ion is a term to describe position This information is used to access databases of policies aware networking enhancement. For example, if a radio or resources to make better decisions. Dynamic exchange CHAPTER 2.4b Cognitive radio: The technologies required Boundary Location Cognitive Policy and Resources Function Engine Engine Function Where Am I? Position Inquire Region (Position) Region Decision Regarding Band to Use Inquire (Band, Region, Time) Approval CR Accesses Band Figure 2.4b-7 Spectrum access sequence diagram. A policy engine uses regional inputs to select spatially variant policies to approve or disapprove a requested spectrum access. of information may be used for other networking information may create increased spectrum access actions. The set of CR applications that are enabled by opportunities. geolocation capability is large and has many attractive One of the primary considerations for such a cognitive benefits. application is noninterference with other spectral uses. Figure 2.4b-8 shows local spectrum awareness and utili- zation. If the regulatory body is allowing CRs to utilize 2.4b.6.2 Dynamic spectrum access the unoccupied "white space," increased spectral access and spectrum awareness can be achieved. The CR can examine the signals and may extract detailed information regarding use. By esti- One of the most common capabilities of CRs is the mating the other uses and monitoring for interference, ability to intelligently utilize available spectrum based two CRs may rendezvous at an unoccupied "channel" and on awareness of actual activity. Current conservative communicate. spectrum management methods (static spectrum as- Sophisticated waveforms that have the ability to pe- signments) are limited because they reduce spatial reuse, riodically stop transmitting and listen for legacy users are preclude opportunistic utilization, and delay wireless called for in this application, as well as waveforms that communication network deployment. Without the need can adapt their spectral shape over time. D