The radio frequency is a limited natural resource and getting enabled day by day due to growing demand of the wireless communication applications. To operate on a specific frequency band, license are needed. The use of radio spectrum in each country is governed by the corresponding government agencies. In conventional technique each user is assigned a license to operate in a certain frequency band. Most of the time spectrum remains unused. The allocated spectrum is not utilized properly; it varies with time, frequency and geographical locations. Thus to overcome the spectrum scarcity and unutilized frequency band, a new communication technique cognitive radio (CR) and dynamic spectrum access (DSA) are introduced. CR network provides efficient utilization of the radio spectrum and highly reliable communication to users whenever and wherever needed. DSA technology allows unlicensed secondary system to share the spectrum with licensed primary system. In this thesis, dynamic spectrum access techniques are discussed and few methods of spectrum management, power management are proposed and presented.