Access point, terminal, and communication method

Abstract

This access point comprises: a transmission circuit that transmits, to a terminal, information pertaining to a pattern of a stream associated with an uplink signal from the terminal; and a reception circuit that receives a signal precoded on the basis of the pattern.

Description

Access point, terminal, and communication method

[0001] The present disclosure relates to an access point, a terminal, and a communication method.

[0002] The Institute of Electrical and Electronics Engineers (IEEE) is currently working on the IEEE 802.11bn (hereinafter referred to as "11bn") standard for next-generation wireless local area networks (WLANs) as a successor to the IEEE 802.11be (hereinafter referred to as "11be") standard in a study group (SG). 11be is also known as "Extreme High Throughput (EHT) WLAN" or simply "EHT," and 11bn is also known as "Ultra High Reliability (UHR) WLAN" or simply "UHR." Specifications used in WLANs (also known as wireless LANs) include IEEE 802.11 and its amendments (IEEE 802.11ax, IEEE 802.11be, and other future standards), IEEE 802.15, etc.

[0003] IEEE 802.11-22 / 1392r0, “Beamforming Improvement for UHR”IEEE 802.11-23 / 0725r0, “Uplink MU MIMO Precoding - Follow-up”IEEE P802.11be / D4.0IEEE 802.11-2020IEEE 802.11-14 / 0571r12, “11ax Evaluation Methodology”Daisuke Ogawa, et al., “A Low Complexity PMI / RI Selection Scheme in LTE-A systems,”VTC Spring 2013, IEEEIEEE 802.11-19 / 1593r3, “Joint Sounding for Multi-AP Systems”IEEE 802.11-19 / 0804r0, “Multi-AP Transmission Procedure”

[0004] However, the method for controlling signal transmission in wireless communication such as wireless LAN has not been fully studied.

[0005] Non-limiting embodiments of the present disclosure contribute to providing an access point, a terminal, and a communication method that can improve the efficiency of transmission control in wireless communication.

[0006] An access point according to one embodiment of the present disclosure includes a transmitting circuit that transmits to a terminal information regarding a pattern of a stream associated with an uplink signal from the terminal, and a receiving circuit that receives a precoded signal based on the pattern.

[0007] These comprehensive or specific aspects may be realized as a system, an apparatus, a method, an integrated circuit, a computer program, or a recording medium, or may be realized as any combination of a system, an apparatus, a method, an integrated circuit, a computer program, and a recording medium.

[0008] According to an embodiment of the present disclosure, for example, it is possible to improve the efficiency of transmission control in wireless communication.

[0009] Further advantages and benefits of one embodiment of the present disclosure will become apparent from the specification and drawings. Such advantages and / or benefits may be provided by some embodiments and features described in the specification and drawings, respectively, but not necessarily all of them may be provided to obtain one or more identical features.

[0010] Figure showing an example sequence of uplink (UL) precodingBlock diagram showing an example configuration of a part of an access point (AP)Block diagram showing an example configuration of a part of a terminal (STA: Station)Block diagram showing an example configuration of an APBlock diagram showing an example configuration of an STAFigure showing an example sequence of operation of an AP and an STAFigure showing an example of the correspondence between P-matrix and stream numberFigure showing an example of stream number in time multiplexing and frequency multiplexingFigure showing an example of stream number patternFigure showing an example of stream number patternFigure showing an example of stream number patternFigure showing an example of stream number patternFigure showing an example of stream number patternFigure showing an example of Common Info field of a Trigger frameFigure showing an example of User Info field of a Trigger frameFigure showing an example of Stream Number Pattern subfieldFigure showing an example sequence of operation of an AP and an STAFigure showing an example sequence of operation of an AP and an STAFigure showing an example of operation sequence of an AP and an STAFigure showing an example of STA Info field of a Null data packet Announcement (NDPA)Figure showing an example of Generate Precoder subfieldFigure showing an example of stream number notification in NDPAFigure showing an example of the number of streams assigned to a STA and its effectFigure showing an example of Trigger type of a Trigger frameFigure showing an example of Common Info field of a Trigger frameUser Info field of a Trigger frame Diagram showing an example of the Info field Diagram showing an example of the Number Of HE / EHT-LTF Symbols subfield Diagram showing an example of the sequence of operations of the AP and STA Diagram showing an example of the sequence of operations of the AP and STA Diagram showing an example of an orthogonal resource and its effect Diagram showing an example of the Precoder Type subfield Block diagram showing an example of the configuration of an AP Diagram showing an example of the sequence of operations of the AP and STA Diagram showing an example of the Trigger type of the Trigger frame Diagram showing an example of the format of the Trigger frame Common Info of the Trigger frameFigure showing an example of the User Info field in the Trigger frameFigure showing an example of the Precoder Calculation Indication subfieldFigure showing an example of the Multi-AP (MAP) NDPA formatFigure showing an example of the User Info field in the Trigger frameFigure showing an example of the Joint Sounding subfieldFigure showing an example of the Trigger type in the Trigger frameFigure showing an example of the Common Info field in the Trigger frameFigure showing an example of the User Info field in the Trigger frame

[0011] Hereinafter, each embodiment of the present disclosure will be described in detail with reference to the drawings.

[0012] One of the focuses of UHR is improving throughput at different reception qualities (e.g., signal-to-noise ratio (SNR) levels). To achieve this goal, for example, uplink (UL) beamforming (BF) is expected to be applied (see, for example, Non-Patent Document 1).

[0013] Regarding the Precoder used for BF, a method has been proposed in which an access point (AP, also referred to as a "base station") performs channel quality estimation (sounding) and UL precoder calculation based on an uplink signal (e.g., Null Data Packet (NDP)) from a terminal (STA, also referred to as a "non-AP STA"), and notifies each STA of the UL precoder (see, for example, Non-Patent Document 2). Note that the Precoder is used to perform linear operations on modulated signals, and is also referred to as, for example, a precoding matrix, beamforming matrix, or steering matrix. In Non-Patent Document 2, for UL MU-MIMO (UL Multi User - Multi Input Multi Output) Precoding, in the sequence shown in FIG. 1, the AP (Beamformee) calculates a Precoder based on an uplink signal (e.g., UL sounding NDP) from the STA (Beamformer), and notifies each STA of the Precoder coefficients.

[0014] However, the control method for UL precoding has not been fully investigated.

[0015] For example, in the method of Non-Patent Document 2, there is a concern that overhead (signaling overhead) increases when the AP notifies each STA of a Precoder.

[0016] In contrast, implicit feedback is specified as an example of a precoding control method with low overhead (see, for example, "10.34.1 HT steering matrix calculations" in Non-Patent Document 4). In this method, channel quality estimation and precoder calculation are performed based on reciprocity between uplink and downlink (DL). If reciprocity between uplink and downlink does not hold, there is concern about degradation of BF performance and reception quality. For example, conditions for not holding reciprocity between uplink and downlink include the influence of interference signals and frequency and phase errors between the transmitter (Tx) and receiver (Rx) due to insufficient calibration frequency.

[0017] In a non-limiting embodiment of the present disclosure, an example of a precoding control method that suppresses an increase in overhead and also suppresses deterioration of reception quality when reversibility between uplink and downlink is not established will be described.

[0018] [Configuration of Wireless Communication System] The wireless communication system according to this embodiment may include, for example, an AP 100 and an STA 200. In the wireless communication system, there may be, for example, two or more APs 100 and two or more STAs 200.

[0019] 2 is a block diagram illustrating a configuration example of a portion of an AP 100 according to an embodiment of the present disclosure. In the AP 100 illustrated in FIG. 2, a transmitter (e.g., corresponding to a transmitter circuit) transmits information regarding a stream pattern (e.g., also referred to as a stream number pattern) associated with an uplink signal from the STA 200 to the STA 200. A receiver (e.g., a receiver circuit) receives a signal (e.g., UL data) precoded based on the pattern.

[0020] 3 is a block diagram illustrating a configuration example of a portion of a STA 200 according to an embodiment of the present disclosure. In the STA 200 illustrated in FIG. 3, a receiving unit (e.g., corresponding to a receiving circuit) receives information regarding a pattern of a stream associated with an uplink signal from the STA 200. A transmitting unit (e.g., corresponding to a transmitting circuit) transmits a precoded signal based on the pattern.

[0021] (Embodiment 1) In this embodiment, AP 100 performs UL precoding control by notifying STA 200 of a control signal including information regarding a pattern of streams (e.g., stream numbers) associated with UL signals from STA 200 (hereinafter referred to as "stream number pattern").

[0022] The stream number pattern indicates, for example, one or a combination of numbers assigned to (associated with) each of a plurality of streams that constitute (or are applied to) the UL signal. The stream numbers are determined, for example, based on the UL signal from the STA 200.

[0023] The stream number pattern may include, for example, at least one of multiple streams applied to the UL signal. For example, the stream number pattern may include consecutive or non-consecutive stream numbers among the numbers (stream numbers) assigned to multiple streams applied to the UL signal. The stream may be, for example, a spatial stream or a space-time stream. Hereinafter, if space-time block coding (STBC) is not implemented, it is assumed that the space-time stream is equal to the spatial stream.

[0024] Furthermore, the UL signal may be, for example, a UL signal received by the AP 100 from the STA 200 (for example, the most recently received UL signal). The UL signal may include, for example, an NDP to which a precoder is applied, or a signal including data to which a precoder is applied. Furthermore, "most recently" refers to, for example, the time when the AP 100 most recently received a UL signal from the STA 200 before transmitting a control signal.

[0025] The control signal may also include, for example, control information for a Precoder applied to the UL signal, and may also include, for example, information regarding a stream number pattern.

[0026] An example of the configuration of the AP 100 and the STA 200 according to this embodiment will be described below.

[0027] [Configuration Example of AP 100] FIG. 4 is a block diagram showing a configuration example of the AP 100.

[0028] The AP 100 shown in FIG. 4 may include, for example, a radio transmission / reception unit 101, a separation unit 102, an orthogonal separation unit 103, a preamble demodulation unit 104, a channel estimation unit 105, a quality estimation unit 106, a precoder selection unit 107, a data demodulation unit 108, a data decoding unit 109, a stream number pattern holding unit 110, a preamble generation unit 111, a data generation unit 112, and a multiplexing unit 113.

[0029] 4 may be included in the transmitting section shown in FIG. 2, and the wireless transmitting / receiving section 101 shown in FIG. 4 may be included in the receiving section shown in FIG.

[0030] 4 , the radio transmission / reception unit 101 performs transmission and reception processing of radio signals for the STA 200. For example, in the transmission processing, the radio transmission / reception unit 101 performs D / A (Digital-to-Analog) conversion and up-conversion to a carrier frequency on the radio frame output from the multiplexing unit 113, and transmits the signal after the transmission processing to the STA 200 via an antenna. Also, in the reception processing, for example, the radio transmission / reception unit 101 receives a signal transmitted from the STA 200 via an antenna, performs down-conversion and A / D (Analog-to-Digital) conversion, and outputs the signal after the reception processing to the demultiplexing unit 102.

[0031] The separation unit 102 separates (or divides) the signal received from STA200 and output from the radio transmission / reception unit 101 into a preamble section (or preamble signal) and a data section (or data signal), outputs the preamble signal to the orthogonal separation unit 103, and outputs the data signal to the data demodulation unit 108.

[0032] The orthogonal separation unit 103 performs a Fourier transform (e.g., Fast Fourier Transform (FFT)) on the preamble signal output from the separation unit 102, and extracts control information (e.g., orthogonal resources, etc.) to be used in the STA 200 (e.g., the orthogonalization unit 215 described later). Then, the orthogonal separation unit 103 separates the reference signal (e.g., a training signal such as a Long Training Field (LTF) or a Short Training Field (STF)) in the preamble signal based on the extracted control information. Here, the reference signal is separated into dimensions corresponding to, for example, the number of receiving antennas and the number of streams. The orthogonal separation unit 103 outputs the separated preamble to the preamble demodulation unit 104.

[0033] Preamble demodulation section 104 demodulates the preamble signal output from orthogonal separation section 103, extracts control information (e.g., frequency bandwidth (BW)) or MCS (Modulation and Coding Scheme)) used for demodulating and decoding the data signal, and outputs this to data demodulation section 108. Preamble demodulation section 104 also extracts a reference signal included in the preamble signal, and outputs the reference signal to channel estimation section 105.

[0034] The channel estimation unit 105 estimates the UL channel from the STA 200 to the AP 100 based on the output of the preamble demodulation unit 104. The channel estimation unit 105 performs channel estimation, for example, for each received stream and each received antenna. The channel estimation unit 105 outputs the derived channel estimation value to the quality estimation unit 106 and the data demodulation unit 108.

[0035] The quality estimation unit 106 estimates the reception quality (e.g., SNR or SINR (Signal-to-Interference-plus-Noise ratio)) of the signal received by the AP 100 for each stream and for each receiving antenna, based on the channel estimation value output from the channel estimation unit 105. As an example, when estimating the SINR, the quality estimation unit 106 may estimate each SINR for each receiving stream and for each receiving antenna using the calculation formula described in Non-Patent Document 5. The quality estimation unit 106 outputs the derived estimated value of the reception quality to the precoder selection unit 107.

[0036] The precoder selection unit 107 generates control information to be transmitted by the AP 100 to the STA 200 based on the estimated value of reception quality output from the quality estimation unit 106. For example, the precoder selection unit 107 may select a precoder (e.g., a stream number pattern) to be used for transmission by the STA 200 based on the estimated value of reception quality. As an example, the precoder selection unit 107 may perform rank adaptation of the transmission rank of the STA 200 based on the SINR output from the quality estimation unit 106. For example, rank adaptation may be a procedure for determining spatial streams and / or the number of spatial streams that result in good throughput and / or communication quality (see, for example, Non-Patent Document 6). For example, the precoder selection unit 107 determines a combination of stream numbers (stream number pattern) to be used for UL transmission in the STA 200 through rank adaptation, and outputs the determined stream number pattern to the stream number pattern storage unit 110.

[0037] Data demodulation section 108 performs an FFT on the Data signal output from demultiplexing section 102, and performs demodulation processing based on the control information output from preamble demodulation section 104 and the UL channel estimation value output from channel estimation section 105. Data demodulation section 108 outputs the demodulated Data signal obtained by demodulation to Data decoding section 109. Data demodulation section 108 may also output the control information output from preamble demodulation section 104 to Data decoding section 109.

[0038] The data decoding unit 109 decodes the demodulated data signal output from the data demodulation unit 108 based on the output (control information) of the preamble demodulation unit 104. When the UL signal is a TB (Trigger Based) PPDU (Physical Layer (PHY) Protocol Data Unit), the data decoding unit 109 may hold control information (e.g., MCS or coding type) included in a trigger frame (a signal instructing the STA 200 to transmit a TB PPDU) transmitted by the AP 100, and perform decoding based on the control information.

[0039] The stream number pattern storage unit 110 stores in a storage area (e.g., a buffer) the stream number pattern output from the precoder selection unit 107. For example, the stream number pattern storage unit 110 may output the stream number pattern to the data generation unit 112 when generating a control signal so that the AP 100 can notify the STA 200 of the stream number pattern.

[0040] The preamble generation unit 111 generates a preamble signal (for example, EHT-SIG, EHT-LTF, U-SIG, etc.) to be included in a control signal transmitted from the AP 100 to the STA 200. The preamble generation unit 111 outputs the generated preamble signal to the multiplexing unit.

[0041] The data generation unit 112 generates a data signal (for example, an NDPA (NDP Announcement) frame or a trigger frame). The data signal may include, for example, a stream number pattern output from the stream number pattern storage unit 110. Here, when generating a trigger frame that instructs the STA 200 to transmit a TB PPDU, the AP 100 stores control information of the data signal in the TB PPDU (for example, MCS or coding type, etc.) in a memory area. The data generation unit 112 outputs the generated data signal to the multiplexing unit 113.

[0042] The multiplexing unit 113 performs modulation and inverse Fourier transform (e.g., Inverse Fast Fourier Transform (IFFT)) processing on the preamble signal output from the preamble generation unit 111 and the data signal output from the data generation unit 112, multiplexes them in accordance with the format of the radio frame, and outputs the result as a radio frame to the radio transmitting and receiving unit 101. Here, the reference signal included in the preamble signal may be orthogonalized by allocating predetermined orthogonal resources.

[0043] [Configuration Example of STA 200] FIG. 5 is a block diagram showing a configuration example of the STA 200. As shown in FIG.

[0044] The STA 200 shown in Figure 5 may include, for example, a radio transmission / reception unit 201, a separation unit 202, a preamble demodulation unit 203, a channel estimation unit 204, a data demodulation unit 205, a data decoding unit 206, a precoder generation unit 207, a stream number pattern holding unit 208, a precoder holding unit 209, a reference signal generation unit 210, a data generation unit 211, a control signal generation unit 212, a precoding matrix multiplication unit 213, a modulation unit 214, an orthogonalization unit 215, and a multiplexing unit 216.

[0045] 5 may be included in the receiving section shown in FIG. 3, and the wireless transmitting / receiving section 201 shown in FIG. 5 may be included in the transmitting section shown in FIG.

[0046] 5 , the wireless transceiver unit 201 performs transmission and reception processing of wireless signals for the AP 100. For example, in the transmission processing, the wireless transceiver unit 201 performs D / A conversion and up-conversion to a carrier frequency on the wireless frame output from the multiplexer 216, and transmits the signal after the transmission processing to the AP 100 via an antenna. Also, in the reception processing, for example, the wireless transceiver unit 201 receives a signal transmitted from the AP 100 via an antenna, performs down-conversion and A / D conversion, and outputs the signal after the reception processing to the separator 202.

[0047] The separation unit 202 separates (or divides) the signal received from AP 100 and output from the wireless transmission / reception unit 201 into a preamble section (or preamble signal) and a data section (or data signal), outputs the preamble signal to the preamble demodulation unit 203, and outputs the data signal to the data demodulation unit.

[0048] Preamble demodulation section 203 performs a Fourier transform (FFT) on the preamble signal output from separation section 202, extracts control information (for example, BW or MCS) used for demodulating and decoding the data signal, and outputs this to data demodulation section 205. Preamble demodulation section 203 also extracts a reference signal (for example, LTF or STF) included in the preamble signal and outputs this to channel estimation section 204.

[0049] The channel estimation unit 204 estimates channel quality based on the output of the preamble demodulation unit 203. The channel estimation value derived in the channel estimation unit 204 is a DL channel estimation value from the AP 100 to the STA 200. For example, the channel estimation unit 204 outputs the DL channel estimation value to the Data demodulation unit 205 in order to demodulate the Data signal. Here, the STA 200 may derive a UL channel estimation value (e.g., a channel from the STA 200 to the AP 100) from the DL channel estimation value, assuming, for example, that there is (establishes) channel reversibility between the UL and DL. The channel estimation unit 204 outputs the derived UL channel estimation value to the Precoder generation unit 207.

[0050] Data demodulation section 205 performs an FFT on the Data signal output from demultiplexing section 202, and performs demodulation processing based on the control information output from preamble demodulation section 203 and the DL channel estimation value output from channel estimation section 204. Data demodulation section 205 outputs the demodulated Data signal obtained by demodulation to Data decoding section 206. Data demodulation section 205 may also output the control information output from preamble demodulation section 203 to Data decoding section 206.

[0051] The data decoding unit 206 decodes the demodulated data signal output from the data demodulation unit 205 based on the output (control information) of the preamble demodulation unit 203. If the received data obtained by decoding contains a stream number pattern, the data decoding unit 206 outputs the data to a stream number pattern holding unit 208. Furthermore, if the received data contains precoder control information from the AP 100 (e.g., precoder generation type, number of transmission streams, orthogonal resource information used for the transmission stream (e.g., orthogonal code, frequency, time, etc.)), the data decoding unit 206 outputs the precoder control information to the precoder generation unit 207.

[0052] The precoder generation unit 207 generates a precoder (precoding matrix) based on the UL channel estimation value output from the channel estimation unit 204 and the control information output from the data decoding unit 206. The precoder generation unit 207 outputs information about the generated precoder to be applied to the reference signal and data signal transmitted by the STA 200. For example, the precoder generation unit 207 outputs the generated precoder to a precoder holding unit so that the STA 200 can select a precoder based on the control information (stream number pattern) from the AP 100. The precoder generation unit 207 also determines a stream number associated with each stream applied to the UL transmission of the STA 200 and outputs the determined stream number to the stream number pattern holding unit 208.

[0053] The stream number pattern holding unit 208 stores in a storage area (buffer) the stream numbers output from the precoder generation unit 207. Furthermore, when a stream number pattern is output from the data decoding unit, the stream number pattern holding unit 208 extracts the stream number specified by the stream number pattern from the stored stream numbers, and outputs the extracted stream number to the precoder holding unit 209.

[0054] The precoder holding unit 209 saves the precoder output from the precoder generation unit 207 in a storage area. The precoder holding unit 209 also extracts components from a precoding matrix based on the stream number (specified stream number) output from the stream number pattern holding unit 208, and outputs the components to, for example, a precoding matrix multiplication unit 213 (not shown). Here, selecting and extracting components from a precoding matrix to obtain a reconstructed precoding matrix is ​​called precoder reconstruction or precoder selection.

[0055] The reference signal generating unit 210 generates a reference signal (e.g., LTF, STF, etc.) to be included in the preamble signal of the UL signal. It is assumed that the reference signal generated by the reference signal generating unit 210 will undergo application of a precoder and orthogonalization in later processing. For example, the reference signal generating unit 210 may generate a reference signal based on the number of streams determined by the precoder generating unit 207 and control information acquired by the data decoding unit 206 (e.g., the number of streams or frequency specified by the AP 100). Furthermore, the reference signal generating unit 210 may determine the number of streams of the reference signal according to the number of stream numbers output from the precoder holding unit 209 (the number of stream numbers specified by the AP 100 using a stream number pattern) or the number of columns of the precoding matrix to be reconstructed. The reference signal generating unit 210 outputs the generated reference signal to the precoding matrix multiplying unit 213.

[0056] The data generation unit 211 generates a data signal (for example, an MPDU (MAC Protocol Data Unit)) to be included in the UL signal. The signal generated in the data generation unit 211 assumes that a precoder will be applied in later processing, and unlike reference signals, does not assume that orthogonalization will be applied. Furthermore, the data generation unit 211 may determine the number of streams of the data signal according to the number of stream numbers output from the precoder holding unit 209 (the number of stream numbers indicated by the stream number pattern from the AP 100) or the number of columns of the precoding matrix to be reconstructed. The data generation unit 211 outputs the generated data signal to the precoding matrix multiplication unit 213.

[0057] The control signal generating unit 212 generates a control signal to be included in the preamble signal of the UL signal (for example, a preamble signal excluding reference signals such as EHT-SIG and U-SIG). Unlike the reference signal and the data signal, the signal generated in the control signal generating unit 212 does not assume the application of a precoder or orthogonalization in subsequent processing. The control signal generating unit 212 outputs the generated control signal to the modulating unit 214.

[0058] The precoding matrix multiplication unit 213 multiplies the signals output from the reference signal generation unit 210 and the data generation unit 211 by the precoding matrix output from the precoder holding unit 209. Here, different precoding matrix elements are multiplied for each stream and each transmit antenna. The precoding matrix multiplication unit 213 outputs the signal after precoding matrix multiplication (precoded signal) to the modulation unit 214.

[0059] The modulation unit 214 performs modulation and inverse Fourier transform (IFFT) on the precoded signal output from the precoding matrix multiplication unit 213 and the control signal output from the control signal generation unit 212, and outputs the modulated signal to the multiplexing unit 216. When the precoded signal is a reference signal, the modulation unit 214 outputs the modulated signal (modulated reference signal) to the orthogonalization unit 215.

[0060] The orthogonalization unit 215 orthogonalizes the modulated reference signals output from the modulation unit 214 using orthogonal resources. For example, when orthogonal codes (e.g., P-matrix) are used as resources, the orthogonalization unit 215 multiplies each stream of the modulated reference signals by a different orthogonal code so that the streams are mapped to each transmitting antenna. The orthogonalization unit 215 outputs the orthogonalized modulated reference signals to the multiplexing unit 216.

[0061] The multiplexing unit 216 multiplexes the orthogonalized modulated reference signal and the modulated signal (the data signal and the signal obtained by multiplying the control signal by a precoding matrix and modulating it) according to the format of the radio frame, and outputs the multiplexed signal to the radio transmitting / receiving unit 201 as a radio frame.

[0062] The above describes exemplary configurations of the AP 100 and the STA 200.

[0063] [Example of Operation of AP 100 and STA 200] An example of operation of the AP 100 and STA 200 will be described below.

[0064] [Method 1] FIG. 6 is a sequence diagram showing an example of the operation of the AP 100 (simply referred to as AP) and the STA 200 (simply referred to as STA) in Method 1.

[0065] <Transmission of UL Signal to which Precoder is Applied> In FIG. 6, STA 200 transmits a UL signal to which Precoder is applied (for example, a UL signal to which multiple streams are applied).

[0066] The UL signal may be, for example, a TB PPDU (e.g., a Data signal) in which a reference signal and Data are multiplied by a Precoding matrix, or an NDP in which only a reference signal is multiplied by a Precoding matrix without generating Data. An NDP multiplied by a Precoding matrix may also be called a Precoded NDP, a Beamformed NDP, or a Steered NDP.

[0067] The STA 200 (for example, the precoding matrix multiplication unit 213) multiplies, for example, the reference signal and the data signal by a precoding matrix. The precoding matrix corresponds to a Q-matrix, and in the case of STF, for example, the variable Q in equation (36-35) or equation (36-46) described in Non-Patent Document 3 is k,u In the case of LTF, the variable Q in equation (36-44) or equation (36-45) described in Non-Patent Document 3 k and Q k,u , In the case of the Data signal, the variable Q in equation (36-87) or equation (90) described in Non-Patent Document 3 k,u is multiplied as

[0068] The STA 200 (for example, the orthogonalization unit 215) performs orthogonalization on the reference signals. As an example, orthogonalization using an orthogonal code (P-matrix) will be described.

[0069] The stream number of each stream constituting the UL signal may correspond to, for example, each row of the P-matrix included in the reference signal. The AP 100 identifies (or grasps) the stream number of each stream constituting the UL signal by orthogonally separating the streams corresponding to each row of the P-matrix. For example, the stream number is determined based on the uplink signal of the STA 200. For example, when the UL signal uses three streams (in the case of 3-stream transmission), the P-matrix (P EHT-LTF ) is used (for example, equations (36-43) in Non-Patent Document 3).

[0070] In the case of 3-stream transmission, for example, the four values ​​in each of the first to third rows of the P-matrix are multiplied by the four LTF symbols of each stream, as shown in Fig. 7. For example, the streams corresponding to the first, second, and third rows of this P-matrix may be set to Stream 1, Stream 2, and Stream 3, respectively, which make up the UL signal (e.g., LTF), and the stream number of each stream may be associated with the first, second, and third rows of the P-matrix.

[0071] It is assumed that the number of streams constituting the UL signal is determined by the AP 100 based on the capability of the STA 200, and that the AP and the STAs agree on the number of streams of the UL signal.

[0072] <Receiving UL signal and obtaining stream number> After receiving the UL signal, AP 100 (e.g., orthogonal separation unit 103) refers to the NSS subfield from the control signal (e.g., EHT-SIG) and obtains the number of streams of the UL signal and the stream number associated with the P-matrix.

[0073] AP 100 performs orthogonal separation of the reference signals based on the acquired control information.

[0074] The AP 100 (e.g., preamble demodulation unit 104) demodulates the preamble signal of each orthogonally separated stream. Here, when the UL signal is a signal containing data (e.g., TB PPDU) and code multiplexing is applied, the AP 100 acquires a stream number associated with the P-matrix, as in the case of NDP. On the other hand, the stream number when the UL signal is a signal containing data (e.g., TB PPDU) and a multiplexing method other than code multiplexing (e.g., time multiplexing or frequency multiplexing) is applied will be described with reference to FIG. 8 .

[0075] In the case of time multiplexing in Fig. 8, the STA 200 and the AP 100 recognize the streams of packets transmitted consecutively in time as different stream numbers, and store these in recording areas (e.g., stream number pattern storage units 110 and 208). For example, as shown in Fig. 8, when three packets are transmitted from the STA 200 using one stream each, the streams of packets 1, 2, and 3 are set to streams 1, 2, and 3, respectively. In this case, the same P-matrix may be used between streams 1, 2, and 3.

[0076] Also, for example, if three packets are each transmitted using two streams, the streams of Packet 1 may be set to Streams 1 and 2, the streams of Packet 2 may be set to Streams 3 and 4, and the streams of Packet 3 may be set to Streams 5 and 6. Here, the stream numbers within the same packet (for example, Stream 1 and Stream 2 within Packet 1) may be recognized by the difference in the rows of the P-matrix described above.

[0077] In addition, in FIG. 8, an example has been described in which packets are transmitted with a gap section (non-transmission section) of a predetermined time provided, but this is not limiting, and packets of a predetermined length may be transmitted continuously without a gap section.

[0078] In the case of frequency multiplexing in FIG. 8, the STA 200 and the AP 100 recognize the streams of signals transmitted in different frequency bands (or frequency resources) as different stream numbers and store them in a recording area (for example, the stream number pattern storage units 110 and 208).

[0079] The frequency band may be, for example, a resource in units of a Resource Unit (RU) or a Tone. Also, for example, a plurality of Tones spaced apart by a predetermined Tone interval may be grouped together to form one Stream.

[0080] 8, when the frequencies are RU1<RU2<RU3 and one stream is transmitted from STA 200 in each RU, the stream number for RU1 may be set to Stream 1, the stream for RU2 may be set to Stream 2, and the stream for RU3 may be set to Stream 3. Also, for example, when the frequencies are RU1>RU2>RU3, the stream numbers for the streams in RU1, 2, and 3 may be set to Stream 1, 2, and 3.

[0081] Also, for example, in the example of frequencies where RU1<RU2<RU3, if two streams are transmitted in each RU, the streams in RU1 may be set to Streams 1 and 2, the streams in RU2 may be set to Streams 3 and 4, and the streams in RU3 may be set to Streams 5 and 6. Here, the stream numbers within the same RU (for example, Stream 1 and Stream 2 in RU1) may be recognized by the difference in the rows of the P-matrix described above, as in time multiplexing.

[0082] The AP 100 (e.g., the channel estimation unit 105) estimates the UL channel between the AP and the STA for each stream and each receiving antenna based on the orthogonally separated reference signal (e.g., the LTF). The AP 100 (e.g., the quality estimation unit 106) also estimates the reception quality for each stream and each receiving antenna using the estimated UL channel. As an example, the AP 100 may calculate the SINR for each stream and each receiving antenna using the formula described in Non-Patent Document 5 in estimating the reception quality.

[0083] <Determining Stream Number Pattern> The AP 100 (e.g., the Precoder selection unit 107) determines a stream number pattern using the calculated reception quality (e.g., SINR). The stream number pattern may include, for example, at least one of the multiple streams that make up the UL signal. For example, the stream number pattern may include consecutive or non-consecutive stream numbers from among the stream numbers of the multiple streams that make up the UL signal. For example, a rank adaptation method may be applied to determine the stream number pattern.

[0084] As an example, we will explain the case where STA200 transmits a UL signal using three streams, and AP100 selects Streams 1 and 3 as the combination of stream numbers (stream number pattern) with the highest capacity using rank adaptation aimed at maximizing capacity (communication capacity).

[0085] In this case, the AP 100 (stream number pattern storage unit 110) stores stream numbers 1 and 3 obtained by rank adaptation in a storage area, and outputs a stream number pattern including stream numbers 1 and 3 to the preamble generation unit 111 and the data generation unit 112.

[0086] The AP 100 (for example, the Data generation unit 112) notifies the STA 200 of the determined Stream number pattern and generates a control signal (for example, a Trigger frame) for causing the STA 200 to transmit UL data.

[0087] An example of a method for notifying a stream number pattern using a control signal will be described below.

[0088] (1) Method using a bitmap: The AP 100 uses multiple bits in the control signal to indicate whether each of multiple streams is in use or not, depending on the value of each bit (0 or 1). For example, if the STA 200 transmits an UL signal using four streams (Streams 1 to 4) and the AP 100 determines the stream number pattern to be Streams 1, 3, and 4, the bitmap is set to "1011." Here, each bit indicates whether Streams 1 to 4 are in use or not, from left to right, with 1 indicating "in use" and 0 indicating "not in use." When the STA 200 receives the bitmap "1011," it uses three streams, Streams 1, 3, and 4, when transmitting the next UL data. Note that if the UL signal uses six streams, a 6-bit bitmap may be used, or the number of bits in the bitmap may be variably set according to the number of streams.

[0089] (2) Method of using a common table between AP 100 and STA 200: A common table (common table) is defined in advance between AP 100 and STA 200, and AP 100 notifies STA 200 of the values ​​corresponding to the common table using a control signal. As an example, Figure 9 shows an example of a common table using 3 bits when the UL signal uses four streams. In the example of Figure 9, 8 different stream number patterns can be notified using 3 bits (values ​​0 to 7).

[0090] Furthermore, for example, if four bits are used in the common table (not shown), the AP 100 and the STA 200 can cover all stream number patterns for transmitting and receiving UL signals using four streams (the same as the method using a bitmap in (1)). For example, if the table is defined using a number of bits fewer than the number of streams, the amount of signaling can be reduced by partially modifying (or omitting) the contents of the stream number pattern, as shown in Figure 9. For example, in the example of Figure 9, the pattern for the number of streams 1 is limited to only Stream 1, and cases for other streams are omitted.

[0091] The common table may be defined in a standard, or may be notified from the AP 100 to the STA 200 .

[0092] (3) Method using a different table for each number of streams: Similar to method (2) using a common table, a table of stream number patterns is defined. In method (3), the table size differs (changes) for each number of streams. Figures 10 to 13 show examples of tables of stream number patterns for each of the numbers of streams 1 to 4. In the examples of Figures 10 to 13, stream number patterns are defined that use the same number of bits (1 to 4 bits) as the number of streams 1 to 4.

[0093] This allows the amount of signaling in the table to be reduced depending on the number of streams.

[0094] Similarly to the method (2) using a common table, a table corresponding to a number of bits less than the number of streams may be defined. In this case, for example, the number of stream number patterns may be reduced by modifying (or omitting) some of the stream number patterns defined in the tables shown in Figures 10 to 13.

[0095] The table may also be defined in a standard, for example, or may be notified from the AP 100 to the STA 200 .

[0096] (4) Method of using a bitmap when the number of streams is small: For example, as shown in Figures 10 and 11 for the method of (3) using a different table for each stream, when the number of streams is small (for example, when the number of streams is two or less), the use / non-use of a stream may be notified by a bitmap (value of 0 / 1) corresponding to each stream as in (1) without using a table. On the other hand, when the number of streams is large (for example, when the number of streams is more than two), the stream number pattern may be notified using a table (for example, Figures 12 and 13).

[0097] <Basic Trigger for Notifying Stream Number Pattern> Regarding the examples of notifying the stream number pattern (1) to (4) described above, a method for notifying the stream number pattern by using a Basic Trigger (Basic type trigger frame) for the control signal and extending the format of the Basic Trigger will be described.

[0098] FIG. 14 shows an example of the format of the Common Info field in the Basic Trigger of the EHT, and FIG. 15 shows an example of the format of the User Info field in the Basic Trigger of the EHT.

[0099] In the Common Info, for example, one bit of the Reserved field is extended. In the example of Fig. 14, the one-bit Reserved field of B63 is used to notify the Stream number pattern. This one bit instructs, for example, the STA 200 as to whether or not to reinterpret the User Info for the Stream number pattern notification. For example, the name of this one-bit subfield is "Stream Number Pattern," and the processing contents of the Stream Number Pattern subfield are shown in Fig. 16. As shown in Fig. 16, when the value of the Stream Number Pattern subfield is 0, the User Info field is not reinterpreted, and when the value of the Stream Number Pattern subfield is 1, the User Info field is reinterpreted.

[0100] If the Trigger Type is different from Basic Trigger, the Stream Number Pattern subfield may be set to the Reserved field.

[0101] For example, when the value of the Stream Number Pattern subfield is 1, the STA 200 converts four bits (e.g., B25, B30, B31, and B5 of Trigger Dependent User Info) of the User Info field shown in Fig. 15 into a stream number pattern. These four bits may be used to notify the stream number pattern based on, for example, any of the methods (1) to (4) described above.

[0102] In the Basic Trigger, the extendable bits are 4 bits as shown in Figure 15. Therefore, if, for example, 5 or more bits are used to notify the Stream number pattern, this can be addressed by adding a new Trigger Type or by further reinterpreting some bits of an existing field (e.g., RU Allocation).

[0103] 6, the AP 100 generates a Basic Trigger (including a Stream number pattern) as a control signal and transmits the Basic Trigger to the STA 200. The STA 200 also receives the Basic Trigger from the AP 100.

[0104] Here, the transmission of the UL signal and the transmission of the Basic Trigger (control signal) may be performed in different transmission opportunities (TXOP). Alternatively, the transmission of the UL signal and the Basic Trigger may be performed in a single transmission opportunity. When the UL signal and the Basic Trigger are transmitted in a single transmission opportunity, as shown in Fig. 17, a fixed time (e.g., short interframe space (SIFS)) may be set between the UL signal and the Basic Trigger (e.g., the portion indicated by the omitted line in Fig. 6).

[0105] <STA Reception of Basic Trigger and Acquisition of Stream Number Pattern> The STA 200 (for example, the separator 202 and the preamble demodulator 203) shown in FIG. 6 separates the received Basic Trigger into a preamble signal and a data signal, and demodulates each of them.

[0106] The STA 200 (for example, the data demodulation section 205 and the data decoding section 206) demodulates and decodes the data signal based on the control information acquired when demodulating the preamble signal, and acquires the stream number pattern included in the data signal.

[0107] STA 200 (for example, stream number pattern storage unit 208) compares the acquired stream number pattern with the stream numbers of the UL signal that have already been saved, and outputs the corresponding stream numbers to precoder storage unit 209 and precoding matrix multiplication unit 213. STA 200 (for example, precoding matrix multiplication unit 213) extracts a precoder to be used for UL data transmission (response to the basic trigger) based on the acquired stream number.

[0108] Furthermore, the STA 200 may determine the rank based on, for example, the number of stream numbers (or the number of streams) included in the acquired stream number pattern.

[0109] As an example, the operation when STA 200 having three transmitting antennas transmits an UL signal using three streams (e.g., streams 1, 2, and 3) and obtains a stream number pattern indicating stream numbers 1 and 3 from AP 100 will be described.

[0110] The precoder W that STA 200 applies to the UL signal is shown in equation (2).

[0111] When Streams 1 and 3 are selected in AP 100, the second column of equation (2) is deleted and Precoder W' shown in equations (3) and (4) is applied to UL data transmission.

[0112] When applying W' to UL data, each component is multiplied for each transmission stream of the UL data, similar to the application of the Precoder using the Q-matrix described above.

[0113] In this way, the AP 100 notifies the STA 200 of the stream number pattern associated with the precoder used for the UL signal. For example, the AP 100 implicitly indicates the precoder.

[0114] For example, in the method described in Non-Patent Document 2, a precoder (e.g., a precoding matrix) is notified from the AP to the STA. Here, since the size of the precoder changes depending on the number of UL signal streams or the number of transmit / receive antennas, there is a concern that the overhead of notifying the precoder will increase. In contrast, in Method 1, the AP 100 notifies the STA 200 of a stream number pattern associated with the precoder (e.g., stream number) that the STA 200 has generated in advance. By notifying the stream number pattern, it is possible to reduce the signaling overhead associated with notifying the precoder.

[0115] Furthermore, in implicit feedback, a precoding method with relatively little overhead, channel quality estimation and precoder calculation are performed assuming reversibility between uplink and downlink. Here, with implicit feedback, if reversibility between uplink and downlink is not established, there is a concern that a difference in quality determination for each stream will occur between the STA and the AP, resulting in degradation of precoder performance (or reception quality). In contrast, in method 1, the AP 100 receives an UL signal transmitted from the STA 200, estimates the quality of each stream of the received UL signal, and determines (or selects) a precoder to be used for UL data transmission based on the quality estimation results. As a result, for example, the AP 100 can improve reception quality even when reversibility between uplink and downlink is not established by notifying the STA 200 of a stream number pattern in which precoder coefficients (e.g., columns) applied to streams with poor quality are not used (thinned out).

[0116] Furthermore, in method 1, the stream number pattern may include non-consecutive stream numbers. For example, in a method in which the number of streams is notified from AP 100 to STA 200, STA 200 applies precoders for the notified number of streams, starting from the stream with the first number. In contrast, in method 1, the stream number pattern includes non-consecutive stream numbers, which increases the number of combinations (patterns) of stream numbers for which AP 100 can estimate quality, making it possible to select stream numbers with better reception quality.

[0117] 18, the AP 100 may transmit a Basic Trigger and the STA 200 may transmit UL data multiple times. In this case, the second and subsequent Basic Triggers may be linked to the most recent Precoded NDP. Alternatively, the second and subsequent Basic Triggers may be unnecessary, and the STA 200 may transmit data from the second time onward by inheriting the information from the first Basic Trigger.

[0118] [Method 2] In method 2, the AP 100 transmits a signal (e.g., NDPA) to the STA 200 instructing it to generate a precoder, and transmits a training signal (e.g., NDP) to instruct the STA 200 to estimate the UL channel and generate a precoder.

[0119] After transmitting the NDPA and NDP, the AP 100 also notifies the STA 200 of a control signal (for example, a Trigger frame) that instructs the STA 200 to transmit an UL signal.

[0120] The STA 200 estimates a channel estimation value using a training signal, generates a precoder based on the channel estimation value, and transmits an UL signal by applying the precoder. Here, the UL signal transmitted by the STA 200 may be an NDP to which a precoder is applied (Precoded NDP).

[0121] The AP 100 determines a stream number pattern using a UL signal to which a precoder is applied and transmitted from the STA 200 .

[0122] [Operation Example 2-1] FIG. 19 is a sequence diagram showing an operation example of the AP 100 (simply referred to as AP) and the STA 200 (simply referred to as STA) in Operation Example 2-1 of Method 2.

[0123] <Precoder Generation by STA instructed by AP> The AP 100 (for example, the Data generation unit 112) generates an NDPA frame for instructing the STA 200 to generate a Precoder. Fig. 20 shows an example of the format of the STA Info field in the NDPA frame.

[0124] For example, in method 2, the fields B20 to B24 shown in Fig. 20 are extended. For example, one bit (Reserved) of B20 notifies the STA 200 that after the AP 100 transmits the NDPA and NDP, a Trigger frame instructing the transmission of a Precoded NDP will be transmitted subsequently. As an example, this subfield name is defined as a "Generate Precoder" subfield, and an example of the processing contents corresponding to each value (e.g., 0 or 1) of the Generate Precoder subfield is shown in Fig. 21.

[0125] When the value of the Generate Precoder subfield is 1 in Fig. 21, the AP 100 notifies the scheduling result of the UL signal transmitted by the STA 200 in fields B21 to B24 shown in Fig. 20. For example, the number of streams, that is, the size of the Precoder generated by the STA 200, may be assigned (scheduled) in B21 to B24.

[0126] Also, when the value of the Generate Precoder subfield is 0 in Fig. 21, the AP 100 does not need to notify the scheduling result of the UL signal transmitted by the STA 200 in the fields B21 to B24 shown in Fig. 20. For example, information on the Nc Index subfield may be notified in B21 to B24.

[0127] 20, before the extension, the Nc Index subfield is assigned to B21 to B24. This subfield indicates the number of columns of the compressed beamforming feedback matrix (see, for example, Section 9.4.1.67 of Non-Patent Document 3). In Method 2, the AP 100 notifies the STA 200 of the stream number pattern instead of the compressed beamforming feedback matrix, and therefore, information in the Nc Index subfield does not need to be notified.

[0128] Fig. 22 shows an example of the correspondence between the values ​​set in B21 to B24 shown in Fig. 20 and the control value (e.g., the number of transmitted streams of the UL signal). Fig. 23 shows an example of the number of streams assigned to STA 200 and the effect thereof.

[0129] As shown in FIG. 19, the AP 100 (for example, the preamble generating unit 111 or the data generating unit 112) generates an NDP after transmitting an NDPA, and transmits the NDP.

[0130] STA200 (e.g., separation unit 202, preamble demodulation unit 203, and data demodulation unit 205) separates the NDPA transmitted from AP100 into a preamble signal and a data signal, and demodulates each signal. STA200 (e.g., data decoding unit 206) decodes the NDPA frame of the data signal. When STA200 acquires a value of 1 in the Generate Precoder subfield during decoding of the NDPA frame, it interprets B21 to B24 of the NDPA frame as the number of streams and stores that value.

[0131] Furthermore, when STA200 (for example, preamble demodulation unit 203 and channel estimation unit 204) receives an NDP after receiving an NDPA, it demodulates the NDP and estimates the quality of the DL channel based on the reference signal included in the NDP.

[0132] Here, assuming that there is channel reciprocity between the UL and DL, the STA 200 may estimate the quality of the UL channel from the quality estimate of the DL channel. If there is channel reciprocity between the UL and DL, the UL channel can be derived by Equation (5). In Equation (5), H UL denotes the estimated UL channel matrix, and H DL denotes the estimated channel matrix for DL.

[0133] The STA 200 (e.g., the precoder generation unit 207) generates the estimated UL channel (H UL ), and the number of streams notified from AP 100, a UL precoder is generated.

[0134] Here, for each number of allocated streams shown in FIG. 23, the STA 200 may generate a UL precoder as follows.

[0135] (1) When the number of allocated streams is the maximum number of MIMO streams: STA 200 generates a precoder according to the maximum number of MIMO streams.

[0136] (2) When the number of allocated streams is greater than the maximum number of MIMO streams: STA 200 distributes the number of allocated streams according to the number of precoder generation methods held by STA 200 to generate precoders.

[0137] As an example, a case will be described in which STA 200, whose maximum number of MIMO streams is two, has three precoder generation methods: identity matrix, ZF (Zero Forcing), and MRC (Maximum Ratio Combination), and is notified of an allocation of six streams by NDPA. In this case, STA 200 generates identity matrix, ZF, and MRC precoders using two streams each. These precoders are multiplexed using orthogonal codes and transmitted in a single UL signal. The distribution of the number of allocated streams notified by AP 100 is not limited to the above example. For example, under the same conditions, STA 200 may generate a ZF precoder using three streams, an MRC precoder using two streams, and an identity matrix precoder using one stream. Alternatively, STA 200 may generate ZF and MRC precoders using three streams, without generating an identity matrix precoder.

[0138] This allows the AP 100 to select a stream number across different precoders, so the type of precoder that the STA 200 has applied to the UL signal may be unknown.

[0139] (3) When the number of allocated streams is smaller than the maximum number of MIMO streams: STA 200 generates a precoder according to the notified number of streams.

[0140] An example of generating a UL precoder according to the number of allocated streams has been described above.

[0141] The STA 200 (for example, the precoder storage unit 209 and the stream number pattern storage unit 208) stores the generated precoder and the stream number corresponding to the number of transmitted streams.

[0142] <Transmission of a signal to control a UL signal> As shown in FIG. 19, after transmitting the NDPA and NDP, the AP 100 (for example, the Data generation unit 112) generates a Trigger frame that instructs the STA 200 to transmit a UL signal (Precoded NDP), and transmits the Trigger frame.

[0143] Here, for example, "Precoded UL Signal Trigger" is added as a new Trigger Type of the Trigger frame. Fig. 24 shows an example in which the Trigger type includes the content of the existing Trigger Type subfield (see, for example, Non-Patent Document 3) and the added "Precoded UL Signal Trigger".

[0144] FIG. 25 shows an example of the Common Info field of the Precoded UL Signal Trigger, and FIG. 26 shows an example of the User Info field of the Precoded UL Signal Trigger.

[0145] In the Common Info field shown in FIG. 25 , the subfields (e.g., control information related to data generation) of the existing Common Info field (e.g., FIG. 14 ), UL BW, GI And HE / EHT-LTF Type / Triggered TXOP Sharing Mode, LDPC Extra Symbol Segment, Pre-FEC Padding Factor, PE Disambiguity, UL Spatial Reuse, Special User Info Field Flag, EHT Reserved, and Trigger Dependent Common Info, are set to Reserved in the instruction for NDP transmission without data.

[0146] For example, the UL BW subfield is a subfield that indicates the bandwidth of the TB PPDU, and since the STA 200 transmits an UL signal based on the bandwidth of the NDP of the AP 100, the UL BW subfield is set to Reserved in FIG.

[0147] Also, for example, the GI And HE, EHT-LTF Type, and Triggered TXOP Sharing Mode subfields are information related to TB PPDU and TXOP Sharing, and therefore are set to Reserved in FIG. 25 .

[0148] Furthermore, for example, the Pre-FEC Padding Factor subfield and the PE Disambiguity subfield are reserved because they are information related to the MU PPDU and the TB PPDU.

[0149] Also, for example, since spatial reuse is not taken into consideration in this embodiment, the UL Spatial Reuse subfield is set to Reserved.

[0150] Also, for example, since the Special User Info field is not used in this embodiment, the Special User Info Field Flag subfield is set to Reserved.

[0151] Also, for example, the Trigger Dependent Common Info subfield is not used in this embodiment.

[0152] In the User Info field shown in FIG. 26, the subfields of UL FEC Coding Type, UL EHT-MCS, PS160, and Trigger Dependent User Info from the existing Basic Trigger User Info field (for example, FIG. 15) are reserved.

[0153] For example, the UL FEC Coding Type subfield and the UL EHT-MCS subfield are reserved because they are information related to the TB PPDU.

[0154] Also, for example, since the STA 200 transmits an UL signal based on the band of the NDP of the AP 100, the PS160 subfield is set to Reserved in FIG.

[0155] Also, for example, the Trigger Dependent User Info subfield is not used in this embodiment.

[0156] In addition, in Figs. 25 and 26, subfields (for example, UL Length) similar to the existing Common Info field and the existing User Info field have the same functions and processing contents.

[0157] Figure 27 shows an example of the correspondence between the value and content of the "Number Of HE / EHT-LTF Symbols" subfield of the Common Info field shown in Figure 25. In Figure 27, the existing content is extended to add the content of values ​​5 and 6 (for example, 12 symbols and 16 symbols).

[0158] In the above extension, the P-matrix size (number of LTF symbols × number of LTF symbols) is extended, and the number of STAs and streams that can be multiplexed is increased, thereby aiming to improve throughput.

[0159] In addition, the EHT-LTF symbol, which is the LTF symbol of the EHT version in Figure 27, may be called, for example, a "UHR-LTF symbol" in the case of the UHR version.

[0160] 26, the number of bits in the SS Allocation field and the Number Of Spatial Streams subfield of the User Info field is extended compared to the existing User Info field. This extension (simple extension) changes the maximum number of spatial streams that can be transmitted by one STA 200 from the existing 4 to 16.

[0161] In this way, the number of streams of the UL signal is notified, for example, by the NDPA (B21 to B24) or the Precoded UL Signal Trigger (Number Of Spatial Streams subfield). When notified by the NDPA, the value of the Number Of Spatial Streams subfield of the Precoded UL Signal Trigger may be ignored or may be set to the same value as the value set by the NDPA.

[0162] <Precoded NDP Transmission and Stream Number Pattern Determination> As shown in Fig. 19 , when STA 200 receives a Precoded UL Signal Trigger, it generates a Precoded NDP (UL signal) using the generated Precoder and transmits the generated Precoded NDP to AP 100. For example, STA 200 (e.g., reference signal generation unit 210 and precoding matrix multiplication unit 213) applies the generated Precoder to the generated reference signal.

[0163] When AP 100 receives a Precoded NDP from STA 200, it estimates the channel and reception quality of each stream of the Precoded NDP and determines a stream number pattern, similar to method 1. AP 100 then notifies STA 200 of the stream number pattern, for example, by using a Basic Trigger. STA 200 applies a Precoder and transmits UL data based on the stream number notified by the stream number pattern.

[0164] In operation example 2-1, the number of streams of the UL signal can be set to a number greater or less than the maximum number of streams in MIMO, so that it is possible to apply multiple precoder types and increase the number of STAs that multiplex and transmit UL signals.

[0165] For example, when multiple precoders are used (for example, when the number of allocated streams is greater than the maximum number of streams in MIMO), AP 100 can select the stream with the best reception quality (for example, the best) across different types of precoders.

[0166] Furthermore, for example, when the number of STAs that multiplex UL signals is increased (for example, when the number of allocated streams is less than the maximum number of streams in MIMO), AP 100 can notify the number of streams using NDPA, thereby scheduling multiple STAs 200 and improving the throughput of the entire wireless communication system.

[0167] Furthermore, by the AP 100 notifying the STA 200 in advance by the NDPA whether or not there is a Precoded UL Signal Trigger after the NDP, the STA 200 can generate a Precoder immediately after receiving the NDP, that is, before receiving the Precoded UL Signal Trigger, as shown in Fig. 19. This increases the possibility that even a STA with low processing power can generate a Precoder before transmitting an UL signal.

[0168] The STA 200 may generate a precoder based on a training signal (e.g., LTF) transmitted simultaneously with a control signal (e.g., a trigger frame) transmitted from the AP 100. Fig. 28 shows an example of a sequence in this case. In this case, the AP 100 instructs the STA 200 to generate a precoder and transmit an UL signal by using a control signal (Precoded UL Signal Trigger).

[0169] Furthermore, the AP 100 may apply a unit matrix to the reference signal and the data signal as a precoding matrix so that the STA 200 can generate a precoder based on the training signal, thereby reducing the overhead of the NDPA and NDP.

[0170] Furthermore, the Precoded UL Signal Trigger of Method 2 may be used in combination with a BFRP (BF Report Poll) Trigger. For example, the sequence shown in FIG. 29 may be applied.

[0171] [Operation Example 2-2] FIG. 30 is a sequence diagram showing an operation example of the AP 100 (simply referred to as AP) and the STA 200 (simply referred to as STA) in Operation Example 2-2 of Method 2.

[0172] In Operation Example 2-2, the STA 200 transmits one or more packets (UL signals) in response to the control signal (Precoded UL Signal Trigger) used in Operation Example 2-1. At this time, the STA 200 may transmit packets using different precoders. The AP 100 selects a packet and stream number pattern with good reception quality. In the example of FIG. 30, the STA 200 transmits three packets in a time-multiplexed manner.

[0173] <Instruction to Generate a Precoder> In the operation example 2-2, similarly to the operation example 2-1, the AP 100 instructs the STA 200 to generate a Precoder by transmitting an NDPA and an NDP.

[0174] After receiving the NDP, the STA 200 performs channel estimation and generates a precoder based on the number of streams notified by the NDPA. At this time, the type of precoder generated by the STA 200 and the number of transmission packets may depend on the implementation of the STA 200 or capability (already shared between the AP and the STA). In addition, the number of transmission packets may be notified to the STA 200 from the AP 100 by, for example, the NDPA or a trigger frame.

[0175] The number of streams in each packet is the same (for example, the number notified by NDPA), but the number of streams in each packet may be different.

[0176] The STA 200 (for example, the stream number pattern storage unit 208) stores the stream numbers associated with each precoder as different stream numbers across the precoders.

[0177] The STA 200 (for example, the Precoder storage unit 209) stores all the generated Precoders.

[0178] After transmitting the NDP, the AP 100 generates a Precoded UL Signal Trigger and transmits the generated Precoded UL Signal Trigger to the STA 200 .

[0179] <Packet Transmission> When the STA 200 receives a Precoded UL Signal Trigger, the STA 200 applies the generated Precoder to each packet. For example, the STA 200 (e.g., the reference signal generating unit 210 and the control signal generating unit 212) generates a reference signal and a control signal to be included in the packet. Furthermore, the STA 200 (e.g., the precoding matrix multiplying unit 213) applies the generated Precoder to the reference signal of each packet.

[0180] The STA 200 (for example, the orthogonalization unit 215) multiplies the reference signal included in the stream of each packet by an orthogonal code to orthogonalize the reference signal. The orthogonal codes used between packets may be the same or different.

[0181] The STA 200 transmits each packet generated by the above operation to the AP 100 .

[0182] <Packet reception and stream number acquisition> When AP 100 (e.g., channel estimation unit 105, quality estimation unit 106, and precoder selection unit 107) receives a packet from STA 200, it estimates the channel and reception quality of each stream, as in method 1, and determines a stream number pattern for each packet.

[0183] At this time, the AP 100 compares the reception quality (for example, capacity) between packets and notifies the STA 200 of the stream number pattern of the packet with the best reception quality.

[0184] For example, if STA200 transmits three packets (e.g., Packet1, Packet2, and Packet3) using three streams, a stream number pattern is determined from among stream numbers 1, 2, and 3 for Packet1, stream numbers 4, 5, and 6 for Packet2, and stream numbers 7, 8, and 9 for Packet3, and notified to STA200.

[0185] As another notification method, the AP 100 may notify the STA 200 of a field indicating the packet number and a field indicating the stream number separately. For example, in the example using three streams and three packets described above, the AP 100 may notify the STA 200 of a stream number pattern including Packet 1 and Streams 1 and 2.

[0186] The STA 200 applies a precoder based on the stream number pattern notified by the AP 100 and transmits UL data.

[0187] In operation example 2-2, the STA 200 transmits one or more UL signals based on the control information notified by the AP 100, so that the AP 100 can select the optimum precoder type and stream number for reception.

[0188] Note that the transmitting antenna of the STA 200 may be changed for each packet (for example, this is called antenna selecting), and the AP 100 may select the transmitting antenna that is best for reception based on the stream number pattern.

[0189] Furthermore, the multiplexing method for transmitting multiple packets is not limited to time multiplexing, and other orthogonal resources, such as frequency multiplexing, may be used in combination with orthogonal codes. Information regarding the orthogonal resources may be reported from the AP 100 to the STA 200, for example. This allows the AP 100 to select the optimal orthogonal resource (e.g., time resource or frequency resource) for reception. Figure 31 shows an example of orthogonal resources included in the control signal and their effects.

[0190] Also, for example, the AP 100 may directly notify the STA 200 of the type of precoder and control the STA 200 to form a beam that is optimal for reception at the AP 100. For example, a subfield (e.g., 3 bits) notifying the precoder type may be added to the STA Info of the NDPA (e.g., FIG. 20) or the User Info of the Precoded UL Signal Trigger (e.g., FIG. 26). The name of this added subfield may be defined as a "Precoder Type" subfield, for example. FIG. 32 shows an example of the correspondence between the value and content of the Precoder Type subfield. The Precoder Type subfield may include a value (e.g., value 0 in FIG. 32) indicating that the STA 200 generates a precoder without the AP 100 specifying the type of precoder. The AP 100 may also determine the type of precoder to be notified based on the capability information of the STA 200.

[0191] In addition, the capability of STA200 (e.g., the method of generating a precoder) may be shared between the AP and STA at the start of the above-mentioned sequence by notifying AP100 from STA200 upon association with AP100, by notifying separately by PPDU or the like, or by being defined in a specification or by notification by beacon.

[0192] The STA 200 generates a precoder based on the notified precoder type and number of streams, multiplies the precoder by the UL signal, and transmits the result.

[0193] Furthermore, the AP 100 may allocate multiple User Info fields to one STA 200 and indicate multiple Precoder types to be notified in each User Info field. In this case, based on Operation Example 2-2, the STA 200 may generate each packet using multiple Precoder types indicated by the AP 100 and multiplex and transmit the packets using orthogonal resources such as time or frequency.

[0194] An example of the operation of the AP 100 and the STA 200 has been described above.

[0195] As described above, in this embodiment, AP 100 transmits to STA 200 a stream number pattern associated with the UL signal from STA 200, and receives UL data precoded based on the stream number pattern at STA 200. Furthermore, STA 200 receives the stream number pattern associated with the UL signal from STA 200, and transmits UL data precoded based on the received stream number pattern.

[0196] As a result, AP 100 only needs to notify STA 200 of a pattern of stream numbers associated with an UL signal from STA 200 (for example, a stream constituting the UL signal), thereby suppressing an increase in overhead compared to when AP 100 notifies STA 200 of a precoder determined by AP 100. Furthermore, since AP 100 can determine the stream number (or precoder) based on the reception quality of the UL signal, deterioration of reception quality is suppressed even when reversibility between uplink and downlink is not established, for example. Therefore, according to this embodiment, it is possible to improve the efficiency of transmission control in wireless communication.

[0197] Second Embodiment [Configuration of Wireless Communication System] A wireless communication system according to this embodiment may include, for example, an AP 100a and an STA 200. Two or more APs 100a and two or more STAs 200 may exist in the wireless communication system.

[0198] 33 is a block diagram showing an example of the configuration of the AP 100a according to the present embodiment. The AP 100a differs from the first embodiment in that it includes a MAP (Multi-AP) control unit 114.

[0199] In FIG. 33, the MAP control unit 114 instructs the data generation unit 112 to generate a control signal (e.g., a trigger frame, also called a MAP trigger) for cooperation between APs in MAP cooperation, or a signal to be transmitted in MAP cooperation (e.g., an NDPA).

[0200] [Configuration Example of STA 200] The configuration of the STA 200 according to this embodiment may be the same as the configuration of the STA 200 according to the first embodiment (for example, FIG. 5).

[0201] [Example of Operation of AP 100a and STA 200] An example of operation of the AP 100a and STA 200 will be described below.

[0202] [Method 3] FIG. 34 is a sequence diagram showing an example of the operation of the AP 100a (simply referred to as AP) and the STA 200 (simply referred to as STA) in Method 3.

[0203] In the example of FIG. 34, the Sharing AP is AP1, the Shared AP is AP2, and the STAs 200 connected to AP1 and AP2 are STA1 and STA2, respectively.

[0204] Method 3 utilizes Joint NDP sounding in MAP coordinated transmission (see, for example, Non-Patent Documents 7 and 8).

[0205] 34 , in Method 3, between cooperative APs, a Sharing AP transmits a MAP Trigger to a Shared AP. When the Shared AP receives the MAP Trigger, it transmits a MAP NDPA, a MAP NDP, and a Precoded UL Signal Trigger (similar to Method 2, for example) to each STA 200 (STA 200 connected to the Sharing AP and the Shared AP) simultaneously with the Sharing AP.

[0206] This enables channel estimation between the Sharing AP and the Shared AP and the STA 200 connected to each AP. Furthermore, by transmitting and sharing information about reception quality measured at the Shared AP to the Sharing AP, it is possible to determine a stream number pattern (select a Precoder for the STA) that optimizes reception at multiple APs 100a.

[0207] <Generation of MAP Trigger> The Sharing AP (for example, the Data generator 112) generates a MAP Trigger.

[0208] The MAP Trigger requests the Shared AP to transmit an NDPA similar to that in Method 2 (an NDPA instructing the STA 200 to generate a Precoder), for example.

[0209] The signal (MAP Trigger) requesting transmission of an NDPA similar to that of Method 2 may be a Control frame different from the Trigger frame, or another newly defined signal. In this case, the Control frame may include information (e.g., a Subfield) requesting transmission of an NDPA similar to that of Method 2.

[0210] In Method 3, an advantage of using a trigger frame is that transmission opportunities can be shared (TXOP sharing) with one or more shared APs, and the number of propagation paths between APs and STAs that can be channel estimated can be increased.

[0211] The format of the MAP Trigger may be, for example, the same as the format of an existing Basic Trigger.

[0212] In Method 3, for example, a "MAP Trigger (Sounding)" corresponding to the MAP Trigger requesting transmission of an NDPA is newly added to the Trigger Type. Note that the Trigger Type may include the Precoded UL Signal Trigger of the first embodiment. Fig. 35 shows an example of the Trigger Type when a MAP Trigger (Sounding) is newly added.

[0213] Also, Fig. 36 shows an example of the format of the entire trigger frame for MAP Trigger (Sounding). In Fig. 36, in the case of MAP Trigger (Sounding), a broadcast address is set in the RA (Receiver Address) field.

[0214] Fig. 37 shows an example of the Common Info field of a MAP Trigger (Sounding), and Fig. 38 shows an example of the User Info field of a MAP Trigger (Sounding). Note that the formats shown in Fig. 37 and Fig. 38 are examples that use the format of a Basic Trigger.

[0215] In the MAP Trigger (Sounding), a "Precoder Calculation Indication" subfield (for example, 1 bit) is added to the Common Info field. In the example of Fig. 37, B53 (reserved in the existing format) is set in the Precoder Calculation Indication subfield. The Precoder Calculation Indication subfield notifies the Shared AP whether or not to transmit an NDPA instructing the STA 200 to generate a Precoder.

[0216] The NDPA that instructs the generation of a Precoder mentioned above refers to the NDPA in which the value of the Generate Precoder subfield is set to 1 in Method 2 (for example, FIGS. 20 and 21).

[0217] Figure 39 shows an example of the correspondence relationship between the value and content of the Precoder Calculation Indication subfield. In Figure 39, when the value of the Precoder Calculation Indication subfield is 1, the Shared AP is requested to transmit an NDPA instructing the generation of a Precoder to STA 200, and when the value of the Precoder Calculation Indication subfield is 0, the Shared AP is not requested to transmit an NDPA instructing the generation of a Precoder to STA 200. Also, in Figure 39, when the value of the Precoder Calculation Indication subfield is 0, the procedure of the already proposed Joint NDP sounding (see, for example, Non-Patent Documents 7 and 8) may be implemented.

[0218] In addition, in MAP Trigger (Sounding), the Trigger Dependent Common Info field does not need to be used.

[0219] In addition, in the User Info field of the MAP Trigger (Sounding) (for example, FIG. 38), the AID (Association ID (Identification)) of the Shared AP is set in the AID12 subfield. Also, the Trigger Dependent User Info does not need to be used.

[0220] <Transmission of MAP NDPA> The Sharing AP and Shared AP (for example, the MAP control unit 114) instruct the Data generation unit 112 to generate a MAP NDPA based on information related to the MAP Trigger.

[0221] MAP NDPA may be a format obtained by extending the existing NDPA frame as shown in Fig. 40. In Fig. 40, the value of the "Generate Precoder" subfield in the STA Info field is set to 1, and STA 200 is instructed to generate a Precoder. Note that if the value of the Generate Precoder subfield is set to 0, STA 200 does not need to be instructed to generate a Precoder.

[0222] When the Generate Precoder subfield is 1, B21 to B24 shown in FIG. 40 may notify each STA 200 of the number of streams of the UL signal transmitted by the STA 200 (similar to method 2).

[0223] 40, B25 to B30 are set in the "Joint NDP sounding AP ID" subfield to notify the identifier of the AP 100a that transmits the MAP NDP. This identifier may be an identifier (different from the MAC address) determined by the AP that manages MAP cooperation (Coordination AP) during negotiation of the MAP cooperation set.

[0224] Furthermore, by allocating a plurality of STA Info fields to one STA 200, information on a plurality of APs 100a (for example, all APs 100a) that transmit MAP NDP is notified.

[0225] However, the number of streams of the UL signal (e.g., B21 to B24) may all be the same value in multiple STA Info fields assigned to one STA 200. Alternatively, the number of streams of the UL signal may be set in the first STA Info field among multiple STA Info fields, and the other STA Info fields (B21 to B24) may be reserved.

[0226] As shown in FIG. 34, the Sharing AP and the Shared AP transmit the generated MAP NDPA at the same time to the STA 200 connected to the AP (STA1 for AP1, STA2 for AP2).

[0227] STA200 demodulates and decodes the received MAP NDPA and obtains the destination AP and number of streams of the UL signal (Precoded NDP) based on the Joint NDP sounding AP ID and the number of streams (e.g., B21 to B24) contained in the Data signal.

[0228] <Transmission of MAP NDP> The Sharing AP and the Shared AP (for example, the preamble generating unit 111) generate a MAP NDP after transmitting a MAP NDPA.

[0229] Here, the number of rows and the first row number of the orthogonal code (P-matrix) that the Shared AP applies to the MAP NDP are values ​​notified by the “Number Of Spatial Streams” subfield and the “Starting Spatial Stream” subfield of the MAP Trigger (e.g., FIG. 38).

[0230] For example, the Sharing AP notifies the Shared AP of the number of rows (Number Of Spatial Streams) and the starting row number (Starting Spatial Stream) of the orthogonal code to be applied to the MAP NDP. For example, if the Sharing AP and Shared AP each transmit the MAP NDP using four streams, the Sharing AP notifies the Shared AP of Number Of Spatial Streams = 3 (four streams) and Starting Spatial Stream = 4 using a MAP Trigger. This notifies the Shared AP that, for example, the Sharing AP will use four rows with indexes 0 to 3, and the Shared AP will use four rows with indexes 4 to 7.

[0231] As shown in FIG. 34, the Sharing AP and the Shared AP transmit the generated MAP NDP at the same time and with the same frequency.

[0232] <Precoder Generation by STA> When the STA 200 receives the MAP NDP, it demodulates the preamble signal included in the MAP NDP, estimates the channel, and generates a precoder. For example, the STA 200 (e.g., the channel estimation unit 204) may estimate the DL channel for each AP 100a and the UL channel assuming reversibility based on the MAP NDP. For example, the STA 200 (e.g., the precoder generation unit 207) generates a precoder based on the number of streams notified by the MAP NDP.

[0233] Here, the generated Precoder forms a beam for each AP 100a that has transmitted the MAP NDP.

[0234] <Precoded UL Signal Trigger Transmission by AP> Each AP 100a (e.g., Data generation unit 112) generates a Precoded UL Signal Trigger after transmitting a MAP NDP. For example, the format of the User Info field in the Precoded UL Signal Trigger of Method 2 may be extended as shown in Fig. 41. For example, in Fig. 41, a "Joint Sounding" subfield is newly added. Fig. 42 shows an example of the correspondence between the value and content of the Joint Sounding subfield.

[0235] As shown in FIG. 34, the Sharing AP and the Shared AP transmit the generated Precoded UL Signal Trigger to the STA 200.

[0236] When the STA 200 receives a Precoded UL Signal Trigger, it separates the Preamble signal and Data signal of the Precoded UL Signal Trigger and demodulates each of them. In addition, the STA 200 (e.g., Data decoding section 206) acquires control information included in the Precoded UL Signal Trigger.

[0237] The STA 200 (for example, the reference signal generating section 210 and the control signal generating section 212) generates a preamble signal to be included in the UL signal.

[0238] At this time, STA200 sets the AP notified by the Joint NDP sounding AP ID of the MAP NDPA as the destination. For example, in the example of Fig. 42, if the value of the Joint Sounding subfield is 1, STA200 determines that the NDP received by STA200 corresponds to the MAP NDP, and determines the destination of the UL signal to be the Sharing AP and Shared AP. Also, in the example of Fig. 42, if the value of the Joint Sounding subfield is 0, STA200 determines that the NDP received by STA200 does not correspond to the MAP NDP, and that the Trigger frame is a Precoded UL Signal Trigger similar to Method 2, and determines the destination of the UL signal.

[0239] The STA 200 (for example, the precoding matrix multiplication unit 213) applies the generated precoder to the reference signal (and to the data signal if the UL signal is a TB PPDU).

[0240] When MAP cooperation is performed, as shown in FIG. 34, the STA 200 transmits the generated UL signal to the Sharing AP and the Shared AP.

[0241] <Sharing of Quality Information Between APs> Each AP 100a performs channel estimation and reception quality estimation based on a preamble signal included in a received UL signal.

[0242] The Shared AP (e.g., the preamble generating unit 111 and the data generating unit 112) generates a data signal (e.g., an MU PPDU) for transmitting quality information (e.g., reception quality information) estimated by the Shared AP to the Sharing AP. As shown in Fig. 34, the Shared AP transmits the generated data signal to the Sharing AP. As a result, the reception quality between each AP 110a and the STA 200 is shared among the multiple APs 110a.

[0243] <Stream Number Pattern Determination and UL Data Transmission> After receiving a Data signal from the Shared AP, the Sharing AP demodulates and decodes it, and stores reception quality information.

[0244] The Sharing AP (for example, the Precoder selection unit 107) determines the stream number pattern for each STA 200 based on the received reception quality information from the Shared AP and the reception quality information estimated by the Sharing AP from the UL signal.

[0245] For example, as shown in Fig. 34, a sharing AP (e.g., data generation unit 112) notifies each STA 200 of the transmission of UL data using the Basic Trigger of method 1. In the example of Fig. 34, AP1 (sharing AP) notifies STA1 connected to AP1 of a stream number so as not to point a beam toward AP2 (shared AP). AP1 also notifies STA2 connected to AP2 of a stream number so as not to point a beam toward AP1 but to point a beam toward AP2.

[0246] When the STA 200 receives the Basic Trigger, it applies a Precoder to the UL data signal based on the acquired Stream number pattern, for example, in the same way as in Method 1, and transmits the UL data to each destination AP 100a.

[0247] The above describes an example of the operation of the AP 100a and the STA 200 according to this embodiment.

[0248] In this embodiment (method 3), multiple APs 100a cooperate to perform NDP sounding, which enables UL precoder selection that takes into account interference with Overlapping Basic Service Set (OBSS) APs, and is therefore expected to improve system throughput.

[0249] (Variations) Below, we will explain a method of extending each of the above embodiments (e.g., Methods 1 to 3) to UL MU-MIMO, in which UL signals and UL data multiplexed by multiple STAs 200 are transmitted to one AP (AP 100 or AP 100a).

[0250] In the case of MU conditions, the techniques in methods 1 to 3 may be simply extended. Here, the spatial streams assigned to each STA 200 have different leading indexes so that they are orthogonal to each other. For this reason, for example, in the User Info field (e.g., FIG. 15) of the Basic Trigger of method 1, by setting the Starting Spatial Stream subfield (e.g., B26 to B29) for each STA 200, code multiplexing between MUs using orthogonal codes (e.g., P-matrix) is enabled.

[0251] As an example, we will explain a case where STA1 and STA2 each transmit UL signals using three streams to one AP (AP100 or AP100a), and the AP notifies STA1 of stream numbers 1 and 3 and notifies STA2 of stream numbers 1, 2, and 3.

[0252] In this case, STA1 can use the first row of the P-matrix, so the value of Starting Spatial Stream for STA1 is set to 0 (corresponding to the first row), and two-stream transmission with stream numbers 1 and 3 is notified. Since two rows (for two streams) of the P-matrix are used for STA1, the value of Starting Spatial Stream for STA2 becomes 2 (e.g., corresponding to the third row), and three-stream transmission is notified. Here, for example, if STA3 is to be further multiplexed, five rows (for five streams) of the P-matrix are used for STA1 and STA2, so the value of Starting Spatial Stream for STA3 becomes 5 (e.g., corresponding to the sixth row).

[0253] By multiplexing multiple STAs 200 using MUs in methods 1 to 3, the AP can select a pair of MUs (e.g., a combination of STAs 200 and the number of streams) with good reception quality at the AP by taking into account the reception quality of precoders that are not orthogonal between the STAs 200.

[0254] The embodiments of the present disclosure have been described above.

[0255] In the above embodiments, BF between AP and STA is described, but the above embodiments are not limited to application to communication between AP and STA, and may also be applied to communication between APs of MAP, for example.

[0256] Furthermore, in each of the above embodiments, the "control signal" including the Stream number pattern may be, for example, a Trigger frame, or may be a signal other than a Trigger frame.

[0257] Furthermore, in each of the above embodiments, the time corresponding to "most recent" (e.g., represented as X) may be specified (defined) in advance in a standard, or may be notified to the STA 200 from an AP (e.g., AP 100 or AP 100a) by a beacon or the like. For example, if time X has elapsed since the transmission timing of the UL signal, the STA 200 may transmit the UL data without precoding. Also, for example, an identifier of the UL signal may be transmitted from the AP in order to associate a stream number pattern with an UL signal other than the most recent UL signal. The identifier of the UL signal may be an identifier (e.g., also referred to as a token) temporarily issued for each UL signal, or may be an identifier assigned to each precoder. In the case of an identifier assigned to each precoder, the same identifier may be assigned to multiple UL signals using the same precoder.

[0258] The UL signal identifier may be included in a control signal (e.g., a trigger frame) from the AP 100. For example, for the User Info field of the Basic Trigger shown in Fig. 15, bits of existing subfields (e.g., two bits of the Preferred AC subfield in the Trigger Dependent User Info, or one bit each from the RU Allocation subfield and the PS160 subfield) may be used as subfields for notifying the UL signal identifier.

[0259] Furthermore, the AP 100 may include the identifier of the UL signal in a trigger frame of a new trigger type and notify the STA 200. For example, as shown in Fig. 43 , a "Stream Number Indication Trigger" that is a new trigger type may be added as a control signal including the identifier of the UL signal.

[0260] Here, the format of the Stream Number Indication Trigger may be the same as that of an existing Basic Trigger. Figure 44 shows an example of the Common Info field of the Stream Number Indication Trigger, and Figure 45 shows an example of the User Info field of the Stream Number Indication Trigger. Note that the formats shown in Figures 44 and 45 are examples of the Basic Trigger format.

[0261] Here, in the User Info field shown in Figure 45, the Stream Number Pattern subfield is a subfield that uses 4 bits to notify the stream number pattern shown in Embodiment 1, Figures 10 to 13, and Figure 15. Also, the UL Signal ID subfield shown in Figure 45 is a subfield that uses 8 bits to notify the identifier of the UL signal (UL signal transmitted before the Stream Number Indication Trigger transmitted by AP 100) that is associated with the stream number pattern. Note that the number of bits in the Stream Number Pattern subfield and the UL Signal ID subfield is an example, and other numbers of bits may be used.

[0262] Furthermore, in each of the above embodiments, the UL transmission operation when there is no Basic Trigger (when STA 200 does not receive a Trigger frame) may be any of the following: (A) STA 200 performs precoding based on the most recent instruction from AP 100 and transmits UL data. (B) STA 200 transmits UL data without precoding. (C) AP (AP 100 or AP 100a) determines (or selects) either operation (A) or operation (B) and notifies STA 200 by a beacon or the like.

[0263] Furthermore, in each of the above embodiments, the operation of an STA supporting an existing standard may be any of the following: (A) The STA does not generate a Precoder. The STA provides feedback in response to an NDP from the AP. The STA treats NDPAs of Methods 2 and 3 as NDPAs of the existing standard. (B) For operation (A), the STA does not transmit feedback until it receives a BFRP (BF Report Poll) from the AP. (C) The STA does not generate a Precoder or transmit a UL signal.

[0264] Furthermore, in each of the above-described embodiments, the field (or subfield) used for notifying control information is an example, and other fields or subfields may be used. Furthermore, the number of bits used for notifying control information in each field or subfield is an example, and other numbers of bits may be used. Furthermore, the term "UHR" used in the name of a field or subfield may be omitted, or, instead of the term "UHR", another term indicating a different standard version, a terminal capability, or the like may be used.

[0265] Furthermore, the signal formats described in each of the above-mentioned embodiments are merely examples, and other configurations may be used in which at least one of other fields is added and some fields is deleted, and other configurations may be used in which at least one of other subfields is added and some subfields are deleted in each of the above-mentioned fields.

[0266] Furthermore, in the above embodiment, as an example, a case based on the format defined in IEEE 802.11 has been described, but the format to which an embodiment of the present disclosure is applied is not limited to the IEEE 802.11 format.

[0267] Furthermore, in the above embodiment, the value, size (number of bits) of the control information notified to STA 200, and the content corresponding to the value of the control information are merely examples, and other values, sizes, and content may also be used.

[0268] The present disclosure can be realized by software, hardware, or software in conjunction with hardware. Each functional block used in the description of the above embodiments may be partially or entirely realized as an LSI, which is an integrated circuit, and each process described in the above embodiments may be partially or entirely controlled by a single LSI or a combination of LSIs. The LSI may be composed of individual chips, or may be composed of a single chip that includes some or all of the functional blocks. The LSI may have data input and output. Depending on the degree of integration, the LSI may also be called an IC, system LSI, super LSI, or ultra LSI.

[0269] The integrated circuit method is not limited to LSI, and may be realized by a dedicated circuit, a general-purpose processor, or a dedicated processor. Also, a field programmable gate array (FPGA) that can be programmed after LSI manufacturing, or a reconfigurable processor that can reconfigure the connections and settings of circuit cells within the LSI, may be used. The present disclosure may be realized as digital processing or analog processing.

[0270] Furthermore, if an integrated circuit technology that can replace LSI emerges due to advances in semiconductor technology or other derivative technologies, it is natural that such technology may be used to integrate functional blocks. The application of biotechnology, etc. is also a possibility.

[0271] The present disclosure may be implemented in any type of apparatus, device, or system (collectively referred to as a communications apparatus) that has a communications function. The communications apparatus may include a radio transceiver and processing / control circuitry. The radio transceiver may include a receiver and a transmitter, or both functions. The radio transceiver (transmitter and receiver) may include a radio frequency (RF) module and one or more antennas. The RF module may include an amplifier, an RF modulator / demodulator, or the like. Non-limiting examples of communication devices include telephones (e.g., cell phones, smartphones), tablets, personal computers (PCs) (e.g., laptops, desktops, notebooks), cameras (e.g., digital still / video cameras), digital players (e.g., digital audio / video players), wearable devices (e.g., wearable cameras, smartwatches, tracking devices), game consoles, digital book readers, telehealth / telemedicine devices, communication-enabled vehicles or mobile transportation (e.g., cars, airplanes, ships), and combinations of the above devices.

[0272] The communication devices are not limited to portable or mobile devices, but also include any kind of non-portable or fixed equipment, devices, and systems, such as smart home devices (such as home appliances, lighting equipment, smart meters or measuring devices, control panels, etc.), vending machines, and any other "things" that may exist on an IoT (Internet of Things) network.

[0273] Communications include data communications via cellular systems, wireless LAN systems, communication satellite systems, and the like, as well as data communications via combinations of these.

[0274] A communications apparatus also includes devices such as controllers and sensors connected or coupled to a communications device that performs the communications functions described in this disclosure, such as controllers and sensors that generate control and data signals used by the communications device to perform the communications functions of the communications apparatus.

[0275] The communication apparatus also includes infrastructure facilities, such as base stations, access points, and any other apparatus, device, or system that communicates with or controls the various apparatuses listed above, but are not limited to these.

[0276] An access point according to one embodiment of the present disclosure includes a transmitting circuit that transmits to a terminal information regarding a pattern of a stream associated with an uplink signal from the terminal, and a receiving circuit that receives a precoded signal based on the pattern.

[0277] In one embodiment of the present disclosure, the pattern includes at least one of a plurality of streams to be applied to the upstream signal.

[0278] In one embodiment of the present disclosure, the pattern includes non-consecutive numbers among the numbers assigned to the plurality of streams.

[0279] In one embodiment of the present disclosure, the upstream signal is a Null Data Packet (NDP) transmitted using the plurality of streams, or a signal including data transmitted using the plurality of streams.

[0280] In one embodiment of the present disclosure, the uplink signal is a signal that the access point receives from the terminal within a specified time period.

[0281] In one embodiment of the present disclosure, the uplink signal is the most recently received signal among signals received by the access point from the terminal.

[0282] In one embodiment of the present disclosure, the transmitting circuit transmits a signal instructing the generation of a precoder and a training signal to the terminal, and the pattern is determined using the uplink signal to which the precoder is applied, which is generated based on a channel estimation value estimated at the terminal using the training signal.

[0283] In one embodiment of the present disclosure, the transmission circuit transmits a control signal to the terminal instructing the terminal to transmit the uplink signal.

[0284] In one embodiment of the present disclosure, the pattern is determined based on channel estimates between the terminal and each of a plurality of access points.

[0285] A terminal according to one embodiment of the present disclosure includes a receiving circuit that receives information regarding a pattern of a stream associated with an uplink signal from the terminal, and a transmitting circuit that transmits a precoded signal based on the pattern.

[0286] In a communication method according to an embodiment of the present disclosure, an access point transmits, to a terminal, information regarding a pattern of a stream associated with an uplink signal from the terminal, and receives a signal precoded based on the pattern.

[0287] In a communication method according to an embodiment of the present disclosure, a terminal receives information regarding a pattern of a stream associated with an uplink signal from the terminal, and transmits a precoded signal based on the pattern.

[0288] The disclosures of the specification, drawings and abstract contained in Japanese Patent Application No. 2023-191792, filed November 9, 2023, are incorporated herein by reference in their entirety.

[0289] One embodiment of the present disclosure is useful in wireless communication systems.

[0290] 100, 100a AP 101, 201 Radio transmission / reception unit 102, 202 Separation unit 103 Orthogonal separation unit 104, 203 Preamble demodulation unit 105, 204 Channel estimation unit 106 Quality estimation unit 107 Precoder selection unit 108, 205 Data demodulation unit 109, 206 Data decoding unit 110, 208 Stream number pattern storage unit 111 Preamble generation unit 112, 211 Data generation unit 113, 216 Multiplexing unit 114 MAP control unit 200 STA 207 Precoder generation unit 209 Precoder storage unit 210 Reference signal generation unit 212 Control signal generation unit 213 Precoding matrix multiplication unit 214 Modulation unit 215 Orthogonalization unit

Claims

1. An access point comprising: a transmitting circuit that transmits, to a terminal, information regarding a pattern of a stream associated with an uplink signal from the terminal; and a receiving circuit that receives a signal precoded based on the pattern.

2. The access point according to claim 1, wherein the pattern includes at least one of a plurality of streams to be applied to the upstream signal.

3. The access point according to claim 2, wherein the pattern includes non-consecutive numbers among the numbers assigned to the plurality of streams.

4. The access point according to claim 2, wherein the uplink signal is a Null Data Packet (NDP) transmitted using the multiple streams, or a signal including data transmitted using the multiple streams.

5. The access point according to claim 1, wherein the upstream signal is a signal received by the access point from the terminal within a specified period of time.

6. The access point according to claim 1, wherein the uplink signal is the most recently received signal among signals received by the access point from the terminal.

7. The access point according to claim 1, wherein the transmission circuit transmits a signal instructing the generation of a precoder and a training signal to the terminal, and the pattern is determined using the uplink signal to which the precoder is applied, the precoder being generated based on a channel estimation value estimated in the terminal using the training signal.

8. The access point according to claim 7, wherein the transmission circuit transmits a control signal to the terminal to instruct the terminal to transmit the uplink signal.

9. The access point according to claim 1, wherein the pattern is determined based on channel estimates between the terminal and each of a plurality of access points.

10. A terminal comprising: a receiving circuit for receiving information relating to a pattern of a stream associated with an uplink signal from a terminal; and a transmitting circuit for transmitting a precoded signal based on the pattern.

11. A communication method, comprising: an access point transmitting, to a terminal, information regarding a pattern of a stream associated with an uplink signal from the terminal; and receiving a precoded signal based on the pattern.

12. A communication method, comprising: a terminal receiving information regarding a pattern of a stream associated with an uplink signal from the terminal; and transmitting a precoded signal based on the pattern.