Tomlinson-Harashima precoding in an OTFS communication system

• US 10,541,734 B2
• Filed: 07/24/2018
• Issued: 01/21/2020
• 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:
  US16/044,414
• Publication Number:
  US 20190036577A1
• Time in Patent Office: 546 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 wireless communication, comprising:

generating, based on a feedback signal, a two-dimensional estimate of a channel, wherein the two-dimensional estimate is in a delay-Doppler domain that comprises a time delay dimension and a frequency shift dimension;

determining, based on the two-dimensional estimate, a set of precoding values and a set of perturbation values;

generating a plurality of perturbed symbols by applying the set of perturbation values to a plurality of user symbols;

generating a plurality of pre-coded symbols by applying the set of precoding values to the plurality of perturbed symbols;

generating, based on the plurality of pre-coded symbols, a pre-coded signal that is modulated using an orthogonal time frequency space (OTFS) or an orthogonal frequency division multiplexing (OFDM) modulation scheme; and

transmitting, over the channel, the pre-coded signal.

2. The method of claim 1, further comprising:

receiving, over the channel, the feedback signal.

3. The method of claim 2, wherein the feedback signal comprises a channel matrix with a full rank or a nearly full rank.

4. The method of claim 1, wherein the determining the set of perturbation values comprises minimizing ∥

h<sup>−

1</sup>(x+v)∥

², wherein h is the two-dimensional estimate, v is the set of perturbation values, and x is the plurality of user symbols.

5. The method of claim 1, wherein the determining the set of perturbation values is based on minimizing an expected interference and noise in the channel.

6. The method of claim 1, wherein the determining the set of perturbation values is performed in a hybrid delay-time domain that is related to the delay-Doppler domain through a Fast Fourier Transform (FFT) taken across the frequency shift dimension.

7. The method of claim 6, wherein the determining the set of precoding values comprises performing a decomposition of two-dimensional estimate of the channel in the hybrid delay-time domain.

8. The method of claim 7, wherein the decomposition comprises an LDQ decomposition, wherein L is a lower triangular matrix, D is a diagonal matrix and Q is a unitary matrix.

9. The method of claim 7, wherein the set of precoding values comprises Tomlinson-Harashima precoding values.

10. A device for wireless communication, comprising:

a processor; and

a memory that comprises instructions stored thereupon, wherein the instructions when executed by the processor configure the processor to;

generate, based on a feedback signal, a two-dimensional estimate of a channel, wherein the two-dimensional estimate is in a delay-Doppler domain that comprises a time delay dimension and a frequency shift dimension;

determine, based on the two-dimensional estimate, a set of precoding values and a set of perturbation values;

generate a plurality of perturbed symbols by applying the set of perturbation values to a plurality of user symbols;

generate a plurality of pre-coded symbols by applying the set of precoding values to the plurality of perturbed symbols;

generate, based on the plurality of pre-coded symbols, a pre-coded signal that is modulated using an orthogonal time frequency space (OTFS) or an orthogonal frequency division multiplexing (OFDM) modulation scheme; and

transmit, over the channel, the pre-coded signal.

11. The device of claim 10, wherein the instructions when executed by the processor further configures the processor to:

receive, over the channel, the feedback signal.

12. The device of claim 11, wherein the feedback signal comprises a channel matrix with a full rank or a nearly full rank.

13. The device of claim 10, wherein the instructions when executed by the processor further configures the processor, as part of determining the set of perturbation values, to minimize ∥

h<sup>−

1</sup>(x+v)∥

², wherein h is the two-dimensional estimate, v is the set of perturbation values, and x is the plurality of user symbols.

14. The device of claim 10, wherein determining the set of perturbation values is based on minimizing an expected interference and noise in the channel.

15. The device of claim 10, wherein determining the set of perturbation values is performed in a hybrid delay-time domain that is related to the delay-Doppler domain through a Fast Fourier Transform (FFT) taken across the frequency shift dimension.

16. The device of claim 15, wherein the instructions when executed by the processor further configures the processor, as part of determining the set of precoding values, to perform a LDQ decomposition of two-dimensional estimate of the channel in the hybrid delay-time domain, wherein L is a lower triangular matrix, D is a diagonal matrix and Q is a unitary matrix.

17. The device of claim 16, wherein the set of precoding values comprises Tomlinson-Harashima precoding values.

18. A non-transitory computer readable program storage medium having code stored thereon, the code, when executed by a processor, causing the processor to implement a method for wireless communication, the method comprising:

generating, based on a feedback signal, a two-dimensional estimate of a channel, wherein the two-dimensional estimate is in a delay-Doppler domain that comprises a time delay dimension and a frequency shift dimension;

determining, based on the two-dimensional estimate, a set of precoding values and a set of perturbation values;

generating a plurality of perturbed symbols by applying the set of perturbation values to a plurality of user symbols;

generating a plurality of pre-coded symbols by applying the set of precoding values to the plurality of perturbed symbols;

generating, based on the plurality of pre-coded symbols, a pre-coded signal that is modulated using an orthogonal time frequency space (OTFS) or an orthogonal frequency division multiplexing (OFDM) modulation scheme; and

transmitting, over the channel, the pre-coded signal.

19. The non-transitory computer readable program storage medium of claim 18, wherein the method further comprises:

receiving, over the channel, the feedback signal that comprises a channel matrix with a full rank or a nearly full rank.

20. The non-transitory computer readable program storage medium of claim 18, wherein the determining the set of perturbation values is performed in a hybrid delay-time domain that is related to the delay-Doppler domain through a Fast Fourier Transform (FFT) taken across the frequency shift dimension.

21. The non-transitory computer readable program storage medium of claim 20, wherein the determining the set of precoding values comprises performing a LDQ decomposition of two-dimensional estimate of the channel in the hybrid delay-time domain, wherein L is a lower triangular matrix, D is a diagonal matrix and Q is a unitary matrix, and wherein the set of precoding values comprises Tomlinson-Harashima precoding values.