In this paper we focus on spectrum sensing in cognitive radio to sense the presence of primary user and effectively use the available radio bandwidth. Cognitive users are allowed to share the licensed spectrum allotted to the primary user, when kept unutilized by it. Here energy detection technique is usedfor spectrum sensing overthe Rayleigh fading channel.Multiple cognitive radios actively participate to enhance the sensing capability of channel by collecting all sensed data at one central place. This collected data is processedand decision is made for the availability of spectrum, and thus can overcome the flaws of individual sensing. Comparison of cooperative and non-cooperative spectrum sensing for same number of cognitive radios is carried out under the centralized fusion procedure.
