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

• US 7,620,114 B2
• Filed: 12/01/2004
• Issued: 11/17/2009
• 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
• Primary Examiner(s): TSE, YOUNG TOI
• Application Number:
  US11/000,192
• Publication Number:
  US 20050249151A1
• Time in Patent Office: 1,812 Days
• Field of Search: 375/134, 375/145, 375/149, 375/260, 375/267, 370/208, 370/210
• US Class Current: 375/267
• 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,

the system comprising:

a first communication device including a transmit weight separator;

a second communication device configured to weight a reference signal with a first weight matrix U* to produce a weighted reference signal and transmit the weighted reference signal to the first communication device, the first weight matrix U* including a conjugate matrix of a second weight matrix U and produce the first weight matrix U* based on singular value decomposition of the channel matrix H in a direction from the first communication device to the second communication device;

the transmit weight separator is configured to receive the weighted reference signal from the second communication device and separate the weighted reference signal into a third weight matrix V and a diagonal matrix D; and

the first communication device is further configured to weight data with the third weight matrix V to produce weighted data and transmit the weighted data to the second communication device.

2. The wireless communication system according to claim 1, which carries out the spatial multiplexing transmission with the transmit and receive weights determined by utilizing a matrix UDV^H obtained by the singular value decomposition of the channel matrix H with elements that are pairs of the transmit antennas and the receive antennas, wherein U is the second weight matrix, D is the diagonal matrix, and V^H is a conjugate transposed matrix of the third of a third weight matrix V,

wherein said second communication device acquires the channel matrix H, using a reference signal from said first communication device, acquires the third weight matrix V in the direction from the first communication device as a transmitter to the second communication device as a receiver, receives the receive weights U^H by the singular value decomposition of the channel matrix H, and transmits the reference signal weighted with U* to the first communication device, where U* is the conjugate matrix for U as the receive 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 the third weight matrix V in the direction from the first communication device to the second communication device and the 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, wherein H^T is a transposed matrix of the channel matrix H, and U^T is a transposed matrix of the second weight matrix U, by receiving the reference signal weighted with U* in the direction from the second communication device to the first communication device, the channel matrix H in this direction being the 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 third weight matrix 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, wherein U is a second weight matrix, D is a diagonal matrix, and V^H is a transposed matrix of a third weight matrix V. said wireless communication apparatus comprising:

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

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

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

a transmitting section which weights a reference signal with the third weight matrix V 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 with the transmit weights.

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 a first weight matrix U* including a conjugate matrix of a second weight matrix U and produces the first weight matrix U* on singular value decomposition of the channel matrix H;

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

a transmitting section which transmits data weighted with the third weight matrix V 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 the reference signal weighted with the first weight matrix U* which is the conjugate matrix for U as the receive weights in a direction from the second communication device to the first communication device;

said separator separates the received signal into the third weight matrix V in the direction from the first communication device to the second communication device and the diagonal matrix D; and

said transmitting section transmits the data weighted with the third weight matrix V as the transmit weights 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 H 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 V^H is a transposed matrix of the third weight matrix V;

said receiving section acquires H^TU*=V*DU^T=V*D, wherein H^T is the transposed matrix of the channel matrix H, and U^T is a transposed matrix of the second weight matrix U, by receiving the reference signal weighted with U* in the direction from the second communication device to the first communication device; and

said separator separates the transmit weights 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, wherein U is a second weight matrix, D is a diagonal matrix, and V^H is a transpose matrix of a third weight matrix V, said wireless communication method comprising the steps of:

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

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

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

weighting a reference signal with the third weight matrix V 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 with the transmit weights.

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, wherein U is a second weight matrix, D is a diagonal matrix, and V^H is a transposed matrix of a third weight matrix V, said wireless communication method comprising the steps of:

receiving a reference signal weighted with a conjugate matrix U* for U as the receive weights in a direction from a second communication device to a first communication device and acquiring H^TU*=V*DU^TV*D, wherein H^T is a transposed matrix of the channel matrix H, and U^T is a transposed matrix of the second weight matrix U;

separating the third weight matrix V as the transmit weights in a 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 in the direction from the first communication device to the second communication device and transmitting the data.

10. A computer readable medium embodying a program of instructions executable by a computer to perform a method of 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, wherein U is a second weight matrix, D is a diagonal matrix, and V^H is a transposed matrix of a third weight matrix V, said method comprising the steps of:

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

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

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

weighting a reference signal with the third weight matrix V 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 with the transmit weights.

11. A computer readable medium embodying a program of instructions executable by a computer to perform a method of 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, wherein U is a second weight matrix, D is a diagonal matrix, and V^H is a transposed matrix of a third weight matrix V, said method comprising the steps of:

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

separating the third weight matrix V as the transmit weights in a 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 in the direction from the first communication device to the second communication device and transmitting the data.