Simplified log-likelihood ratio calculation for binary LDPC codes

Abstract

Combining binary LDPC codes and high order constellations is a simple but effective way to improve the bandwidth efficiency. Since the binary LDPC codes require soft decisions as the input information, the constellation has to provide soft information calculated by Log-Likelihood Ratio (LLR) to it. In this paper, a simplified algorithm to calculate LLR for binary turbo-codes is applied for binary LDPC codes. Simulation results show that the simplified algorithm have a very small performance loss over Gaussian and Rayleigh channels.