Determining hybrid ARQ indicators

1. A user equipment (UE)-implemented method for Hybrid Automatic Repeat Request (HARQ) indicator detection, the method comprising:

separating received Physical HARQ Indicator Channel (PHICH) modulation symbols into two data streams: (1) PHICH modulation symbols including interference, and (2) PHICH modulation symbols including substantially no interference;

separately evaluating the PHICH modulation symbols including interference and the PHICH modulation symbols including substantially no interference, wherein separately evaluating the received PHICH modulation symbols comprises:

generating first set of outputs based on both the received PHICH modulation symbols including interference and a predetermined orthogonal cover code for the UE; and

generating second set of outputs based on both the received PHICH modulation symbols including substantially no interference and the predetermined orthogonal cover code for the UE; and

determining a Hybrid ARQ indicator for a UE based upon a combination of the separate evaluations of the PHICH modulation symbols including interference and the PHICH modulation symbols including substantially no interference, wherein determining the Hybrid ARQ indicator for the UE is based on the first set of outputs, the second set of outputs, and comparing with a reduced set of hypothesis values.

2. The method of claim 1 , where in the first set and the second set of outputs formed from the received PHICH modulation symbols over all the receive antennas and the OCC and transformed form of OCC.

3. The method of claim 1 , wherein the hypothesis values are determined based on the Hybrid ARQ indicators for other UEs simultaneously transmitted over the same radio resources.

4. The method of claim 1 , wherein the comparing comprises;

obtaining a first set of metrics, by measuring the squared Euclidean distance between the first set and corresponding reduced set of hypothesis values for Hybrid ARQ indicator equal to a minus one or a plus one;

obtaining second set of metrics, by measuring the squared Euclidean distance between the second set and corresponding reduced set of hypothesis values for Hybrid ARQ indicator equal to a minus one or a plus one;

scaling the first set of metrics by a first scaled estimate of noise variance;

scaling the second set of metrics by a second scaled estimate of noise variance; and

computing an exponential sum of first and second set of metrics corresponding to Hybrid ARQ indicator equal to a minus one and a plus one.

5. The method of claim 4 , wherein the exponential sum computed in natural logarithm using look-up tables.

6. The method claim 4 , wherein the first and second scaling factors are negative numbers less than zero.

7. The method of claim 4 , wherein the second scaling factor is different from the first scaling.

8. The method of claim 7 , wherein the first and second scaling factors dependent on the noise plus interference power estimated over the PHICH symbols with interference and the PHICH symbols with relatively no interference.

9. The method claim 1 , wherein the reduced set of hypothesis values is based on the predetermined orthogonal cover code and a transformed version of the predetermined orthogonal cover code for the UE.

10. The method of claim 1 , wherein the reduced set of hypothesis values are stored in a pre-computed look up table.

11. The method of claim 1 , wherein each of the reduced set of hypothesis values corresponds to an orthogonal cover code that has a non-zero cross covariance value with the predetermined orthogonal cover code.

12. The method of claim 1 , wherein generating the first outputs is based on the predetermined orthogonal cover code, and generating second outputs is based on a transformed version of the predetermined orthogonal cover code.

13. The method of claim 12 , wherein the transform is based on a Space Frequency Block Coding (SFBC) technique.

14. The method of claim 1 , wherein the interference is from a neighboring cell transmission.

15. The method of claim 1 , wherein the interference is from the CRS transmissions from at least one neighboring cell.

16. A receiver of a communication network, comprising:

one or more processors configured to:

separate received Physical HARQ Indicator Channel (PHICH) modulation symbols into two data streams: (1) PHICH modulation symbols including interference, and (2) PHICH modulation symbols including substantially no interference;

separately evaluate the PHICH modulation symbols including interference and the PHICH modulation symbols including substantially no interference, wherein separately evaluating the received PHICH modulation symbols comprises:

generating first set of outputs based on both the received PHICH modulation symbols including interference and a predetermined orthogonal cover code for the UE; and

generating second set of outputs based on both the received PHICH modulation symbols including substantially no interference and the predetermined orthogonal cover code for the UE; and

determine a Hybrid ARQ indicator for a UE based upon a combination of the separate evaluations of the PHICH modulation symbols including interference and the PHICH modulation symbols including substantially no interference, wherein determining the Hybrid ARQ indicator for the UE is based on the first set of outputs, the second set of outputs, and comparing with a reduced set of hypothesis values.

17. A user equipment (UE)-implemented method of reducing interference arising from Cell-specific Reference Symbols (CRS) transmitted by a macro cell, the method comprising:

determining at a UE which PHICH (Physical HARQ Indicator Channel) modulation symbols are interfered with by a CRS (Cell-specific Reference Symbol) transmission received at the UE;

separately evaluating at the UE (a) the PHICH modulated symbols that are interfered with by the CRS transmission, and (b) the PHICH modulated symbols that are not interfered with by the CRS transmission, wherein separately evaluating the PHICH modulation symbols comprises:

generating first set of outputs based on both the PHICH modulation symbols that are interfered with by the CRS transmission and a predetermined orthogonal cover code for the UE; and

generating second set of outputs based on both the PHICH modulation symbols that are not interfered with by the CRS transmission and the predetermined orthogonal cover code for the UE; and

determine a Hybrid ARQ indicator for a UE based upon a combination of the separate evaluations after scaling them, wherein determining the Hybrid ARQ indicator for the UE is based on the first set of outputs, the second set of outputs, and comparing with a reduced set of hypothesis values.