Method and apparatus for time-aligning transmissions from multiple base stations in a CDMA communication system

• US 7,796,549 B2
• Filed: 01/24/2008
• Issued: 09/14/2010
• Est. Priority Date: 07/09/2001
• Status: Expired due to Fees

• Current Assignee: Qualcomm, Inc.
• Original Assignee: Qualcomm, Inc.
• Inventors: Wheatley, Charles E. III, Willenegger, Serge D., Subrahmanya, Parvathanathan, Grilli, Francesco
• Primary Examiner(s): Nguyen; Brian D
• Application Number:
  US12/019,596
• Publication Number:
  US 20080117835A1
• Time in Patent Office: 964 Days
• Field of Search: 370/252, 370/328, 370/335, 370/342, 370/350, 370/441, 370/509
• US Class Current: 370/328
• 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 in a wireless communication system, comprising:

obtaining, by a terminal, a time difference value for at least a first base station selected from a plurality of base stations in said wireless communication system, the time difference value being a difference between a timing of the first base station and a timing of a reference base station in said wireless communication system;

estimating, by the terminal, an actual timing of the first base station based on the time difference value obtained for the first base station and the timing of the reference base station; and

initiating a search for the first base station by the terminal communicating within the wireless communication system based on the estimated actual timing for the first base station and a resolution of the time difference value.

2. An apparatus in a wireless communication system, comprising:

means for obtaining a time difference value for at least a first base station selected from a plurality of base stations in said wireless communication system, the time difference value for the first base station being a difference between a timing of the first base station and a timing of a reference base station within said wireless communication system;

means for estimating an actual timing of the first base station based on the time difference value obtained for the first base station and the timing of the reference base station; and

means for initiating a search for the first base station by a terminal communicating within the wireless communication system based on the estimated actual timing for the first base station and a resolution of the time difference value.

5. The apparatus as in claim 2 wherein the time difference value is selected from a group consisting of a frame-level time difference value and a chip-level time difference value for each of the plurality of base stations.

3. A terminal in a wireless communication system, comprising:

a data processor for obtaining a time difference value for at least a first base station in the wireless communication system, wherein the time difference value for the first base station is a difference between a timing of the first base station and a timing of a reference base station within the wireless communication system; and

a controller for estimating an actual timing of the first base station based on the time difference value obtained for the first base station and the timing of the reference base station, and to initiate a search for the first base station based on the estimated actual timing for the first base station and a resolution of the time difference value.

6. The terminal as in claim 3 wherein the time difference value is selected from a group consisting of a frame-level time difference value and a chip-level time difference value for each of the plurality of base stations.

4. A computer program product including a computer-readable medium physically embodied with computer-readable program code for:

obtaining, by a terminal, a time difference value for at least a first base station selected from a plurality of base stations in a wireless communication system, the time difference value being a difference between a timing of the first base station and a timing of a reference base station in said wireless communication system;

estimating, by the terminal, an actual timing of the first base station based on the time difference value obtained for the first base station and the timing of the reference base station; and

initiating a search for the first base station by the terminal communicating within the wireless communication system based on the estimated actual timing for the first base station and a resolution of the time difference value.

7. The computer program product as in claim 4 wherein the time difference value is selected from a group consisting of a frame-level time difference value and a chip-level time difference value for each of the plurality of base stations.

8. An apparatus in a wireless communication system, comprising:

circuitry configured to;

obtain a time difference value for a first base station selected from a plurality of base stations in the wireless communication system, the time difference value for the first base station being a difference between a timing of the first base station and a timing of a reference base station in the wireless communication system;

estimate an actual timing of the first base station based on the time difference value obtained for the first base station and the timing of the reference base station; and

initiate a search for the first base station by the apparatus communication within the wireless communication system based on the estimated actual timing for the first base station and a resolution of the time different value.

9. The apparatus as in claim 8 wherein the time difference value is selected from a group consisting of a frame-level time difference value and a chip-level time difference value for each of the plurality of base stations.