Distributed Low-Density Lattice Codes

This letter presents a novel distributed LDLC (D-LDLC) relaying scheme for the classical relay channel. The relay node decodes LDLC packets from the source and forwards an additional parity message to the destination. The destination then performs joint decoding in order to exploit the available coding gain as well as diversity gain. First, assuming AWGN links, density evolution is used to optimize the noise threshold of the overall parity-check matrix, and this method is shown to produce good finite-length D-LDLC designs. Then, we provide results for the optimized D-LDLCs under Rayleigh fading channel conditions. Joint decoding based on D-LDLC is shown to provide approximately 3 dB gain over distributed 4-PAM turbo codes under the same conditions (data rate and overall transmission power).

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