Adaptive incentive-compatible routing in VANETs for highway applications

Vehicular Ad-hoc Networks (VANETs) experience diverse network environments ranging from infrastructure based with dense connected vehicle communication in urban highways to infrastructurless with sparse connected vehicle communication in rural highways. Routing protocols in such challenging environments should be adaptive to work with or without a fixed infrastructure under a quickly varying connected vehicle density. They should also be incentive-compatible in order to guarantee that their adaptive routing decisions are followed by all participants. In this paper, we propose a novel routing protocol for highway applications that is both adaptive and incentive-compatible. It is adaptive by switching between: Vehicle-to-Infrastructure (V2I) routing, Vehicle-to-Vehicle (V2V) direct routing and V2V delay-tolerant routing. It is also incentive-compatible as shown by the resulting Nash Equilibrium using a game theoretic analysis. In this analysis, we show how incentives are administered by the fixed network operator through a credit-based exchange system. Cooperative relay vehicles, with high credit balances, are rewarded with extra bandwidth allocations whereas selfish relay vehicles, with low credit balances, are punished with less bandwidth allocations. The fixed network operator administers this credit-based exchange system in order to maintain acceptable user experience by complementing the congestion-prone V2I routing with properly-incentivized V2V direct routing and V2V delay-tolerant routing. Our protocol has been evaluated using our in-house built simulation environment with realistic channel and highway mobility models. Results demonstrate the efficacy of the proposed protocol in comparison to other routing protocols.