Abstract:

Abstract： Spectrum sensing based on the cyclicfeature detection is a key technique in cognitive radio. The cyclic-feature in the spectrum of signals is fundamental to the detection. Using the theory of cyclic spectrum of signals, this paper investigates cyclic-feature in the spectrum of a signal which suffers from fading and Doppler shift. Simulation results show that the cyclic spectrum of a fading and frequencyshifted signal is quite different from that of the corresponding ideal signal. The amplitude and phase of the cyclic spectrum are changed significantly, but the frequency is the same as the ideal signal. Doppler shift broadens the signal spectrum and shifts the cycle frequency, and new spectral components occur at noncycle frequencies. This phenomenon is important in spectrum sensing and signal detection based on the cyclicfeature detection.

Key words: cognitive radio; spectrum sensing; multipath fading; Doppler shift