Tomlinson-Harashima precoding in an OTFS communication system

• US 10,063,295 B2
• Filed: 04/03/2017
• Issued: 08/28/2018
• Est. Priority Date: 04/01/2016
• Status: Active Grant

• Current Assignee: Cohere Technologies Inc
• Original Assignee: Cohere Technologies Inc
• Inventors: Delfeld, Jim, Rakib, Shlomo Selim
• Primary Examiner(s): Huang, David S
• Application Number:
  US15/478,174
• Publication Number:
  US 20170288710A1
• Time in Patent Office: 512 Days
• CPC Class Codes: H04B 7/0413 MIMO systems
• CPC Class Codes: H04B 7/0456 Selection of precoding matrices or codebooks, e.g. using matrices antenna weighting
• CPC Class Codes: H04L 25/0222 Estimation of channel variability, e.g. coherence bandwidth, coherence time, fading frequency
• CPC Class Codes: H04L 25/03343 Arrangements at the transmitter end
• CPC Class Codes: H04L 25/4975 Correlative coding using Tomlinson precoding, Harashima precoding, Trellis precoding or GPRS
• CPC Class Codes: H04L 5/0048 Allocation of pilot signals, i.e. of signals known to the receiver

Abstract

A method for signal transmission using precoded symbol information involves estimating a two-dimensional model of a communication channel in a delay-Doppler domain. A perturbation vector is determined in a delay-time domain wherein the delay-time domain is related to the delay-Doppler domain by an FFT operation. User symbols are modified based upon the perturbation vector so as to produce perturbed user symbols. A set of Tomlinson-Harashima precoders corresponding to a set of fixed times in the delay-time domain may then be determined using a delay-time model of the communication channel. Precoded user symbols are generated by applying the Tomlinson-Harashima precoders to the perturbed user symbols. A modulated signal is then generated based upon the precoded user symbols and provided for transmission over the communication channel.

Claims

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

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;

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;

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

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

generating precoded user symbols by applying the Tomlinson-Harashima precoders to the perturbed user symbols; and

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

2. The method of claim 1 wherein the applying includes using FFT operations to apply the Tomlinson-Harashima precoders to the perturbed user symbols.

3. The method of claim 1 wherein the determining a set of Tomlinson-Harashima precoders includes performing a decomposition of the delay-time model of the communication channel.

4. The method of claim 3 in which the decomposition comprises an LQD decomposition where L is a lower triangular matrix, D is a diagonal matrix, and Q is a unitary matrix.

5. The method of claim 1 wherein the estimating the two-dimensional model of the communication channel includes:

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

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

6. A communication apparatus, comprising:

a plurality of antennas;

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 Tomlinson-Harashima precoders corresponding to a set of fixed times in the delay-time domain;

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

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

7. The communication apparatus of claim 6 wherein the processor is further configured to use FFT operations to apply the Tomlinson-Harashima precoders to the perturbed user symbols.

8. The communication apparatus of claim 6 wherein the processor is further configured to determine the set of Tomlinson-Harashima precoders by performing a decomposition of the delay-time model of the communication channel.

9. The communication apparatus of claim 8 where the decomposition comprises an LQD decomposition where L is a lower triangular matrix, D is a diagonal matrix, and Q is a unitary matrix.

10. The communication apparatus of claim 6 wherein the processor, as part of estimating the two-dimensional model of the communication channel, is further configured 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.