Modulation and equalization in an orthonormal time-frequency shifting communications system
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.
1. A receiver processing unit, comprising:
a demodulator operative to receive and demodulate an orthonormal time-frequency shifting (OTFS) signal and to provide a demodulated OTFS signal;
a cyclic deconvolution module configured to deconvolve the demodulated OTFS signal utilizing one or more equalization parameters; and
an OTFS equalizer disposed to generate, based upon the demodulated OTFS signal, an equalized OTFS signal and the one or more equalization parameters.
2. The receiver processing unit of claim 1 wherein the OTFS equalizer is further configured to send the one or more equalization parameters to a transmitter from which the OTFS signal was previously transmitted.
3. The receiver processing unit of claim 1 wherein the OTFS signal results from transforming an original data frame by performing a two-dimensional cyclic convolution using a spreading kernel.
4. The receiver processing unit of claim 3 wherein the cyclic deconvolution module is configured to perform a two-dimensional cyclic deconvolution.
5. The receiver processing unit of claim 1 wherein the OTFS signal results from transforming an original data frame to form a transformed data matrix wherein each element of the transformed data matrix includes a contribution from each of the elements of the original data frame.
6. The receiver processing unit of claim 5 wherein the original data frame has a first dimension of N elements and a second dimension of M elements, where N and M are integers greater than one.
7. The receiver processing unit of claim 1 wherein the one or more equalization parameters comprise a time deconvolution parameter indicative of one or more echo locations in a communication channel through which the OTFS signal is transmitted.
8. The receiver processing unit of claim 1 wherein the one or more equalization parameters comprise a frequency deconvolution parameter indicative of one or more frequency shifts in a communication channel through which the OTFS signal is transmitted.
9. The receiver processing unit of claim 1 wherein the one or more equalization parameters comprise time and frequency deconvolution parameters indicative of one or more echo locations and frequency shifts in a communication channel through which the OTFS signal is transmitted.
10. The receiver processing unit of claim 1 wherein the OTFS signal includes a plurality of cyclically time shifted and cyclically frequency shifted waveforms.
11. The receiver processing unit of claim 1 wherein the OTFS equalizer includes a time-frequency-space decision feedback equalizer.
12. The receiver processing unit of claim 11 wherein the time-frequency-space decision feedback equalizer includes a time-frequency-space feedforward finite impulse response (FIR) filter and a time-frequency-space feedback FIR filter.
13. A method, comprising:
demodulating an orthonormal time-frequency shifting (OTFS) signal and providing a demodulated OTFS signal;
deconvolving the demodulated OTFS signal utilizing one or more equalization parameters; and
generating, based upon the demodulated OTFS signal, an equalized OTFS signal and the one or more equalization parameters.
14. The method of claim 13 further including sending the one or more equalization parameters to a transmitter from which the OTFS signal was previously transmitted.
15. The method of claim 13 wherein the OTFS signal results from transforming an original data frame by performing a two-dimensional cyclic convolution using a spreading kernel.
16. The method of claim 15 wherein the deconvolving includes performing a two-dimensional cyclic deconvolution.
17. The method of claim 13 wherein the OTFS signal results from transforming an original data frame to form a transformed data matrix wherein each element of the transformed data matrix includes a contribution from each of the elements of the original data frame.
18. The method of claim 17 wherein the original data frame has a first dimension of N elements and a second dimension of M elements, where N and M are integers greater than one.
19. The method of claim 13 wherein the one or more equalization parameters comprise time and frequency deconvolution parameters indicative of one or more echo locations and frequency shifts in a communication channel through which the OTFS signal is transmitted.