Orthogonal time frequency space communication system compatible with OFDM

• US 10,411,843 B2
• Filed: 07/12/2016
• Issued: 09/10/2019
• Est. Priority Date: 06/25/2012
• Status: Active Grant

• Current Assignee: Cohere Technologies Inc
• Original Assignee: Cohere Technologies Inc
• Inventors: Rakib, Shlomo Selim, Hadani, Ronny
• Primary Examiner(s): Yu, Lihong
• Application Number:
  US15/208,545
• Publication Number:
  US 20170012749A1
• Time in Patent Office: 1,155 Days
• Field of Search: 375260
• CPC Class Codes: H04L 27/2639 Modulators using other transforms, e.g. discrete cosine transforms, Orthogonal Time Frequency and Space [OTFS] or hermetic transforms
• CPC Class Codes: H04L 27/2697 in combination with other modulation techniques
• CPC Class Codes: H04L 5/0007 the frequencies being orthogonal, e.g. OFDM(A), DMT

Abstract

A system and method for orthogonal time frequency space communication and waveform generation compatible with OFDM. The method includes receiving a plurality of information symbols and encoding an N×M array containing the plurality of information symbols into a two-dimensional array of modulation symbols by spreading each of the plurality of information symbols with respect to both time and frequency. The two-dimensional array of modulation symbols is then transmitted along with one or more OFDM symbols using a plurality of narrowband subcarriers.

Claims

1. A method of transmitting data over a communication channel, the method comprising:

receiving a plurality of information symbols;

encoding an N×

M array containing the plurality of information symbols into a two-dimensional array of orthogonal time frequency space (OTFS) modulation symbols by spreading the plurality of information symbols across both time and frequency by a corresponding plurality of two-dimensional basis functions wherein the corresponding plurality of two-dimensional basis functions are mutually orthogonal with respect to both time and frequency and wherein the array of OTFS modulation symbols is arranged in a time frequency frame along with one or more orthogonal frequency-division multiple access (OFDM) symbols and wherein N and M are integers;

transmitting the two-dimensional array of OTFS modulation symbols using M narrowband subcarriers; and

transmitting the one or more OFDM symbols using at least one OFDM subcarrier.

2. The method of claim 1 wherein the at least one OFDM subcarrier is included within the M narrrowband subcarriers.

3. The method of claim 1 wherein the encoding includes:

transforming the N×

M array into an array of filtered OFDM symbols using at least one Fourier transform and a filtering process;

transforming the array of filtered OFDM symbols into an array of OTFS symbols using at least one two-dimensional Fourier transform wherein the array of OTFS symbols corresponds to the two-dimensional array of modulation symbols.

4. The method of claim 1 wherein the encoding includes combining an inverse symplectic transform with a windowing operation.

5. The method of claim 1 further including selecting N and M based upon at least one of a latency and a rate associated with transmission of the data over the communication channel.

6. The method of claim 1 further including selecting N and M based upon at least one of an anticipated Doppler shift and anticipated multi-path delay associated with transmission of the data over the communication channel.

7. A method of transmitting data over a communication channel, the method comprising:

receiving a plurality of information symbols;

encoding an N×

M array containing the plurality of information symbols into a two-dimensional array of orthogonal time frequency space (OTFS) modulation symbols by using each of the plurality of information symbols frequency to modulate one of by a corresponding plurality of two-dimensional basis functions wherein the array of OTFS modulation symbols is arranged in a time frequency frame along with one or more orthogonal frequency-division multiple access (OFDM) symbols, wherein N and M are integers, and wherein the encoding is performed in accordance with the following relationship;

8. A communication device, comprising:

a wireless transmitter;

a processor; and

a non-transitory memory including program code executable by the processor, the program code including code for causing the processor to;

receive a plurality of information symbols;

encode an N×

M array containing the plurality of information symbols into a two-dimensional array of orthogonal time frequency space (OTFS) modulation symbols by spreading the plurality of information symbols across both time and frequency by a corresponding plurality of two-dimensional basis functions wherein the corresponding plurality of two-dimensional basis functions are mutually orthogonal with respect to both time and frequency and wherein the array of OTFS modulation symbols is arranged in a time frequency frame along with one or more orthogonal frequency-division multiple access (OFDM) symbols and wherein N and M are integers;

transmit the two-dimensional array of OTFS modulation symbols using M narrowband subcarriers; and

transmit the one or more OFDM symbols using at least one OFDM subcarrier.

9. The communication device of claim 8 wherein the at least one OFDM subcarrier is included within the M narrrowband subcarriers.

10. The communication device of claim 8 wherein the code for causing the processor to encode includes code for causing the processor to:

transform the N×

M array into an array of filtered OFDM symbols using at least one Fourier transform and a filtering process;

transform the array of filtered OFDM symbols into an array of OTFS symbols using at least one two-dimensional Fourier transform.

11. The communication device of claim 8 wherein the code for causing the processor to encode includes code for causing the processor to combine an inverse symplectic transform with a windowing operation.