7.5 Spectrum Sensing

Spectrum sensing is the only area of radio communications where we understand how to couple communications with CRs. We have a long ways to go before we can develop deployable cognitive engines.7 The FCC definition of a CR is mainly geared toward the autonomous exploitation of local unused spectrum to provide new paths for spectrum access.

In order for a CR to measure, sense, learn, and adapt, it must be aware of the parameters related to the radio channel characteristics. The radio must also know the availability of spectrum and the level of power it can emit over that specific spectrum. One can argue that spectrum sensing is the most important aspect of CR functionality since it provides the radio with awareness regarding the local spectrum usage and information on how the spectrum is being utilized by primary users. Spectrum awareness can be achieved through the usage of geo-location information, beacons, and/or sensing by CRs. With beacons, the transmitted information can include occupancy of a spectrum and other channel quality features. This section of the chapter addresses spectrum sensing performed by the CR for the purpose of obtaining spectrum usage characteristics covering time, space, and frequency bands. A CR will also learn the types of signals occupying the spectrum, including modulation techniques, waveforms, bandwidth, carrier frequency, and so on. This type of sensing requires advanced signal analysis techniques with high computational complexity. ...

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