Abstract: In this paper we have discuss about overview of all existing spectrum sensing techniques and comparison is evaluated on the basis of their capacity of detecting the presence of primary users. In present day wireless communication has become the most popular communication. Cognitive radio is widely expected another field in wireless communications. Spectrum sensing allows cognitive radios to be aware of the surroundings by determining which frequencies are in use. The spectrum sensing is the focal point of CRs allowing them to detect vacant spectrum holes and use them without harmful interference to other CRs or licensed users.

Keywords: Cognitive Radio, Spectrum Sensing Techniques, Sensing Performance, Non-cooperative System.