Apparatus and method for beamforming in a changing-interference environment

• US 6,141,567 A
• Filed: 06/07/1999
• Issued: 10/31/2000
• Est. Priority Date: 06/07/1999
• Status: Expired due to Term

• Current Assignee: Intel Corporation
• Original Assignee: ArrayComm LLC (Ygomi LLC)
• Inventors: Youssefmir, Michael, Trott, Mitchell D., Karuppiah, Kamaraj, Petrus, Paul
• Primary Examiner(s): LE, THANH C
• Application Number:
  US09/327,776
• Time in Patent Office: 512 Days
• Field of Search: 455/561, 455/563, 455/276.1, 455/277.1, 455/277.2, 455/278.1, 455/279.1, 455/295, 455/296, 455/304, 455/63, 342/368, 342/372, 342/373, 375/346, 375/347, 375/349, 375/351
• US Class Current: 455/562.1
• CPC Class Codes: H04B 7/0615 of weighted versions of same signal
• CPC Class Codes: H04B 7/0617 for beam forming
• CPC Class Codes: H04B 7/0619 using feedback from receiving side feedback signaling for adaptive modulation/coding H04L1/0001
• CPC Class Codes: H04B 7/0848 Joint weighting
• CPC Class Codes: H04B 7/0851 using training sequences or error signal minimizing error signal H04B7/0854
• CPC Class Codes: H04B 7/086 using weights depending on external parameters, e.g. direction of arrival [DOA], predetermined weights or beamforming
• CPC Class Codes: H04L 25/0204 of multiple channels
• CPC Class Codes: H04L 25/021 Estimation of channel covariance
• CPC Class Codes: H04L 25/03203 Trellis search techniques
• CPC Class Codes: H04L 25/0328 with interference cancellation circuitry adaptations for interference cancellation within a sequence estimator H04L25/03305; interference related aspects of direct sequence spread spectrum H04B1/7097; interference related aspects of frequency hopping spread spectrum H04B1/715; see also H04B1/10
• CPC Class Codes: H04L 25/03299 with noise-whitening circuitry

Abstract

An apparatus and method for adaptively producing transmitted signals and processing received signals in a communication system which includes smart antenna array of antenna elements. When processing received signals, the invention modifies an existing processing scheme by incorporating information about a second set of signals for which training or other characteristic information such as a reference is unknown to information about a first set of signals for which characteristic information such as a reference is known, prior to executing the processing scheme. This approach can be used to modify the receive weights which determine the relative weight assigned to the signals received from each of a plurality of antenna elements to take into account the presence of a changing interference environment. This permits an adaptive updating of the receive weights based on the additional information provided by the second set of data., and may be accomplished faster and with less computational resources than required to determine the weights based on applying the entire processing scheme to the second set of data. In addition, assuming a relationship between the transmit and receive environment, the invention can also be used to modify the transmit weights used by the base station.

Claims

1. A method of determining a smart antenna processing strategy to take into account a changing interference environment, the smart antenna processing strategy applied to a signal for transmission to form a set of antenna element signals to transmit to a remote user from a wireless station that includes an array of antenna elements, or applied to a set of received signals from the set of antenna elements of a wireless station to process the received signals and obtain an estimate of a signal transmitted by a remote user to the wireless station, the method comprising:

(a) providing a process that computes a smart antenna processing strategy as a function of a first set of received data and a reference signal for the first set of received data, the strategy computation process taking into account the interference environment present in the first set of received data;

(b) forming a combination as a function of the first set of received data and a second set of received data, the combination including data incorporating the second set of received data such that the combination takes into account aspects of the interference environment present in the second set of received data and not in the first set of received data; and

(c) computing the smart antenna processing strategy by using the provided computation process with the combination formed in step (b) as input.

2. The method of claim 1,

wherein the strategy computation method has as inputs the reference signal, the first set of received data, and an estimate of one or more characteristic features of the first set of received data,

wherein the step of forming a combination forms a modified feature estimate of at least one of the characteristic features that the computation process has as input such that the modified estimate incorporates an amount of the characteristic feature of the second set of received data into the respective characteristic feature of the first set of received data, and

wherein computing step (c) uses the provided computation process with the first set of received data, the reference signal of the first set of received data, and the modified feature estimate as inputs.

3. The method of claim 2, wherein the amount is an adjustable amount defined by an adjustable parameter.

4. The method of claim 2, wherein the characteristic feature estimate of the first set of received data input in the provided strategy computation process includes an estimate of the covariance of the first set of received data.

5. The method of claim 4, wherein the covariance estimate input in the strategy computation process is represented by a noise-plus-interference-plus-signal covariance estimate.

6. The method of claim 4, wherein the covariance estimate input in the strategy computation process is a noise-plus-interference covariance estimate.

7. The method of claim 4, wherein the combining step (b) includes forming a modified covariance estimate, forming the modified covariance estimate further comprising:

forming a covariance estimate of the first set of received data;

forming a covariance estimate of the second set of received data; and

summing the covariance estimate of the first set of received data and the product of the covariance estimate of the second set of received data and an adjustable parameter.

8. The method of claim 4, wherein the combining step (b) includes forming a modified covariance estimate, the forming the modified covariance estimate further comprising performing a matrix factorization of the primary data, performing a matrix factorization of the secondary data, and combining the resulting factors to form the modified covariance estimate, the relative amount of the factors in the combining defined by an adjustable parameter.

9. The method of claim 1, wherein the strategy computation method implicitly or explicitly uses one or more characteristic features of the first set of received data for interference mitigation, and wherein the step of forming a combination includes:

combining the first set of received data and an amount of a set of supplementary signal data determined from the second set of received data and having at least one characteristic feature substantially the same as the corresponding characteristic feature of the second set of received data.

10. The method of claim 9, wherein the amount is an adjustable amount defined by an adjustable parameter.

11. The method of claim 9, wherein the set of supplementary signal data determined from the second set of received data includes the second set of received data.

12. The method of claim 9, wherein the combining is by forming a sum of the first set of received data and the amount of the set of supplementary signal data determined from the second set of received data.

13. The method of claim 9, wherein the combining includes performing a matrix factorization of the primary and secondary data and combining the resulting factors.

14. The method of claim 1, wherein the first set of received data and second set of received data are received burst-by-burst, and wherein the first set of received data and second set of received data are contained in the same burst of data.

15. The method of claim 1, wherein the first set of received data and second set of received data are received burst-by-burst, and wherein the first set of received data and second set of received data are contained in different bursts of data.

16. The method of claim 1, further comprising the step of:

applying the determined smart antenna processing strategy to process the second set of received data.

17. The method of claim 1, further comprising the step of:

applying the determined smart antenna processing strategy to process a third set of data.

18. The method of claim 1, wherein applying the smart antenna processing strategy includes applying a set of weights, and wherein the smart antenna processing strategy computation process computes the set of weights.

19. The method of claim 1, wherein the first set of received data includes received signal data from when the remote user is transmitting data to the wireless station, such that the smart antenna processing strategy determined in step (c) direct a beam towards the remote user and directs nulls towards interferers that are included in the second set of data.

20. The method of claim 1, wherein the first set of received data includes received signal data from when the reference signal passes a reference signal selection test.

21. The method of claim 1, further including:

(d) providing an iterative strategy computation method that iteratively determines a final antenna processing strategy starting with an initial antenna processing strategy,

wherein the smart antenna processing strategy determined in step (c) is used as the initial antenna processing strategy for the iterative strategy computation method provided in step (d).

22. An apparatus for processing a set of received signals received from an antenna array of a wireless station, the apparatus comprising:

(a) a reference signal processor to provide reference signal data for a first set of received signals;

(b) a combiner to form a combination as a function of the first set of received data and a second set of received data, the combination including data incorporating the second set of received data such that the combination takes into account aspects of the interference environment present in the second set of received data and not in the first set of received data; and

(c) an adaptive smart antenna strategy computation processor configured to compute a smart antenna strategy to apply to the set of received signals to determine an estimate of a user signal transmitted by a remote user or to apply to a signal for transmission to transmit the transmission signal to the remote user, the strategy computation processor having the reference signal data and the combination as inputs.

23. The apparatus of claim 22,

wherein the combiner includes a feature estimator and forms a feature estimate of at least one the characteristic feature of the first set of received data, the feature estimate incorporating an amount of the characteristic feature of the second set of received data into the respective characteristic feature of the first set of received data, and

wherein the strategy computation processor has as inputs the reference signal, the first set of received data, and the feature estimate formed by the combiner.

24. The apparatus of claim 23, wherein the feature estimator includes a covariance estimator for estimating the covariance, and the estimated covariance is coupled to the feature estimate input of the strategy computation processor.

25. The apparatus of claim 24, wherein the covariance estimator determines a noise-plus-interference-plus-signal covariance estimate coupled to the feature estimate input of the strategy computation processor.

26. The apparatus of claim 24, wherein the covariance wherein the covariance estimator determines a noise-plus-interference covariance estimate coupled to the feature estimate input of the strategy computation processor.

27. The apparatus of claim 24, wherein the combiner is further configured to implement:

a first covariance estimator having as input the first set of received data;

a second covariance estimator having as input the second set of received data; and

a summer to sum the covariance estimate of the first set of received data output by the first covariance estimator and the product of the covariance estimate of the second set of received data output by the first covariance estimator and an adjustable parameter, the summer forming a covariance estimate, the covariance estimate coupled to the feature estimate input of the strategy computation processor.

28. The apparatus of claim 24, wherein the combiner is further configured to form as output a modified covariance estimate, the modified covariance estimate forming including performing a matrix factorization of the primary data, performing a matrix factorization of the secondary data, and combining the resulting factors to form the modified covariance estimate, the relative amount of the factors in the combining defined by an adjustable parameter, the modified covariance estimate output coupled to the feature estimate input of the strategy computation processor.

29. The apparatus of claim 23, wherein the amount is an adjustable amount defined by an adjustable parameter.

30. The apparatus of claim 22, wherein the strategy computation processor implicitly or explicitly uses one or more characteristic features of the first set of received data for interference mitigation, and wherein is configured to combine the first set of received data and an amount of a set of supplementary signal data determined from the second set of received data and having at least one characteristic feature substantially the same as the corresponding characteristic feature of the second set of received data.

31. The apparatus of claim 30, wherein the amount is an adjustable amount defined by an adjustable parameter.

32. The apparatus of claim 30, wherein the set of supplementary signal data determined by the combiner from the second set of received data includes the second set of received data.

33. The apparatus of claim 30, wherein the combiner is further configured to forming a sum of the first set of received data and the amount of the set of supplementary signal data determined from the second set of received data.

34. The apparatus of claim 30, wherein the combiner is further configured to perform a matrix factorization of the primary and secondary data and to combining the resulting factors.

35. The apparatus of claim 22, wherein the first set of received data and second set of received data are received burst-by-burst, and wherein the first set of received data and second set of received data are contained in the same burst of data.

36. The apparatus of claim 22, wherein the first set of received data and second set of received data are received burst-by-burst, and wherein the first set of received data and second set of received data are contained in different bursts of data.

37. The apparatus of claim 22, wherein the determined smart antenna processing strategy is applied to process the second set of received data.

38. The apparatus of claim 22, wherein the determined smart antenna processing strategy is applied to process a third set of data.

39. The apparatus of claim 22, further comprising:

(d) a transmit signal circuit for forming a transmit strategy from the determined smart antenna processing strategy and from calibration data, the calibration data accounting for differences in the receive and transmit electronic paths for the different antenna elements.

40. The apparatus of claim 22, wherein applying the smart antenna processing strategy includes applying a set of weights, and wherein the strategy computation processor computes the set of weights.

41. An apparatus for processing a set of received signals received from an antenna array of a wireless station, the apparatus comprising:

(a) means for providing reference signal data for a first set of received signals;

(b) means for forming a combination as a function of the first set of received data and a second set of received data, the combination including data incorporating the second set of received data such that the combination takes into account aspects of the interference environment present in the second set of received data and not in the first set of received data; and

(c) means for computing an adaptive smart antenna strategy to apply to the set of received signals to determine an estimate of a user signal transmitted by a remote user or to apply to a signal for transmission to transmit the transmission signal to the remote user, the strategy computation processor having the reference signal data and the combination as inputs.