On the Delay Limited Secrecy Capacity of Fading Channels

TL;DR

This paper analyzes the maximum secure data transmission rate over fading channels with delay constraints, considering different levels of channel knowledge at the transmitter, and introduces a new approach to ensure secrecy.

Contribution

It introduces a novel two-stage method for delay-limited secrecy capacity analysis under varying channel state information scenarios.

Findings

Derived tight bounds on secrecy capacity with full CSI at high SNR

Established non-zero secure rates with only main channel CSI under delay constraints

Proposed a new approach to overcome secrecy outage issues

Abstract

In this paper, the delay limited secrecy capacity of the flat fading channel is investigated under two different assumptions on the available transmitter channel state information (CSI). The first scenario assumes perfect prior knowledge of both the main and eavesdropper channel gains. Here, upper and lower bounds on the secure delay limited capacity are derived and shown to be tight in the high signal-to-noise ratio (SNR) regime (for a wide class of channel distributions). In the second scenario, only the main channel CSI is assumed to be available at the transmitter. Remarkably, under this assumption, we establish the achievability of non-zero secure rate (for a wide class of channel distributions) under a strict delay constraint. In the two cases, our achievability arguments are based on a novel two-stage approach that overcomes the secrecy outage phenomenon observed in earlier works.