NSPs and InSPs can be established and the requirements of the NSPs for resources can be expressed to the InSPs. In addition, in the XaaS framwork, virtualization can happen among the InSPs as well. To facilitate the interaction among the InSPs, a standard protocol to express information-sharing and negotiation-handling are also necessary. Thus, proper control signalling considering delays and reliability needs to be explored in a careful manner to enable the connectivity among different parties involved in wireless virtualization. Moreover, NSPs or end-users may have different QoS demands. Therefore, when designing the control signalling and other overhead involved, the diversity of requirements from different parties should be carefully treated.

Virtual Resource Allocation
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In order to realize the XaaS in the WNV, InSPs or NSPs should discover the available resources in the physical substrate wireless networks. InSPs need to decide what physical resources can be used for virtualization and NSPs can decide what resource to choose based on the end-users’ demands. Since resources will be shared among multiple parties, an efficient resource coordination scheme and interaction model should be investigated. Moreover, the slicing, isolation, customization and allocation schemes are necessary in this case, as different resources needs to be sliced 