Cognitive Radio Enabled Vehicular Ad Hoc Networks

Abstract

Vehicular communication is fast gaining popularity to facilitate safer, smarter, efficient and sustainable transportation through intelligent transport systems. Vehicular Ad Hoc Networks (VANETs) are decentralised wireless networks enabling direct communication between vehicles on the fly. VANETs can be used to exchange safety-related information as well as provide entertainment and convenience to travellers. These applications require high data throughputs, especially for the latter, making the dedicated bandwidth available for VANETs insufficient. Cognitive radio technology, which utilises existing under-utilised spectrum resources through opportunistic access, satisfies these throughput demands of VANETs. A simulation framework for application service management in VANETs was designed and developed to bridge the gap between existing simulators. This framework also supports modelling of multi-radio multi-channel communications and radio channel access mechanisms as per the IEEE WAVE standards. An additional simulation framework was developed for cognitive radio enabled VANETs to simulate vehicular nodes, primary user transmissions, spectrum sensing, and spectrum hand-offs. A three-state sensing model that uses a carrier sensing mechanism in addition to energy detection was developed to distinguish between the primary and secondary users. A higher probability of detection was observed with a sensing interval much shorter than the transmission signal duration of the primary user. Furthermore, the highest probability of detection was recorded with a sensing interval of 10% of the primary user signal duration. A dynamic sensing technique was employed as an attempt to reduce the system overheads, which inevitably increase with the reduced sensing interval, without compromising the accuracy of sensing. With this technique, the probability of detection remained unchanged, but a significant reduction of up to 90% was observed in the system overheads. An algorithm was developed to continuously evaluate the data congestion of all dedicated channels available for vehicular communication and select the least congested channel for cognitive radio signalling. As the framework addresses all aspects with attention to finer details, it is a compelling platform for all firmware and application developers in industrial and research communities alike.