We consider a network that comprises a group of K users, equipped with single-antenna terminals, who want to selfishly maximize their individual transmission rates and S single-antenna base stations. The information rates and the transmit power levels of the users are not dictated by the base stations. In this context we introduce the problem of decentralized handovers: each terminal is equipped with a cognitive radio used to sense the quality of its links with the different base stations and share, in a smart way, its transmit power among them. In the hard handover case, for which there is a unique stable Nash equilibrium, we determine the selfish repartition of the users between the base stations and then we assess its social efficiency, which is measured in terms of sum-rate. In the soft handover case, the problem consists in determining the optimum selfish power allocation for each user and analyzing its sum-rate efficiency with respect to the equivalent virtual K £ S multiple input multiple output (MIMO) network. We also show how to extend the provided results to the case of multi-antenna terminals and base stations and provide simulations to illustrate the presented results.