LDPC Codes for Fading Channels: Two Strategies

This paper compares two approaches to reliable communication over fading channels using low-density parity check (LDPC) codes. The particular model considered is the block fading channel with independent channel realizations. The first approach uses a block interleaver to create independent sub-channels that are encoded using irregular LDPC codes with rates specified by the appropriate capacity values; this first approach uses a decision feedback structure wherein decoded data are used as pilots to estimate the channel prior to the next round of decoding. The second approach uses a combined graph describing both the channel and the code to iteratively estimate the channel and decode data. For comparable channels, it is shown that the decision-feedback approach provides better performance when a long delay is acceptable, while the iterative receiver provides better performance when more stringent delay constraints are imposed.