CELL DETECTION WITH INTERFERENCE CANCELLATION

• US 20100029262A1
• Filed: 06/18/2009
• Published: 02/04/2010
• Est. Priority Date: 08/01/2008
• Status: Active Grant

• Current Assignee: Qualcomm, Inc.
• Original Assignee: Qualcomm, Inc.
• Inventors: Bhushan, Naga, Palanki, Ravi, Wang, Michael M.
• Granted Patent: US 9,277,487 B2
• Time in Patent Office: Days
• US Class Current: 455/423
• CPC Class Codes: H04B 1/7107 Subtractive interference cancellation
• CPC Class Codes: H04J 11/004 using regenerative subtractive interference cancellation
• CPC Class Codes: H04J 11/0093 Neighbour cell search
• CPC Class Codes: H04W 48/16 Discovering, processing access restriction or access information
• CPC Class Codes: H04W 64/003 locating network equipment

Abstract

Techniques for performing cell detection with interference cancellation are described. In an aspect, a user equipment (UE) may detect for pilots from cells in a wireless network using interference cancellation. The UE may process a received signal to detect for pilots from one or more cells. The pilots may be common pilots transmitted with a reuse factor of one or low reuse pilots transmitted with a reuse factor greater than one. The UE may estimate the interference from a detected cell (e.g., the strongest detected cell) and may cancel the estimated interference from the received signal. The UE may then process the interference-canceled signal to detect for pilots from additional cells. The UE may be able to detect pilots from more cells, e.g., from weaker cells, by canceling the interference due to the pilots from the detected cells. This may be desirable for various applications such as positioning.

Claims

1. A method of detecting for cells in a wireless communication network, comprising:

obtaining a received signal comprising pilots transmitted by a plurality of cells in the wireless network; and

processing the received signal with interference cancellation to detect for the pilots from the plurality of cells, the interference cancellation improving the number of detected cells.

2. The method of claim 1, wherein the processing the received signal with interference cancellation comprises

processing the received signal to detect for at least one pilot from at least one cell,

identifying a strongest cell among the at least one cell,

estimating interference due to a pilot from the strongest cell,

canceling the estimated interference from the received signal to obtain an interference-canceled signal, and

processing the interference-canceled signal to detect for at least one additional pilot from at least one additional cell.

3. The method of claim 1, wherein the processing the received signal with interference cancellation comprises

performing pilot detection and interference cancellation in multiple stages, and for each stage

detecting one or more pilots from one or more cells,

selecting at least one cell for interference cancellation from among the one or more detected cells, and

canceling interference due to the at least one selected cell.

4. The method of claim 3, wherein a strongest cell among the one or more detected cells is selected for interference cancellation in each stage.

5. The method of claim 3, wherein the canceling interference due to the at least one selected cell comprises, for each selected cell,

deriving a channel estimate for the selected cell after canceling interference from prior selected cells,

generating a pilot for the selected cell, and

estimating interference due to the selected cell based on the generated pilot and the channel estimate for the selected cell.

6. The method of claim 3, wherein the processing the received signal with interference cancellation comprises terminating the pilot detection and interference cancellation when no more pilots are detectable.

7. The method of claim 3, wherein the processing the received signal with interference cancellation comprises terminating the pilot detection and interference cancellation when all cells in a list of cells have been detected, or when a predetermined number of cells have been detected, or when a termination condition is encountered.

8. The method of claim 1, further comprising:

obtaining time measurements for multiple detected cells based on pilots from the detected cells; and

obtaining a location estimate for a user equipment (UE) based on the time measurements for the multiple detected cells, the location estimate having improved accuracy due to a higher number of detected cells with interference cancellation.

9. The method of claim 1, further comprising:

identifying multiple detected cells based on pilots from the detected cells; and

obtaining a location estimate for a user equipment (UE) based on identities of the multiple detected cells, the location estimate having improved accuracy due to a higher number of detected cells with interference cancellation.

10. The method of claim 1, wherein the pilots comprise common pilots transmitted by the plurality of cells with a reuse factor of one.

11. The method of claim 1, wherein the pilots comprise low reuse pilots transmitted by the plurality of cells with a reuse factor greater than one.

12. The method of claim 11, wherein each cell transmits a low reuse pilot on a subset of time slots available for transmitting the low reuse pilots.

13. The method of claim 11, wherein each cell transmits a low reuse pilot on a subset of subcarriers available for transmitting the low reuse pilots.

14. An apparatus for wireless communication, comprising:

means for obtaining a received signal comprising pilots transmitted by a plurality of cells in a wireless communication network; and

means for processing the received signal with interference cancellation to detect for the pilots from the plurality of cells, the interference cancellation improving the number of detected cells.

15. The apparatus of claim 14, wherein the means for processing the received signal with interference cancellation comprises

means for processing the received signal to detect for at least one pilot from at least one cell,

means for identifying a strongest cell among the at least one cell,

means for estimating interference due to a pilot from the strongest cell,

means for canceling the estimated interference from the received signal to obtain an interference-canceled signal, and

means for processing the interference-canceled signal to detect for at least one additional pilot from at least one additional cell.

16. The apparatus of claim 14, wherein the means for processing the received signal with interference cancellation comprises

means for performing pilot detection and interference cancellation in multiple stages,

means for detecting one or more pilots from one or more cells in each stage,

means for selecting at least one cell for interference cancellation from among the one or more detected cells, and

means for canceling interference due to the at least one selected cell.

17. The apparatus of claim 14, further comprising:

means for obtaining time measurements for multiple detected cells based on pilots from the detected cells; and

means for obtaining a location estimate for a user equipment (UE) based on the time measurements for the multiple detected cells, the location estimate having improved accuracy due to a higher number of detected cells with interference cancellation.

18. An apparatus for wireless communication, comprising:

at least one processor configured to obtain a received signal comprising pilots transmitted by a plurality of cells in a wireless communication network, and to process the received signal with interference cancellation to detect for the pilots from the plurality of cells, the interference cancellation improving the number of detected cells.

19. The apparatus of claim 18, wherein the at least one processor is configured to process the received signal to detect for at least one pilot from at least one cell, to identify a strongest cell among the at least one cell, to estimate interference due to a pilot from the strongest cell, to cancel the estimated interference from the received signal to obtain an interference-canceled signal, and to process the interference-canceled signal to detect for at least one additional pilot from at least one additional cell.

20. The apparatus of claim 18, wherein the at least one processor is configured to perform pilot detection and interference cancellation in multiple stages and, for each stage, to detect one or more pilots from one or more cells, to select at least one cell for interference cancellation from among the one or more detected cells, and to cancel interference due to the at least one selected cell.

21. The apparatus of claim 18, wherein the at least one processor is configured to obtain time measurements for multiple detected cells based on pilots from the detected cells, and to obtain a location estimate for a user equipment (UE) based on the time measurements for the multiple detected cells, the location estimate having improved accuracy due to a higher number of detected cells with interference cancellation.

22. A computer program product, comprising:

a computer-readable medium comprising;

code for causing at least one computer to obtain a received signal comprising pilots transmitted by a plurality of cells in a wireless communication network, and

code for causing the at least one computer to process the received signal with interference cancellation to detect for the pilots from the plurality of cells, the interference cancellation improving the number of detected cells.