Processing method and device for performing space-time decoding on MIMO signal

1. A processing method for performing space-time decoding on MIMO signals comprising:

step 1, performing QR decomposition on a channel matrix H with a matrix size of N r ×N t in a MIMO system and performing an initialization operation, wherein N t is the number of transmitting antennas and N r is the number of receiving antennas;

step 2, enumerating candidate constellation points of transmitting signals at each level of transmitting antennas according to an input parameter M=[M 1 , M 2 , . . . , M N t ], a receiving signal y and a result of QR decomposition of the channel matrix H, wherein M is the number of the enumerated candidate constellation points at each level, the receiving signal y=Hs+n, wherein H is the channel matrix with the matrix size of N r ×N t , s is a transmitting signal with a matrix size of N t ×1, n is white gaussian noise with a matrix size of N r ×1;

step 3, calculating an increment of a Euclid distance due to addition of selection of candidate constellation points at present level according to the obtained candidate constellation points; and

step 4, deciding and outputting space-time decoding according to the sum of the calculated increments of Euclid distances of candidate constellation points at each level.

2. The method according to claim 1 , wherein the step 1 comprises:

step 11, performing QR decomposition on the channel matrix H according to formula 1:

H=Q×R   formula 1,

wherein Q represents an orthogonal matrix after the QR decomposition of the channel matrix H and R represents an upper triangular matrix after the QR decomposition of the channel matrix H;

step 12, multiplying the receiving signal y by a Hermitian transpose of the matrix Q after the QR decomposition of the channel matrix H: ŷ=Q H y, wherein Q H represents a Hermitian conjugate of the matrix Q; and

step 13, setting i=N t .

3. The method according to claim 2 , wherein the transmitting signals are modulated by using a mode of multi-level Quadrature Amplitude Modulation (M-QAM).

4. The method according to claim 2 , wherein the step 2 comprises:

step 21, calculating directly restored data of transmitting signals of the i(1, 2, . . . , N t ) th transmitting antenna according to formula 2:

ξ

i

=

y

^

i

-

∑

j

=

i

+

1

N

t

⁢

R

ij

⁢

s

j

R

ii

,

formula

⁢

⁢

2

wherein ŷ i represents a i th element of a vector ŷ, R ij represents data in the i th low and the j th column of the matrix R after the QR decomposition of the channel matrix H, and s j represents detected transmitting signals of the j th transmitting antenna;

step 22, calculating a distance of the restored data from the nearest candidate constellation point according to formula 3:

d=ξ i −Q (ξ i )  formula 3,

wherein Q(ξ i ) represents performing a hard decision for ζ i ;

step 23, calculating an auxiliary variable φ according to formula 4:

φ=| ( d )|>| ( d )|  formula 4,

wherein ( ) represents taking real part operation, and ( ) represents taking imaginary part operation;

step 24, calculating the number Rn i =ceil(sqrt(M i )) of points of required real parts and the number In i =ceil(sqrt (M i )) of points of required imaginary parts;

step 25, calculating the number Rn i of the nearest points from (ξ i ) in a set set and calculating the number In i of the nearest points from (ξ i ) in a set set, wherein set is a set of values of real parts of candidate constellation points and set is a set of values of imaginary parts of candidate constellation points; and

step 25, calculating candidate constellation points p i (1, 2, . . . , M i ) at each level of transmitting antennas according to a principle of gradual increase of Euclid distances and according to Rn i , In i and the auxiliary variable φ.

5. The method according to claim 4 , wherein the transmitting signals are modulated by using a mode of multi-level Quadrature Amplitude Modulation (M-QAM).

6. The method according to claim 4 , wherein the step 3 comprises:

step 31, setting s i to be respectively equal to each point in the candidate constellation points p i (1, 2, . . . , M i ) detected by the i th transmitting antenna, and calculating Euclid distances under M i different paths according to formula 5:

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(

s

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=

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;

formula

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5

and

step 32, determining whether i equals 1, and if yes, performing the step 4; if not, setting i=i−1 and performing the step 21.

7. The method according to claim 6 , wherein the step 4 comprises:

step 41, determining whether a hard decision mode or a soft decision mode is used, performing step 42 if the hard decision mode is determined to be used and performing step 43 if the soft decision mode is determined to be used;

step 42, selecting directly a path that minimizes

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i

=

1

N

t

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(

s

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as a decision output; and

step 43, performing log-likelihood ratio calculation according to constellation points corresponding to the first A paths that minimizes

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=

1

N

t

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

e

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(

s

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2

and a value of

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1

N

t

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(

s

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2

,

and using a result of calculation as a decision output.

8. The method according to claim 6 , wherein the transmitting signals are modulated by using a mode of multi-level Quadrature Amplitude Modulation (M-QAM).

9. The method according to claim 1 , wherein the step 4 comprises:

step 41, determining whether a hard decision mode or a soft decision mode is used, performing step 42 if the hard decision mode is determined to be used and performing step 43 if the soft decision mode is determined to be used;

step 42, selecting directly a path that minimizes

∑

i

=

1

N

t

⁢



e

⁡

(

s

i

)



2

as a decision output; and

step 43, performing log-likelihood ratio calculation according to constellation points corresponding to the first A paths that minimizes

∑

i

=

1

N

t

⁢



e

⁡

(

s

i

)



2

and a value of

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=

1

N

t

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e

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(

s

i

)



2

,

and using a result of calculation as a decision output.

10. The method according to claim 9 , wherein the transmitting signals are modulated by using a mode of multi-level Quadrature Amplitude Modulation (M-QAM).

11. The method according to claim 1 , wherein the transmitting signals are modulated by using a mode of multi-level Quadrature Amplitude Modulation (M-QAM).

12. A processing apparatus for performing space-time decoding on MIMO signals comprising:

a QR decomposition module configured to perform QR decomposition on a channel matrix H with a matrix size of N r ×N t in a MIMO system and perform an initialization operation, wherein N t is the number of transmitting antennas and N r is the number of receiving antennas;

a candidate constellation point calculation module configured to enumerate candidate constellation points of transmitting signals at each level of transmitting antennas according to an input parameter M=[M 1 , M 2 , . . . , M N t ], a receiving signal y and a result of the QR decomposition of the channel matrix H, wherein M is the number of the enumerated candidate constellation points at each level, the receiving signal y=Hs+n, wherein H is the channel matrix with the matrix size of N r ×N t , s is a transmitting signal with a matrix size of N t ×1, n is white gaussian noise with a matrix size of N r ×1;

a Euclid increment calculation module configured to calculate an increment of a Euclid distance due to addition of selection of a candidate constellation point at present level according to the obtained candidate constellation points; and

an output module configured to decide and output space-time decoding according to the sum of the calculated increments of Euclid distances of candidate constellation points at each level.

13. The apparatus according to claim 12 , wherein the QR decomposition module is configured to:

perform QR decomposition on the channel matrix H according to formula 6:

H=Q×R   formula 6,

wherein Q represents an orthogonal matrix after the QR decomposition of the channel matrix H and R represents an upper triangular matrix after the QR decomposition of the channel matrix H;

multiply the receiving signal y by a Hermitian transpose of the matrix Q after the QR decomposition of the channel matrix H: ŷ=Q H y, wherein Q H represents a Hermitian conjugate of the matrix Q; and

set i=N t .

14. The apparatus according to claim 13 , wherein the transmitting signals are modulated by using a mode of multi-level Quadrature Amplitude Modulation (M-QAM).

15. The apparatus according to claim 13 , wherein the candidate constellation point calculation module is configured to:

calculate directly restored data of transmitting signals of the i(1, 2, . . . , N t ) th transmitting antenna according to formula 7:

ξ

i

=

y

^

i

-

∑

j

=

i

+

1

N

t

⁢

R

ij

⁢

s

j

R

ii

,

formula

⁢

⁢

7

wherein ŷ i represents a i th element of a vector ŷ, R ij represents data in the i th low and the j th column of the matrix R after the QR decomposition of the channel matrix H, and s j represents detected transmitting signals of the j th transmitting antenna;

calculate a distance of the restored data from the nearest candidate constellation point according to formula 8:

d=ξ i −Q (ξ i )  formula 8,

wherein Q(ξ i ) represents performing a hard decision for ζ i ;

calculate an auxiliary variable φ according to formula 9:

φ=| ( d )|>| ( d )|  formula 9,

wherein ( ) represents taking real part operation, and ( ) represents taking imaginary part operation;

calculate the number Rn i =ceil(sqrt(M i )) of points of required real parts and the number In i =ceil(sqrt(M i )) of points of required imaginary parts;

calculate the number Rn i of the nearest points from (ξ i ) in a set set and calculating the number In i of the nearest points from (ξ i ) in a set set, wherein set is a set of values of real parts of candidate constellation points and set is a set of values of imaginary parts of candidate constellation points; and

calculate candidate constellation points p i (1, 2, . . . , M i ) at each level of transmitting antennas according to a principle of gradual increase of Euclid distances and according to Rn i , In i and the auxiliary variable φ.

16. The apparatus according to claim 15 , wherein the transmitting signals are modulated by using a mode of multi-level Quadrature Amplitude Modulation (M-QAM).

17. The apparatus according to claim 15 , wherein the Euclid increment calculation module is configured to:

set s i to be respectively equal to each point in the candidate constellation points p i (1, 2, . . . , M i ) detected by the i th transmitting antenna, and calculate Euclid distances under M i different paths according to formula 10:

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⁡

(

s

i

)



2

=



y

^

i

-

∑

j

=

i

N

t

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R

ij

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s

j

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2

;

formula

⁢

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10

and

determine whether i equals 1, and if yes, invoke the output module; if not, set i=i−1 and invoke the candidate constellation point calculation module.

18. The apparatus according to claim 17 , wherein the output module comprises:

a determining sub-module configured to determine whether a hard decision mode or a soft decision mode is used, invoke a hard decision outputting sub-module if the hard decision mode is determined to be used and invoke a log-likelihood ratio calculation sub-module if the soft decision mode is determined to be used;

the hard decision outputting sub-module configured to select directly a path that minimizes

∑

i

=

1

N

t

⁢



e

⁡

(

s

i

)



2

as a decision output; and

the log-likelihood ratio calculation sub-module configured to perform a log-likelihood ratio calculation according to constellation points corresponding to the first A paths that minimizes

∑

i

=

1

N

t

⁢



e

⁡

(

s

i

)



2

and a value of

∑

i

=

1

N

t

⁢



e

⁡

(

s

i

)



2

,

and use a result of calculation as a decision output.

19. The apparatus according to claim 17 , wherein the transmitting signals are modulated by using a mode of multi-level Quadrature Amplitude Modulation (M-QAM).

20. The apparatus according to claim 12 , wherein the transmitting signals are modulated by using a mode of multi-level Quadrature Amplitude Modulation (M-QAM).