A Survey on Dynamic Spectrum Access Techniques in Cognitive Radio

Wireless networks are characterized by fixed spectrum policy. With increasing demands for wirelesscommunication efficiently using the spectrum resources has become an essential issue. Cognitive radio is aform of wireless communication which is used to sense the spectrum and find the free spectrum. It is usedby unlicensed users without causing interference to the licensed user. Cognitive radio with the dynamicspectrum access is key technology which provides the best solution by allowing a group of Secondary usersto share the radio spectrum originally allocated to the primary users. Dynamically accessing the unusedspectrum is known as dynamic spectrum access (DSA) which becomes a promising approach to increasethe efficiency of spectrum usage. In this paper, DSA models are discussed along with different methodssuch as game theory based method, a measurement-based model, network coded cognitive control channel,Markovian Queuing model, the Delay performance of threshold policies, fuzzy logic based method andspatio-temporal spectrum management model.