I. Introduction
With the densification of heterogeneous wireless-capable devices and the rapid and continuous increase in data traffic volumes in wireless networks [1], spectrum sharing techniques are essential for mitigating mutual interference between co-located, co-channel wireless devices, thereby enabling concurrent operation of multiple devices. It follows that, in practice, the technical design of spectrum sharing techniques for a given technology depends on three major aspects: (i) the technologies implemented by the other devices, where interference is to be managed either between devices of the same technology (i.e. intra-technology coexistence), or of different technologies (i.e. inter-technology coexistence); (ii) the management of the devices, where interference may be managed with various levels of coordination (i.e. intra-and inter-operator coexistence), or in a fully distributed manner (for individually deployed devices); and (iii) the management of the spectrum, spanning a continuum of access models, from exclusive use of spectrum (i.e. exclusive spectrum access rights for a single operator/technology) to a spectrum commons (i.e. equal spectrum access rights for all users/operators/technologies) [2].