Dynamic Spectrum Scheduling and Management in Centralized Cognitive Radio Networks

Abstract

As the demand for wireless radio spectrum increases, spectrum regulatory authorities expect to face a spectrum scarcity problem.As the demand for wireless radio spectrum increases, spectrum regulatory authorities expect to face a spectrum scarcity problem. Dynamic Spectrum Access (DSA) was recently proposed to enable efficient utilization of the radio spectrum. Cognitive Radio (CR)s are used to help in the realization of efficient DSA techniques. An integral component in Cognitive Radio Network (CRN), and in DSA in general, is scheduling, which has to do with the Secondary User (SU)’s ability to decide on the available spectrum that best meets its Quality of Service (QoS) requirements. Switching delay, which is defined as the time needed by a SU to hop among available channels, is a major factor that affects the performance of CRNs. This study is motivated by the fact that the literature is in need for efficient schedulers that can maximize the CRN’s through-put while maintaining a minimum spectrum switching delay for the SUs. Specifically, two scheduling techniques are introduced with the aim of minimizing the switching de-lay and hence maximizing the amount of transmitted information over the underlying CRN. The first scheduler is an opportunistic spectrum and switching-delay aware scheduler with the objective of maximizing the total number of transmitted packets over the span of multiple time-slots. From the simulation results, the opportunistic scheduler, in highly dynamic channels, was able to transmit up to 20% more packets compared to the benchmark scheduling algorithm where the scheduling problem is done every timeslot. Moreover, the scheduler was able to reduce the effect of both switching and scheduling delays. On the other hand, the second proposed scheduler maximizes spectrum exploitation by allowing unscheduled SUs to utilize any idle spectrum during the switching delay. From the results, the proposed scheduler allowed for≈38% more SUs to be scheduled in an overpopulated CRN. Moreover, by utilizing the switching delay, the proposed scheduler was able to deliver around 4.5% more packets compared to the benchmark algorithm without sacrificing any complexity. In conclusion, both of the implemented schedulers delivered a higher amount of transmitted packets compared to the benchmark scheduling algorithms and both schedulers were able to reduce the effect of switching delay.