Opportunistic Secrecy with a Strict Delay Constraint

TL;DR

This paper analyzes the delay-limited secrecy capacity of flat fading channels under different transmitter channel state information scenarios, providing bounds and achievable rates with novel key-sharing strategies.

Contribution

It introduces a new two-stage key-sharing approach to achieve secure rates under delay constraints, addressing secrecy outage issues in fading channels.

Findings

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

Established non-zero secure rates with only main channel CSI for various distributions.

Proposed a novel key-sharing method overcoming secrecy outage phenomena.

Abstract

We investigate the delay limited secrecy capacity of the flat fading channel 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 delay limited secrecy capacity are derived, and shown to be tight in the high signal-to-noise ratio (SNR) regime. In the second scenario, only the main channel CSI is assumed to be available at the transmitter where, remarkably, we establish the achievability of a non-zero delay-limited secure rate, for a wide class of channel distributions, with a high probability. In the two cases, our achievability arguments are based on a novel two-stage key-sharing approach that overcomes the secrecy outage phenomenon observed in earlier works.