An Overarching Review on Taxonomy of Routing Metric in Concurrence with Trust and Security for CRAHN

Cognitive radio technology is introduced to solve the problem of spectrum paucity by providing efficient, dynamic and opportunistic use of frequency bands. Wireless devices with cognitive capability refer as cognitive radio users and when these devices topologically arranged in ad hoc manner without any centralized entity termed as cognitive radio ad hoc network (CRAHN). Ironically, however CRAHN deals with major issues like network topology, frequency band change, and unpredictable PU behavior and spectrum variation temporally and spatially. In this paper, we present survey of recent routing protocols in CRAHN. Initially, routing challenges in CRAHN is addressed. Thereafter, we present the different routing metric which is classified into seven categories like end-to-end Delay, hop count, PDR, reliability, throughput, energy efficient and location centric. After surveying above routing protocols, we have seen that reactive routing protocol is more popular among all. This survey also focuses on routing protocols that have considered two key issues for improving Path trustworthiness and data security while communication. It also shed light on the open issues for designing and implementing the routing protocols in CRAHN.