Two Stage Cooperative Spectrum Sensing for Interweave Cognitive Radio with SNR Enhancement by Using Signal Transformation Over AWGN Channel

Abstract

Spectrum Underutilization, along with the growing issue of spectrum scarcity, has promoted a reassessment of how the radio frequency spectrum is used. Cognitive Radio technology comes as a solution which enhance the utilization of spectrum with systematic use of the scarce resource by Opportunistic Spectrum Access. One of the important functions of cognitive radio is Spectrum Sensing which enable cognitive radio to detect spectral opportunity also called White Space or Spectrum Whole. Among many spectrum sensing algorithms available, Energy Detector(ED) is preferred since it doesn?�?t need the prior information about primary user?�?s signals and having low computational complexity. However, the performance of ED is directly proportional to signal to noise ratio(SNR) which leads to poor performance at the low SNR regime. In order to alleviate the detection problem at low SNR, Discrete Wavelet Transform(DWT) based denoising of the primary user signal is applied in the front end of ED. The effect of denoising prior to ED is analysed by employing six different wavelets as Haar, Daubechies, Bi Orthogonal Splines, Reverse Bi Orthogonal, Coiflet, Fejer-Korovkin and the performance metrics of ED is analysed using single stage wavelet denoising based ED. Based on the best performing wavelet, Two Stage Spectrum Sensing is developed which composed of CED as a first stage and Denoising based ED as a second stage which consist of wavelet denoising prior to ED that will perform signal to noise ratio enhancement. The detection performance of proposed Two Stage Spectrum Sensing approach is compared against ED alone and Single Stage wavelet based ED in terms of different performance metrics given as probability of detection, probability of miss detection, Receiver operating Characteristic a