Abstract: Abstract: Now a days, WSN face the problem of spectrumunderutilization, cognitive radio is one of the technique whichused for solving these problem in WSN. It can be achieve byopportunistically exploiting portions of the spectrum temporarilyby vacating licensed primary users. First we focus on how CRSNsare different from other wireless networks and then list out thenumber of challenges and main issue of routing in Cognitive Radio Networks (CRNs). In WSN, Multimedia applications arerepresented as delay sensitive and high bandwidth stipulatingtraffic sources. Other auxiliary multimedia applications based on Cognitive Radio Sensor Networks (CRSNs) with energy and spectrum constraints is a highly derivative task. In the existingsystem the users which are close to the cluster heads (cell centerusers) have higher frequency range than the users which are farfrom the cluster head (cell edge users). So cell center users get maximum resources and cell edge users get limited resources.We propose an algorithm in which we calculate a weighted SNRvalue for each user and based on that value cluster head assignsresources to the users.

Keywords:  Energy Spectrum Rank, Cluster head, SNRPRB, CRSN.