Estimation of downlink transmission parameters in a radio communications system with an adaptive antenna array

• US 6,738,020 B1
• Filed: 05/21/2002
• Issued: 05/18/2004
• Est. Priority Date: 07/31/2001
• Status: Active Grant

• Current Assignee: Apple Inc.
• Original Assignee: ArrayComm LLC (Ygomi LLC)
• Inventors: Lindskog, Erik D., Trott, Mitchell D., Trigui, Hafedh, de la Barbosa, Serge
• Primary Examiner(s): Tarcza, Thomas H.
• Assistant Examiner(s): ALSOMIRI, ISAM A
• Application Number:
  US10/153,515
• Time in Patent Office: 728 Days
• Field of Search: 342/44, 342/50, 342/174, 342/377, 342/378
• US Class Current: 342/377
• CPC Class Codes: H01Q 3/2605 Array of radiating elements provided with a feedback control over the element weights, e.g. adaptive arrays
• CPC Class Codes: H04B 7/0634 Antenna weights or vector/matrix coefficients
• CPC Class Codes: H04B 7/0643 Feedback on request
• CPC Class Codes: H04W 52/42 in systems with time, space, frequency or polarisation diversity

Abstract

A method and apparatus are provided that allows system calibration to be incorporated into a single function that also derives transmit parameters from receive parameters in a spatial diversity system. In one embodiment, the invention includes receiving signals at an antenna array from a plurality of different locations, deriving characterizations of the spatial parameters of the received signals, receiving measurements of a plurality of different signals transmitted from the antenna array to a plurality of different locations, deriving characterizations of the spatial parameters of the transmitted signals from the received measurements, and generating a transformation function for producing transmit spatial parameters based on measurements of received signals using the receive spatial parameter characterizations and the transmit spatial parameter characterizations.

Claims

1. A method comprising:

receiving signals at an antenna array from a plurality of different locations;

deriving characterizations of the spatial parameters of the received signals;

receiving measurements of a plurality of different signals transmitted from the antenna array to a plurality of different locations;

deriving characterizations of the spatial parameters of the transmitted signals from the received measurements; and

generating a transformation function for producing transmit spatial parameters based on measurements of received signals using the receive spatial parameter characterizations and the transmit spatial parameter characterizations.

2. The method of claim 1, wherein the characterizations of the spatial parameters of the received signals comprise spatial signatures of the received signals, wherein the characterizations of the spatial parameters of the transmitted signals comprise spatial signatures of the transmitted signals, and wherein the transformation function converts a receive spatial signature to a transmit spatial signature.

3. The method of claim 2, further comprising:

receiving traffic from a remote radio;

deriving a received traffic spatial signature for the received traffic;

applying the transformation function to convert the received traffic spatial signature to a transmit traffic spatial signature; and

transmitting traffic to the remote radio using the transmit traffic spatial signature.

4. The method of claim 2, wherein deriving receive spatial signatures comprises measuring relative phase and amplitude at different elements of the antenna array.

5. The method of claim 2, wherein deriving receive spatial signatures comprises rendering the relative phases and amplitudes as a sequence of complex numbers, each complex number corresponding to an element of the antenna array.

6. The method of claim 2, wherein the received signals contain the received measurements and wherein generating a transformation function comprises pairing receive spatial signatures for received signals with transmit spatial signatures for the corresponding received measurements, forming an ordered matrix of receive spatial signatures and a matrix of transmit spatial signatures ordered in accordance with the pairing and solving the matrices for the transformation function.

7. The method of claim 6, wherein solving for the transformation function comprises multiplying the matrix of transmit spatial signatures by the Hermitian of the matrix of receive spatial signatures and multiplying the result by the inverse the product of the matrix of receive spatial signatures and the Hermitian of the matrix of receive spatial signatures.

8. The method of claim 2, further comprising selecting some of the received signals based on a quality measure from among the received signals and wherein deriving receive spatial signatures comprises deriving receive spatial signatures only for the selected signals.

9. The method of claim 8, wherein selecting some of the received signals comprises selecting signals corresponding to a clearer channel and lower mobility.

10. The method of claim 1, wherein the characterizations of the spatial parameters of the received signals comprise covariance matrices of measurements of the received signals, wherein the characterizations of the spatial parameters of the transmitted signals comprise covariance matrices of measurements of the transmitted signals, and wherein the transformation function converts a receive covariance matrix to a transmit covariance matrix.

11. The method of claim 1, wherein the characterizations of the spatial parameters of the received signals comprise eigenvectors based on covariance matrices from the received signals, wherein the characterizations of the spatial parameters of the transmitted signals comprise eigenvectors based on covariance matrices from the transmitted signals, and wherein the transformation function converts a receive eigenvector to a transmit eigenvector.

12. The method of claim 1, wherein the characterizations of the spatial parameters of the received signals comprise weight vectors based on the received signals, wherein the characterizations of the spatial parameters of the transmitted signals comprise weight vectors based on the transmitted signals, and wherein the transformation function converts a receive weight vector to a transmit weight vector.

13. The method of claim 1, wherein receiving signals comprises receiving signals in traffic channels from a plurality of different remote terminals.

14. The method of claim 1, wherein receiving measurements comprises receiving feedback from a plurality of different remote terminals.

15. The method of claim 14, wherein receiving feedback comprises receiving closed loop transmit diversity packets from the remote terminals.

16. The method of claim 15, wherein the closed loop transmit diversity packets are assembled in accordance with a standard for WCDMA (Wideband Code Division Multiple Access).

17. The method of claim 15, wherein receiving feedback comprises receiving power control feedback from the remote terminals.

18. The method of claim 17, wherein the power control feedback is received in packets assembled in accordance with a standard for GSM (Global System for Mobile Communications).

19. The method of claim 1, wherein receiving measurements comprises receiving power measurements of the transmitted signals.

20. A machine-readable medium having stored thereon data representing instructions which, when executed by a machine, cause the machine to perform operations comprising:

receiving signals at an antenna array from a plurality of different locations;

deriving characterizations of the spatial parameters of the received signals;

receiving measurements of a plurality of different signals transmitted from the antenna array to a plurality of different locations;

deriving characterizations of the spatial parameters of the transmitted signals from the received measurements;

generating a transformation function for producing transmit spatial parameters based on measurements of received signals using the receive spatial parameter characterizations and the transmit spatial parameter characterizations.

21. The medium of claim 20, wherein the characterizations of the spatial parameters of the received signals comprise spatial signatures of the received signals, wherein the characterizations of the spatial parameters of the transmitted signals comprise spatial signatures of the transmitted signals, and wherein the transformation function converts a receive spatial signature to a transmit spatial signature.

22. The medium of claim 20, wherein the characterizations of the spatial parameters of the received signals comprise covariance matrices of measurements of the received signals, wherein the characterizations of the spatial parameters of the transmitted signals comprise covariance matrices of measurements of the transmitted signals, and wherein the transformation function converts a receive covariance matrix to a transmit covariance matrix.

23. The medium of claim 20, wherein the characterizations of the spatial parameters of the received signals comprise eigenvectors based on covariance matrices from the received signals, wherein the characterizations of the spatial parameters of the transmitted signals comprise eigenvectors based on covariance matrices from the transmitted signals, and wherein the transformation function converts a receive eigenvector to a transmit eigenvector.

24. The medium of claim 20, wherein the characterizations of the spatial parameters of the received signals comprise weight vectors based on the received signals, wherein the characterizations of the spatial parameters of the transmitted signals comprise weight vectors based on the transmitted signals, and wherein the transformation function converts a receive weight vector to a transmit weight vector.

25. The medium of claim 20, further comprising instructions which, when executed by the machine, cause the machine to perform further operations comprising:

receiving traffic from a remote radio;

deriving a received traffic spatial signature for the received traffic;

applying the transformation function to convert the received traffic spatial signature to a transmit traffic spatial signature; and

transmitting traffic to the remote radio using the transmit traffic spatial signature.

26. The medium of claim 20, wherein the instructions for receiving measurements comprise instructions which, when executed by the machine, cause the machine to perform further operations comprising receiving feedback signals from a plurality of different remote terminals.

27. The medium of claim 20, wherein the instructions for receiving measurements comprise instructions which, when executed by the machine, cause the machine to perform further operations comprising receiving power control feedback from the remote terminals.

28. The medium of claim 20, wherein the received signals contain the received measurements and wherein the instructions for generating a transformation function comprise instructions which, when executed by the machine, cause the machine to perform further operations comprising pairing receive spatial signatures for received signals with transmit spatial signatures for the corresponding received measurements, forming an ordered matrix of received spatial signatures and a matrix of transmit spatial signatures ordered in accordance with the pairing and solving the matrices for the transformation function.

29. An apparatus comprising:

a transmitter to transmit a plurality of different signals to a plurality of different remote locations;

a receiver to receive signals at an antenna array from a plurality of different locations, at least a portion of the received signals including measurements of at least a portion of the different transmitted signals; and

a processor to derive characterizations of the spatial parameters of the received signals,

to receive measurements of the transmitted signals,

to derive characterizations of the spatial parameters of the transmitted signals from the received measurements, and

to generate a transformation function for producing transmit spatial parameters based on measurements of received signals using the receive spatial parameter characterizations and the transmit spatial parameter characterizations.

30. The apparatus of claim 29, wherein the characterizations of the spatial parameters of the received signals comprise spatial signatures of the received signals, wherein the characterizations of the spatial parameters of the transmitted signals comprise spatial signatures of the transmitted signals, and wherein the transformation function converts a receive spatial signature to a transmit spatial signature.

31. The apparatus of claim 29, wherein the receiver further receives traffic from a remote radio;

the processor further derives a received traffic spatial signature for the received traffic and applies the transformation function to convert the received traffic spatial signature to a transmit traffic spatial signature; and

the transmitter further transmits traffic to the remote radio using the transmit traffic spatial signature.

32. The apparatus of claim 29, wherein the received signals are received in traffic channels from a plurality of different remote terminals.

33. The apparatus of claim 29, wherein the received measurements are feedback signals from a plurality of different remote terminals.

34. The apparatus of claim 33, wherein the feedback signals are closed loop transmit diversity packets from the remote terminals.

35. The apparatus of claim 33, wherein the feedback signals are power control feedback from the remote terminals.

36. The apparatus of claim 29, wherein the processor further selects some of the received signals based on a quality measure from among the received signals and wherein the processor deriver spatial signatures only for the selected signals.