System and method for transmit weight computation for vector beamforming radio communication

• US 20040209579A1
• Filed: 02/13/2004
• Published: 10/21/2004
• Est. Priority Date: 04/10/2003
• Status: Active Grant

• Current Assignee: IPR Licensing Incorporated (InterDigital, Inc.)
• Original Assignee: IPR Licensing Incorporated (InterDigital, Inc.)
• Inventors: Vaidyanathan, Chandra
• Granted Patent: US 7,099,678 B2
• Time in Patent Office: Days
• US Class Current: 455/101
• CPC Class Codes: H04B 7/0413 MIMO systems
• CPC Class Codes: H04B 7/0443 utilizing "waterfilling" technique
• CPC Class Codes: H04B 7/0465 taking power constraints at power amplifier or emission constraints, e.g. constant modulus, into account
• CPC Class Codes: H04B 7/0615 of weighted versions of same signal
• CPC Class Codes: H04L 1/0002 by adapting the transmission rate
• CPC Class Codes: H04L 1/0026 Transmission of channel quality indication

Abstract

A system and method for vector wireless radio communication (multiple modes or signal streams) between a first communication device and a second communication device using radio frequency (RF) communication techniques. At each communication device, signals are received at a plurality of antennas representing a plurality of modes simultaneously transmitted by the other communication device, wherein each mode is a signal stream. A transmit matrix is computed from signals received at the plurality of antennas. The transmit matrix distributes a plurality of modes among a plurality of antenna paths each associated with a corresponding one of the plurality of antennas of the first communication device, and is applied to the plurality of modes to be simultaneously transmitted from the plurality of antennas of one communication device to the other communication device.

Claims

1. A method for radio communication between a first communication device and a second communication device, comprising:

a. computing a transmit matrix from signals received at a plurality of antennas of the first communication device, wherein the signals represent a plurality of modes simultaneously transmitted by the second communication device to the first communication device, wherein each mode is a signal stream, and wherein the transmit matrix distributes a plurality of modes among a plurality of antenna paths associated with corresponding ones of the plurality of antennas of the first communication device; and

b. applying the transmit matrix to the plurality of modes to be simultaneously transmitted from the plurality of antennas of the first communication device to the second communication device.

2. The method of claim 1, and further comprising the step of computing receive weights from the signals received at the plurality of antennas of the first communication device, wherein the step of computing the transmit matrix is based on the receive weights.

3. The method of claim 1, and further comprising the step of computing a matched filter matrix from the signals received at the plurality of antennas.

4. The method of claim 3, wherein the step of computing the transmit matrix comprises computing the orthogonalization of the matched filter matrix.

5. The method of claim 1, wherein the steps of computing and applying are performed each time signals are received from the second communication device to update the transmit matrix.

6. The method of claim 1, wherein the steps of computing and applying are performed at baseband for each of a plurality of frequency sub-carriers associated with a multi-carrier modulation scheme used for each of the plurality of modes.

7. The method of claim 6, wherein the step of computing comprises computing the transmit matrix such that the power transmitted from each of the plurality of antennas of the first communication device is less than a maximum power.

8. The method of claim 7, wherein the step of computing comprises computing the transmit matrix such that the sum of the power at corresponding sub-carrier frequencies for each mode across the plurality of antenna paths is the same.

9. The method of claim 1, and further comprising the step of selecting a transmit data rate separately for each of the plurality of modes to be transmitted to the second communication device.

10. The method of claim 9, wherein the step of selecting is performed according to a received signal-to-noise ratio (SNR) for each of the plurality of modes at the second communication device.

11. The method of claim 10, and further comprising the step of estimating the received SNR for each of the plurality of modes at the second communication device from the received SNR for each of the plurality of modes at the first communication device.

12. The method of claim 11, wherein the step of estimating comprises equating the received SNR for each of the plurality of modes at the second communication device to the received SNR of the corresponding mode received at the first communication device.

13. The method of claim 12, wherein the step of estimating the received SNR for each of the plurality of modes at the second communication device comprises multiplying the received SNR of the corresponding mode received at the first communication device by a factor that compensates for a difference between a transmit power of the first communication device and a transmit power of the second communication device.

14. The method of claim 13, and further comprising the step of receiving from the second communication device information indicating the transmit power used by the second communication device.

15. The method of claim 9, wherein the step of selecting comprises selecting a slower transmit data rate for lower received SNR of a mode and selecting a higher data rate for higher received SNR of a mode.

16. The method of claim 9, wherein the step of selecting is performed based on received SNR information obtained each time a transmission is received from the second communication device.

17. The method of claim 16, and further comprising the step of receiving from the second communication device information indicating the received SNR for each of the plurality of modes received at the second communication device.

18. The method of claim 10, and further comprising the step of storing the received SNR for each of the plurality of modes received at respective ones of a plurality of other communication devices for use in rate selection when transmitting to a respective one of the plurality of other communication devices.

19. The method of claim 1, wherein for a synchronization field to be transmitted by the first communication device to the second communication device the step of applying comprises applying elements of the transmit matrix for corresponding ones of the plurality of modes for disjoint subsets of a plurality of frequency sub-carriers associated with a multi-carrier baseband modulation scheme.

20. The method of claim 19, wherein for a data field to be transmitted by the first communication device to the second communication device the step of applying comprises applying elements of the transmit matrix corresponding to each of the plurality of modes for all the plurality of sub-carriers associated with a baseband modulation scheme.

21. The method of claim 1, and further comprising the step of computing receive weights at a plurality of frequency sub-carriers associated with a multi-carrier baseband modulation scheme from signals received at the plurality of antennas of the first communication device representing a synchronization field transmitted by the second communication device using elements of a transmit matrix for corresponding ones of the plurality of modes for disjoint subsets of a plurality of frequency sub-carriers associated with a multi-carrier baseband modulation scheme, and deriving therefrom receive weights at each of the plurality of frequency sub-carriers for each of the plurality of modes.

22. The method of claim 21, wherein the step of deriving comprises interpolating the receive weights at remaining ones of the plurality of frequency sub-carriers for each of the plurality of modes from the receive weights for the plurality of frequency sub-carriers associated with the received signals.

23. A radio communication device comprising:

a. a plurality of antennas;

b. a radio transceiver coupled to the plurality of antennas, the radio transceiver capable of upconverting a plurality of transmit signals for simultaneous transmission via the plurality of antennas, and downconverting a plurality of signals simultaneously received at the plurality of antennas to produce a plurality of received signals; and

c. a baseband signal processor coupled to the radio transceiver that computes a transmit matrix from parameters derived from the plurality of received signals representing a plurality of modes simultaneously transmitted by another communication device, wherein each mode is a signal stream, wherein the transmit matrix distributes a plurality of modes among a plurality of antenna paths associated with corresponding ones of the plurality of antennas, and the baseband signal processor applies the transmit matrix to the plurality of modes to produce the plurality of transmit signals to be simultaneously transmitted to the other communication device.

24. The radio communication device of claim 23, wherein the baseband signal processor computes receive weights from the plurality of received signals and computes the transmit matrix based on the receive weights.

25. The radio communication device of claim 23, wherein the baseband signal processor computes a matched filter matrix from the signals received at the plurality of antennas.

26. The radio communication device of claim 25, wherein the baseband signal processor computes the transmit matrix by computing the orthogonalization of the matched filter matrix.

27. The radio communication device of claim 23, wherein the baseband signal processor computes the transmit matrix each time a plurality of signals are received at the plurality of antennas from the other communication device.

28. The radio communication device of claim 23, wherein the baseband signal processor computes the transmit matrix for each of a plurality of frequency sub-carriers associated with a multi-carrier modulation scheme used for each of the plurality of modes.

29. The radio communication device of claim 28, wherein the baseband signal processor computes the transmit matrix such that the power transmitted from each of the plurality of antennas is less than a maximum power.

30. The radio communication device of claim 29, wherein the baseband signal processor computes the transmit matrix such that the sum of the power at corresponding sub-carrier frequencies of each mode across the plurality of antenna paths is the same.

31. The radio communication device of claim 23, wherein the baseband signal processor selects a transmit data rate separately for each of the plurality of modes to be transmitted to the other communication device.

32. The radio communication device of claim 31, wherein the baseband signal processor selects a transmit data rate according to a received signal-to-noise ratio (SNR) for each of the plurality of modes at the other communication device.

33. The radio communication device of claim 32, wherein the baseband signal processor estimates the received SNR for each of the plurality of modes at the other communication device from the received SNR for corresponding ones of the plurality of modes.

34. The radio communication device of claim 33, wherein the baseband signal processor estimates the received SNR for each of the plurality of modes at the other communication by equating the received SNR for each of the plurality of modes at the other communication to the received SNR of the corresponding mode.

35. The radio communication device of claim 33, wherein the baseband signal processor estimates the received SNR for each of the plurality of modes at the other communication device by multiplying the received SNR of the corresponding mode by a factor that compensates for a difference between a transmit power of the communication device and a transmit power of the other communication device.

36. The radio communication device of claim 35, wherein the baseband signal processor computes the factor based on information received from the other communication device that indicates the transmit power used by the other communication device.

37. The radio communication device of claim 32, wherein the baseband signal processor selects a slower transmit data rate for lower received SNR of a mode and selects a higher data rate for higher received SNR of a mode.

38. The radio communication device of claim 32, wherein the baseband signal processor selects a transmit data rate based on received SNR information obtained each time a transmission is received from the other communication device.

39. The radio communication device of claim 32, wherein the baseband signal processor processes information received from the other communication device indicating the received SNR for each of the plurality of modes received at the other communication device.

40. The radio communication device of claim 32, and further comprising a memory that stores the received SNR for each of the plurality of modes received at respective ones of a plurality of other communication devices for use in rate selection when transmitting to a respective one of the plurality of other communication devices.

41. The radio communication device of claim 23, wherein when processing a synchronization field to be transmitted to the other communication device, the baseband signal processor applies elements of the transmit matrix for corresponding ones of the plurality of modes for disjoint subsets of a plurality of frequency sub-carriers associated with a multi-carrier baseband modulation scheme.

42. The radio communication device of claim 41, wherein when processing a data field to be transmitted to the other communication device, the baseband signal processor applies elements of the transmit matrix corresponding to each of the plurality of modes for all the plurality of sub-carriers associated with a baseband modulation scheme.

43. The radio communication device of claim 23, wherein the baseband signal processor computes receive weights at the plurality of frequency sub-carriers associated with a multi-carrier baseband modulation scheme from signals received at the plurality of antennas representing a synchronization field transmitted by the other communication device using elements of a transmit matrix for corresponding ones of the plurality of modes for disjoint subsets of a plurality of frequency sub-carriers associated with a multi-carrier baseband modulation scheme, and derives therefrom receive weights at each of the plurality of frequency sub-carriers for each of the plurality of modes.

44. The radio communication device of claim 43, wherein the baseband signal processor derives the receive weights at each of the plurality of frequency sub-carriers for each of the plurality of modes by interpolating the receive weights at remaining ones of the plurality of frequency sub-carriers for each of the plurality of modes from the receive weights for the plurality of frequency sub-carriers associated with the received signals.

45. A medium encoded with instructions that when executed, perform a method comprising the steps of:

a. computing a transmit matrix from parameters derived from a plurality of signals representing a plurality of modes simultaneously transmitted by a second communication device and received at a plurality of antennas of a first communication device, wherein each mode is a signal stream, wherein the transmit matrix distributes a plurality of modes among a plurality of antenna paths associated with corresponding ones of the plurality of antennas of the first communication device; and

b. applying the transmit matrix to the plurality of modes to be simultaneously transmitted from the plurality of antennas of the first communication device to the second communication device.

46. A method for radio communication between a first communication device and a second communication device using radio frequency (RF) communication techniques, comprising:

a. at the first communication device;

i. receiving at a plurality of antennas signals representing a plurality of modes simultaneously transmitted by the second communication device, wherein each mode is a signal stream;

ii. computing a transmit matrix from parameters derived from the signals received at the plurality of antennas, wherein the transmit matrix distributes a plurality of modes among a plurality of antenna paths each associated with a corresponding one of the plurality of antennas of the first communication device; and

iii. applying the transmit matrix to the plurality of modes to be simultaneously transmitted from the plurality of antennas of the first communication device to the second communication device;

b. at the second communication device;

i. receiving at a plurality of antennas signals representing a plurality of modes simultaneously transmitted by the first communication device;

ii. computing a transmit matrix from parameters derived from the signals received at the plurality of antennas, wherein the transmit matrix distributes a plurality of modes among a plurality of antenna paths each associated with a corresponding one of the plurality of antennas of the second communication device; and

iii. applying the transmit matrix to the plurality of modes to be simultaneously transmitted from the plurality of antennas of the second communication device to the first communication device;

c. wherein the step of computing the transmit matrix is repeated each time signals are received at the first communication device from the second communication device to update the transmit matrix at the first communication device, and the step of computing the transmit matrix is repeated each time signals are received at the second communication device from the first communication device to update the transmit matrix at the second communication device.

47. A radio communication system comprising first and second communication devices, wherein

a. the first communication device comprises:

i. a plurality of antennas;

ii. a radio transceiver coupled to the plurality of antennas, the radio transceiver capable of upconverting a plurality of transmit signals for simultaneous transmission via the plurality of antennas, and downconverting a plurality of signals simultaneously received at the plurality of antennas to produce a plurality of received signals; and

iii. a baseband signal processor coupled to radio transceiver that computes a transmit matrix from parameters derived from the plurality of received signals representing a plurality of modes simultaneously transmitted by the second communication device, wherein each mode is a signal stream, wherein the transmit matrix distributes a plurality of modes among a plurality of antenna paths associated with corresponding ones of the plurality of antennas of the first communication device, and the baseband signal processor applies the transmit matrix to the plurality of modes to produce the plurality of transmit signals to be simultaneously transmitted to the second communication device;

b. wherein the second communication device comprises;

i. a plurality of antennas;

ii. a radio transceiver coupled to the plurality of antennas, the radio transceiver capable of upconverting a plurality of transmit signals for simultaneous transmission via the plurality of antennas, and downconverting a plurality of signals simultaneously received at the plurality of antennas to produce a plurality of received signals; and

iii. a baseband signal processor coupled to radio transceiver that computes a transmit matrix from parameters derived from the plurality of received signals representing a plurality of modes simultaneously transmitted by the first communication device, wherein the transmit matrix distributes a plurality of modes among a plurality of antenna paths associated with corresponding ones of the plurality of antennas of the second communication device, and the baseband signal processor applies the transmit matrix to the plurality of modes to produce the plurality of transmit signals to be simultaneously transmitted to the first communication device;

c. wherein the baseband signal processors at the first and second communication devices compute their respective transmit matrix each time signals are received from the other communication device.

48. A method for simultaneously communicating a plurality of signals between a first communication device and a second communication device using radio frequency (RF) communication techniques, comprising:

a. applying a transmit matrix to a plurality of baseband signals to be transmitted from the first communication device to the second communication device, the transmit matrix distributing the plurality of baseband signals among a plurality of antennas of the first communication device for simultaneous transmission to the second communication device;

b. receiving the signals transmitted by the first communication device at a plurality of antennas of the second communication device to compute a matched filter matrix from the received signals;

c. computing from the matched filter matrix a transmit matrix for transmitting a plurality of baseband signals from the second communication device to the first communication device, the transmit matrix distributing the plurality of baseband signals among the plurality of antennas of the second communication device; and

d. applying the transmit matrix to the plurality of baseband signal to be transmitted from the second communication device to the first communication device.

49. The method of claim 48, wherein the step of computing the transmit matrix at the second communication device comprises computing the orthogonalization of the matched filter matrix.

50. The method of claim 49, and further comprising steps of

e. receiving at the first communication the plurality of signals transmitted by the second communication device and computing a matched filter matrix therefrom;

f. updating the transmit matrix at the first communication device from the matched filter matrix derived from the signals received from the second communication device.

51. The method of claim 50, wherein the step of updating the transmit matrix at the first communication device comprises orthogonalizing the matched filter matrix of the first communication device.

52. The method of claim 50, wherein steps (a), (c), (d) and (f) are performed at each of a plurality of frequency sub-carriers associated with a multi-carrier modulation scheme used for each of the plurality of baseband signals transmitted between the first and second communication devices.

53. The method of claim 52, wherein the step (c) of computing the transmit matrix at the second communication device further comprises normalizing the transmit matrix such that the power transmitted from each of the plurality of antennas of the second communication device is less than a maximum power.

54. The method of claim 52, wherein the step (c) of computing the transmit matrix comprises computing values for the transmit matrix such at each frequency sub-carrier, the sum of the power of the baseband signals across all of the antennas of the second communication device is equal to a constant.

55. The method of claim 54, wherein the step (f) of computing the transmit matrix at the first communication device further comprises normalizing the transmit matrix such that the power transmitted from each of the plurality of antennas of the first communication device is less than a maximum power.

56. The method of claim 55, wherein the step (f) of computing the transmit matrix comprises computing values for the transmit matrix such at each frequency sub-carrier, the sum of the power of the baseband signals across all of the antennas of the first communication device is equal to a constant.