Method and system for initial synchronization and collision avoidance in device to device communications without network coverage

Patent metadata

Field	Value
Publication number	US-10932309-B2
Application number	US-201816219734-A
Country	US
Kind code	B2
Filing date	Dec 13, 2018
Priority date	Aug 8, 2013
Publication date	Feb 23, 2021
Grant date	Feb 23, 2021

Abstract

A method at a first device for enabling a device-to-device wireless link, the method detecting whether a presence signal of a second device is received over a first time period, the presence signal of the second device having a time-slot boundary; and if the presence signal of the second device is not detected, initiating a time-slot boundary by the first device including: transmitting a first presence signal of the first device in a selected time-slot; and checking for an acknowledgment to the first presence signal.

First claim

The invention claimed is:

1. A method at a device for enabling a device-to-device wireless link, the method comprising:
listening, by the device, for a presence signal from another device on a channel for a first time period comprising a predetermined number of one or more frame periods; and
in response to not finding a presence signal from another device, transmitting, by the device, a presence signal and a system frame number on the channel to establish a time-slot boundary, wherein the presence signal enables identification of a device-to-device cluster, wherein the device-to-device cluster is a group of devices capable of establishing direct links between them;
wherein the transmitting of the presence signal enables alignment to the established time-slot boundary.

2. The method of claim 1 , wherein the first time period further comprises a randomly generated contention period.

3. The method of claim 1 , wherein the one or more frame periods comprise an integer number of time-slot durations.

4. The method of claim 1 , further comprising receiving, from another device, an acknowledgement related to the presence signal transmitted by the device.

5. The method of claim 1 , further comprising:
receiving the presence signal from another device during the first time period; and
omitting the transmitting step.

6. The method of claim 5 , further comprising establishing the time slot boundary based on the received presence signal.

7. The method of claim 6 , further comprising selecting a free time slot to communicate.

8. The method of claim 1 , wherein at least one of the presence signal from another device and the presence signal transmitted by the device comprises a primary synchronization signal and a secondary synchronization signal.

9. A wireless device comprising:
a processor; and
a communications subsystem;

wherein the processor and the communications subsystem cooperate to:
listen, by the wireless device, for a presence signal from another device on a channel for a first time period comprising a predetermined number of one or more frame periods; and
in response to not finding a presence signal from another device, transmit, by the wireless device, a presence signal and a system frame number on the channel to establish a time-slot boundary, wherein the presence signal enables identification of a device-to-device cluster, wherein the device-to-device cluster is a group of devices capable of establishing direct links between them;

wherein the transmitting of the presence signal enables alignment to the established time-slot boundary.

10. The wireless device of claim 9 , wherein the first time period further comprises a randomly generated contention period.

11. The wireless device of claim 9 , wherein the one or more frame periods comprise an integer number of time-slot durations.

12. The wireless device of claim 9 , wherein the processor and the communications subsystem further cooperate to receive, from another device, an acknowledgement related to the presence signal transmitted by the wireless device.

13. The wireless device of claim 9 , wherein the processor and the communications subsystem further cooperate to:
receive the presence signal from another device during the first time period; and

omit the transmitting step.

14. The wireless device of claim 13 , wherein the processor and the communications subsystem further cooperate to establish the time slot boundary based on the received presence signal.

15. The wireless device of claim 14 , wherein the processor and the communications subsystem further cooperate to select a free time slot to communicate.

16. The wireless device of claim 9 , wherein at least one of the presence signal from another device and the presence signal transmitted by the wireless device comprises a primary synchronization signal and a secondary synchronization signal.

17. A non-transitory computer readable medium having stored thereon computer-executable code for execution by a processor of a wireless device, the code comprising instructions for:
listening, by the wireless device, for a presence signal from another device on a channel for a first time period comprising a predetermined number of one or more frame periods; and
in response to not finding a presence signal from another device, transmitting, by the wireless device a presence signal and a system frame number on the channel to establish a time-slot boundary, wherein the presence signal enables identification of a device-to-device cluster, wherein the device-to-device cluster is a group of devices capable of establishing direct links between them;

wherein the transmitting of the presence signal enables alignment to the established time-slot boundary.

18. The non-transitory computer readable medium of claim 17 , wherein the first time period further comprises a randomly generated contention period.

19. The non-transitory computer readable medium of claim 17 , wherein the one or more frame periods comprise an integer number of time-slot durations.

20. The non-transitory computer readable medium of claim 17 , wherein the code further comprises instructions for receiving, from another device, an acknowledgement related to the presence signal transmitted by the wireless device.

21. The non-transitory computer readable medium of claim 17 , wherein the code further comprises instructions for:
receiving the presence signal from another device during the first time period; and
omitting the transmitting step.

22. The non-transitory computer readable medium of claim 21 , wherein the code further comprises instructions for establishing the time slot boundary based on the received presence signal.

23. The non-transitory computer readable medium of claim 22 , wherein the code further comprises instructions for selecting a free time slot to communicate.

24. The non-transitory computer readable medium of claim 17 , wherein at least one of the presence signal from another device and the presence signal transmitted by the wireless device comprises a primary synchronization signal and a secondary synchronization signal.

Assignees

• Blackberry Ltd

Inventors

• Nguyen Nam
• Blankenship Yufei Wu
• Dhakal Sagar

Classifications

• H04J13/0062

  Zadoff-Chu · CPC title

• H04L1/1812

  Hybrid protocols; Hybrid automatic repeat request [HARQ] · CPC title

• H04W56/001

  Synchronization between nodes · CPC title

• H04W72/0446

  Resources in time domain, e.g. slots or frames · CPC title

• H04W72/40

  Resource management for direct mode communication, e.g. D2D or sidelink · CPC title