Abstract: Spectrum sensing is one of the challenge in the hidden terminal which comes across in cognitive radio is .so has to overcome this we are proposing a optimal selection process for secondary nodes using fuzzy interface system. Using fuzzy logic rule the selection of secondary node play an important role in the enhancement of output of the cognitive radio spectrum sensing. if the node is not optimal the error rate will increase and packet transform may delay which may damage he data packet in forwarding process. So we implement energy detection system for taking decision by using the probability alarm by using fuzzy interface system we can reduce the spectrum sensing loss in forwarding the packets.
Keywords: Cognitive Radio, Fuzzy Inter face system Fuzzy Rules, SNR, Spectrum Sensing, error rate.