TIME SYNCHRONIZATION METHOD IN CDMA SYSTEM

• US 20020054611A1
• Filed: 01/25/1999
• Published: 05/09/2002
• Est. Priority Date: 07/07/1998
• Status: Active Grant

• Current Assignee: Fujitsu Limited
• Original Assignee: Fujitsu Limited
• Inventors: SETA, MITSURU
• Granted Patent: US 6,483,825 B2
• Time in Patent Office: Days
• US Class Current: 370/503
• CPC Class Codes: H04B 7/2693 Centralised synchronisation, i.e. using external universal time reference, e.g. by using a global positioning system [GPS] or by distributing time reference over the wireline network
• CPC Class Codes: H04H 20/67 Common-wave systems, i.e. using separate transmitters operating on substantially the same frequency

Abstract

A time synchronization method in a CDMA system for synchronizing the time of a plurality of base stations and the time of a base station controller that controls each of these base stations includes providing the base station controller with a GPS receiver for receiving a signal from GPS satellites and generating a reference time based upon the received signal, adopting the reference time generated by the GPS receiver as the time of the base station controller, creating time reference information based upon this time and sending the time reference information to each base station. Each base station synchronizes its own time to the that of the base station controller based upon the time reference information it has received.

Claims

1. A time synchronization method for synchronizing the time of a plurality of base stations in a CDMA system and the time of a base station controller that controls each of these base stations, comprising the steps of:

providing the base station controller with a GPS receiver for receiving a signal from GPS satellites and generating a reference time based upon the received signal;

adopting the reference time generated by the GPS receiver as the time of the base station controller, creating time reference information based upon this time and sending the time reference information to each base station; and

in each base station, synchronizing the time of each base station to the that of the base station controller based upon the time reference information received by each base station.

2. The method according to claim 1, further comprising the step of periodically transmitting, to each base station as the time reference information, reference time specifying data and time correction data for each base station.

3. The method according to claim 2, wherein each base station synchronizes its own time to that of the base station controller based upon the reference time specifying data and the time correction data received from said base station controller.

4. The method according to claim 2, further comprising the steps of:

providing in each base station a phase offset (inclusive of a phase offset of zero) between frame timing of a receiving signal from the base station controller and frame timing of a transmitting signal to the base station controller;

in the base station controller, measuring a transmission delay time from the base station controller to the base station based upon frame timing of a transmitting signal to the base station, frame timing of a receiving signal from the base station and said phase offset;

transmitting the transmission delay time from the base station controller to each base station as the time correction data; and

in each base station, correcting the time of each base station to the that of the base station controller based upon the reference time specifying data and the time correction data received from said base station controller.

5. The method according to claim 2, further comprising the steps of:

providing in each base station a phase offset (inclusive of a phase offset of zero) between frame timing of a receiving signal from the base station controller and frame timing of a transmitting signal to the base station controller;

in the base station controller, measuring, every n frames, a transmission delay time from the base station controller to the base station based upon frame timing of a transmitting signal to the base station, frame timing of a receiving signal from the base station and said phase offset; and

adopting a reference time that follows n frames as the reference time specifying data, adopting correction information, which is for correcting said reference time that follows the n frames and is based upon the transmission delay time, as the time correction data, and transmitting these items of data from the base station controller to each base station.

6. The method according to claim 5, further comprising the step of each base station making its own time agree with the reference time indicated by the reference time specifying data upon elapse of time indicated by the time correction data after the base station receives the reference time specifying data and the time correction data.

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

providing in each base station a phase offset (inclusive of a phase offset of zero) between frame timing of a receiving signal from the base station controller and frame timing of a transmitting signal to the base station controller;

in the base station controller, measuring a transmission delay time from the base station controller to the base station based upon frame timing of a transmitting signal to the base station, frame timing of a receiving signal from the base station and said phase offset; and

adding this transmission delay time to the reference time to create the time reference information and transmitting this time reference information to each base station;

wherein each base station synchronizes its own time to that of the base station controller based upon the time reference information it has received.