Telecommunications network synchronization for data services

• US 6,256,507 B1
• Filed: 08/31/1998
• Issued: 07/03/2001
• Est. Priority Date: 08/31/1998
• Status: Expired due to Term

• Current Assignee: Telefonaktiebolaget LM Ericsson
• Original Assignee: Telefonaktiebolaget LM Ericsson
• Inventors: Lemieux, Yves
• Primary Examiner(s): BANKS HAROLD, MARSHA DENISE
• Application Number:
  US09/144,795
• Time in Patent Office: 1,037 Days
• Field of Search: 455/422, 455/427, 455/456, 455/12.1, 455/13.2, 455/502, 455/560, 455/561, 370/345, 370/350, 370/324, 342/357.06, 342/357.09, 342/357.1, 375/356
• US Class Current: 455/502
• CPC Class Codes: H04J 3/0644 External master-clock
• CPC Class Codes: H04J 3/0679 by determining clock distribution path in a network
• CPC Class Codes: H04W 56/006 using known positions of transmitter and receiver

Abstract

A star network type topology is implemented for a network synchronization system wherein synchronization information radiates from a centralized primary reference source comprising the global positioning system (GPS). A GPS receiver installed at each mobile switching center and base station of a wireless communications network supplies a stratum 1 classified clock pulse to a local clock. The local clock trains to this clock pulse and generates a corresponding stratum 1 classified synchronization clock pulse for controlling timing operations of the mobile switching center or base station. In the event the GPS primary reference source fails or its accuracy degrades, a change is made to a tree or linear network type topology wherein the synchronization information flows downstream from the mobile switching center local clocks to the base stations. Operation of the network synchronization system is coordinated through a synchronization manager maintained by the transport network management system of the network. Highly accurate synchronization using these topologies supports the provision of value added services such as mobile station locating and information time stamping.

Claims

1. A mobile communications network, comprising:

plurality of mobile switching centers;

a synchronization system implementing a star network type topology mode of operation wherein a global positioning system (GPS) comprises a primary reference source for synchronization, and each mobile switching center includes a global positioning system receiver in communication with the global positioning system and operable to supply a stratum 1 classified clock pulse for use in synchronizing mobile switching center operation and deriving a system clock;

a transport network management system including a synchronization manager functionality for controlling a synchronization mode of operation for the synchronization system; and

means for supporting synchronization mode communication between the transport network management system and the synchronization system.

2. The network as in claim 1 further including a local clock module within each mobile switching center, the local clock module connected to receive the global positioning system receiver supplied stratum 1 classified clock pulse and generate in response thereto a corresponding stratum 1 classified synchronization clock pulse for synchronizing mobile switching center operation to the derived system clock.

3. The network as in claim 2 further including:

a plurality of base stations connected to the mobile switching centers, each base station including a global positioning system receiver in communication with the global positioning system and operable to supply a stratum 1 classified clock pulse for use in synchronizing base station operation and deriving a system clock;

a local clock module within each base station, the local clock module connected to receive the global positioning system receiver supplied stratum 1 classified clock pulse and generate in response thereto a corresponding stratum 1 classified synchronization clock pulse for synchronizing base station operation to the derived system clock;

a clock distribution module within each mobile switching center and base station, the clock distribution module connected to the local clock module; and

a first communications link between each base station clock distribution module and the mobile switching center clock distribution module over which system clock synchronization information is communicated.

4. The network as in claim 3 wherein the first communications link supports unidirectional communication from the mobile switching center clock distribution module to the base station clock distribution module.

5. The network as in claim 3 further including a second communications link between the mobile switching center clock distribution module and clock distribution modules of other mobile switching centers over which system clock synchronization information is communicated.

6. The network as in claim 5 wherein the second communications link supports bidirectional communication between mobile switching center clock distribution modules.

7. A mobile communications network, comprising:

a plurality of mobile switching centers;

a synchronization system implementing a star network type topology mode of operation wherein a global positioning system (GPS) comprises a primary reference source for synchronization, and each mobile switching center includes a global positioning system receiver in communication with the global positioning system and operable to supply a stratum 1 classified clock pulse for use in synchronizing mobile switching center operation and deriving a system clock and further implementing a tree or linear network type topology mode of operation with a local clock within the mobile switching center comprising the primary reference source for synchronization; and

a synchronization manager functionality for selectively configuring the synchronization mode of operation for the synchronization system between the star network type topology and the tree or linear network type topologies.

8. The network as in claim 7 further including:

a plurality of base stations connected to the mobile switching centers, and

a local clock within each base station that is synchronized to the local clock within the mobile switching center when the synchronization system is configured in the tree or linear network type topology modes of operation.

9. A mobile communications network, comprising:

a mobile switching center;

a plurality of base stations connected to the mobile switching center; and

a synchronization system implementing a star network type topology mode of operation wherein a global positioning system (GPS) comprises a primary reference source for synchronization, and each mobile switching center and base station includes a global positioning system receiver in communication with the global positioning system and operable to supply a stratum 1 classified clock pulse for use in synchronizing mobile switching center and base station communications operation and deriving a system clock;

a transport network management system including a synchronization manager functionality for controlling a synchronization mode of operation for the synchronization system; and

means for supporting synchronization mode communication between the transport network management system and the synchronization system.

10. The network as in claim 9 further including a local clock module within each mobile switching center and base station, the local clock module connected to receive the global positioning system receiver supplied stratum 1 classified clock pulse and generate in response thereto a corresponding stratum 1 classified synchronization clock pulse for synchronizing mobile switching center and base station operation to the derived system clock.

11. The network as in claim 10 further including:

a clock distribution module within each mobile switching center and base station, the clock distribution module connected to the local clock module; and

a first communications link between each base station clock distribution module and the mobile switching center clock distribution module over which system clock synchronization information is communicated.

12. The network as in claim 11 wherein the first communications link supports unidirectional communication from the mobile switching center clock distribution module to the base station clock distribution module.

13. The network as in claim 11 further including a second communications link between the mobile switching center clock distribution module and clock distribution modules of other mobile switching centers over which system clock synchronization information is communicated.

14. The network as in claim 13 wherein the second communications link supports bidirectional communication between mobile switching center clock distribution modules.

15. The network as in claim 9 wherein the means for supporting comprises a separate data communications network established between the mobile switching center and base stations.

16. The network as in claim 9 wherein the means for supporting comprises an embedded operations and maintenance channel supported by communications links interconnecting mobile switching centers and base stations.

17. The network as in claim 9:

wherein the mobile switching center is connected for telephonic communication with a public switched telephone network (PSTN);

wherein the synchronization system further implements a linear network type topology mode of operation with pulse code modulated communications links of the public switched telephone network comprising the primary reference source for synchronization; and

wherein the synchronization manager functionality of the transport network management system selectively configures the synchronization mode of operation for the synchronization system between the star network type topology and the linear network type topology.

18. A mobile communications network, comprising:

a mobile switching center;

a plurality of base stations connected to the mobile switching center;

a synchronization system implementing a star network type topology mode of operation wherein a global positioning system (GPS) comprises a primary reference source for synchronization, and each mobile switching center and base station includes a global positioning system receiver in communication with the global positioning system and operable to supply a stratum 1 classified clock pulse for use in synchronizing mobile switching center and base station communications operation and deriving a system clock and further implementing a linear network type topology mode of operation with a local clock within the mobile switching center comprising the primary reference source for synchronization; and

a synchronization manager functionality for selectively configuring the synchronization mode of operation for the synchronization system between the star network type topology and the linear network type topology.

19. The network as in claim 18 further including a local clock within each base station that is synchronized to the local clock within the mobile switching center when the synchronization system is configured in the linear network type topology mode of operation.

20. The network as in claim 18 wherein the local clock within the mobile switching center is synchronized to a global positioning system clock pulse when the synchronization system is configured in the star network type topology mode of operation, and further including a local clock within each base station that is also synchronized to the global positioning system clock pulse when the synchronization system is configured in the star network type topology mode of operation.