Though wireless communication has been one of the most acclaimed innovations, a major problem of spectrum scarcity has tampered with its efficiency as the spectrum needs have been constantly increasing. In order to combat this issue, cognitive radio is used so that efficient use of the available spectrum is made by the unlicensed user. Its main functions are sensing and analyzing. This work focuses on a new, efficient energy detection based spectrum sensing. The fast Fourier transform (FFT) of the energy detection method is replaced by Hadamard transform and Hilbert transform. Simulated results prove that there is improvement in both signal to noise ratio (SNR) and probability of detection  in this concatenated approach.

cognitive radio, concatenated spectrum sensing, Hadamard transform, Hilbert transform.