Tomlinson-harashima precoding in an OTFS communication system

1. A device for signal transmission using precoded symbol information, the device comprising:

a processor configured to:

estimate a two-dimensional model of a communication channel in a delay-Doppler domain wherein the two-dimensional model of the communication channel is a function of time delay and frequency shift;

determine a perturbation vector in a delay-time domain wherein the delay-time domain is related to the delay-Doppler domain by an FFT operation;

modify user symbols based upon the perturbation vector so as to produce perturbed user symbols;

determine, using a delay-time model of the communication channel, a set of precoders corresponding to a set of fixed times in the delay-time domain;

generate precoded user symbols by applying the precoders to the perturbed user symbols; and

provide, based upon the precoded user symbols, a modulated signal for transmission over the communication channel.

2. The device of claim 1 , wherein the processor is further configured, as part of applying the precoders, to:

use FFT operations to apply the precoders to the perturbed user symbols.

3. The device of claim 1 , wherein the processor is further configured, as part of determining the set of precoders, to:

perform a decomposition of the delay-time model of the communication channel.

4. The device of claim 3 , wherein the decomposition comprises an LQD decomposition, and wherein L is a lower triangular matrix, D is a diagonal matrix, and Q is a unitary matrix.

5. The device of claim 1 , wherein the processor is further configured, as part of estimating the two-dimensional model of the communication channel, to:

receive at least a first pilot signal wherein the first pilot signal occupies a first predetermined coordinate position in a time-frequency plane; and

determine a first time shift of the first pilot signal and a first frequency shift of the first pilot signal.

6. The device of claim 1 , wherein the modulated signal is modulated using an orthogonal time frequency space (OTFS) or an orthogonal frequency division multiplexing (OFDM) modulation scheme.

7. The device of claim 1 , wherein the processor is further configured to:

receive, over the communication channel, a feedback signal,

wherein the estimating the two-dimensional model of the communication channel is based on the feedback signal.

8. The device of claim 1 , wherein the set of precoders comprise a set of Tomlinson-Harashima precoders.

9. A non-transitory computer-readable storage medium having instructions stored thereupon for wireless communication, comprising:

instructions for estimating a two-dimensional model of a communication channel in a delay-Doppler domain wherein the two-dimensional model of the communication channel is a function of time delay and frequency shift;

instructions for determining a perturbation vector in a delay-time domain wherein the delay-time domain is related to the delay-Doppler domain by an FFT operation;

instructions for modifying user symbols based upon the perturbation vector so as to produce perturbed user symbols;

instructions for determining using a delay-time model of the communication channel, a set of precoders corresponding to a set of fixed times in the delay-time domain;

instructions for generating precoded user symbols by applying the precoders to the perturbed user symbols; and

instructions for providing based upon the precoded user symbols, a modulated signal to the plurality of antennas for transmission over the communication channel.

10. The storage medium of claim 9 , further comprising:

instructions for using FFT operations to apply the precoders to the perturbed user symbols.

11. The storage medium of claim 9 , further comprising:

instructions for determining the set of precoders by performing a decomposition of the delay-time model of the communication channel.

12. The storage medium of claim 11 , wherein the decomposition comprises an LQD decomposition, and wherein L is a lower triangular matrix, D is a diagonal matrix, and Q is a unitary matrix.

13. The storage medium of claim 9 , further comprising, as part of the instructions for estimating the two-dimensional model of the communication channel:

instructions for receiving at least a first pilot signal wherein the first pilot signal occupies a first predetermined coordinate position in a time-frequency plane, and

instructions for determining a first time shift of the first pilot signal and a first frequency shift of the first pilot signal.

14. The storage medium of claim 9 , wherein the modulated signal is modulated using an orthogonal time frequency space (OTFS) or an orthogonal frequency division multiplexing (OFDM) modulation scheme.

15. The storage medium of claim 9 , further comprising:

instructions for receiving, over the communication channel, a feedback signal,

wherein the estimating the two-dimensional model of the communication channel is based on the feedback signal.

16. The storage medium of claim 9 , wherein the set of precoders comprise a set of Tomlinson-Harashima precoders.