Secure Wireless Communication and Optimal Power Control under Statistical Queueing Constraints

TL;DR

This paper investigates secure wireless communication over fading channels with queueing constraints, defining effective secure throughput, and deriving optimal power control policies to maximize security and performance under buffer limitations.

Contribution

It introduces the effective secure throughput region for buffer-constrained fading broadcast channels and proposes algorithms for optimal power control policies to enhance security.

Findings

Effective secure throughput region is convex.

Optimal power control policies are derived for boundary points.

Opportunistic transmission is not optimal under buffer constraints.

Abstract

In this paper, secure transmission of information over fading broadcast channels is studied in the presence of statistical queueing constraints. Effective capacity is employed as a performance metric to identify the secure throughput of the system, i.e., effective secure throughput. It is assumed that perfect channel side information (CSI) is available at both the transmitter and the receivers. Initially, the scenario in which the transmitter sends common messages to two receivers and confidential messages to one receiver is considered. For this case, effective secure throughput region, which is the region of constant arrival rates of common and confidential messages that can be supported by the buffer-constrained transmitter and fading broadcast channel, is defined. It is proven that this effective throughput region is convex. Then, the optimal power control policies that achieve the boundary points of the effective secure throughput region are investigated and an algorithm for the numerical computation of the optimal power adaptation schemes is provided. Subsequently, the special case in which the transmitter sends only confidential messages to one receiver, is addressed in more detail. For this case, effective secure throughput is formulated and two different power adaptation policies are studied. In particular, it is noted that opportunistic transmission is no longer optimal under buffer constraints and the transmitter should not wait to send the data at a high rate until the main channel is much better than the eavesdropper channel.