Cooperative based tit-for-tat strategies to retaliate against greedy behavior in VANETs

In this paper, we address the problem of greediness in IEEE 802.11 CSMA/CA protocol in Vehicular Ad-hoc Networks (VANETs). In VANETs some nodes might misbehave by deviating from following the CSMA/CA standard medium access protocol, in order to increase their channel access probability. Such behavior may have a catastrophic impact on the network performance as it causes denial of service for the other cooperative nodes. To overcome such a problem, a motivational mechanism is needed to incentivize vehicles to comply with the protocol design in such distributed networks. Classical, Generous and Reputation based tit-for-tat strategies have been proposed to study the interaction among vehicles. However, these strategies are not able to enforce the cooperation since they rely on one-to-one monitoring that is not resilient to collisions. In this paper, we propose two collaborative-based tit-for-tat strategies that are identified as Group Reputation and Cooperative Detection strategies. Both strategies are able to improve the misbehavior detection decision and thus impose the MAC-layer cooperation in VANETs. In Group Reputation tit-for-tat strategy, the reputation is aggregated from the node's neighbors while in Cooperative Detection tit-for-tat strategy, a cooperative detection mechanism is proposed. These strategies are (1) immune to the ambiguous monitoring caused by collisions and (2) able to force the greedy nodes to cooperate under the threat of retaliation. Simulation results are conducted using NS-3 to demonstrate the performance of the proposed strategies compared to other strategies. Simulation results revealed that the two proposed strategies outperformed the other strategies in minimizing the effect of the interpretation errors and maximizing the throughput of the cooperative nodes.