Improving the Finite-Length Performance of Spatially Coupled LDPC Codes by Connecting Multiple Code Chains

Pablo M. Olmos

University Carlos III de Madrid

Abstract:

We analyze the finite-length performance of codes on graphs constructed by connecting spatially coupled low-density parity-check (SC-LDPC) code chains. First, we review existing results to analyze the finite-length performance of SC-LDPC code chains and we show that short (low rate) code chains present more robust decoding properties than long (higher rate) chains, i.e., the scaling between block error rate and gap to threshold is more favorable for shorter chains. Codes constructed by connected SC-LDPC code chains are also analyzed. In certain scenarios, in addition to superior iterative decoding thresholds, connected chain ensembles present better finite-length performance than single chain ensembles of the same rate and length. However, these gains tend to vanish as we consider longer SC-LDPC code chains. All these results will be easily explained using the finite-length analysis tools described above. In order to improve the finite-length performance of systems using long SC-LDPC code chains, we present a novel encoding/transmission scheme, where, instead of transmitting codewords corresponding to a single SC-LDPC chain independently, we connect consecutive chains in a multi-layer format to form a connected chain ensemble. We refer to such a transmission scheme to as continuous chain (CC) transmission of SC-LDPC codes. We show that CC transmission can be implemented with no significant increase in encoding/decoding complexity or decoding delay with respect a system using a single SC-LDPC code chain for encoding.

Biography:

Pablo M. Olmos was born in Granada, Spain, in 1984. He received the M.Sc./B.Sc.degrees in telecommunication engineering in 2008 and the Ph.D. degree in telecommunication engineering in 2011 from the University of Sevilla. He is currently an assistant professor at University Carlos III de Madrid. He has visited Princeton University, École Polytechnique Fédérale de Lausanne (EPFL), Notre Dame University and École Nationale Supérieure de l'Electronique et de ses Applications (ENSEA) as invited researcher.