RF-based antenna selection in MIMO systems

• US 20050287962A1
• Filed: 06/25/2004
• Published: 12/29/2005
• Est. Priority Date: 06/25/2004
• Status: Active Grant

• Current Assignee: Mitsubishi Electric Research Laboratories, Inc. (Mitsubishi Electric Corporation)
• Original Assignee: Mitsubishi Electric Research Laboratories, Inc. (Mitsubishi Electric Corporation)
• Inventors: Zhang, Jinyun, Molisch, Andreas F., Sudarshan, Pallav, Mehta, Neelesh B.
• Granted Patent: US 7,327,983 B2
• Time in Patent Office: Days
• US Class Current: 455/101
• CPC Class Codes: H01Q 3/26 varying the relative phase or relative amplitude of energisation between two or more active radiating elements; varying the distribution of energy across a radiating aperture H01Q3/12, H01Q3/22, H01Q3/24 take precedence
• CPC Class Codes: H04B 7/0417 Feedback systems
• CPC Class Codes: H04B 7/0626 Channel coefficients, e.g. channel state information [CSI]
• CPC Class Codes: H04B 7/0691 using subgroups of transmit antennas
• CPC Class Codes: H04B 7/0697 using spatial multiplexing
• CPC Class Codes: H04B 7/0848 Joint weighting
• CPC Class Codes: H04B 7/0874 using subgroups of receive antennas
• CPC Class Codes: H04L 1/0036 arrangements specific to the receiver
• CPC Class Codes: H04L 1/0625 Transmitter arrangements
• CPC Class Codes: H04L 1/0631 Receiver arrangements

Abstract

A method is presented for processing signals of a multiple-input, multiple-output communications system in the RF domain. The system includes multiple transmit antennas and multiple receive antennas connected by a wireless channel. A matrix M is generated based on long-term characteristics of the wireless channel. The matrix M is multiplied times input RF signals to obtain output RF signals. The matrix can be generated in a transmitter, a receiver, or both.

Claims

1. A method for processing RF signals in a multiple-input, multiple-output communications system, including multiple transmit antennas and multiple receive antennas connected by a wireless channel, comprising:

generating a matrix M based on long-term characteristics of the wireless channel; and

multiplying the matrix M times the input RF signals to obtain output RF signals.

2. The method of claim 1, in which the generating is in a transmitter, and the output RF signals are fed to multiple transmit antennas.

3. The method of claim 1, in which the generating is in a receiver, and the input RF signals are obtained from multiple receive antennas.

4. The method of claim 1, further comprising:

generating, in a transmitter, a first matrix M based on long-term characteristics of the wireless channel;

multiplying the first matrix M times first input RF signals to obtain first output RF signals fed to multiple transmit antennas;

generating, in receiver, a second matrix M based on the long-term characteristics of the wireless channel; and

multiplying the second matrix M times second input RF signals obtained from multiple receive antennas to obtain second output RF signals.

5. The method of claim 2, further comprising:

modulating a plurality of input bit streams into L RF signals.

6. The method of claim 3, further comprising:

demodulating a subset of the output RF signals.

7. The method of claim 1, in which the matrix M is in a form

M=BQ,

where B is a full rank matrix, and Q is an matrix of singular vectors obtained by decomposing a covariance matrix.

8. The method of claim 1, in which the matrix M includes a plurality of elements, and only phase characteristics of the elements are used to generate the matrix M.

9. The method of claim 8, further comprising:

setting a subset of the elements to zero.

10. The method of claim 9, in which the setting is based on amplitude characteristics of the elements.

11. The method of claim 1, in which the input RF signals are generated using spatial-diversity gain techniques in a transmitter.

12. The method of claim 1, in which the input RF signals are generated using spatial-multiplexing gain techniques in a transmitter.

13. The method of claim 1, in which a number of the output RF signals is less than a number of the input RF signals.

14. The method of claim 13, further comprising:

selecting a subset of output RF signals for demodulation.

15. The method of claim 6, further comprising:

selecting a subset of RF signals using the matrix M.

16. The method of claim 15, further comprising:

selecting a subset of the subset of RF signals using a L/K switch.

17. The method of claim 5, further comprising:

routing the L RF signals to K input RF signals.