Calculating spatial weights in a radio communications system

• US 6,650,881 B1
• Filed: 11/30/2000
• Issued: 11/18/2003
• Est. Priority Date: 11/30/2000
• Status: Active Grant

• Current Assignee: Apple Inc.
• Original Assignee: ArrayComm LLC (Ygomi LLC)
• Inventors: Dogan, Mithat C.
• Primary Examiner(s): VUONG, QUOCHIEN B
• Application Number:
  US09/727,261
• Time in Patent Office: 1,083 Days
• Field of Search: 455/269, 455/272, 455/276.1, 455/67.11, 455/132, 455/561, 455/562.1, 370/252, 370/334, 370/350, 370/516, 375/148, 375/262, 375/267
• US Class Current: 455/276.1
• 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 7/0851 using training sequences or error signal minimizing error signal H04B7/0854
• CPC Class Codes: H04B 7/0854 using error minimizing algorithms, e.g. minimum mean squared error [MMSE], "cross-correlation" or matrix inversion

Abstract

A method and apparatus are provided that allows initial beamforming weights to be determined before timing or delay and frequency offset are known. According to one aspect of the present invention, the invention includes receiving a burst from a terminal at a set of spatial diversity antennas, the burst including a known training sequence and storing measurements of the received burst from each spatial diversity antenna corresponding to receive times within a selected analysis window. The invention further includes determining weights for each diversity antenna for at least a portion of the training sequence of the burst before timing for the burst has been determined, applying the determined weights to the stored measurements and determining timing for the burst based on the stored measurements to which the determined weights have been applied.

Claims

1. A method comprising:

receiving a burst from a terminal at a set of spatial diversity antennas, the burst including a known training sequence;

storing measurements of the received burst from each spatial diversity antenna corresponding to receive times within a selected analysis window;

determining weights for each diversity antenna for at least a portion of the training sequence of the burst before timing for the burst has been determined;

applying the determined weights to the stored measurements; and

determining timing for the burst based on the stored measurements to which the determined weights have been applied.

2. The method of claim 1 wherein determining weights comprises selecting weights that will yield a minimum least squares error for at least a portion of the training sequence of the burst.

3. The method of claim 1 wherein the weights relate to the spatial directionality and interference of the received burst.

4. The method of claim 1 further comprising applying the determined timing to the burst and redetermining weights that will yield a minimum least squares error for the burst using the determined timing.

5. The method of claim 4 further comprising applying the redetermined weights to at least a portion of the burst and redetermining timing using the at least a portion of the burst to which the redetermined weights have been applied.

6. The method of claim 5 further comprising determining frequency offset using the at least a portion of the burst to which the redetermined weights have been applied.

7. The method of claim 5 further comprising applying the redetermined timing to the burst and further determining weights that will yield a minimum least squares error for the burst using the redetermined timing.

8. The method of claim 5 wherein computing a covariance matrix comprises computing a covariance matrix only for a portion of the known training sequence.

9. The method of claim 1 further comprising generating a single representation of the received burst after applying the determined weights.

10. The method of claim 9 wherein determining timing further comprises calculating a cross correlation vector for the plurality of different timing hypotheses for application to the least squares calculation.

11. The method of claim 1 wherein determining the weights comprises computing a covariance matrix against the expected signal.

12. The method of claim 1 wherein determining timing comprises determining a least squares error for a plurality of different timing hypotheses for a portion of the known training sequence.

13. The method of claim 1 wherein determining timing comprises determining timing with respect to a repeated core sequence of the known training sequence and then determining timing with respect to the entire received burst.

14. The method of claim 13 further comprising redetermining weights using the entire received burst after determining timing with respect to the entire received burst.

15. The method of claim 1, wherein the burst is configured in accordance with at least one of a TDMA, a FDMA, a CDMA and a FDD air interface standard.

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

receiving a burst from a terminal at a set of spatial diversity antennas, the burst including a known training sequence;

storing measurements of the received burst from each spatial diversity antenna corresponding to receive times within a selected analysis window;

determining weights for each diversity antenna for at least a portion of the training sequence of the burst before timing for the burst has been determined;

applying the determined weights to the stored measurements; and

determining timing for the burst based on the stored measurements to which the determined weights have been applied.

17. The medium of claim 16 wherein the instructions causing the machine to perform operations comprising determining weights further comprise instructions for selecting weights that will yield a minimum least squares error for at least a portion of the training sequence of the burst.

18. The medium of claim 16 further comprising instructions causing the machine to perform operations comprising applying the determined timing to the burst and redetermining weights that will yield a minimum least squares error for the burst using the determined timing.

19. The medium of claim 18 further comprising instructions causing the machine to perform operations comprising applying the redetermined weights to at least a portion of the burst and redetermining timing using the at least a portion of the burst to which the redetermined weights have been applied.

20. The medium of claim 18 further comprising instructions causing the machine to perform operations comprising determining frequency offset using the at least a portion of the burst to which the redetermined weights have been applied.

21. The medium of claim 18 further comprising instructions causing the machine to perform operations comprising applying the redetermined timing to the burst and further determining weights that will yield a minimum least squares error for the burst using the redetermined timing.

22. The medium of claim 16 wherein the instructions causing the machine to perform operations comprising determining the weights further comprise instructions to compute a covariance matrix against the expected signal for a portion of the known training sequence.

23. The medium of claim 16 wherein the instructions causing the machine to perform operations comprising determining timing further comprise instructions for determining a least squares error for a plurality of different timing hypotheses for a portion of the known training sequence.

24. The medium of claim 16 wherein the instructions causing the machine to perform operations comprising determining timing further comprise instructions for determining timing with respect to a repeated core sequence of the known training sequence and then determining timing with respect to the entire received burst.

25. The medium of claim 16, wherein the burst is configured in accordance with at least one of a TDMA, a FDMA, a CDMA, and a FDD air interface standard.

26. An apparatus comprising:

a set of spatial diversity antennas at a terminal to receive a burst, the burst including a known training sequence;

a memory to store measurements of the received burst from each spatial diversity antenna corresponding to receive times within a selected analysis window;

a processor to determine weights for each diversity antenna for at least a portion of the training sequence of the burst before timing for the burst has been determined to apply the determined weights to the stored measurements, and to determine timing for the burst based on the stored measurements to which the determined weights have been applied.

27. The apparatus of claim 26 wherein the processor further applies the determined timing to the burst and redetermines weights that will yield a minimum least squares error for the burst using the determined timing.

28. The apparatus of claim 27 wherein the processor further applies the redetermined weights to at least a portion of the burst and redetermines timing using the at least a portion of the burst to whichfihe redetermined weights have been applied.

29. The apparatus of claim 27 wherein the processor further determines frequency offset using the at least a portion of the burst to which the redetermined weights have been applied.

30. The apparatus of claim 27 twherein the processor determines timing with respect to a repeated core sequence of the known training sequence and then determines timing with respect to the entire received burst.

31. The apparatus of claim 26, wherein the terminal is within at least one of a TDMA, a FDMA, a CDMA and a FDD radio communications system.