Method and apparatus for processing signals received from a channel having a variable channel length

1. A method comprising:

receiving a wireless signal at a wireless channel estimator;

receiving the wireless signal at a wireless channel length determination unit,

wherein each of the channel estimator and the channel length determination unit independently receive the wireless signal;

determining a first channel estimate for a communication channel based on a first channel length and the wireless signal at the channel estimator; and

determining a second channel length that optimizes a channel estimation quality criterion using the first channel estimate and the independently received wireless signal at the channel length determination unit.

2. The method of claim 1 further comprising:

determining a second channel estimate for the communication channel based on the second channel length at the channel estimator.

3. The method of claim 2 wherein determining the second channel length includes iterating through a plurality of channel lengths to identify a channel length that optimizes the channel estimation quality criterion.

4. The method of claim 2 wherein the first channel length is a maximum expected channel length of the communication channel.

5. The method of claim 2 wherein determining the second channel length includes estimating channel tap variances using the first channel estimate.

6. The method of claim 2 wherein determining the second channel length includes estimating input noise associated with the communication channel.

7. The method of claim 2 wherein determining the second channel length includes determining a combination of channel length and sample timing values that optimize the channel estimation quality criterion.

8. The method of claim 2 wherein determining the second channel length includes iterating combinations of channel length and sample timing values to optimize the channel estimation quality criterion.

9. The method of claim 2 wherein determining the first channel estimate for the communication channel includes using a training sequence received from the communication channel and determining the second channel estimate for the communication channel includes using the training sequence received from the communication channel.

10. The method of claim 2 wherein the channel estimation quality criterion is based on a channel estimation error.

11. A system comprising:

a wireless channel estimator that receives a wireless signal; and

a wireless channel length determination unit that receives the wireless signal,

wherein each of the channel estimator and the channel length determination unit independently receive the wireless signal;

wherein the channel estimator determines a first channel estimate for a communication channel based on a first channel length and the wireless signal; and

wherein the channel length determination unit determines a second channel length that optimizes a channel estimation quality criterion using the first channel estimate and the wireless signal.

12. The system of claim 11 wherein the channel estimator determines a second channel estimate for a communication channel based on the second channel length.

13. The system of claim 11 wherein the channel length determination unit iterates through a plurality of channel lengths to identify a channel length that optimizes the channel estimation quality criterion.

14. The system of claim 11 wherein the first channel length is a maximum expected channel length of the communication channel.

15. The system of claim 11 wherein the channel length determination unit determines the second channel length by estimating channel tap variances using the first channel estimate.

16. The system of claim 11 wherein the channel length determination unit determines the second channel length by estimating input noise associated with the communication channel.

17. The system of claim 11 wherein the channel length determination unit determines the second channel length by determining channel length and sample timing values that optimize the channel estimation quality criterion.

18. The system of claim 11 wherein the channel length determination unit determines the second channel length by iterating channel length and sample timing values to optimize the channel estimation quality criterion.

19. The system of claim 11 wherein determining the first channel estimate for the communication channel includes using a training sequence received from the communication channel and determining the second channel estimate for the communication channel includes using the training sequence received from the communication channel.

20. The system of claim 11 wherein the channel estimation quality criterion is based on a channel estimation error.

21. A method comprising:

independently receiving a wireless signal at each of a channel estimator and a channel length determination unit;

determining a first channel estimate for a communication channel based on a first channel length and the received wireless signal at the channel estimator; and

estimating channel tap variances for the communication channel using the first channel estimate, the independently received wireless signal, and a plurality of previous channel estimates at the channel length determination unit.

22. The method of claim 21 further comprising:

estimating noise power for the communication channel using the first channel estimate at the channel length determination unit; and

determining, using the estimated channel tap variances and the noise power, a value for at least one channel related parameter that optimizes a channel estimation quality criterion at the channel length determination unit, wherein the at least one channel related parameter includes channel length.

23. The method of claim 22 further comprising:

determining a second channel estimate based on the value of the at least one channel related parameter at the channel estimator, wherein determining a value includes iterating through

a plurality of channel length values to find a channel length value to optimize channel estimation quality.

24. The method of claim 21 wherein said first channel length is a maximum expected channel length of the communication channel.

25. The method of claim 21 wherein estimating the channel tap variances includes estimating variances using channel estimates corresponding to N most recent time frames in a time division multiple access (TDMA) system, and wherein the channel estimates are based on the first channel length, wherein N is an integer greater than one.

26. The method of claim 24 wherein determining the at least one channel related parameter value includes determining channel length and sample timing values that optimize the channel estimation quality criterion.

27. A system comprising:

a channel estimator that receives a wireless signal and determines a first channel estimate for the communication channel based on a first channel length and the received wireless signal; and

a channel length determination unit that independently receives the wireless signal, and that estimates channel tap variances for the communication channel using the first channel estimate, the independently received wireless signal, and a plurality of previous channel estimates.

28. The system of claim 27 wherein the channel length determination unit estimates noise power for the communication channel using the first channel estimate.

29. The system of claim 28 wherein the channel length determination unit determines a value for at least one channel related parameter that optimizes a channel estimation quality criterion based on the estimated channel tap variances and the noise power, and wherein the at least one channel related parameter includes channel length.

30. The system of claim 29 wherein the channel estimator determines a second channel estimate based on the value of the at least one channel related parameter,

wherein the channel determination unit determines the value by iterating through a plurality of channel length values to find a channel length value that optimizes channel estimation quality.

31. The system of claim 27 wherein the first channel length is a maximum expected channel length of the communication channel.

32. The system of claim 27 wherein the channel determination unit estimates the channel tap variances by estimating variances using channel estimates corresponding to N most recent time frames in a time division multiple access (TDMA) system, wherein the channel estimates are based on the first channel length, and wherein N is an integer greater than one.

33. The system of claim 29 wherein the channel determination unit determines the at least one channel related parameter value by determining channel length and sample timing values that optimize the channel estimation quality criterion.