Synchronization of Variable-Length Constrained Sequence Codes

Abstract

We study the ability of recently developed variable-length constrained sequence codes to determine codeword boundaries in the received sequence upon initial receipt of the sequence and if errors in the received sequence cause synchronization to be lost. We first investigate construction of these codes based on the finite state machine description of a given constraint, and develop new construction criteria to achieve high synchronization probabilities. Given these criteria, we propose a guided partial extension algorithm to construct variable-length constrained sequence codes with high synchronization probabilities. With this algorithm we construct new codes and determine the number of codewords and coded bits that are needed to recover synchronization once synchronization is lost. We consider a large variety of constraints including the runlength limited (RLL) constraint, the DC-free constraint, the Pearson constraint and constraints for inter-cell interference mitigation in flash memories. Simulation results show that the codes we construct exhibit excellent synchronization properties, often resynchronizing within a few bits.

A New Detection Method for Noisy Channels With Time-Varying Offset

“…Systematic methods for designing Pearson codes that efficiently translate (arbitrary) source data into n-bit codewords in the codebook S = {0, 1} n \ {0} and vice versa have been presented in [11,12,13]. The rate of the encoder, 0018-9448 (c) 2021 IEEE.…”