Universal LDPC codes for cooperative communications

Abstract

Cooperative communication is a well known technique to yield transmit diversity in the case of fading channels and to increase the spectral efficiency in the case of Gaussian channels. Error-correcting codes have to be carefully designed to achieve the promised gains. Good LDPC codes are known for fading channels and for Gaussian channels, but an LDPC code ensemble that performs well on both channels has not yet been presented in the literature. This paper merges two families of LDPC codes into a universal LDPC code ensemble for both fading channels and Gaussian channels. Furthermore, the new universal LDPC code ensemble outperforms previously proposed codes on the block fading channel, which is explained through a fading space analysis. Simulation of the word error rate performance of the new proposed family of LDPC codes shows that it performs well on both fading channels and Gaussian channels

Low-Density Graph Codes for Coded Cooperation on Slow Fading Relay Channels

“…This does not directly serve the performance analysis for the BF channel. However, an analysis in the real space of the fading coefficients has shown that this can be used to increase the coding gain on a BF relay channel [12]. But the optimization of the coding gain is outside the scope of this paper and here we will only use Proposition 5 in the application of Eq.…”

“…In more recent work [12] we optimized the degree distribution using the analysis of Section V. Another method is based on density evolution with a modified Gaussian approximation that takes into account the SNR variation in one received codeword as well as the rate-compatibility constraint [28].…”