Date Added: Mar 2010
A cooperative approach to the sensing task of wireless Cognitive Radio (CR) networks is introduced based on a basis expansion model of the Power Spectral Density (PSD) map in space and frequency. Joint estimation of the model parameters enables identification of the (un) used frequency bands at arbitrary locations, and thus facilitates spatial frequency reuse. The novel scheme capitalizes on two forms of sparsity: the first one introduced by the narrow-band nature of transmit-PSDs relative to the broad swaths of usable spectrum; and the second one emerging from sparsely located active radios in the operational space. An estimator of the model coefficients is developed based on the Lasso algorithm to exploit these forms of sparsity and reveal the unknown positions of transmitting CRs.