An improved ensemble of variable-rate LDPC codes with precoding

In this paper, we apply the precoding technique developed by Abbasfar et al. for ARA codes to the original rate-compatible LDPC codes introduced in [1] to obtain an improved ensemble of variable-rate LDPC codes, which perform universally well over the AWGN channel in the low to high code-rate region. The proposed codes will be named precoded Kite codes. The Extrinsic Information Transfer (EXIT) chart is used to optimize the code performance. Numerical results show that the precoded Kite codes can achieve a coding gain of up to 0.3 dB over the codes in [1]. A performance comparison is also made between the proposed codes and the Raptor codes over the AWGN channel. It is shown that the proposed codes outperform the Raptor codes universally in a wide code rate range over AWGN channels. Extensive simulation results confirm that precoded Kite codes perform close to capacity within a range of code rates from 0.1 to 0.9.