Compensating for drifts occurring during sleep times in access terminals

• US 8,451,740 B2
• Filed: 03/19/2009
• Issued: 05/28/2013
• Est. Priority Date: 04/01/2008
• Status: Active Grant

• Current Assignee: Qualcomm, Inc.
• Original Assignee: Qualcomm, Inc.
• Inventors: Sampath, Hemanth, Palanki, Ravi, Lin, Jeremy H., Kadous, Tamer A.
• Primary Examiner(s): Pham, Chi
• Assistant Examiner(s): HYUN, SOON D
• Application Number:
  US12/407,467
• Publication Number:
  US 20090245230A1
• Time in Patent Office: 1,531 Days
• Field of Search: None
• US Class Current: 370/252
• CPC Class Codes: H04W 52/0274 by switching on or off the equipment or parts thereof
• CPC Class Codes: Y02D 30/70 in wireless communication networks

Abstract

A method and apparatus are presented for compensating drifts in access terminals occurring during a sleep time. The method includes determining whether a sleep time exceeds a threshold, buffering time domain samples containing acquisition pilots and a paging channel, powering down RF circuitry in the access terminal after buffering samples, processing the samples to compensate for drift, and determining whether the access terminal was paged based upon the processed samples. The apparatus includes a digital front end, an FFT engine coupled to the digital front end, a symbol buffer coupled to the FFT engine, a processor coupled to the digital front end, FFT engine, and symbol buffer, and a memory coupled to the processor, the memory further comprising instructions for executing the method.

Claims

1. A method for compensating drifts occurring during a sleep time in an access terminal, comprising:

determining whether a sleep time exceeds a threshold, and when the sleep time exceeds the threshold;

buffering time domain samples from at least one acquisition or paging channel,

powering down RF circuitry in the access terminal after buffering the time domain samples, and

processing the time domain samples to compensate for drift; and

determining whether the access terminal was paged based upon the processed time domain samples.

2. The method according to claim 1, wherein the time domain samples further comprise acquisition pilots.

3. The method according to claim 2, wherein the paging channel comprises the Quick Paging CHannel (QPCH).

4. The method according to claim 2, wherein determining whether the access terminal was paged further comprises:

demodulating the paging channel; and

determining the terminal was paged based upon the successfully decoding the paging channel.

5. The method according to claim 4, further comprising:

decoding a subsequent page when the page based upon the paging channel is detected.

6. The method according to claim 2, wherein the processing further comprises:

processing TDM 1, 2, 3 samples in a cold start acquisition mode;

determining at least one of time and frequency offset correction values; and

applying the at least one time and frequency offset correction values to the buffered paging channel samples.

7. The method according to claim 6, further comprising:

applying the time correction by determining the starting location of the first OFDM symbol of the paging channel.

8. The method according to claim 6, further comprising:

applying the frequency correction using a time-domain phase ramp corresponding to the determined frequency offset correction value.

9. The method according to claim 1, wherein the time domain samples are buffered in a buffer space which includes at least one of a symbol-RAM, a TCM memory in the processor, and a sample-server.

10. The method according to claim 9, further comprising:

operating an FFT engine in a bypass mode to transfer the time domain samples from the sample server to the symbol-RAM.

11. The method according to claim 2, when it is determined that the sleep time did not exceed the threshold, further comprising:

demodulating the paging channel without buffering and processing of the time domain samples.

12. The method according to claim 11, further comprising;

placing the AT in a sleep state upon detecting that the terminal was not paged after demodulating the paging channel.

13. An apparatus for compensating drifts occurring during a sleep time in an access terminal, comprising:

a digital front end;

an FFT engine coupled to the digital front end;

a symbol buffer coupled to the FFT engine;

a processor coupled to the digital front end, FFT engine, and the symbol buffer;

a memory coupled to the processor, the memory further comprising instructions which

determines whether a sleep time exceeds a threshold, and when the sleep time exceeds the threshold;

buffers time domain samples from at least one acquisition or paging channel, powers down RF circuitry in the access terminal after buffering the time domain samples, and processes the time domain samples to compensate for drift, and

determines whether the access terminal was paged based upon the processed time domain samples.

14. The apparatus according to claim 13, wherein the time domain samples further comprise acquisition pilots.

15. The apparatus according to claim 14, wherein the instructions which determine whether the access terminal was paged comprise further instruction which:

demodulates the paging channel; and

determines whether the terminal was paged based upon the successful demodulating of the paging channel.

16. The apparatus according to claim 15, wherein the memory comprises further instructions which

demodulate a subsequent page when the page based upon the paging channel is detected.

17. The apparatus according to claim 16, wherein the memory comprises further instructions which

process TDM 1, 2, 3 samples in a cold start acquisition mode,

determines at least one of time and frequency offset correction values, and

applies the at least one time and frequency offset correction values to the buffered paging channel samples.

18. The apparatus according to claim 17, wherein the memory comprises further instructions which

applies the time correction by determining the starting location of the first OFDM symbol of the paging channel.

19. The apparatus according to claim 17, wherein the memory comprises further instructions which

applies the frequency correction using a time-domain phase ramp corresponding to the determined frequency offset correction value.

20. An apparatus for compensating drifts occurring during a sleep time in an access terminal, comprising:

means for determining whether a sleep time exceeds a threshold, and when the sleep time exceeds the threshold;

means for buffering time domain samples from at least one acquisition or paging channel,

means for powering down RF circuitry in the access terminal after buffering the time domain samples, and

means for processing the time domain samples to compensate for drift; and

means for determining whether the access terminal was paged based upon the processed time domain samples.

21. The apparatus according to claim 20, wherein the time domain samples further comprise acquisition pilots.

22. The apparatus according to claim 21, wherein the paging channel comprises the Quick Paging CHannel (QPCH).

23. The apparatus according to claim 21, further comprising:

means for demodulating the paging channel; and

means for determining whether the terminal was paged based upon the successful decoding of the paging channel.

24. The apparatus according to claim 23, further comprising;

means for demodulating a subsequent page when the page based upon the paging channel is detected.

25. The apparatus according to claim 22, further comprising:

means for processing TDM 1, 2, 3 samples in a cold start acquisition mode;

means for determining at least one of time and frequency offset correction values; and

means for applying the at least one time and frequency offset correction values to the buffered paging channel samples.

26. A non-transitory computer readable media embodying logic for compensating drifts occurring during a sleep time in an access terminal, the logic configured to perform a method comprising:

determining whether a sleep time exceeds a threshold, and when the sleep time exceeds the threshold,

buffering time domain samples from at least one acquisition or paging channel,

powering down RF circuitry in the access terminal after buffering the time domain samples, and

processing the time domain samples to compensate for drift; and

determining whether the access terminal was paged based upon the processed time domain samples.

27. The non-transitory computer readable media according to claim 26, wherein the time domain samples further comprise acquisition pilots.

28. The non-transitory computer readable media according to claim 27, wherein the paging channel comprises the Quick Paging CHannel (QPCH).

29. The non-transitory computer readable media according to claim 27, comprising additional logic to perform the method further comprising:

demodulating the paging channel; and

determining whether the terminal was paged based upon the successful demodulating of the paging channel.

30. The non-transitory computer readable media according to claim 29, comprising additional logic to perform the method further comprising:

demodulating a subsequent page when the page based upon the paging channel is detected.

31. The non-transitory computer readable media according to claim 28, comprising additional logic to perform the method further comprising:

processing TDM 1, 2, 3 samples in a cold start acquisition mode;

determining at least one of time and frequency offset correction values; and

applying the at least one time and frequency offset correction values to the buffered paging channel samples.

32. A method for compensating drifts occurring during a sleep time in an access terminal, comprising:

determining that a sleep time exceeds a threshold, and when the sleep time exceeds the threshold;

buffering time domain samples containing acquisition pilots and a paging channel; and

processing the time domain samples to compensate for drift.

33. The method according to claim 32, further comprising:

powering down RF circuitry in the access terminal after buffering the time domain samples.

34. The method according to claim 32, further comprising:

determining whether the access terminal was paged based upon the time domain processed samples.

36. The method according to claim 34, wherein the page is sent on a data channel.

35. A method for compensating drifts occurring during a sleep time in an access terminal, comprising:

determining that a sleep time exceeds a threshold;

buffering time domain samples containing acquisition pilots and a paging channel;

processing the time domain samples to compensate for drift;

processing Primary and Secondary Synchronization Signal (PSS and SSS) samples in a cold start acquisition mode;

determining at least one of time and frequency offset correction values; and

applying the at least one time and frequency offset correction values to the buffered paging samples.

37. An apparatus for compensating drifts occurring during a sleep time in an access terminal, comprising:

means for determining that a sleep time exceeds a threshold, and when the sleep time exceeds the threshold;

means for buffering time domain samples containing acquisition pilots and a paging channel; and

means for processing the time domain samples to compensate for drift.

38. The apparatus according to claim 37, further comprising:

means for powering down RF circuitry in the access terminal after buffering the time domain samples.

39. The apparatus according to claim 37, further comprising:

means for determining whether the access terminal was paged based upon the processed time domain samples.

41. The apparatus according to claim 39, wherein the page is sent on a data channel.

40. An apparatus for compensating drifts occurring during a sleep time in an access terminal, comprising:

means for determining that a sleep time exceeds a threshold;

means for buffering time domain samples containing acquisition pilots and a paging channel;

means for processing the time domain samples to compensate for drift;

means for processing Primary and Secondary Synchronization Signal (PSS and SSS) samples in a cold start acquisition mode;

means for determining at least one of time and frequency offset correction values; and

means for applying the at least one time and frequency offset correction values to the buffered paging samples.

42. An apparatus for compensating drifts occurring during a sleep time in an access terminal, comprising:

a digital front end;

an FFT engine coupled to the digital front end;

a symbol buffer coupled to the FFT engine;

a processor coupled to the digital front end, FFT engine, and the symbol buffer;

a memory coupled to the processor, the memory further comprising instructions which

determines that a sleep time exceeds a threshold, and when the sleep time exceeds the threshold;

buffers time domain samples containing acquisition pilots and a paging channel, and

processes the time domain samples to compensate for drift.

43. The apparatus according to claim 42, wherein the memory further comprising instructions which:

power down RF circuitry in the access terminal after buffering the time domain samples.

44. The apparatus according to claim 42, wherein the memory further comprising instructions which:

determine whether the access terminal was paged based upon the processed time domain samples.

46. The apparatus according to claim 44, wherein the page is sent on a data channel.

45. An apparatus for compensating drifts occurring during a sleep time in an access terminal, comprising:

a digital front end;

an FFT engine coupled to the digital front end;

a symbol buffer coupled to the FFT engine;

a processor coupled to the digital front end, FFT engine, and the symbol buffer; and

a memory coupled to the processor, the memory further comprising instructions which

determines that a sleep time exceeds a threshold,

buffers time domain samples containing acquisition pilots and a paging channel,

processes the time domain samples to compensate for drift,

process Primary and Secondary Synchronization Signal (PSS and SSS) samples in a cold start acquisition mode,

determine at least one of time and frequency offset correction values, and

apply the at least one time and frequency offset correction values to the buffered paging samples.

47. A non-transitory computer readable media embodying logic for compensating drifts occurring during a sleep time in an access terminal, the logic configured to perform a method comprising:

determining that a sleep time exceeds a threshold, and when the sleep time exceeds the threshold;

buffering time domain samples containing acquisition pilots and a paging channel; and

processing the time domain samples to compensate for drift.