Blindly combined energy detection for spectrum sensing in cognitive radio

Abstract—In this letter, a method is proposed to optimally com-bine the received signal samples in space and time based on the principle of maximizing the signal-to-noise ratio (SNR). After the combining, energy detection (ED) is used. However, optimal com-bining needs information of the source signal and channel, which is usually unknown. To overcome this difficulty, a method is proposed to blindly combine the signal samples. Similar to energy detection, blindly combined energy detection (BCED) does not need any in-formation of the source signal and the channel a priori. BCED can be much better than ED for highly correlated signals, and most im-portantly, it does not need noise power estimation and overcomes ED’s susceptibility to noise uncertainty. Also, perfect synchroniza-tion is not required. Simulations based on wireless microphone sig-nals and randomly generated signals are presented to verify the methods. Index Terms—Cognitive radio, sensing algorithm, signal detec-tion, spectrum sensing. I