Rate Adaptation for Secure HARQ Protocols

TL;DR

This paper proposes a novel rate adaptation strategy for IR-HARQ protocols in secure communications, optimizing dummy-message rates to enhance throughput and reduce delay over fading channels with eavesdroppers.

Contribution

It introduces a coding strategy that splits dummy-message rates across multiple parameters, improving secrecy and reliability in IR-HARQ systems.

Findings

Splitting dummy-message rate increases throughput.

The proposed method reduces average delay.

Performance surpasses existing benchmarks.

Abstract

This paper investigates the incremental-redundancy hybrid-automatic repeat request (IR-HARQ) transmission over independent block-fading channels in the presence of an eavesdropper, where the secrecy of the transmission is ensured via introduction of dummy-messages. Since the encoder only knows the statistics of the channel state, the secrecy and the reliability are defined in a probabilistic framework. Unlike previous works on this subject, we design a coding strategy tailored to IR-HARQ by splitting the dummy-message rate over several rate parameters. These additional degrees of freedom improve the match between the dummy-message rates and the realizations of the eavesdropper channels. We evaluate the performance in terms of secrecy outage probability, connection outage probability and throughput and we compare it with the benchmark paper by Tang et al. Numerical examples illustrate that, comparing to existing alternatives, splitting of the dummy-message rate provides higher throughput and lower expected duration/average delay.