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A noise suppression technique using overlapped FFT for carrier sensing of cognitive radio is proposed. The energy detection method is modified. A broadband signal is FFTed and the averaged power of each bin throughout the carrier-sensing period is calculated and judged against a threshold. At the process, adjacent FFT frames are overlapped greatly but with sufficiently large interval compared to the sample-by-sample sliding window. As a result, the averaging effect of noise increases and False Alarm (FA) and MisDetection (MD) probabilities are improved with much smaller computation amount than the sample-by-sample sliding window case. Simulations on FA and MD probabilities are performed and the effectiveness is confirmed. A model to explain the phenomenon using oversampling was introduced.
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