ABSTRACT
Contents 11.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 280 11.2 Characteristics of Cognitive Radio Networks . . . . . . . . . . . . . . . . . . . . . . 281 11.3 Routing Protocols for Cognitive Radio Networks . . . . . . . . . . . . . . . . . 284
11.3.1 Major Challenges . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 284 11.3.2 Overview of Existing Routing Protocols
for CR Networks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 285 11.3.2.1 Collaborative Spectrum Selection
and Routing Protocol . . . . . . . . . . . . . . . . . . . . . . . . . . . 285 11.3.2.2 Collaborative Routing Protocol Based on
Layered Graph Model . . . . . . . . . . . . . . . . . . . . . . . . . . 286 11.3.2.3 Spectrum-Aware Routing Protocol . . . . . . . . . . . . . 287 11.3.2.4 Control-Channel-Based Routing Protocol. . . . . . 288
11.3.3 Open Research Issues. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 289 11.4 Transport Layer Protocols for Cognitive Radio Networks . . . . . . . . 290
11.4.1 Challenges and Issues. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 290 11.4.2 Performance Study of TCP in CR Networks . . . . . . . . . . . . . . 291
11.4.2.1 Service Interruption Loss in Overlay CR Networks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 291
11.4.2.2 Performance Results . . . . . . . . . . . . . . . . . . . . . . . . . . . . 291 11.5 Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 294 Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 295 References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 295
11.1 Introduction Radio frequency (RF) spectrum is a critical resource for many services that people across the world rely on for their safety, communications, employment, and entertainment.1 The current static spectrum management policy allocates dedicated frequency bands to specific wireless services. The RF spectrum thus allocated can be vastly underutilized, a fact confirmed by the spectrum measurements in the major cities of America. The US Federal Communications Commission (FCC) found that spectrum access is an even more significant problem2,3 than physical scarcity of RF spectrum, largely due to the current spectrum allocation policy that limits the ability of users with immediate needs to access available RF spectrum that has already been allocated to another user or service, even though the latter does not have an immediate need to use the spectrum.
