Modulation and equalization in an orthonormal time-frequency shifting communications system
View Patent ↗A method for modulating data for transmission within a communication system. The method includes establishing a time-frequency shifting matrix of dimension N×N, wherein N is greater than one. The method further includes combining the time-frequency shifting matrix with a data frame to provide an intermediate data frame. A transformed data matrix is provided by permuting elements of the intermediate data frame. A modulated signal is generated in accordance with elements of the transformed data matrix.
1. A method of receiving data, comprising:
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;
demodulating the signals to form a transformed data frame having a first dimension of at least N elements and a second dimension of at least M elements, where N and M are integers greater than one;
wherein the first dimension corresponds to a frequency shift axis and the second dimension corresponds to a time shift axis;
performing an inverse time-frequency transformation operation with respect to elements of the transformed data frame so as to yield a non-transformed matrix; and
generating, based upon the non-transformed matrix, a recovered data frame comprising an estimate of the original data frame.
2. The method of claim 1 wherein the inverse time-frequency transformation is performed using a decoding matrix, the decoding matrix being a Hermitian matrix of a time-frequency transformation matrix used to transform the original data frame.
3. The method of claim 1 wherein the generating includes performing an inverse permutation operation upon elements of the non-transformed matrix, wherein the inverse-permutation operation effects a shift of the elements of the inverse-transformed matrix along a time shift axis of the non-transformed matrix.
4. The method of claim 1 wherein N is equal to M.
5. The method of claim 1 further including generating an equalized data frame by performing an equalization operation using elements of the transformed data frame, the equalization operation correcting for distortion introduced into the signals during propagation of the carrier waveforms through a channel.
6. The method of claim 1 further including detecting a time-shifted signal component of the signals and a frequency-shifted signal component of the signals and generating, based upon the detecting, corrective information.
7. The method of claim 6 further including sending the corrective information to a transmitter from which the signals were previously transmitted.
8. The method of claim 6 further using the corrective information to equalize elements of the transformed data frame.
9. A data receiver, comprising:
a processor;
a memory including program code executable by the processor, the program code including:
code for facilitating 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;
code for demodulating the signals to form a transformed data frame having a first dimension of at least N elements and a second dimension of at least M elements, where N and M are integers greater than one;
wherein the first dimension corresponds to a frequency shift axis and the second dimension corresponds to a time shift axis;
code for performing an inverse time-frequency transformation operation with respect to elements of the transformed data frame so as to yield a non-transformed matrix; and
code for generating, based upon the non-transformed matrix, a recovered data frame comprising an estimate of the original data frame.
10. The data receiver of claim 9 wherein the inverse time-frequency transformation is performed using a decoding matrix, the decoding matrix being a Hermitian matrix of a time-frequency transformation matrix used to transform the original data frame.
11. The data receiver of claim 9 wherein the code for generating includes code for performing an inverse permutation operation upon elements of the non-transformed matrix, wherein the inverse-permutation operation effects a shift of the elements of the inverse-transformed matrix along a time shift axis of the non-transformed matrix.
12. The data receiver of claim 9 wherein N is equal to M.