ABSTRACT
Contents 2.1 Classification of Cognitive Radio Networks . . . . . . . . . . . . . . . . . . . . . . . . . . 30
2.1.1 Noninterfering CR Networks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30 2.1.2 Interference-Tolerant CR Networks . . . . . . . . . . . . . . . . . . . . . . . . . . 31 2.1.3 Central Access CR Networks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32 2.1.4 Ad Hoc CR Networks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33 2.1.5 Capacity Analysis: The State of the Art and Motivation . . . . . . 33
2.2 Transmit Power Control . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35 2.3 Capacity Analysis of a Central Access Cognitive Radio Network . . . . 39
2.3.1 System Model . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39 2.3.2 Capacity Analysis and Numerical Results . . . . . . . . . . . . . . . . . . . . . 39
2.4 Capacity Analysis of a Cooperative Cognitive Radio Network . . . . . . . 41 2.4.1 System Model . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 41 2.4.2 Cooperative Communications and Signaling . . . . . . . . . . . . . . . . . 41
2.4.3 Capacity Analysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 44 2.4.4 Results and Discussions. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 46
2.5 Conclusions and Open Issues . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50 2.6 Appendix: Derivation of (2.4) through (2.9) . . . . . . . . . . . . . . . . . . . . . . . . . 51 References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 52
Current static and rigid spectrum licensing policy has resulted in very inefficient spectrum utilization [1-3]. Cognitive radio (CR) [4-8] has been extensively researched in recent years as a promising technology to improve spectrum utilization. The ultimate goal of CR research is to establish a CR network that is either self-sufficient in delivering a multitude of wireless services or capable of assisting existing wireless networks to enhance their performance. The performance of a CR network is inevitably affected by the coexisting primary systems. Most importantly, the CR transmissions should be carefully controlled to guarantee that the primary services are not jeopardized. To better understand the ultimate performance limits and potential applications of CR networks, it is crucial to study the CR network capacity to provide theoretical insights into the CR network design.
