Bi-Directional Beamforming Multiple-Input Multiple-Output Wireless Communication

• US 20090116569A1
• Filed: 10/13/2008
• Published: 05/07/2009
• Est. Priority Date: 11/05/2007
• Status: Active Grant

• Current Assignee: Cisco Technology, Inc. (Cisco Systems, Inc.)
• Original Assignee: Cisco Technology, Inc. (Cisco Systems, Inc.)
• Inventors: Jin, Hang
• Granted Patent: US 8,542,762 B2
• Time in Patent Office: Days
• US Class Current: 375/260
• CPC Class Codes: H04B 7/0417 Feedback systems
• CPC Class Codes: H04B 7/0617 for beam forming
• CPC Class Codes: H04B 7/086 using weights depending on external parameters, e.g. direction of arrival [DOA], predetermined weights or beamforming

Abstract

Techniques are provided herein to configure first and second wireless communication devices in order to perform bi-directional beamformed multiple-input multiple-output (MIMO) communication. Each device uses received signals from the other device to compute beamforming weight vectors for application to a plurality of signal streams to be simultaneously beamformed transmitted to the other device.

Claims

1. A method comprising:

at a first device comprising a first plurality of antennas;

receiving at the first plurality of antennas a plurality of uplink signal streams that were beamformed from a second device to the first device;

computing a plurality of downlink beamforming weight vectors from signals resulting from reception at the first plurality of antennas of the plurality of signal streams beamformed by the second device;

applying the plurality of downlink beamforming weight vectors to a plurality of downlink signal streams for simultaneous beamform transmission via the first plurality of antennas of the first device to the second device;

at the second device comprising a second plurality of antennas;

receiving at the second plurality of antennas the plurality of downlink signal streams that were beamformed by the first device;

computing a plurality of uplink beamforming weight vectors from signals resulting from reception at the second plurality of antennas of the plurality of downlink signal streams beamformed by the first device;

applying the plurality of uplink beamforming weight vectors to a plurality of uplink signal streams for simultaneous beamform transmission via the second plurality of antennas of the second device to the first device.

2. The method of claim 1, and further comprising at the first device transmitting a downlink broadcast signal, and at the second device, receiving the downlink broadcast signal at the second plurality of antennas, and wherein computing the plurality of uplink beamforming weight vectors is based on signals resulting from detection of the downlink broadcast signal received at the second plurality of antennas of the second device.

3. The method of claim 2, wherein computing the plurality of uplink beamforming weight vectors comprises computing updates to the plurality of uplink beamforming weight vectors at each of multiple instances of reception of downlink broadcast signals.

4. The method of claim 2, wherein transmitting the downlink broadcast signal comprises transmitting the downlink broadcast signal with a higher power than a power used to transmit the plurality of downlink signal streams.

5. The method of claim 1, wherein computing the plurality of downlink beamforming weight vectors comprises computing a signal covariance matrix from signals resulting from reception of the plurality of uplink signal streams at the first plurality of antennas of the first device, and computing the plurality of downlink beamforming weight vectors from the signal covariance matrix.

6. The method of claim 5, wherein computing the signal covariance matrix is based on uplink spatial signatures derived from reception at the first plurality of antennas of the first device of uplink beams formed from application of the plurality of uplink beamforming weight vectors to the plurality of uplink signal streams at the second device.

7. The method of claim 1, wherein computing the plurality of uplink beamforming weight vectors comprises computing a signal covariance matrix from signals resulting from reception of the plurality of downlink signal streams at the second plurality of antennas of the second device, and computing the plurality of uplink beamforming weight vectors from the signal covariance matrix.

8. The method of claim 7, wherein computing the signal covariance matrix is based on downlink spatial signatures derived from reception at the second plurality of antennas of the second device of downlink beams formed from application of the plurality of downlink beamforming weights to the plurality of downlink signal streams at the first device.

9. An apparatus comprising:

a plurality of antennas;

a transmitter coupled to the plurality of antennas and configured to produce individual transmit signals for transmission by respective ones of the plurality of antennas;

a receiver coupled to the plurality of antennas and configured to produce individual receive signals from signals received by respective ones of the plurality of antennas; and

a controller coupled to the receiver and transmitter, wherein the controller is configured to;

compute a plurality of beamforming weight vectors from signals resulting from reception at the plurality of antennas of a plurality of signals streams beamformed from another device; and

apply the plurality of beamforming weight vectors to a plurality of signal streams for simultaneous beamform transmission via the plurality of antennas to the other device.

10. The apparatus of claim 9, wherein the controller is further configured to compute the plurality of beamforming weight vectors based on signals resulting from reception of a broadcast signal at the plurality of antennas.

11. The apparatus of claim 10, wherein the controller is configured to compute updates to the plurality of beamforming weight vectors at each of multiple instances of reception of broadcast signals.

12. The apparatus of claim 9, wherein the controller is configured to compute the plurality of beamforming weight vectors by computing a signal covariance matrix from signals resulting from reception of the plurality of signal streams at the plurality of antennas, and computing the plurality of beamforming weight vectors from the signal covariance matrix.

13. Logic encoded in one or more tangible media for execution and when executed operable to:

compute a plurality of beamforming weight vectors from signals resulting from reception at a plurality of antennas of a plurality of signals streams beamformed from another device; and

apply the plurality of beamforming weight vectors to a plurality of signal streams for simultaneous beamform transmission via the plurality of antennas to the other device.

14. The logic of claim 13, wherein the logic that computes the plurality of beamforming weight vectors comprises logic that computes the plurality of beamforming weight vectors based on signals resulting from reception of a broadcast signal at the plurality of antennas.

15. The logic of claim 14, wherein the logic that computes the plurality of beamforming weight vectors comprises logic that computes updates to the plurality of beamforming weight vectors at each of multiple instances of reception of broadcast signals.

16. The logic of claim 13, wherein the logic that computes the plurality of beamforming weight vectors comprises logic that computes a signal covariance matrix from signals resulting from detection of the plurality of signal streams at the plurality of antennas and logic that computes the plurality of beamforming weight vectors from the signal covariance matrix.

17. A system comprising:

a first wireless communication device and a second wireless communication device;

the first wireless communication device comprising;

a first plurality of antennas;

a first transmitter coupled to the first plurality of antennas and configured to produce individual transmit signals for transmission by respective ones of the first plurality of antennas;

a first receiver coupled to the first plurality of antennas and configured to produce individual receive signals from signals detected by respective ones of the first plurality of antennas; and

a first controller coupled to the first receiver and first transmitter, wherein the first controller is configured to;

compute a plurality of downlink beamforming weight vectors from signals resulting from reception at the first plurality of antennas of the plurality of signal streams beamformed by the second wireless communication device; and

apply the plurality of downlink beamforming weight vectors to a corresponding plurality of downlink signal streams for simultaneous beamform transmission via the first plurality of antennas of the first wireless communication device to the second wireless communication device;

the second wireless communication device comprising;

a second plurality of antennas;

a second transmitter coupled to the second plurality of antennas and configured to produce individual transmit signals for transmission by respective ones of the second plurality of antennas;

a second receiver coupled to the second plurality of antennas and configured to produce individual receive signals from signals detected by respective ones of the second plurality of antennas; and

a second controller coupled to the receiver and transmitter, wherein the second controller is configured to;

compute a plurality of uplink beamforming weight vectors from signals resulting from reception at the second plurality of antennas of the plurality of downlink signal streams transmitted by the first wireless communication device;

applying the plurality of uplink beamforming weight vectors to a corresponding plurality of uplink signal streams for simultaneous beamform transmission via the second plurality of antennas of the second wireless communication device to the first wireless communication device.

18. The system of claim 17, wherein the first controller is configured to generate a downlink broadcast signal that is transmitted via the first transmitter, and the second controller is configured to compute the plurality of uplink beamforming weight vectors based on signals resulting from detection of the downlink broadcast signal received at the second plurality of antennas of the second wireless communication device.

19. The system of claim 17, wherein the second controller is configured to compute updates to the plurality of uplink beamforming weight vectors at each of multiple instances of reception of downlink broadcast signals.

20. The system of claim 17, wherein the first controller is configured to compute the plurality of downlink beamforming weight vectors by computing a signal covariance matrix from signals resulting from reception of the plurality of uplink signal streams at the first plurality of antennas and to compute the plurality of downlink beamforming weight vectors from the signal covariance matrix.

21. The system of claim 17, wherein the second controller is configured to compute the plurality of uplink beamforming weight vectors by computing a signal covariance matrix from signals resulting from reception of the plurality of downlink signal streams at the second plurality of antennas and to compute the plurality of uplink beamforming weight vectors from the signal covariance matrix.