Spectrum is scarce and the primary users (licensed users) do not use them always. There are free spaces called spectrum holes. Spectrum is not utilised efficiently in certain bands. A technique which scans the spectrum for the given bandwidth and finds the spectrum holes so that secondary users can use them, was proposed. But for high bandwidths the sampling rates are high such that practical Analog to Digital Converters cannot achieve. Compressed sensing techniques sample at rate less than the Nyquist rate and still are able to reconstruct the original signal except that the signal should be sparse in some domain. So spectrum sensing using compressed sensing methods were proposed and found to be more efficient.
P. Avinash, Gandhiraj R., and Soman, K. P., “Spectrum sensing using compressed sensing techniques for sparse multiband signals”, International Journal of Scientific & Engineering Research, vol. 3, no. 5, pp. 1-5, 2012.