Channel acquistion using orthogonal time frequency space modulated pilot signal

1. A wireless communication method for recovering information bits from a received signal, implemented by a wireless communication receiver, comprising:

receiving a wireless signal comprising a data signal portion and a pilot signal portion wherein the pilot signal portion includes multiple pilot signals multiplexed together in an orthogonal time frequency space (OTFS) domain;

performing two-dimensional channel estimation in a time-frequency domain based on a minimum mean square error (MMSE) optimization criterion; and

recovering information bits using a channel estimate obtained from the two-dimensional channel estimation;

wherein the performing the two-dimensional channel estimation includes:

identifying a subset of the pilot signal portion from which to obtain a preliminary channel estimate in the time-frequency domain;

estimating, using samples of the wireless signal received within a two-dimensional observation window, the preliminary channel estimate; and

obtaining the channel estimate by interpolating and/or predicting the preliminary channel estimate.

2. The method of claim 1 , wherein the preliminary channel estimate is estimated using samples from all time domain sampling instances.

3. The method of claim 1 , wherein the preliminary channel estimate is estimated using samples from a subset corresponding to less than all time domain sampling instances, depending on the preliminary channel estimate.

4. The method of claim 1 , wherein estimating operation includes calculating a finite impulse response (FIR) Wiener filter estimate using the subset of the pilot signal portion.

5. A wireless communication apparatus comprising a memory and a processor, wherein the memory stores instructions that, when executed, cause the processor to implement a wireless communication reception method, the instructions comprising:

instructions for receiving a wireless signal comprising a data signal portion and a pilot signal portion wherein the pilot signal portion includes multiple pilot signals multiplexed together in an orthogonal time frequency space (OTFS) domain;

instructions for performing two-dimensional channel estimation in a time-frequency domain based on a minimum mean square error (MMSE) optimization criterion; and

performing information bit recovery using a channel estimate obtained from the two-dimensional channel estimation;

wherein the instructions for estimating the two-dimensional channel estimation include:

instructions for identifying a subset of the pilot signal portion from which to obtain a preliminary channel estimate in the time-frequency domain;

instructions for estimating, using samples of the wireless signal received within a two-dimensional observation window, the preliminary channel estimate; and

instructions for obtaining the channel estimate by interpolating and/or predicting the preliminary channel estimate.

6. The apparatus of claim 5 , wherein the instructions for estimating the preliminary channel estimate include instructions for estimating the preliminary channel using samples from all time domain sampling instances.

7. The apparatus of claim 5 , wherein the preliminary channel estimate is estimated using samples from a subset corresponding to less than all time domain sampling instances, depending on the preliminary channel estimate.

8. The apparatus of claim 5 , wherein estimating operation includes calculating a finite impulse response (FIR) Wiener filter estimate using the subset of the pilot signal portion.

9. A wireless communication method for recovering information bits from a received signal, implemented by a wireless communication receiver, comprising:

receiving, over a communication channel a wireless signal comprising a data signal portion and a pilot signal portion wherein the pilot signal portion includes multiple pilot signals multiplexed together in an orthogonal time frequency space (OTFS) domain;

transforming the received wireless signal into a delay-time domain signal;

applying a delay-time domain mask to separate out each of the multiple pilot signals' contribution to the delay-time domain signal into corresponding separate received pilot signal contributions;

estimating, using the separate received pilot signal contributions, the communication channel estimates at delay-time domain positions of the multiple pilot signals; and

interpolating the communication channel estimates to obtain an entire communication channel estimate.

10. The method of claim 9 , wherein the transforming is performed using a Fourier transform.

11. The method of claim 9 , wherein the delay-time domain mask comprises a square mask.

12. The method of claim 9 , wherein the interpolating is performed across time for multiple values of delays in the delay-time domain.

13. The method of claim 9 , wherein the estimating includes estimating the communication channel estimates using a spline approximation technique in which a piecewise continuous polynomial is computed based on the separate received pilot signal contributions.

14. The method of claim 9 , wherein the estimating includes estimating the communication channel estimates using a minimum mean square error criterion based on the received pilot signal contributions.

15. The method of claim 9 , wherein the estimating includes estimating the communication channel estimates by applying a bandwidth constraint by zeroing high frequency coefficients resulting from applying a frequency transform to the separate received pilot signal contributions.

16. The method of claim 9 , wherein the interpolating includes interpolating using a polynomial approximation.

17. The method of claim 9 , further including: recovering information bits using a channel estimate obtained from the two-dimensional channel estimation.

18. The method of claim 17 , wherein the recovering the information bits includes performing a symbol demodulation to recover information bits.

19. The method of claim 9 , further including windowing the communication channel estimate in a time-frequency domain.

20. The method of claim 19 , wherein the windowing includes windowing using a squared cosine window.

21. The method of claim 9 , further including:

applying an inverse Fourier transform across the delay dimension a channel estimate in a time-frequency domain.

22. The method of claim 21 , wherein the applying the inverse Fourier transform includes applying the inverse Fourier transform only on a masked portion or only on a portion corresponding to a delay span around the received pilot signals.

23. A wireless communication apparatus, comprising:

a memory for storing data and instructions;

a processor for executing the instructions and implementing a data reception method comprising:

receiving, over a communication channel a wireless signal comprising a data signal portion and a pilot signal portion wherein the pilot signal portion includes multiple pilot signals multiplexed together in an orthogonal time frequency space (OTFS) domain;

transforming the received wireless signal into a delay-time domain signal;

applying a delay-time domain mask to separate out each of the multiple pilot signal's contribution to the delay-time domain signal into corresponding separate received pilot signal contributions;

estimating, using the separate received pilot signal contributions, the communication channel estimates at delay-time domain positions of the multiple pilot signals; and

interpolating the communication channel estimates to obtain an entire communication channel estimate.

24. The apparatus of claim 23 , wherein the transforming is performed using a Fourier transform.

25. The apparatus of claim 23 , wherein the delay-time domain mask comprises a square mask.

26. The apparatus of claim 23 , wherein the interpolating is performed across time for multiple values of delays in the delay-time domain.

27. The apparatus of claim 23 , wherein the estimating includes estimating the communication channel estimates using a spline approximation technique in which a piecewise continuous polynomial is computed based on the separate received pilot signal contributions.

28. The apparatus of claim 23 , wherein the estimating includes estimating the communication channel estimates using a minimum mean square error criterion based on the received pilot signal contributions.

29. The apparatus of claim 23 , wherein the estimating includes estimating the communication channel estimates by applying a bandwidth constraint by zeroing high frequency coefficients resulting from applying a frequency transform to the separate received pilot signal contributions.

30. The apparatus of claim 23 , wherein the interpolating includes interpolating using a polynomial approximation.

31. The apparatus of claim 23 , further including: recovering information bits using a channel estimate obtained from the two-dimensional channel estimation.

32. The apparatus of claim 31 , wherein the recovering the information bits includes performing a symbol demodulation to recover information bits.

33. A wireless communication method for recovering information bits from a received signal, implemented by a wireless communication receiver, comprising:

receiving, over a communication channel, a wireless signal comprising a data signal portion and a pilot signal portion wherein the pilot signal portion includes multiple pilot signals multiplexed together in an orthogonal time frequency space (OTFS) domain;

transforming the received wireless signal into a delay-Doppler domain signal by applying a two-dimensional symplectic Fourier transform;

applying a delay-Doppler domain mask to separate out each of the multiple pilot signal's contribution to the time-frequency domain signal into corresponding separate received pilot signal contributions;

estimating, using the separate received pilot signal contributions, the communication channel estimates at delay-Doppler domain positions of the multiple pilot signals; and

interpolating the communication channel estimates to obtain an entire communication channel estimate.

34. The method of claim 33 , wherein the delay-Doppler domain mask comprises a square mask.

35. The method of claim 34 , wherein the interpolating is performed across time for multiple values of delays in the delay-Doppler domain.

36. The method of claim 33 , wherein the estimating includes estimating the communication channel estimates using a minimum mean square error criterion based on the received pilot signal contributions.

37. The method of claim 33 , further including: recovering information bits using a channel estimate obtained from the two-dimensional channel estimation.

38. The method of claim 33 , further including:

isolating the multiple pilot signals back into time-frequency domain by using a two-dimensional symplectic Fourier transform by zeroing delay and Doppler values outside the entire channel estimate.

39. The method of claim 33 , further including:

transforming the multiple pilot signals back into time-frequency domain by using a two-dimensional symplectic Fourier transform and wherein estimating the communication channel estimates includes estimating the communication channel estimates in time-frequency domain using an optimization algorithm.

40. The method of claim 39 , wherein the optimization algorithm includes one of a minimum mean square error algorithm or a spline optimization algorithm.

41. The method of claim 39 , further including windowing the communication channel estimate in a time-frequency domain.

42. The method of claim 41 , wherein the windowing includes windowing using a squared cosine window.