Finite-length EXIT analyses for protograph LDPC codes over underwater acoustic channels

摘要

The conventional infinite-length extrinsic information transfer (EXIT) charts would not be accurate for short-length coded systems, because short-length coded sequences do not possess ergodicity as infinite-or very-long length coded sequences. In this paper, we concern with the finite-length EXIT analysis, which is developed for protograph low-density parity-check (PG-LDPC) codes over underwater acoustic (UWA) channels. The finite-length EXIT analysis is thus exploited for analyzing the practical instead of asymptotic performance of short-length coded UWA communication systems limited by bandwidth and power. Due to the poor performance of the conventional PG-LDPC codes, a rate 1/2 protograph-based construction of LDPC code for the UWA channel is proposed. The finite-length EXIT analysis show that the proposed codes are superior to the conventional PG-LDPC codes and the (3, 6) regular LDPC code with the same code length, agreeing well with the bit-error-rate (BER) simulation results.