Görünür ışık ile iletişim destekli güvenli ve verimli otonom taşıt grubu mimarisi

Autonomous vehicles use a variety of sensors together with advanced software to drive without any human input. Autonomous vehicle platoon is an enhancement of autonomous behaviour where vehicles are organized into groups of close proximity through wireless communication with the goal of improving traffic throughput, transportation safety, fuel consumption and emissions. The chain of platoons that follow each other, on the other hand, refer to multiplatoon. Autonomous platoon and multiplatoon systems mostly adopt the current dominant vehicular radio frequency (RF) technology, IEEE 802.11p (DSRC), for communication among vehicles. However, DSRC suffers from problems of performance degradation due to congestion, the scarcity of RF and security. Visible Light Communication (VLC) is a recently proposed alternative communication technology with the potential of addressing problems by exploiting the directivity and impermeability of light. However, utilizing only VLC in vehicle platoon may degrade platoon stability since VLC is sensitive to environmental effects, i.e. fog, and might have short-term unreachability due to the increase in the inter-vehicle distance and/or loss of line-of-sight on a curvy road. In this thesis, hybrid usage of DSRC and VLC is investigated to achieve secure and efficient architecture for the vehicular platoons. First, we experimentally analyze the characteristics of vehicular VLC in different scenarios including single and dual channel data transmission considering various light dimming level and bearing angle of values with the goal of determining the usage limitation of VLC in the vehicular environment. We demonstrate that state of the art Lambertian radiation pattern does not represent the automotive light emitting diode (LED) radiation pattern accurately. Dual channel usage increases the angular limitation by up to 10\degree ~compared to the single channel VLC and dimming is a key parameter in VLC, which affects data dissemination and received power signal strength. Second, we propose an DSRC and VLC based hybrid security protocol for platoon communication, namely SP-VLC, with the goal of ensuring platoon stability and securing platoon maneuvers under data packet forgery, data packet replay, fake maneuver packet and jamming attacks. We define platoon maneuver attack based on the identification of various scenarios where a fake maneuver request packet or a fake maneuver response packet is transmitted by a malicious actor on the road side. SP-VLC includes mechanisms for secret key establishment and periodic update via VLC to ensure the participation of only the target vehicle in communication; authentication using of message authentication code to ensure the packet integrity; data transmission over both DSRC and VLC incorporating the encryption and decryption of the packets using the secret key generated between consecutive platoon members to exploit the complementary propagation characteristics of data transmission; jamming detection and reaction to switch to VLC only communication based on packet reception characteristics; and secure platoon maneuvering based on the joint usage of DSRC and VLC. We demonstrate the functionality of the proposed SP-VLC protocol under all possible security attacks by both providing a detailed analysis and performing extensive simulations. We develop a simulation platform combining realistic vehicle mobility model, realistic VLC and DSRC channel models and vehicle platoon management and demonstrate that SP-VLC protocol generates less than 0.1\% difference in the speed and distance variation of platoon members during attacks in comparison to 25\% and 10\% in that of previously proposed DSRC and DSRC-VLC hybrid protocols, respectively. Third, we propose a DSRC and VLC based safety message dissemination protocol for multiplatoon to satisfy the hard delay and high packet delivery ratio constraints of the safety application under application level data traffic. Vehicles utilize VLC for safety message dissemination within the platoon when the multiplatoon has high vehicle density leading to high medium contention. DSRC is adopted for platoon based data dissemination when VLC is disconnected within the dissemination distance. We demonstrate that the proposed hybrid protocol improves both packet delivery ratio and delay by limiting the contention to the line-of-sight vehicles.