Non-systematic low-density parity-check codes for nonuniform sources

Messages coded and transmitted over a channel may contain some redundancy, which is usually not utilized by standard channel decoding techniques. Non-systematic codes have a potential for significant advantage over systematic codes if a method is found to utilize such redundancy. We propose a novel general encoder/decoder structure for non-systematic low-density parity-check (LDPC) codes, that can be used in several different configurations for efficiently exploiting redundancy in decoding of redundant data sequences. Simulation results for one configuration of this method demonstrate clear performance gains over standard systematic LDPC codes when a decoder utilizes the source redundancy for decoding of redundant data sequences. These gains increase as the non-uniformity of the source increases, and also with use of some of the other configurations of the new general method