Performance of improved AR3A code over EPR4 channel

High rate low-density parity-check (LDPC) codes have been under intense research in the serial concatenation of inner Extend partial-response Class 4(EPR4) and outer LDPC codes due to their decoding performance close to the Shannon capacity. The Accumulate Repeat-3 and Accumulate (AR3A) codes, viewed as a subclass of protograph LDPC codes, achieve good decoding performance with simple linear encoder structure and flexible code rates via puncturing variable nodes, which makes us consider the potential of serially concatenating the EPR4 channel with AR3A codes. Simulation results show that AR3A codes can´t preserve their performance advantages over regular LDPC codes in the EPR4 channel, although they surpass regular LDPC codes in the AWGN channels. This paper proposes an improved AR3A code where we change the puncturing method, that is, the degree-1 variable nodes are punctured instead of degree-5 ones. The performance curves verify that the improved AR3A code possesses better decoding performance than the regular LDPC code in EPR4 channels and still keeps its original excellent characteristics of low hardware complexity.