Methods and devices for interference variance estimation and interference cancellation

1. An interference variance estimation method, comprising:

receiving a composite sample comprising a sample of a first Orthogonal Frequency Division Multiplexing (OFDM) transmission scheme interfered by an out-of-band interference of a second OFDM transmission scheme different from the first OFDM transmission scheme, the first OFDM transmission scheme comprising a plurality of resource elements arranged in a symbol-subcarrier grid;

determining, for each of the plurality of resource elements, a power estimate of the out-of-band interference; and

filtering the plurality of power estimates over a plurality of subcarriers corresponding to a same symbol of the symbol-subcarrier grid to obtain the interference variance, the filtering being performed by using a filter length corresponding to correlation properties of samples of the second OFDM transmission scheme,

wherein weights of the filtering are based on a correlation property of the plurality of power estimates with respect to the plurality of subcarriers.

2. The method of claim 1 ,

wherein the first OFDM transmission scheme comprises a cellular transmission scheme; and

wherein the second OFDM transmission scheme comprises a wireless network transmission scheme.

3. The method of claim 1 , comprising:

time-averaging the interference variance of a particular subcarrier over a plurality of symbols of the symbol-subcarrier grid to obtain an estimate of the interference variance for the particular subcarrier.

4. The method of claim 3 , comprising:

time-averaging the interference variance based on a sliding window.

5. The method of claim 1 , comprising:

filtering the plurality of power estimates over a plurality of adjacent sets of subcarriers of the symbol-subcarrier grid.

6. The method of claim 1 , comprising:

determining the weights of the filtering based on an Minimum Mean Square Error (MMSE) algorithm.

7. The method of claim 1 , comprising:

determining a hypothesis of the sample of the first OFDM transmission scheme based on a distance between the composite sample and a set of modulation symbols of the first OFDM transmission scheme.

8. The method of claim 7 , comprising:

determining for each of the resource elements the power estimate of the out-of-band interference based on the received composite sample, the hypothesis of the sample of the first OFDM transmission scheme and an estimated channel.

9. The method of claim 1 ,

wherein a correlation coefficient of power estimates corresponding to a predetermined subcarrier distance of 50 indicates that the power estimates are totally correlated.

10. The method of claim 1 ,

wherein a distribution of the out-of-band interference on each subcarrier of the first OFDM transmission scheme is Gaussian with zero mean.

11. An interference cancellation method, comprising:

receiving a composite sample comprising a sample of a first Orthogonal Frequency Division Multiplexing (OFDM) transmission scheme interfered by an out-of-band interference of a second OFDM transmission scheme different from the first OFDM transmission scheme, the first OFDM transmission scheme comprising a plurality of resource elements arranged in a symbol-subcarrier grid, wherein a plurality of subcarriers are partitioned into a plurality of non-data bearing subcarriers and a plurality of data bearing subcarriers;

determining a first estimate of the out-of-band interference according to the plurality of non-data bearing subcarriers using an interference variance that is associated with the out-of-band interference of the second OFDM transmission scheme, the interference variance being estimated with respect to the plurality of subcarriers;

determining a second estimate of the out-of-band interference according to the plurality of data bearing subcarriers based on the first estimate; and

cancelling the out-of-band interference based on the composite sample and the second estimate.

12. The method of claim 1 ,

wherein the first OFDM transmission scheme comprises a transmission scheme of a Long Term Evolution (LTE) network; and

wherein the second OFDM transmission scheme comprises a transmission scheme of a WiFi network.

13. The method of claim 11 ,

wherein the first OFDM transmission scheme comprises a cellular transmission scheme; and

wherein the second OFDM transmission scheme comprises a wireless network transmission scheme.

14. The method of claim 11 , comprising:

determining the first estimate of the out-of-band interference by using a Minimum Mean Square Error (MMSE)-based estimator.

15. The method of claim 11 , comprising:

determining the second estimate of the out-of-band interference by using a correlation property between the plurality of non-data bearing subcarriers and the plurality of data bearing subcarriers.

16. The method of claim 11 , comprising:

determining the second estimate of the out-of-band interference based on a scaling of the first estimate of the out-of-band interference.

17. The method of claim 16 , comprising

scaling the first estimate of the out-of-band interference with a variance of the out-of-band interference at the plurality of data bearing subcarriers.

18. The method of claim 17 , comprising:

estimating the variance of the out-of-band interference at the plurality of data bearing subcarriers.

19. The method of claim 18 ,

wherein the estimating the variance of the out-of-band interference comprises:

determining for each of the plurality of resource elements a corresponding power estimate of the out-of-band interference;

estimating the variance at a resource element based on filtering the plurality of power estimates over subcarriers of the symbol-subcarrier grid which of the plurality of subcarriers correspond to a same symbol of the symbol-subcarrier grid; and

adjusting weights of the filtering based on a correlation property of the plurality of power estimates with respect to the subcarriers.

20. The method of claim 12 , comprising:

cancelling the out-of-band interference based on a subtraction of the second estimate of the out-of-band interference from the composite sample.

21. The method of claim 11 ,

wherein the first OFDM transmission scheme comprises a transmission scheme of a Long Term Evolution (LTE) network; and

wherein the second OFDM transmission scheme comprises a transmission scheme of a WiFi network.

22. The method of claim 11 , wherein the interference variance is estimated by filtering a plurality of power estimates associated with the plurality of subcarriers, the filtering being performed by using a filter length corresponding to correlation properties of samples of the second OFDM transmission scheme.

23. An interference variance estimator, comprising:

a receiving port configured to receive a composite sample comprising a sample of a first Orthogonal Frequency Division Multiplexing (OFDM) transmission scheme interfered by an out-of-band interference of a second OFDM transmission scheme different from the first OFDM transmission scheme, the first OFDM transmission scheme comprising a plurality of resource elements arranged in a symbol-subcarrier grid;

a first circuit configured to determine, for each of the resource elements, a power estimate of the out-of-band interference; and

a second circuit configured to filter a plurality of power estimates over subcarriers corresponding to a same symbol of the symbol-subcarrier grid to obtain the interference variance, the filtering being performed by using a filter length corresponding to correlation properties of samples of the second OFDM transmission scheme, and

wherein weights of the filtering are based on a correlation property of the plurality of power estimates with respect to the subcarriers.

24. The interference variance estimator of claim 23 ,

wherein the second circuit comprises a Minimum Mean Square Error (MMSE) filter configured to filter the power estimates.

25. The interference variance estimator of claim 23 ,

wherein the first OFDM transmission scheme comprises a transmission scheme of a Long Term Evolution (LTE) network; and

wherein the second OFDM transmission scheme comprises a transmission scheme of a WiFi network.

26. An interference canceller, comprising:

a receiving port configured to receive a composite sample comprising a sample of a first OFDM transmission scheme interfered by an out-of-band interference of a second OFDM transmission scheme different from the first OFDM transmission scheme, the first OFDM transmission scheme comprising a plurality of resource elements arranged in a symbol-subcarrier grid, wherein the subcarriers are partitioned into a plurality of non-data bearing subcarriers and a plurality of data bearing subcarriers;

a first circuit configured to determine a first estimate of the out-of-band interference according to the plurality of non-data bearing subcarriers using an interference variance that is associated with the out-of-band interference of the second OFDM transmission scheme, the interference variance being estimated with respect to the plurality of subcarriers;

a second circuit configured to determine a second estimate of the out-of-band interference according to the plurality of data bearing subcarriers based on the first estimate; and

a third circuit configured to cancel the out-of-band interference based on the composite sample and the second estimate.

27. The interference canceller of claim 26 , wherein the first circuit comprises an Minimum Mean Square Error (MMSE) filter configured to determine the first estimate.

28. The interference canceller of claim 26 , wherein the second circuit is configured to determine the second estimate based on a scaling of the first estimate with a variance of the out-of-band interference at the plurality of data bearing subcarriers.

29. The interference canceller of claim 26 ,

wherein the first OFDM transmission scheme comprises a transmission scheme of a Long Term Evolution (LTE) network; and

wherein the second OFDM transmission scheme comprises a transmission scheme of a WiFi network.