WO2011115431A2 - Procédé et appareil pour une communication dans un système de réseau local sans fil - Google Patents

Procédé et appareil pour une communication dans un système de réseau local sans fil Download PDF

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Publication number
WO2011115431A2
WO2011115431A2 PCT/KR2011/001850 KR2011001850W WO2011115431A2 WO 2011115431 A2 WO2011115431 A2 WO 2011115431A2 KR 2011001850 W KR2011001850 W KR 2011001850W WO 2011115431 A2 WO2011115431 A2 WO 2011115431A2
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sta
sounding ppdu
ppdu
transmission
frame
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English (en)
Korean (ko)
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WO2011115431A3 (fr
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강병우
석용호
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LG Electronics Inc
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LG Electronics Inc
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    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B7/00—Radio transmission systems, i.e. using radiation field
    • H04B7/02—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas
    • H04B7/04—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas
    • H04B7/06—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas at the transmitting station
    • H04B7/0613—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas at the transmitting station using simultaneous transmission
    • H04B7/0615—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas at the transmitting station using simultaneous transmission of weighted versions of same signal
    • H04B7/0619—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas at the transmitting station using simultaneous transmission of weighted versions of same signal using feedback from receiving side
    • H04B7/0636—Feedback format
    • H04B7/0643—Feedback on request

Definitions

  • the present invention relates to wireless communication, and more particularly, to a communication method and a device supporting the same in a WLAN system.
  • Wireless LAN is based on radio frequency technology, using a portable terminal such as a personal digital assistant (PDA), a laptop computer, a portable multimedia player (PMP), or the like. It is a technology that allows wireless access to the Internet in a specific service area.
  • PDA personal digital assistant
  • PMP portable multimedia player
  • IEEE 802.11 improves Quality of Service (QoS), access point protocol compatibility, security enhancement, radio resource measurement, and wireless access vehicular environment. Standards of various technologies such as, fast roaming, mesh network, interworking with external network, and wireless network management are being put into practice.
  • IEEE 802.11n In order to overcome the limitation of communication speed, which has been pointed out as a weak point in WLAN, IEEE 802.11n is a relatively recent technical standard. 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) with data throughput of up to 540 Mbps and also uses multiple antennas at both the transmitter and receiver to minimize transmission errors and optimize data rates. It is based on Multiple Inputs and Multiple Outputs (MIMO) technology. In addition, the standard not only uses a coding scheme for transmitting multiple duplicate copies to increase data reliability, but may also use orthogonal frequency division multiplex (OFDM) to increase the speed.
  • HT High Throughput
  • MIMO Multiple Inputs and Multiple Outputs
  • OFDM orthogonal frequency division multiplex
  • HT High Throughput
  • PPDU Physical Layer Convergence Procedure
  • PPDU Protocol Data Unit
  • STA legacy stations
  • An HT green field PPDU format is introduced, which is a PPDU format efficiently designed for HT STAs that can be used in the system.
  • the legacy STA and the HT STA support the HT mixed PPDU format, which is a PPDU format designed to support the HT system in a coexisting system.
  • VHT Very High Throughput
  • SAP MAC Service Access Point
  • the VHT WLAN system allows a plurality of VHT STAs to access and use the channel at the same time in order to use the wireless channel efficiently. To this end, it supports transmission of MU-MIMO (Multi User-Multiple Input Multiple Output) using multiple antennas.
  • a VHT access point (AP) may perform spatial division multiple access (SDMA) transmission for simultaneously transmitting spatial multiplexed data to a plurality of VHT STAs.
  • SDMA spatial division multiple access
  • a plurality of spatial streams may be distributed to a plurality of STAs to simultaneously transmit data to increase the overall throughput of the WLAN system.
  • the AP In a multi-user environment in which one AP supports a plurality of STAs, research has been conducted on a multi-transmit / receive antenna transmission technology considering a multi-user to increase the total channel capacity of the MU-MIMO system considering the multi-user.
  • the multi-user channel environment must ensure that the channel matrix is in good condition so that all MU-MIMO techniques can fully exploit the spatial freedom, so that multiple users can communicate simultaneously at the desired rate without being limited by interference. It is required to be.
  • the AP In the downlink channel, the AP simultaneously transmits radio signals to several STAs, so that each STA receives a signal of another user in addition to a desired signal, which may act as interference.
  • interference may be removed by filtering channels at the AP. For example, zero-forcing filters may be used to mitigate interference.
  • the VHT WLAN system may support a wider bandwidth in the HT WLAN system.
  • the AP in order to transmit and receive signals through multiple antennas, it is necessary to estimate a channel between a transmitter and a receiver.
  • the AP may request information required for channel estimation from one STA and receive the necessary information corresponding thereto to estimate the channel.
  • the next generation WLAN system supports MU-MIMO, each channel for a plurality of STAs must be estimated. Accordingly, a mechanism for estimating a channel by requesting information required for channel estimation from a plurality of STAs and receiving a response thereto is required.
  • the technical problem to be solved by the present invention is to estimate the channels for a plurality of STAs in a wireless LAN system that supports MU-MIMO (Multi User-Multiple Input Multiple Output) and through this can perform wireless communication through MU-MIMO transmission To provide a method and a device supporting the same.
  • MU-MIMO Multi User-Multiple Input Multiple Output
  • a communication method by an access point (AP) in a WLAN system requests a first station (STA) and a second STA to transmit a Sounding (Physical Layer Convergence Procedure) Protocol Data Unit (PLCP) protocol for channel estimation and a first STA from the first STA.
  • STA station
  • PLCP Physical Layer Convergence Procedure
  • Requesting the transmission of the sounding PPDU is performed by aggregating a first request frame for requesting the sounding PPDU transmission to the first STA and a second request frame for requesting the sounding PPDU transmission to the second STA.
  • Aggregated-Frame includes transmitting to the first STA and the second STA.
  • the first request frame may include training request (TRQ) indication information indicating whether to transmit the sounding PPDU.
  • TRQ training request
  • the first request frame may include STA identification information for identifying the first STA.
  • the STA identification information may indicate an association ID (AID), which is an identifier in a PHY layer allocated when the first STA is associated with the AP.
  • AID association ID
  • the method estimates a channel based on the first sounding PPDU and the second sounding PPDU to obtain channel information for multi-user multiple input multiple output (MU-MIMO) transmission.
  • the method may further include transmitting data to the second STA through a MU-MIMO transmission method.
  • a communication method by an AP in a WLAN system includes requesting transmission of a sounding PPDU for channel estimation to a first STA and a second STA, receiving a first sounding PPDU from the first STA, and receiving a second sounding PPDU from the second STA. It includes.
  • the request for transmission of the sounding PPDU is performed by broadcasting one request frame to the first STA and the second STA.
  • the request frame may include first control information for the first STA and second control information for the second STA.
  • the first control information may include TRQ indication information indicating whether to transmit the sounding PPDU.
  • the first control information may include STA identification information for identifying the first STA.
  • the STA identification information may indicate an AID which is an identifier in a physical layer allocated when the first STA is combined with the AP.
  • the STA identification information may indicate a medium access control (MAC) address of the first STA.
  • MAC medium access control
  • the method obtains channel information for MU-MIMO transmission by estimating a channel based on the first sounding PPDU and the second sounding PPDU, and MU-MIMO data to the first STA and the second STA.
  • the method may further include transmitting through a transmission method.
  • a wireless device in another aspect, includes an RF unit for transmitting or receiving a frame and a processor operatively connected to the RF unit.
  • the processor requests a first STA and a second STA to transmit a sounding PPDU for channel estimation, to receive a first sounding PPDU from the first STA, and to receive a second sounding PPDU from the second STA. Is set. Requesting the transmission of the sounding PPDU is performed by aggregating a first request frame for requesting the sounding PPDU transmission to the first STA and a second request frame for requesting the sounding PPDU transmission to the second STA. And sending an aggregation-frame to the first STA and the second STA.
  • a wireless device In another aspect, a wireless device is provided.
  • An RF unit for transmitting or receiving a frame; And,
  • the processor requests a first STA and a second STA to transmit a sounding PPDU for channel estimation, to receive a first sounding PPDU from the first STA, and to receive a second sounding PPDU from the second STA. Is set.
  • the request for transmission of the sounding PPDU is performed by broadcasting one request frame to the first STA and the second STA.
  • a method and apparatus for acquiring channel information for a plurality of STAs may be provided to increase the efficiency of using a wireless medium, thereby improving throughput and data transmission reliability of the WLAN system.
  • FIG. 1 is a diagram illustrating a physical layer architecture of IEEE 802.11.
  • FIG. 2 is a block diagram illustrating an example of a PPDU format used in a WLAN system to which the IEEE 802.11n standard is applied.
  • 3 is a diagram illustrating an orthogonal mapping matrix applied according to a channel layer.
  • FIG. 4 is a flowchart illustrating a method of obtaining channel information.
  • FIG. 5 is a block diagram illustrating an example of a management frame format including a TRQ message.
  • FIG. 6 is a block diagram illustrating an example of an NDP PPDU format.
  • FIG. 7 is a block diagram illustrating an example of a PPDU format used in a next generation WLAN system.
  • FIG. 8 is a view showing a channel information acquisition method according to an embodiment of the present invention.
  • FIG. 9 is a block diagram illustrating an example of a format of an A-MPDU that may be used in an embodiment of the present invention.
  • FIG. 10 is a block diagram illustrating an example of a management frame format according to an embodiment of the present invention.
  • FIG. 11 illustrates an example of a VHT control field format that can be applied to an embodiment of the present invention.
  • FIG. 12 is a block diagram illustrating a wireless device to which an embodiment of the present invention can be applied.
  • a wireless local area network (WLAN) system in which an embodiment of the present invention is implemented includes at least one basic service set (BSS).
  • BSS is a collection of stations (STAs) that have been successfully synchronized to communicate with each other.
  • STAs stations
  • BSS can be classified into Independent BSS (IBSS) and Infrastructure BSS.
  • the BSS includes at least one STA and an Access Point (AP).
  • the AP is a functional medium that provides a connection through a wireless medium for each STA in the BSS.
  • the AP may be called by other names such as a centralized controller, a base station (BS), a scheduler, and the like.
  • a STA is any functional medium that includes a medium access control (MAC) and a wireless-medium physical layer (PHY) interface that meets the IEEE 802.11 standard.
  • the STA may be an AP or a non-AP STA, but refers to a non-AP STA unless otherwise indicated below.
  • the STA may be classified into Very High Throughput (VHT) -STA, High Throughput (HT) -STA, and L (Legacy) -STA.
  • VHT Very High Throughput
  • HT High Throughput
  • L Legacy
  • the HT-STA refers to an STA supporting IEEE 802.11n
  • the L-STA refers to a STA supporting a lower version of IEEE 802.11n, for example, IEEE 802.11a / b / g.
  • L-STA is also called non-HT STA.
  • FIG. 1 is a diagram illustrating a physical layer architecture of IEEE 802.11.
  • the PHY architecture of IEEE 802.11 includes a PHY Layer Management Entity (PLME), a Physical Layer Convergence Procedure (PLCP) sublayer 110, and a Physical Medium Dependent (PMD) sublayer 100.
  • PLME cooperates with the MAC Layer Management Entity (MLME) to provide the management of the physical layer.
  • the PLCP sublayer 110 transfers the MAC Protocol Data Unit (MPDU) received from the MAC sublayer 120 to the sublayer between the MAC sublayer 120 and the PMD sublayer 100 according to an instruction of the MAC layer.
  • the frame coming from the PMD sublayer 100 is transferred to the MAC sublayer 120.
  • the PMD sublayer 100 is a PLCP lower layer to enable transmission and reception of physical layer entities between two stations through a wireless medium.
  • the MPDU delivered by the MAC sublayer 120 is referred to as a physical service data unit (PSDU) in the PLCP sublayer 110.
  • PSDU physical service data unit
  • the MPDU is similar to the PSDU. However, when an A-MPDU (aggregated MPDU) that aggregates a plurality of MPDUs is delivered, the individual MPDUs and the PSDUs may be different from each other.
  • A-MPDU aggregated MPDU
  • the PLCP sublayer 110 adds an additional field including information required by the physical layer transceiver in the process of receiving the PSDU from the MAC sublayer 120 and transmitting it to the PMD sublayer 100.
  • the added field may be a PLCP preamble, a PLCP header, and tail bits required on the data field.
  • the PLCP preamble serves to prepare the receiver for synchronization and antenna diversity before the PSDU is transmitted.
  • the PLCP header includes a field including information on a PLC Protocol Data Unit (PPDU) to be transmitted, which will be described in detail later with reference to FIG. 2.
  • PPDU PLC Protocol Data Unit
  • the PLCP sublayer 110 adds the above-described fields to the PSDU, generates a PPDU (PLCP Protocol Data Unit), and transmits the data to the receiving station via the PMD sublayer, and the receiving station receives the PPDU to receive data from the PLCP preamble and PLCP header. Obtain and restore information necessary for restoration.
  • PPDU PLCP Protocol Data Unit
  • FIG. 2 is a block diagram illustrating an example of a PPDU format used in a WLAN system to which the IEEE 802.11n standard is applied.
  • the sub-figure (a) shows a legacy PPDU (L-PPDU) format, which is a PPDU used in the existing IEEE 802.11a / b / g. Therefore, in a WLAN system to which the IEEE 802.11n standard is applied, the L-STA may transmit and receive an L-PPDU having such a format.
  • L-PPDU legacy PPDU
  • the L-PPDU 210 includes an L-STF 211, an L-LTF 212, an L-SIG field 213, and a data field 214.
  • the L-STF 211 is used for frame timing acquisition, automatic gain control (AGC) convergence, coarse frequency acquisition, and the like.
  • the L-LTF 212 is used for frequency offset and channel estimation.
  • the L-SIG field 213 includes control information for demodulating and decoding the data field 214.
  • Sub-batch (b) is a block diagram of an HT-mixed PPDU format that allows L-STA and HT-STA to coexist.
  • the HT mixed PPDU 220 includes the L-STF 221, the L-LTF 222, the L-SIG 223, the HT-SIG 224, the HT-STF 225, and the HT mixed PPDU 220.
  • L-STF 221, L-LTF 222, and L-SIG field 223 are the same as indicated by reference numerals 211, 212, and 213 in sub-view (a), respectively. Accordingly, the L-STA may interpret the data field through the L-LTF 222, the L-LTF 222, and the L-SIG 223 even when the HT mixed PPDU 220 is received.
  • the L-LTF field 223 is a channel for the HT-STA to perform to receive the HT mixed PPDU 220 and to decode the L-SIG field 223, HT-SIG 224, and HT-STF 225. It may further include information for estimation.
  • the HT-STA knows that the HT mixed PPDU 220 is a PPDU for itself through the HT-SIG 224 following the L-SIG 223, and based on this, the HT-STA can demodulate and decode the data field 227. Can be.
  • the HT-STF 225 may be used for frame timing synchronization, AGC convergence, etc. for the HT-STA.
  • the HT-LTF 226 may be used for channel estimation for demodulation of the data field 227. Since IEEE 802.11n supports SU-MIMO, a plurality of HT-LTFs 226 may be configured for channel estimation for each data field transmitted in a plurality of spatial streams.
  • the HT-LTF 226 may be configured with Data HT-LTF used for channel estimation for spatial streams and extension HT-LTF (Additional HT-LTF) additionally used for full channel sounding. have. Accordingly, the plurality of HT-LTFs 226 may be equal to or greater than the number of spatial streams transmitted.
  • the HT-mixed PPDU 220 receives the L-STA and L-STF 221, L-LTF 222 and L-SIG field 223 is transmitted first to enable the acquisition of data. Thereafter, the HT-SIG field 224 is transmitted for demodulation and decoding of data transmitted for the HT-STA.
  • the HT-SIG field 224 is transmitted without performing beamforming so that the L-STA and the HT-STA receive the corresponding PPDU to acquire data, and then the HT-STF 225 and the HT- The LTF 226 and the data field 227 perform wireless signal transmission through precoding.
  • the HT-STF 225 is transmitted to the STA receiving the precoding, and the HT-STF 225 can be taken into consideration so that the power due to the precoding is variable.
  • the HT-LTF 226 and the data fields 227 are transmitted. do.
  • the HT-STA using 20 MHz in the HT WLAN system uses 52 data subcarriers per OFDM symbol
  • the L-STA using the same 20 MHz still uses 48 data subcarriers per OFDM symbol.
  • the HT-SIG field 224 is decoded using the L-LTF 222 in the HT mixed PPDU 220 format to support backward compatibility, the HT-SIG field 224 is 48 It consists of 2 data subcarriers.
  • the HT-STF 225 and the HT-LTF 226 consist of 52 data subcarriers per OFDM symbol.
  • each HT-SIG field 224 is composed of 24 bits and is transmitted in a total of 48 bits. That is, the channel estimation for the L-SIG field 223 and the HT-SIG field 224 uses the L-LTF 222, and the bit string constituting the L-LTF 222 is expressed by Equation 1 below. .
  • the L-LTF 222 is composed of 48 data subcarriers except the DC subcarrier per symbol.
  • the sub-view (c) is a block diagram showing the HT-Greenfield PPDU 230 format that only the HT-STA can use.
  • the HT-GF PPDU 230 includes the HT-GF-STF 231, HT-LTF1 232, HT-SIG 233, a plurality of HT-LTF2 234, and data fields. 235.
  • the HT-GF-STF 231 is used for frame timing acquisition and AGC.
  • HT-LTF1 232 is used for channel estimation.
  • the HT-SIG 233 is used for demodulation and decoding of the data field 235.
  • HT-LTF2 234 is used for channel estimation for demodulation of data field 235.
  • HT-STA uses SU-MIMO, channel estimation is required for each data field transmitted in a plurality of spatial streams, and thus, HT-LTF 226 may be configured in plural.
  • the plurality of HT-LTF2 234 may be composed of a plurality of Data HT-LTF and a plurality of extended HT-LTF, similar to the HT-LTF 226 of the HT mixed PPDU 220.
  • Each data field 214, 227, 235 shown in sub-views (a), (b) and (c) may include a service field, scrambled PSDU, tail bit, and padding bit, respectively.
  • HT-LTF is defined for channel estimation for MIMO use.
  • HT-LTF is used for channel estimation like L-LTF, but the difference is that MIMO channel can be estimated.
  • the orthogonal mapping matrix PHTLTF is multiplied by the HT-LTF.
  • PHTLTF is composed of 1 and -1 can be represented by the following equation (2).
  • the orthogonal mapping matrix is applied in different sizes according to the channel layer, which is referred to FIG. 3.
  • 3 is a diagram illustrating an orthogonal mapping matrix applied according to a channel layer.
  • training symbols are defined in units of spatial streams and are transmitted for channel estimation of each spatial stream.
  • the number of spatial streams is 1, 2, 4, 1, 2, 4 HT-LTFs are transmitted.
  • the number of spatial streams is 3, one extra long training symbol is used.
  • four HT-LTFs can be used.
  • an AP and / or STA that wants to transmit / receive a PPDU using a MIMO transmission method needs to know channel information between a sender and a receiver.
  • the sender may perform channel estimation.
  • Channel estimation may be performed based on training symbols of a physical layer convergence procedure (PLCP) preamble of a sounding PPDU (sounding PPDU) transmitted from a receiver. More specifically, the operation may be performed based on the HT-LTF 226 shown in FIG. 2 (b).
  • the HT-LTF used for channel estimation may be determined by the total number of antennas of the receiver or the number of spatial streams transmitted.
  • FIG. 4 is a flowchart illustrating a method of obtaining channel information.
  • the AP 410 transmits a training request (TRQ) message to the STA 420 to request channel information (S410).
  • TRQ training request
  • the TRQ message transmission may be performed by transmitting a management frame, which is one of types of MAC frames. This will be described in more detail with reference to the management frame format shown in FIG. 5.
  • FIG. 5 is a block diagram illustrating an example of a management frame format including a TRQ message.
  • the management frame 500 may include a frame control field 510, a duration / idifier field 520, an address field 530, and a transport frame control.
  • a frame control (540) field a HT control (High Throughput control) field 550, a carrier frame field (560), and a frame check sequence (FCS) field 570.
  • FCS frame check sequence
  • the frame control field 510 includes control information for the management frame 500.
  • the persistence / ID field 520 may include an association ID (AID) of the STA and / or the AP transmitting the duration and / or management frame 500 necessary for the delivery of the management frame 500.
  • AID association ID
  • the address field 530 includes information for identifying an STA that receives the management frame 500 and may typically indicate a MAC address of the corresponding STA.
  • the delivery frame control field 540 may include a frame control field value for a specific frame to be managed by the management frame 500.
  • the HT control field 550 includes subfields containing control information for supporting HT.
  • the HT control field 550 includes a link adaptation control subfield 551, a calibration position subfield 552, a calibration sequence subfield 553, and channel state information. ) / steering subfield 554, NDP announcement subfield 555, Access Category constraint subfield 556, and Reverse Direction Grant / more PPDU subfield 557. do.
  • the calibration location subfield 552 indicates whether the frame is a frame for calibration and whether the calibration is in progress.
  • the calibration sequence subfield 553 contains identification information about the progress of the calibration procedure.
  • CSI / steering subfield 554 indicates the type of feedback.
  • NDP notification subfield 555 indicates that an NDP PPDU will be sent after a management frame.
  • the AC restriction subfield 556 indicates whether the AC of the reverse direction (RD) data frame is limited to only one AC.
  • the RDG / more PPDU subfield 557 may be interpreted differently depending on whether the management frame 500 was sent by an RD initiator or by an RD responder.
  • the RDG / more PPDU indicates whether there is an RDG.
  • the RD responder transmits a management frame, it may indicate whether the PPDU carrying the management frame is the last PPDU transmitted by the RD responder or whether another PPDU is to be transmitted after that.
  • the link adaptation control subfield 551 may include a TRQ subfield 551a, a Modulation and Coding Scheme (MCS) request or an Antenna Selection (ASEL) subfield 551b, and a MCS Feedback Sequence Identifier (MFSI) subfield 551c. And an MCS Feedback and Antenna Selection Command / data (MFB / ASELC) subfield 551d.
  • MCS Modulation and Coding Scheme
  • ASEL Antenna Selection
  • MCSI MCS Feedback Sequence Identifier
  • the TRQ subfield 551a indicates whether to request an STA to receive the management frame 500 to transmit a sounding PPDU.
  • the management frame 500 may be used for TRQ message transmission according to the value of the TRQ subfield 551a.
  • the MAI subfield 551b includes information for whether to request a Modulation and Coding Scheme (MCS) and for identifying a detailed request when requesting an MCS.
  • MCS Modulation and Coding Scheme
  • the MFSI subfield 551c contains information about the identifier of the MCS feedback sequence.
  • the MFB / ASLEC subfield 551d contains information about NCS feedback and ASEL command / ASEL data.
  • the STA When the STA receives the management frame 500, the STA checks the value of the TRQ subfield 551a of the link adaptation control subfield 551 included in the HT control field 550 to determine whether the management frame is a TRQ message. can do.
  • the STA 410 receiving the TRQ message transmits a sounding PPDU to the AP 420 in response to the TRQ message (S420).
  • the sounding PPDU may be distinguished from the general PPDU through a bit value indicated by the sounding indication subfield included in the HT-SIG field 224 in the PPDU 210 illustrated in FIG. 2.
  • the AP may estimate the MIMO channel through the HT-LTF (more generally, training symbol) included in the sounding PPDU.
  • An example of a sounding PPDU transmitted by an STA is a NDP (Null Data Packet) PPDU.
  • the NDP PPDU indicates that the sounding indication subfield indicates that the corresponding PPDU is for sounding and is a PPDU having no data field.
  • the format of the NDP PPDU may refer to FIG. 6.
  • FIG. 6 is an example of an NDP PPDU format, which corresponds to a format in which data fields are excluded from the format of the HT-Green field PPDU of FIG. 2.
  • VHT Very High Throughput
  • MU-MIMO Multi User-Multiple Input Multiple Output
  • the amount of control information transmitted to STAs for MU-MIMO transmission may be relatively large compared to the amount of IEEE 802.11n control information.
  • the number of spatial streams that each STA should receive, and modulation and coding information of data transmitted for each STA may correspond to control information required for the VHT WLAN system. Accordingly, when MU-MIMO transmission is performed to simultaneously service data to a plurality of STAs, control information to be transmitted may be increased according to the number of receiving STAs.
  • FIG. 7 is a block diagram illustrating an example of a PPDU format used in a next generation WLAN system.
  • the PPDU 700 includes an L-STF 710, an L-LTF 720, an L-SIG field 730, a VHT-SIGA field 740, a VHT-STF 750, and a VHT-. It may include an LTF 760, a VHT-SIGB field 770, and a data field 780.
  • the PLCP sublayer adds the necessary information to the PSDU received from the MAC layer and converts the information into a data field 780 and converts the L-STF 710, L-LTF 720, L-SIG field 730, and VHT-SIGA field ( 740), the VHT-STF 750, the VHT-LTF 760, the VHT-SIGB 770, etc., are added to generate the PPDU 700 and transmit it to one or more STAs through the PMD layer.
  • the L-STF 710 is used for frame timing acquisition, automatic gain control (AGC) convergence, coarse frequency acquisition, and the like.
  • AGC automatic gain control
  • the L-LTF 720 is used for channel estimation for demodulation of the L-SIG field 730 and the VHT-SIGA field 740.
  • L-SIG field 730 is used by the L-STA to receive the PPDU to obtain data.
  • the VHT-SIGA field 740 is common control information required for the VHT-STAs paired with the AP and includes the control information for interpreting the received PPDU 700.
  • the VHT-SIGA field 740 may include information on spatial streams for each of a plurality of MIMO paired STAs, bandwidth information, identification information on whether or not to use Space Time Block Coding (STBC), and identification of STA groups.
  • Information Group Identifier
  • information on the STA to which each group identifier is assigned and short GI (Guard Interval) related information.
  • the identification information (Group Identifier) for the STA group may include whether the currently used MIMO transmission method is MU-MIMO or SU-MIMO.
  • the VHT-STF 750 is used to improve the performance of AGC estimation in MIMO transmission.
  • VHT-LTF 760 is used by the STA to estimate the MIMO channel. Since the VHT WLAN system supports MU-MIMO, the VHT-LTF 760 may be set as many as the number of spatial streams in which the PPDU 700 is transmitted. Additionally, full channel sounding is supported and the number of VHT LTFs can be greater if this is performed.
  • the VHT-SIGB field 770 includes dedicated control information required for a plurality of MIMO paired STAs to receive the PPDU 700 and acquire data. Therefore, the STA may be designed to decode the VHT-SIGB field 770 only when the common control information included in the VHT-SIGB field 770 indicates that the currently received PPDU 700 is MU-MIMO transmitted. Can be. Conversely, the STA may be designed not to decode the VHT-SIGB field 770 when the common control information indicates that the currently received PPDU 700 is for a single STA (including SU-MIMO).
  • the VHT-SIGB field 770 includes information on modulation, encoding, and rate-matching of each STA.
  • the size of the VHT-SIGB field 770 may vary depending on the type of MIMO transmission (MU-MIMO or SU-MIMO) and the channel bandwidth used for PPDU transmission.
  • the AP In order to transmit MU-MIMO supported by the next generation WLAN system, the AP must acquire channel information about each of a plurality of MIMO paired STAs. Therefore, when the existing channel information acquisition method is applied as it is, the TRQ message is instantaneously sent to each STA. Therefore, when the number of paired STAs increases, the time for occupying radio resources for transmitting the TRQ message becomes long, which may cause a problem of lowering the throughput of the entire WLAN system. Therefore, a channel information acquisition method that can be appropriately applied to the next generation WLAN system is required.
  • FIG. 8 is a view showing a channel information acquisition method according to an embodiment of the present invention.
  • the AP 810 transmits a TRQ message to a plurality of MIMO paired STAs 820 and 830.
  • the MIMO paired STAs 820 and 830 transmit sounding PPDUs to the AP in response to the TRQ message (S820 and S830).
  • the AP 810 may perform channel estimation and obtain channel information based on the sounding PPDU.
  • the AP 810 may simultaneously transmit a TRQ message to a plurality of MIMO paired STAs 820 and 830 (S810).
  • the transmission of the TRQ message may be performed by transmitting a management frame.
  • the present invention proposes a method of transmitting a management frame to a plurality of MIMO paired STAs while transmitting a TRQ message and simultaneously transmitting a TRQ message to a plurality of MIMO paired STAs.
  • A-MPDU Aggregate-MAC Protocol Data Unit
  • the A-MPDU includes a plurality of management frames to be transmitted to a plurality of MIMO paired STAs.
  • Each management frame may include a frame control field, a persistent / ID field, an address field, a delivery frame control field, a VHT control field, a delivery frame field, and an FCS field, and the VHT control field may include information related to a TRQ message. Can be. This will be described in more detail with reference to FIG. 9.
  • FIG. 9 is a block diagram illustrating an example of a format of an A-MPDU that may be used in an embodiment of the present invention.
  • the A-MPDU format is illustrated as including four management frames on the assumption that four STAs are a MIMO paired WLAN system with the AP.
  • the A-MPDU format includes a management frame that can be included in the A-MPDU. The number is not particularly limited.
  • the A-MPDU 800 includes management frames 910, 920, 930, and 940 to be transmitted to a MIMO paired STA.
  • the number of management frames included in the A-MPDU may change according to the number of STAs that are paired with the AP and the MIMO. In the drawing, two management frames are included in the A-MPDU.
  • the management frame includes a TRQ message for the MIMO paired STA.
  • Management frame 1 corresponds to STA1 and management frame 2 corresponds to a frame intended to be transmitted to STA2.
  • the management frame 910 includes a frame control field 911, a persistence / ID field 912, an address field 913, a forwarding frame control field 914, a VHT control field 915, a forwarding frame field 916, and an FCS. Field 917.
  • the frame control field 911, the persistence / ID field 912, the forwarding frame control field 914, the forwarding frame field 916, and the FCS field 917 are indicated by 510, 520, 540, 560, and 570 of FIG. 5. Each field is the same, so detailed description thereof will be omitted.
  • the address field 913 indicates the MAC address of the STA corresponding to each management frame. Accordingly, the address field of management frame 1 indicates the MAC address of STA1 and the address field of management frame 2 indicates the MAC address of STA2.
  • the VHT control field 915 is similar to the HT control field 550 of FIG. 5, but may include a reserved bit of the HT control field 550 as an HT / VHT indicator subfield 915a. have. This indicates whether the corresponding management frame is in a format related to HT or a format related to VHT.
  • the VHT control field 915 includes an HT / VHT indicator subfield 915a, a TRQ subfield 915b, an MAI subfield 915c, an MFSI subfield 915d, and an MFB / ASELC subfield 915d.
  • the HT / VHT indicator subfield 915a indicates whether the management frame 910 is in a format related to HT or a format related to VHT. This may be implemented by including additional fields or by setting the reserved bits of the existing HT control field 550 to the HT / VHT indicator subfield.
  • the TRQ subfield 915b, the MAI subfield 915c, the MFSI subfield 915d, and the MFB / ASELC subfield 915e are fields 551a and 551b included in the HT control field 950 shown in FIG. 551c, 551d).
  • the MFB / ASELC field 915e may include recommended MFB related information, which is represented as HT MCS when the HT / VHT indicator field 915a indicates that the management frame is in a format related to HT. If 915a indicates that the management frame is in a format related to VHT, the management frame may include information indicating the number of the recommended VHT MCS and the number of recommended space time streams.
  • the STA paired with the AP may know which management frame is a management frame for itself through the address field 913 of the included management frame.
  • the STA may transmit a sounding PPDU to the AP when the TRQ subfield included in the VHT control field in the management frame indicates to transmit the sounding frame. Accordingly, the AP may receive the sounding PPDU from the MIMO paired STA to obtain channel information after channel estimation.
  • TRQ message transmission through A-MPDU transmission may transmit a TRQ message to a plurality of MIMO paired STAs at the same time, but when the number of STAs increases, the number of management frames included therein increases. Therefore, using A-MPDU has a problem of increasing the amount of MAC header overhead. This is because the control field of the MAC frame is additionally included as the amount of MPDUs to be aggregated increases. Therefore, instead of aggregating each management frame to be transmitted to each MIMO paired STA, a method of transmitting a TRQ message by defining one new management frame is proposed.
  • FIG. 10 is a block diagram illustrating an example of a management frame format according to an embodiment of the present invention.
  • the management frame 1100 includes a frame control field 1110, a persistence / ID field 1020, an address field 1030, a delivery frame control field 1040, a plurality of VHT control fields 1050, And includes a delivery frame field 1060 and an FCS field 1070.
  • the frame control field 1110, the persistence / ID field 1020, the address field 1030, the delivery frame control field 1040, the delivery frame field 1060, and the FCS field 1070 are included in the management frame of FIG. 9 described above. Since the included fields 911, 912, 913, 914, 916, and 917 are the same, detailed descriptions thereof will be omitted.
  • the management frame 1000 is transmitted to an unspecified STA adjacent to the AP, not the MIMO paired specific STA, and the STA interprets the management frame 1000 to determine whether the management frame 1000 is a frame for itself. It may be set to a broadcast address rather than an identifier (eg MAC address or AID).
  • the management frame 1000 includes a plurality of VHT control fields 1050.
  • Each VHT control field 951, 952 constituting the plurality of VHT control fields 1050 includes control information to be delivered to each target STA intended to receive the management frame 1000.
  • the VHT control field 1050 includes information about a TRQ message requesting sounding PPDU transmission.
  • the VHT control field may include STA identification information for distinguishing between a TRQ message and a request message for which STA.
  • the number of VHT control fields included may vary depending on the number of target STAs to which the AP intends to transmit a TRQ message.
  • the number of VHT control fields can be known through the frame control field or other signals.
  • the VHT control field may include subfields 915a, 915b, 915c, 915d, and 915e included in the VHT control field of FIG. 9. More specifically, it includes a TRQ subfield 1051a and a STA identifier subfield 1051b associated with the TRQ message.
  • the TRQ subfield 1051a includes information indicating whether the transmitted management frame 1000 is a TRQ message requesting the STA to transmit a sounding PPDU.
  • the STA identifier subfield 1051b includes identification information that enables the STA to receive the management frame 1000 and determine which of the plurality of VHT control fields is for the corresponding STA.
  • STA1 may recognize that the VHT control field 1 1051a is a field for itself through an interpretation of the STA identifier subfield 1051b.
  • the STA identifier subfield may include the MAC address of the STA and / or an association identifier (AID) allocated when the STA associates with the AP as identification information of the STA.
  • VHT control field 10 may be implemented by further adding a STA identification information subfield to the existing HT control field.
  • adding a subfield increases the overall size of the VHT control field, which may increase overhead.
  • the VHT control field applicable to the embodiment of the present invention may be implemented by reinterpreting the link adaptation control subfield included in the existing HT control field.
  • VHT control field format illustrates an example of a VHT control field format that can be applied to an embodiment of the present invention.
  • the format of the VHT control field is the same as the format of the HT control field, which means that the format of the VHT control field can be distinguished from the format of the HT control field only by how to interpret the bit string assigned to each field.
  • the field format shown in FIG. 11 is a VHT control field format when the reserved bit is used as a HT / VHT indicator subfield and indicates that the HT / VHT indicator subfield is a VHT control field. In this case, the HT control field format may be interpreted.
  • the VHT control field 1100 includes a link adaptation control subfield 1110.
  • the link adaptation subfield includes a TRQ subfield 1111, an MAI subfield 1112, an MFSI subfield 1113 and an MFB / ASELC subfield 1114. Since this is the same as the HT control field 500 shown in FIG. 5, a detailed description thereof will be omitted.
  • the existing link adaptation control subfields include 1-bit reserved bits, 1-bit TRQ subfield 1111, 4-bit MAI subfield 1112, 3-bit MFSI subfield 1113 and 7-bit MFB. / ASELC subfield 1114. Therefore, a specific bit section of the 14 bits arranged after the TRQ subfield 1111 may be used as a bit string for providing STA identification information. For example, when the STA identification information is used as the AID, the required bit size for allocating the AID among the 14 bits may be allocated as the subfield for the AID.
  • the STA transfers the bit string following the bit string corresponding to the TRQ subfield 1210 to MAI, MFS, and MFB / ASELC. Will be interpreted.
  • the STA interprets the bit string following the bit string corresponding to the TRQ subfield as STA identification information and whether to transmit a sounding PPDU. The decision is made.
  • the wireless device 1200 may be an AP or an STA.
  • the wireless device 1200 includes a processor 1210, a memory 1220, and a transceiver 1230.
  • the transceiver 1230 transmits and / or receives a radio signal, but the physical layer of IEEE 802.11 is implemented.
  • the processor 1210 is functionally connected to the transceiver 1230, and implements the MAC layer and / or the embodiment of the present invention shown in Figs. 7 to 11 relating to a method for obtaining channel information through TRQ-sounding PPDU transmission and reception. It is configured to implement the PHY layer.
  • Processor 1210 and / or transceiver 1230 may include application-specific integrated circuits (ASICs), other chipsets, logic circuits, and / or data processing devices.
  • ASICs application-specific integrated circuits
  • the above-described technique may be implemented as a module (process, function, etc.) for performing the above-described function.
  • the module may be stored in the memory 1220 and executed by the processor 1210.
  • the memory 1220 may be included in the processor 1210, and may be functionally connected to the processor 1210 through various known means that are separately located outside the processor 1210.

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  • Radio Transmission System (AREA)

Abstract

L'invention concerne un procédé de communication utilisant un point d'accès (AP) dans un système de réseau local sans fil. Ce procédé comprend les étapes consistant à demander la transmission d'une unité de données de protocole (PPDU) d'une PLCP (procédure de convergence de couche physique) de sondage pour estimer un canal jusqu'à une première station (STA) et à une seconde station (STA), à recevoir un premier PPDU de sondage de la première STA, et à recevoir un second PPDU de sondage de la seconde STA. Le processus de demande de la transmission de la PPDU de sondage comprend l'étape de transmission d'une trame agrégée à la première STA et à la seconde STA, dans cette étape une première trame de demande destinée à demander la transmission de la PPDU de sondage à la première STA est agrégée à une seconde trame de demande destinée à demander la transmission de la PPDU de sondage à la seconde STA.
PCT/KR2011/001850 2010-03-18 2011-03-17 Procédé et appareil pour une communication dans un système de réseau local sans fil Ceased WO2011115431A2 (fr)

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KR101603116B1 (ko) * 2012-04-13 2016-03-25 엘지전자 주식회사 무선랜 시스템에서 비콘 프레임의 선택적 디코딩을 위한 방법 및 장치
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WO2015060514A1 (fr) * 2013-10-22 2015-04-30 엘지전자 주식회사 Procédé et dispositif d'empêchement de brouillage dans une zone de service en chevauchement
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US20170135087A1 (en) * 2014-07-01 2017-05-11 Wilus Institute Of Standards And Technology Inc. Wireless communication method and wireless communication terminal
US12382458B2 (en) 2014-07-01 2025-08-05 Wilus Institute Of Standards And Technology Inc. Simultaneous data transmission between an access point and a plurality of stations
US10085243B2 (en) 2014-07-01 2018-09-25 Wilus Institute Of Standards And Technology Inc. Wireless communication method and wireless communication terminal
US11844072B2 (en) 2014-07-01 2023-12-12 Wilus Institute Of Standards And Technology Inc. Simultaneous data transmission between an access point and a plurality of stations
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KR102117635B1 (ko) 2014-07-01 2020-06-02 주식회사 윌러스표준기술연구소 무선 통신 방법 및 무선 통신 단말
US10708890B2 (en) 2014-07-01 2020-07-07 Wilus Institute Of Standards And Technology Inc. Simultaneous data transmission between an access point and a plurality of stations
US10893511B2 (en) 2014-07-01 2021-01-12 Wilus Institute Of Standards And Technology Inc. Simultaneous data transmission between an access point and a plurality of stations
KR102309050B1 (ko) 2014-07-01 2021-10-06 주식회사 윌러스표준기술연구소 무선 통신 방법 및 무선 통신 단말
WO2016003195A1 (fr) * 2014-07-01 2016-01-07 주식회사 윌러스표준기술연구소 Procédé de communication sans fil et terminal de communication sans fil
US11350390B2 (en) 2014-07-01 2022-05-31 Wilus Institute Of Standards And Technology Inc. Simultaneous data transmission between an access point and a plurality of stations
KR20170030491A (ko) * 2014-07-01 2017-03-17 주식회사 윌러스표준기술연구소 무선 통신 방법 및 무선 통신 단말
US10251085B2 (en) 2015-01-08 2019-04-02 Lg Electronics Inc. Method and device for transmitting frame including error check bits for header in wireless LAN
WO2016111435A1 (fr) * 2015-01-08 2016-07-14 엘지전자 주식회사 Procédé et dispositif permettant de transmettre une trame contenant des bits de contrôle d'erreurs pour un en-tête dans un réseau lan sans fil
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