BilayerProtographCodesforHalf-DuplexRelayChannels.PDFVIP

IEEE TRANSACTIONS ON WIRELESS COMMUNICATIONS, VOL. 12, NO. 5, MAY 2013 1969 Bilayer Protograph Codes for Half-Duplex Relay Channels Thuy Van Nguyen, Student Member, IEEE, Aria Nosratinia, Fellow, IEEE, and Dariush Divsalar, Fellow, IEEE Abstract—Despite encouraging advances in the design of relay reduced to the following: a code and its sub-code must codes, several important challenges remain. Many of the existing be designed simultaneously that operate with two different LDPC relay codes are tightly optimized for fixed channel con- rates at two different SNRs at the relay and the destination, ditions and not easily adapted without extensive re-optimization of the code. Some have high encoding complexity and some need respectively. Despite some progress, LDPC codes for the relay long block lengths to approach capacity. This paper presents channel are often painstakingly optimized to match to a set a high-performance protograph-based LDPC coding scheme for of channel conditions without a structure to facilitate the the half-duplex relay channel that addresses simultaneously sev- optimization of design, and many of them do not offer easy eral important issues: structured coding that permits easy design, encoding. This paper proposes a class of LDPC relay codes low encoding complexity, embedded structure for convenient adaptation to various channel conditions, and performance close that address three important issues in an integrative manner: to capacity with a reasonable block length. The application of low encoding complexity, modular structure allowin