Block length of LDPC codes in fading channels

In this paper we study the block length of LDPC codes on fading channels with respect to coding efficiency, immunity ot channel fading, decoding complexity and implementation complexity. LDPC codes are proved to approach near-Shannon limit of channel capacity when the length is long enough. It is desirable to have very long block length when the coding efficiency is concerned. Also thanks to the inherent "interleaver" effect, long codes are less likely to be completely corrupted in deep fades and can thus avoid serious performance degradation. However, the practical block length is confined by the implementation complexity of LDPC decoder, which increases significantly with block length. We show that for a given channel condition, there is a good block length that has the least decoding and implementation complexity whereas achieves the desired BER. A single path Rayleigh fading channel is employed in this study.