Enhancing Intelligent Transportation Systems: Scalability, Emulation, and Applications of V2X Communication for Connected and Autonomous Vehicles

The integration of Vehicle-to-Everything (V2X) communication is a key advancement for Connected and Autonomous Vehicles (CAVs), enhancing the safety, efficiency, and intelligence of modern Intelligent Transportation Systems (ITS). While Autonomous Vehicles (AVs) rely heavily on onboard sensor data for situational awareness, they remain limited in non-line-of-sight scenarios, which can lead to critical driver errors and accidents. V2X communication extends this awareness by enabling real-time exchange of information beyond sensor range, improving decision-making and reducing collisions. Two primary V2X technologies are Dedicated Short-Range Communication (DSRC) and Cellular-V2X (C-V2X). While DSRC, based on IEEE 802.11p, was initially prominent in research, C-V2X, standardized by 3GPP Release 14, has gained increased attention due to its scalability, reliability, and support for high-speed vehicular communication. However, challenges persist in deploying V2X systems, especially in dense urban environments. Communication loss remains a significant issue, and large-scale testing with real vehicles is impractical. Existing simulators like NS-3 and OMNET++ suffer from long run-times, limiting their effectiveness in large-scale evaluations. Furthermore, the application, scalability, and robustness of both basic and advanced Cooperative Vehicle Safety (CVS) applications present significant challenges due to strict requirements of low latency, high reliability, and limited bandwidth. This dissertation addresses these challenges by proposing a set of scalable, efficient solutions for improving V2X communication under congestion. It investigates C-V2X performance over the PC5 sidelink interface under variable traffic conditions and presents techniques to mitigate congestion and reduce packet loss. A Remote Vehicle Emulator (RVE) is introduced for high-fidelity, near-real-time simulation of DSRC and C-V2X. A Driver Messenger System (DMS) is also proposed, which transmits Over-the-Air (OTA) Driver Intent Messages (DIMs) in scenarios like Lane Change and Stop-Controlled Intersections (SC-I), enhancing driver awareness and safety. Additionally, Collaborative Perception and Automated Vehicle Marshalling (AVM) are explored, using spatial sparsification and infrastructure communication for coordinated CAV movement, respectively.