Wireless communications system, wireless communications apparatus, wireless communications method and computer program for wireless communication

• US 20050094741A1
• Filed: 08/23/2004
• Published: 05/05/2005
• Est. Priority Date: 11/05/2003
• Status: Active Grant

• Current Assignee: Sony Corporation (Sony Group Corp.)
• Original Assignee: Sony Corporation (Sony Group Corp.)
• Inventors: Kuroda, Shinichi
• Granted Patent: US 7,474,641 B2
• Time in Patent Office: Days
• US Class Current: 375/267
• CPC Class Codes: H04B 7/0413 MIMO systems
• CPC Class Codes: H04B 7/0421 utilizing implicit feedback, e.g. steered pilot signals
• CPC Class Codes: H04B 7/0456 Selection of precoding matrices or codebooks, e.g. using matrices antenna weighting
• CPC Class Codes: H04B 7/06 at the transmitting station
• CPC Class Codes: H04B 7/0619 using feedback from receiving side feedback signaling for adaptive modulation/coding H04L1/0001
• CPC Class Codes: H04B 7/0665 Feed forward of transmit weights to the receiver
• CPC Class Codes: H04B 7/0854 using error minimizing algorithms, e.g. minimum mean squared error [MMSE], "cross-correlation" or matrix inversion
• CPC Class Codes: H04B 7/0862 receiver computing weights based on information from the transmitter
• CPC Class Codes: H04L 1/0656 Cyclotomic systems, e.g. Bell Labs Layered Space-Time [BLAST]
• CPC Class Codes: H04L 2025/0377 during the reception of training signals
• CPC Class Codes: H04L 25/0202 Channel estimation
• CPC Class Codes: H04L 25/0224 using sounding signals
• CPC Class Codes: H04L 27/12 Modulator circuits; Transmitter circuits
• CPC Class Codes: H04L 27/2601 Multicarrier modulation systems
• CPC Class Codes: H04W 72/20 Control channels or signalling for resource management

Abstract

In performing SVD-MIMO transmission, a set-up procedure is simplified while assuring a satisfactory decoding capability with a reduced number of antennas. A transmitter estimates channel information based on reference signals sent from a receiver, determines a transmit antenna weighting coefficient matrix based on the channel information, calculates a weight to be assigned to each of components of a multiplexed signal, and sends, to the receiver, training signals for respective signal components, the training signals being weighted by the calculated weights. On the other hand, the receiver determines a receive antenna weighting coefficient matrix based on the received training signals.

Claims

1. A wireless communication system for a communication between a transmitter and a receiver each having a plurality of antennas, by multiplexing a signal, the system comprising:

a channel information acquirer which obtains channel information representing a characteristic of a channel linking the transmitter and the receiver;

a first matrix determiner which determines a weighting coefficient matrix for the antennas of the transmitter based on the obtained channel information;

a weight calculator which calculates a weight to be assigned to each of components of the signal multiplexed at the transmitter;

a training signal sender which sends training signals for the respective components of the multiplexed signal to the receiver, the training signals being weighted by the weights calculated by the weight calculator; and

a second matrix determiner which determines a weighting coefficient matrix for the antennas of the receiver based on the received training signals.

2. The system of claim 1, wherein the channel information acquirer is on the part of the transmitter and estimates the channel information based on reference signals sent from the receiver to the transmitter and corresponding to respective antennas of the receiver.

3. The system of claim 2, wherein the channel information acquirer calibrates the channel information obtained based on the reference signals sent from the receiver to the transmitter to obtain the channel information in the direction from the transmitter to the receiver.

4. The system according to claim 1, wherein the first matrix determiner determines the weighting coefficient matrix for the antennas of the transmitter by performing one of maximal ratio combining, zero-forcing for canceling all unnecessary signals, a combination of maximal ratio combining and zero-forcing, and a singular value decomposition.

5. The system according to claim 1, wherein the second matrix determiner determines the weighting coefficient matrix for the antennas of the receiver by performing zero-forcing for canceling all unnecessary signals.

6. The system of claim 2 which employs a RTS/CTS function where the transmitter sends a transmission requesting packet RTS (Request To Send) and the receiver sends a confirmation packet CTS (Clear To Send) in response to the RTS, so that the data transfer is initiated when the transmitter receives the CTS,

wherein the receiver sends the CTS packet with reference signals included in the CTS packet, and

wherein the transmitter calculates a weight to be assigned to each of components of the multiplexed signal based on the channel information which is obtained based on the reference signals included in the CTS packet, and sends data packet including training signals for respective signal components sent in a multiplexed fashion.

7. A wireless communication apparatus for transmitting a signal by multiplexing the signal using a plurality of antennas, the apparatus comprising:

a channel information acquirer which obtains channel information representing a characteristic of a channel linking the apparatus to a receiver;

a matrix determiner which determines a weighting coefficient matrix for transmit antennas based on the obtained channel information;

a weight calculator which calculates a weight to be assigned to each of components of the multiplexed signal; and

a training signal sender which sends training signals for the respective components of the multiplexed signal to the receiver, the training signals being weighted by the weights calculated by the weight calculator.

8. The apparatus of claim 7, wherein the channel information acquirer estimates the channel information based on reference signals corresponding to respective antennas of the receiver and sent from the receiver.

9. The apparatus of claim 8, wherein the channel information acquirer calibrates the channel information obtained based on the reference signals sent from the receiver, to obtain the channel information in the direction from the apparatus to the receiver.

10. The apparatus of claim 7, wherein the matrix determiner determines the weighting coefficient matrix for the transmit antennas by performing one of maximal ratio combining, zero-forcing for canceling all unnecessary signals, a combination of maximal ratio combining and zero-forcing, and a singular value decomposition.

11. The apparatus of claim 8, which employs a RTS/CTS function where a transmitter sends a transmission requesting packet RTS (Request To Send) and initiates a data transfer in response to and upon receiving a confirmation packet CTS (Clear To Send) including the reference signals sent from a receiver,

wherein the channel information acquirer calculates a weight to be assigned to each of components of the multiplexed signal based on the channel information which is obtained based on the reference signals included in the CTS packet, and

wherein the training signal sender sends a data packet including training signals for respective signal components sent in a multiplexed fashion.

12. A wireless communication apparatus for receiving a multiplexed signal using a plurality of antennas, the apparatus comprising a reference signal sender which sends reference signals corresponding to respective antennas to a transmitter which sends the multiplexed signal.

13. The apparatus of claim 12, further comprising:

a training signal receiver which receives training signals for respective components of the multiplexed signal, the training signals being weighted by respective weights;

a matrix determiner which determines a weighting coefficient matrix for the antennas based on the received training signals; and

a signal retriever which iteratively performs zero-forcing and canceling so as to retrieve the multiplexed signal.

14. A wireless communication method for transmitting a signal by multiplexing the signal using a plurality of antennas, the method comprising steps of:

obtaining channel information representing a characteristic of a channel linked to a receiver;

determining a weighting coefficient matrix for transmit antennas based on the obtained channel information;

calculating a weight to be assigned to each of components of the multiplexed signal; and

sending training signals for the respective components of the multiplexed signal to the receiver, the training signals being weighted by the weights calculated in the calculating step.

15. The method of claim 14, wherein the step of obtaining the channel information estimates the channel information based on reference signals corresponding to respective antennas of the receiver and sent from the receiver.

16. The method of claim 15, wherein the step of obtaining the channel information calibrates the channel information obtained based on the reference signals sent from the receiver, to obtain the channel information in the direction toward the receiver.

17. The method of claim 14, wherein the step of determining a weighting coefficient matrix for transmit antennas by performing one of maximal ratio combining, zero-forcing for canceling all unnecessary signals, a combination of maximal ratio combining and zero-forcing, and a singular value decomposition.

18. The method of claim 15, which employs a RTS/CTS function where a transmitter sends a transmission requesting packet RTS (Request To Send) and initiates a data transfer in response to and upon receiving a confirmation packet CTS (Clear To Send) including the reference signals sent from a receiver,

wherein the step of obtaining the channel information comprises calculating a weight to be assigned to each of components of the multiplexed signal based on the channel information which is obtained based on the reference signals included in the CTS packet, and

wherein the step of sending training signals comprises sending a data packet including training signals for respective signal components sent in a multiplexed fashion.

19. A wireless communication method for receiving a multiplexed signal using a plurality of antennas, the method comprising a step of sending reference signals corresponding to respective antennas to a transmitter which sends the multiplexed signal.

20. The method of claim 19, further comprising steps of:

receiving training signals for respective components of the multiplexed signal, the training signals being weighted by respective weights;

determining a weighting coefficient matrix for the antennas based on the received training signals; and

retrieving the multiplexed signal by iteratively performing zero-forcing and canceling.

21. A computer program for a computer system to perform processing for transmitting a signal from a transmitter to a receiver by multiplexing the signal using a plurality of antennas, the program comprising steps of:

obtaining channel information representing a characteristic of a channel linked to a receiver;

determining a weighting coefficient matrix for transmit antennas based on the obtained channel information;

calculating a weight to be assigned to each of components of the multiplexed signal; and

sending training signals for the respective components of the multiplexed signal to the receiver, the training signals being weighted by the weights calculated in the calculating step.