Low complexity soft-input Viterbi decoding for digital communication systems

A method comprising:

• providing a data stream;
• rearranging a sequence of the data stream into a digital bit sequence using bit-wise and symbol-wise interleaving;
• mapping said digital bit sequence according to a predetermined modulation scheme;
• introducing a channel factor to a modulated digital bit sequence;
• demapping said modulated digital bit sequence;
• de-interleaving the demapped digital bit sequence using bit-wise and symbol-wise de-interleaving;
• decoding a soft decision metric computation comprising a log-likelihood ratio (LLR) soft decision metric of a binary bit stream of a signal, wherein said LLR corresponding to said binary bit stream of a signal equals
• 1
• 4
• ⁢
• (
• m
• 0
• ⁡
• (
• c
• l
• )
• -
• m
• 1
• ⁡
• (
• c
• l
• )
• )
• ,
• wherein cl represents transmitted code of said binary bit stream, wherein m0 represents a minimum Euclidean distance from a received soft decision symbol to hard decision symbols in a subset of constellation points with an ith bit equal to zero, and wherein m1 represents a minimum Euclidean distance from said received soft decision symbol to said hard decision symbols in said subset of constellation points with said ith bit equal to one;
• and
• decoding the de-interleaved digital bit sequence using a Viterbi decoder.

A communication system comprising:

• a convolutional encoder;
• an interleaver operatively connected to said convolutional encoder;
• a quadrature amplitude modulation (QAM) mapper operatively connected to said interleaver;
• a channel component operatively connected to said QAM mapper;
• a QAM demapper operatively connected to said channel component;
• a de-interleaver operatively connected to said QAM demapper, wherein said de-interleaver is adapted to decode a soft decision metric computation comprising a log-likelihood ratio (LLR) soft decision metric of a binary bit stream of a signal, and wherein said soft decision metric of a kth symbol of a received noisy QAM symbol, yk, said LLR corresponding to an ith bit in a kth symbol of a received noisy QAM symbol, yk, equals
• 1
• 4
• ⁢
• (
• m
• 0
• ⁡
• (
• y
• k
• ,
• i
• )
• -
• m
• 1
• ⁡
• (
• y
• k
• ,
• i
• )
• )
• ,
• wherein m0 represents a minimum Euclidean distance from a received soft decision symbol to hard decision symbols in a subset of constellation points with an ith bit equal to zero, and wherein m1 represents a minimum Euclidean distance from said received soft decision symbol to said hard decision symbols in said subset of constellation points with said ith bit equal to one;
• and
• a Viterbi decoder operatively connected to said de-interleaver.