Method and device for resident time calculation and synchronization

Patent metadata

Field	Value
Publication number	US-9407388-B2
Application number	US-201214376431-A
Country	US
Kind code	B2
Filing date	Feb 7, 2012
Priority date	Feb 7, 2012
Publication date	Aug 2, 2016
Grant date	Aug 2, 2016

Abstract

The embodiments herein relate to a method in a communications network comprising a communications link connecting a first device to a second device. The communications link comprises an upper layer having a variable delay and a lower layer having a constant delay. The first device comprises a first clock and the second device comprises a second clock. The communications network synchronizes the first clock via the lower layer of the communications link with the second clock. The communications network determines, at the second device, a residence time for a first message when transmitted from the first device to the second device via the upper layer of the communications link.

First claim

The invention claimed is:

1. A method in a communications network comprising a communications link connecting a first device to a second device, wherein the communications link comprises an upper layer having a variable delay and a lower layer having a constant delay, wherein the first device comprises a first clock and the second device comprises a second clock, the method comprising:
synchronizing the first clock via the lower layer of the communications link with the second clock; and
determining, at the second device, a residence time for a fifth message when transmitted from the first device to the second device via the upper layer of the communications link,
wherein the first device further comprises a third clock and the second device comprises a fourth clock, wherein the third clock is a replica of the fourth clock, and
wherein the determining, at the second device, the residence time for the fifth message when transmitted from the first device to the second device via the upper layer of the communications link further comprises:
determining at the first device, an eleventh time stamp using the third clock for the transmission of the fifth message from the first device to the second device;
determining, at the second device, a twelfth time stamp using the fourth clock, which twelfth time stamp is associated with the receipt of the fifth message at the second device; and
determining, at the second device, a second difference between the twelfth time stamp and the eleventh time stamp; and
wherein the fifth message further comprises the eleventh time stamp.

2. The method according to claim 1 , wherein the determining, at the second device, the residence time for the fifth message when transmitted from the first device to the second device via the upper layer of the communications link further comprises:
determining, at the first device, a ninth time stamp using the first clock for the transmission of the fifth message from the first device to the second device;
transmitting the fifth message comprising the ninth time stamp from the first device to the second device via the upper layer of the communications link;
determining, at the second device, a tenth time stamp using the second clock, which tenth time stamp is associated with receipt of the fifth message at the second device; and
determining, at the second device, a first difference between the tenth time stamp and the ninth time stamp.

3. The method according to claim 2 , further comprising:
selecting at the second device, the first difference as the residence time; and
selecting at the second device, the ninth time stamp as an ingress time stamp associated with the fifth message in the communications link.

4. The method according to claim 1 , wherein the first device further comprises a third clock and the second device comprises a fourth clock, and wherein the method further comprises:
synchronizing the third clock via the lower layer of the communications link with the fourth clock.

5. The method according to claim 1 , wherein the communications link is a microwave radio link.

6. A communications network comprising:
a communications link connecting a first device to a second device, wherein the communications link comprises an upper layer having a variable delay and a lower layer having a constant delay, wherein the first device comprises a first clock and the second device comprises a second clock,
wherein the communications network is configured to synchronize the first clock via the lower layer of the communications link with the second clock; and
wherein the communications network is configured to determine, at the second device, a residence time for a fifth message when transmitted from the first device to the second device via the upper layer of the communications link,
wherein the first device further comprises a third clock and the second device comprises a fourth clock, wherein the third clock is a replica of the fourth clock,
wherein the first device is further configured to determine an eleventh time stamp using the third clock for the transmission of the fifth message from the first device to the second device; and
wherein the second device is further configured to:
determine a twelfth time stamp using the fourth clock, which twelfth time stamp is associated with the receipt of the fifth message at the second device; and to
determine a second difference between the twelfth time stamp and the eleventh time stamp; and

wherein the fifth message further comprises the eleventh time stamp.

7. The communications network according to claim 6 ,
wherein the first device is further configured to:
determine, a ninth time stamp using the first clock for the transmission of the fifth message from the first device to the second device; and to
transmit the fifth message comprising the ninth time stamp from the first device to the second device via the upper layer of the communications link; and

wherein the second device is further configured to:
determine a tenth time stamp using the second clock, which tenth time stamp is associated with receipt of the fifth message at the second device; and to
determine a first difference between the tenth time stamp and the ninth time stamp.

8. The communications network according to claim 7 , wherein the second device is further configured to:
select the first difference as the residence time; and to
select the ninth time stamp as an ingress time stamp associated with the fifth message in the communications link.

9. The communications network according to claim 6 , wherein the first device is further configured to synchronize the third clock via the lower layer of the communications link with the fourth clock.

10. The communications network according to claim 6 , wherein the communications link is a microwave radio link.

11. A method in a second device connected to a first device via a communications link in a communications network, wherein the communications link comprises an upper layer having a variable delay and a lower layer having a constant delay, wherein the second device comprises a second clock, the method comprising:
determining a residence time for a fifth message when transmitted from the first device to the second device via the upper layer of the communications link,
wherein the first device further comprises a third clock and the second device comprises a fourth clock, wherein the third clock is a replica of the fourth clock, and wherein the method further comprises:
determining a twelfth time stamp using the fourth clock, which twelfth time stamp is associated with the receipt of the fifth message at the second device; and
determining a second difference between the twelfth time stamp and an eleventh time stamp; and
wherein the fifth message further comprises the eleventh time stamp.

12. The method according to claim 11 , further comprising:
receiving a fifth message comprising a ninth time stamp from the first device via the upper layer of the communications link, which ninth time stamp is associated with transmission of the fifth message from the first device;
determining a tenth time stamp using the second clock, which tenth time stamp is associated with receipt of the fifth message at the second device; and
determining, at the second device, a first difference between the tenth time stamp and the ninth time stamp.

13. A method in a second device connected to a first device via a communications link in a communications network, wherein the communications link comprises an upper layer having a variable delay and a lower layer having a constant delay, wherein the second device compri

Assignees

• Grenabo Hakan
• Thorsen Per-Arne
• ERICSSON TELEFON AB L M (publ)

Inventors

• Grenabo Hakan
• Thorsen Per-Arne

Classifications

• H04J3/0638

  Clock or time synchronisation among nodes; Internode synchronisation (synchronization for ring networks H04L12/422; data switching networks with synchronous transmission H04L12/43) · CPC title

• H04J3/0667 Primary

  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 title