Cognitive radio

Cognitive radio (CR) is a form of wireless communication in which a transceiver can autonomously identify the communication channels that are in use and those that are not. Subsequently, the transceiver moves into unoccupied channels, while avoiding those being used. This functionality optimizes usage of the available radio frequency (RF) spectrum.

Cognitive radio can bypass and reduce congestion in the radio spectrum. Its users are unlicensed users who utilize unused licensed spectrum without causing interference to those who are licensed. The techniques used in cognitive radio include spectrum sensing, spectrum database, and pilot channel. These techniques can be complex and require high computational power to detect unused spectrum or fail to take advantage of spectrum space created in real time. The process of spectrum allocation normally involves licensing, although many parts of licensed spectrum are not optimally utilized. The image below shows spectral inefficiency where certain spectrum bands are congested, while other bands are underutilized.

Spectral inefficiency illustration

Spectrum sensing is a technique that uses CR devices to track all the spectrum bands located in a neighborhood to identify its various primary users and spectrum holes. Primary users are the group of users licensed to occupy a particular spectrum band. Spectrum holes constitute the space in a spectrum band that can be used by unlicensed users. Spectrum holes are created and removed dynamically in real time.

The Federal Communications Commission (FCC) put forward a spectrum database concept to circumvent the complexity of the spectrum sensing technique and to utilize TV white space. As part of this process, all TV stations are required to update their usage for every upcoming week in a database hosted by the FCC, from which CR devices can seek free spectrum information. This can negate the need for complex and costly spectrum sensing.