Most previous works on energy detection for spectrum sensing have assumed that the noise power in the licensed band is constant over time and known a priori. However, it is widely known that this assumption does not hold in practice. In order to deal with this issue, the author has presented an adaptive energy detection strategy which adjusts its detection threshold according to the noise power estimation and analysed its sensing performance for the case of employing a single receive antenna at the secondary user terminals. The author extend this work to the case of multiple receive antennas. Analytical results show that the proposed scheme can maintain a target false alarm rate irrespective of the noise power level. Also, they demonstrate that it can achieve a closer approximation of the performance of the energy detector with an ideal detection threshold by increasing the number of the receive antennas and/or the time bandwidth product of the noise waveform used to estimate the noise power.
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