Method and apparatus for ordering retransmissions in an NxM MIMO system

1. A method for ordering retransmissions in a Multi-Input Multi-Output (MIMO) system using N×M antennas, the method comprising:

splitting, at a transmitter, a coded data stream into N sub-packets, and transmitting the N sub-packets to a receiver via N transmission antennas;

removing, at the receiver, interferences of the N sub-packets received via M reception antennas, and independently decoding the interference-removed sub packets;

transmitting, at the receiver to the transmitter, one of an acknowledgement (ACK) and a negative acknowledgement (NACK) depending on errors included in the decoded sub-packets; and

upon receipt of the NACK, retransmitting to the receiver, at the transmitter, a sub-packet retransmission based on an Alamouti space-time coding scheme in descending order of signal to noise ratios (SNRs).

2. The method of claim 1 , further comprising canceling interference and decoding by combining, at the receiver, the retransmitted sub-packet with the previous defective sub-packet on a symbol level.

3. The method of claim 1 , wherein the interference removing is achieved by Minimum Mean Square Examination (MMSE) or Zero Forcing (ZF).

4. The method of claim 1 , wherein a signal-to-noise ratio (SNR) criterion of each reception antenna, determined at the receiver at every retransmission, is used for selection of the retransmission ordering.

5. The method of claim 4 , wherein a highest SNR of each reception antenna maximizes a determinant that derives a channel matrix after each retransmission.

6. The method of claim 5 , wherein the channel matrix is adaptively changed by checking a channel every time there is a need for retransmission.

7. The method of claim 5 , wherein the channel matrix is expressed as

H

M

×

N

=

(

h

11

h

12

⋯

h

1

⁢

N

h

21

h

22

⋮

⋮

⋱

⋮

h

M

⁢

⁢

1

…

…

h

M

⁢

⁢

N

)

.

8. A transmission apparatus for ordering retransmissions in a Multi-Input Multi-Output (MIMO) system using N×M antennas, the apparatus comprising:

a channel encoder for encoding input information bits based on a coding scheme, and generating coded packets having a specific length;

a spatial demultiplexer for encoding the coded packets based on a space-time coding scheme, and parallel-converting the encoded packets into N sub-blocks;

symbol mappers for modulating the N sub-blocks output from the spatial demultiplexer into modulation symbol streams using a modulation scheme, mapping the symbol streams to times and frequencies based on a pilot sub-carrier position set pattern, and outputting the mapping results to associated transmission antennas; and

N transmission antennas for separately transmitting N sub-packets split from each of the coded symbol streams,

wherein, upon receipt of a negative acknowledgement (NACK) due to errors included in the transmitted sub-packets, the transmission apparatus arranges columns of a retransmission matrix based on an Alamouti space-time coding scheme in a descending order of signal to noise ratios (SNRs), and retransmits a retransmission sub-packet according to the arranged columns to a reception apparatus.

9. The transmission apparatus of claim 8 , wherein a signal-to-noise ratio (SNR) criterion of each reception antenna, determined at the receiver at every retransmission, is used for selection of the retransmission ordering.

10. The transmission apparatus of claim 9 , wherein a highest SNR of each reception antenna maximizes a determinant that derives a channel matrix after each retransmission.

11. The transmission apparatus of claim 10 , wherein the channel matrix is adaptively changed by checking a channel every time there is a need for retransmission.

12. The transmission apparatus of claim 10 , wherein the channel matrix is expressed as

H

MxN

=

(

h

11

h

12

⋯

h

1

⁢

N

h

21

h

22

⋮

⋮

⋱

⋮

h

M

⁢

⁢

1

⋯

⋯

h

MN

)

.

13. A reception apparatus for ordering retransmissions in a Multi-Input Multi-Output (MIMO) system using N×M antennas, the apparatus comprising:

M reception antennas for separately receiving N sub-packets split from a coded symbol stream;

a pre-combiner for combining a sub-packet retransmitted according to retransmission ordering, with a previous defective sub-packet on a symbol level; and

a detector for removing interference of a signal received from the pre-combiner, splitting the interference-removed signal into N transmission data sub-packets after said removing, and outputting independently decoded sub-packets;

wherein the reception apparatus transmits one of an acknowledgement (ACK) and a negative acknowledgement (NACK) to a transmission apparatus depending on errors included in the decoded sub-packets and receives from the transmission apparatus the retransmitted sub-packet in response to the NACK transmitted by the reception apparatus, and the retransmission ordering comprises arranging columns of a retransmission matrix based on an Alamouti space-time coding scheme in descending order of signal to noise ratios (SNRs).

14. The reception apparatus of claim 13 , wherein the interference removing is achieved by Minimum Mean Square Examination (MMSE) or Zero Forcing (ZF).

15. The reception apparatus of claim 13 , wherein a signal-to-noise ratio (SNR) criterion of each reception antenna, determined at the receiver at every retransmission, is used for selection of the retransmission ordering.

16. The reception apparatus of claim 15 , wherein a highest SNR of each reception antenna maximizes a determinant that derives a channel matrix after each retransmission.

17. The reception apparatus of claim 16 , wherein the channel matrix is adaptively changed by checking a channel every time there is a need for retransmission.

18. The reception apparatus of claim 16 , wherein the channel matrix is expressed as

H

M

×

N

=

(

h

11

h

12

⋯

h

1

⁢

N

h

21

h

22

⋮

⋮

⋱

⋮

h

M

⁢

⁢

1

…

…

h

M

⁢

⁢

N

)

.

19. A method for ordering retransmissions in a Multi-Input Multi-Output (MIMO) system using N×M antennas, the method comprising:

splitting, by a transmitter, a coded data stream into N sub-packets;

transmitting the N sub-packets from the transmitter to a receiver via N transmission antennas;

removing, at the receiver, interferences of the N sub-packets received via M reception antennas, and independently decoding the interference-removed sub packets;

receiving by the transmitter from the receiver, a negative acknowledgement (NACK) in response to errors included in the N sub-packets received by M reception antennas that have had their interferences removed and been independently decoded by the receiver;

arranging, by the transmitter, columns of a retransmission matrix based on an Alamouti space-time coding scheme in descending order of signal to noise ratios (SNRs); and

retransmitting from the transmitter to the receiver a retransmission sub-packet according to the arranged columns in response to the received NACK.

20. A reception method for retransmissions in a Multi-Input Multi-Output (MEMO) system using N×M antennas, the method comprising:

transmitting, by a receiver, one of an acknowledgement (ACK) and a negative acknowledgement (NACK) to a transmitter depending on errors included in one or more decoded sub-packets;

receiving, from the transmitter, a packet retransmitted in response to the NACK;

receiving N sub-packets split from a coded symbol stream separately by M reception antennas;

combining, by a pre-combiner, the packet retransmitted according to a retransmission ordering, with a previous defective packet on a symbol level;

removing, by a detector, interference of a signal received from the pre-combiner;

splitting, by the detector, the interference-removed signal into N transmission data sub-packets; and

outputting, by the detector, independently decoded sub-packet signals,

wherein the retransmission ordering comprises arranging columns of a retransmission matrix based on an Alamouti space-time coding scheme in descending order of signal to noise ratios (SNRs).