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

Patent metadata

Field	Value
Publication number	US-10172176-B2
Application number	US-201715672600-A
Country	US
Kind code	B2
Filing date	Aug 9, 2017
Priority date	Aug 8, 2013
Publication date	Jan 1, 2019
Grant date	Jan 1, 2019

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 for a presence signal from another device on a channel for a first time period comprising a predetermined frame period; and
transmitting a presence signal and system frame number on the channel to establish a time-slot boundary;
wherein the transmitting of the presence signal enables another device to align 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 frame period comprises 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.

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 the presence signal 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 for a presence signal from another device on a channel for a first time period comprising a predetermined frame period; and
transmit a presence signal and system frame number on the channel to establish a time-slot boundary;
wherein the transmitting of the presence signal enables another device to align 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 frame period comprises 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.

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 the presence signal 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 for a presence signal from another device on a channel for a first time period comprising a predetermined frame period; and
transmitting a presence signal and system frame number on the channel to establish a time-slot boundary;
wherein the transmitting of the presence signal enables another device to align 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 frame period comprises 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.

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 the presence signal comprises a primary synchronization signal and a secondary synchronization signal.

Assignees

• Blackberry Ltd

Inventors

• Nguyen Nam
• Blankenship Yufei Wu
• Dhakal Sagar

Classifications

• H04W56/002

  Mutual synchronization · CPC title

• H04W72/02

  Selection of wireless resources by user or terminal · CPC title

• H04W4/70

  Services for machine-to-machine communication [M2M] or machine type communication [MTC] · CPC title

• H04B7/2656

  for structure of frame, burst · CPC title

• H04W76/14 Primary

  Direct-mode setup · CPC title