METHOD, DEVICE AND SYSTEM FOR CLOCK SYNCHRONIZATION

• US 20120263220A1
• Filed: 06/25/2012
• Published: 10/18/2012
• Est. Priority Date: 12/25/2009
• Status: Abandoned Application

• Current Assignee: Huawei Device Company Limited (Huawei Investment & Holding Co., Ltd.), Zhejiang University
• Original Assignee: Huawei Technologies Co., Ltd. (Huawei Investment & Holding Co., Ltd.), Zhejiang University
• Inventors: Li, Bingbo, Xu, Wenguang, Jiang, Long, Sun, Wenhua, Xu, Yuanxin, Chen, Shumin, Wang, Yang, Liu, Yunfeng
• Application Number:
  US13/532,101
• Publication Number:
  US 20120263220A1
• Time in Patent Office: Days
• US Class Current: 375/224
• CPC Class Codes: H04J 3/0667 Bidirectional timestamps, e.g. NTP or PTP for compensation of clock drift and for compensation of propagation delays arrangements for monitoring round trip delays in packet switching networks H04L43/0864
• CPC Class Codes: H04W 56/00 Synchronisation arrangements

Abstract

A method, a device and a system for clock synchronization are provided. The method includes: under a first transfer mode, generating a first receiving timestamp by using a first link, and acquiring a first transmitting timestamp of a master clock device; under a second transfer mode, generating a second transmitting timestamp by using the first link, and acquiring a second receiving timestamp of the master clock device; and acquiring a time difference to the master clock device according to the first receiving timestamp, the first transmitting timestamp, the second transmitting timestamp and the second receiving timestamp, and realizing a clock synchronization with the master clock device by using the time difference. A slave clock device and a master clock device are provided in the embodiments of the present invention, as well as a system for clock synchronization.

Claims

1. A method for clock synchronization, comprising:

under a first transfer mode, generating a first receiving timestamp by using a first link, and acquiring a first transmitting timestamp of a master clock device;

under a second transfer mode, generating a second transmitting timestamp by using the first link, and acquiring a second receiving timestamp of the master clock device; and

acquiring a time difference to the master clock device according to the first receiving timestamp, the first transmitting timestamp, the second transmitting timestamp and the second receiving timestamp, and realizing a clock synchronization with the master clock device by using the time difference.

2. The method for clock synchronization according to claim 1, wherein acquiring the time difference to the master clock device according to the first receiving timestamp, the first transmitting timestamp, the second transmitting timestamp and the second receiving timestamp comprises:

calculating the time difference to the master clock device according to the formula;

Offset=0.5(TS1−

TM1+TS2−

TM2),

in which, Offset is the time difference, TS1 is the first receiving timestamp, TM1 is the first transmitting timestamp, TS2 is the second transmitting timestamp, and TM2 is the second receiving timestamp.

3. The method for clock synchronization according to claim 2, further comprising switching the transfer mode of a physical layer from the first transfer mode to the second transfer mode, after completing a handshake protocol with the master clock device;

under the first transfer mode, generating the first receiving timestamp by using the first link, and acquiring the first transmitting timestamp of the master clock device comprises;

under the first transfer mode, receiving a synchronous message transmitted by the master clock device through the first link, and recording the first receiving timestamp at which the synchronous message is received; and

under the first transfer mode, receiving a follow message transmitted by the master clock device through the first link, and extracting the first transmitting timestamp of the master clock device from the follow message.

4. The method for clock synchronization according to claim 3, wherein under the second transfer mode, generating the second transmitting timestamp by using the first link, and acquiring the second receiving timestamp of the master clock device comprises

under the second transfer mode, transmitting a time delay request message to the master clock device through the first link, and recording the second transmitting timestamp;

and

under the second transfer mode, receiving a time delay response message returned by the master clock device through the second link, and extracting the second receiving timestamp of the master clock device from the time delay response message.

5. A method for clock synchronization, comprising:

under a first transfer mode, generating a first transmitting timestamp by using a first link, and transmitting the first transmitting timestamp to a slave clock device;

under a second transfer mode, generating a second receiving timestamp by using the first link, and transmitting the second receiving timestamp to the slave clock device; and

by using the slave clock device, acquiring a time difference between the master clock device and the slave clock device according to the first transmitting timestamp and the second receiving timestamp as well as the first receiving timestamp and the second transmitting timestamp acquired by the slave clock device, and realizing a clock synchronization with the slave clock device.

6. The method for clock synchronization according to claim 5, wherein acquiring the time difference between the master clock device and the slave clock device according to the first transmitting timestamp and the second receiving timestamp as well as the first receiving timestamp and the second transmitting timestamp acquired by the slave clock device, and realizing the clock synchronization with the slave clock device comprises:

realizing the clock synchronization with the slave clock device, according to the time difference between the master clock device and the slave clock device acquired from the formula;

Offset=0.5(TS1−

TM1+TS2−

TM2),

in which, Offset is the time difference, TS1 is the first receiving timestamp, TM1 is the first transmitting timestamp, TS2 is the second transmitting timestamp, and TM2 is the second receiving timestamp.

7. The method for clock synchronization according to claim 6, further comprising:

switching the transfer mode of a physical layer from the first transfer mode to the second transfer mode, after completing a handshake protocol with the slave clock device;

under the first transfer mode, generating the first transmitting timestamp by using the first link, and transmitting the first transmitting timestamp to the slave clock device comprises;

under the first transfer mode, transmitting a synchronous message to the slave clock device by using the first link, and recording the first transmitting timestamp; and

under the first transfer mode, transmitting a follow message to the slave clock device through the first link, wherein the follow message carries the first transmitting timestamp.

8. The method for clock synchronization according to claim 7, wherein under the second transfer mode, generating the second receiving timestamp by using the first link, and transmitting the second receiving timestamp to the slave clock device comprises:

under the second transfer mode, receiving a time delay request message transmitted by the slave clock device through the first link, and recording the second receiving timestamp at which the time delay request message is received; and

under the second transfer mode, transmitting a time delay response message to the slave clock device through the second link, wherein the time delay response message carries the second receiving timestamp.

9. A slave clock device, comprising:

a first generation module configured to generate a first receiving timestamp by using a first link under a first transfer mode, and acquire a first transmitting timestamp of a master clock device;

a second generation module configured to generate a second transmitting timestamp by using the first link under a second transfer mode, and acquire a second receiving timestamp of the master clock device; and

a first synchronization module configured to acquire a time difference to the master clock device according to the first receiving timestamp, the first transmitting timestamp, the second transmitting timestamp and the second receiving timestamp acquired by the first generation module and the second generation module, and realize a clock synchronization with the master clock device by using the time difference.

10. The slave clock device according to claim 9, wherein the first synchronization module is specifically configured to calculate the time difference to the master clock device according to the following formula, and realize the clock synchronization with the master clock device by using the time difference:

Offset=0.5(TS1−

TM1+TS2−

TM2),

in which, Offset is the time difference, TS1 is the first receiving timestamp, TM1 is the first transmitting timestamp, TS2 is the second transmitting timestamp, and TM2 is the second receiving timestamp.

11. The slave clock device according to claim 10, further comprising a first switching module configured to switch the transfer mode of a physical layer from the first transfer mode to the second transfer mode, after a handshake protocol with the master clock device is completed;

the first generation module comprises;

a first receiving unit configured to receive a synchronous message transmitted by the master clock device through the first link under the first transfer mode, and record the first receiving timestamp at which the synchronous message is received; and

a second receiving unit configured to receive a follow message transmitted by the master clock device through the first link under the first transfer mode, and extract the first transmitting timestamp of the master clock device from the follow message.

12. The slave clock device according to claim 11, wherein the second generation module comprises:

a first transmitting unit configured to transmit a time delay request message to the master clock device through the first link under the second transfer mode, and record the second transmitting timestamp; and

a third receiving unit configured to receive a time delay response message returned by the master clock device through the second link under the second transfer mode, and extract the second receiving timestamp of the master clock device from the time delay response message.

13. A master clock device, comprising:

a third generation module configured to generate a first transmitting timestamp by using a first link under a first transfer mode, and transmit the first transmitting timestamp to a slave clock device;

a fourth generation module configured to generate a second receiving timestamp by using the first link under a second transfer mode, and transmit the second receiving timestamp to the slave clock device; and

a second synchronization module configured to acquire, by using the slave clock device, a time difference between the master clock device and the slave clock device, according to the first transmitting timestamp and the second receiving timestamp as well as the first receiving timestamp and the second transmitting timestamp acquired by the slave clock device, and realize a clock synchronization with the slave clock device.

14. The master clock device according to claim 13, wherein the second synchronization module is specifically configured to realize, by using the slave clock device, the clock synchronization with the master clock device according to the time difference between the master clock device and the slave clock device acquired from the formula:

Offset=0.5(TS1−

TM1+TS2−

TM2),

In which, Offset is the time difference, TS1 is the first receiving timestamp, TM1 is the first transmitting timestamp, TS2 is the second transmitting timestamp, and TM2 is the second receiving timestamp.

15. The master clock device according to claim 14, further comprising a second switching module configured to switch the transfer mode of a physical layer from the first transfer mode to the second transfer mode, after a handshake protocol with the slave clock device is completed;

the third generation module comprises;

a second transmitting unit configured to transmit a synchronous message to the slave clock device through the first link under the first transfer mode, and record the first transmitting timestamp; and

a third transmitting unit configured to transmit a follow message to the slave clock device through the first link under the first transfer mode, wherein the follow message carries the first transmitting timestamp.

16. The master clock device according to claim 15, wherein the fourth generation module comprises:

a fourth receiving unit configured to receive a time delay request message transmitted by the slave lock device through the first link under the second transfer mode, and record the second receiving timestamp at which the time delay request message is received; and

a fourth transmitting unit configured to transmit a time delay response message to the slave clock device through the second link under the second transfer mode, wherein the time delay response message carries the second receiving timestamp.

17. A system for clock synchronization, comprising a slave clock device and a master clock device:

the slave clock device comprising;

a first generation module configured to generate a first receiving timestamp by using a first link under a first transfer mode, and acquire a first transmitting timestamp of a master clock device;

a second generation module configured to generate a second transmitting timestamp by using the first link under a second transfer mode, and acquire a second receiving timestamp of the master clock device; and

a first synchronization module configured to acquire a time difference to the master clock device according to the first receiving timestamp, the first transmitting timestamp, the second transmitting timestamp and the second receiving timestamp acquired by the first generation module and the second generation module, and realize a clock synchronization with the master clock device by using the time difference,

the master clock device comprising;

a third generation module configured to generate a first transmitting timestamp by using a first link under a first transfer mode, and transmit the first transmitting timestamp to a slave clock device;

a fourth generation module configured to generate a second receiving timestamp by using the first link under a second transfer mode, and transmit the second receiving timestamp to the slave clock device; and

a second synchronization module configured to acquire, by using the slave clock device, a time difference between the master clock device and the slave clock device, according to the first transmitting timestamp and the second receiving timestamp as well as the first receiving timestamp and the second transmitting timestamp acquired by the slave clock device, and realize a clock synchronization with the slave clock device.

18. The system according to claim 17, wherein

the first synchronization module is specifically configured to calculate the time difference to the master clock device according to the following formula, and realize the clock synchronization with the master clock device by using the time difference:

Offset=0.5(TS1−

TM1+TS2−

TM2),

in which, Offset is the time difference, TS1 is the first receiving timestamp, TM1 is the first transmitting timestamp, TS2 is the second transmitting timestamp, and TM2 is the second receiving timestamp,

the second synchronization module is specifically configured to realize, by using the slave clock device, the clock synchronization with the master clock device according to the time difference between the master clock device and the slave clock device acquired from the formula;

Offset=0.5(TS1−

TM1+TS2−

TM2).

19. The system according to claim 18, the slave clock device further comprising a first switching module configured to switch the transfer mode of a physical layer from the first transfer mode to the second transfer mode, after a handshake protocol with the master clock device is completed;

the first generation module comprises;

a first receiving unit configured to receive a synchronous message transmitted by the master clock device through the first link under the first transfer mode, and record the first receiving timestamp at which the synchronous message is received; and

a second receiving unit configured to receive a follow message transmitted by the master clock device through the first link under the first transfer mode, and extract the first transmitting timestamp of the master clock device from the follow message,

the master clock device further comprising a second switching module configured to switch the transfer mode of a physical layer from the first transfer mode to the second transfer mode, after a handshake protocol with the slave clock device is completed;

the third generation module comprises;

a second transmitting unit configured to transmit a synchronous message to the slave clock device through the first link under the first transfer mode, and record the first transmitting timestamp; and

a third transmitting unit configured to transmit a follow message to the slave clock device through the first link under the first transfer mode, wherein the follow message carries the first transmitting timestamp.

20. The system according to claim 19,

wherein the second generation module comprises:

a first transmitting unit configured to transmit a time delay request message to the master clock device through the first link under the second transfer mode, and record the second transmitting timestamp; and

a third receiving unit configured to receive a time delay response message returned by the master clock device through the second link under the second transfer mode, and extract the second receiving timestamp of the master clock device from the time delay response message;

and wherein the fourth generation module comprises;

a fourth receiving unit configured to receive a time delay request message transmitted by the slave lock device through the first link under the second transfer mode, and record the second receiving timestamp at which the time delay request message is received; and

a fourth transmitting unit configured to transmit a time delay response message to the slave clock device through the second link under the second transfer mode, wherein the time delay response message carries the second receiving timestamp.