ery low level are all availa- channel or may be used to access locally unoccupied ble for a CR developer to utilize in creating new capa- spectrum. Non-interference is particularly important, bilities. Finally, middleware technology enables greater and protocols for sensing, deciding, and accessing spec- software reuse, which makes CR development trum are being designed, developed, and demonstrated economical. today. Modern regulatory philosophy is starting to allow CR Increased robustness in biometric sensor technology to deploy new services and capabilities. As the trend provides a whole new dimension to CR applications. The continues, there are economic motivations for deploying most likely initial use of this technology is in user CR systems. authentication applications, such as the purchasing of Section 2.4b.6 covered research in CR technologies, services and products. and presented three significant classes of CR applica- Knowledge of time has been available in many forms, tions. Geolocation-enabled applications and authentica- but integration into a broader range of full-function tion applications were discussed in some detail. The most capabilities will enable all new applications. Stable time promising CR application is dynamic spectrum access. knowledge enables a CR to plan and execute with more Suggestions for using OFDM waveforms along with dy- precision. Using this capability for non-infrastructure- namic bit loading are included in this chapter. Solutions based geolocation, dynamic spectrum access, or AI plan- to the rendezvous problem are suggested, and the hidden ning is envisioned for near-term CR functions. node problem is described. A smart agent model of CRs is attractive. An agent is Section 2.4b.7 covered the timeline in which these an entity that perceives and acts on behalf of another. technologies will roll out and be integrated into radio This is where CRs are going. Smart agent models of the equipment and products. Many of the technologies re- world enable a radio to provide services fo