Multi-Layer Iterative LDPC Decoding for Broadband Wireless Access Networks: A Recursive Shortening Algorithm

This paper presents a novel multi-layer iterative decoding scheme using deterministic bits to lower the decoding threshold of LDPC codes in wireless multimedia communication systems. These deterministic bits serve as known information in the LDPC decoding process to reduce the redundancy during data transmission. Unlike the existing work, our proposed scheme addresses the controllable deterministic bits, such as MPEG null packets, rather than the widely investigated protocol headers. In particular, our multi-layer scheme integrates deterministic bit identification into LDPC decoding process. This integration is able to make significant performance improvement if adequate deterministic bits are discovered. We find that the length of deterministic bits may vary from time to time, and the exploring of deterministic bits is associated to a series of shortened parity matrices during the decoding iterations. Accordingly, we develop a recursive LDPC shortening algorithm to match the dynamic length and facilitate the iterative identification of deterministic bits. Simulation results show that our proposed scheme can achieve considerable gain in today's most popular broadband wireless access networks such as WiMAX.