communications (MTC) and many different coexisting network and service operators. Therefore, 5G must support convergence over traditionally separated network domains and offer greater granularity and flexibility in control signalling and in data transmission. Correspondingly, the architecture is expected to be much more complex than before, in the sense that different network entities, such as relays, small cell base stations (SBSs), massive machines and data centers/cloud, etc, will be widely deployed with ultra densificantion and taken as close as possible to the end-users. Along with the rapid development of hardware computing units, the BS in wireless networks is expected to be deployed with powerful computing units or data centers to enable the software defined networking (SDN) and accommodated to the diverse service requirements. These changes, however, not only can enable the boost of data rates, but also bring many nontrivial challenges on how to achieve a super-efficient operation from network management point-of-view [@Liang].

In this light, network function virtualization (NFV) is envisioned as one powerful tool to address these aforementioned problems in wireless networks. In the resulted wireless network virtualization (WNV), network infrastructures and functionalities are decoupled from the services that they provide to maximize their utilization, where the differentiated services 