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

Patent metadata

Field	Value
Publication number	US-12058749-B2
Application number	US-202318093104-A
Country	US
Kind code	B2
Filing date	Jan 4, 2023
Priority date	Aug 8, 2013
Publication date	Aug 6, 2024
Grant date	Aug 6, 2024

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 first device for enabling a device-to-device wireless link, the method comprising:
detecting whether a presence signal of a second device is received; and
if the presence signal of the second device is not detected, initiating a time-slot boundary by the first device including:
selecting a first presence signal based on Zadoff-Chu root sequence indexes different from ones used by a base station; and
transmitting the first presence signal of the first device in a selected time-slot in a radio frame.

2. The method of claim 1 , wherein the radio frame comprises an integer number of time-slots.

3. The method of claim 1 , wherein a duration of the time-slot is predetermined.

4. The method of claim 1 , wherein the presence signal of the second device has a second time-slot boundary, and the method further comprising:
if the presence signal of the second device is detected, aligning a time-slot boundary on the first device to the second time-slot boundary established by the second device; and
after aligning to the second time-slot boundary established by the second device, determining a time-slot to use for transmission by the first device.

5. The method of claim 1 , wherein the first presence signal comprises one or more sequences.

6. The method of claim 5 , wherein the first presence signal comprises a primary synchronization signal and a secondary synchronization signal.

7. The method of claim 5 , wherein the one or more sequences stays the same for a plurality of consecutive presence signal transmissions.

8. The method of claim 1 , wherein the selection of the first presence signal is related to an identity of the first device.

9. A device comprising:
a processor; and
a communications subsystem;
wherein the processor and the communications subsystem cooperate to:
detect whether a presence signal of a second device is received; and
if the presence signal of the second device is not detected, initiate a time-slot boundary by the first device including:
selecting a first presence signal based on Zadoff-Chu root sequence indexes different from ones used by a base station; and
transmitting the first presence signal of the first device in a selected time-slot in a radio frame.

10. The device of claim 9 , wherein the radio frame comprises an integer number of time-slots.

11. The device of claim 9 , wherein a duration of the time-slot is predetermined.

12. The device of claim 9 , wherein the presence signal of the second device has a second time-slot boundary, and the processor and communications subsystem further cooperate to:
if the presence signal of the second device is detected, align a time-slot boundary on the first device to the second time-slot boundary established by the second device; and
after aligning to the second time-slot boundary established by the second device, determine a time-slot to use for transmission by the first device.

13. The device of claim 9 , wherein the first presence signal comprises one or more sequences.

14. The device of claim 13 , wherein the first presence signal comprises a primary synchronization signal and a secondary synchronization signal.

15. The device of claim 13 , wherein the one or more sequences stays the same for a plurality of consecutive presence signal transmissions.

16. The device of claim 9 , wherein the selection of the first presence signal is related to an identity of the first device.

17. A non-transitory computer readable medium having stored thereon executable code for execution by a processor of a device, the executable code comprising instructions for:
detecting whether a presence signal of a second device is received; and
if the presence signal of the second device is not detected, initiating a time-slot boundary by the first device including:
selecting a first presence signal based on Zadoff-Chu root sequence indexes different from ones used by a base station; and
transmitting the first presence signal of the first device in a selected time-slot in a radio frame.

18. The non-transitory computer readable medium of claim 17 , wherein the radio frame comprises an integer number of time-slots.

19. The non-transitory computer readable medium of claim 17 , wherein a duration of the time-slot is predetermined.

20. The non-transitory computer readable medium of claim 17 , wherein the presence signal of the second device has a second time-slot boundary, and the executable code comprising further instructions for:
if the presence signal of the second device is detected, aligning a time-slot boundary on the first device to the second time-slot boundary established by the second device; and
after aligning to the second time-slot boundary established by the second device, determining a time-slot to use for transmission by the first device.

Assignees

• Blackberry Ltd

Inventors

• Nguyen Nam
• Blankenship Yufei Wu
• Dhakal Sagar

Classifications

• H04W72/0446

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

• H04W74/085 Primary

  collision avoidance · CPC title

• H04W72/02

  Selection of wireless resources by user or terminal · CPC title

• H04W56/00

  Synchronisation arrangements · CPC title

• H04W8/005

  Discovery of network devices, e.g. terminals · CPC title