ABSTRACT
Recently, cognitive radio networks (CRNs) have attracted an increasing amount of interest as an effective method of alleviating the spectrum scarcity problem in wireless communications by allowing access of secondary users (SUs) to frequency channels that are allocated to primary users (PUs), in a way that does not affect the quality of service
12.1 Introduction 403 12.2 Optimal Transmission Duration 407 12.3 Cognitive MAC Protocol Design 411 12.4 Performance Analysis 413
12.4.1 Virtual Slot Model 413 12.4.2 Markov Chain Model 414
12.5 Simulation Results 417 12.5.1 Transmission-Throughput Trade-Off 418 12.5.2 Impact of Sensing Duration 420 12.5.3 Impact of the Secondary Network Density 420
12.6 Conclusions 422 Acknowledgment 423 References 423 Biographical Sketches 425
(QoS) of the primary networks [1,2]. The research on CRN has been encouraged by the Federal Communications Commission (FCC), which has revealed that there is a significant amount of licensed spectrum that is largely underutilized in vast temporal and spatial dimensions [3]. In order to reuse the available spectrum that is not being used under the current fixed spectrum allocation policy, the FCC has recently allowed the access of SUs to the broadcast television spectrum at locations where that spectrum is not being used by primary services, which is known as IEEE 802.22 wireless regional area network (WRAN) standard [4] that aims to provide broadband wireless Internet access to rural areas.
