Operation of wideband code division multiple access base stations

• US 20030007471A1
• Filed: 08/13/2001
• Published: 01/09/2003
• Est. Priority Date: 07/03/2001
• Status: Abandoned Application

• Current Assignee: Qualcomm, Inc.
• Original Assignee: Qualcomm, Inc.
• Inventors: Agrawal, Avneesh, Terasawa, Daisuke
• Application Number:
  US09/929,557
• Publication Number:
  US 20030007471A1
• Time in Patent Office: Days
• US Class Current: 370/335
• CPC Class Codes: H04B 7/2668 Arrangements for Wireless Code-Division Multiple Access [CDMA] System Synchronisation, for code acquisition H04B1/7075, for code tracking H04B1/7085
• CPC Class Codes: H04W 56/0015 one node acting as a reference for the others
• CPC Class Codes: H04W 56/009 Closed loop measurements

Abstract

A wideband code division multiple access system supports asynchronous operation, with each base station having its own time reference. Substantial benefits may be realized by operating the WCDMA system in a quasi-synchronous mode, in which the base stations broadcast the relative time difference between their time references and the time references of their neighbor base stations. The WCDMA system supports techniques for measuring the relative time difference.

Claims

1. In a WCDMA system including a radio network controller for controlling a plurality of base stations in communication with at least one mobile station, a method comprising:

receiving a first time difference, the first time difference corresponding to the difference in time of receipt at the mobile station of a downlink signal transmitted from each of at least a first base station and a second base station;

generating a relative time difference as a function of at least the first time difference; and

broadcasting the relative time difference by at least one of the first and second base stations.

2. The method of claim 1, further comprising:

measuring, at the first and second base stations, a round trip delay for the downlink signal and an associated uplink signal,

the relative time difference is further a function of the round trip delays.

3. The method of claim 2, wherein measuring a round trip delay at the first base station comprises:

measuring a first delay for a downlink signal transmitted from the first base station and an uplink signal to the first base station; and

subtracting a known time delay from the first delay.

4. The method of claim 1, further comprising:

receiving a second time difference, the second time difference corresponding to the difference in time of receipt at a second mobile station of a second downlink signal transmitted from each of at least the first and second base stations,

wherein the relative time difference is a function of the first time difference and the second time difference.

5. The method of claim 1, further comprising:

receiving a second time difference, the second time difference corresponding to the difference in time of receipt at a second mobile station of a second downlink signal transmitted from the first base station and a third base station

generating a second relative time difference as a function of at least the second time difference; and

broadcasting the second relative time difference by at least one of the first and third base stations.

6. A digital signal storage medium embodying machine readable instructions executable by a digital signal processing apparatus in a WCDMA system, wherein the machine readable instructions are capable of governing a function of a hardware device, and wherein said machine readable instructions cause a hardware device to:

receive a first time difference, the first time difference corresponding to the difference in time of receipt at a mobile station of a downlink signal transmitted from each of at least a first base station and a second base station;

generate a relative time difference as a function of at least the first time difference; and

broadcast a relative time difference by at least one of the first and second base stations.

7. The medium of claim 6, the machine readable instructions further causing a hardware device to:

measure, at the first and second base stations, a round trip delay for the downlink signal transmitted and an associated uplink signal,

wherein the relative time difference is a function of the first time difference, the second time difference and the round trip delay.

8. The medium of claim 7, wherein measuring a round trip delay at the first base station comprises:

measuring a first delay for a downlink signal transmitted from the first base station and an uplink signal to the first base station; and

subtracting a known time delay from the first delay.

9. The medium of claim 6, the machine readable instructions further causing a hardware device to:

receive a second time difference, the second time difference corresponding to the difference in time of receipt at a second mobile station of a second downlink signal transmitted from each of at least the first and second base stations,

wherein the relative time difference is a function of the first time difference and the second time difference.

10. The medium of claim 6, the machine readable instructions further causing a hardware device to:

receive a second time difference, the second time difference corresponding to the difference in time of receipt at a second mobile station of a second downlink signal transmitted from the first base station and a third base station;

generate a second relative time difference as a function of at least the second time difference; and

broadcast a second relative time difference by at least one of the first and third base stations.

11. A wideband code division multiple access system comprising:

a first base station that uses a first time reference;

a second base station that uses a second time reference; and

a controller that computes a relative time difference as a function of the difference in time of receipt at a mobile station of a downlink signal transmitted from each of at least the first base station and the second base station.

12. The system of claim 11, wherein the controller further:

measures, at the first and second base stations, a round trip delay for the downlink signal and an associated uplink signal; and

calculates the relative time difference as a function of the round trip delays.

14. The system of claim 13,

wherein the first base station uses a first time reference,

wherein the second base station uses a second time reference,

wherein the relative time difference is a function of the difference between the first time reference and the second time reference.

16. The method of claim 15, further comprising acquiring frame timing of the second base station.

17. The method of claim 15, further comprising:

receiving a downlink signal transmitted from the first base station;

receiving the downlink signal transmitted from the second base station;

transmitting a first time difference, the first time difference corresponding to the difference in time of receipt the downlink signal transmitted from each of the first base station and the second base station.

19. The medium of claim 18, the machine readable instructions further causing a hardware device to acquire frame timing of the second base station.

20. The medium of claim 18, the machine readable instructions further causing a hardware device to:

receive a downlink signal transmitted from the first base station;

receive the downlink signal transmitted from the second base station;

transmit a first time difference, the first time difference corresponding to the difference in time of receipt the downlink signal transmitted from each of the first base station and the second base station.

13. A wideband code division multiple access system comprising:

a first base station that communicates with a mobile station;

a second base station that communicates with the mobile station; and

a controller,

wherein the controller measures, at the first and second base stations, a round trip delay for the downlink signal and an associated uplink signal,

wherein the controller receives from the mobile station a first time difference, the first time difference corresponding to the difference in time of receipt at the mobile station of a downlink signal transmitted from each of at least a first base station and a second base station,

wherein the controller computes a relative time difference as a function of the measured round trip delays and the first time difference, and

wherein at least one of the first base station and the second base station broadcasts the relative time difference.

15. A method comprising:

receiving a relative time difference transmitted by a first base station in a wideband code division multiple access system, the relative time difference being a function of the difference between a first time reference used by the first base station and a second time reference used by a second base station;

receiving from the first base station the first time reference used by a first base station; and

calculating the frame timing of the second base station as a function of the first time reference and the relative time difference.

18. A digital signal storage medium embodying machine readable instructions executable by a digital signal processing apparatus, wherein the machine readable instructions are capable of governing a function of a hardware device, and wherein said machine readable instructions cause a hardware device to:

receive from a first base station in a wideband code division multiple access system a relative time difference, the relative time difference being a function of the difference between a first time reference used by the first base station and a second time reference used by a second base station;

receive from the first base station the first time reference used by a first base station; and

calculate the frame timing of the second base station as a function of the first time reference and the relative time difference.