METHOD AND APPARATUS FOR TIME-ALIGNING TRANSMISSIONS FROM MULTIPLE BASE STATIONS IN A CDMA COMMUNICATION SYSTEM

• US 20100260155A1
• Filed: 05/03/2010
• Published: 10/14/2010
• Est. Priority Date: 07/09/2001
• Status: Active Grant

• Current Assignee: Qualcomm, Inc.
• Original Assignee: Qualcomm, Inc.
• Inventors: Wheatley, Charles E. III, Subrahmanya, Parvathanathan, Grilli, Francesco, Willenegger, Serge
• Granted Patent: US 8,477,742 B2
• Time in Patent Office: Days
• US Class Current: 370/336
• CPC Class Codes: H04B 2201/70702 Intercell-related aspects
• 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 56/001 Synchronization between nodes
• CPC Class Codes: H04W 56/0015 one node acting as a reference for the others
• CPC Class Codes: H04W 56/002 Mutual synchronization
• CPC Class Codes: H04W 56/0045 compensating for timing error by altering transmission time
• CPC Class Codes: H04W 92/20 between access points

Abstract

Schemes to time-align transmissions from multiple base stations to a terminal. To achieve time-alignment, differences between the arrival times of transmissions from the base stations, as observed at the terminal, are determined and provided to the system and used to adjust the timing at the base stations such that terminal-specific radio frames arrive at the terminal within a particular time window. In one scheme, a time difference between two base stations is partitioned into a frame-level time difference and a chip-level time difference. Whenever requested to perform and report time difference measurements, the terminal measures the chip-level timing for each candidate base station relative to a reference base station. Additionally, the terminal also measures the frame-level timing and includes this information in the time difference measurement only if required. Otherwise, the terminal sets the frame-level part to a predetermined value (e.g., zero).

Claims

1. A method of communications, comprising:

receiving coarse timing measurements from first and second base stations;

receiving fine timing measurements from the first and second base stations;

computing a time difference between the first and second base stations based on the course time measurements and the fine time measurements; and

sending the time difference to at least one of the first and second base stations.

2. The method as in claim 1 wherein each of the coarse time measurements is a frame-level timing measurement and each of the fine time measurements is a chip-level measurement.

3. The method as in claim 1 wherein the time difference is a fine full-range time difference, said method further comprising computing the fine full-range time difference by:

computing a coarse full-range time difference between the first and second base stations;

computing a fine partial-range time difference between the first and second base stations; and

computing the fine full-range time difference by combining the full-range time difference and the fine partial-range time difference.

4. The method as in claim 3 further comprising computing the difference of the system frame numbers of the first and second base stations as the coarse full-range time difference.

10. The apparatus as in claim 3 further comprising means for computing the difference of the relative time measurements of the first and second base stations as the line partial-range time difference.

5. The method as in claim 46 further comprising computing the difference of the relative time measurements of the first and second base stations as the fine partial-range time difference.

6. An apparatus operable in a communication system, comprising:

means for receiving coarse time measurements from first and second base stations;

means for receiving fine time measurements from the first and second base stations;

means for computing a time difference between the first and second base stations based on the course time measurements and the fine time measurements; and

means for sending the time difference to at least ore of the first and second base stations.

7. The apparatus as in claim 6 wherein each of the coarse time measurements is a frame-level time measurement and each of the fine time measurements is a chip-level measurement.

8. The apparatus as in claim 6 wherein the time difference is a fine full-range time difference, said apparatus further comprising:

means for computing a coarse full-range time difference between the first and second base stations;

means for computing a fine partial-range time difference between the first and second base stations; and

means for computing the fine full-range time difference by combining the full-range time difference and the fine partial-range time difference.

9. The apparatus as in claim 8 further comprising means for computing the difference of the system frame numbers of the first and second base stations as the coarse full-range time difference.

11. An apparatus operable in a communication system, comprising:

a controller; and

circuitry coupled to the controller configured to;

receive coarse time measurements from first and second base stations;

receive fine time measurements from the first and second base stations;

compute a time difference between the first and second base stations based on the course time measurements and (he fine time measurements; and

send the time difference to at least one of the first and second base stations.

12. The apparatus as in claim 11 wherein each of the coarse time measurements is a frame-level timing measurement and each of the fine time measurements is a chip-level measurement.

13. The apparatus as in claim 11 wherein the time difference is a fine full-range time difference, the circuitry and the controller are further configured to:

compute a coarse full-range time difference between the first and second base stations;

compute a fine partial-range time difference between the first and second base stations; and

compute the fine full-range time difference by combining the full-range time difference and the fine partial-range time difference.

14. The apparatus as in claim 13 wherein the circuitry and the controller are further configured to compute the difference of the system frame numbers of the first and second base stations as the coarse full-range time difference.

15. The apparatus as in claim 11 wherein the circuitry and the controller are further configured to compute the difference of the relative time measurements of the first and second base stations as the fine partial-range time difference.