Design of good low-density parity-check codes for block fading channels

The paper focuses on the design of good irregular low density parity check (LDPC) codes for Rayleigh block fading channels using a strategy of joint channel estimation and LDPC decoding. It is assumed that the amplitude of the fading coefficient is unknown. A density evolution technique employing a semi-Gaussian approximation is used to find good degree sequences for irregular LDPC codes for channels with different block memory sizes. The capacity of the BPSK-modulated Rayleigh block fading channel with unknown fading amplitude is used as a benchmark. For a block fading channel with a memory size of 20 bits, the best irregular LDPC code found has a threshold that is 0.47 dB away from the channel capacity.