Orthogonal time frequency space modulation system
View Patent ↗A system and method for orthogonal time frequency space communication and waveform generation. The method includes receiving a plurality of information symbols and creating a plurality of modulation symbols by using each of the plurality information symbols to modulate one of a plurality of two-dimensional basis functions on a time-frequency plane Each of the plurality of two-dimensional basis functions is uniquely associated with one of the plurality of information symbols. The method further includes generating a transmit waveform comprised of a plurality of pulse waveforms. Each of the plurality of pulse waveforms corresponds to a combination of one of the plurality of modulation symbols and one of a plurality of time-translated and frequency-modulated versions of a fundamental transmit pulse.
1. A method for waveform transmission, the method comprising:
receiving a plurality of information symbols:
creating a matrix of modulation parameters by using each of the plurality information symbols to modulate one of a plurality of two-dimensional basis functions on a time-frequency plane wherein each of the plurality of two-dimensional basis functions is uniquely associated with one of the plurality of information symbols;
generating a transmit waveform comprised of a plurality of pulse waveforms, each of the plurality of pulse waveforms corresponding to a combination of one of the modulation parameters and one of a plurality of time-translated and frequency-modulated versions of a fundamental transmit pulse; and
transmitting the transmit waveform over a communication channel.
2. The method of claim 1 wherein each of the plurality of time-translated and frequency-modulated versions of the fundamental transmit pulse is associated with a time translation by one of N multiples of T and a frequency modulation by one of the M multiples of Δƒ, where N and M are constants, N×M is equivalent to a number of the modulation parameters, T is a time sampling period, and Δƒ is a frequency sampling period.
3. The method of claim 2 wherein the fundamental transmit pulse has the property of being orthogonal to translations by a multiple of time T and modulation by a multiple of Δƒ.
4. The method of claim 2 wherein the transmit waveform is of a total duration of NT seconds and a total bandwidth of Mă Hz.
5. The method of claim 1 further including generating the plurality of pulse waveforms by modulating a set of OFDM subcarriers.
6. The method of claim 2 further including arranging the plurality of information symbols on a two-dimensional grid having a first dimension of N elements and a second dimension of M elements.
7. A communication device, comprising:
a wireless transmitter;
a processor; and
a memory including program code executable by the processor, the program code including:
code for causing the processor to receive a plurality of information symbols;
code for causing the processor to create a matrix of modulation parameters by using each of the plurality information symbols to modulate one of a plurality of two-dimensional basis functions on a time-frequency plane wherein each of the plurality of two-dimensional basis functions is uniquely associated with one of the plurality of information symbols;
code for causing the processor to generate a transmit waveform comprised of a plurality of pulse waveforms, each of the plurality of pulse waveforms corresponding to a combination of one of the modulation parameters and one of a plurality of time-translated and frequency-modulated versions of a fundamental transmit pulse; and
code for causing the processor to provide the transmit waveform to the wireless transmitter for transmission by the wireless transmitter.
8. The communication device of claim 7 wherein each of the plurality of time-translated and frequency-modulated versions of the fundamental transmit pulse is associated with a time translation by one of N multiples of T and a frequency modulation by one of the M multiples of Δƒ, where N and M are constants, N×M is equivalent to a number of the modulation parameters, T is a time sampling period, and Δƒ is a frequency sampling period.
9. The communication device of claim 7 wherein the fundamental transmit pulse has the property of being orthogonal to translations by a multiple of time T and modulation by a multiple of Δƒ.
10. The communication device of claim 8 wherein the transmit waveform is of a total duration of NT seconds and a total bandwidth of Mă Hz.
11. The communication device of claim 7 , wherein the program code further includes code for generating the plurality of pulse waveforms by modulating a set of OFDM subcarriers.
12. The communication device of claim 7 , wherein the program code further includes code for arranging the plurality of information symbols on a two-dimensional grid having a first dimension of N elements and a second dimension of M elements.
13. A method, comprising:
receiving, at a communication receiver, one or more modulated waveforms;
matched filtering samples of the one or more modulated waveforms with respect to a receive pulse to produce estimated time-frequency modulation symbols wherein each of the estimated time-frequency modulation symbols corresponds to modulation of one of a plurality of orthogonal two-dimensional basis functions by one of a plurality of information symbols; and
projecting the estimates of the time-frequency modulation symbols on the plurality of orthogonal two-dimensional basis functions in order to obtain estimates of the plurality of information.
14. The method of claim 13 further including performing windowing and periodization operations with respect to the estimated time-frequency modulation symbols.
15. The method of claim 13 wherein the projecting includes performing a symplectic Fourier transform operation with respect to a periodic sequence comprised of the estimates of the time-frequency modulation symbols.
16. A communication device, comprising:
a wireless receiver configured to receive one or more modulated waveforms;
a processor; and
a memory including program code executable by the processor, the program code including:
code for causing the processor to receive, from the wireless receiver, samples of one or more modulated waveforms,
code for causing the processor to matched filter samples of the one or more modulated waveforms with respect to a receive pulse to produce estimated time-frequency modulation symbols wherein each of the estimated time-frequency modulation symbols corresponds to modulation of one of a plurality of orthogonal two-dimensional basis functions by one of a plurality of information symbols; and
code for causing the processor to project the estimated time-frequency modulation symbols on the plurality of orthogonal two-dimensional basis functions in order to obtain estimates of the plurality of information symbols.
17. The communication device of claim 16 wherein the program code further includes code for performing windowing and periodization operations with respect to the estimated time-frequency modulation symbols.
18. The communication device of claim 16 wherein the code for causing the processor to project further includes code for causing the processor to perform a symplectic Fourier transform operation with respect to a periodic sequence comprised of the estimated time-frequency modulation symbols.
19. The method of claim 13 wherein the projecting is in accordance with equation:
x
^
[
l
,
k
]
=
∑
m
=
0
M
-
1
∑
n
=
0
N
-
1
X
^
(
n
,
m
)
b
k
,
l
*
(
n
,
m
)
where {circumflex over (x)}[l, k] represents the estimates of the plurality of information symbols, where {circumflex over (X)}(n, m) represent the estimated time-frequency modulation symbols, and where
b
k
,
l
*
(
n
,
m
)
=
e
-
j
2
π
(
lm
L
-
kn
K
)
corresponds to the plurality of orthogonal two-dimensional basis functions.
20. The communication device of claim 16 wherein the code for causing the processor to project is in accordance with equation:
x
^
[
l
,
k
]
=
∑
m
=
0
M
-
1
∑
n
=
0
N
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1
X
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(
n
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)
b
k
,
l
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(
n
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m
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where {circumflex over (x)}[l, k] represents the estimates of the plurality of information symbols, where {circumflex over (X)}(n, m) represent the estimated time-frequency modulation symbols, and where
b
k
,
l
*
(
n
,
m
)
=
e
-
j
2
π
(
lm
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-
kn
K
)
corresponds to the plurality of orthogonal two-dimensional basis functions.
21. The method of claim 1 wherein the plurality of modulation symbols are created in accordance with the equation:
X
[
n
,
m
]
=
1
MN
W
tr
[
n
,
m
]
∑
k
=
0
N
-
1
∑
l
=
0
M
-
1
x
[
l
,
k
]
b
k
,
l
[
n
,
m
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b
k
,
l
[
n
,
m
]
=
e
j
2
π
(
ml
M
-
nk
N
)
where X[n, m], n=0, . . . , N−1, m=0, . . . , M−1 represent the plurality of modulation symbols, x[k, l] represents the plurality of information symbols, W tr [n, m] represents a transmit windowing function, and b k,l [n, m] represents the plurality of two-dimensional basis functions.