Improving the security for future wireless communications

Intelligent reflecting surface (IRS) is a communication technology that holds great promise for its potential to improve the performance of wireless data transmission systems. A research team has investigated the potential of the aerial intelligent reflecting surface (AIRS) and shown its ability to improve communication security.

The research team, with scientists in China and the United Kingdom, published their findings on April 29 in the journal Intelligent and Converged Networks at DOI: https://doi.org/10.23919/ICN.2022.0020.

The research team studied an IRS carried by an unmanned aerial vehicle (UAV), also known as a drone, to help the communication between the ground nodes. Because of the small size and low power consumption of the IRS, it can be easily mounted on an aerial platform such as  a drone, to form  an AIRS with flexible deployment, which means it can be put up or taken down where there is no communications infrastructure easily available. While UAV-enabled wireless communication offers strong possibilities, because of the openness characteristic of the UAV-to-ground link, the signal that is transmitted by the UAV to the ground station is vulnerable to be eavesdropped. So communication security has become an essential piece of the puzzle in studying the UAV communication network.

The IRS has been increasingly gaining attention in wireless communities. The IRS consists of a large number of low-cost passive reflecting elements with the adjustable phase shifts. When the phase shifts of the IRS’s elements are properly, their reflected signals can combine with those from other paths coherently to enhance the link achievable rate. Since the IRS does not employ any transmit radio frequency (RF) chains, energy consumption only comes from reflective elements phase adjustment, which is usually very low. With its relative simplicity, intelligence, and energy efficient properties, IRS has recently gathered extensive interest from researchers.

“Our main aim was to exploit the potential of the AIRS in secure communication, where the IRS is carried by a rotary wing UAV to reflect the incident signal,” said Hehao Niu, a professor at the Institute of Electronic Countermeasure, National University of Defense Technology. To solve the formulated non-convex secrecy rate problem, the researchers developed an alternating optimization algorithm to obtain the suboptimal solution. Specifically, the team optimized the reflecting coefficients using the Riemannian manifold optimization based method. They deployed the AIRS using the successive convex approximation technique. Taking it a step further, they employed an element-wise block coordinate descent (EBCD) method to reduce the computational complexity. Their simulation results show a significant improvement in security with the assistance of AIRS.

While the researchers set out to explore the potential of AIRS in secure communication, they also found other potential applications. AIRS can also be utilized in other application scenarios where the goal is to enlarge the coverage of wireless networks or to reflect the signal to users that are obscured by tall buildings, said Zheng Chu, a professor with the Institute for Communication Systems, University of Surrey.

Looking ahead, the research team plans to expand their study. “We will extend this work to include cases where the UAV is flying from an initial point to a destination within a given time. Thus, we will try to jointly design the UAV's trajectory and the reflecting coefficients of the IRS,” said Zhengyu Zhu, a professor at the School of Information Engineering, Zhengzhou University.

In thinking about their future work, the team would like to study the AIRS-assisted secure communication with multi-antenna ground nodes. Because of the imperfect channel estimation and feedback, another possible future work is to develop a more robust design for the AIRS-assisted communication.

The National Natural Science Foundation of China, the Open Fund of the Shaanxi Key Laboratory of Information Communication Network and Security, the China Postdoctoral Science Foundation, and the Henan Postdoctoral Foundation provided funding for this research.

The authors of this study include Hehao Niu, Institute of Electronic Countermeasure, National University of Defense Technology; Zheng Chu, Institute for Communication Systems, University of Surrey; Zhengyu Zhu, School of Information Engineering, Zhengzhou University; and Fuhui Zhou, College of Electronic and Information Engineering, Nanjing University of Aeronautics and Astronautics.

The paper is also available on SciOpen (https://www.sciopen.com/home) by Tsinghua University Press.

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About Intelligent and Converged Networks 

Intelligent and Converged Networks is an international specialized journal that focuses on the latest developments in communication technology. The journal is co-published by Tsinghua University Press and the International Telecommunication Union (ITU), the United Nations specialized agency for information and communication technology (ICT). Intelligent and Converged Networks draws its name from the accelerating convergence of different fields of communication technology and the growing influence of artificial intelligence and machine learning.

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