Design and Analysis of a Concatenated Code for Intersymbol Interference Wiretap Channels

TL;DR

This paper introduces a two-stage concatenated coding scheme combining LDPC and trellis codes to achieve reliable and secure communication over intersymbol interference wiretap channels, optimizing for secrecy capacity.

Contribution

It presents a novel nested coding structure that achieves tight bounds on secrecy capacity and minimizes information leakage in wiretap channels.

Findings

Achieves tight lower bounds on secrecy capacity.

Optimizes LDPC degree distributions to ensure weak secrecy.

Estimates and bounds information leakage rate effectively.

Abstract

We propose a two-stage concatenated coding scheme for reliable and secure communication over intersymbol interference wiretap channels. We first establish the secrecy capacity. Then, motivated by the theoretical codes that achieve the secrecy capacity, our scheme integrates low-density parity-check (LDPC) codes in the outer stage, forming a nested structure of wiretap codes, with trellis codes in the inner stage to improve achievable secure rates. The trellis code is specifically designed to transform the uniformly distributed codewords produced by the LDPC code stage into a Markov process, achieving tight lower bounds on the secrecy capacity. We further estimate the information leakage rate of the proposed scheme using an upper bound. To meet the weak secrecy criterion, we optimize degree distributions of the irregular LDPC codes at the outer stage, essentially driving the estimated upper bound on the information leakage rate to zero.