METHOD AND APPARATUS FOR CHANNEL STATE INFORMATION FEEDBACK IN JOINT TRANSMISSION - Patent application

Abstract

A method for a STA to determine channel state information (CSI) for a wireless channel includes receiving multiple sounding data transmissions from multiple APs over multiple communication channels. The method further includes, for each of the communication channels, estimating channel state information (CSI) for the channel based on the multiple sounding data transmissions received over each of the communication channels. Additionally, the method includes aggregating the channel state information for each of the communication channels to generate aggregated CSI and transmitting the aggregated CSI to the multiple APs.

Description

[Technical field]

[0001] The present invention relates generally to the field of wireless communication systems, and more particularly to sounding protocols when using Access Point (AP) cooperation. [Background technology]

[0002] A Wireless Local Area Network (WLAN) communication system, such as the IEEE® 802.11 family of Wi-Fi® protocols, includes wireless communication devices that transmit and receive signals, including Access Points (APs), which act as an interface between the WLAN and one or more further networks, and Stations (STAs), which are devices that support the 802.11 protocol and exchange signals with the APs.

[0003] Both APs and STAs can employ multiple-input multiple-output (MIMO) technology, where wireless communication devices have multiple antennas, allowing techniques such as beamforming to be used to increase the performance and throughput of wireless networks.

[0004] The AP uses a sounding protocol to estimate the characteristics of the communications channel between antennas on the AP and antennas on the STAs. Sounding packets are transmitted from the AP to the STAs. The STAs analyze and evaluate reception of the sounding packets, and information is fed back to the transmitting AP. The AP then uses this "channel state information" (CSI) when configuring transmissions to the STAs.

[0005] In some cases, multiple APs may work in cooperation to communicate with one or more STAs in a WLAN. For example, the proposed IEEE 802.11be standard is under development to support next-generation, extremely high throughput (EHT) WLANs. EHT communication may be achieved using AP cooperation, which may utilize coordination between multiple APs and multiple antennas on an AP to minimize interference and improve quality of service for communication with STAs.

[0006] In some cases, multiple APs may cooperate to communicate with one or more STAs to achieve increased or improved throughput. AP cooperation can also help minimize interference and improve quality of service for communications with the STAs.

[0007] However, existing sounding protocols may provide insufficient channel estimation accuracy when AP cooperation is used. Therefore, there is a need for improved methods and apparatus for sounding protocols when access point cooperation is used.

[0008] This background information is provided to identify information believed by the applicant to be of possible relevance to the present invention. No admission is necessarily intended, nor should be construed, that any of the preceding information constitutes prior art against the present invention. Summary of the Invention

[0009] An objective of an embodiment of the present invention is to provide a method and apparatus for a sounding protocol when using AP cooperation. According to an embodiment of the present invention, a method is provided for a STA to determine channel state information (CSI) of a wireless channel. The method includes receiving a plurality of sounding data transmissions from a plurality of APs over a plurality of communication channels, estimating, for each of the communication channels, a channel state information (CSI) of the channel based on the plurality of sounding data transmissions received over each of the communication channels, aggregating the channel information of each of the communication channels to generate an aggregated CSI, and transmitting the aggregated CSI to the plurality of APs.

[0010] According to an embodiment of the present invention, a method for a station (STA) to determine channel state information (CSI) of a wireless channel is provided, the method includes receiving a plurality of sounding data transmissions from a plurality of access points (APs) over a plurality of communication channels, estimating a CSI of the channel based on the plurality of sounding data transmissions for each of the plurality of communication channels, aggregating the plurality of communication channels to generate an aggregated channel having an aggregated channel matrix, transforming the aggregated channel matrix using singular value decomposition to generate Σ and V matrices of the aggregated channel matrix, and transmitting the Σ and V matrices to the plurality of APs.

[0011] In a further embodiment, the multiple sounding data transmissions are received consecutively.

[0012] In any of the above described embodiments, multiple sounding data transmissions are received in parallel.

[0013] In any of the above described embodiments, the aggregated matrix includes the gains and phases of multiple sounding data transmissions.

[0014] In any of the above described embodiments, the multiple communication channels use the 802.11 Wi-Fi protocol.

[0015] In any of the above-described embodiments, the 802.11 protocol includes a multiple-input multiple-output (MIMO) protocol.

[0016] Any of the above-described embodiments may further include determining that joint transmission is to be used by multiple APs over multiple communication channels.

[0017] According to an embodiment of the present invention, a method for an access point (AP) to determine channel state information (CSI) of a wireless channel is provided, the method including: transmitting sounding data transmissions to a plurality of stations (STAs) over a plurality of communication channels, receiving a pair of Σ and V matrices from each of the plurality of STAs in response to the sounding data transmissions, each of the paired Σ and V matrices being generated through singular value decomposition of a matrix of a channel estimated by each of the plurality of STAs, reconstructing an aggregate matrix of CSI based on the pair of Σ and V matrices received from the plurality of STAs, and calculating a precoder matrix based on the aggregate matrix.

[0018] In any of the above described embodiments, the sounding data transmission is transmitted in parallel with multiple sounding data transmissions.

[0019] In any of the above described embodiments, the sounding data transmission is transmitted in series with multiple sounding data transmissions.

[0020] Any of the above-described embodiments may further include the AP communicating with one of the multiple STAs using a precoder matrix with a cooperative beamforming technique.

[0021] Any of the above-described embodiments may further include the AP communicating a portion of the multiple data streams to the multiple STAs using a precoder matrix with a joint transmission technique.

[0022] According to an embodiment of the present invention, a station (STA) for communicating over a communication channel is provided, the station including a processor and a non-transitory memory storing instructions that, when executed by the processor, cause the STA to receive a plurality of sounding data transmissions from a plurality of access points (APs) over the plurality of communication channels, estimate a CSI of the channel based on the plurality of sounding data transmissions for each of the plurality of communication channels, aggregate the plurality of communication channels to generate an aggregated channel having an aggregated channel matrix, transform the aggregated channel matrix using singular value decomposition to generate a Σ matrix and a V matrix of the aggregated channel matrix, and transmit the Σ matrix and the V matrix to the plurality of APs.

[0023] In any of the above described embodiments, the multiple sounding data transmissions are received consecutively.

[0024] In any of the above described embodiments, multiple sounding data transmissions are received in parallel.

[0025] In any of the above described embodiments, the aggregated matrix includes the gains and phases of multiple sounding data transmissions.

[0026] In any of the above described embodiments, the multiple communication channels use the 802.11 Wi-Fi protocol.

[0027] In any of the above-described embodiments, the 802.11 protocol includes a multiple-input multiple-output (MIMO) protocol.

[0028] Any of the above-described embodiments may further include determining that joint transmission is to be used by multiple APs over multiple communication channels.

[0029] The embodiments have been described above in conjunction with the aspects of the invention in which they may be implemented. It will be understood by one of ordinary skill in the art that the embodiments may be implemented in conjunction with the aspects for which they are described, but may also be implemented using other embodiments of the aspects. Where the embodiments are mutually exclusive or otherwise inconsistent with one another, this will be apparent to one of ordinary skill in the art. As will be apparent to one of ordinary skill in the art, some embodiments may be described in the context of one aspect, but may be applicable to other aspects. [Brief description of the drawings]

[0030] Additional features and advantages of the present invention will become apparent from the following detailed description taken in conjunction with the accompanying drawings.

[0031] [Figure 1] 1 illustrates a computing device that may be used in embodiments of the present invention.

[0032] [Diagram 2] 1 illustrates a wireless network in which embodiments of the present invention may be used.

[0033] [Diagram 3] 1 illustrates an embodiment having two APs and two STAs using a coordinated beamforming technique according to an embodiment.

[0034] [Figure 4] 1 illustrates an embodiment having two APs and two STAs using a joint transmission technique according to an embodiment.

[0035] [Diagram 5] 1 illustrates a sequential sounding procedure according to an embodiment.

[0036] [Figure 6] 1 illustrates a first parallel sounding procedure according to an embodiment.

[0037] [Figure 7] 1 illustrates a second parallel sounding protocol according to an embodiment.

[0038] [Figure 8a] 4 illustrates a CSI matrix for channel state information according to an embodiment.

[0039] [Figure 8b] 1 illustrates two aggregated matrices of channel state information according to an embodiment.

[0040] [Figure 9a] 1 illustrates the use of a precoder matrix using the CBF technique, according to one embodiment.

[0041] [Figure 9b] 1 illustrates the use of a precoder matrix using the JT technique, according to one embodiment.

[0042] [Figure 10] 1 illustrates computation and use of a precoder matrix using STA-aggregated CSI information and JT technique according to an embodiment.

[0043] It is to be noted that like features are identified with like reference numerals throughout the accompanying drawings. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0044] It is an object of embodiments of the present invention to provide a method and apparatus for implementing a sounding protocol when using Access Point (AP) cooperation.

[0045] A wireless network typically includes several end-user stations, referred to as STAs, that are wirelessly connected to an Access Point (AP), which provides access to a larger Local Area Network (LAN), Wide Area Network (WAN), the Internet, and any number of other wired and wireless networks as known in the art. In many network topologies, a single AP may serve multiple STAs.

[0046] Examples of STAs include any wireless entity, such as a mobile phone, a tablet, a laptop computer, another AP, a vehicle, a beacon, and so on.

[0047] Some of the most common wireless networks are based on the IEEE 802.11 family of standards that define the protocols used for wireless communication. One of the more recent standards in the family of protocols is 802.11be Very High Throughput (EHT). One of the features of 802.11be is known as multi-access point (AP) cooperation, which allows a STA to connect to multiple APs to optimize the wireless connection for speed, distance, signal-to-noise ratio (SNR), or other factors. Allowing a STA to connect to multiple APs, or an AP to connect to multiple STAs, allows the STA's connection to the wider network through the APs to be optimized using multiple paths.

[0048] Modern wireless STAs and APs also support multiple-input multiple-output (MIMO) technology, where each STA and AP can transmit and receive using multiple transmit and receive antennas. MIMO technology in STAs and APs allows them to use multi-stream transmissions to increase throughput, range, or both throughput and range. An additional benefit of multiple antennas in a MIMO configuration is that further improvements can be achieved by using beamforming to control the direction of wireless transmissions. With MIMO technology, the path between each antenna on the AP and each antenna on the STA can be independently optimized.

[0049] FIG. 1 is a block diagram of a wireless communication device or system 100 that may be used to implement STAs and APs utilizing the methods disclosed herein. Examples include mobile phones, portable computers, tablets, wireless access points, etc. A particular device 100 may utilize all of the components shown or only a subset of these components, and different devices may have different levels of integration. Additionally, a device may include multiple instances of components such as multiple processing units, processors, memory, transmitters, receivers, etc. The device 100 includes a processing unit 110. The processing unit 110 typically includes a processor, also known as a central processing unit (CPU) 110, a bus, and memory 120, and may also optionally include a mass storage device 130, a video adapter 140, and an I / O interface 160 (each shown with dashed lines to indicate options). The device 100 may further include one or more network interfaces 150 that connect the device to a communication network 102, which may be a wired network or a wireless network such as an IEEE 802.11-enabled wireless network. The device 100 may further include one or more wireless access network interfaces 190 that connect the computing system to a cellular network 104, which may be a cellular network such as 3G, 4G, LTE, 5G, etc.

[0050] CPU 110 may include any type of electronic data processor and may include one or more cores or processing elements. Memory 120 may include any type of non-transitory system memory, such as static random access memory (SRAM), dynamic random access memory (DRAM), synchronous DRAM (SDRAM), read-only memory (ROM), or a combination thereof. In an embodiment, memory may include ROM for use during startup and DRAM for program and data storage for use while executing programs. Bus may be one or more of any type of several bus architectures, including a memory bus or memory controller, a peripheral bus, or a video bus.

[0051] Mass storage device 130 may include any type of non-transitory storage device configured to store data, programs, and other information and make the data, programs, and other information accessible via the bus. Mass storage device may include, for example, one or more of a solid state drive, a hard disk drive, a magnetic disk drive, or an optical disk drive.

[0052] Video adapter 140 and I / O interface 160 provide optional interfaces for coupling external input and output devices to the processing unit. Examples of input and output devices include display 170 coupled to video adapter 140 and I / O device 180, such as a touch screen, coupled to I / O interface 1160. Other devices may be coupled to CPU 110 and additional or fewer interfaces may be utilized. For example, a serial interface such as a Universal Serial Bus USB (not shown) may be used to provide an interface for external devices. Alternatively, the computing system may rely on a network interface to connect to available mass storage devices, video adapters, and I / O interfaces available on a network.

[0053] FIG. 2 illustrates an embodiment 200 of a STA wirelessly connecting to the Internet 202 through an AP. L is the scheduled data stream. It will be appreciated that in other embodiments, the Internet 202 may be replaced by any other computer network to which the STAs are configured to connect. APs 204, 206, 208 represent multiple APs providing wireless network access in an area. In general, there may be L APs, where L is a positive integer. Each of the L APs has a MIMO architecture and in particular has several transmit antennas, i.e., N1, N2,..., N, capable of supporting MIMO techniques including beamforming. L200 includes a 100-GHz AP 204, 206, 208, and 100-GHz AP 206. Each of the L APs 204, 206, 208 is directly or indirectly connected to the Internet 202. Three STAs are shown: a laptop computer 210, a tablet 212, and a mobile phone 214. Any number of STAs may be supported in embodiment 200, limited only by the coverage area of ​​the APs and the number of STAs that may affect the responsiveness and throughput capabilities of the APs, which may cause service to the STAs to fall below acceptable limits. The STAs connect to one or more APs to access the Internet.

[0054] Figure 3 shows an embodiment similar to Figure 2, where two APs and two STAs are shown for illustrative purposes. STA1 304 and STA2 306 access AP1 204 and AP2 206 to access the Internet 202. AP1 204 and AP2 206 implement multi-AP cooperation that allows two STAs to connect to either or both APs.

[0055] Multi-AP techniques include techniques known as "cooperative beamforming" (CBF) and "joint transmission" (JT). Using the CBF technique, STA1 304 may be scheduled to communicate with AP1 204, and STA2 306 may be scheduled to communicate with AP2 206. Referring to FIG. 4, using the JT technique, the K1 and K2 data streams are shared between AP1 204 and AP2 206 to jointly communicate with STA1 304 and STA2 306.

[0056] When using multi-AP cooperation and beamforming, a calibration procedure known as "sounding" is used to estimate wireless communication channel state information (CSI) between antennas on the AP and antennas on the STA. The CSI measurements are used to configure beamforming transmissions between the AP and the STA. In some sounding procedures, the AP transmits null data packets (NDPs) to the STAs. Each STA that receives one or more NDP packets analyzes them to calculate or estimate the channel or channel response to generate a feedback matrix for the combined communication between the AP and the STA. In some embodiments, estimating the channel includes measuring the phase and gain of the received one or more NDPs. Sounding adds overhead to the network, but allows for increased network performance that should outweigh the reduced capacity due to the overhead. When using multi-AP cooperation, the CSI calculation is performed by each STA. The CSI information from the STAs is then fed back to each AP. Each AP is responsible for aggregating information received from the STAs to compute a precoder that may be used when multiple APs cooperate to perform joint transmissions (JT) to a STA or to communicate to scheduled STAs using CBF. The precoder is used by the MIMO transmitter to determine the transmission parameters to use for each of the transmitting antennas.

[0057] FIG. 5 illustrates a continuous sounding procedure 500 according to an embodiment. The master AP starts the procedure by sending an NDP announcement (NDPA) frame towards the STA. The master AP is the AP designated to start the sounding procedure. The master AP then sends a first NDP frame (shown as NDP1). After this, other slave APs sequentially send NDP frames towards the STA in succession. In this embodiment shown, slave AP1 sends a second NDP frame, NDP2, and then another slave AP2 sends a third NDP frame, NDP3. The master AP then sends a trigger frame signaling the STA to feed back a CSI beamforming report. Each STA receives the NDP from each AP in turn. Thus, continuous sounding allows each STA to estimate the channel to each AP without being affected by other APs.

[0058] 6 illustrates a first parallel sounding procedure 600 according to an embodiment. The master AP starts the procedure by sending an NDPA frame towards the STA. Then, both the master AP and the slave AP send NDP frames towards the STA simultaneously. Then, the master AP sends a trigger frame to signal the STA to feed back a CSI beamforming report. Additional slave APs may join the sounding procedure by sending their respective NDP frames in parallel with NDP1 and NDP2.

[0059] 7 shows a second parallel sounding procedure 700 according to an embodiment. The master AP starts the procedure by sending a sounding trigger frame towards the STA. Then, both the master AP and the slave AP send NDPA frames towards the STA simultaneously. After this, both the master AP and the slave AP send NDP frames towards the STA simultaneously. Then, the master AP sends a trigger frame signaling the STA to feedback a CSI beamforming report. Additional slave APs may participate in this sounding procedure by sending their respective NDP frames in parallel with NDPA, NDP1, and NDP2.

[0060] Returning to FIG. 3, this figure shows two APs performing multi-AP cooperation with two STAs each. AP1 204 has N1 Tx antennas. AP2 206 has N2 Tx antennas. STA1 304 has M1 Rx antennas. STA2 306 has M2 Rx antennas. During the sounding process, STA1 304 calculates the number of Rx antennas based on the NDP frames received from the transmitters in AP1 204 and AP2 206 for channels 308 and 310.

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[0061] It is impractical for the STA to transmit the raw H matrix back to the AP. In an embodiment, channel information related to the matrix H is calculated using singular value decomposition (SVD) techniques to convert H into the form UΣV H where U is the left eigenmatrix, Σ is the eigenvalue matrix, V H is a right-specific matrix. If H has dimension K×N, then U has dimension K×K, Σ has dimension K×N, and V H has size N×N. For practical purposes, when written in SVD form, we use the ΣV H It is sufficient that only the information is fed back. Σ and V H Given the data, H can then be reconstructed by AP: The superscript H refers to the Hermitian transpose (i.e., conjugate transpose) matrix operation.

[0062] The precoder for an AP can be calculated by the master AP, which can be AP1 204 or AP2 206, or by both AP1 204 and AP2 206. When using multi-AP cooperation, to calculate the precoder for cooperative beamforming (CBF) or joint transmission (JT), four channel conditions are calculated for the actual stream sizes K1 and K2.

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[0063] In an embodiment using coordinated beamforming (CBF) where STA1 304 and STA2 306 are communicating with AP1 204, as shown in FIG.

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[0064] The channel matrix in each AP is not the left eigenmatrix U but the fed back eigenvalue Σ and the right eigenmatrix V H If these CSI values ​​are aggregated (e.g., concatenated into a single H matrix), then U, Σ, and V H are the U, Σ, and V H can be considered to be individually and separately aggregated from U. Since U is a unitary matrix containing phase information, it can be considered as a kind of carrier frequency offset (CFO) and can be ignored without affecting the overall multi-user MIMO (MU-MIMO) performance of the CB. In other embodiments, the same principle can be applied to single AP-based downlink MU-MIMO.

[0065] In embodiments using joint transmission (JT), the channels that are aggregated are not limited to columns in matrix 800, but are also aggregated by rows of matrix 800. In these embodiments, the U matrix is ​​not ignored when channels are aggregated into rows of matrix 800. That is,

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[0066] In an embodiment, CSI information for each channel may be transmitted separately between each STA and each AP when using CBF-based multi-AP cooperation or single AP-based DL MU-MIMO. However, in an embodiment using JT-based multi-AP cooperation, each STA must first aggregate the channels between itself and the APs with which it cooperates before calculating the SVD and calculating the CSI information. In the sounding procedures shown in Figures 5, 6, and 7 and other suitable methods, each STA must aggregate the estimated channels between itself and all APs in the multi-AP cooperation. The STA may then calculate the SVD of the aggregated channels to calculate the CSI information to feed back to the AP.

[0067] Referring to Fig. 3, STA1 304 and STA2 306 should aggregate the estimated channel similar to the matrix 802 in Fig. 8b. Here, before each STA calculates the CSI information for feedback,

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[0068] 10, in matrix 802, the superscript x represents the STA index. x is the estimated channel, estimated and aggregated at STAx. The subscript is the size of the channel. The general inverse of the matrix 802 is used to calculate the zero-forcing beamforming (ZFBF) based precoder matrix 1002 in the master AP.

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[0069] In an embodiment of the present invention, a STA performs channel aggregation before computing singular value decomposition matrices Σ and V. The singular value decomposition matrices Σ and V are then fed back by the STA to one or more APs. This approach is performed particularly when joint transmission (rather than cooperative beamforming) is implemented by the APs for communication. In some embodiments, the STA is configured to determine whether joint transmission is implemented for communication. If joint transmission is implemented by multiple APs together, the STA is further configured to perform channel aggregation before computing and feeding back the singular value decomposition matrices Σ and V. That is, the estimated channels between the STA and all APs working together in cooperative mode may be aggregated to each STA before CSI is fed back in case of a joint transmission (JT) schedule. The STA thus estimates the channels between itself and all cooperating APs in combination. Then, SVD is performed on this aggregated channel. If joint transmission is not implemented (e.g., cooperative beamforming is implemented), the STA is configured to perform a different procedure. For example, the STA may be configured to compute and feed back the singular value decomposition matrices without channel aggregation. That is, the estimated channel between each STA and each AP may be fed back to each STA without aggregation in the case of a coordinated beamforming schedule.

[0070] In the case of joint transmission, the aggregated channel matrix can be expressed as:

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[0071] Here, a and b refer to different channels.

[0072] In various embodiments, the channels between one AP in cooperation mode and all scheduled STAs in the AP cooperation may be reconstructed jointly by the AP to compute the ZFBF-based precoder computation for the cooperative beamforming (CB) schedule.

[0073] In various embodiments, all channels between all APs and all scheduled STAs in cooperative mode may be reconstructed together at the AP to calculate a joint transmission (JT) schedule.

[0074] According to an embodiment of the present invention, a method for a STA to determine channel state information (CSI) for a wireless channel is provided, the method includes receiving a plurality of sounding data transmissions from a plurality of APs over a plurality of communication channels, estimating, for each of the communication channels, channel state information (CSI) for the channel based on the plurality of sounding data transmissions received over each of the communication channels, aggregating the channel information for each of the communication channels to generate an aggregated CSI, and transmitting the aggregated CSI to the plurality of APs.

[0075] As used herein, the term "about" should be interpreted to include variations from the nominal value, for example, a variation of + / - 10% from the nominal value. It should be understood that such variations are always included in a given value provided herein, whether or not it is specifically referred to.

[0076] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs.

[0077] Through the description of the foregoing embodiments, the present invention may be implemented by using only hardware, or by using software and a required universal hardware platform. Based on such understanding, the technical solution of the present invention may be embodied in the form of a software product. The software product may be stored in a non-volatile or non-transitory storage medium, which may be a compact disc read-only memory (CD-ROM), a USB flash disk, or a removable hard disk. The software product includes some instructions that enable a computer device (personal computer, server, or network device) to execute the method provided in the embodiments of the present invention. For example, such execution may correspond to simulating a logical operation as described herein. The software product may additionally or alternatively include some instructions that enable a computer device to execute an operation for configuring or programming a digital logic device according to the embodiments of the present invention.

[0078] While the invention has been described with reference to specific features and embodiments thereof, it is apparent that various modifications and combinations can be made without departing from the invention. Accordingly, the specification and drawings should be regarded merely as illustrative of the invention as defined in the appended claims, and it is intended to cover any and all modifications, variations, combinations, or equivalents that are within the scope of the invention. (Other possible items) (Item 1) 1. A method for a station (STA) to determine channel state information (CSI) of a wireless channel, comprising: receiving a plurality of sounding data transmissions from a plurality of access points (APs) over a plurality of communication channels; estimating, for each of the plurality of communication channels, a CSI for the channel based on the plurality of sounding data transmissions; aggregating the plurality of communication channels to generate an aggregated channel having an aggregated channel matrix; performing a singular value decomposition on the aggregated channel matrix to generate a Σ matrix and a V matrix for the aggregated channel; transmitting the Σ matrix and the V matrix to the plurality of APs; A method comprising: (Item 2) 2. The method of claim 1, wherein the multiple sounding data transmissions are received consecutively. (Item 3) 2. The method of claim 1, wherein the multiple sounding data transmissions are received in parallel. (Item 4) 4. The method of any one of claims 1 to 3, wherein the aggregated channel matrix includes gains and phases of the multiple sounding data transmissions. (Item 5) 5. The method according to any one of claims 1 to 4, wherein the multiple communication channels use the 802.11 Wi-Fi protocol. (Item 6) 6. The method of claim 5, wherein the 802.11 Wi-Fi protocol includes a multiple-input multiple-output (MIMO) protocol. (Item 7) 7. The method according to any one of claims 1 to 6, further comprising determining that joint transmission is used by the multiple APs over the multiple communication channels. (Item 8) 1. A method for an access point (AP) to determine channel state information (CSI) of a wireless channel, comprising: transmitting a sounding data transmission to a plurality of stations (STAs) over a plurality of communication channels; receiving a pair of Σ and V matrices from each of the plurality of STAs in response to the sounding data transmission, each of the paired Σ and V matrices being generated through singular value decomposition of a matrix of a channel estimated by each of the plurality of STAs; reconstructing the aggregate CSI matrix based on pairs of the Σ matrix and the V matrix received from the multiple STAs; calculating a precoder matrix based on the aggregate matrix; A method comprising: (Item 9) 9. The method of claim 8, wherein the sounding data transmission is transmitted in parallel with a plurality of sounding data transmissions. (Item 10) 9. The method of claim 8, wherein the sounding data transmission is transmitted in series with a plurality of sounding data transmissions. (Item 11) 11. The method according to any one of claims 8 to 10, further comprising the step of the AP communicating with one of the plurality of STAs using the precoder matrix with a cooperative beamforming technique. (Item 12) 12. The method according to any one of claims 8 to 11, further comprising the AP communicating a portion of a plurality of data streams to the plurality of STAs using the precoder matrix with a joint transmission technique. (Item 13) A station (STA) communicating over a communication channel, the STA comprising: a processor and a non-transitory memory storing instructions, the instructions, when executed by the processor, causing the STA to: receiving a plurality of sounding data transmissions from a plurality of access points (APs) over a plurality of communication channels; estimating a CSI for each of the plurality of communication channels based on the plurality of sounding data transmissions; aggregating the plurality of communication channels to generate an aggregated channel having an aggregated channel matrix; performing a singular value decomposition on the aggregated channel matrix to generate a Σ matrix and a V matrix for the aggregated channel; transmitting the Σ matrix and the V matrix of the aggregated channels to the plurality of APs; Execute the station. (Item 14) Item 14. The station of item 13, wherein the multiple sounding data transmissions are received consecutively. (Item 15) Item 14. The station of item 13, wherein the multiple sounding data transmissions are received in parallel. (Item 16) 16. The station of any one of claims 13 to 15, wherein the aggregated matrix includes gains and phases of the multiple sounding data transmissions. (Item 17) 17. The station according to any one of claims 13 to 16, wherein the multiple communication channels use the 802.11 Wi-Fi protocol. (Item 18) 18. The station of claim 17, wherein the 802.11 Wi-Fi protocol includes a multiple-input multiple-output (MIMO) protocol. (Item 19) 19. The station according to any one of claims 13 to 18, further comprising a step of determining that joint transmission is used by the multiple APs over the multiple communication channels.

Claims

1. 1. A method for a station (STA) to determine channel state information (CSI) of a wireless channel, comprising: receiving a plurality of sounding data transmissions from a plurality of access points (APs) over a plurality of communication channels; estimating a CSI for each of the plurality of communication channels based on the plurality of sounding data transmissions; aggregating the plurality of communication channels to generate an aggregated channel having an aggregated channel matrix; performing a singular value decomposition on the aggregated channel matrix to generate a Σ matrix and a V matrix for the aggregated channel; transmitting the Σ matrix and the V matrix to the plurality of APs; Equipped with The method, wherein transmitting the Σ matrix and the V matrix to the multiple APs includes transmitting only the Σ matrix and the V matrix to the multiple APs, without the unitary matrix U obtained by the singular value decomposition.

2. The method of claim 1 , wherein the multiple sounding data transmissions are received consecutively.

3. The method of claim 1 , wherein the multiple sounding data transmissions are received in parallel.

4. The method of claim 1 , wherein the aggregated channel matrix includes gains and phases of the multiple sounding data transmissions.

5. The method of any one of claims 1 to 4, wherein the multiple communication channels use the 802.11 Wi-Fi protocol.

6. The method of claim 5, wherein the 802.11 Wi-Fi protocol includes a multiple-input multiple-output (MIMO) protocol.

7. The method of claim 1 , further comprising determining that joint transmissions are to be used by the multiple APs over the multiple communication channels.

8. A computer program product causing a processor of the STA to carry out the method according to any one of claims 1 to 7.

9. 1. A method for an access point (AP) to determine channel state information (CSI) of a wireless channel, comprising: transmitting a sounding data transmission to a plurality of stations (STAs) over a plurality of communication channels; receiving a pair of Σ and V matrices from each of the plurality of STAs in response to the sounding data transmission, each of the paired Σ and V matrices being generated through singular value decomposition of a matrix of a channel estimated by each of the plurality of STAs; reconstructing the aggregate matrix of the CSI based on pairs of the Σ matrix and the V matrix received from the multiple STAs; calculating a precoder matrix based on the aggregate matrix; Equipped with The method, wherein the step of reconstructing the aggregated CSI matrix based on pairs of the Σ matrix and the V matrix received from the multiple STAs includes the step of reconstructing the aggregated CSI matrix based only on pairs of the Σ matrix and the V matrix received from the multiple STAs.

10. The method of claim 9 , wherein the sounding data transmission is transmitted in parallel with a plurality of sounding data transmissions.

11. The method of claim 9 , wherein the sounding data transmission is transmitted in series with a plurality of sounding data transmissions.

12. The method of claim 9 , further comprising the AP communicating with one of the plurality of STAs using the precoder matrix with a cooperative beamforming technique.

13. The method of claim 9 , further comprising the AP communicating a portion of multiple data streams to the multiple STAs using the precoder matrix with a joint transmission technique.

14. A computer program product for causing a processor of the AP to execute the method according to any one of claims 9 to 13.

15. A station (STA) communicating over a communication channel, the STA comprising: a processor and a non-transitory memory storing instructions that, when executed by the processor, cause the STA to: receiving a plurality of sounding data transmissions from a plurality of access points (APs) over a plurality of communication channels; estimating a CSI for each of the plurality of communication channels based on the plurality of sounding data transmissions; aggregating the plurality of communication channels to generate an aggregated channel having an aggregated channel matrix; performing a singular value decomposition on the aggregated channel matrix to generate a Σ matrix and a V matrix for the aggregated channel; transmitting the Σ matrix and the V matrix of the aggregated channels to the plurality of APs; Run the command, A station, wherein transmitting the Σ matrix and the V matrix to the multiple APs includes transmitting only the Σ matrix and the V matrix to the multiple APs, without the unitary matrix U obtained by the singular value decomposition.

16. The station of claim 15, wherein the plurality of sounding data transmissions are received consecutively.

17. The station of claim 15, wherein the multiple sounding data transmissions are received in parallel.

18. 18. A station according to any one of claims 15 to 17, wherein the aggregated channel matrix includes gains and phases of the multiple sounding data transmissions.

19. A station according to any one of claims 15 to 18, wherein said multiple communication channels use the 802.11 Wi-Fi protocol.

20. 20. The station of claim 19, wherein the 802.11 Wi-Fi protocol includes a multiple-input multiple-output (MIMO) protocol.

21. The station of claim 15 , further comprising: determining that joint transmissions are to be used by the multiple APs over the multiple communication channels.

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