TIME AND FREQUENCY ACQUISITION AND TRACKING FOR OFDMA WIRELESS SYSTEMS

• US 20110092231A1
• Filed: 10/07/2010
• Published: 04/21/2011
• Est. Priority Date: 10/21/2009
• Status: Active Grant

• Current Assignee: Qualcomm, Inc.
• Original Assignee: Qualcomm, Inc.
• Inventors: Luo, Tao, Yoo, Taesang
• Granted Patent: US 9,401,784 B2
• Time in Patent Office: Days
• US Class Current: 455/501
• 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 for wireless communication with a serving base station in presence of interference from an interfering base station, the method comprising:

acquiring a reference signal from an interfering base station;

obtaining a timing reference from the acquired reference signal of the interfering base station; and

communicating with the serving base station based on the timing reference from the interfering base station.

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

3. The method of claim 1, in which the communicating comprises generating a backed-off timing reference by applying a backoff to the timing reference and communicating with the serving base station using the backed-off timing reference.

4. An apparatus operable in a wireless communication system with a serving base station in presence of interference from an interfering base station, the apparatus comprising:

means for acquiring a reference signal from an interfering base station;

means for obtaining a timing reference from the acquired reference signal of the interfering base station; and

means for communicating with the serving base station based on the timing reference from the interfering base station.

5. A computer program product for wireless communications in a wireless network with a serving base station in presence of interference from an interfering base station, the computer program product comprising:

a computer-readable medium having program code recorded thereon, the program code comprising;

program code to acquire a reference signal from an interfering base station;

program code to obtain a timing reference from the acquired reference signal of the interfering base station; and

program code to communicate with the serving base station based on the timing reference from the interfering base station.

6. An apparatus operable in a wireless communication system with a serving base station in presence of interference from an interfering base station, the apparatus comprising:

at least one processor; and

a memory coupled to the at least one processor, the at least one processor being configured;

to acquire a reference signal from an interfering base station;

to obtain a timing reference from the acquired reference signal of the interfering base station; and

to communicate with the serving base station based on the timing reference from the interfering base station.

7. A method operable in wireless communication system with a serving base station in presence of interference from an interfering base station, the method comprising:

acquiring a first reference signal from a strong interfering base station;

obtaining a first frequency reference from the first reference signal; and

communicating with the serving base station based on the first frequency reference from the interfering base station.

8. The method of claim 7 further comprising:

acquiring a second reference signal from the serving base station;

obtaining a second frequency reference from the second reference signal;

estimating a frequency offset difference between the serving base station and the strong interfering base station using the first and second frequency references; and

compensating for the frequency offset difference in the serving base station.

9. The method of claim 7, in which the interfering and serving base stations are evolved NodeBs in a long term evolution (LTE) network.

10. An apparatus operable in a wireless communication system with 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 strong interfering base station;

means for obtaining a first frequency reference from the first reference signal; and

means for communicating with the serving base station based on the first frequency reference from the interfering base station.

11. A computer program product for wireless communications in a wireless network with a serving base station in presence of interference from an interfering base station, the computer program product comprising:

a computer-readable medium having program code recorded thereon, the program code comprising;

program code to acquire a first reference signal from a strong interfering base station;

program code to obtain a first frequency reference from the first reference signal; and

program code to communicate with the serving base station based on the first frequency reference from the interfering base station.

12. An apparatus operable in a wireless communication system with a serving base station in presence of interference from an interfering base station, the apparatus comprising:

at least one processor; and

a memory coupled to the at least one processor, the at least one processor being configured;

to acquire a first reference signal from a strong interfering base station;

to obtain a first frequency reference from the first reference signal; and

to communicate with the serving base station based on the first frequency reference from the interfering base station.

13. A method operable in wireless communication system with 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;

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

acquiring a second reference signal from a second base station;

constructing a second power delay profile from the second reference signal;

constructing a composite power delay profile from the first and second power delay profiles; and

generating a timing reference for a combined signal from the composite power delay profile.

14. The method of claim 13, in which the first and second base stations are evolved NodeBs in a long term evolution (LTE) network.

15. The method of claim 13, further comprising:

acquiring a third reference signal from a third base station;

constructing a third power delay profile from the third reference signal; and

wherein the constructing the composite power delay profile further comprises constructing the composite power delay profile from the third power delay profile.

16. The method of claim 13, further comprising canceling the first reference signal prior to acquiring the second reference signal.

17. The method of claim 13, in which the constructing the composite power delay profile further comprises applying a weight to the first and second power delay profiles.

18. The method of claim 17, in which the weight given to the first and power delay profiles is based on a cell type of the first base station and the second base station.

19. The method of claim 18 in which 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.

20. An apparatus operable in a wireless communication system with 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;

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;

means for constructing a second power delay profile from the second reference signal;

means for constructing a composite power delay profile from the first and second power delay profiles; and

means for generating a timing reference for a combined signal from the composite power delay profile.

21. A computer program product for wireless communications in a wireless network with a serving base station in presence of interference from an interfering base station, the computer program product comprising:

a computer-readable medium having program code recorded thereon, the program code comprising;

program code to acquire a first reference signal from a first base station;

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

program code to acquire a second reference signal from a second base station;

program code to construct a second power delay profile from the second reference signal;

program code to construct a composite power delay profile from the first and second power delay profiles; and

program code to generate a timing reference for a combined signal from the composite power delay profile.

22. An apparatus operable in a wireless communication system with a serving base station in presence of interference from an interfering base station, the apparatus comprising:

at least one processor; and

a memory coupled to the at least one processor, the at least one processor being configured;

to acquire a first reference signal from a first base station;

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

to acquire a second reference signal from a second base station;

to construct a second power delay profile from the second reference signal;

to construct a composite power delay profile from the first and second power delay profiles; and

to generate a timing reference for a combined signal from the composite power delay profile.

23. The apparatus of claim 22, in which the first and second base stations are evolved NodeBs in a long term evolution (LTE) network.

24. The apparatus of claim 22, in which the processor is further configured:

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

to construct a third power delay profile from the third reference signal; and

wherein the processor is configured to construct the composite power delay profile further comprises the processor being configured to construct the composite power delay profile from the third power delay profile.

25. The apparatus of claim 22, in which the processor is further configured, prior to acquiring the second reference signal, to cancel the first reference signal.

26. The apparatus of claim 22, in which the constructing the composite power delay profile further comprises applying a weight to the first and second power delay profiles.

27. The apparatus of claim 26, in which the weight given to the first and power delay profiles is based on a cell type of the first base station and the second base station.

28. The apparatus of claim 27, in which 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.

29. A method for wireless communication with a serving base station in presence of interference from an interfering base station, the method comprising:

extracting a reference signal from a received signal, the reference signal being associated with a strongest interfering base station from a plurality of detected base stations;

subtracting the reference signal from the received signal;

extracting a plurality of reference signals from the received signal, the plurality of reference signals being associated with the plurality of detected base stations;

subtracting the plurality of reference signals from the received signal;

estimating a composite frequency error using the reference signal and the plurality of reference signals;

enabling a frequency tracking loop based on the composite frequency error;

estimating a plurality of frequency offsets associated with the plurality of detected base stations; and

compensating for a residual frequency error for one of the plurality of detected base stations using the composite frequency error and one of the plurality of frequency offsets associated with the one of the plurality of detected base stations.

30. An apparatus operable in wireless communication system with a serving base station in presence of interference from an interfering base station, the apparatus comprising:

means for extracting a reference signal from a received signal, the reference signal being associated with a strongest interfering base station from a plurality of detected base stations;

means for subtracting the reference signal from the received signal;

means for extracting a plurality of reference signals from the received signal, the plurality of reference signals being associated with the plurality of detected base stations;

means for subtracting the plurality of reference signals from the received signal;

means for estimating a composite frequency error using the reference signal and the plurality of reference signals;

means for enabling a frequency tracking loop based on the composite frequency error;

means for estimating a plurality of frequency offsets associated with the plurality of detected base stations; and

means for compensating for a residual frequency error for one of the plurality of detected base stations using the composite frequency error and one of the plurality of frequency offsets associated with the one of the plurality of detected base stations.

31. A computer program product for wireless communications in a wireless network with a serving base station in presence of interference from an interfering base station, the computer program product comprising:

a computer-readable medium having program code recorded thereon, the program code comprising;

program code to extract a reference signal from a received signal, the reference signal being associated with a strongest interfering base station from a plurality of detected base stations;

program code to subtract the reference signal from the received signal;

program code to extract a plurality of reference signals from the received signal, the plurality of reference signals being associated with the plurality of detected base stations;

program code to subtract the plurality of reference signals from the received signal;

program code to estimate a composite frequency error using the reference signal and the plurality of reference signals;

program code to enable a frequency tracking loop based on the composite frequency error;

program code to estimate a plurality of frequency offsets associated with the plurality of detected base stations; and

program code to compensate for a residual frequency error for one of the plurality of detected base stations using the composite frequency error and one of the plurality of frequency offsets associated with the one of the plurality of detected base stations.

32. An apparatus operable in a wireless communication system with a serving base station in presence of interference from an interfering base station, the apparatus comprising:

at least one processor; and

a memory coupled to the at least one processor, the at least one processor being configured;

to extract a reference signal from a received signal, the reference signal being associated with a strongest interfering base station from a plurality of detected base stations;

to subtract the reference signal from the received signal;

to extract a plurality of reference signals from the received signal, the plurality of reference signals being associated with the plurality of detected base stations;

to subtract the plurality of reference signals from the received signal;

to estimate a composite frequency error using the reference signal and the plurality of reference signals;

to enable a frequency tracking loop based on the composite frequency error;

to estimate a plurality of frequency offsets associated with the plurality of detected base stations; and

to compensate for a residual frequency error for one of the plurality of detected base stations using the composite frequency error and one of the plurality of frequency offsets associated with the one of the plurality of detected base stations.