Methods for digital signal processing and transmission/reception systems utilizing said methods
Methods for digital signal processing and transmission/reception systems utilizing the methods based on the use of LDPC codes, for example the LDPC code with a 3/5 code rate, in combination with a QAM modulation, for example the 16 QAM or 64 QAM or 256 QAM modulation. In transmission, a bit permutation (Demux) is carried out prior to the QAM constellation mapping function, and in reception, the bit permutation is carried out after the QAM constellation demapping function.
1. A method for processing and transmitting digital signals to a QAM modulator of the 64QAM type, comprising:
encoding the signals in packets according to an LDPC code with a 3/5 code rate,
writing the packets into an interleaving matrix by an Interleaver block,
carrying out, by a Demux block, a bit permutation of the bits received from the Interleaver block prior to the constellation mapping function, wherein the permutation is carried out on 12-bit words,
generating a word Y comprising the bits y 0 y 1 y 2 y 3 y 4 y 5 y 6 y 7 y 8 y 9 y 10 y 11 , in this order, starting from a word B comprising the bits b 0 b 1 b 2 b 3 b 4 b 5 b 6 b 7 b 8 b 9 b 10 b 11 , in this order, the bits y 0 and b 0 being respectively the most significant bits of the words Y and B, and the bits y 11 and b 11 being respectively the least significant bits of the words Y and B, and wherein:
y0=b4, y1=b6, y2=b0, y3=b5, y4=b8, y5=b10, y6=b2, y7=b1, y8=b7, y9=b3, y10=b11, y11=b9.
2. A system comprising a QAM modulator, adapted to implement the method according to claim 1 .
3. A method for processing digital signals received by a QAM demodulator of the 64QAM type, comprising:
encoding the signals in packets according to an LDPC code with a 3/5 code rate,
writing the packets into an interleaving matrix by an Interleaver block,
carrying out, by a Demux block, a bit permutation of the bits received from the Interleaver block after the constellation demapping function, wherein the permutation is carried out on 12-bit words,
generating a word B comprising the bits b 0 b 1 b 2 b 3 b 4 b 5 b 6 b 7 b 8 b 9 b 10 b 11 , in this order, starting from a word Y comprising the bits y 0 y 1 y 2 y 3 y 4 y 5 y 6 y 7 y 8 y 9 y 10 y 11 , in this order, the bits y 0 and b 0 being respectively the most significant bits of the words Y and B, and the bits y 11 and b 11 being respectively the least significant bits of the words Y and B, wherein:
y0=b4, y1=b6, y2=b0, y3=b5, y4=b8, y5=b10 y6=b2, y7=b1, y8=b7, y9=b3, y10=b11, y11=b9.
4. A system for receiving digital signals comprising a QAM demodulator, adapted to implement the method according to claim 3 .