System and method for joint maximal ratio combining using time-domain signal processing

• US 6,873,651 B2
• Filed: 07/18/2002
• Issued: 03/29/2005
• Est. Priority Date: 03/01/2002
• Status: Expired due to Term

• Current Assignee: IPR Licensing Incorporated (InterDigital, Inc.)
• Original Assignee: Cognio, Inc. (Cisco Systems, Inc.)
• Inventors: Tesfai, Yohannes, Vaidyanathan, Chandra, Sugar, Gary L.
• Primary Examiner(s): Chin, Stephen
• Assistant Examiner(s): WILLIAMS, LAWRENCE B
• Application Number:
  US10/064,482
• Publication Number:
  US 20030165187A1
• Time in Patent Office: 985 Days
• Field of Search: 375/148, 375/219, 375/220, 375/229, 381/94.1
• US Class Current: 375/219
• CPC Class Codes: H04B 7/0615 of weighted versions of same signal
• CPC Class Codes: H04B 7/0669 using different channel coding between antennas space-time coding H04L1/0618
• CPC Class Codes: H04B 7/0671 using different delays between antennas
• 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: H04L 1/06 using space diversity
• CPC Class Codes: H04L 2025/03445 Time domain
• CPC Class Codes: H04L 25/0204 of multiple channels
• CPC Class Codes: H04L 27/2601 Multicarrier modulation systems
• CPC Class Codes: H04W 52/42 in systems with time, space, frequency or polarisation diversity

Abstract

A spatial signal processing system and method are provided to optimize the received signal-to-noise ratio (SNR) at a first radio communication device based on the transmit filter at another radio communication device. Using an estimate of the channel derived from a signal received at one device from another device, an iterative process is provided to determine complex weights for one or more tapped delay-line transmit filters at each of two communication devices that optimize the received SNR.

Claims

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

a. at the first communication device;

i. generating a transmit filter vector for processing a signal to be transmitted from the first communication device via a plurality of antennas of the first communication device to the second communication device, the transmit filter vector comprised of a plurality of transmit filter sub-vectors defining one or more complex weights associated with a transmit tapped-delay line filter, each transmit filter sub-vector associated with a corresponding one of the plurality of antennas of the first communication device and having a length corresponding to the number taps of the associated transmit tapped-delay line filter; and

ii. applying the transmit filter vector to a signal to be transmitted from the first communication device to the second communication device;

b. at the second communication device;

i. generating a receive filter matrix from a signal received by one or more antennas of the second communication device from the first communication device, the receive filter matrix comprised of one or more sub-matrices each being a convolution matrix derived from a receive filter sub-vector, wherein each receive filter sub-vector defines one or more complex weights associated with a receive tapped-delay line filter for a corresponding one of the one or more antennas of the second communication device;

ii. computing a principal eigenvector of a product of the receive filter matrix and a Hermitian of the receive filter matrix, the principal eigenvector comprised of one or more sub-vectors each having a length corresponding to a number of taps of a transmit tapped-delay line filter associated with a corresponding one of the one or more antennas of the second communication device;

iii. deriving from the one or more sub-vectors of the principal eigenvector one or more transmit filter sub-vectors that form a transmit filter vector, each transmit filter sub-vector associated with a corresponding one of the one or more antennas of the second communication device and defining one or more complex weights associated with the transmit tapped-delay line filter for a corresponding one of the one or more antennas of the second communication device; and

iv. applying the transmit filter vector at the second communication device to a signal to be transmitted from the second communication device to the first communication device.

2. The method of claim 1, wherein the step of generating the transmit filter vector at the first communication device further comprises normalizing each sub-vector of the transmit filter vector so that the total power associated with a transmitted signal is divided equally among the plurality of antennas of the first communication device.

3. The method of claim 1, wherein the step of deriving the one or more transmit filter sub-vectors for the second communication device comprises equating each transmit filter sub-vector to the corresponding sub-vector of the principal eigenvector.

4. The method of claim 1, wherein the second communication device has a plurality of antennas, and wherein the step of deriving the one or more transmit filter sub-vectors at the second communication device further comprises computing the norm of each of a plurality of sub-vectors of the principal eigenvector and dividing each sub-vector of the principal eigenvector by the norm and by the square root of the number of plurality of antennas of the second communication device so that the power of the signal transmitted by the second communication device is divided equally among the plurality of antennas of the second communication device.

5. The method of claim 1, and further comprising at the first communication device steps of:

iii. generating a receive filter matrix from a signal received by the plurality of antennas of the first communication device from the second communication device, the receive filter matrix comprised of a plurality of sub-matrices each being a convolution matrix derived from a receive filter sub-vector, wherein each sub-vector defines one or more complex weights associated with a receive tapped-delay line filter for a corresponding one of the plurality of antennas of the first communication device;

iv. computing a principal eigenvector of a product of the receive filter matrix and a Hermitian of the receive filter matrix, the principal eigenvector comprised of a plurality of sub-vectors each having a length corresponding to the number of taps of the transmit tapped-delay line filter of the first communication device; and

v. updating from the plurality of sub-vectors of the principal eigenvector the plurality of transmit filter sub-vectors.

6. The method of claim 5, and further comprising repeating steps (iii) through (v) at the first communication device and steps (i) through (iv) at the second communication device for signals transmitted between the first and second communication devices, to converge to transmit filter vectors at the first and second communication devices that optimize the signal-to-noise ratio of signals communicated between them.

7. The method of claim 5, wherein the step of updating the transmit filter sub-vectors of the first communication device comprises equating each transmit filter sub-vector to the corresponding sub-vector of the principal eigenvector computed by the first communication device.

8. The method of claim 5, wherein the step of updating the transmit filter sub-vectors of the first communication device comprises computing the norm of each of a plurality of sub-vectors of the principal eigenvector and dividing each sub-vector of the principal eigenvector by the norm and by the square root of the number of plurality of antennas of the first communication device.

24. The method of claim 1, wherein the second communication device comprises a plurality of antennas, and wherein step (i) at the second communication device of generating comprises generating the receive filter matrix comprised of a plurality of sub-matrices each being a convolution matrix derived from a receive filter sub-vector associated with a corresponding one of the plurality of antennas of the second communication device.

25. The method of claim 24, wherein step (iii) at the second communication device comprises deriving a plurality of transmit filter sub-vectors that form the transmit filter vector, wherein each transmit filter sub-vector is associated with a corresponding one of the plurality of antennas of the second communication device.

26. The method of claim 25, wherein step (iv) at the second communication device comprises applying the transmit filter vector to a signal to be transmitted via the plurality of antennas of the second communication device to the first communication device.

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

a. generating a transmit filter vector for processing a signal to be transmitted from the first communication device to the second communication device, the transmit filter vector comprised of a plurality of transmit filter sub-vectors defining one or more complex weights associated with a transmit tapped-delay line filter, each transmit filter sub-vector associated with a corresponding one of a plurality of antennas of the first communication device and having a length corresponding to the number taps of the associated transmit tapped-delay line filter;

b. applying the transmit filter vector to a signal to be transmitted from the first communication device to the second communication device;

c. generating a receive filter matrix from a signal received by the plurality of antennas of the first communication device from the second communication device, the receive filter matrix comprised of a plurality of sub-matrices each being a convolution matrix derived from a receive filter sub-vector, wherein each receive filter sub-vector defines one or more complex weights associated with a receive tapped-delay line filter for a corresponding one of the plurality of antennas of the first communication device;

d. computing a principal eigenvector of a product of the receive filter matrix and a Hermitian of the receive filter matrix, the principal eigenvector comprised of a plurality of sub-vectors each having a length corresponding to the number of taps of the transmit tapped-delay line filter of the first communication device; and

e. updating from the plurality of sub-vectors of the principal eigenvector the plurality of transmit filter sub-vectors.

10. The method of claim 9, wherein the step of updating comprises equating each transmit filter sub-vector to the corresponding sub-vector of the principal eigenvector.

11. The method of claim 9, wherein the step of updating further comprises computing the norm of each of a plurality of sub-vectors of the principal eigenvector and dividing each sub-vector of the principal eigenvector by the norm and by the square root of the number of plurality of antennas of the first communication device so that the power of the signal transmitted by the first communication device is divided equally among the plurality of antennas of the first communication device.

12. The method of claim 9, and further comprising repeating steps (c) through (e) when a signal is received at the first communication device from the second communication device to update the transmit filter vector at the first communication device for transmission of signals from the first communication device to the second communication device.

27. The method of claim 9, and further comprising repeating steps (c) through (e) when a signal is received at the first communication device from the second communication device to update the transmit filter vector at the first communication device for transmission of signals from the first communication device to the second communication device, and converging to a transmit filter vector at the first communication device that optimizes the signal-to-noise ratio of signals communicated between the first and second communication device.

30. The method of claim 9, wherein the step of generating the receive filter matrix comprises generating the receive filter matrix from a plurality of signals transmitted by a plurality of antennas of the second communication device and received by the plurality of antennas of the first communication device.

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

a. generating a transmit filter vector for processing a signal to be transmitted from a first communication device to a second communication device, the transmit filter vector comprised of a plurality of transmit filter sub-vectors defining one or more complex weights associated with a transmit tapped-delay line filter, each transmit filter sub-vector associated with a corresponding one of a plurality of antennas of the first communication device and having a length corresponding to the number taps of the associated transmit tapped-delay line filter;

b. applying the transmit filter vector to a signal to be transmitted from the first communication device to the second communication device;

c. generating a receive filter matrix from a signal received by the plurality of antennas of the first communication device from the second communication device, the receive filter matrix comprised of a plurality of sub-matrices each being a convolution matrix derived from a receive filter sub-vector, wherein each receive filter sub-vector defines one or more complex weights associated with a receive tapped-delay line filter for a corresponding one of the plurality of antennas of the first communication device;

d. computing a principal eigenvector of a product of the receive filter matrix and a Hermitian of the receive filter matrix, the principal eigenvector comprised of a plurality of sub-vectors each having a length corresponding to the number of taps of the transmit tapped-delay line filter of the first communication device; and

e. updating from the plurality of sub-vectors of the principal eigenvector the plurality of transmit filter sub-vectors.

14. The medium of claim 13, wherein the instructions encoded on the medium for performing the step of updating comprises instructions for equating each transmit filter sub-vector to the corresponding sub-vector of the principal eigenvector.

15. The medium of claim 13, wherein the instructions encoded on the medium for performing the step of updating further comprise instructions that compute the norm of each of a plurality of sub-vectors of the principal eigenvector and divide each sub-vector of the principal eigenvector by the norm and by the square root of the number of plurality of antennas of the first communication device so that the power of the signal transmitted by the first communication device is divided equally among the plurality of antennas of the first communication device.

16. The medium of claim 13, and further comprising instructions that repeat steps (c) through (e) for each signal received at the first communication device from the second communication device to update the transmit filter vector at the first communication device for transmission of signals from the first communication device to the second communication device.

17. The medium of claim 13, wherein the instructions associated with the computations of steps (a) through (e) are implemented by one or more arrays of gates.

18. The medium of claim 13, wherein the instructions are processor readable instructions, that when executed by a processor, cause the processor to perform steps (a) through (e).

19. A communication device comprising the baseband signal processing integrated circuit device of claim 13, and further comprising:

a. a transmitter coupled to the baseband signal processing integrated circuit and to be coupled to the plurality of antennas to upconvert transmit signals generated by the baseband signal processing integrated circuit for transmission via respective ones of the plurality of antennas; and

b. a receiver coupled to the baseband signal processing integrated circuit and to be coupled to the plurality of antennas to downconvert signals received by the plurality of antennas and to produce receive signals that are coupled to the baseband signal processing integrated circuit.

28. The medium of claim 13, and further comprising instructions that repeat steps (c) through (e) when a signal received at the first communication device from the second communication device to update the transmit filter vector at the first communication device for transmission of signals from the first communication device to the second communication device, and converging to a transmit filter vector at the first communication device that optimizes the signal-to-noise ratio of signals communicated between the first and second communication device.

29. A baseband signal processing integrated circuit device comprising the one or more arrays of gates of claim 17.

31. The medium of claim 13, wherein the instructions encoded on the medium for generating the receive filter matrix comprise instructions for generating the receive filter matrix from a plurality of signals transmitted by a plurality of antennas of the second communication device and received by the plurality of antennas of the first communication device.

20. A semiconductor device comprising a plurality of gates configured to implement:

a. a plurality of transmit tapped delay-line filters, each associated with a corresponding one of a plurality of antennas;

b. a plurality of receive tapped delay-line filters, each associated with a corresponding one of the plurality of antennas;

c. one or more computation blocks that;

i. generate a transmit filter vector for processing a signal to be transmitted to another communication device, the transmit filter vector comprised of a plurality of transmit filter sub-vectors defining one or more complex weights associated with the transmit tapped-delay line filter, each transmit filter sub-vector associated with a corresponding one of the plurality of antennas and having a length corresponding to the number taps of the associated transmit tapped-delay line filter;

ii. apply the transmit filter vector to a signal to be transmitted from the other communication device;

iii. generate a receive filter matrix from a signal received by the plurality of antennas from the other communication device, the receive filter matrix comprised of a plurality of sub-matrices each being a convolution matrix derived from a receive filter sub-vector, wherein each receive filter sub-vector defines one or more complex weights associated with the receive tapped-delay line filter for a corresponding one of each of the plurality of antennas;

iv. compute a principal eigenvector of a product of the receive filter matrix and a Hermitian of the receive filter matrix, the principal eigenvector comprised of a plurality of sub-vectors each having a length corresponding to the number of taps of the transmit tapped-delay line filter; and

v. update from the plurality of sub-vectors of the principal eigenvector the plurality of transmit filter sub-vectors.

21. The semiconductor device of claim 20, wherein the computation blocks update the plurality of transmit sub-vectors by equating each transmit filter sub-vector to the corresponding sub-vector of the principal eigenvector.

22. The semiconductor device of claim 20, wherein the computation blocks updates the plurality of transmit sub-vectors by computing the norm of each of a plurality of sub-vectors of the principal eigenvector and dividing each sub-vector of the principal eigenvector by the norm and by the square root of the number of the plurality of antennas so that the power of the signal transmitted is divided equally among the plurality of antennas.

23. A radio communication device comprising the semiconductor device of claim 20, and further comprising:

a. a plurality of antennas;

b. a transmitter coupled to the plurality of antennas and to the semiconductor device to upconvert transmit signals generated by the semiconductor device for transmission via respective ones of the plurality of antennas; and

c. a receiver coupled to the plurality of antennas and to the semiconductor device to downconvert signals received by the plurality of antennas and produce receive signals that are coupled to the semiconductor device.

32. The semiconductor device of claim 20, wherein the one or more computation blocks that generate the receive filter matrix generate the receive filter matrix from a plurality of signals transmitted by a plurality of antennas of the second communication device and received by the plurality of antennas of the first communication device.

33. A radio communication system comprising:

a. a first communication device having N plurality of antennas, a baseband signal processor that generates transmit signals and that recovers data from receive signals and a radio transceiver coupled to the baseband signal processor that upconverts the transmit signals for transmission via the N plurality of antennas and downconverts signals received by the N plurality of antennas to produce receive signals, wherein the baseband signal processor of the first communication device (i) generates a transmit filter vector for processing a signal to be transmitted from the first communication device via the N plurality of antennas to a second communication device, the transmit filter vector comprised of a plurality of transmit filter sub-vectors defining one or more complex weights associated with a transmit tapped-delay line filter, each transmit filter sub-vector associated with a corresponding one of the plurality of antennas of the first communication device and having a length corresponding to the number taps of the associated transmit tapped-delay line filter; and

(ii) applies the transmit filter vector to a signal to be transmitted from the first communication device via the N plurality of antennas to the second communication device;

b. the second communication device having M plurality of antennas, a baseband signal processor that generates transmit signals and that recovers data from receive signals and a radio transceiver coupled to the baseband signal processor that upconverts the transmit signals for transmission via the M plurality of antennas and downconverts signals received by the M plurality of antennas to produce receive signals, wherein the baseband signal processor of the second communication device (i) generates a receive filter matrix from a signal received by the M plurality of antennas of the second communication device from the first communication device, the receive filter matrix comprised of a plurality of sub-matrices each being a convolution matrix derived from a receive filter sub-vector, wherein each receive filter sub-vector defines one or more complex weights associated with a receive tapped-delay line filter for a corresponding one of the M plurality of antennas;

(ii) computes a principal eigenvector of a product of the receive filter matrix and a Hermitian of the receive filter matrix, the principal eigenvector comprised of a plurality of sub-vectors each having a length corresponding to a number of taps of a transmit tapped-delay line filter associated with a corresponding one of the M plurality of antennas;

(iii) derives from the plurality of sub-vectors of the principal eigenvector a plurality of transmit filter sub-vectors that form a transmit filter vector, each transmit filter sub-vector associated with a corresponding one of M plurality of antennas and defining one or more complex weights associated with the transmit tapped-delay line filter for a corresponding one of the M plurality of antennas; and

(iv) applies the transmit filter vector at the second communication device to a signal to be transmitted from the second communication device to the first communication device.

34. The system of claim 33, wherein the baseband signal processor of the first communication device normalizes each sub-vector of the transmit filter vector so that the total power associated with a transmitted signal is divided equally among the N plurality of antennas.

35. The system of claim 33, wherein the baseband signal processor of the second communication device derives the plurality of transmit filter sub-vectors by computing the norm of each of a plurality of sub-vectors of the principal eigenvector and dividing each sub-vector by the norm and by the square root of M so that the power of the signal transmitted by the second communication device is divided equally among the M plurality of antennas.

36. The system of claim 33, wherein the baseband signal processor of the first communication device (iii) generates a receive filter matrix from signals received by the plurality of antennas of the first communication device from the second communication device, the receive filter matrix comprised of a plurality of sub-matrices each being a convolution matrix derived from a receive filter sub-vector, wherein each sub-vector defines one or more complex weights associated with a receive tapped-delay line filter for a corresponding one of the N plurality of antennas of the first communication device;

(iv) computes a principal eigenvector of a product of the receive filter matrix and a Hermitian of the receive filter matrix, the principal eigenvector comprised of a plurality of sub-vectors each having a length corresponding to the number of taps of the transmit tapped-delay line filter of the first communication device; and

(v) updates from the plurality of sub-vectors of the principal eigenvector the plurality of transmit filter sub-vectors.

37. The system of claim 36, wherein the baseband signal processors of the first and second communication devices repeat the processing steps to update their transmit filter vectors each time signals are received from the other device, to converge to transmit filter vectors that optimize the signal-to-noise ratio of signals communication between them.

38. The system of claim 36, wherein the baseband signal processor of the first communication device updates the transmit filter sub-vectors by equating each transmit filter sub-vector to the corresponding sub-vector of the principal eigenvector.

39. The system of claim 36, wherein the baseband signal processor of the first communication device updates the transmit filter sub-vectors by computing the norm of each of a plurality of sub-vectors of the principal eigenvector and dividing each sub-vector of the principal eigenvector by the norm and by the square root of N.