Method and apparatus for synchronizing a base station in a communication system

• US 6,112,100 A
• Filed: 01/23/1998
• Issued: 08/29/2000
• Est. Priority Date: 01/23/1998
• Status: Expired due to Term

• Current Assignee: Google Technology Holdings LLC (Alphabet Inc.)
• Original Assignee: Motorola, Inc. (Motorola Solutions, Inc.)
• Inventors: Ossoinig, Karl Heinz, Goldberg, Steven Jeffrey, Hill, Thomas Casey
• Primary Examiner(s): Nguyen, Lee
• Application Number:
  US09/012,514
• Time in Patent Office: 949 Days
• Field of Search: 455/502, 455/503, 455/524, 455/67.1, 455/67.3, 370/350, 370/503, 370/328, 375/356, 375/365
• US Class Current: 455/502
• CPC Class Codes: H04W 56/0015 one node acting as a reference for the others
• CPC Class Codes: H04W 56/005 compensating for timing error by adjustment in the receiver
• CPC Class Codes: H04W 92/20 between access points

Abstract

A method and apparatus synchronize a first floating timing reference (207) of a first base station (116) with a timing reference of a second base station (116) of a communication system, without requiring an interruption of normal user traffic through the communication system. A receiver (208) of the first base station monitors (402) a user traffic transmission of the second base station, thereby generating a received signal, and a processing system (206) of the first base station derives (410) a received timing reference (308) from the received signal. The processing system independently adjusts (426, 428) the first floating timing reference according to the received timing reference, without requiring a timing adjustment instruction from a centralized synchronization controller.

Claims

1. A method for synchronizing a first floating timing reference of a first base station with a timing reference of a second base station of a communication system, without requiring an interruption of normal user traffic through the communication system, the method comprising in the first base station the steps of:

utilizing, for transmitting the normal user traffic, a transmission protocol that requires both simulcast transmissions and non-simulcast, location-directed transmissions, so that monitoring of the second base station can occur during predetermined time intervals when the first base station is silenced for ones of the location-directed transmissions of the second base station;

monitoring a user traffic transmission of the second base station only during said predetermined time intervals, by a receiver of the first base station, thereby generating a received signal;

deriving a received timing reference from the received signal; and

independently adjusting the first floating timing reference by a predetermined fraction of a time difference between the first floating timing reference and the received timing reference, the predetermined fraction being less than unity, without requiring a timing adjustment instruction from a centralized synchronization controller.

2. The method of claim 1,

wherein the deriving step comprises the step of correcting the received timing reference according to an estimated transmission delay between the first and second base stations.

3. The method of claim 1,

wherein the monitoring step comprises the step of monitoring a plurality of second base stations, thereby generating a plurality of received signals, and

wherein the adjusting step comprises the step of adjusting the first floating timing reference as a function of a corresponding plurality of received timing references derived from the plurality of received signals.

4. The method of claim 1, further comprising the step of

disallowing transmissions by the first base station until the first base station achieves a predetermined level of synchronization with the second base station,

wherein the adjusting step comprises the step of adjusting the first floating timing reference by a time difference between the first floating timing reference and the received timing reference.

5. The method of claim 1,

wherein the adjusting step comprises the step of adjusting the first floating timing reference by no more than a predetermined limit.

6. The method of claim 1, further comprising in the first base station the steps of:

maintaining a history of actions taken during previously executed adjusting steps;

comparing an action indicated for a current adjusting step with the history of actions; and

generating an alert when the comparing step detects that the action indicated is not converging on synchronization.

7. The method of claim 1, further comprising the steps of:

transmitting, by the second base station, location information identifying a geographic location at which the second base station is positioned; and

determining, by the first base station, an estimated transmission delay between the first and second base stations, by comparing the location information with corresponding location information stored in the first base station and identifying the geographic location of the first base station.

8. The method of claim 1,

wherein the first base station operates in a first communication system, and

wherein the second base station operates in a second communication system different from the first communication system, and

wherein the first floating timing reference of the first base station provides a common timing reference utilized for a plurality of base stations in the first communication system, and

wherein the adjusting step comprises the step of adjusting the common timing reference according to the received timing reference.

9. The method of claim 1, further comprising in a controller of the communication system the step of

generating artificial user traffic through the second base station when actual user traffic through the second base station is below a predetermined threshold.

10. The method of claim 1,

wherein the monitoring step comprises the step of monitoring a plurality of second base stations, thereby generating a plurality of received signals, and

wherein the deriving step comprises the step of deriving a plurality of timing references that indicate a requirement for conflicting adjustments of the first floating timing reference, and

wherein, in response to the requirement, the adjusting step comprises the step of adjusting the first floating timing reference in accordance with a pre-programmed technique for handling an adjustment conflict, and

wherein the method further comprises the step of generating an alert in response to the requirement.

11. A first base station for synchronizing a first floating timing reference of the first base station with a timing reference of a second base station of a communication system, without requiring an interruption of normal user traffic through the communication system, the first base station comprising:

a first transmitter for transmitting user traffic in synchronism with a second transmitter of the second base station;

a receiver for monitoring a user traffic transmission of the second base station only during predetermined time intervals, thereby generating a received signal;

a processing system coupled to the receiver for deriving a received timing reference from the received signal, and coupled to the first transmitter for controlling the first transmitter;

the first floating timing reference coupled to the processing system for providing a timing signal for the first base station; and

a controller interface coupled to the processing system for receiving the user traffic from a system controller,

wherein the processing system is programmed to;

control the first transmitter to utilize, for the normal user traffic, a transmission protocol that requires both simulcast transmissions and non-simulcast, location-directed transmissions, so that monitoring of the second base station can occur during said predetermined time intervals when the first base station is silenced for ones of the location-directed transmissions of the second base station; and

independently adjust the first floating timing reference by a predetermined fraction of a time difference between the first floating timing reference and the received timing reference, the predetermined fraction being less than unity, without requiring a timing adjustment instruction from a centralized synchronization controller.

12. The first base station of claim 11, wherein the processing system is further programmed to correct the received timing reference according to an estimated transmission delay between the first and second base stations.

13. The first base station of claim 11,

wherein the processing system is further programmed to adjust the first floating timing reference as a function of a corresponding plurality of received timing references derived from a plurality of received signals, in response to the receiver monitoring a plurality of second base stations, thereby generating the plurality of received signals.

14. The first base station of claim 11, further comprising the step of

wherein the processing system is further programmed to:

disallow transmissions by the first base station until the first base station achieves a predetermined level of synchronization with the second base station; and

adjust the first floating timing reference by a time difference between the first floating timing reference and the received timing reference.

15. The first base station of claim 11,

wherein the processing system is further programmed to adjust the first floating timing reference by no more than a predetermined limit.

16. The first base station of claim 11, wherein the processing system is further programmed to:

maintain a history of actions taken during previously executed adjusting steps;

compare an action indicated for a current adjusting step with the history of actions; and

generate an alert when the processing system detects that the action indicated is not converging on synchronization.

17. The first base station of claim 11,

wherein the second base station is arranged to transmit location information identifying a geographic location at which the second base station is positioned;

and

wherein the processing system is further programmed to determine an estimated transmission delay between the first and second base stations, by comparing the location information with corresponding location information stored in the first base station and identifying the geographic location of the first base station.

18. The first base station of claim 11,

wherein the first base station is arranged and coupled to operate in a first communication system, and

wherein the second base station is arranged and coupled to operate in a second communication system different from the first communication system, and

wherein the first floating timing reference of the first base station is arranged to provide a common timing reference utilized for a plurality of base stations in the first communication system.

19. The first base station of claim 11,

wherein the processing system is further programmed to derive a plurality of timing references, in response to the receiver'"'"'s monitoring a plurality of second base stations, thereby generating a plurality of received signals, and

wherein, in response to the plurality of received signals indicating a requirement for conflicting adjustments of the first floating timing reference, the processing system is further programmed to adjust the first floating timing reference in accordance with a pre-programmed technique for handling an adjustment conflict, and

wherein the processing system is further programmed to generate an alert in response to the requirement.