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1. (WO2009142654) ESTIMATION OF DATA-TO-PILOT RATIO IN A WIRELESS COMMUNICATION SYSTEM
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CLAIMS

1. A method for wireless communication, comprising: estimating channel gain and noise variance based on received pilot; and estimating a data-to-pilot ratio based on received data and the estimated channel gain and noise variance.

2. The method of claim 1, further comprising: receiving pilot sent on a shared channel to multiple terminals; and receiving data sent on the shared channel to a specific terminal.

3. The method of claim 1, wherein the estimating the data-to-pilot ratio comprises determining a first quantity based on the received data and the estimated noise variance, determining a second quantity based on the estimated channel gain, and estimating the data-to-pilot ratio based on the first and second quantities.

4. The method of claim 1, wherein the received data comprises multiple received data symbols, and wherein the data-to-pilot ratio is estimated based on a metric

y, l 2 - <χ,2

\K

where i is an index for the received data symbols, yr represents z-th received data symbol, h, represents estimated channel gain for the z-th received data symbol, and σf represents estimated noise variance for the z-th received data symbol.

5. The method of claim 4, wherein the estimating the data-to-pilot ratio comprises averaging the metric across the multiple received data symbols, and determining the data-to-pilot ratio based on the averaged metric.

6. The method of claim 4, wherein the estimating the data-to-pilot ratio comprises averaging numerator of the metric across the multiple received data symbols, averaging denominator of the metric across the multiple received data symbols, and determining the data-to-pilot ratio based on the averaged numerator and the averaged denominator.

7. The method of claim 4, wherein the estimating the data-to-pilot ratio comprises scaling numerator of the metric with a scaling factor determined based on the estimated channel gain, scaling denominator of the metric with the scaling factor, averaging the scaled numerator across the multiple received data symbols, averaging the scaled denominator across the multiple received data symbols, and determining the data-to-pilot ratio based on the averaged scaled numerator and the averaged scaled denominator.

8. The method of claim 4, wherein the estimating the data-to-pilot ratio comprises constraining numerator of the metric or a quantity derived based on the numerator of the metric to be non-negative.

9. The method of claim 1, further comprising: deriving log-likelihood ratios (LLRs) for code bits based on the received data and the estimated data-to-pilot ratio; and decoding the LLRs to obtain decoded data.

10. The method of claim 1, further comprising: receiving at least one pilot symbol and at least one data symbol sent on multiple subcarriers with orthogonal frequency division multiplexing (OFDM), wherein the received pilot comprises the at least one received pilot symbol and the received data comprises the at least one received data symbol.

11. A method for wireless communication, comprising: receiving pilot via multiple receive antennas; receiving data via the multiple receive antennas; combining the received data across the multiple receive antennas to obtain combined data; estimating signal-to-noise-and-interference ratio (SINR) based on the received pilot from the multiple receive antennas; and estimating a data-to-pilot ratio based on the combined data and the estimated SINR.

12. The method of claim 11 , wherein the estimating the SINR comprises estimating channel gain and noise variance for each receive antenna based on the pilot received via the receive antenna, and estimating the SINR based on estimated channel gain and noise variance for the multiple receive antennas.

13. The method of claim 11, wherein the combining the received data comprises combining the received data across the multiple receive antennas with maximal ratio combining (MRC) to obtain the combined data.

14. The method of claim 11, wherein the combined data comprises multiple combined data symbols, and wherein the data-to-pilot ratio is estimated based on a metric

- SINR

SINR;

where i is an index for the combined data symbols, Z1 represents z-th combined data symbol, and SINR1 represents estimated SINR for the z-th combined data symbol.

15. The method of claim 11, wherein the estimating the data-to-pilot ratio comprises constraining numerator of the metric or a quantity derived based on the numerator of the metric to be non-negative.

16. The method of claim 11 , wherein the combined data comprises combined data symbols from multiple tiles, and wherein the data-to-pilot ratio is estimated for each tile based on pilot symbols from the tile and combined data symbols from the multiple tiles.

17. An apparatus for wireless communication, comprising: at least one processor configured to estimate channel gain and noise variance based on received pilot, and to estimate a data-to-pilot ratio based on received data and the estimated channel gain and noise variance.

18. The apparatus of claim 17, wherein the at least one processor is configured to determine a first quantity based on the received data and the estimated noise variance, to determine a second quantity based on the estimated channel gain, and to estimate the data-to-pilot ratio based on the first and second quantities.

19. The apparatus of claim 17, wherein the received data comprises multiple received data symbols, and wherein the data-to-pilot ratio is estimated based on a metric

y, - <y.

\ k

where i is an index for the received data symbols, yt represents z-th received data symbol, H1 represents estimated channel gain for the z-th received data symbol, and σ] represents estimated noise variance for the z-th received data symbol.

20. The apparatus of claim 19, wherein the at least one processor is configured to average numerator of the metric across the multiple received data symbols, to average denominator of the metric across the multiple received data symbols, and to determine the data-to-pilot ratio based on the averaged numerator and the averaged denominator.

21. The apparatus of claim 17, wherein the at least one processor is configured to receive pilot via multiple receive antennas, to receive data via the multiple receive antennas, to combine the received data across the multiple receive antennas to obtain combined data, to estimate signal-to-noise-and-interference ratio (SINR) based on the received pilot from the multiple receive antennas, and to estimate the data-to-pilot ratio based on the combined data and the estimated SINR.

22. The apparatus of claim 21, wherein the combined data comprises multiple combined data symbols, and wherein the data-to-pilot ratio is estimated based on a metric

I z I 2 - SINR,

SINR;

where i is an index for the combined data symbols, Z1 represents z-th combined data symbol, and SINR1 represents estimated SINR for the z-th combined data symbol.

23. An apparatus for wireless communication, comprising: means for estimating channel gain and noise variance based on received pilot; and means for estimating a data-to-pilot ratio based on received data and the estimated channel gain and noise variance.

24. The apparatus of claim 23, wherein the means for estimating the data-to-pilot ratio comprises means for determining a first quantity based on the received data and the estimated noise variance, means for determining a second quantity based on the estimated channel gain, and means for estimating the data-to-pilot ratio based on the first and second quantities.

25. The apparatus of claim 23, wherein the received data comprises multiple received data symbols, and wherein the data-to-pilot ratio is estimated based on a metric

y, \ 2 - ^ where i is an index for the received data symbols, yr represents z-th received data symbol, H1 represents estimated channel gain for the z-th received data symbol, and σ] represents estimated noise variance for the z-th received data symbol.

26. The apparatus of claim 25, wherein the means for estimating the data-to-pilot ratio comprises means for averaging numerator of the metric across the multiple received data symbols, means for averaging denominator of the metric across the multiple received data symbols, and means for determining the data-to-pilot ratio based on the averaged numerator and the averaged denominator.

27. The apparatus of claim 23, further comprising: means for receiving pilot via multiple receive antennas; means for receiving data via the multiple receive antennas; means for combining the received data across the multiple receive antennas to obtain combined data; and means for estimating signal-to-noise-and-interference ratio (SINR) based on the received pilot from the multiple receive antennas, wherein the means for estimating the data-to-pilot ratio comprises means for estimating the data-to-pilot ratio based on the combined data and the estimated SINR.

28. The apparatus of claim 27, wherein the combined data comprises multiple combined data symbols, and wherein the data-to-pilot ratio is estimated based on a metric

- SINR,

SINR

where i is an index for the combined data symbols, Z1 represents z-th combined data symbol, and SINR1 represents estimated SINR for the z-th combined data symbol.

29. A computer program product, comprising: a computer-readable medium comprising: code for causing at least one computer to estimate channel gain and noise variance based on received pilot; and code for causing the at least one computer to estimate a data-to-pilot ratio based on received data and the estimated channel gain and noise variance.

30. A method of transmitting data and pilot for wireless communication, comprising: sending pilot at a predetermined power level to multiple terminals; and sending data to each of the multiple terminals at a power level determined based on a data-to-pilot ratio for the terminal, each terminal estimating the data-to-pilot ratio for the terminal based on the data sent to the terminal and the pilot sent to the multiple terminal.

31. The method of claim 30, further comprising: determining the predetermined power level of the pilot based on power levels of the data sent to the multiple terminals and target data-to-pilot ratios for the multiple terminals.

32. The method of claim 30, further comprising: varying the power level of the data sent to each terminal without informing the terminal of changes to the power level.

33. The method of claim 30 , further comprising : receiving channel quantity indicator (CQI) information from each of the multiple terminals; and determining the power level of the data sent to each terminal based on the CQI information received from the terminal.

34. The method of claim 30, wherein the data sent to each terminal comprises control data, and wherein the pilot and control data are sent on a shared control channel to the multiple terminals.

35. An apparatus for wireless communication, comprising: at least one processor configured to send pilot at a predetermined power level to multiple terminals, and to send data to each of the multiple terminals at a power level determined based on a data-to-pilot ratio for the terminal, each terminal estimating the data-to-pilot ratio for the terminal based on the data sent to the terminal and the pilot sent to the multiple terminal.

36. The apparatus of claim 35, wherein the at least one processor is configured to vary the power level of the data sent to each terminal without informing the terminal of changes to the power level.