Systems and methods for synchronization signal timeslot reselection for synchronization target selection in networks

• US 10,244,495 B1
• Filed: 09/28/2017
• Issued: 03/26/2019
• Est. Priority Date: 09/28/2017
• Status: Active Grant

• Current Assignee: Hong Kong Applied Science And Technology Research Institute Co., Ltd.
• Original Assignee: Hong Kong Applied Science And Technology Research Institute Co., Ltd.
• Inventors: Thong, Wilson Wang Kit, Kwan, Victor Man Wai, Zhang, Elaine Jihui, Chuai, Jie, Leung, Ching Hong, Lee, Yan Lam, Tsang, Eric Kong Chau
• Primary Examiner(s): Elpenord, Candal
• Application Number:
  US15/718,492
• Publication Number:
  US 20190098588A1
• Time in Patent Office: 544 Days
• Field of Search: None
• CPC Class Codes: H04W 56/001 Synchronization between nodes
• CPC Class Codes: H04W 72/0446 Resources in time domain, e.g. slots or frames

Abstract

Methods and systems which provide for synchronization target selection by configuring a network device to reselect a synchronization signal transmission timeslot for synchronization target searching by the network device are described. Synchronization signal timeslot reselection may provide for downgrading a current stratum index to an artificial stratum index that does not accurately indicate a number of hops between the network device and a global synchronization source to allow for selection of available synchronization targets with stratum indices that are higher than or equal to the network device'"'"'s stratum index without causing a synchronization loop. A synchronization signal pattern cycle structure having synchronization signal timeslots organized into multiple subcycles for accommodating synchronization signal timeslot reselection is utilized according to embodiments.

Claims

1. A method comprising;

monitoring, by a network device, for a synchronization signal transmitted by a first synchronization target network device at synchronization signal timeslot k, wherein the network device is operating in synchronization with the first synchronization target network device based upon previously receiving a synchronization signal from the first synchronization target network device, wherein the synchronization signal timeslot k corresponds to a stratum level of the first synchronization target network device within a synchronization tree, and wherein the synchronization signal timeslot is a synchronization signal timeslot of N synchronization signal timeslots each of which corresponds to a different stratum level of the synchronization tree and 0≤

k<

N;

transmitting, by the network device when the synchronization signal transmitted by the first synchronization target network device is received by the network device at a synchronization signal timeslot k, a network device synchronization signal at synchronization signal timeslot k+1 for synchronizing operation of network devices downstream from the network device in the synchronization tree, wherein the synchronization signal timeslot k+1 corresponds to a stratum, level of the network device within the synchronization tree; and

performing, by the network device when the synchronization signal transmitted by the first synchronization target network device is not received by the network device at the synchronization signal timeslot k, a stratum level downgrade procedure configured for searching for a second synchronization target network device having a synchronization tree stratum level equal to or higher than the synchronization tree stratum level of the network device.

2. The method of claim 1, wherein the stratum level downgrade procedure comprises:

reselecting, by the network device, synchronization signal timeslot k+1+N corresponding to an artificial stratum index for scheduling transmission of the network device synchronization signal during searching for the second synchronization target network device by the network device.

3. The method of claim 2, wherein the stratum level downgrade procedure further comprises:

stopping, by the network device, transmission of the synchronization signal at the synchronization signal timeslot k+1.

4. The method of claim 2, further comprising:

reselecting, by the network device when a synchronization signal transmitted by a neighboring network device available to be used as the second synchronization target network device is received in synchronization signal timeslot id during the searching for the second synchronization target network device, synchronization signal timeslot k′

+1 corresponding to a new stratum level index of the network device for transmission of the network device synchronization signal.

5. The method of claim 1, further comprising:

performing, by the network device when a synchronization signal transmitted by a neighboring network device available to be used as the second synchronization target network device is received in synchronization signal timeslot k′

during the searching for the second synchronization target network device, a stratum level upgrade procedure configured for decreasing a synchronization tree stratum level index of the network device based upon a synchronization tree stratum level of the neighboring network device transmitting the synchronization signal received by the network device at synchronization signal timeslot k′

.

6. The method of claim 5, wherein the stratum level upgrade procedure comprises:

reselecting, by the network device, synchronization signal timeslot k′

+1 for transmission of the network device synchronization signal.

7. The method of claim 5, wherein k′

≥

k.

8. The method of claim 5, wherein k′

<

k.

9. The method of claim 1, wherein synchronization signal timeslot k and

synchronization signal timeslot k+1 are timeslots of a plurality of timeslots comprising 2N synchronization signal timeslots forming a synchronization signal pattern cycle, and wherein the synchronization signal pattern cycle is repeated for providing network synchronization.

10. The method of claim 9, wherein the synchronization signal pattern cycle comprises a plurality of subcycles, wherein a first subcycle of the plurality of subcycles comprises synchronization signal timeslots corresponding to synchronization tree stratum levels including synchronization signal timeslot k and synchronization signal timeslot k+1, and wherein a second subcycle of the plurality of subcycles comprises synchronization signal timeslots corresponding to artificial stratum levels including the synchronization signal timeslot corresponding to an artificial stratum index.

11. The method of claim 1, wherein the synchronization signal transmitted by the first synchronization target network device includes information selected from the group consisting of information regarding an extent of time misalignment between the first synchronization target network device and the network device, information regarding identification of the first synchronization target network device, and information ‘

from which one or more signal reception quality metrics can be determined by the network device.

12. A system comprising:

a network device having a receiver and transmitter for data communication in a network, the network device configured to;

monitor for a synchronization signal transmitted by a first synchronization target network device at synchronization signal timeslot k, wherein the synchronization signal timeslot k corresponds to a stratum level of the first synchronization target network device within a synchronization tree, and wherein the synchronization signal timeslot k is a synchronization signal timeslot of N synchronization signal timeslots each of which corresponds to a different stratum level of the synchronization tree and 0≤

k<

N;

transmit a network device synchronization signal at synchronization signal timeslot k+1 for synchronizing operation of network devices downstream from the network device in the synchronization tree when the synchronization signal transmitted by the first synchronization target network device is received by the network device at the synchronization signal timeslot k, wherein synchronization signal timeslot k+1 corresponds to a stratum level of the network device within the synchronization tree; and

perform a stratum level downgrade procedure configured for searching for a second synchronization target network device having a synchronization tree stratum level equal to or higher than the synchronization tree stratum level of the network device when the synchronization signal transmitted by the first synchronization target network device is not received by the network device at synchronization signal timeslot k.

13. The system of claim 12, wherein to perform the stratum level downgrade procedure the network device is configured to:

reselect synchronization signal timeslot k+1+/V corresponding to an artificial stratum index for scheduling transmission of the network device synchronization signal during searching for the second synchronization target network device by the network device.

14. The system of claim 13, wherein to perform the stratum level downgrade procedure the network device is further configured to:

stop transmission of the synchronization signal at the synchronization signal timeslot k+1.

15. The system of claim 13, wherein the network device is further configured to:

reselect synchronization signal timeslot N+1 corresponding to a new stratum level index of the network device for transmission of the network device synchronization signal when a synchronization signal transmitted by a neighboring network device available to be used as the second synchronization target network device is received in synchronization signal timeslot k′

during the searching for the second synchronization target network device.

16. The system of claim 12, wherein the network device is further configured to:

perform a stratum level upgrade procedure configured for decreasing a synchronization tree stratum level index of the network device based upon a synchronization tree stratum level of a neighboring network device transmitting the synchronization signal received by the network device at synchronization signal timeslot k′

when a synchronization signal transmitted by a neighboring network device available to be used as the second synchronization target network device is received in synchronization signal timeslot N during the searching for the second synchronization target network device.

17. The system of claim 16, wherein to perform the stratum level upgrade procedure the network device is configured to:

reselect synchronization signal timeslot k′

+1 for transmission of the network device synchronization signal.

18. The system of claim 12, wherein the synchronization signal timeslot k and the synchronization signal timeslot k+1 are timeslots of a plurality of timeslots comprising IN synchronization signal timeslots forming a synchronization signal pattern cycle, and wherein the synchronization signal pattern cycle is repeated for providing network synchronization.

19. The system of claim 18, wherein the synchronization signal pattern cycle comprises a plurality of subcycles, wherein a first subcycle of the plurality of subcycles comprises synchronization signal timeslots corresponding to synchronization tree stratum levels including the synchronization signal timeslot k and the synchronization signal timeslot k+1, and wherein a second subcycle of the plurality of subcycles comprises synchronization signal timeslots corresponding to artificial stratum levels including the synchronization signal timeslot, corresponding to an artificial stratum index.

20. The system of claim 12, wherein the synchronization signal transmitted by the first synchronization target network device includes information selected from the group consisting of information regarding an extent of time misalignment between the first synchronization target network device and the network device, information regarding identification of the first synchronization target network device, and information from which one or more signal reception quality metrics can be determined by the network device.

21. A synchronization signal timeslot reselection method for synchronization target selection in a network, the method comprising:

monitoring, by a network device, for a synchronization signal of a first synchronization target network device of the network device in a synchronization signal timeslot corresponding to a synchronization tree stratum index of the first synchronization target network device, wherein the network device is operable to transmit the synchronization signal in the synchronization signal timeslot corresponding to a synchronization tree stratum index of the network device when the synchronization signal of the first synchronization target network device is received by the network device in the synchronization signal timeslot corresponding to the synchronization tree stratum index of the first synchronization target network device;

determining, by the network device, that the synchronization signal of the first synchronization target network de vice of the network de vice has not been received by the network device in the synchronization signal timeslot corresponding to the synchronization tree stratum index of the first synchronization target network device;

reselecting a synchronization signal timeslot corresponding to an artificial stratum index for scheduling transmission of the synchronization signal in a synchronization signal timeslot corresponding to the artificial stratum index during a search for a second synchronization target network device by the network device, wherein the network device is operable to stop transmitting the synchronization signal in the synchronization signal timeslot corresponding to the synchronization tree stratum index of the network device when the synchronization signal of the first synchronization target network device is determined to have been received by the network device in the synchronization signal timeslot corresponding to the synchronization tree stratum index of the first synchronization target network device; and

initiating, by the network device, the search for the second synchronization target network device.

22. The method of claim 21, wherein the search for the second synchronization target network device comprises:

monitoring, by the network device, synchronization signal timeslots corresponding to synchronization tree stratum indices equal to and higher than the synchronization tree stratum index of the network device for a neighboring network device suitable for use as the second synchronization target network device by the network device.

23. The method of claim 22, further comprising:

reselecting the synchronization signal timeslot for the transmission of the network device synchronization signal based upon a stratum index of a network device transmitting a received synchronization signal if the network device receives the received synchronization signal in the synchronization signal timeslot corresponding to the synchronization tree stratum index equal to or higher than the synchronization tree stratum index of the network device.

24. The method of claim 22, wherein the search for the second synchronization target network device comprises:

monitoring, by the network device, the synchronization signal timeslots corresponding to synchronization tree stratum indices lower than the synchronization tree stratum index of the network device for a neighboring network device suitable for use as the second synchronization target network device by the network device.

25. The method of claim 24, further comprising:

reselecting the synchronization signal timeslot for transmission of the network device synchronization signal based upon the synchronization tree stratum index of a network device transmitting a received synchronization signal if the network device receives the received synchronization signal in the synchronization signal timeslot corresponding to synchronization tree stratum index lower than the synchronization tree stratum index of the network device.

26. The method of claim 21, wherein each of the synchronization signal timeslots are timeslots of a synchronization signal pattern cycle having a plurality of subcycles, wherein a first subcycle of the plurality of subcycles comprises synchronization signal timeslots corresponding to synchronization tree stratum levels including the synchronization signal timeslot corresponding to a synchronization tree stratum index of the first synchronization target network device and the synchronization signal timeslot corresponding to the synchronization tree stratum index of the network device, and wherein a second subcycle of the plurality of subcycles comprises synchronization signal timeslots corresponding to artificial stratum levels including the synchronization signal timeslot corresponding to an artificial stratum index.