MINIMIZING THE IMPACT OF SELF SYNCHRONIZATION ON WIRELESS COMMUNICATION DEVICES

• US 20100260169A1
• Filed: 04/06/2010
• Published: 10/14/2010
• Est. Priority Date: 04/08/2009
• Status: Active Grant

• Current Assignee: Qualcomm, Inc.
• Original Assignee: Qualcomm, Inc.
• Inventors: Palanki, Ravi, Gheorghiu, Valentin A.
• Granted Patent: US 8,730,938 B2
• Time in Patent Office: Days
• US Class Current: 370/350
• CPC Class Codes: H04J 3/0638 Clock or time synchronisation among nodes; Internode synchronisation synchronization for ring networks H04L12/422; data switching networks with synchronous transmission H04L12/43
• CPC Class Codes: H04W 56/0015 one node acting as a reference for the others
• CPC Class Codes: H04W 56/002 Mutual synchronization

Abstract

A method for self synchronization by a base station is described. Network information is sent to a wireless communication device. The network information indicates a first time period. The first time period is a period of silence by the base station. Synchronization signals are monitored during the first time period. Monitoring synchronization signals includes not transmitting.

Claims

1. A method for self synchronization by a base station, comprising:

sending network information to a wireless communication device, wherein the network information indicates a first time period, wherein the first time period is a period of silence by the base station; and

monitoring synchronization signals during the first time period, wherein monitoring synchronization signals comprises not transmitting.

2. The method of claim 1, wherein the base station has a current stratum, and further comprising transmitting synchronization signals in a second time period, wherein the second time period comprises slots designated for base stations having a stratum less than or equal to the current stratum to transmit synchronization signals.

3. The method of claim 1, wherein the first time period comprises slots designated for base stations having a stratum less than or equal to the current stratum to monitor synchronization signals.

4. The method of claim 1, wherein the network information comprises a multimedia broadcast single frequency network (MBSFN) subframe declaration.

5. The method of claim 4, further comprising receiving a common reference signal (CRS) from a synchronizing node, wherein the base station uses the CRS for tracking.

6. The method of claim 4, wherein the base station has a current stratum, and further comprising transmitting a common reference signal (CRS) in subframes declared as MBSFN for a stratum greater the current stratum, wherein the subframes declared as MBSFN comprise a second time period.

7. The method of claim 4, wherein the base station has a current stratum, and further comprising tracking a common reference signal (CRS) in subframes declared as MBSFN for a stratum less than or equal to the current stratum.

8. The method of claim 1, further comprising:

searching for a synchronization signal;

determining whether the synchronization signal has been acquired; and

determining a current stratum based on the synchronization signal if the synchronization signal has been acquired.

9. The method of claim 1, wherein the network information comprises a message instructing the one or more wireless communication devices to enter a discontinuous receive (DRX) mode during the period of silence.

10. The method of claim 9, wherein the network information comprises a sleep time for the wireless communication device.

11. The method of claim 1, wherein the network information comprises identifying one or more subframes when the base station performs self synchronization.

12. The method of claim 1, wherein the network information comprises a subframe index, wherein the subframe index implicitly indicates one or more subframes when the base station performs self synchronization.

13. The method of claim 1, wherein the synchronization signals are sent by a synchronization source.

14. The method of claim 1, wherein monitoring synchronization signals comprises time-tracking a synchronization source.

15. The method of claim 14, further comprising performing frequency error correction while time-tracking the synchronization source.

16. The method of claim 1, wherein sending the network information comprises gradually decreasing power and then gradually increasing the power to mimic a deep fade.

17. The method of claim 1, wherein the network information comprises scheduling information, and wherein the scheduling information comprises no scheduled transmissions to the wireless communication device in and around subframes where no common reference signal (CRS) is transmitted.

18. The method of claim 1, wherein sending the network information comprises simultaneously transmitting a common reference signal (CRS) to the wireless communication device while achieving self synchronization using a Primary Synchronization Signal (PSS) on the last two orthogonal frequency division multiplexing (OFDM) symbols of a slot.

19. The method of claim 1, wherein sending the network information comprises simultaneously transmitting a common reference signal (CRS) to the wireless communication device while achieving self synchronization using a Secondary Synchronization Signal (SSS) on the last two orthogonal frequency division multiplexing (OFDM) symbols of a slot.

20. The method of claim 1, wherein the base station is a home evolved NodeB (HeNB).

21. The method of claim 1, wherein the wireless communication device is legacy user equipment (UE).

22. The method of claim 1, wherein the period of silence is coordinated by a network.

44. The wireless device of claim 1, wherein the period of silence is coordinated by a network.

23. A wireless device configured for self synchronization, comprising:

a processor;

memory in electronic communication with the processor;

instructions stored in the memory, the instructions being executable by the processor to;

send network information to a wireless communication device, wherein the network information indicates a first time period, wherein the first time period is a period of silence by the base station; and

monitor synchronization signals during the first time period, wherein monitoring synchronization signals comprises not transmitting.

24. The wireless device of claim 23, wherein the base station has a current stratum, and wherein the instructions are further executable to transmit synchronization signals in a second time period, wherein the second time period comprises slots designated for base stations having a stratum less than or equal to the current stratum to transmit synchronization signals.

25. The wireless device of claim 23, wherein the first time period comprises slots designated for base stations having a stratum less than or equal to the current stratum to monitor synchronization signals.

26. The wireless device of claim 23, wherein the network information comprises a multimedia broadcast single frequency network (MBSFN) subframe declaration.

27. The wireless device of claim 26, wherein the instructions are further executable to receive a common reference signal (CRS) from a synchronizing node, wherein the wireless device uses the CRS for tracking.

28. The wireless device of claim 26, wherein the wireless device has a current stratum, and wherein the instructions are further executable to transmit a common reference signal (CRS) in subframes declared as MBSFN for a stratum greater the current stratum, wherein the subframes declared as MBSFN comprise a second time period.

29. The wireless device of claim 26, wherein the wireless device has a current stratum, and wherein the instructions are further executable to track a common reference signal (CRS) in subframes declared as MBSFN for a stratum less than or equal to the current stratum.

30. The wireless device of claim 23, wherein the instruction are further executable to:

search for a synchronization signal;

determine whether the synchronization signal has been acquired; and

determine a current stratum based on the synchronization signal if the synchronization signal has been acquired.

31. The wireless device of claim 23, wherein the network information comprises a message instructing the one or more wireless communication devices to enter a discontinuous receive (DRX) mode during the period of silence.

32. The wireless device of claim 31, wherein the network information comprises a sleep time for the wireless communication device.

33. The wireless device of claim 23, wherein the network information comprises identifying one or more subframes when the wireless device performs self synchronization.

34. The wireless device of claim 23, wherein the network information comprises a subframe index, wherein the subframe index implicitly indicates one or more subframes when the wireless device performs self synchronization.

35. The wireless device of claim 23, wherein the synchronization signals are sent by a synchronization source.

36. The wireless device of claim 23, wherein monitoring synchronization signals comprises time-tracking a synchronization source.

37. The wireless device of claim 36, wherein the instructions are further executable to perform frequency error correction while time-tracking the synchronization source.

38. The wireless device of claim 23, wherein sending the network information comprises gradually decreasing power and then gradually increasing the power to mimic a deep fade.

39. The wireless device of claim 23, wherein the network information comprises scheduling information, and wherein the scheduling information comprises no scheduled transmissions to the wireless communication device in and around subframes where no common reference signal (CRS) is transmitted.

40. The wireless device of claim 23, wherein sending the network information comprises simultaneously transmitting a common reference signal (CRS) to the wireless communication device while achieving self synchronization using a Primary Synchronization Signal (PSS) on the last two orthogonal frequency division multiplexing (OFDM) symbols of a slot.

41. The wireless device of claim 23, wherein sending the network information comprises simultaneously transmitting a common reference signal (CRS) to the wireless communication device while achieving self synchronization using a Secondary Synchronization Signal (SSS) on the last two orthogonal frequency division multiplexing (OFDM) symbols of a slot.

42. The wireless device of claim 23, wherein the wireless device is a home evolved NodeB (HeNB).

43. The wireless device of claim 23, wherein the wireless communication device is legacy user equipment (UE).

45. A wireless device configured for self synchronization, comprising:

means for sending network information to a wireless communication device, wherein the network information indicates a first time period, wherein the first time period is a period of silence by the base station; and

means for monitoring synchronization signals during the first time period, wherein monitoring synchronization signals comprises not transmitting.

46. The wireless device of claim 45, wherein the base station has a current stratum, and further comprising means for transmitting synchronization signals in a second time period, wherein the second time period comprises slots designated for base stations having a stratum less than or equal to the current stratum to transmit synchronization signals.

47. The wireless device of claim 45, wherein the first time period comprises slots designated for base stations having a stratum less than or equal to the current stratum to monitor synchronization signals.

48. The wireless device of claim 45, wherein the network information comprises a multimedia broadcast single frequency network (MBSFN) subframe declaration.

49. A computer-program product for self synchronization by a base station, the computer-program product comprising a computer-readable medium having instructions thereon, the instructions comprising:

code for sending network information to a wireless communication device, wherein the network information indicates a first time period, wherein the first time period is a period of silence by the base station; and

code for monitoring synchronization signals during the first time period, wherein monitoring synchronization signals comprises not transmitting.

50. The computer-program product of claim 49, wherein the base station has a current stratum, and wherein the instructions further comprise code for transmitting synchronization signals in a second time period, wherein the second time period comprises slots designated for base stations having a stratum less than or equal to the current stratum to transmit synchronization signals.

51. The computer-program product of claim 49, wherein the first time period comprises slots designated for base stations having a stratum less than or equal to the current stratum to monitor synchronization signals.

52. The computer-program product of claim 49, wherein the network information comprises a multimedia broadcast single frequency network (MBSFN) subframe declaration.