before its widespread deployment, including control signalling, virtual resource allocation, network management, and some non-technical issues such as business model, etc. Due to the inherent random and broadcast natures of wireless networks, these challenges need to be tackled carefully and broadly by comprehensive research efforts and call for a complete re-design of capabilities, architectures, interfaces, functions, access and non-access protocols of network services.

In this article, WNV is first briefly reviewed. Then by summarizing some existed work, we discuss the XaaS taxonomy, briefly present some definitions in XaaS and also introduce some key enabling technologies towards the mature XaaS framework. Challenges and research opportunities in these areas are also discussed. This article, we hope, can attract interests from the research and industrial communities on this emerging interdisciplinary field, which is able to boost up the development of the future 5G network infrastructure.

Wireless Network Virtualization in 5G
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![An example of wireless network virtualization[]{data-label="fig:example1"}](wnv2.jpg){height="8cm" width="10cm"}

Virtualization have recently moved from traditional server virtualization to wireless network virtualization. In stead of virtualizing the computing resources in server virtualization, in WNV, physical resources need to be abstracted to isolated virtual resources from the infrastructure service providers (InSPs). Then, the virtual resources can 