Systems and Methods for User Equipment Synchronization

• US 20160044620A1
• Filed: 08/06/2015
• Published: 02/11/2016
• Est. Priority Date: 08/07/2014
• Status: Active Grant

• Current Assignee: Futurewei Technologies Incorporated (Huawei Investment & Holding Co., Ltd.)
• Original Assignee: Futurewei Technologies Incorporated (Huawei Investment & Holding Co., Ltd.)
• Inventors: Bagheri, Hossein, Sartori, Philippe, Soong, Anthony C.K., Liu, Deping
• Granted Patent: US 10,111,191 B2
• Time in Patent Office: Days
• US Class Current: 1/1
• CPC Class Codes: H04W 24/10 Scheduling measurement reports ; Arrangements for measurement reports
• CPC Class Codes: H04W 56/0015 one node acting as a reference for the others
• CPC Class Codes: H04W 72/20 Control channels or signalling for resource management
• CPC Class Codes: H04W 76/14 Direct-mode setup

Abstract

Systems and methods for User Equipment (UE) synchronization for Device-to-Device (D2D) out-of-coverage communication are provided. In an embodiment, a method in an in-coverage (IC) UE for the IC UE to become a synchronization source for out-of-coverage UEs for D2D communication includes obtaining, by the IC UE scanning parameters; scanning, by the IC UE, for out-of-coverage synchronization signals; transmitting, by the IC UE, a measurement report to a Transmission Point (TP) in response to a report trigger, the measurement report comprising information of one or more received out-of-coverage synchronization signals; receiving, by the IC UE, a configuration command from the TP instructing the IC UE to become a synchronization source in response to a configuration command from the TP; and transmitting, by the IC UE, a D2D synchronization signal (SS) for a duration of time or until instructed not to do so by the TP.

Claims

1. A method in an in-coverage (IC) user equipment (UE) for the IC UE to become a synchronization source for out-of-coverage UEs for device-to-device (D2D) communication, the method comprising:

obtaining, by the IC UE, scanning parameters;

scanning, by the IC UE, for out-of-coverage synchronization signals;

transmitting, by the IC UE, a measurement report to a Transmission Point (TP) in response to a report trigger, the measurement report comprising information of one or more received out-of-coverage synchronization signals;

receiving, by the IC UE, a configuration command from the TP instructing the IC UE to become a synchronization source; and

transmitting, by the IC UE, a D2D synchronization signal (SS) for a duration of time or until instructed not to do so by the TP.

2. The method of claim 1, wherein the scanning parameters are preconfigured.

3. The method of claim 1, wherein the scanning parameters are received in a broadcast message.

4. The method of claim 1, wherein the scanning parameters comprise T1, T2, and T3, wherein T1 is a time gap between scanning windows, T2 is a length of time of the scanning window, and T3 is a total length of time for scanning.

5. The method of claim 1, further comprising:

refraining from configuring the IC UE to become the synchronization source in response to a configuration command from the TP establishing a different IC UE as the synchronization source; and

refraining from transmitting the D2D synchronization signal.

6. The method of claim 1, further comprising:

listening, by the IC UE, for measurement reports from other UEs for a listening time;

refraining, by the IC UE, from transmitting the measurement report when the IC UE determines that another UE has transmitted the measurement report during the listening time; and

transmitting, by the IC UE, the measurement report to the TP when the UE determines that no other UE has transmitted the measurement report during the listening time.

7. The method of claim 6, wherein the listening time comprises a random time.

8. The method of claim 1, further comprising:

selecting, by the UE, a random number; and

refraining from transmitting, by the IC UE, the measurement report when the random number is less than a predetermined threshold.

9. The method of claim 1, further comprising:

listening, by the IC UE, for the D2DSS from other UEs for a listening time;

refraining, by the IC UE, from transmitting the measurement report when the IC UE determines that another UE has transmitted the D2DSS during the listening time; and

transmitting, by the IC UE, the measurement report to the TP when the UE determines that no other UE has transmitted the D2DSS during the listening time.

10. The method of claim 1, further comprising:

reading, by the IC UE, a physical D2D synchronization channel (PD2DSCH) of detected sources;

refraining, by the IC UE, from transmitting the measurement report when the IC UE determines that there is another synchronization source belonging the IC UE'"'"'s cell; and

transmitting, by the IC UE, the measurement report to the TP when the UE determines that there is not another synchronization source belonging the IC UE'"'"'s cell.

11. The method of claim 1, further comprising refraining from transmitting the measurement report for one of the out-of-coverage synchronization signals if a received signal strength (RSS) of the one of the out-of-coverage synchronization signals is less than a threshold.

12. An in-coverage (IC) user equipment (UE) comprising:

a processor; and

a non-transitory computer readable storage medium storing programming for execution by the processor, the programming including instructions to;

obtain scanning parameters;

scan for out-of-coverage synchronization signals;

transmit a measurement report to Transmission Point (TP) in response to a report trigger, the measurement report comprising information of one or more received out-of-coverage synchronization signals;

receive a configuration command from the TP instructing the IC UE to become a synchronization source; and

transmit a device-to-device (D2D) synchronization signal (SS) for a duration of time or until instructed not to do so by the TP.

13. The IC UE of claim 12, wherein the scanning parameters are preconfigured.

14. The IC UE of claim 12, wherein the scanning parameters are received in a broadcast message.

15. The IC UE of claim 12, wherein the scanning parameters comprise T1, T2, and T3, wherein T1 is a time gap between scanning windows, T2 is a length of time of the scanning window, and T3 is a total length of time for scanning.

16. The IC UE of claim 12, wherein the programming further comprises instructions to:

refrain from configuring the IC UE to become the synchronization source in response to a configuration command from the TP establishing a different IC UE as the synchronization source; and

refrain from transmitting the D2D synchronization signal.

17. The IC UE of claim 12, wherein the programming further comprises instructions to:

listen for measurement reports from other UEs for a listening time;

refrain from transmitting the measurement report when the IC UE determines that another UE has transmitted the measurement report during the listening time; and

transmit the measurement report to the TP when the UE determines that no other UE has transmitted the measurement report during the listening time.

18. The IC UE of claim 17, wherein the listening time comprises a random time.

19. The IC UE of claim 12, wherein the programming further comprises instructions to:

select a random number; and

refrain from transmitting, by the IC UE, the measurement report when the random number is less than a predetermined threshold.

20. The IC UE of claim 12, wherein the programming further comprises instructions to:

listen for the D2DSS from other UEs for a listening time;

refrain from transmitting the measurement report when the IC UE determines that another UE has transmitted the D2DSS during the listening time; and

transmit the measurement report to the TP when the UE determines that no other UE has transmitted the D2DSS during the listening time.

21. The IC UE of claim 12, wherein the programming further comprises instructions to:

read a physical D2D synchronization channel (PD2DSCH) of detected sources;

refrain from transmitting the measurement report when the IC UE determines that there is another synchronization source belonging the IC UE'"'"'s cell; and

transmit the measurement report to the TP when the UE determines that there is not another synchronization source belonging the IC UE'"'"'s cell.

22. The IC UE of claim 12, further comprising refraining from transmitting the measurement report for one of the out-of-coverage synchronization signals if a received signal strength (RSS) of the one of the out-of-coverage synchronization signals is less than a threshold.

23. A method in a transmission point (TP) for selecting an in-network-coverage user equipment (UE) to serve as a synchronization source for out-of-network-coverage UEs for device-to-device (D2D) communications, comprising:

receiving, with the TP, a measurement report from a first one of a plurality of in-network-coverage UEs, the measurement report corresponding to an out-of-network coverage UE;

selecting, with the TP, a second one of the in-network-coverage UEs to be a synchronization source; and

transmitting, with the TP, a configuration message to the second one of the in-network-coverage UEs, the configuration message identifying the second one of the in-network-coverage UEs as the synchronization source, wherein only the second one of the in-network-coverage UEs is permitted to transmit a D2D synchronization signal (SS) during a specified time frame.

24. The method of claim 23, further comprising:

transmitting, with the TP, a scanning message to at least some of the in-network-coverage UEs, the scanning message instructing the in-network-coverage UEs when to scan for out-of-network UE signals.

25. The method of claim 24, wherein the scanning message comprises a first time duration indicating a duration of time for one of the in-network-coverage UEs to scan for D2DSS from out-of-network UEs, a second time duration indicating a length of time between successive scans, and a third time duration indicating a time after which the one of the in-network-coverage UEs is to stop scanning.

26. The method of claim 24, wherein the scanning message comprises a threshold, wherein in-network-coverage UEs that measure a received power from the TP above the threshold are prohibited from scanning.

27. The method of claim 23, further comprising:

determining a number of scanning groups of in-network-coverage UEs; and

sending scanning parameters to each of the groups.

28. The method of claim 27, wherein the scanning parameters for a first group are different from the scanning parameters for a second group.

29. The method of claim 23, wherein the first one of the plurality of in-network-coverage UEs is the second one of the plurality of in-network-coverage UEs.

30. A transmission point (TP) comprising:

a processor; and

a non-transitory computer readable storage medium storing programming for execution by the processor, the programming including instructions to;

receive a measurement report from a first one of a plurality of in-network-coverage UEs, the measurement report corresponding to an out-of-network coverage UE;

select a second one of the in-network-coverage UEs to be a synchronization source; and

transmit a configuration message to the second one of the in-network-coverage UEs, the configuration message identifying the second one of the in-network-coverage UEs as the synchronization source, wherein only the second one of the in-network-coverage UEs is permitted to transmit a D2D synchronization signal (SS) during a specified time frame.

31. The TP of claim 30, further comprising:

transmitting, with the TP, a scanning message to at least some of the in-network-coverage UEs, the scanning message instructing the in-network-coverage UEs when to scan for out-of-network UE signals.

32. The TP of claim 31, wherein the scanning message comprises a first time duration indicating a duration of time for one of the in-network-coverage UEs to scan for D2DSS from out-of-network UEs, a second time duration indicating a length of time between successive scans, and a third time duration indicating a time after which the one of the in-network-coverage UEs is to stop scanning.

33. The TP of claim 31, wherein the scanning message comprises a threshold, wherein in-network-coverage UEs that measure a received power from the TP above the threshold are prohibited from scanning.

34. The TP of claim 30, further comprising:

determining a number of scanning groups of in-network-coverage UEs; and

sending scanning parameters to each of the groups.

35. The TP of claim 34, wherein the scanning parameters for a first group are different from the scanning parameters for a second group.

36. The TP of claim 30, wherein the first one of the plurality of in-network-coverage UEs is the second one of the plurality of in-network-coverage UEs.