Cross-layer tradeoff of QoS and security in Vehicular ad hoc Networks: A game theoretical approach

Abstract

Vehicular ad hoc Networks (VANETs) have high requirements on both Quality of Service (QoS) and security due to their unique wireless features such as highly dynamic vehicles and unreliable channels. However, it is challenging to jointly optimize QoS and security because they are conflicting objectives that contend for limited network resources. Therefore, it is essential to make a tradeoff between them. In this study, a two-period game is designed to deal with the external decision-making of vehicles and internal resource competition of an individual vehicle, respectively. In the first-period external decision-making, each vehicle aims to maximize the throughput by constructing a cross-layer utility between Medium Access Control (MAC) and Physical (PHY) layers. Moreover, the optimal transmission power of the external decision-making is obtained as the vehicle’s best strategy, which serves as an input in the next period. In the second-period internal decision-making, the conflicting objectives, i.e., QoS and security, inside an individual vehicle are viewed as two abstract players who compete for the vehicle’s limited resources. Furthermore, a general game is formulated for the internal decision-making to model the behaviors of the “communication player” in controlling the number of data blocks and that of the “security player” in deciding the hash length. The theoretical value of the Nash equilibrium of the internal game is derived and proved to be the two players’ optimal strategy composition. The simulation results demonstrate that the proposed game enables a vehicle to obtain satisfactory QoS and security levels by dynamically adjusting its optimal strategies according to the situated network and traffic environment.