Multitaper Spectrum Sensing of OFDMA Signals in Frequency Selective Fading Environment

This paper considers the problem of how to quickly and accurately identify spectrum holes from downlink orthogonal frequency division multiple access (OFDMA) signals in frequency selective fading environment. We assume that the subcarrier assignment of primary users (PUs) in an OFDMA system is {\it a priori} known to the detector. Under this assumption, we formulate the original problem as the problem of detecting presence/absence of PUs, which requires less computational complexity than its original counterpart. We propose a spectrum sensing algorithm to detect presence/absence of a PU. In the proposed algorithm, we first apply the Thomson's multitaper spectrum estimation (MTSE) method to obtain spectral estimates at certain subcarriers of interest, and then we perform a simple threshold test. We present closed form results for false-alarm and miss-detection probabilities of the proposed algorithm. We study impacts of system/MTSE parameters on the detection performance via Monte Carlo simulation.