Background and Objective: Reliable high-speed data communication that supports multimedia application for both indoor and outdoor mobile users is a fundamental requirement for next generation wireless networks and requires a dense deployment of physically coexisting network architectures. Due to the limited spectrum availability, a novel interference-aware spectrum sharing concept is introduced where networks that suffer from congested spectrums (secondary-networks) are allowed to share the spectrum with other networks with available spectrum (primary-networks) under the condition that limited interference occurs to primary networks. The main objective is the development of multiuser access schemes for spectrum sharing systems whereby secondary users that are randomly positioned over the coverage area are allowed to share the spectrum with primary users under the condition that the interference observed at the primary receiver is below a predetermined threshold. Methods: Two scheduling schemes are proposed for selecting a user among those that satisfy the interference constraint and achieve an acceptable signal-to-noise ratio level. The first scheme selects the user that reports the best channel quality while the second is based on the concept of switched diversity where the base station scans the users in a sequential manner until an acceptable user is found. The proposed schemes operate under two power-adaptive settings that are based on the amount of interference available at the secondary transmitter. In the On/Off power setting, users transmit based on whether the interference constraint is met or not, while in the full power adaptive setting, users vary their transmission power to satisfy the interference constraint. Results: Monte Carlo simulations were used to verify the analytical results for the multiuser secondary system in terms of average spectral efficiency, system delay, and feedback. Conclusion: It is shown that scheduling users based on highest channel quality increases the average spectral efficiency, but is associated with a high feedback load. However, the switched scheduling scheme significantly decreased the feedback load but at the expense of a lower average spectral efficiency. Furthermore, it is shown that transmit power techniques increase the performance of spectrum sharing systems in terms of ASE as well as decrease system delay and feedback.


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