# US 7,746,943 B2 · Wireless communication system, wireless communication apparatus and wireless communication method

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- Number: US 7,746,943 B2
- Document ID: US7746943B2
- Status: Granted
- Kind: B2
- Application number: 11/790,592
- Filed: 2007-04-26
- Published: 2007-11-08
- Granted: 2010-06-29
- Earliest claimed: 2006-04-27
- Assignees: Sony Corporation
- Inventors: Tomoya Yamaura
- Web page: https://patentgrep.com/patent/US7746943B2

## CPC

- H04B 7/0408: using two or more beams, i.e. beam diversity
- H04L 25/03343: {Arrangements at the transmitter end}
- H04B 7/0421: {utilizing implicit feedback, e.g. steered pilot signals}
- H04B 7/0634: {Antenna weights or vector/matrix coefficients}
- H04B 7/0697: {using spatial multiplexing}
- H04L 25/0248: {Eigen-space methods}
- H04L 2025/03414: {Multicarrier}
- H04L 2025/03426: {transmission using multiple-input and multiple-output channels}
- H04L 2025/0377: {during the reception of training signals}
- H04L 2025/03796: {Location of reference signals}
- H04B: TRANSMISSION
- H04L: TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION (arrangements common to telegraphic and telephonic communication H04M)

## Abstract

A wireless communication system which performs data transmission from a first terminal including N antennas to a second terminal including M antennas using spatially multiplexed streams (N and M are integers larger than or equal to 2 and N<M) is disclosed. The system includes training request means, training means, channel matrix preparing means, transmission weight matrix computation means, and beamforming means.

## Claims

### Claim 1

A wireless communication system which performs data transmission from a first terminal including N antennas to a second terminal including M antennas using spatially multiplexed streams (N is an integer of 2 or more and M is an integer of 1 or more), the system comprising:
training request means for requesting transmission of a training signal for exciting a backward channel from the first terminal to the second terminal;
training means for transmitting a packet including training series for exciting an N×M backward channel matrix from the second terminal to the first terminal in response to the request;
channel matrix preparing means for dividing the training series received by the antennas of the first terminal and constructing the backward channel matrix;
transmission weight matrix computation means for obtaining a N×N transmission weight matrix for beamforming at the time of forward data transmission using an N×N channel matrix composed of N columns included in the backward channel matrix in consideration of the number N of antennas of the first terminal, in a case of N<M; and
beamforming means for performing beamforming in transmission signals from the antennas of the first terminal using the transmission weight matrix for beamforming when a data packet is transmitted from the first terminal to the second terminal.

### Claim 2 (depends on 1)

The wireless communication system according to claim 1,
wherein the training request means allows the first terminal to request the training series by a TRQ bit included in a link adaptation control field of a HT control field of an MAC frame,
wherein the training means transmits a sounding packet including the training series for exciting the backward channel matrix, and
wherein the transmission weight computation means divides a spatial stream training of the sounding packet received by the first terminal and constructs the backward channel matrix from the divided training series.

### Claim 3 (depends on 2)

The wireless communication system according to claim 2, wherein the training means performs feedback of the sounding packet from the second terminal by a staggered format for temporally dividing a training signal part used for a space division process of a data part and the training signal for exciting a channel of a spatial dimension larger than or equal to the number of streams of data.

### Claim 4 (depends on 3)

The wireless communication system according to claim 3,
wherein the training request means transmits a wireless communication signal for requesting the transmission of the training signal with a format having N data streams from the first terminal to the second terminal, and
wherein the training means feeds back the sounding packet which excites the channel of N spatial dimensions in the training signal part used for the space division process of the data part and allows the training signal for exciting the channel of N-M remaining spatial dimensions to be unrelated to the space division of the signal from the second terminal to the first terminal.

### Claim 5 (depends on 3)

The wireless communication system according to claim 3, wherein the channel matrix preparing means excites the channel of N spatial dimensions in the training signal part used for the space division process of the data part to estimate the N×N channel matrix, but does not process the training signal for exciting the channel of N-M remaining spatial dimensions, when the first terminal receives the sounding packet.

### Claim 6

A wireless communication apparatus which includes N antennas and performs data transmission using spatially multiplexed streams to a second terminal including M antennas (N is an integer of 2 or more and M is an integer of 1 or more), the apparatus comprising:
training request means, for requesting the second terminal to transmit a training signal for exciting a backward channel;
channel matrix preparing means for dividing training series of the antennas for receiving a packet including the training series transmitted from the second terminal into streams and constructing the backward channel matrix in response to the request;
transmission weight matrix computation means for obtaining an N×N transmission weight matrix for beamforming at the time of forward data transmission using an N×N channel matrix composed of N columns included in the backward channel matrix in consideration of the number N of its own antennas, in a case of N<M; and
beamforming means for performing beamforming in transmission signals from the antennas using the transmission weight matrix for beamforming when a data packet is transmitted to the second terminal.

### Claim 7 (depends on 6)

The wireless communication apparatus according to claim 6,
wherein the training request means allows the first terminal to request the training series by a TRQ bit included in a link adaptation control field of a HT control field of an MAC frame, and
wherein the channel matrix preparing means divides a spatial stream training of a sounding packet received by the antennas and constructs the backward channel matrix from the divided training series.

### Claim 8 (depends on 7)

The wireless communication apparatus according to claim 7, wherein the channel matrix preparing means prepares a channel matrix from the sounding packet of a staggered format for temporally dividing a training signal part used for a space division process of a data part and the training signal for exciting a channel of a spatial dimension larger than or equal to the number of streams of data.

### Claim 9 (depends on 8)

The wireless communication apparatus according to claim 8, wherein the training request means transmits a wireless communication signal for requesting the transmission of the training signal with a format having N data streams, and requests the second terminal to feed back the sounding packet which excites the channel of N spatial dimensions in the training signal part used for the space division process of the data part and allows the training signal for exciting the channel of N-M remaining spatial dimensions to be unrelated to the space division of the signal from the second terminal to the first terminal.

### Claim 10 (depends on 9)

The wireless communication apparatus according to claim 9, wherein the channel matrix preparing means excites the channel of N spatial dimensions in the training signal part used for the space division process of the data part to estimate the N×N channel matrix, but does not process the training signal for exciting the channel of N-M remaining spatial dimensions, in the received sounding packet.

### Claim 11

A wireless communication method in a wireless communication apparatus which includes N antennas and performs data transmission using spatially multiplexed streams to a second terminal including M antennas (N is an integer of 2 or more and M is an integer of 1 or more), the method comprising the steps of:
requesting the second terminal to transmit a training signal for exciting a backward channel;
dividing training series of the antennas for receiving a packet including the training series transmitted from the second terminal into streams and constructing the backward channel matrix in response to the request;
obtaining an N×N transmission weight matrix for beamforming at the time of forward data transmission using an N×N channel matrix composed of N columns included in the backward channel matrix in consideration of the number N of its own antennas, in a case of N<M; and
performing beamforming in transmission signals from the antennas using the transmission weight matrix for beamforming when a data packet is transmitted to the second terminal.

### Claim 12

A wireless communication system which performs data transmission from a first terminal including N antennas to a second terminal including M antennas using spatially multiplexed streams (N is an integer of 2 or more and M is an integer of 1 or more), the system comprising:
a training request unit which requests transmission of a training signal for exciting a backward channel from the first terminal to the second terminal;
a training unit which transmits a packet including training series for exciting an N×M backward channel matrix from the second terminal to the first terminal in response to the request;
a channel matrix preparing unit which divides the training series received by the antennas of the first terminal and constructs the backward channel matrix;
a transmission weight matrix computation unit which obtains a N×N transmission weight matrix for beamforming at the time of forward data transmission using an N×N channel matrix composed of N columns included in the backward channel matrix in consideration of the number N of antennas of the first terminal, in a case of N<M; and
a beamforming unit which performs beamforming in transmission signals from the antennas of the first terminal using the transmission weight matrix for beamforming when a data packet is transmitted from the first terminal to the second terminal.

### Claim 13

A wireless communication apparatus which includes N antennas and performs data transmission using spatially multiplexed streams to a second terminal including M antennas (N is an integer of 2 or more and M is an integer of 1 or more), the apparatus comprising:
a training request unit which requests the second terminal to transmit a training signal for exciting a backward channel;
a channel matrix preparing unit which divides training series of the antennas for receiving a packet including the training series transmitted from the second terminal into streams and constructs the backward channel matrix in response to the request;
a transmission weight matrix computation unit which obtains an N×N transmission weight matrix for beamforming at the time of forward data transmission using an N×N channel matrix composed of N columns included in the backward channel matrix in consideration of the number N of its own antennas, in a case of N<M; and
a beamforming unit which performs beamforming in transmission signals from the antennas using the transmission weight matrix for beamforming when a data packet is transmitted to the second terminal.