This paper deals with spectrum sensing in an orthogonal frequency division multiplexing (OFDM) context, allowing an\nopportunistic user to detect a vacant spectrum resource in a licensed band. The proposed method is based on an iterative algorithm\nused for the joint estimation of noise variance and frequency selective channel. It can be seen as a second-order detector, since it is\nperformed by means of the minimum mean square error criterion.Themain advantage of the proposed algorithm is its capability to\nperformspectrumsensing, noise variance estimation, and channel estimation in the presence of a signal. Furthermore, the sensing\nduration is limited to only one OFDMsymbol.We theoretically show the convergence of the algorithm, and we derive its analytical\ndetection and false alarm probabilities. Furthermore, we show that the detector is very efficient, even for low SNR values, and is\nrobust against a channel uncertainty.
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