LDPC coded bit interleaved orthogonal modulation with non-coherent detection

Abstract

In this paper, we investigate the design and optimization of low-density parity-check (LDPC) coded bit interleaved orthogonal modulation systems with non-coherent detection over flat Rayleigh fading channels. We show that, two different EXIT chart analysis aspects can be done for this system, but the conventional approach cannot be used to optimize the system. With the aid of our designed EXIT chart analysis scheme and the linear programming method, the degree distribution for the variable nodes of the adopted LDPC code is optimized. The EXIT chart analyses show that, after optimization, the performance of the designed system is very close to channel capacity, i.e. the gap between them is only about 0.1 dB, which is much closer than those proposed in the existing literatures. Simulation results are also presented with different code lengths, indicating that the performance of the proposed system can approach that predicted by EXIT chart analysis as the code length becomes infinite.