Physical-Layer Security in the Finite Blocklength Regime over Fading Channels

TL;DR

This paper analyzes physical-layer security over fading channels considering finite blocklength effects, proposing optimal transmission strategies and demonstrating how blocklength and secrecy rate influence throughput.

Contribution

It introduces a comprehensive framework for optimizing secrecy throughput in finite blocklength regimes over fading channels, including adaptive schemes and artificial noise techniques.

Findings

Increasing blocklength improves secrecy throughput.

Secrecy throughput increases with blocklength.

Optimal secrecy rate balances rate and decoding accuracy.

Abstract

This paper studies physical-layer secure transmissions from a transmitter to a legitimate receiver against an eavesdropper over slow fading channels, taking into account the impact of finite blocklength secrecy coding. A comprehensive analysis and optimization framework is established to investigate secrecy throughput for both single- and multi-antenna transmitter scenarios. Both adaptive and non-adaptive design schemes are devised, in which the secrecy throughput is maximized by exploiting the instantaneous and statistical channel state information of the legitimate receiver, respectively. Specifically, optimal transmission policy, blocklength, and code rates are jointly designed to maximize the secrecy throughput. Additionally, null-space artificial noise is employed to improve the secrecy throughput for the multi-antenna setup with the optimal power allocation derived.Various important insights are developed. In particular, 1) increasing blocklength benefits both reliability and secrecy under the proposed transmission policy; 2) secrecy throughput monotonically increases with blocklength; 3) secrecy throughput initially increases but then decreases as secrecy rate increases, and the optimal secrecy rate maximizing the secrecy throughput should be carefully chosen in order to strike a good balance between rate and decoding correctness. Numerical results are eventually presented to verify theoretical findings.