5G wireless networks are expected to support massive user connections and exponentially increasing wireless services, which makes information security unprecedentedly important. As an emerging network security solution, physical layer security (PLS) takes advantage of the intrinsic characteristics of wireless channels, such as noise, interference, and fading, to degrade the received signal qualities at the malicious users, and achieves keyless secure transmission via signal design and signal processing approaches. In the past few years, the research on PLS has generated a large body of literature, with the topics ranging from information-theoretical studies to practical scheme design. However, it is still challenging to develop PLS solutions that well match the unique features of 5G networks. The aim of this special issue is to provide a venue to publish recent research achievements that address the challenges faced by 5G security.

In this special issue, eight papers were selected based on our rigorous peer review by qualified experts. The topics of the accepted manuscripts mainly include (a) advanced signal design for enhanced security, (b) cooperation based PLS techniques, (c) security provisioning for NOMA, (d) attack detection and countermeasures in 5G networks, and (e) PLS for 5G enabled Internet-of-Things. All accepted papers are briefly introduced as below.

The paper titled “Provoking the Adversary by Detecting Eavesdropping and Jamming Attacks: A Game-Theoretical Framework”, by A. Salem et al., developed a mechanism to detect the jamming and eavesdropping attacks launched by an adversary and analyzed the interactions between the legitimate user and the adversary using the stochastic game theory. Numerical results validated the efficiency of the proposed games.

In the paper “Adaptive OFDM-IM for Enhancing Physical Layer Security and Spectral Efficiency of Future Wireless Networks”, H. M. Furqan et al. proposed three approaches to enhance the physical layer security and improve the spectral efficiency of OFDM systems with Index Modulation. In the proposed schemes, different activation ratios and/or constellation modulation orders are selected adaptively for each subblock based on the legitimate user’s channel, such that a high error floor is created at the eavesdropper.

In the paper “Precoding-Aided Spatial Modulation for the Wiretap Channel with Relay Selection and Cooperative Jamming”, Z. Bouida et al. proposed a PLS scheme for dual-hop cooperative networks with an external eavesdropper. In the proposed scheme, precoding-aided spatial modulation (PSM) and relay selection techniques are combined such that both hops are secured. The authors also analyzed the system performance in terms of the ergodic secrecy rate and secrecy outage probability.

The impact of masquerading attack on the outage and capacity performance of cooperative relaying networks was investigated in “On the Performance of the DNPS-Based Relay Networks under Masquerading Attack”, authored by W. Chang. In this paper, multiple masquerade relays with random masquerading behavior were taken into account, and the geographical effect of the network topology was considered as well. This paper can be recognized as a first step to inspire the investigation of the masquerading attack for relay networks.

The paper entitled “Impact of Antenna Selection on Physical-Layer Security of NOMA Networks”, by D. Deng et al., studied the impact of antenna selection algorithms on decode-and-forward (DF) cooperative non-orthogonal multiple access (NOMA) networks, where the signal transmitted from the relay can be overheard by an eavesdropper. It was revealed that the system security performance is highly dependent on the system parameters such as the number of antennas at the relay, SNR, and main-to-eavesdropper ratio (MER).

Z. Xiang et al. proposed to exploit NOMA technique to enhance the uplink security performance in 5G-enabled Internet-of-Things (IoT) in their paper “Exploiting Uplink NOMA to Improve Sum Secrecy Throughput in IoT Networks”. The authors derived the closed-form expressions for joint connection outage probability, joint secrecy outage probability, and sum secrecy throughput. Based on the theoretical results, the condition that NOMA outperforms OMA was presented.

In the paper titled “On Secrecy Outage Probability and Average Secrecy Rate of Large-Scale Cellular Networks”, L. Tao et al. investigated the secrecy performance in large-scale cellular networks, where both base stations and eavesdroppers follow independent and different homogeneous Poisson point processes (PPPs). The exact expressions for the secrecy outage probability and average secrecy rate at the typical user were presented by using the tool of stochastic geometry.

The paper entitled “Probabilistic Caching Placement in the Presence of Multiple Eavesdroppers”, by F. Shi et al., studied the physical-layer security for the caching aided networks. In this work, the authors designed, analyzed, and optimized the probabilistic caching placement in the presence of multiple eavesdroppers. Simulation results were provided to exhibit the superiority of the proposed probabilistic caching placement compared to the competing solutions.

Conflicts of Interest

The authors declare that there are no conflicts of interest regarding the publication of this article.


The guest editors would like to thank the authors for their great contributions to this special issue. We also appreciate the experts who participated in the peer review process and provided constructive comments which significantly improved the quality of the manuscripts.

Li Sun
Kamel Tourki
Yafei Hou
Lu Wei