1. Modeling and Evaluation of Backoff Misbehaving Nodes in CSMA/CA Networks

With the advancement with flexible and configurable wireless adapters, it becomes feasible for a node to modify its low-layer (e.g. physical or MAC layer) parameters, which can substantially affect the network performance of a wireless network. Backoff misbehavior, in which a node deliberately manipulates its backoff time, can induce significant network problems, such as severe unfairness and denial-of-service. Although great progress has been made towards the design of countermeasures to backoff misbehavior, little attention has been focused on quantifying the gain of backoff misbehaviors. In this chapter, to assess the gain that misbehaving nodes can obtain, we introduce a new metric, namely order gain, to characterize the performance benefits of misbehaving nodes in comparison to legitimate nodes in CSMA/CA-based wireless networks. We derive the order gains of a variety of misbehaviors and further investigate the relation between our metric, order gain, and the throughput gain for a misbehaving node. We show that in IEEE 802.11 networks, the throughput ratio of a backoff misbehaving node to a legitimate node is either bounded above or proportional to the number of legitimate nodes. We use both simulations and experiments to validate our theoretical analysis and to further demonstrate the impact of a wide range of backoff misbehaviors on network performance in CSMA/CA-based wireless networks.