Bi-directional beamforming multiple-input multiple-output wireless communication

• US 8,542,762 B2
• Filed: 10/13/2008
• Issued: 09/24/2013
• 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
• Primary Examiner(s): Malek, Leila
• Application Number:
  US12/250,056
• Publication Number:
  US 20090116569A1
• Time in Patent Office: 1,807 Days
• Field of Search: 375/267, 375/259, 375/260, 375/299, 455/69, 455/88, 455/24, 455/101
• US Class Current: 375/267
• 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 by a second device and transmitted to the first device;

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

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; and

transmitting a non-beamformed downlink broadcast signal;

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;

detecting the non-beamformed downlink broadcast signal transmitted by the first device;

computing a plurality of uplink beamforming weight vectors based on the plurality of downlink signal streams beamformed by the first device and transmitted to the second device and based on the detected non-beamformed downlink broadcast signal detected by the second device; and

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;

wherein the first device repeats the computing each time a new plurality of uplink signal streams are received at the first plurality of antennas of the first device from the second device to update the plurality of beamforming weight vectors used by the first device for application to the plurality of downlink signal streams to be transmitted, and wherein the second device repeats the computing each time the second device receives a new plurality of downlink signal streams from the first device to update the plurality of beamforming weight vectors used by the second device for application to the plurality of uplink signal streams to be transmitted.

2. The method of claim 1, wherein comprises transmitting the non-beamformed downlink broadcast signal comprises transmitting the non-beamformed downlink broadcast signal with a higher power than a power used to transmit beamformed downlink signal streams to the second device.

3. 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.

4. The method of claim 3, 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 based on uplink beams formed from application of the plurality of uplink beamforming weight vectors to the plurality of uplink signal streams at the second device.

5. 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.

6. The method of claim 5, 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 based on downlink beams formed from application of the plurality of downlink beamforming weight vectors to the plurality of downlink signal streams at the first device.

7. The method of claim 1, further comprising:

determining whether there are uplink signal streams in a queue; and

if there are uplink signal streams in the queue, then performing the computing and applying operations in the second device and otherwise not performing the computing and applying operations.

8. 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 based on signals resulting from reception at the plurality of signal streams that were beamformed at another device by applying transmit beamforming weight vectors and transmitted from the other device and based on signals resulting from reception of a non-beamformed broadcast signal transmitted by the other device and received at the plurality of antennas;

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; and

repeat the compute operation each time a new plurality of signal streams are received at the plurality of antennas from the other device to update the plurality of beamforming weight vectors used for application to the plurality of signal streams to be transmitted to the other device.

9. The apparatus of claim 8, 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.

10. The apparatus of claim 8, wherein the controller is configured to compute the plurality of beamforming weight vectors and apply the plurality of beamforming weight vectors to the plurality of signal streams when there are uplink signal streams in a queue and otherwise the controller does not compute the plurality of beamforming weight vectors and does not apply the plurality of beamforming weight vectors to the plurality of signal streams.

11. A non-transitory computer readable storage media encoded with instructions for execution by a processor and when executed cause the processor to:

compute a plurality of beamforming weight vectors from signals resulting from reception of a plurality of signal streams that were beamformed from at another device by application of transmit beamforming weight vectors and transmitted from the other device and based on signals resulting from reception of a non-beamformed broadcast signal transmitted by the other device and received at the plurality of antennas

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; and

repeat the compute operation each time the plurality of signal streams are received at the plurality of antennas from the other device to update the plurality of beamforming weight vectors used for application to the plurality of signal streams to be transmitted to the other device.

12. The non-transitory computer readable storage media of claim 11, wherein the instructions that cause the processor to compute the plurality of beamforming weight vectors comprise instructions that cause the processor to compute a signal covariance matrix from signals resulting from reception of the plurality of signal streams at the plurality of antennas to compute the plurality of beamforming weight vectors from the signal covariance matrix.

13. The non-transitory computer readable medium of claim 11, wherein the instructions that cause the processor to compute the plurality of beamforming weight vectors comprise instructions that cause the processor to:

compute the beamforming weight vectors and apply the beamforming weight vectors to uplink signal streams when there are uplink signal streams in a queue, and otherwise not computing the beamforming weight vectors and not applying the beamforming weight vectors to the uplink signal streams.

14. 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 received 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 of a first plurality of signal streams beamformed by the second wireless communication device and received at the first plurality of antennas

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

repeat the compute operation each time uplink signal streams are received from the second wireless communication device to update the plurality of beamforming weight vectors used for application to the plurality of downlink signal streams to be transmitted from the first wireless communication device to the second wireless communication device; and

generate a non-beamformed downlink broadcast signal for transmission by the first transmitter;

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 received by respective ones of the second plurality of antennas; and

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

compute a plurality of uplink beamforming weight vectors based on the plurality of downlink signal streams beamformed by the first wireless communication device and received at the second plurality of antennas and based on signals resulting from reception of the non-beamformed downlink broadcast signal transmitted by the first wireless communication device and received at the second plurality antennas;

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

repeat the compute operation each time new downlink signal streams are received from the first wireless communication device to update the plurality of beamforming weight vectors used for application to the plurality of uplink signal streams to be transmitted from the second wireless communication device to the first wireless communication device.

15. The system of claim 14, 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.

16. The system of claim 14, 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.

17. The system of claim 14, wherein the first transmitter of the first wireless communication device is configured to transmit the non-beamformed downlink broadcast signal with a higher power than a power used to transmit the beamformed downlink signal streams to the second wireless communication device.

18. The system of claim 14, wherein the second controller of the second wireless communications device is further configured to compute and apply the uplink beamforming weight vectors if there are uplink signal streams in a queue and otherwise does not compute and apply the uplink beamforming weight vectors.