Physical Layer Security in Downlink Multi-Antenna Cellular Networks

TL;DR

This paper analyzes physical layer security in downlink cellular networks with multi-antenna base stations, revealing how secrecy rates are affected by network parameters and proposing models for outage probability and optimal deployment density.

Contribution

It introduces a stochastic geometry and random matrix theory-based model to analyze secrecy rates and outage probabilities in cellular networks with RCI precoding.

Findings

Secrecy rate does not increase monotonically with transmit power.

There exists an optimal base station density for maximizing secrecy rate.

High transmit power can lead to secrecy outage in cellular networks.

Abstract

In this paper, we study physical layer security for the downlink of cellular networks, where the confidential messages transmitted to each mobile user can be eavesdropped by both (i) the other users in the same cell and (ii) the users in the other cells. The locations of base stations and mobile users are modeled as two independent two-dimensional Poisson point processes. Using the proposed model, we analyze the secrecy rates achievable by regularized channel inversion (RCI) precoding by performing a large-system analysis that combines tools from stochastic geometry and random matrix theory. We obtain approximations for the probability of secrecy outage and the mean secrecy rate, and characterize regimes where RCI precoding achieves a nonzero secrecy rate. We find that unlike isolated cells, the secrecy rate in a cellular network does not grow monotonically with the transmit power, and the network tends to be in secrecy outage if the transmit power grows unbounded. Furthermore, we show that there is an optimal value for the base station deployment density that maximizes the secrecy rate, and this value is a decreasing function of the signal-to-noise ratio.