Time synchronization method in CDMA system

• US 6,483,825 B2
• Filed: 01/25/1999
• Issued: 11/19/2002
• Est. Priority Date: 07/07/1998
• Status: Expired due to Fees

• Current Assignee: Fujitsu Limited
• Original Assignee: Fujitsu Limited
• Inventors: Seta, Mitsuru
• Primary Examiner(s): Yao, Kwang Bin
• Application Number:
  US09/236,962
• Publication Number:
  US 20020054611A1
• Time in Patent Office: 1,394 Days
• Field of Search: 370/312, 370/315, 370/316, 370/319, 370/320, 370/323, 370/324, 370/325, 370/328, 370/335, 370/342, 370/345, 370/349, 370/350, 370/503, 370/509, 370/510, 370/512, 370/515, 370/516, 370/517, 370/518, 370/519, 375/140, 375/141, 375/145, 375/146, 375/147, 375/149, 375/367, 455/502, 455/503
• US Class Current: 370/335
• 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 signals from GPS satellites and generating a reference time based upon the received signals;

adopting the reference time generated by the GPS receiver as the time of the base station controller; and

measuring a transmission delay time from the base station controller to each base station and regarding the transmission delay time as time correction data;

transmitting, from the base station controller to each base station, data for specifying said reference time and said time correction data for each base station; and

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

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

providing in each base station a phase offset 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 that of the base station controller based upon the reference time specifying data and the time correction data received from said base station controller.

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

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

4. The method according to claim 3, 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.

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

providing in each base station a phase offset 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.

6. A base station controller in a CDMA system which synchronizes the time of a plurality of base stations and the time of a base station controller that controls each of these base stations, comprising:

a GPS receiver for receiving a signal from GPS satellites and generating a reference time based upon the received signal;

a timing means for adopting the reference time generated by the GPS receiver as the time of the base station controller;

means for measuring a transmission delay time from the base station controller to each base station and generating time correction data based upon the transmission delay time; and

transmitting means for transmitting, to each base station, data for specifying said reference time and said time correction data for each base station.

7. A base station in a CDMA system, said CDMA system synchronizes the time of a plurality of base stations and the time of a base station controller that controls each of the plurality of base stations, said base station comprising:

receiving means for receiving data for specifying reference time which is created based upon a signal received in the base station controller from GPS satellites and time correction data which is created based upon a transmission delay time from the base station controller to the base station; and

synchronizing means for synchronizing the time of the base station to that of the base station controller based upon the received data for specifying said reference time and said time correction data.