Receiving apparatus and demodulating method

A receiving apparatus employed in a Multi-Input Multi-Output (MIMO) system in which a first data sequence and a second data sequence are encoded with Low Density Parity Check (LDPC) codes and transmitted via different antennas, comprising:

• a propagation path estimation unit configured to estimate propagation paths of a plurality of receive signals received via different antennas, using the receive signals;
• a space filtering unit configured to separate the receive signals to a signal of a first data sequence and a signal of a second data sequence on the basis of an estimation result of the propagation path estimation unit;
• a provisional decoding unit configured to LDPC-decode the signal of the first data sequence and the signal of the second data sequence with check matrices which is modified in different forms by fundamental row operation from each other, to obtain a provisional likelihood ratio for the first data sequence and the second data sequence, respectively;
• a soft replica signal generation unit configured to generate a soft replica signal, on the basis of the provisional likelihood ratio for the first data sequence and the second data sequence and the estimation result of the propagation path estimation unit;
• a soft decision outputting unit configured to obtain receive likelihood values of the first data sequence and the second data sequence, respectively, on the basis of a residual signal obtained by subtracting the soft replica signal from the receive signals;
• an actual decoding unit configured to LDPC-decode the receive likelihood values, by using the check matrices, respectively, to obtain a likelihood ratio of the first data sequence and a likelihood ratio of the second data sequence;
• and
• a decision unit configured to obtain the first data sequence and the second data sequence on the basis of the likelihood ratio of the first-data sequence and the likelihood ratio of the second data sequence generated by the actual decoding unit, respectively.

A demodulating method employed in a Multi-Input Multi-Output (MIMO) system in which a first data sequence and a second data sequence are encoded with Low Density Parity Check (LDPC) codes and transmitted via different antennas, comprising:

• (a) estimating propagation paths of a plurality of receive signals received via different antennas;
• (b) separating the receive signals to a signal of a first data sequence and a signal of a second data sequence on the basis of an estimation result of the step (a);
• (c) LDPC-decoding the signal of the first data sequence and the signal of the second data sequence with check matrices which is modified in different forms by fundamental row operation from each other, to obtain a provisional likelihood ratio for the first data sequence and a likelihood ratio of the second data sequence, respectively;
• (d) outputting provisional first data sequence and provisional second data sequence on the basis of the provisional likelihood ratio for the first data sequence and the second data sequence, respectively;
• (e) generating a replica signal, on the basis of the provisional first data sequence and the provisional second data sequence and the estimation result of the step (a);
• (f) obtaining receive likelihood values of the first data sequence and the second data sequence, respectively, on the basis of a residual signal obtained by subtracting the replica signal from the receive signals;
• (g) LDPC-decoding the receive likelihood values by using the check matrices, respectively, to obtain a likelihood ratio of the first data sequence and a likelihood ratio of the second data sequence;
• and
• (h) obtaining the first data sequence and the second data sequence on the basis of the likelihood ratio of the first data sequence and the likelihood ratio of the second data sequence generated by the actual decoding unit, respectively.

A demodulating method employed in a Multi-Input Multi-Output (MIMO) system in which a first data sequence and a second data sequence are encoded with Low Density Parity Check (LDPC) codes and transmitted via different antennas, comprising:

• (a) estimating propagation paths of a plurality of receive signals received via different antennas, using the receive signals;
• (b) separating the receive signals to a signal of a first data sequence and a signal of a second data sequence on the basis of an estimation result of the step (a);
• (c) LDPC-decoding the signal of the first data sequence and the signal of the second data sequence with check matrices which is modified in different forms by fundamental row operation from each other, to obtain a provisional likelihood ratio for the first data sequence and the second data sequence, respectively;
• (k) generating a soft replica signal, on the basis of the provisional likelihood ratio for the first data sequence and the likelihood ratio of the second data sequence and the estimation result of the step (a);
• (f) obtaining receive likelihood values of the first data sequence and the second data sequence, respectively, on the basis of a residual signal obtained by subtracting the soft replica signal from the receive signals;
• (g) LDPC-decoding the receive likelihood values, by using the check matrices, respectively, to obtain a likelihood ratio of the first data sequence and a likelihood ratio of the second data sequence;
• and
• (l) obtaining the first data sequence and the second data sequence on the basis of the likelihood ratio of the first data sequence and the likelihood ratio of the second data sequence generated by the actual decoding unit, respectively.