SYNCHRONIZATION TRANSMISSIONS IN A WIRELESS COMMUNICATION SYSTEM

• US 20110002430A1
• Filed: 10/01/2007
• Published: 01/06/2011
• Est. Priority Date: 10/03/2006
• Status: Active Grant

• Current Assignee: Qualcomm, Inc.
• Original Assignee: Qualcomm, Inc.
• Inventors: Malladi, Durga Prasad, Kim, Byoung-Hoon
• Granted Patent: US 8,509,267 B2
• Time in Patent Office: Days
• US Class Current: 375/362
• CPC Class Codes: H04B 1/7083 Cell search, e.g. using a three-step approach
• CPC Class Codes: H04B 2201/70701 featuring pilot assisted reception
• CPC Class Codes: H04J 11/0069 Cell search, i.e. determining cell identity [cell-ID] design of multiplexing codes H04J13/00; processing access restriction or access information H04W48/16; discovery of network devices for network data management H04W8/005; sounding signals for channel estimation H04L25/0226; structure of reference signals in multicarrier modulation systems H04L27/2613; frame, time or carrier synchronisation in multicarrier modulation systems H04L27/2655
• CPC Class Codes: H04L 5/0007 the frequencies being orthogonal, e.g. OFDM(A), DMT
• CPC Class Codes: H04L 5/0053 Allocation of signaling, i.e. of overhead other than pilot signals

Abstract

To support cell search, multiple (e.g., two) synchronization transmissions are sent in a frame with non-uniform spacing. Information is conveyed via the non-equal distances between consecutive synchronization transmissions. Multiple levels of non-uniform spacing may be used to convey different types of information. In one design, the multiple synchronization transmissions are sent in different subframes of a frame, and each synchronization transmission is sent in one of multiple symbol periods in a respective subframe. The synchronization transmissions may be sent in non-evenly spaced subframes to convey frame boundary. One synchronization transmission may be sent in one of multiple possible symbol periods depending on the information, e.g., a particular group of cell IDs, being conveyed. The distances between synchronization transmissions may also be used to convey cyclic prefix length. A secondary synchronization transmission carrying a cell ID may be sent at a predetermined offset from one of the multiple synchronization transmissions.

Claims

1. An apparatus comprising:

a processor configured to send a first synchronization transmission in a first location of a frame, and to send a second synchronization transmission in a second location of the frame, wherein a first distance between the first and second locations of the frame is different from a second distance between the second location of the frame and the first location of a next frame; and

a memory coupled to the processor.

2. The apparatus of claim 1, wherein the frame comprises a plurality of subframes, wherein the first location is in a first subframe of the frame, and wherein the second location is in a second subframe of the frame, the first and second subframes corresponding to any two of the plurality of subframes in the frame.

3. The apparatus of claim 2, wherein the first subframe is at start of the frame and the second subframe is nearest to but not at middle of the frame.

4. The apparatus of claim 2, wherein a first number of subframes corresponding to the first distance is different from a second number of subframes corresponding to the second distance.

5. The apparatus of claim 2, wherein a plurality of groups of cell identifiers (IDs) are associated with a plurality of symbol periods in the first subframe, and wherein the first location corresponds to one of the plurality of symbol periods in the first subframe.

6. The apparatus of claim 5, wherein the processor is configured to determine a symbol period in the first subframe for the first synchronization transmission based on a group of cell IDs for a cell sending the first and second synchronization transmissions.

7. The apparatus of claim 5, wherein the plurality of groups of cell IDs are associated with a predetermined symbol period in the second subframe.

8. The apparatus of claim 1, wherein the frame comprises a plurality of symbol periods, and wherein the number of symbol periods corresponding to the first distance is one of a plurality of possible numbers of symbol periods for the first distance.

9. The apparatus of claim 1, wherein the processor is configured to generate the first and second synchronization transmissions based on a synchronization sequence derived based on at least one of a CAZAC (constant amplitude zero auto-correlation) sequence, a pseudo-noise (PN) sequence, a Golay sequence, and a Golay complementary sequence.

10. The apparatus of claim 1, wherein the processor is configured to generate the first and second synchronization transmissions based on one of multiple cyclic prefix lengths.

11. The apparatus of claim 1, wherein the processor is configured to send a third synchronization transmission in a third location of the frame, the third location being a predetermined offset from the first location.

12. The apparatus of claim 11, wherein the first and third locations are in adjacent symbol periods.

13. The apparatus of claim 1, wherein the processor is configured to send the first and second synchronization transmissions on a primary synchronization channel (P-SCH).

14. The apparatus of claim 11, wherein the processor is configured to send the third synchronization transmission on a secondary synchronization channel (S-SCH).

15. An apparatus comprising:

a processor configured to send a first primary synchronization code (PSC) on a primary synchronization channel (P-SCH) in a first location of a frame, and to send a second PSC on the P-SCH in a second location of the frame, wherein a first distance between the first and second locations of the frame is different from a second distance between the second location of the frame and the first location of a next frame; and

a memory coupled to the processor.

16. A method comprising:

sending a first synchronization transmission in a first location of a frame; and

sending a second synchronization transmission in a second location of the frame, wherein a first distance between the first and second locations of the frame is different from a second distance between the second location of the frame and the first location of a next frame.

17. The method of claim 16, wherein the frame comprises a plurality of subframes, and wherein a first number of subframes corresponding to the first distance is different from a second number of subframes corresponding to the second distance.

18. The method of claim 17, wherein each subframe comprises a plurality of symbol periods, and wherein the number of symbol periods corresponding to the first distance is one of a plurality of possible numbers of symbol periods for the first distance.

19. The method of claim 16, wherein a plurality of groups of cell identifiers (IDs) are associated with a plurality of possible symbol periods for the first synchronization transmission, and wherein the method further comprises:

determining a symbol period for the first synchronization transmission based on a group of cell IDs for a cell sending the first and second synchronization transmissions.

20. The method of claim 16, further comprising:

sending a third synchronization transmission in a third location of the frame, the third location being a predetermined offset from the first location.

21. An apparatus comprising:

means for sending a first synchronization transmission in a first location of a frame; and

means for sending a second synchronization transmission in a second location of the frame, wherein a first distance between the first and second locations of the frame is different from a second distance between the second location of the frame and the first location of a next frame.

22. The apparatus of claim 21, wherein a plurality of groups of cell identifiers (IDs) are associated with a plurality of possible symbol periods for the first synchronization transmission, and wherein the apparatus further comprises:

means for determining a symbol period for the first synchronization transmission based on a group of cell IDs for a cell sending the first and second synchronization transmissions.

23. The apparatus of claim 21, further comprising:

means for sending a third synchronization transmission in a third location of the frame, the third location being a predetermined offset from the first location.

24. A computer-readable medium including instructions stored thereon, comprising:

a first instruction set for sending a first synchronization transmission in a first location of a frame; and

a second instruction set for sending a second synchronization transmission in a second location of the frame, wherein a first distance between the first and second locations of the frame is different from a second distance between the second location of the frame and the first location of a next frame.

25. The computer-readable medium of claim 24, further comprising:

a third instruction set for sending a third synchronization transmission in a third location of the frame, the third location being a predetermined offset from the first location.

26. An apparatus comprising:

a processor configured to receive a first synchronization transmission in a first location of a frame, to receive a second synchronization transmission in a second location of the frame, to perform detection for the first and second synchronization transmissions, and to determine a first distance between the first and second locations of the frame, the first distance being different from a second distance between the second location of the frame and the first location of a next frame; and

a memory coupled to the processor.

27. The apparatus of claim 26, wherein the processor is configured to correlate input samples with a synchronization sequence to detect for the first and second synchronization transmissions, and to determine the first and second locations based on correlation results.

28. The apparatus of claim 26, wherein the processor is configured to perform correlation for the first and second synchronization transmissions based on a single matched filter.

29. The apparatus of claim 26, wherein the processor is configured to determine frame boundary based on the first distance.

30. The apparatus of claim 26, wherein the processor is configured to determine a group of cell identifiers for a cell sending the first and second synchronization transmissions based on the first distance.

31. The apparatus of claim 26, wherein the processor is configured to determine a cyclic prefix length used by a cell sending the first and second synchronization transmissions based on the first distance.

32. The apparatus of claim 26, wherein the processor is configured to receive a third synchronization transmission in a third location of the frame, the third location being a predetermined offset from the first location.

33. The apparatus of claim 32, wherein the processor is configured to derive a channel estimate based on the first synchronization transmission and to perform coherent detection of the third synchronization transmission based on the channel estimate.

34. The apparatus of claim 32, wherein the processor is configured to determine a group of cell identifiers based on the first distance and to perform correlation for the third synchronization transmission based on the group cell identifiers to obtain a cell identifier for a cell sending the first, second and third synchronization transmissions.

35. A method comprising:

receiving a first synchronization transmission in a first location of a frame;

receiving a second synchronization transmission in a second location of the frame;

performing detection for the first and second synchronization transmissions; and

determining a first distance between the first and second locations of the frame, the first distance being different from a second distance between the second location of the frame and the first location of a next frame.

36. The method of claim 35, further comprising:

determining frame boundary based on the first distance.

37. The method of claim 35, further comprising:

determining a group of cell identifiers for a cell sending the first and second synchronization transmissions based on the first distance.

38. The method of claim 35, further comprising:

determining a cyclic prefix length used by a cell sending the first and second synchronization transmissions based on the first distance.

39. The method of claim 35, further comprising:

receiving a third synchronization transmission in a third location of the frame, the third location being a predetermined offset from the first location;

deriving a channel estimate based on the first synchronization transmission; and

performing coherent detection of the third synchronization transmission based on the channel estimate.

40. An apparatus comprising:

means for receiving a first synchronization transmission in a first location of a frame;

means for receiving a second synchronization transmission in a second location of the frame;

means for performing detection for the first and second synchronization transmissions; and

means for determining a first distance between the first and second locations of the frame, the first distance being different from a second distance between the second location of the frame and the first location of a next frame.

41. The apparatus of claim 40, further comprising:

means for determining frame boundary based on the first distance.

42. The apparatus of claim 40, further comprising:

means for receiving a third synchronization transmission in a third location of the frame, the third location being a predetermined offset from the first location;

means for deriving a channel estimate based on the first synchronization transmission; and

means for performing coherent detection of the third synchronization transmission based on the channel estimate.

43. A computer-readable medium including instructions stored thereon, comprising:

a first instruction set for receiving a first synchronization transmission in a first location of a frame;

a second instruction set for receiving a second synchronization transmission in a second location of the frame;

a third instruction set for performing detection for the first and second synchronization transmissions; and

a fourth instruction set for determining a first distance between the first and second locations of the frame, the first distance being different from a second distance between the second location of the frame and the first location of a next frame.

44. The computer-readable medium of claim 43, and further comprising:

a fifth instruction set for determining frame boundary based on the first distance.

45. An apparatus comprising:

a processor configured to send a primary synchronization transmission in a first location of a frame, the first location being non-overlapping with at least one other location used for at least one other primary synchronization transmission sent by at least one neighboring cell, and to send a secondary synchronization transmission in a second location of the frame; and

a memory coupled to the processor.

46. The apparatus of claim 45, wherein the first location and the at least one other location correspond to different symbol periods of the frame.

47. The apparatus of claim 45, wherein the first and second locations correspond to adjacent symbol periods of the frame.

48. An apparatus comprising:

a processor configured to receive a primary synchronization transmission from a first cell in a first location of a frame, the first location being non-overlapping with at least one other location used for at least one other primary synchronization transmission sent by at least one neighboring cell in a synchronized network, and to receive a secondary synchronization transmission from the first cell in a second location of the frame; and

a memory coupled to the processor.

49. The apparatus of claim 48, wherein the processor is configured to derive a channel estimate for the first cell based on the primary synchronization received from the first cell, and to perform coherent detection of the secondary synchronization transmission received from the first cell based on the channel estimate.

50. The apparatus of claim 48, wherein the processor is configured to receive a second primary synchronization transmission from a second cell in a third location of the frame, the third location being one of the at least one other location, to receive a second secondary synchronization transmission from the second cell in a fourth location of the frame, to derive a second channel estimate for the second cell based on the second primary synchronization received from the second cell;

and to perform coherent detection of the second secondary synchronization transmission received from the second cell based on the second channel estimate.

51. The apparatus of claim 48, wherein the processor is configured to receive primary synchronization transmissions from the first cell and the at least one neighboring cell in a third location of the frame, and to detect for the primary synchronization transmissions received in the third location of the frame.