Secure Massive MIMO Transmission with an Active Eavesdropper

TL;DR

This paper analyzes secure massive MIMO systems under active eavesdropping attacks during training, deriving asymptotic secrecy rates and optimal power policies, and exploiting channel correlation diversity to enhance security.

Contribution

It provides a novel asymptotic secrecy rate analysis for massive MIMO with active eavesdroppers and proposes strategies to mitigate pilot contamination effects.

Findings

Asymptotic achievable secrecy rate derived for large antenna arrays.

Optimal power allocation policy for single-antenna eavesdropper identified.

Channel correlation diversity can fully mitigate secrecy rate loss.

Abstract

In this paper, we investigate secure and reliable transmission strategies for multi-cell multi-user massive multiple-input multiple-output (MIMO) systems with a multi-antenna active eavesdropper. We consider a time-division duplex system where uplink training is required and an active eavesdropper can attack the training phase to cause pilot contamination at the transmitter. This forces the precoder used in the subsequent downlink transmission phase to implicitly beamform towards the eavesdropper, thus increasing its received signal power. Assuming matched filter precoding and artificial noise (AN) generation at the transmitter, we derive an asymptotic achievable secrecy rate when the number of transmit antennas approaches infinity. For the case of a single-antenna active eavesdropper, we obtain a closed-form expression for the optimal power allocation policy for the transmit signal and the AN, and find the minimum transmit power required to ensure reliable secure communication. Furthermore, we show that the transmit antenna correlation diversity of the intended users and the eavesdropper can be exploited in order to improve the secrecy rate. In fact, under certain orthogonality conditions of the channel covariance matrices, the secrecy rate loss introduced by the eavesdropper can be completely mitigated.