Enhance routing metric based optimized link state routing (OLSR) protocol for VANET

Abstract

Vehicular Ad Hoc Networks (VANETs) grasp the interest of researchers and many governmental agencies as technological solution for human’s transportation systems. VANETs aims at providing connectivity among vehicles on the road and infrastructure network in ad hoc communications scheme. In VANETs each vehicle uses a routing mechanism to find a path for sending its messages to the last destination, where messages are sent in a multi hop fashion. The behavior emphasis the impact of the routing protocol mechanism in the performances of VANETs. In recent years, the analysis of VANETs routing protocols and their impact on the performances of network with different network scenarios has significantly developed a precise understanding of the requirements and goals for designing a VANETs routing protocol. Further, in the literature many routing protocol mechanisms are proposed to deal with VANET’s requirements. Nonetheless, proposed routing mechanisms in the literature considered a single network scenario in VANETs. However, Vehicles or moving nodes in VANETs are tending to travel in long distances, which implies their engagement in multiple network scenarios and topologies. The adhered behavior of VANET’s nodes results in a need for a routing mechanism that addresses the requirement of more than one network scenarios and topologies. This problem is less considered in the literature. Hence, this thesis proposes VANETs Expected Transmission Time (VETT) routing metric to tackle the dynamic topology changes in VANETs. The proposed metric defines the performances of Optimized link stat routing protocol (OLSR) in different network scenarios as an objective optimization problem. The proposed mechanism is integrated with OLSR protocol as geographical routing protocol. Extensive simulation results are presented by comparing between the performances of optimized and non-optimized routing mechanisms. The mechanisms are evaluated for varying network metrics including traffic density, packet size, and number of cars for two network topologies; city and highway. The results show that the proposed routing metric (VETT) improves the performance of OLSR for multiple VANET scenarios in-terms of delay, packet delivery ratio (PDR), packet loss, and throughput. The objective optimization mechanism (VETT) reduces the delay by more than 30% and increases the PDR and throughput by more than 15%. Furthermore, the performance analysis of routing protocols for different VANET scenarios shows divergences in the performances of a single routing protocol in different scenarios. This supports the hypothesis that network topology has a major impact on the routing protocol performances. This thesis concludes that the optimization of routing protocol is necessary to improve the performances of VANET. A single objective optimization results in a great routing performances improvement. However, it is not capable of improving more than one performances simultaneously.