On the windowed encoding complexity of SC-LDGM codes for lossy source compression

It has been shown that spatially coupled low-density generator-matrix (SC-LDGM) code ensembles display distortion saturation for the lossy binary symmetric source coding problem with belief propagation guided decimation algorithms, in the sense that the distortion of the SC-LDGM code ensemble approaches the optimal distortion of the underlying (uncoupled) LDGM block code ensemble. This has also been demonstrated for the class of protograph-based SC-LDGM code ensembles with windowed encoding (WE), where distortion close to the rate distortion limit was obtained with low-latency encoding. In this paper, we propose and compare two decimation techniques for lowering the WE complexity of SC-LDGM codes that maintain distortion performance close to the rate-distortion bound.