Thesis (M.Sc.) - Cairo University - Faculty of Engineering - Department of Electronics and Communications

Cognitive Radio Vehicular Ad-hoc Networks (CR-VANETs) exploit the dynamic spectrum capability of cognitive radios to allow the vehicles to access the unused channels in their vicinity. The existing VANETs protocols are not originally designed as enablers for cognitive radios. Therefore, CR-VANETs do not only suffer the traditional CR problems, especially in spectrum sensing, but also suffer new challenges due to the highly dynamic nature of VANETs. This thesis presents a spectrum sensing and reporting protocol for non-safety applications, which counters the deficiencies of typical CR-VANETs in high-density networks. We introduce the Single Channel Slotted Contention (SC)² protocol for highly dense vehicular traffic on highways. The proposed protocol consists of three main components: random single channel sensing, slotted contention and implicit aggregation.The proposed (SC)² protocol can be easily incorporated with the IEEE 802.11p. Simulation results show that the proposed protocol increases the secondary throughput and spectrum utilization while significantly decreasing the radio environment map time in high densities when compared to the legacy IEEE 802.11p based protocols. A trade-off between the primary outages and the secondary throughput can be controlled via the contention window size. We also analytically study the collision probability and secondary throughput of the (SC)² and the IEEE 8021.11p based protocols

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