Base-site synchronization in a communication system

• US 5,245,634 A
• Filed: 03/23/1992
• Issued: 09/14/1993
• Est. Priority Date: 03/23/1992
• Status: Expired due to Term

• Current Assignee: Motorola Mobility, Inc. (Lenovo Group Ltd.)
• Original Assignee: Motorola, Inc. (Motorola Solutions, Inc.)
• Inventors: Averbuch, Nimrod
• Primary Examiner(s): Kuntz, Curtis
• Assistant Examiner(s): PHAN, HAI
• Application Number:
  US07/856,426
• Time in Patent Office: 540 Days
• Field of Search: 370/104.1, 370/108, 370/103, 375/108, 375/107, 375/109, 375/115, 455/51.1, 455/51.2
• US Class Current: 375/357
• CPC Class Codes: H04H 20/67 Common-wave systems, i.e. using separate transmitters operating on substantially the same frequency
• CPC Class Codes: H04J 3/0682 by delay compensation, e.g. by compensation of propagation delay or variations thereof, by ranging

Abstract

A central-site (100) has located within it a synchronization system for purposes of backing-up a GPS external synchronization system. The central-site (100) is coupled to a plurality of base-sites (102, 103) which are required to be synchronized to one another. When the GPS signal is lost, the synchronization system within the central-site (100) allows the plurality of base-sites (102, 103) to maintain synchronization to one another. In this manner, the necessity for a synchronization system within each of the plurality of base-sites (102,103) is eliminated.

Claims

1. A communication system having a central-site coupled to a plurality of base-sites, the communication system comprising:

means, at the central-site, for providing a synchronization signal;

means, at the central-site and coupled to said means for providing, for measuring a round-trip time delay between the central-site and each of the plurality of base-sites;

means, at each of the plurality of base-sites, for measuring a round-trip time delay; and

means, at either the central-site or each of the plurality of base-sites, for compensating the discrepancies in said measured round-trip time delays between the central-site and each of the plurality of base-sites.

2. The communication system of claim 1 further comprising means for synchronizing the plurality of base-sites to one another utilizing an external synchronization system.

3. The communication system of claim 2 wherein said means for synchronizing the plurality of base-sites to one another utilizing an external synchronization system further comprises means for synchronizing to the global positioning system (GPS).

4. The communication system of claim 1 wherein said means for providing a synchronization signal further comprises either a rubidium standard, a cesium standard, or an oscillator.

5. The communication system of claim 1 wherein said communication system is a code-division multiple access (CDMA) radiotelephone system.

6. The communication system of claim 1 wherein said central-site is coupled to the plurality of base-sites via one of either a T1 link, a JT1 link or a CEPT link.

7. The communication system of claim 1 wherein said central-site is one of either an earth-based central-site or a space-based central-site.

8. A code-division multiple access (CDMA) radiotelephone system having a central-site coupled to a plurality of base-sites, the communication system comprising:

means, at the central-site, for providing a synchronization signal;

means, at the central-site and coupled to said means for providing, for measuring a round-trip time delay between the central-site and each of the plurality of base-sites;

means, at each of the plurality of base-sites, for measuring a round-trip time delay; and

means, at either the central-site or each of the plurality of base-sites, for compensating the discrepancies in said measured round-trip time delays between the central-site and each of the plurality of base-sites.

9. The CDMA radiotelephone system of claim 8 wherein said central-site is coupled to the plurality of base-sites via a T1 link.

10. A method of synchronization in a communication system, the communication system having a central-site coupled to a plurality of base-sites, the method comprising the steps of:

providing, at the central-site, a synchronization signal;

measuring, at the central-site, a round-trip time delay between the central-site and each of the plurality of base-sites;

measuring at each of the plurality of base-sites, a round-trip time delay; and

compensating, at either the central-site or each of the plurality of base-sites, the discrepancies in said measured round-trip time delays between the central-site and each of the plurality of base-sites.

11. A method of maintaining synchronization in a communication system, the communication system having a central-site coupled to a plurality of base-sites, the plurality of base-sites synchronized to one another by an external synchronization system, the method comprising the steps of:

providing, at the central-site, a synchronization signal;

measuring, at the central-site, a first round-trip time delay between the central-site and each of the plurality of base-sites;

measuring, at each of the plurality of base-sites, a second round-trip time delay;

comparing said first round-trip time delay and said second round-trip time delay;

compensating, at either the central-site or each of the plurality of base-sites, the discrepancies in said measured round-trip time delays between the central-site and each of the plurality of base-sites; and

repeating said steps of measuring a first round-trip time delay and measuring a second round-trip time delay.

12. A method of maintaining synchronization in a communication system, the communication system having a central-site coupled to a plurality of base-sites, the plurality of base-sites having been previously synchronized to one another by an external synchronization system, the external synchronization system having been subsequently removed, the method of maintaining synchronization comprising the steps of:

sending, from each of the plurality of base-sites, an initiate backup message to the central-site upon loss of the external synchronization system;

measuring, at the central-site, a round-trip time delay between the central-site and the plurality of base-sites;

measuring, at each of the plurality of base-sites, a round-trip time delay between each of the plurality of base-sites and the central-site;

comparing, at each of the plurality of base-sites, said round-trip time delays measured by each of the plurality of base-sites and the central-site; and

maintaining synchronization among the plurality of base-sites based on said step of comparing.

13. The method of claim 12 wherein said step of measuring, at each of the plurality of base-sites, begins at a predetermined time after said initiate backup message is sent.