RadioVisor: a slicing plane for radio access networks

To cope with the exponential traffic growth, increasingly diverse traffic mix including voice, video, machine-tomachine(M2M), and the spectrum shortage, wireless networks have to get densely deployed and dynamically adapt to meet the distinct requirements of diverse traffic classes. However, current network architectures are ill-equipped to support a dense and dynamic wireless infrastructure. First, since it will be impossible to obtain regularly placed cell sites for an infrastructure with higher density, basestations will be deployed wherever possible in a chaotic fashion. However, a chaotic and dense wireless deployment will be very complex to manage, since it will experience highly variable loads and unpredictable inter-cell interference among other things. Further since spectrum is limited, very likely all the basestations will be operating on the same frequency (referred to as frequency reuse factor of one). This leads to a tremendous amount of inter-cell interference, and that becomes the limiting factor for network capacity. Second, a dense infrastructure is very expensive to deploy and operate. Current deployments are unaffordable except to the largest operators, so a deployment with significantly higher density will likely be enormously expensive even for the largest operators, preventing smaller operators from expanding and offering consumers the choices they need. Rather than looking at the radio access layer as a collection of independent base stations, SoftRAN [1] proposes that all base stations deployed in a geographical area should be abstracted as a virtual big-base station which is made up of radio elements (the individual physical base stations). A logically centralized control plane makes all decisions regarding handovers and interference management, while the radio elements are simpler devices with minimal control logic. Since all neighboring base stations are allocating from a fixed set of shared resources, SoftRAN abstracts the radio resources as a 3D resource grid of space, time, and frequency slots; and program them in a software defined fashion through a logically centralized radio access control plane. Rather than having a single entity controlling radio access networks which limits sharing as standardized by 3GPP on LTE [2], we build on SoftRAN and argue that the 3D resource grid should be dynamically sliced based on traffic among virtual operators. This will enable virtual operators to innovate in scheduling, interference management and even in physical layer (PHY). Operators should be able to flexibly define slices based on subscriber attributes and application types (e.g. voice, video) to support a wide range of application requirements. Such architecture raises unique challenges compared to data-center and enterprise networks. Indeed, radio resources are inherently coupled due to the shared nature of wireless media. Unlike FlowVisor [3] which slices the flow space and easily isolates the disjoint subspaces. Slicing radio resources would need to consider interference.