Spectrum Sensing in Cognitive Radios Based on Multiple Cyclic Frequencies
Cognitive radios sense the radio spectrum in order to find unused frequency bands and use them in an agile manner. Transmission by the primary user must be detected reliably even in the low Signal-to-Noise Ratio (SNR) regime and in the face of shadowing and fading. Communication signals are typically cyclo-stationary, and have many periodic statistical properties related to the symbol rate, the coding and modulation schemes as well as the guard periods, for example. These properties can be exploited in designing a detector, and for distinguishing between the primary and secondary users' signals.