Modulation and equalization in an orthonormal time-frequency shifting communications system

• US 9,130,638 B2
• Filed: 06/25/2013
• Issued: 09/08/2015
• Est. Priority Date: 05/26/2011
• Status: Active Grant

• Current Assignee: Cohere Technologies Inc
• Original Assignee: Cohere Technologies Inc
• Inventors: Hadani, Ronny, Rakib, Salim Shlomo
• Primary Examiner(s): NEFF, MICHAEL R
• Application Number:
  US13/927,091
• Publication Number:
  US 20140169441A1
• Time in Patent Office: 805 Days
• Field of Search: 375/233, 375/232, 375/230, 375/229
• US Class Current: 1/1
• CPC Class Codes: H04B 1/1027 assessing signal quality or detecting noise/interference for the received signal
• CPC Class Codes: H04B 7/005 Control of transmission; Equalising
• CPC Class Codes: H04L 23/02 adapted for orthogonal signalling
• CPC Class Codes: H04L 25/03834 using pulse shaping
• CPC Class Codes: H04L 27/01 Equalisers baseband equalizers at the transmitter end H04L25/03343; in analogue transmission systems H04B3/04, H04B7/005
• CPC Class Codes: H04L 27/2634 Inverse fast Fourier transform [IFFT] or inverse discrete Fourier transform [IDFT] modulators in combination with other circuits for modulation
• CPC Class Codes: H04L 27/26524 Fast Fourier transform [FFT] or discrete Fourier transform [DFT] demodulators in combination with other circuits for demodulation
• CPC Class Codes: H04L 27/2655 Synchronisation arrangements
• CPC Class Codes: H04L 27/2697 in combination with other modulation techniques
• CPC Class Codes: H04L 5/0016 Time-frequency-code
• CPC Class Codes: H04L 5/0044 allocation of payload

Abstract

A method of receiving data including receiving, on one or more carrier waveforms, signals representing a plurality of data elements of an original data frame wherein each of the data elements are represented by cyclically time shifted and cyclically frequency shifted versions of a known set of waveforms. The method further includes generating, based upon the signals, a received data frame and generating an equalized data frame by performing an equalization operation using elements of the received data frame, the equalization operation correcting for distortion introduced into the signals during propagation of the carrier waveforms through a channel.

Claims

1. A method, comprising:

receiving, at a signal receiver, a received orthonormal time-frequency shifting (OTFS) signal wherein the received OTFS signal includes a plurality of echo reflections of a transmitted OTFS signal comprised of cyclically time shifted and cyclically frequency shifted waveforms, each of the plurality of echo reflections comprising at least one of a time-shifted signal component and a frequency-shifted signal component;

evaluating the cyclically time shifted and cyclically frequency shifted waveforms in order to detect the at least one of the time-shifted signal component and the frequency-shifted signal component of ones of the plurality of echo reflections; and

generating, based upon the evaluating, corrective information useful in correcting for effects of the plurality of echo reflections.

2. The method of claim 1 further including sending the corrective information to a transmitter from which the transmitted OTFS signal was previously transmitted.

3. The method of claim 1 further using the corrective information to equalize the OTFS signal by shifting ones of the plurality of echo reflections relative to a primary received signal component.

4. The method of claim 1 wherein the evaluating includes using pattern matching to evaluate patterns associated with the cyclically time shifted and cyclically frequency shifted waveforms.

5. The method of claim 1 wherein the transmitted OTFS signal is generated by transforming a data frame including a plurality of data elements into a transformed data matrix having a plurality of transformed data elements wherein ones of the plurality of transformed data elements are based upon multiple ones of the plurality of data elements and wherein the data frame has a first dimension of at least N data elements and a second dimension of at least N data elements, wherein N is greater than one.

6. The method of claim 1 wherein the transmitted OTFS signal is generated by transforming a data frame including a plurality of data elements into a two-dimensionally spread data matrix and tiling each column of the two-dimensionally spread data matrix as a function of one of time and frequency.

7. A receiver, comprising:

a processor;

a memory including program code executable by the processor, the program code including;

code for receiving, at a signal receiver, a received orthonormal time-frequency shifting (OTFS) signal wherein the received OTFS signal includes a plurality of echo reflections of a transmitted OTFS signal comprised of cyclically time shifted and cyclically frequency shifted waveforms, each of the plurality of echo reflections comprising at least one of a time-shifted signal component and a frequency-shifted signal component;

code for evaluating the cyclically time shifted and cyclically frequency shifted waveforms in order to detecting the at least one of the time-shifted signal component and the frequency-shifted signal component of ones of the plurality of echo reflections; and

code for generating, based upon the evaluating, corrective information useful in correcting for effects of the plurality of echo reflections.

8. The receiver of claim 7 wherein the program code further includes code for facilitating sending of the corrective information to a transmitter from which the transmitted OTFS signal was previously transmitted.

9. The receiver of claim 7 wherein the program code further includes code for using the corrective information to equalize the OTFS signal by shifting ones of the plurality of echo reflections relative to a primary received signal component.

10. A non-transitory computer readable medium including program instructions for execution by a processor in a signal receiver, the program instructions comprising instructions for causing the processor to:

receive, at a signal receiver, a received orthonormal time-frequency shifting (OTFS) signal wherein the received OTFS signal includes a primary signal component and at least one echo reflection of a transmitted OTFS signal comprised of cyclically time shifted and cyclically frequency shifted waveforms, the echo reflection comprising at least one of a time-shifted signal component and a frequency-shifted signal component;

evaluate the cyclically time shifted and cyclically frequency shifted waveforms in order to detect at least one of an extent of a time shift of the time-shifted signal component relative to the primary signal component and an extent of a frequency shift of the frequency-shifted signal component relative to the primary signal component; and

generate, based upon the at least one of the extent of the time shift and the extent of the frequency shift, corrective information useful in correcting for effects of the at least one echo reflection.

11. The non-transitory computer readable medium of claim 10 wherein the program instructions further include instructions for facilitating sending the corrective information to a transmitter from which the OTFS signal was previously transmitted.

12. The non-transitory computer readable medium of claim 10 wherein the program instructions further include instructions for using the corrective information to equalize the OTFS signal by shifting the time-shifted signal component and the frequency-shifted signal component relative to a primary received signal component.

13. A method, comprising:

receiving, at a signal receiver, a composite signal including a plurality of echo reflections of a transmitted signal wherein the transmitted signal is comprised of cyclically time-shifted and cyclically frequency-shifted waveforms;

evaluating the cyclically time shifted and cyclically frequency shifted waveforms of the plurality of echo reflections in order to detect at least one of a time-shifted signal component and a frequency-shifted signal component of ones of the plurality of echo reflections; and

generating, based upon the evaluating, corrective information useful in correcting for effects of the plurality of echo reflections.

14. The method of claim 13 further including sending the corrective information to a transmitter from which the composite signal was previously transmitted.

15. The method of claim 13 further using the corrective information to equalize the composite signal.

16. A method of receiving data, comprising:

receiving, on one or more carrier waveforms having propagated through a communication media, a primary signal and echo reflection signals representing a plurality of data elements of an original data frame wherein each of the data elements are represented by cyclically time shifted and cyclically frequency shifted versions of a known set of waveforms;

generating, based upon the primary signal and the echo reflection signals, a received data frame;

evaluating ones of the cyclically time shifted and cyclically frequency shifted versions of the known set of waveforms to determine time and frequency equalization parameters useful in correcting for effects of the echo reflection signals; and

generating an equalized data frame by performing an equalization operation using elements of the received data frame, the equalization operation correcting for distortion introduced by at least the echo reflection signals.

17. The method of claim 16 wherein the received data frame is of dimension N×

N, where N is greater than one.