Capacity-Approaching Variable-Length Constrained Sequence Codes

Abstract

In this thesis we consider construction techniques and applications of variable-length constrained sequence codes. First we present background information related to constrained sequence coding theory and review a recently reported technique for constructing variable-length constrained sequence codes. We then outline original work. We demonstrate two new general algorithms that we have developed to construct variable-length constrained sequence codes for various types of constraints. The first is based on an encoder with a single encoding state, while the second is based on an encoder with multiple encoding states which retains the property of state-independent decoding. We present examples of these construction algorithms. Then we apply our coding technique to develop constrained sequence codes for flash memory with multi-page programming in order to reduce the impact of inter-cell interference and cell leakage. Lastly we study the synchronization properties of the codes we developed, and show that it is possible to design variable-length constrained sequence codes with good synchronization properties such that once the receiver loses synchronization, it regains synchronization within a limited number of codewords.