Novel two-stage spectrum sensing for energy detection with FFT

A cognitive radio system coexisting with various systems must perform a spectrum sensing for finding a white space (WS). In this paper, we propose a new two-stage spectrum sensing method using an energy detection (ED) based on fast Fourier transform (FFT). In the case that an unknown signal is present the FFT band, false signals are detected in the surrounding FFT bins of the received signal due to a spectral leakage. Whereas a windowed FFT is well known as the solution of the spectral leakage, the spectrum spread to out of the original signal frequency is detected. The shape of the spectrum depends on the kinds of the window function. Therefore we improve the detection performance of ED by employing the property of the windowing in the second stage of the proposed spectrum sensing method. The cognitive node can obtain the chance of the wireless communication because WS can be detected with low false alarm probability by the proposed method.