Method and system for utilizing space-time and space-frequency codes for multi-input multi-output frequency selective fading channels
View Patent ↗A communication system for transmitting encoded signals over a communication channel is disclosed. The system includes a transmitter, which has a source that outputs a message signal. The transmitter also includes an encoder that generates a code word in response to the message signal. The code word has a construction that defines a plurality of paths associated with an intersymbol interference (ISI) environment of the communication channel, wherein the code word achieves a diversity based upon the number of transmit antennas and the number of ISI paths. Further, the transmitter includes a modulator that modulates the code word for transmission over the communication channel, and multiple antennas that transmit the modulated code word over the communication channel. The system encompasses a receiver that receives the transmitted code word via a number of receive antennas.
1. A method comprising:
demodulating a signal containing a code word, the code word having a construction that defines a plurality of paths associated with an intersymbol interference (ISI) environment of a communication channel, the code word achieving a diversity based upon the number of transmit antennas and the number of ISI paths,
wherein the code word is decoded to output a message signal.
2. The method according to claim 1 , wherein the code word satisfies a baseband rank criterion such that rank(f ISI (c)−f ISI (e)) is maximized over all pairs of distinct code words c, e∈C, C being an L t ×l linear space-time code, L t representing the number of transmit antennas, wherein
f
(
c
)
ISI
=
[
f
(
c
)
0
_
…
0
_
0
_
f
(
c
)
…
0
_
⋮
⋮
⋰
⋮
0
_
0
_
…
f
(
c
)
]
,
0 being an L t ×1 all zero vector.
3. The method according to claim 2 , wherein rank(f ISI (c)−f ISI (e))=L t L ISI for all pairs of distinct code words c, e∈C, and L ISI represents the number of ISI paths.
4. The method according to claim 2 , wherein the construction further defines an ISI code word matrix as follows:
c
ISI
=
[
c
0
_
…
0
0
c
…
0
⋮
⋮
⋰
⋮
0
0
…
c
]
,
wherein f(c ISI )≠f(c) ISI , the diversity being based upon f(c ISI )−f(e ISI )=f(c) ISI −f(e) ISI .
5. The method according to claim 4 , wherein the construction further defines an ISI channel binary rank criterion such that C has an underlying binary code C of length N=L t l operating in the ISI environment and l≧L t L ISI , L ISI representing the number of ISI paths.
6. The method according to claim 5 , wherein, for every non-zero code word c corresponding to C ISI of full rank L t L ISI over a binary field F, the diversity of the space-time code C is L t L ISI .
7. The method according to claim 1 , wherein the construction further defines M 1 , M 2 , . . . , M L t as binary matrices of dimension k×l,l≧k, and C is an L t ×l linear space-time code of dimension k and includes code word matrices defined as follows:
c
=
[
x
_
M
1
x
_
M
2
⋮
x
_
M
L
t
]
,
wherein x denotes an arbitrary k-tuple of information bits associated with the message signal, and L t <l, L t representing the number of transmit antennas.
8. The method according to claim 7 , wherein the construction further defines M n,m =└O L t ×(m−1) M n O L t ×(L ISI +1−m) ┘, O L t ×(m− being an L t ×(m−1) all zero matrix, for BPSK transmission, the diversity is L t L ISI , if and only if M 1,1 , M 2,1 , . . . , M L t L ISI , ∀α 1 ,α 2 , . . . ,α L t ∈F: M=α 1 M 1,1 ⊕α 2 M 2,1 ⊕. . . ⊕a L t L ISI M L t L ISI is of full rank k unless α 1 =. . . ,α L t L ISI =0, F being a binary field, the code word being drawn from
c
ISI
=
[
x
_
M
1
,
1
x
_
M
1
,
2
⋮
x
_
M
L
t
,
L
ISI
]
.
9. The method according to claim 1 , wherein the received signal is modulated using at least one of BPSK (binary phase-shift keying) modulation and QPSK (quadrature phase-shift keying) modulation.
10. The method according to claim 1 , wherein the decoder utilizes a maximum likelihood decoding algorithm to decode the received signal.
11. The method according to claim 1 , further comprising: storing channel state information of the communication channel, wherein the code word is decoded based upon the channel state information.
12. A device comprising:
demodulating a signal containing a code word, the code word having a construction that defines a plurality of paths associated with an intersymbol interference (ISI) environment of a communication channel, the code word achieving a diversity based upon the number of transmit antennas and the number of ISI paths,
wherein the code word is decoded to output a message signal.
13. The device according to claim 12 , wherein the code word satisfies a baseband rank criterion such that rank(f ISI (c)f ISI (e)) is maximized over all pairs of distinct code words c, e∈C, C being an L 1 × linear space-time code, L t , representing the number of transmit antennas, wherein
f
(
c
)
ISI
=
[
f
(
c
)
0
_
…
0
_
0
_
f
(
c
)
…
0
_
⋮
⋮
⋰
⋮
0
_
0
_
…
f
(
c
)
]
,
0 being an L t ×1 all zero vector.
14. The device according to claim 13 , wherein
rank(f ISI (c)−f ISI (e))=L t L ISI for all pairs of distinct code words c, e∈C, and L ISI represents the number of ISI paths.
15. The device according to claim 13 , wherein the construction further defines an ISI code word matrix as follows:
c
ISI
=
[
c
0
_
…
0
0
c
…
0
⋮
⋮
⋰
⋮
0
0
…
c
]
,
wherein f(c ISI )≠f(c) ISI , the diversity being based upon f(c ISI )−f(e ISI )=f(c) ISI −f(e) ISI .
16. The device according to claim 15 , wherein the construction further defines an ISI channel binary rank criterion such that C has an underlying binary code C of length N=L t l operating in the ISI environment and l≧L t L ISI , L ISI representing the number of ISI paths.
17. The device according to claim 16 , wherein, for every non-zero code word c corresponding to c ISI of full rank L t L ISI over a binary field F, the diversity of the space-time code C is L t L ISI .
18. The device according to claim 12 , wherein the construction further defines M 1 , M 2 , . . . , M L t as biny matrices of dimension k×l,l≧k, and C is an L t ×l linear space-time code of dimension k and includes code word matrices defined as follows:
c
=
[
x
_
M
1
x
_
M
2
⋮
x
_
M
L
t
]
,
wherein x denotes an arbitrary k-tuple of information bits associated with the message signal, and L t <l, L t , representing the number of transmit antennas.
19. The device according to claim 18 , wherein the construction further defines M n,m =└O L t ×(m−1) M n O L t ×(L ISI =l−m)┘, O L t ×(m−l) being an L t ×(m −1) all zero matrix, for BPSK transmission, the diversity is L t L ISI , if and only if M 1,l ,M 2,1 , . . . ,M L t L ISI , ∀α 1 ,α 2 , . . . ,α L t ∈ F: M=α l M l,l ⊕α 2 M 2,l ⊕. . . ⊕α L t L ISI is of full rank k unless α 1 =. . . α L t L ISI =0, F being a binary field, the code word being drawn from
c
ISI
=
[
x
_
M
1
,
1
x
_
M
1
,
2
⋮
x
_
M
L
t
,
L
ISI
]
.
20. The device according to claim 12 , wherein the received signal is modulated using at least one of BPSK (binary phase-shift keying) modulation and QPSK (quadrature phase-shift keying) modulation.
21. The device according to claim 12 , wherein the decoder utilizes a maximum likelihood decoding algorithm to decode the received signal.
22. The device according to claim 12 , wherein channel state information of the communication channel is stored and used to decode the code word.
23. A method comprising:
receiving a code word having a construction that defines a plurality of paths associated with an intersymbol interference (IDI) environment of a communication channel, the code word achieving a diversity based upon the number of transmit antennas and the number of ISI paths, wherein the code word is decoded to output a message signal.
24. A system comprising:
means for receiving a code word having a construction that defines a plurality of paths associated with an intersymbol interference (ISI) environment of a communication channel, the code word achieving a diversity based upon the number of transmit antennas and the number of ISI paths, wherein the code word is decoded to output a message signal.