Physical Layer Security in Wireless Ad Hoc Networks Under A Hybrid Full-/Half-Duplex Receiver Deployment Strategy

This paper studies physical layer security in a wireless ad hoc network with numerous legitimate transmitter-receiver pairs and eavesdroppers. A hybrid full-duplex (FD)/half-duplex receiver deployment strategy is proposed to secure legitimate transmissions, by letting a fraction of legitimate receivers work in the FD mode sending jamming signals to confuse eavesdroppers upon their information receptions, and letting the other receivers work in the half-duplex mode just receiving their desired signals. The objective of this paper is to choose properly the fraction of FD receivers for achieving the optimal network security performance. Both accurate expressions and tractable approximations for the connection outage probability and the secrecy outage probability of an arbitrary legitimate link are derived, based on which the area secure link number, network-wide secrecy throughput, and network-wide secrecy energy efficiency are optimized, respectively. Various insights into the optimal fraction are further developed, and its closed-form expressions are also derived under perfect self-interference cancellation or in a dense network. It is concluded that the fraction of FD receivers triggers a non-trivial tradeoff between reliability and secrecy, and the proposed strategy can significantly enhance the network security performance.

I. Introduction

The rapid development in wireless communications has brought unprecedented attention to information security. Traditionally, security issues are addressed at the upper layers of communication protocols by using encryption. However, the large-scale and dynamic topologies in emerging wireless networks pose a great challenge in implementing secret key management and distribution, particularly in a decentralized wireless ad hoc network without infrastructure support [1]. Fortunately, physical layer security, an information-theoretic approach that attains secure transmissions by exploiting the randomness of wireless channels without necessarily relying on secret keys, is becoming increasingly recognized as a promising alternative to complement the cryptography-based security mechanisms [2]–[7].