Orthogonal time frequency space communication system compatible with OFDM
A system and method for orthogonal time frequency space communication and waveform generation. 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 using M mutually orthogonal waveforms included within M frequency sub-bands.
1. A method of transmitting data over a communication channel, the method comprising:
multiplexing transmissions for a plurality of users into an N×M array containing a plurality of information symbols;
encoding the 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; and
transmitting the two-dimensional array of modulation symbols using M mutually orthogonal waveforms included within M frequency sub-bands,
wherein the multiplexing is performed in one of a delay-Doppler domain, a time-frequency domain, or a code-spreading domain.
2. The method of claim 1 , wherein, in case the multiplexing is performed in the delay-Doppler domain, the multiplexing includes assigning different sets of orthogonal time frequency space (OTFS) basis functions to the plurality of users.
3. The method of claim 1 , wherein, in case the multiplexing is performed in the delay-Doppler domain, the multiplexing includes assigning different sets of information symbols or resource blocks to the plurality of users.
4. The method of claim 1 , wherein, in case the multiplexing is performed in the time-frequency domain, the multiplexing includes assigning a different subframe of the N×M array to each of the plurality of users.
5. The method of claim 1 , wherein, in case the multiplexing is performed in the time-frequency domain, the multiplexing includes assigning the plurality of information symbols to the plurality of users by interleaving in time, frequency, or both time and frequency.
6. The method of claim 1 , wherein, in case the multiplexing is performed in the code-spreading domain, the multiplexing includes assigning a different two-dimensional window function to each user.
7. The method of claim 1 , wherein the encoding is performed in accordance with the following relationship:
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
]
b
k
,
l
[
n
,
m
]
=
e
j
2
π
m
l
M
-
nk
N
wherein x[l,k],k=0, . . . , N−1,l=0, M −1 represents the N×M array containing the plurality of information symbols, X[n,m], n=0, . . . , N−1,m=0, . . . , M −1 represents the two-dimensional array of modulation symbols, W tr [n,m] is a windowing function, and b k,l [m,n] represents a set of basis functions.
8. A wireless communication apparatus, comprising a processor configured to:
multiplex transmissions for a plurality of users into an N×M array containing a plurality of information symbols;
encode the 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; and
transmitting the two-dimensional array of modulation symbols using M mutually orthogonal waveforms included within M frequency sub-bands,
wherein multiplexing the transmissions is performed in one of a delay-Doppler domain, a time-frequency domain, or a code-spreading domain.
9. The apparatus of claim 8 , wherein, in case the multiplexing is performed in the delay-Doppler domain, the multiplexing includes assigning different sets of orthogonal time frequency space (OTFS) basis functions to the plurality of users.
10. The apparatus of claim 8 , wherein, in case the multiplexing is performed in the delay-Doppler domain, the multiplexing includes assigning different sets of information symbols or resource blocks to the plurality of users.
11. The apparatus of claim 8 , wherein, in case the multiplexing is performed in the time-frequency domain, the multiplexing includes assigning a different subframe of the N×M array to each of the plurality of users.
12. The apparatus of claim 8 , wherein, in case the multiplexing is performed in the time-frequency domain, the multiplexing includes assigning the plurality of information symbols to the plurality of users by interleaving in time, frequency, or both time and frequency.
13. The apparatus of claim 8 , wherein, in case the multiplexing is performed in the time-frequency domain, the multiplexing includes assigning a different two-dimensional window function to each user.
14. The apparatus of claim 8 , wherein the encoding is performed in accordance with the following relationship:
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
]
b
k
,
l
[
n
,
m
]
=
e
j
2
π
m
l
M
-
nk
N
wherein x[l,k],k=0, . . . , N−1,l=0, . . . , M−1 represents the N×M array containing the plurality of information symbols, X[n,m],n=0, . . . , N−1,m=0, . . . , M−1 represents the two-dimensional array of modulation symbols, W tr [n,m] is a windowing function, and b k,l [m,n] represents a set of basis functions.
15. The apparatus of claim 8 , wherein, in case the multiplexing is performed in the code-spreading domain, the multiplexing includes assigning a different two-dimensional window function to each user.