Evaluation of low-density parity-check codes over block fading channels

Richardson, Shokrollahi, Urbanke have proposed irregular low-density parity-check codes (LDPCCs) that outperform, on memoryless channels, the best known turbo-codes. These results have been obtained by allowing the degree of each node (variable or check) of a LDPCC to vary according to some distribution. In this paper we investigate the performance of such new codes over block fading channels (i.e. channels with memory), in terms of bit and codeword error rates adopting the standard decoding algorithm and a modified version which slightly improves performance. Also, a numerical comparison with conventional convolutional codes is carried out. For a code rate 1/2, it results that irregular LDPCCs are convenient only for large codeword size (greater than 500 bits), and that the gain with respect to a constraint length 7 convolutional code decreases considerably with the channel memory.