Performance Evaluation of Physical Layer Security in sub-THz band for UAV Communications

Abstract

Wireless communication systems anticipate a surge in demand for higher data rates due to the increased number of interconnected devices, which is expected to double approximately every 18 months. However, the current data rates still fall short of the 100 Gbps rate required for various applications such as immersive virtual reality and high-quality video streaming. While millimeter wave has provided a larger bandwidth compared to microwave frequencies, it remains inadequate. Therefore, the Terahertz (THz) band has emerged as an essential component in dealing with the ever-increasing volume of data traffic and meeting the growing need for broader coverage and higher data rates in the 6G and future wireless networks. Its potential impact is tremendous, as it can greatly enhance a diverse range of applications such as Internet of Everything (IoE) and Unmanned aerial vehicles (UAVs). UAV-enabled THz technology is expected to play a major role in next generation wireless communications. However, the obstacles to utilize THz communication for UAV are challenging due to THz limitations and the mobility of UAVs. For example, increasing the transmission range of a signal in sub-Terahertz (0.1-10 THz) frequency band has been a challenge due to its vapor loss and molecular absorption. It is more challenging in UAV communications because of dynamic network topology and weather conditions. The focus of this dissertation is to improve physical layer security and minimizing path loss in THz-enabled UAV communication systems. A channel model is established specifically for THz-enabled UAVs. Additionally, UM-MIMO is evaluated across three distinct frequency bands (0.06, 0.3, and 1 THz). We have proposed an optimization problem that maximizes the secrecy rate of UAVs in the sub-THz band by optimizing their trajectories and transmit power jointly. To solve this optimization problem, we have designed an iteration algorithm based on Successive Convex Approximation. To enhance the achievable average secrecy rate for UAV ground communications, we have utilized UM-MIMO and a cooperative UAV jamming strategy. Furthermore, we studied THz channel model for line-of-sight (LoS) and non-line of sight (NLoS) for UAV communication and examined its physical layer security under different scenarios. Additionally, we investigated UAV trajectories in sub-THz band and its effect on the secrecy rate of the UAVs communication. Moreover, we present a novel secure UAV-assisted mobile relaying system operating at THz bands for a cognitive relay network. We have developed a PUF-based mutual authentication solution that exploits the physical-layer properties of communication links. We leverage the growing popularity of MIMO in wireless communication. This approach incorporates hardware-based security primitives, namely physically unclonable functions (PUFs), and physical-layer communication mechanism (MIMO). This protocol allows a UAV and a ground user to authenticate each in a distributed manner.