symbol length (or symbol duration). Can be filled (if the last data symbol is not filled with data bits).
  • the inserted padding bit may be a post-FEC padding bit added after channel encoding to secure additional data processing time of the receiver. Therefore, the receiver receiving the DL MU PPDU to which the present embodiment is applied may decode only the data bits but not the padding bits.
  • the transmitter may transmit information about the number of data bits (or the length of the data bits and the data length) included in the last data symbol to the receiver. Therefore, the receiver has an advantage of using the time when the padding bits are transmitted as the time for decoding the data bits.
  • a packet extension field may be inserted, and the length of the inserted packet extension field may be determined by various values. That is, unlike the case where packet extension fields having a fixed symbol length are inserted in one embodiment in the first embodiment, in the second embodiment, the packet extension field is flexibly determined based on the number of data bits (or the length of the data bits and the data length).
  • a packet extension field having a symbol length may be inserted. In this case, the symbol length of the inserted packet extension field may be determined to be 4 ms, 8 ms, 12 ms, or 16 ms depending on the data length in the last data symbol.
  • the length of the signal extension symbol included in the packet extension field may be determined based on the number of data bits (or length of data bits, data length) included in the last data symbol.
  • the symbol length of the packet extension field may be determined as the length for securing the decoding processing time of data bits.
  • the time at which the post-FEC padding bits are transmitted may also be used as the time for decoding the data bits.
  • the symbol length of the packet extension field may be determined by the difference between the time additionally needed to decode the data bits and the time that the padding bits are transmitted.
  • the symbol length of the packet extension field is shorter than that of the first embodiment, thereby reducing the overhead.
  • the transmitter needs to separately signal and transmit information for indicating how far to decode the data field (hereinafter, referred to as a 'decoding boundary' or 'padding boundary')
  • the overhead may increase. have. Therefore, in order to reduce such overhead, a method of unifying and transmitting a decoding boundary (or padding boundary) for each data field included in the DL MU PPDU will be described in detail below.
  • 16 is a diagram illustrating a padding and signal expansion method according to a third embodiment of the present invention.
  • the AP simultaneously transmits data to STAs 1 and 2 through one DL MU PPDU. That is, it is assumed that one DL MU PPDU transmitted by the AP includes a first data field including data for STA 1 and a second data field including data for STA 2.
  • the time taken to decode data received through the DL MU PPDU is the same for both STA 1 and 2.
  • padding bits may be inserted into the remaining data fields based on the data field having the longest data length so that the decoding boundaries of the data fields included in the DL MU PPDU are the same.
  • the data bits of the last data symbol of the first data field for STA 1 are filled up to 3x symbol length
  • the last data symbol of the second data field for STA 2 is filled up to 2x symbol length.
  • information indicating the 3x symbol length as the decoding boundary for the first data field and information indicating the 2x symbol length as the decoding boundary for the second data field need to be signaled and transmitted, respectively. There is. In this case, a problem arises in that overhead is increased in that different decoding boundary values should be signaled for each data field.
  • padding may be performed on the remaining data fields based on the data field having the longest data length among the data fields included in the DL MU PPDU to unify the decoding boundaries for each data field.
  • the padding may be pre-FEC padding (or padding applied to an 802.11ac system).
  • padding bits may be inserted into the second data field based on the decoding boundary of the first data field.
  • the last data symbol of the second data field may be filled with padding bits (or padding bits may be inserted) up to a 3x symbol length that is the decoding boundary of the first data field.
  • the transmitter compares the data lengths of the data fields to be transmitted and inserts padding bits into the remaining data fields based on the data field having the longest data length to fit the decoding boundary equally for each data field.
  • the transmitter may unify the decoding boundary values of all data fields included in one DL MU PPDU into one, and signal and transmit the unified decoding boundary values to each receiver.
  • the receiver may perform decoding on the received data field to the point indicated by the decoding boundary value.
  • the decoding boundary value may indicate a quarter (3.2 ms), 2/4 (6.4 ms), 3/4 (9.6 ms), or 4/4 (12.8 ms) point when the last data symbol is divided into quarters. Can be. That is, the decoding boundary value may indicate any one of 1/4 to 4/4 points as the data length in the last data symbol. For example, if the decoding boundary value is '1', one quarter point (or 1x symbol length) of the last data symbol; if the decoding boundary value is '2', two quarter point (2x symbol length) of the last data symbol.
  • decoding boundary value for indicating four points of the last data symbol may be set to various values.
  • decoding boundary values may be referred to as padding boundary values or a-factor values.
  • padding bits for adjusting the 4x symbol length may be additionally inserted into the last data symbol of each data field. More specifically, if the data bits of the last data symbol in the data field are not filled to the length of 4x symbols (the decoding boundary value indicates a quarter to three quarters of the last data symbol, or the decoding boundary value is The last data symbol may be filled with padding bits up to 4x symbol length, unless pointing to 4/4 points of the last data symbol.
  • the last data symbol of the first data field is filled with data bits up to 3x symbol length
  • the last data symbol of the second data field is data bits up to 2x symbol length and from 2x symbol length to 3x symbol length. It may be filled with padding bits.
  • the transmitter may additionally insert padding bits from 3x symbol length to 4x symbol length in the last data symbol of the first data field and from 3x symbol length to 4x symbol length in the last data symbol of the second data field.
  • the inserted padding bit may be a post-FEC padding bit.
  • the time when the post-FEC padding is transmitted may be used as a time for decoding the data bits of the data field.
  • the last data symbol of each data field (received by a plurality of STAs) included in one DL MU PPDU has the same decoding boundary value and has a 4x symbol length.
  • a packet extension field may be inserted to secure additional data processing time (in addition to SIFS) of the receiver after the data field in which the last data symbol length is equally equal to 4x symbol length.
  • additional data processing time in addition to SIFS
  • the length of the packet extension field for securing the data processing time (or decoding time) of each receiver may also be different for each receiver.
  • the length of the packet extension field is the same length for each receiving STA as well as the aforementioned data field. It needs to be determined (or adjusted). Accordingly, even in this case, the lengths of the remaining data fields and the packet extension fields may be determined based on the total lengths of the longest data fields and the packet extension fields. Since the data field has the same length for each receiving STA, this may be expressed as the length of the remaining packet extension field is determined based on the length of the longest packet extension field.
  • the decoding boundary value may be signaled and transmitted in the HE-SIG field or the L-SIG field.
  • 16 to 22 illustrate embodiments in which a decoding boundary value is signaled using an HE-SIG field
  • FIGS. 23 and 24 illustrate embodiments of signaling a decoding boundary value using an L-SIG field. to be.
  • the decoding boundary value may be signaled using the HE-SIG field.
  • the decoding boundary value may be signaled and included in the HE-SIG A, B, or C field. If the decoding boundary value is signaled in the HE-SIG A field, the decoding boundary value may be included in the common information field (or common field) included in the HE-SIG A field. Or, if the decoding boundary value is signaled in the HE-SIG B field, the decoding boundary value may be included in the common information field (or common field) included in the HE-SIG B field.
  • the common information field may indicate a field including common control information for a plurality of STAs receiving data through one DL MU PPDU.
  • the decoding boundary value is included in the common information field of the HE-SIG field, the present embodiment is performed when the decoding boundary value is signaled as one value common to a plurality of data fields included in the DL MU PPDU (eg, the third In the case of an embodiment).
  • the decoding boundary value may be included in a user-specific field included in the HE-SIG B field, which will be described later in detail.
  • the decoding boundary value signaled in the HE-SIG field indicates the number of data bits (or data length) included in the last data symbol of the data field, as described above. Since the decoding boundary value indicates any one of 1/4 to 4/4 points of the last data symbol, it may be signaled in the HE-SIG field as a bit size of 2 bits.
  • an unnecessary packet extension field (or an unnecessary long packet extension field). May cause an increase in overhead. This will be described later with reference to FIGS. 17 to 20.
  • a first data field received at STA 1 through one DL MU PPDU includes two 4x data symbols
  • a second data field received at STA 2 includes one 4x data symbol.
  • STA 1 does not require additional data processing time to decode the first data field
  • STA 2 requires additional data processing time to decode the second data field.
  • the STA is based on the longest decoding boundary value a (the decoding boundary value of the data field received in STA 1) (eg, '4').
  • the last data symbol of the data field received at 2 may be filled with padding bits (e.g., pre-FEC padding or padding applied to an 802.11ac system) and the longest decoding boundary value (a) is signaled in the HE-SIG field. Can be.
  • a packet extension field 1710 having a length equal to the length of the longest packet extension field (the length of the packet extension field of STA 2) may be inserted after the data field for STA 1.
  • STA 1 unnecessarily receives a packet extension field 1710 having a 4x symbol length even though it does not require additional data processing time (or additional decoding time) for the received data, thereby increasing overhead.
  • This problem is indicated by i) indicating the common decoding boundary values for the plurality of STAs and the individual decoding boundary values for each of the plurality of STAs (see FIGS. 18 to 22), or ii) the decoding boundary values through the L-SIG field. It can be solved when instructed (see FIGS. 23 and 24), which will be described later in detail with reference to the drawings.
  • each of the data fields for STA 1 and 2 includes two 4x data symbols
  • the last data symbol of the data field included in the DL SU PPDU for STA 1 is filled with data bits up to a length of 4x data symbol
  • STA 2 It is assumed that the last data symbol of the data field included in the DL SU PPDU for is filled with data bits up to a length of 1x data symbol.
  • STA 1 has excellent data processing performance (or good decoding performance) so that no additional data processing time is required, and STA 2 has low data processing performance, and thus additional data processing time as Tsym (4x symbol length) is required. Assume that we require
  • the AP may have a length from 1x symbol length to 4x symbol length (from quarter point to 4) to the last data symbol of the data field for STA 2.
  • a pad extension bit post-FEC padding bit
  • a packet extension field with a length of about 1x symbol eg 4 ms
  • the frame format of the DL SU PPDU received at each STA may be represented as shown in FIG. 18.
  • the decoding boundary value of the data field for STA 1 may be '4', and the decoding boundary value may be signaled in the HE-SIG field of the DL SU PPDU received in STA 1 and received in STA 1.
  • the decoding boundary value of the data field for the STA 2 may be '1', and the corresponding decoding boundary value may be signaled in the HE-SIG field of the DL SU PPDU received in the STA 2 and received in the STA 2.
  • the AP may insert padding bits into the remaining data fields centering on the data field having the longest data length among the data fields included in one DL MU PPDU. For example, if data for STA 1 and 2 in FIG. 18 is transmitted through one DL MU PPDU, the longest (or largest) decoding boundary value of the decoding boundary values of the data fields for STA 1 and 2 may be determined.
  • the padding bit may be inserted into the STA 2 according to the decoding boundary value of the STA 1. Since the decoding boundary value of STA 1 is '4', the last data symbol of the data field for STA 2 has padding bits from 1x symbol length to 4x symbol length (from 1/4 point to 4/4 point of last data symbol). Can be inserted. In this case, the inserted padding bit may be a pre-FEC padding bit or a padding bit applied to an 802.11ac system.
  • a packet extension field having a 4x symbol length must be additionally inserted after the data field for STA 2.
  • the total length of the data field and the packet extension field included in one DL MU PPDU should be the same for each receiving STA. Therefore, after the data field for STA 1, a packet extension field 2010 having the same length as that of STA 2 may be additionally inserted, as illustrated in FIG. 20.
  • 19 and 20 correspond to an embodiment of signaling only common boundary information indicating a decoding boundary value common to data fields for a plurality of STAs included in a DL MU PPDU.
  • signaling only common boundary information as described above, there is a problem in that an overhead is increased by addition of an unnecessary packet extension field. This problem may be solved when individual boundary information indicating a decoding boundary value for each of a plurality of STAs is transmitted together with common boundary information.
  • FIG. 21 illustrates a case in which data for STAs 1 and 2 in FIG. 18 are transmitted through one DL MU PPDU, i) a decoding boundary value common to data fields for a plurality of STAs included in the DL MU PPDU; Or DL MU PPDU frame when all common boundary information indicating a decoding boundary) and ii) separate boundary information indicating a decoding boundary value (or a decoding boundary) applied to data fields for each of a plurality of STAs are all signaled. It is a figure which shows a format.
  • the individual boundary information indicates that the decoding boundary value of the data field for a specific STA is a predetermined value (for example, '4') regardless of the common boundary information or is equal to a value indicated by the common boundary information. can do. That is, the individual boundary information may be filled with data bits up to a specific point (eg, 4/4 of the last data symbol) of the last data symbol of the data field for a specific STA regardless of the decoding boundary value indicated by the common boundary information. The data bit may be filled up to the decoding boundary indicated by the common boundary information. Alternatively, the individual boundary information may indicate that the decoding boundary value of the data field for the specific STA is a preset value (eg, '4') or may not be a preset value.
  • a preset value eg, '4'
  • the individual boundary information may indicate that an individual decoding boundary of a data field for a specific STA is or is not a specific point of the last data symbol (eg, 4/4 point of the last data symbol).
  • the individual boundary information indicates that the decoding boundary value of the data field for the specific STA is '4' or not '4' (that is, the decoding boundary value is '1', '2', or In the case of indicating '3').
  • Individual boundary information may be included in a specific field configured with a '1' bit size, and in the following, this specific field may be referred to as an 'individual decoding boundary field'.
  • the separate decoding boundary field may be included in the HE-SIG field (eg, the HE-SIG B field) and transmitted.
  • the individual decoding boundary field may be included in the user specific field of the HE-SIG field and transmitted.
  • Each decoding boundary field may have a value of '0' or '1'.
  • common boundary information indicating '1' as a decoding boundary value common to STAs 1 and 2 may be transmitted to STAs 1 and 2.
  • individual boundary information indicating that an individual decoding boundary value for STA 1 is '4' regardless of common boundary information may be transmitted to STA 1.
  • individual boundary information indicating that the individual decoding boundary value for STA 2 is the same as the common decoding boundary value indicated by the common boundary information (or not indicating that the decoding boundary value is '4') may be transmitted to STA 2. Can be.
  • the STAs 1 and 2 may decode the data field based on the common boundary information and the individual boundary information.
  • STA 1 recognizes that the decoding boundary value is '4' according to the received common boundary information and individual boundary information, and the last data symbol of the received data field is 4x symbol long (or up to 4/4 points of the last data symbol). Can be decoded.
  • STA 2 recognizes that the decoding boundary value is '1' according to the received common boundary information and individual boundary information, and the last data symbol of the received data field is 1x symbol length (or 1/4 point of the last data symbol). Decode).
  • the AP does not need to insert an unnecessarily long packet extension field after the data field for STA 1 to match the DL MU PPDU length, as shown in FIG. 20, and to update the data for STA 2 to match a common decoding boundary value.
  • overhead caused by unnecessary packet extension fields and padding bits may be reduced, thereby improving system performance.
  • This can be easily done by comparing the DL MU PPDU format shown in FIG. 20 (the embodiment signaling only common boundary information) with the DL MU PPDU format shown in FIG. 21 (the embodiment signaling the common boundary information and individual boundary information together). It is possible to check.
  • the method of signaling the common boundary information and the individual boundary information together may solve the ambiguity problem of the receiver for the decoding boundary that may occur when the length of the packet extension field is 12 ms or 16 ms.
  • the other STA may determine whether the last symbol of the DL MU PPDU is a data symbol or a packet extension field. It is unknown whether the signal extension symbol included in the. As a result, a problem may arise that the other STA cannot decode the DL MU PPDU when the frame included in the received DL MU PPDU is a control frame or a measurement frame. This problem can also be solved by the signaling method proposed herein.
  • the common boundary information indicates '4' as the decoding boundary value, and the individual decoding boundary field including the individual boundary information is '0' (or '1').
  • the last symbol is a data symbol (that is, in case of FIG. 22 (b))
  • the common boundary information indicates '4' as the decoding boundary value, and the individual decoding boundary field including the individual boundary information is '1' ( Or '0').
  • the STA receiving the common boundary information '4' and the individual decoding boundary field '0' may recognize that the last symbol of the received DL MU PPDU is a signal extension symbol included in the packet extension field. have.
  • the STA receiving the common boundary information '4' and the individual boundary information '1' may recognize that the last symbol of the received DL MU PPDU is the last data symbol included in the data field.
  • the signaling method proposed herein indicates whether or not the decoding boundary of the frame is the last symbol of the DL MU PPDU, and through this, the presence or absence of a packet extension field in the corresponding DL MU PPDU is indicated by other STA (or OBSS STA). Can be acknowledged.
  • the last symbol means an intact symbol that can be included in the Nsym when the Nsym is calculated using the length field (or the L_LENGTH field) transmitted through the L-SIG field. That is, the last symbol may be a data symbol having a length of Tsym, or a signal extension symbol included in a packet extension field that may be included in Nsym due to a length similar to Tsym.
  • the decoding boundary value may be signaled through the L-SIG field in addition to the HE-SIG field, which will be described later in detail.
  • the decoding boundary value described below may refer to a common decoding boundary value commonly applied to data fields for each receiving STA.
  • 23 and 24 illustrate an embodiment of signaling a decoding boundary value using an L-SIG field.
  • a decoding boundary value may be signaled using a length field of an L-SIG field.
  • the transmitter may directly indicate the decoding boundary value using the HE-SIG field as shown in FIGS. 16 to 22, but may indirectly indicate the length field of the L-SIG and an additional data processing time.
  • the receiver may obtain (or calculate) a decoding boundary value using PSDU length information included in the length field of the L-SIG and an additional data processing time required for processing data. For example, the receiver may calculate a decoding boundary value (or data length) by subtracting the length of the packet extension field corresponding to additional data processing time from the end point of the DL MU PPDU indicated by the L-SIG length field.
  • the STA when the decoding boundary value is signaled by the L-SIG field (or when the decoding boundary value is indirectly indicated by the L-SIG field), the STA is padded to have a common decoding boundary value for each STA (that is, for each STA). It may have different decoding boundary values), so that unnecessary packet extension fields do not need to be inserted (unlike in the above-described third embodiment). This will be described later with reference to FIG. 24.
  • a first data field received at STA 1 through one DL MU PPDU includes two 4x data symbols
  • a second data field received at STA 2 includes one 4x data symbol. Assume that it contains.
  • STA 1 does not require additional data processing time to decode the first data field
  • STA 2 requires additional data processing time to decode the second data field.
  • an unnecessary packet extension field 1710 does not need to be inserted.
  • padding bits should be inserted into the data field for at least one STA so as to have a common decoding boundary value (when the data length of the last data symbol is different, To reduce overhead for decoding boundary values).
  • the packet extension field should be added to another STA in consideration of the length of the packet extension field received by the STA having the poorest performance.
  • the decoding boundary value is signaled indirectly through the L-SIG field, since the decoding boundary value does not need to be transmitted separately, it is not necessary to unify the decoding boundary value into one for each receiving STA in order to reduce overhead. Accordingly, the plurality of data fields included in one DL MU PPDU may have different decoding boundary values for each receiving STA. As a result, the end points of the DL MU PPDU can be set such that the total length of the data field and the packet extension field is the same for each receiving STA (ie, without unnecessary long padding bits and / or packet extension fields being inserted (reducing overhead). The padding bit and / or packet extension field whose length has been determined may be inserted into the DL MU PPDU.
  • 25 is a flowchart illustrating a method for controlling an AP according to an embodiment of the present invention.
  • the foregoing descriptions with respect to this flowchart may be equally applicable. Therefore, hereinafter, redundant description will be omitted.
  • the AP may generate a DL MU PPDU (S2510).
  • the generated DL MU PPDU may include a physical preamble and data fields for a plurality of STAs.
  • the physical preamble may include common boundary information indicating a common decoding boundary of data fields for the plurality of STAs, and individual boundary information indicating an individual decoding boundary of each of the data fields for the plurality of STAs.
  • the AP may transmit the generated DL MU PPDU (S2520).
  • S2520 Each STA that receives the DL MU PPDU from the AP decodes the DL MU PPDU as shown in the flowchart of FIG. 26.
  • 26 is a flowchart illustrating a method for controlling a STA according to an embodiment of the present invention.
  • the foregoing descriptions with respect to this flowchart may be equally applicable. Therefore, hereinafter, redundant description will be omitted.
  • an STA may receive a DL MU PPDU from an AP (S2610).
  • the DL MU PPDU may include a physical preamble and data fields for a plurality of STAs.
  • the physical preamble may include common boundary information indicating a common decoding boundary of data fields included in a DL MU PPDU, and individual boundary information indicating an individual decoding boundary of a data field for an STA that receives the DL MU PPDU.
  • the individual boundary information may indicate that the decoding boundary value of the data field for the specific STA is '4' regardless of the common boundary information or may be the same as the value indicated by the common boundary information.
  • the common boundary information and the individual boundary information may be signaled in the HE-SIG field of the physical preamble and received by the STA.
  • the STA may process (or decode) the data field based on the common boundary information and the individual boundary information included in the physical preamble (S2620). For example, if the individual boundary information indicates that the decoding boundary value of the data field for the STA is '4' irrespective of the common boundary information (i.e., indicates 4/4 point of the last data symbol of the data field).
  • the STA may process the data field by recognizing the decoding value as '4' regardless of the received common boundary information. Accordingly, the STA can decode the last data symbol included in the data field to 4x symbol length (or up to 4/4 points of the last data symbol).
  • the STA may decode the data field according to the decoding boundary value indicated by the received common boundary information. Accordingly, the STA may decode the last data symbol included in the data field up to 1x, 2x, or 3x symbol lengths (or up to 1/4, 2/4, or 3/4 points of the last data symbol).
  • 27 is a block diagram of each STA apparatus according to an embodiment of the present invention.
  • the STA apparatus 2710 may include a memory 2712, a processor 2711, and an RF unit 2713.
  • the STA device may be an AP or a non-AP STA as an HE STA device.
  • the RF unit 2713 may be connected to the processor 2711 to transmit / receive a radio signal.
  • the RF unit 2713 may up-convert data received from the processor 2711 into a transmission / reception band to transmit a signal.
  • the processor 2711 may be connected to the RF unit 2713 to implement a physical layer and / or a MAC layer according to the IEEE 802.11 system.
  • the processor 2711 may be configured to perform operations according to various embodiments of the present disclosure according to the above-described drawings and descriptions.
  • a module implementing the operation of the STA 2710 according to various embodiments of the present disclosure described above may be stored in the memory 2712 and executed by the processor 2711.
  • the memory 2712 is connected to the processor 2711 and stores various information for driving the processor 2711.
  • the memory 2712 may be included in the processor 2711 or may be installed outside the processor 2711 and may be connected to the processor 2711 by a known means.
  • the STA apparatus 2710 may include a single antenna or multiple antennas.
  • the specific configuration of the STA apparatus 2710 of FIG. 27 may be implemented so that the above-described matters described in various embodiments of the present invention may be independently applied or two or more embodiments may be simultaneously applied.
  • each component or feature is to be considered optional unless stated otherwise.
  • Each component or feature may be embodied in a form that is not combined with other components or features. It is also possible to combine some of the components and / or features to form an embodiment of the invention.
  • the order of the operations described in the embodiments of the present invention may be changed. Some components or features of one embodiment may be included in another embodiment or may be replaced with corresponding components or features of another embodiment. It is obvious that the claims may be combined to form an embodiment by combining claims that do not have an explicit citation relationship in the claims or as new claims by post-application correction.
  • Embodiments according to the present invention may be implemented by various means, for example, hardware, firmware, software, or a combination thereof.
  • an embodiment of the present invention may include one or more application specific integrated circuits (ASICs), digital signal processors (DSPs), digital signal processing devices (DSPDs), programmable logic devices (PLDs), FPGAs ( field programmable gate arrays), processors, controllers, microcontrollers, microprocessors, and the like.
  • ASICs application specific integrated circuits
  • DSPs digital signal processors
  • DSPDs digital signal processing devices
  • PLDs programmable logic devices
  • FPGAs field programmable gate arrays
  • processors controllers, microcontrollers, microprocessors, and the like.
  • an embodiment of the present invention may be implemented in the form of a module, procedure, function, etc. that performs the functions or operations described above.
  • the software code may be stored in memory and driven by the processor.
  • the memory may be located inside or outside the processor, and may exchange data with the processor by various known means.
  • the present invention can be applied to various wireless communication systems in addition to the IEEE 802.11 system.

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

Abstract

Selon la présente invention, dans un procédé transmission à multi-utilisateur (MU) à liaison descendante (DL) pour un dispositif de point d'accès (AP) dans un système sans fil LAN (WLAN) selon un mode de réalisation de la présente invention, la présente invention comprend les étapes consistant : à générer une PPDU MU DL (unité de données de protocole physique) comprenant des champs de données sur un préambule physique et une pluralité de STA; et à transmettre la PPDU MU DL. Le préambule physique peut comprendre les étapes : des informations de limite commune pour ordonner un décodage de limite commune à des champs de donnés pour la pluralités de STA; et des informations de limite individuelle pour ordonner une limite de décodage pour chacun des champs de données pour la pluralité de STA.
PCT/KR2016/001866 2015-06-01 2016-02-25 Procédé de transmission de données dans un système de communication sans fil et son appareil Ceased WO2016195214A1 (fr)

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