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Femtocells equipped with cognitive capabilities are able to efficiently utilise the empty spaces of macrocell spectrum. This makes it possible to enhance the spectral efficiency of the available spectrum for end users. In a two-tier macro-femtocell network, `extra' macrocell resources need to be carefully and efficiently utilised by the femto-tier network, without having any negative impact on the performance of an existing macrocell network. Hence to attain self-configurable features in femtocell networks, this research proposes adaptive approaches through which femtocells can manage their coverage by controlling the transmission power to improve the network performance while alleviating the cross-tier interference. Since the interference problem is a very serious issue in the deployment of closed access mode compared with open access mode, the authors propose a mode selection mechanism that enables femtocells to automatically configure their modes to resolve interference issues while meeting the minimum quality-of-service requirements for their registered users. Simulation results confirm that the proposed mechanisms improve the overall capacity and spectral efficiency while reducing the outage probability.