On the Concatenated Transmission Scheme With the Low-Complexity Symbol-Level Watermark Decoder for Recovering the Synchronization

The Davey–MacKay (DM) concatenated code employing the symbol-level watermark decoding algorithm is able to correct a large number of binary insertions, deletions, and substitutions, while it has the high computational complexity for recovering the synchronization. In the DM concatenated scheme, at the large insertion/deletion probability, in order to achieve the reliable output, the watermark decoder needs to perform the forward and backward passes on a very large trellis. In this paper, a threshold is selected to prevent the paths having very low forward and backward quantities from participating in the calculation of log-likelihood ratios from the watermark decoder. Simulation results show that great reduction in the complexity of the decoding algorithm is achieved at a very slight expense of accuracy.