Development of a Mathematical Framework for Comparison of Underlay and Overlay Systems

Overlay and underlayare two main spectrum access strategies in cognitive radio.In this work, wehave driven closed form expressions for the primary service outage probabilitiesof both techniques. We have also formulated and solved optimization problems with the objective of maximizing the secondary service’s capacity with constraints on primary service’s outage probability and secondary service power budget. A mathematical frame work for comparing the performance of the two systems has been developed. The performances of the two systems havebeen compared against different levels of primary service interference, activity, and secondary service power budget levels, and the strengths of each system has been clarified.