Time and frequency acquisition and tracking for OFDMA wireless systems

• US 9,401,784 B2
• Filed: 10/07/2010
• Issued: 07/26/2016
• Est. Priority Date: 10/21/2009
• Status: Active Grant

• Current Assignee: Qualcomm, Inc.
• Original Assignee: Qualcomm, Inc.
• Inventors: Yoo, Taesang, Luo, Tao
• Primary Examiner(s): TALUKDER, MD K
• Application Number:
  US12/900,285
• Publication Number:
  US 20110092231A1
• Time in Patent Office: 2,119 Days
• Field of Search: 455/277.1, 455/133, 455/501, 455/522, 455/63.1, 455/452.1, 455/434, 370/329, 370/328, 370/336
• US Class Current: 1/1
• CPC Class Codes: H04B 1/7097 Interference-related aspects
• CPC Class Codes: H04B 15/00 Suppression or limitation of noise or interference by means associated with receiver H04B1/10
• CPC Class Codes: H04B 2201/70701 featuring pilot assisted reception
• CPC Class Codes: H04B 2201/70702 Intercell-related aspects
• CPC Class Codes: H04J 11/005 of intercell interference
• CPC Class Codes: H04J 11/0069 Cell search, i.e. determining cell identity [cell-ID] design of multiplexing codes H04J13/00; processing access restriction or access information H04W48/16; discovery of network devices for network data management H04W8/005; sounding signals for channel estimation H04L25/0226; structure of reference signals in multicarrier modulation systems H04L27/2613; frame, time or carrier synchronisation in multicarrier modulation systems H04L27/2655
• CPC Class Codes: H04L 27/2657 Carrier synchronisation
• CPC Class Codes: H04L 27/2662 Symbol synchronisation
• CPC Class Codes: H04L 5/0032 Distributed allocation, i.e. involving a plurality of allocating devices, each making partial allocation
• CPC Class Codes: H04L 5/0048 Allocation of pilot signals, i.e. of signals known to the receiver
• CPC Class Codes: H04W 24/02 Arrangements for optimising operational condition
• CPC Class Codes: H04W 72/541 using the level of interference

Abstract

Obtaining a timing reference in wireless communication is facilitated when desiring to communicate with a weak serving base station (such as an evolved NodeB) in the presence of a stronger interfering base station. The user equipment (UE) may track a stronger interfering base station'"'"'s timing, or the UE may track a timing that is derived by a composite power delay profile (PDP) from multiple base stations. The composite PDP may be constructed by adjusting individual base station PDPs according to a weighting scheme. The timing obtained in such a manner may be used for estimation of the channel of the interfering base station and cancelling interfering signals from the base station. It may also be used to estimate the channel of the serving base station after adding a backoff. The UE may track a stronger interfering base station'"'"'s frequency, or the UE may track a composite frequency.

Claims

1. A method operable to acquire a timing of a serving base station in presence of interference from an interfering base station, the method comprising:

acquiring a first reference signal from a first base station, wherein the first base station is the interfering base station;

constructing a first power delay profile (PDP) from the first reference signal;

acquiring a second reference signal from a second base station, wherein the second base station is the serving base station and the second reference signal is weaker than the first reference signal;

constructing a second PDP from the second reference signal;

constructing a composite PDP from the first and second PDPs;

generating a timing reference for a combined signal from the composite PDP;

determining the timing of the weaker serving base station based at least in part on the timing reference for the combined signal; and

tracking and using the determined timing as a timing reference for communicating with the weaker serving base station.

2. The method of claim 1, wherein the first and second base stations are evolved NodeBs in a long term evolution (LTE) network.

3. The method of claim 1, further comprising:

acquiring a third reference signal from a third base station; and

constructing a third PDP from the third reference signal,

wherein the constructing the composite PDP further comprises constructing the composite PDP from the third PDP.

4. The method of claim 1, further comprising canceling the first reference signal prior to acquiring the second reference signal.

5. The method of claim 1, wherein the constructing the composite PDP further comprises applying a weight to the first and second PDPs.

6. The method of claim 5, wherein the weight given to the first and second PDPs is based on a cell type of the first base station and the second base station.

7. The method of claim 6, wherein the cell type of the first base station or the second base station is determined based on one of a Primary Synchronization Signal (PSS), a Secondary Synchronization Signal (SSS), a Physical Broadcast Channel (PBCH), a System Information of the PBCH and a neighbor list.

8. The method of claim 1, further comprising adjusting the timing of the serving base station by an offset.

9. The method of claim 1, wherein constructing a composite PDP from the first and second PDPs comprises combining the first PDP and the second PDP without a corresponding shift in time of either of the first PDP or the second PDP.

10. An apparatus operable to acquire a timing of a serving base station in presence of interference from an interfering base station, the apparatus comprising:

means for acquiring a first reference signal from a first base station, wherein the first base station is the interfering base station;

means for constructing a first power delay profile (PDP) from the first reference signal;

means for acquiring a second reference signal from a second base station, wherein the second base station is the serving base station and the second reference signal is weaker than the first reference signal;

means for constructing a second PDP from the second reference signal;

means for constructing a composite PDP from the first and second PDPs;

means for generating a timing reference for a combined signal from the composite;

means for determining the timing of the weaker serving base station based at least in part on the timing reference for the combined signal; and

means for tracking and using the determined timing as a timing reference for communicating with the weaker serving base station.

11. The apparatus of claim 10, wherein the means for determining is configured to adjust the timing of the serving base station by an offset.

12. The apparatus of claim 10, wherein the means for constructing a composite PDP from the first and second PDPs is configured to combine the first PDP and the second PDP without a corresponding shift in time of either of the first PDP or the second PDP.

13. A computer program product, stored on a non-transitory computer-readable medium, for acquiring a timing of a serving base station in presence of interference from an interfering base station, the computer program product comprising program code to:

acquire a first reference signal from a first base station, wherein the first base station is the interfering base station;

construct a first power delay profile (PDP) from the first reference signal;

acquire a second reference signal from a second base station, wherein the second base station is the serving base station and the second reference signal is weaker than the first reference signal;

construct a second PDP from the second reference signal;

construct a composite PDP from the first and second PDPs;

generate a timing reference for a combined signal from the composite PDP;

determine the timing of the weaker serving base station based at least in part on the timing reference for the combined signal; and

track and use the determined timing as a timing reference for communicating with the weaker serving base station.

14. The computer program product of claim 13, wherein the program code to determine comprises program code to adjust the timing of the serving base station by an offset.

15. The computer program product of claim 13, wherein the program code to generate a timing reference for a combined signal from the composite PDP comprises code to combine the first PDP and the second PDP without a corresponding shift in time of either of the first PDP or the second PDP.

16. An apparatus operable to acquire a timing of a serving base station in presence of interference from an interfering base station, the apparatus comprising:

a memory; and

at least one processor coupled to the memory and configured to;

acquire a first reference signal from a first base station, wherein the first base station is the interfering base station;

construct a first power delay profile (PDP) from the first reference signal;

acquire a second reference signal from a second base station, wherein the second base station is the serving base station and the second reference signal is weaker than the first reference signal;

construct a second PDP from the second reference signal;

construct a composite PDP from the first and second PDPs;

generate a timing reference for a combined signal from the composite PDP;

determine the timing of the weaker serving base station based at least in part on the timing reference for the combined signal; and

track and use the determined timing as a timing reference for communicating with the weaker serving base station.

17. The apparatus of claim 16, wherein the first and second base stations are evolved NodeBs in a long term evolution (LTE) network.

18. The apparatus of claim 16, wherein at least one processor is further configured to:

acquire a third reference signal from a third base station; and

construct a third PDP from the third reference signal,

wherein the at least one processor configured to construct the composite PDP is further configured to construct the composite PDP from the third PDP.

19. The apparatus of claim 16, wherein the at least one processor is further configured, prior to acquiring the second reference signal, to cancel the first reference signal.

20. The apparatus of claim 16, wherein the constructing the composite PDP further comprises applying a weight to the first and second PDPs.

21. The apparatus of claim 20, wherein the weight given to the first and second PDPs is based on a cell type of the first base station and the second base station.

22. The apparatus of claim 21, wherein the cell type of the first base station or the second base station is determined based on one of the following:

a Primary Synchronization Signal (PSS), a Secondary Synchronization Signal (SSS), a Physical Broadcast Channel (PBCH), a System Information of the PBCH and a neighbor list.

23. The apparatus of claim 16, wherein the at least one processor is further configured to adjust the timing of the serving base station by an offset.

24. The apparatus of claim 16, wherein the at least one processor generates a timing reference for a combined signal from the composite PDP by being configured to combine the first PDP and the second PDP without a corresponding shift in time of either of the first PDP or the second PDP.