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Optimal Soft Combination and Cooperative Sensing in Distributed Antenna Systems

Cooperative sensing based on energy detection in distributed antenna systems is considered in this letter. We investigate soft combination of the observed energies from different cognitive radio users. Based on the Neyman-Pearson criterion, an optimal soft combination scheme which can maximize the detection probability for the constant false alarm rate is obtained. Closed-form expressions for the detection probability and false alarm rate for the optimal soft combination scheme are derived. Finally, through numerical results the improvement in cooperative sensing schemes with the optimal soft combination is shown.