Methods and apparatus relating to timing and/or synchronization including the use of wireless terminals beacon signals

• US 8,743,843 B2
• Filed: 01/10/2007
• Issued: 06/03/2014
• Est. Priority Date: 01/11/2006
• Status: Active Grant

• Current Assignee: Qualcomm, Inc.
• Original Assignee: Qualcomm, Inc.
• Inventors: Laroia, Rajiv, Rangan, Sundeep, Das, Arnab, Lane, Frank A., Li, Junyi
• Primary Examiner(s): Bost, Dwayne
• Assistant Examiner(s): Johnson, Gerald
• Application Number:
  US11/621,957
• Publication Number:
  US 20070201423A1
• Time in Patent Office: 2,701 Days
• Field of Search: 370/336, 370/338, 370/432, 455/574
• US Class Current: 370/336
• CPC Class Codes: H04J 3/0602 Systems characterised by the synchronising information used
• CPC Class Codes: H04L 27/2601 Multicarrier modulation systems
• CPC Class Codes: H04L 27/261 Details of reference signals
• CPC Class Codes: H04L 5/0016 Time-frequency-code
• CPC Class Codes: H04L 5/0035 Resource allocation in a cooperative multipoint environment
• CPC Class Codes: H04L 5/0048 Allocation of pilot signals, i.e. of signals known to the receiver
• CPC Class Codes: H04W 16/14 Spectrum sharing arrangements between different networks
• CPC Class Codes: H04W 28/04 Error control
• CPC Class Codes: H04W 28/18 Negotiating wireless communication parameters
• CPC Class Codes: H04W 36/16 Performing reselection for specific purposes
• CPC Class Codes: H04W 36/24 Reselection being triggered by specific parameters
• CPC Class Codes: H04W 40/24 Connectivity information management, e.g. connectivity discovery or connectivity update
• CPC Class Codes: H04W 40/244 using a network of reference devices, e.g. beaconing
• CPC Class Codes: H04W 48/08 Access restriction or access information delivery, e.g. discovery data delivery signalling during connection H04W76/00
• CPC Class Codes: H04W 48/16 Discovering, processing access restriction or access information
• CPC Class Codes: H04W 48/20 Selecting an access point
• CPC Class Codes: H04W 52/0229 where the received signal is a wanted signal
• CPC Class Codes: H04W 52/04 TPC
• CPC Class Codes: H04W 72/02 Selection of wireless resources by user or terminal
• CPC Class Codes: H04W 76/14 Direct-mode setup
• CPC Class Codes: H04W 8/005 : Discovery of network devices, e.g. terminals
• CPC Class Codes: H04W 84/042 : Public Land Mobile systems, e.g. cellular systems
• CPC Class Codes: H04W 84/18 : Self-organising networks, e.g. ad-hoc networks or sensor networks
• CPC Class Codes: H04W 88/02 : Terminal devices
• CPC Class Codes: H04W 88/04 : adapted for relaying to or from another terminal or user
• CPC Class Codes: H04W 88/06 : adapted for operation in multiple networks or having at least two operational modes, e.g. multi-mode terminals
• CPC Class Codes: H04W 88/10 : adapted for operation in multiple networks, e.g. multi-mode access points
• CPC Class Codes: Y02D 30/70 : in wireless communication networks

Abstract

Wireless terminal beacon signaling is used to achieve timing synchronization between two wireless terminals in a wireless communication system, e.g., in an ad hoc network lacking a centralized timing reference. An exemplary timing structure used by an individual wireless terminal includes a beacon transmission time interval, a beacon monitoring time interval and a silence time interval. A first wireless terminal monitoring for beacon signals from other wireless terminals, detects a beacon signal portion from a second wireless terminal and determines a timing adjustment as a function of the detected beacon signal portion. The first wireless terminal applies the determined timing adjustment, e.g., time shifting its timing structure, such that its beacon signal can be detected by the second wireless terminal. Implementation of the determined timing adjustment sets the timing structures of the two wireless terminals to have a fixed relationship thereby allowing for coordinated communications including a peer-to-peer communications session.

Claims

1. A method of operating a communications device, the method comprising:

during a beacon receive time period performing a beacon signal detection operation to detect receipt of at least a portion of a beacon signal; and

transmitting beacon signal bursts, each beacon signal burst including a first beacon symbol and a second beacon symbol; and

varying an amount of time between successive transmitted beacon signal bursts in accordance with a predetermined time varying sequence used to control spacing between successively transmitted beacon signal bursts;

wherein each beacon symbol corresponds to a beacon symbol transmission time period;

wherein each beacon signal burst corresponds to multiple beacon symbol transmission time periods; and

wherein transmitting beacon signal bursts includes transmitting beacon signal bursts in which a majority of beacon symbol transmission time periods available during the transmitted beacon signal bursts are left unused.

2. The method of claim 1 wherein the beacon receive time period is longer than a beacon transmission time period in which one of said beacon signal bursts is transmitted.

3. The method of claim 2,

wherein beacon symbols in individual beacon signal bursts occupy less than 10% of available beacon symbol transmission units included in the individual beacon signal burst;

wherein the beacon receive and beacon transmission time periods are non-overlapping and

wherein the beacon receive time period is at least two times the beacon transmit period in duration.

4. The method of claim 3, further comprising:

during a silence period occurring between said beacon receive and beacon transmission time periods neither transmitting nor operating to detect beacon signals.

5. The method of claim 4, wherein the silence period is at least twice one of the beacon transmission time period and beacon receive time period.

6. The method of claim 2, further comprising:

adjusting communications device transmission time based on a detected portion of a received beacon signal; and

transmitting a signal in accordance with said adjusted communications device transmission timing.

7. The method of claim 6, wherein said transmitted signal is a beacon signal.

8. The method of claim 7, wherein said timing adjustment adjusts the beacon signal transmission time period to occur during a period of time known to be used by the device which transmitted the received beacon signal portion to receive beacon signals.

9. The method of claim 7, further comprising:

establishing a communications session with the device from which said detected portion of a beacon signal was received.

10. The method of claim 9 further comprising:

repeating said beacon transmission and detection operations during said established communications session.

11. The method of claim 1, further comprising:

pseudo randomly adjusting the start of at least one of said beacon transmission time period and said beacon receive time period in a recurring sequence of such time periods.

12. The method of claim 1,

wherein said communications device is a mobile wireless terminal;

and

wherein said receive and transmission time periods occur on a periodic basis.

50. The method of claim 1, wherein adjusting pseudo-randomly the receive time period or the beacon transmission time period includes:

adjusting pseudo-randomly the beacon transmission time period.

51. The method of claim 1, further comprising:

varying the duration of transmitted beacon signal bursts in accordance with a predetermined pattern.

52. The method of claim 51, wherein said predetermined pattern is a function of a wireless terminal identifier corresponding to said communications device.

53. The method of claim 1,

wherein said step of varying an amount of time between successive transmitted beacon signal bursts in accordance with a predetermined time varying sequence is performed during an active mode of communications device operation;

and

wherein said method further comprises;

varying, during an inactive mode of commutations device operation, the amount of time between successive transmitted beacon signal bursts in accordance with said predetermined time varying sequence.

54. The method of claim 1,

wherein said step of varying an amount of time between successive transmitted beacon signal bursts in accordance with a predetermined time varying sequence is performed during an active mode of communications device operation;

and

wherein said method further comprises;

varying, during an inactive mode of commutations device operation the amount of time between successive transmitted beacon signal bursts in accordance with a second time varying sequence, said second time varying sequence being different from said first time varying sequence.

55. The method of claim 51, wherein said predetermined pattern is the same for different communications devices in a communications system in which said communications device operates.

56. The method of claim 3, wherein the majority of available beacon symbol transmission units included in the individual beacon signal burst are left unused.

57. The method of claim 1, wherein transmitting beacon signal bursts, includes transmitting a beacon signal burst in which a majority of beacon symbol transmission units available during the beacon signal burst are left unused.

58. The method of claim 1,

wherein performing a beacon signal detection operation to detect receipt of at least a portion of a beacon signal includes performing a beacon signal burst detection operation.

59. The method of claim 1, wherein said beacon symbol has a longer duration than OFDM symbols used by said communications device to transmit user data.

13. A communications device comprising:

a beacon signal detection module for performing a beacon signal detection operation during a beacon receive time period to detect receipt of at least a portion of a beacon signal; and

a transmission module for transmitting beacon signal bursts, each beacon signal burst including a first beacon symbol and a second beacon symbol; and

a transmission control module for varying an amount of time between successive transmitted beacon signal bursts in accordance with a predetermined time varying sequence used to control spacing between successively transmitted beacon signal bursts,

wherein each beacon symbol corresponds to a beacon symbol transmission time period;

wherein each beacon signal burst corresponds to multiple beacon symbol transmission time periods; and

wherein transmitting beacon signal bursts includes transmitting beacon signal bursts in which a majority of beacon symbol transmission time periods available during the transmitted beacon signal bursts are left unused.

14. The communications device of claim 13 wherein the beacon receive time period is longer than a beacon transmission time period in which one of said beacon signal bursts is transmitted.

15. The communications device of claim 14,

wherein beacon symbols in individual beacon signal bursts occupy less than 10% of available beacon symbol transmission units included in the individual beacon signal burst;

wherein the beacon receive and beacon transmission time periods are non-overlapping; and

wherein the beacon receive time period is at least two times the beacon transmit period in duration.

16. The communications device of claim 15, wherein said communications device is part of a time division duplex OFDM wireless communications system supporting peer-peer direct communications.

17. The communications device of claim 15, further comprising:

a silence state control module, for controlling wireless terminal operation during a silence period occurring between said beacon receive and beacon transmission time periods, to neither transmit nor operate to detect beacon signals.

18. The communications device of claim 17, wherein the silence period is at least twice one of the beacon transmission time period and beacon receive time period.

19. The communications device of claim 14, further comprising:

a transmission time adjustment module for adjusting the communications device'"'"'s transmission time based on a detected portion of a received beacon signal;

wherein said transmission control module controls said transmission module to transmit a signal in accordance with said adjusted communications device transmission timing; and

an adjustment module for adjusting pseudo-randomly the device'"'"'s transmission time period.

20. The communications device of claim 19, wherein said transmitted signal is a beacon signal.

21. The communications device of claim 20, wherein said transmission time adjustment module adjustment adjusts the beacon signal transmission time period to occur during a period of time known to be used by the device which transmitted the received beacon signal portion to receive beacon signals.

22. The communications device of claim 20, further comprising:

a communication session initiation module for establishing a communications session with the device from which said detected portion of a beacon signal was received.

23. The communications device of claim 22 further comprising:

a beacon detection control module for controlling said beacon detection module operation; and

memory including stored communication session state information, and wherein when said communications session state information indicates that the established communications session is ongoing, said transmission control module controls said transmission module to repeat said beacon transmission operation and said beacon detection control module controls said beacon signal detection module to repeat said beacon detection operations.

24. The communications device of claim 13, further comprising:

a timing adjustment module for pseudo randomly adjusting the start of at least one of said beacon transmission time period and said beacon receive time period in a recurring sequence of such time periods.

25. The communications device of claim 13, wherein said receive and transmission time periods occur on a periodic basis.

26. The communications device of claim 13, further comprising:

a battery for powering said communications device.

27. The communications device of claim 26, wherein said transmission module is an OFDM transmitter.

28. The communications device of claim 26, further comprising:

a mode control module for controlling the communications device to operate, during different times, in a first and second mode of operation in which the communications device transmits beacon signals,

wherein said first mode is an inactive mode in which the communications device transmits beacon signals, operates to detect beacon signals, but is restricted from transmitting user data; and

wherein said second mode is an active mode in which the communications device transmits beacon signals, operates to detect beacon signals, and is permitted to transmit user data.

29. A communications device comprising:

means for performing a beacon signal detection operation during a beacon receive time period to detect receipt of at least a portion of a beacon signal; and

means for transmitting beacon signal bursts, each beacon signal burst including a first beacon symbol and a second beacon symbol; and

means for varying an amount of time between successive transmitted beacon signal bursts in accordance with a predetermined time varying sequence used to control spacing between successively transmitted beacon signal bursts;

wherein each beacon symbol corresponds to a beacon symbol transmission time period;

wherein each beacon signal burst corresponds to multiple beacon symbol transmission time periods; and

wherein transmitting beacon signal bursts includes transmitting beacon signal bursts in which a majority of beacon symbol transmission time periods available during the transmitted beacon signal bursts are left unused.

30. The communications device of claim 29 wherein the beacon receive time period is longer than a beacon transmission time period in which one of said beacon signal bursts is transmitted.

31. The communications device of claim 30,

wherein beacon symbols in individual beacon signal bursts occupy less than 10% of available beacon symbol transmission units included in the individual beacon signal burst;

wherein the beacon receive and beacon transmission time periods are non-overlapping; and

wherein the beacon receive time period is at least two times the beacon transmit period in duration.

32. The communications device of claim 31, wherein said communications device is part of a time division duplex OFDM wireless communications system supporting peer-peer direct communications.

33. The communications device of claim 31, further comprising:

means for controlling wireless terminal operation during a silence period occurring between said beacon receive and beacon transmission time periods, to neither transmit nor operate to detect beacon signals.

34. The communications device of claim 33, wherein the silence period is at least twice one of the beacon transmission time period and beacon receive time period.

35. The communications device of claim 30, further comprising:

means for adjusting the communications device'"'"'s transmission time based on a detected portion of a received beacon signal; and

means for controlling said means for transmitting to transmit a signal in accordance with said adjusted communications device transmission timing.

36. The communications device of claim 35, wherein said transmitted signal is a beacon signal.

37. The communications device of claim 36, wherein said means for adjusting the communications device'"'"'s transmission time adjusts the beacon signal transmission time period to occur during a period of time known to be used by the device which transmitted the received beacon signal portion to receive beacon signals.

38. A non-transitory computer readable medium embodying machine executable instruction for controlling a communications device to implement a method, the method comprising:

during a beacon receive time period performing a beacon signal detection operation to detect receipt of at least a portion of a beacon signal;

transmitting beacon signal bursts, each beacon signal burst including a first beacon symbol and a second beacon symbol; and

varying an amount of time between successive transmitted beacon signal bursts in accordance with a predetermined time varying sequence used to control spacing between successively transmitted beacon signal bursts;

wherein each beacon symbol corresponds to a beacon symbol transmission time period;

wherein each beacon signal burst corresponds to multiple beacon symbol transmission time periods; and

wherein transmitting beacon signal bursts includes transmitting beacon signal bursts in which a majority of beacon symbol transmission time periods available during the transmitted beacon signal bursts are left unused.

39. The non-transitory computer readable medium of claim 38 wherein the beacon receive time period is longer than a beacon transmission time period in which one of said beacon signal bursts is transmitted.

40. The non-transitory computer readable medium of claim 39,

wherein beacon symbols in individual beacon signal bursts occupy less than 10% of available beacon symbol transmission units included in the individual beacon signal burst;

wherein the beacon receive and beacon transmission time periods are non-overlapping; and

wherein the beacon receive time period is at least two times the beacon transmit period in duration.

41. The non-transitory computer readable medium of claim 40, further embodying machine executable instructions for:

during a silence period occurring between said beacon receive and beacon transmission time periods neither transmitting nor operating to detect beacon signals.

42. The non-transitory computer readable medium of claim 41, wherein the silence period is at least twice one of the beacon transmission time period and beacon receive time period.

43. The non-transitory computer readable medium of claim 39, further embodying machine executable instructions for:

adjusting communications device transmission time based on a detected portion of a received beacon signal; and

transmitting a signal in accordance with said adjusted communications device transmission timing.

44. An apparatus comprising:

a processor configured to;

perform a beacon signal detection operation to detect receipt of at least a portion of a beacon signal during a beacon receive time period; and

control transmission of beacon signal bursts, each beacon signal burst including a beacon symbol; and

varying an amount of time between successive transmitted beacon signal bursts in accordance with a predetermined time varying sequence used to control spacing between successively transmitted beacon signal bursts;

wherein each beacon symbol corresponds to a beacon symbol transmission time period;

wherein each beacon signal burst corresponds to multiple beacon symbol transmission time periods; and

wherein said processor is further configured to, as part of transmitting beacon signal bursts, transmit beacon signal bursts in which a majority of beacon symbol transmission time periods available during the transmitted beacon signal bursts are left unused.

45. The communications device of claim 44 wherein said processor is further configured to:

control the beacon receive time period to be longer than a beacon transmission time period in which one of said beacon signal bursts is transmitted.

46. The apparatus of claim 45, wherein beacon symbols in individual beacon signal bursts occupy less than 10% of available beacon symbol transmission units included in the individual beacon signal burst;

and

wherein said processor is further configured to;

control the beacon receive and beacon transmission time periods to be non-overlapping; and

to control the beacon receive time period to be at least two times the beacon transmit period in duration.

49. The apparatus of claim 45, wherein said processor is further configured to:

adjust communications device transmission time based on a detected portion of a received beacon signal; and

control transmission of a signal in accordance with said adjusted communications device transmission timing.

47. The apparatus of 46, wherein said processor is further configured to:

neither control transmission of beacon signals nor operate to detect beacon signals during a silence period occurring between said beacon receive and beacon transmission time periods.

48. The apparatus of claim 47, wherein said processor is further configured to:

control the silence period to be at least twice one of the beacon transmission time period and beacon receive time period.