Multi-dimensional detector for receiver of MIMO system

1. A multi-dimensional detector for a receiver of a multiple input multiple output (MIMO) system, comprising:

a first symbol detecting means for calculating symbol distance values of a symbol using an upper triangular matrix (R) obtained from QR decomposition, to detect an m th symbol, wherein ‘Q’ denotes a unitary matrix and ‘m’ is a positive integer greater than one;

a symbol deciding means for deciding the m th symbol having a minimum distance value among the calculated symbol distance values from the first symbol detecting means;

a column removing and updating means for removing an mth column of the upper triangular matrix R from the decided m th symbol, and updating a received signal; and

a second symbol detecting means for calculating symbol distance values based on the updated received signal y and the column removed upper triangular matrix R, to detect a (m−1) th symbol.

2. The multi-dimensional detector of claim 1 , further comprising:

a first log likelihood ratio calculating means for calculating a first log likelihood ratio using the symbol distance values outputted from the first symbol detecting means; and

a second log likelihood ratio calculating means for calculating a second log likelihood ratio using the symbol distance values outputted from the second symbol detecting means.

3. The multi-dimensional detector of claim 1 , wherein each of the first and second symbol detecting means includes:

a symbol generating means for generating symbols;

a plurality of symbol distance calculating means for receiving the upper triangular matrix R and the generated symbols and sequentially performing hard decision for the received symbols and calculating symbol distance values for the received symbols; and

a buffering means for storing the calculated distance values from the symbol distance calculating means.

4. The multi-dimensional detector of claim 3 , further comprising:

registers for temporally storing each of the updated received signals and providing the temporally stored updated received signals to the symbol distance calculating means for a next iteration of symbol distance calculation.

5. The multi-dimensional detector of claim 4 , wherein each of the symbol distance calculating means includes:

a plurality of shifting and adding means for shifting each of inputted triangular matrices R as much as symbols generated from the symbol generating means and adding the shifted matrices;

a calculating means for calculating a distance value to detect a symbol using the results of the shifting and adding means, a previous hard decision result, and an updated received signal; and

a hard decision means for performing hard decision for a newly updated received signal based on the results of the shifting and adding means.

6. The multi-dimensional detector of claim 5 , wherein the calculating means subtracts column values of an upper triangular matrix R of the shifting and adding means, which is selected by a previous hard decision result, from the updated received signal, and calculates a distance value for an own symbol by accumulating the subtracting result with a previous symbol distance value.

7. The multi-dimensional detector of claim 5 , wherein the hard decision means includes:

a plurality of calculating means for receiving a real part and an imaginary part of an updated received signal and performing calculation on an upper triangular matrix R vector with the received real part and imaginary part; and

a comparing means for deciding a plurality of bits by comparing the real part and the imaginary part with a predetermined value and comparing each of the outputs of the calculating means with a predetermined value,

wherein hard decision is performed by mapping the decided bits to a lattice point structure of a symbol.

8. A multi-dimensional detecting method being performed via a receiver of a multiple input multiple output (MIMO) system, comprising:

calculating, via a first symbol detector, symbol distance values of a symbol using an upper triangular matrix R obtained from QR decomposition, to detect an m th symbol, wherein ‘Q’ denotes a unitary matrix and ‘m’ is a positive integer greater than one;

deciding, via a symbol decider, the m th symbol having a minimum distance value among the calculated symbol distance values;

removing, via a column remover, an m th column of the upper triangular matrix R from the decided m th symbol and updating a received signal; and

calculating, via a second symbol detector, symbol distance values using the updated received signal and the column removed upper triangular matrix R, to detect a (m−1) th symbol.

9. The multi-dimensional detecting method of claim 8 , further comprising:

calculating a first log likelihood ratio using the symbol distance values outputted from said calculating symbol distance values using the upper triangular matrix R; and

calculating a second log likelihood ratio using the symbol distance values outputted from said calculating symbol distance values using the updated received signal.

10. The multi-dimensional detecting method of claim 8 , wherein said calculating symbol distance values using the upper triangular matrix R includes:

generating symbols;

sequentially performing hard decision for each symbol and calculating symbol distance values to detect the m th symbol using the upper triangular matrix R and the generated symbols; and

accumulating the calculated symbol distance values for each symbol and storing the accumulated symbol distance value.

11. The multi-dimensional detecting method of claim 10 , wherein said the sequentially performing hard decision includes:

performing hard decision for a (m−1) th symbol, calculating distance values of an m th symbol, and outputting the updated received signal;

performing hard decision for a (m−2) th symbol using the updated received signal, calculating distance values of a (m−1) th symbol, and newly updating the updated received signal; and

performing a process of performing hard decision for a next symbol, calculating distance values of an own symbol using the updated received signal, and updating the updated received signal y until a first symbol.

12. The multi-dimensional detecting method of claim 11 , wherein the distance values of the m th symbol are calculated by subtracting a multiplying result of an m th element of the upper triangular matrix R and the m th element of the generated symbol from a multiplying value of a constant C and an m th received signal vector and squaring an absolute value of the subtracting result.

13. The multi-dimensional detecting method of claim 11 , wherein distance values of the (m−1) th symbol are calculated by subtracting a multiplying result of a (m−1) th element of the upper triangular matrix R and the (m−1) th element of hard decision element from an updated (m−1) th received signal, squaring an absolute value of the subtracting result, and accumulating the squaring result and the distance values of the m th symbol.

14. The multi-dimensional detecting method of claim 12 , wherein the multiplying result of the m th element of the upper triangular matrix R and the m th element of the generated symbol is subtracted after shifting the upper triangular matrix R as much as the generated symbols.

15. A receiver of a multiple input multiple output (MIMO) system, comprising:

a QR decomposing means for decomposing a received signal to an unitary matrix Q and an upper triangular matrix R; and

a multi-dimensional detecting means for deciding an m th symbol and a (m−1) th symbol, wherein ‘m’ is a positive integer greater than one, through multi-dimensional detection for the output of the QR decomposing means,

wherein the multi-dimensional detecting means includes:

a first symbol detecting means for calculating symbol distance values of a symbol using the upper triangular matrix (R) obtained from QR decomposition, to detect the m th symbol;

a symbol deciding means for deciding the m th symbol having a minimum distance value among the calculated symbol distance values from the first symbol detecting means;

a column removing and updating means for removing an m th column of the upper triangular matrix R from the decided m th symbol, and updating a received signal; and

a second symbol detecting means for calculating symbol distance values using the updated received signal and the column removed upper triangular matrix R, to detect a (m−1) th symbol.

16. The apparatus of claim 15 , wherein the multi-dimensional detecting means further includes:

a first log likelihood ratio calculating means for calculating a first log likelihood ratio using the symbol distance values outputted from the first symbol detecting means; and

a second log likelihood ratio calculating means for calculating a second log likelihood ratio using the symbol distance values outputted from the second symbol detecting means.