Noisy channels with synchronization errors : information rates and code design

Abstract

Synchronization errors are omnipresent in practical communication systems. However, their effect is usually negligible in the signal to noise ratio (SNR) range of interest. But as the ever-increasing potency of error-correcting codes pushes down the SNR limits for reliable communication, timing errors are expected to become the main performance-limiting factor. Hence, it is important to study the effect of injecting timing errors in standard channels.In this work, we investigate a more realistic, yet mathematically tractable model of timing errors. The quantized timing errors are modeled as a first order Markov chain. In the first part of this thesis, we develop a finite-state model for a channel suffering from additive noise and timing errors. We then present Monte Carlo methods for upper and lower bounding the information rates over such channels. In the later part, we present concatenated channel codes, which are capable of error-correction as well as timing recovery.