System, method, apparatus, and computer program for wireless communication

• US 20050249151A1
• Filed: 12/01/2004
• Published: 11/10/2005
• Est. Priority Date: 05/10/2004
• Status: Active Grant

• Current Assignee: Redwood Technologies, LLC (Dominion Harbor Enterprises, LLC)
• Original Assignee: Sony Corporation (Sony Group Corp.)
• Inventors: Takano, Hiroaki
• Granted Patent: US 7,620,114 B2
• Time in Patent Office: Days
• US Class Current: 370/328
• CPC Class Codes: H04B 7/0413 MIMO systems
• CPC Class Codes: H04B 7/0615 of weighted versions of same signal
• CPC Class Codes: H04B 7/0697 using spatial multiplexing
• CPC Class Codes: H04B 7/0848 Joint weighting

Abstract

The disclosed invention implements SVD-MIMO communication efficiently with a less number of high-load calculation required for singular value decomposition (SVD) processing for a channel matrix. A receiver derives a channel matrix H from a reference signal from a transmitter and acquires downlink transmit weights V and receive weights U^H by SVD of the channel matrix H. The receiver transmits a reference signal weighted with U* to the transmitter, where U* is a conjugate matrix for U as uplink transmit weights. The transmitter receives the reference signal weighted with U* and separates the signal into downlink transmit weights V and a diagonal matrix D, based on unitary matrix properties.

Claims

1. A wireless communication system which carries out spatial multiplexing transmission with transmit and receive weights determined by utilizing a channel matrix with elements that are pairs of transmit antennas and receive antennas,

wherein, in an instance where data transmission from a first communication device to a second communication device is performed,

wherein said second communication device transmits a reference signal weighted with transmit weights in a direction from the second communication device to the first communication device;

and

wherein said first communication device separates the reference signal received into transmit weights in a direction from the first communication device to the second communication device and a diagonal matrix and transmits data with the thus obtained transmit weights.

2. The wireless communication system according to claim 1, which carries out spatial multiplexing transmission with transmit and receive weights determined by utilizing a matrix UDV^H obtained by singular value decomposition of a channel matrix H with elements that are pairs of transmit antennas and receive antennas,

wherein said second communication device acquires a channel matrix H, using a reference signal from said first communication device, acquires transmit weights V in the direction from the first communication device as a transmitter to the second communication device as a receiver and receive weights U^H by singular value decomposition of the channel matrix H, transmits a reference signal weighted with U* to the first communication device, where U* is a conjugate matrix for U as transmit weights in the direction from the second communication device to the first communication device, and

wherein said first communication device, upon receiving the reference signal weighted with U*, separates the received signal into transmit weights V in the direction from the first communication device to the second communication device and a diagonal matrix D by suitably using unitary matrix properties.

3. The wireless communication system according to claim 2, wherein said first communication device acquires H^TU*=V*DU^T=V*D by receiving the reference signal weighted with U* in the direction from the second communication device to the first communication device, the channel matrix in this direction being a transposed matrix H^T for the channel matrix H (=UDV^H) in the direction from the first communication device to the second communication device, and separates the transmit weights V in the direction from the second communication device to the first communication device from V*D, based on the unitary matrix properties.

4. A wireless communication apparatus which carries out spatial multiplexing transmission with transmit and receive weights determined by utilizing a matrix UDV^H obtained by singular value decomposition of a channel matrix H with elements that are pairs of transmit antennas and receive antennas, said wireless communication apparatus comprising:

in an instance where data communication from another end in a direction from a first communication device to a second communication device is performed,

a channel matrix acquisition unit which acquires a channel matrix H in a direction from the first communication device to the second communication device, based on a reference signal received from another end;

a singular value decomposition unit which executes singular value decomposition of the acquired channel matrix into UDV^H;

a receiving section which receives user data transmitted in a forward direction from the other end and weights the user data with receive weights UH derived from the acquired channel matrix H through the singular value decomposition; and

a transmitting section which weights a reference signal with transmit weights in a reverse direction to the other end by using a conjugate matrix U* for U obtained, based on a result of the singular value decomposition of the acquired channel matrix H, as the transmit weights, and transmits the reference signal.

5. A wireless communication apparatus which carries out spatial multiplexing transmission with transmit and receive weights determined by utilizing a channel matrix with elements that are pairs of transmit antennas and receive antennas, said wireless communication apparatus comprising:

a receiving section which receives a reference signal weighted with transmit weights;

a separator which separates the received signal into transmit weights V in a reverse direction and a diagonal matrix D; and

a transmitting section which transmits data weighted with the transmit weights obtained by said separator in the reverse direction to the direction in which said reference signal was received.

6. The wireless communication apparatus according to claim 5, in an instance where data communication to another end in a direction from a first communication device to a second communication device is performed,

wherein said receiving section receives a reference signal weighted with U* which is a conjugate matrix for U as transmit weights in a direction from the second communication device to the first communication device,

wherein said separator separates the received signal into transmit weights V in the direction from the first communication device to the second communication device and a diagonal matrix D, and

wherein said transmitting section transmits data weighted with V in the direction from the first communication device to the second communication device.

7. The wireless communication apparatus according to claim 6,

wherein the channel matrix in the direction from the second communication device to the first communication device is a transposed matrix H^T for the channel matrix H (=UDV^H) in the direction from the first communication device to the second communication device,

wherein said receiving section acquires H^TU*=V*DU^T=V*D by receiving the reference signal weighted with U* in the direction from the second communication device to the first communication device, and

wherein said separator separates the transmit weights V in the direction from the first communication device to the second communication device from V*D, based on unitary matrix properties.

8. A wireless communication method for carrying out spatial multiplexing transmission with transmit and receive weights determined by utilizing a matrix UDV^H obtained by singular value decomposition of a channel matrix H with elements that are pairs of transmit antennas and receive antennas, said wireless communication method comprising the steps of:

in an instance where data communication from another end in a direction from a first communication device to a second communication device is performed,

acquiring a channel matrix H in the direction from the first communication device to the second communication device, based on a reference signal received from the other end;

executing singular value decomposition of the acquired channel matrix H into UDV^H;

receiving user data transmitted in a forward direction from the other end and weighting the user data with receive weights U^H derived from the acquired channel matrix H by the singular value decomposition; and

weighting a reference signal with transmit weights in a reverse direction to the other end by using a conjugate matrix U* for U obtained, based on a result of the singular value decomposition of the acquired channel matrix H, as the transmit weights, and transmitting the reference signal.

9. A wireless communication method for carrying out spatial multiplexing transmission with transmit and receive weights determined by utilizing a matrix UDV^H obtained by singular value decomposition of a channel matrix H with elements that are pairs of transmit antennas and receive antennas, said wireless communication method comprising the steps of:

in an instance where data communication to another end in a direction from a first communication device to a second communication device is performed,

receiving a reference signal weighted with a conjugate matrix U* for U as transmit weights in a direction from the second communication device to the first communication device and acquiring H^TU*=V*DU^T=V*D;

separating transmit weights V in the direction from the first communication device to the second communication device from V*D, based on unitary matrix properties; and

weighting data with the transmit weights V in the direction from the first communication device to the second communication device and transmitting the data.

10. A computer program coded in a computer readable form to perform a process on a computer system for carrying out spatial multiplexing transmission with transmit and receive weights determined by utilizing a matrix UDV^H obtained by singular value decomposition of a channel matrix H with elements that are pairs of transmit antennas and receive antennas, said computer program comprising the steps of:

in an instance where data communication from another end in a direction from a first communication device to a second communication device is performed,

acquiring a channel matrix H in the direction from the first communication device to the second communication device, based on a reference signal received from the other end;

executing singular value decomposition of the acquired channel matrix H into UDV^H;

receiving user data transmitted in a forward direction from the other end and weighting the user data with receive weights U^H derived from the acquired channel matrix H by the singular value decomposition; and

weighting a reference signal with transmit weights in a reverse direction to the other end by using a conjugate matrix U* for U obtained, based on a result of the singular value decomposition of the acquired channel matrix H, as the transmit weights, and transmitting the reference signal.

11. A computer program coded in a computer readable form to perform a process on a computer system for carrying out spatial multiplexing transmission with transmit and receive weights determined by utilizing a matrix UDV^H obtained by singular value decomposition of a channel matrix H with elements that are pairs of transmit antennas and receive antennas, said computer program comprising the steps of:

in an instance where data communication to another end in a direction from a first communication device to a second communication device is performed,

receiving a reference signal weighted with a conjugate matrix U* for U as transmit weights in a direction from the second communication device to the first communication device and acquiring H^TU*=V*DU^T=V*D;

separating transmit weights V in the direction from the first communication device to the second communication device from V*D, based on unitary matrix properties; and

weighting data with the transmit weights V in the direction from the first communication device to the second communication device and transmitting the data.