Wireless communication, sensing, and REM: A security perspective

The diverse requirements of next-generation communication systems necessitate awareness, flexibility, and intelligence as essential building blocks of future wireless networks. The awareness can be obtained from the radio signals in the environment using wireless sensing and radio environment mapping (REM) methods. This is, however, accompanied by threats such as eavesdropping, manipulation, and disruption posed by malicious attackers. To this end, this work analyzes the wireless sensing and radio environment awareness mechanisms, highlighting their vulnerabilities and provides solutions for mitigating them. As an example, the different threats to REM and its consequences in a vehicular communication scenario are described. Furthermore, the use of REM for securing communications is discussed and future directions regarding sensing/REM security are highlighted

Novel Models and Algorithms Paving the Road towards RF Convergence

After decades of rapid evolution in electronics and signal processing, the technologies in communications, positioning, and sensing have achieved considerable progress. Our daily lives are fundamentally changed and substantially defined by the advancement in these technologies. However, the trend is challenged by a well-established fact that the spectrum resources, like other natural resources, are gradually becoming scarce. This thesis carries out research in the field of RF convergence, which is regarded as a mean to intelligently exploit spectrum resources, e.g., by finding novel methods of optimising and sharing tasks between communication, positioning, and sensing. The work has been done to closely explore opportunities for supporting the RF convergence. As a supplement for the electromagnetic waves propagation near the ground, ground-to-air channel models are first proposed and analysed, by incorporating the atmospheric effects when the altitude of aerial users is higher than 300 m. The status quos of techniques in communications, positioning, and sensing are separately reviewed, and our newly developments in each field are briefly introduced. For instance, we study the MIMO techniques for interference mitigation on aerial users; we construct the reflected echoes, i.e., the radar receiving, for the joint sensing and communications system. The availability of GNSS signals is of vital importance to the GNSS-enabled services, particularly the life-critical applications. To enhance the resilience of GNSS receivers, the RF fingerprinting based anti-spoofing techniques are also proposed and discussed. Such a guarantee on GNSS and ubiquitous GNSS services drive the utilisation of location information, also needed for communications, hence the proposal of a location-based beamforming algorithm. The superposition coding scheme, as an attempt of the waveform design, is also brought up for the joint sensing and communications. The RF convergence will come with many facets: the joint sensing and communications promotes an efficient use of frequency spectrum; the positioning-aided communications encourage the cooperation between systems; the availability of robust global positioning systems benefits the applications relying on the GNSS service

Physical Layer Authentication Using Intelligent Reflective Surfaces

The Intelligent Reflective Surface (IRS) is one of the key technologies that will increase the coverage of cellular networks and enhance their performance at a low cost. Moreover, the IRS will improve the performance of the Channel-based Physical layer Authentication security mechanism. In this thesis, we propose an authentication scheme that takes advantage of the presence of the IRS in the IRS-assisted multiple input multiple output (MIMO) system to improve the security performance of the system. The proposed cascaded channel estimation authentication scheme has been developed and compared with a systematic channel estimation authentication scheme. We consider a non-line of sight communication between the transmitter and the receiver through the IRS. We will also demonstrate the efficiency of the proposed scheme by comparing it with one of the commonly used schemes. Moreover, we will formulate the optimal attack strategies to test the security of the proposed scheme. The performance of the proposed scheme is evaluated, and the numerical results show the merit of the proposed approach that can be adopted as a Physical layer authentication mechanism.The Intelligent Reflective Surface (IRS) is one of the key technologies that will increase the coverage of cellular networks and enhance their performance at a low cost. Moreover, the IRS will improve the performance of the Channel-based Physical layer Authentication security mechanism. In this thesis, we propose an authentication scheme that takes advantage of the presence of the IRS in the IRS-assisted multiple input multiple output (MIMO) system to improve the security performance of the system. The proposed cascaded channel estimation authentication scheme has been developed and compared with a systematic channel estimation authentication scheme. We consider a non-line of sight communication between the transmitter and the receiver through the IRS. We will also demonstrate the efficiency of the proposed scheme by comparing it with one of the commonly used schemes. Moreover, we will formulate the optimal attack strategies to test the security of the proposed scheme. The performance of the proposed scheme is evaluated, and the numerical results show the merit of the proposed approach that can be adopted as a Physical layer authentication mechanism