Synchronization method and system for clock signal sources, in particular in packet transmission communication systems

• US 7,016,443 B1
• Filed: 08/03/2000
• Issued: 03/21/2006
• Est. Priority Date: 08/06/1999
• Status: Expired due to Term

• Current Assignee: HMD Global Oy
• Original Assignee: Siemens AG
• Inventors: Splett, Armin
• Primary Examiner(s): Chin, Stephen
• Assistant Examiner(s): Wang, Ted M.
• Application Number:
  US10/048,954
• Time in Patent Office: 2,056 Days
• Field of Search: 375/354, 375/371, 375/373, 375/355, 375/293, 370/229, 370/398, 370/392, 370/324, 370/350, 370/395.62, 370/507, 714/815
• US Class Current: 375/354
• 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 56/0015 one node acting as a reference for the others
• CPC Class Codes: H04W 92/12 between access points and access point controllers

Abstract

The invention relates to a method for synchronization of clock sources in a communications system, in particular a radio communications system, having a large number of devices (PSTN, MSC, RNM, BSi, MSi, OMC) which communicate directly or indirectly with one another and have reference clock sources (Cs) for their operation.

In order to overcome aging effects or timing errors in the clock sources (C), the invention proposes the clock sources (C) of one or more communicating devices (MS, BS, RNM) be synchronized by means of asynchronous signaling from at least one reference clock source (Cs). This even allows devices with clock sources that are becoming old to be operated reliably. Furthermore, in particular, there is no need for every device to have its own high-precision clock source (CS). Use is particularly advantageous in communications systems in which no reference clock is transmitted via a landline network.

Claims

1. A method for synchronization of clock sources in a communications system, comprising:

providing a plurality of devices to communicate with one another, each device having a reference clock source for operation, and the clock sources of one or more of the plurality of devices are synchronized using asynchronous signaling from at least one of the reference clock sources;

comparing a received time and/or reference time of one of the devices having a clock source, when the time, which is based on the clock source, forms a time difference; and

determining a number of time differences successively and arranging the time differences with a weighting factor, wherein

the weighting factor is inversely proportional to a response time.

2. The method as claimed in claim 1, in which the signaling occurs in response to a request, which is sent by one of the devices with a clock source to another of the devices with a reference clock source, and/or allows a delay time to be determined.

3. The method as claimed in claim 1, in which time information is interchanged between the plurality of devices in the communications systems, which time information is provided centrally and is transmitted within a transmission frame.

4. The method as claimed in claim 3, in which a specific signaling bit or a complex timer packet with a time and date transmitted as time information.

5. The method as claimed in claim 1, in which aging and/or other timing inaccuracy in a clock source can be synchronized and/or tuned and is compensated for and/or is readjusted.

6. The method as claimed in claim 1, in which more than 90,000 time differences are determined successively and are averaged.

7. The method as claimed in claim 1, in which the plurality of devices with autonomous stable clock sources but without a correspondingly suitable synchronization control device transmit synchronization information between the plurality of devices with a reference clock source and with a synchronization control device and devices with a clock source which can be synchronized.

8. The method as claimed in claim 1, wherein when a mobile device with a clock source configured for synchronization moves from a first area into a second area, synchronization is performed by the device with a reference clock source.

9. The method as claimed in claim 1, in which the communication system is a packet-switching system.

10. The method of claim 1, wherein the determining step further including linear regression.

11. A communications system, comprising:

a plurality of devices to communicate with one another and having reference clock sources for operation, the clock sources of one or more of the plurality of devices is synchronized using asynchronous signaling from at least one of the reference clock sources, and

one of the plurality of devices having a clock source is provided for synchronization and compares the received time and/or a reference time which is estimated or determined by the device using an instantaneous time, which is based on the device'"'"'s clock source, and forms a time difference, wherein

the communications system is configured for a number of time differences which are determined successively and are averaged using a weighting factor in the averaging process, and

the weighting factor is inversely proportional to a response time.

12. The communications system of claim 11, wherein mobile stations and base stations have a clock source configured for synchronization via external asynchronous information signals, and have a synchronization control device.

13. The communication system of claim 11, wherein the number of time difference are averaged further including using linear regression.

14. A communication device for a communication system, comprising:

a clock source configured to be synchronized by an asynchronous signaling from at least one reference clock source of one or more communicating devices;

a synchronization control device which compares a received time and/or a reference time, which is determined or estimated therefrom, having an instantaneous time, which is based on its own clock source which can be synchronized, and forms a time difference, wherein

the synchronization control device is configured such that a number of time differences are determined successively and are averaged, with a weighting factor being used in the averaging process, and

the weighting factor is inversely proportional to a response time.

15. The communication device of claim 14, wherein the number of time difference are averaged further including using linear regression.