We provide a theoretical analysis of the capacity achievable by an open/closed-access cognitive radio system, where the system uses spectrum resources primarily allocated to a macro cellular system. For spectrum sharing, we consider two methods based on listen-before-talk and adaptive transmit power control principles. Moreover, outdoor and indoor installations of CRS stations are investigated. We have also taken the effect of antenna heights into consideration. Numerical results reveal the capacities possible from CRS base stations installed within the coverage area of the macro cell system. We show numerical examples that compare the capacities achievable by open-access and closed access cognitive radio systems.