Detection and Defense Scheme against Selfish Nodes in MAC-Layer

IEEE 802.11 is a set of media access control (MAC) and physical layer (PHY) specifications for implementing ad hoc networks. In ad hoc networks, selfish nodes deviating from the standard MAC (Medium Access Control) protocol degrades normal nodes performance and are difficult to detect. Specifically, the non-deterministic nature of the IEEE 802.11 MAC protocol imposes great challenges to distinguish selfish nodes from well-behaved nodes. The traditional selfish misbehavior detection approaches either rely on a large amount of historical data to perform detection, or employ throughput or delay models that are only valid in WLANs for detection. Since they are based on large amount of data, the detection may take very long time. The proposed real time detection scheme for multi hop ad hoc networks requires only few samples and can adapt to channel dynamics more quickly. The selfish nodes are detected based on certain parameters such as slot time, SIFS, DIFS. If a node is determined as selfish node, the penalty scheme is applied to punish the selfish node by decreasing its throughput and specifically, all its one hop neighbours stop forwarding the packets for it until they receive another decision notice indicating that this node is not selfish any more. Based on the detection there are 3 defense scheme namely, i) naive selfish node ii) random selfish node iii) γ-persistent selfish nodes. The defense schemes are designed to prevent the selfish nodes from degrading normal nodes performance.