Spectrum-Map-Empowered Opportunistic Routing for Cognitive Radio Ad Hoc Networks

Cognitive radio (CR) has emerged as a key technology for enhancing spectrum efficiency by creating opportunistic transmission links. Supporting the routing function on top of opportunistic links is a must for transporting packets in a CR ad hoc network (CRAHN) consisting of cooperative relay multiradio systems. However, there lacks a thorough understanding of these highly dynamic opportunistic links and a reliable end-to-end transportation mechanism over the network. Aspiring to meet this need, with innovative establishment of the spectrum map from local sensing information, we first provide a mathematical analysis to deal with transmission delay over such opportunistic links. Benefitting from the theoretical derivations, we then propose spectrum-map-empowered opportunistic routing protocols for regular and large-scale CRAHNs with wireless fading channels, employing a cooperative networking scheme to enable multipath transmissions. Simulations confirm that our solutions enjoy significant reduction of end-to-end delay and achieve dependable communications for CRAHNs, without commonly needed feedback information from nodes in a CRAHN to significantly save the communication overhead at the same time.