Although the radio access network (RAN) part of mobile networks offers a significant opportunity for benefiting from the use of SDN ideas, this opportunity is largely untapped due to the lack of a software-defined RAN (SD-RAN) platform. We fill this void with FlexRAN, a flexible and programmable SD-RAN platform that separates the RAN control and data planes through a new, custom-tailored southbound API. Aided by virtualized control functions and control delegation features, FlexRAN provides a flexible control plane designed with support for real-time RAN control applications, flexibility to realize various degrees of coordination among RAN infrastructure entities, and programmability to adapt control over time and easier evolution to the future following SDN/NFV principles. We implement FlexRAN as an extension to a modified version of the OpenAirInterface LTE platform, with evaluation results indicating the feasibility of using FlexRAN under the stringent time constraints posed by the RAN. To demonstrate the effectiveness of FlexRAN as an SD-RAN platform and highlight its applicability for a diverse set of use cases, we present three network services deployed over FlexRAN focusing on interference management, mobile edge computing and RAN sharing.

Spectrum is a limited resource (especially below 6 GHz where most mobile and wireless systems currently operate) and optimizing its use is the target of national regulators in order to provide and deliver maximum benefit and services to the citizens. We present the UK perspective on the future wireless spectrum below 6 GHz, including plans and strategy of Ofcom (the UK telecommunications regulator) to make more spectrum available for wireless and mobile services. We identify capacity (especially indoors), coverage, machine-to-machine (M2M) and wireless backhaul as four major drivers that are expected to influence spectrum regulation in the coming future, and discuss the spectrum bands under consideration with respect to each. We then examine the amount and nature of future spectrum below 6 GHz. We find that, unlike currently allocated spectrum, most of the new spectrum (close to 80%) would be shared spectrum and it will be accessed via either licensed shared access (LSA) or opportunistic spectrum access (OSA) models. We outline a trend indicating that hybrid geolocation database plus sensing will be a dominant and more generally applicable spectrum access technique in the future when dealing with shared spectrum bands with incumbents not in the wireless services sector. On the other hand, some form of beacon signaling can enable efficient spectrum sharing among heterogeneous wireless systems assuming such signaling can be incorporated in a cost-effective manner. Finally we discuss 5G requirements under consideration and potential spectrum below 6 GHz to meet those requirements.

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Mobile phones and innovative data oriented mobile services have the potential to bridge the digital divide in Internet access and have transformative developmental impact. However as things stand currently, economics come in the way for traditional mobile operators to reach out and provide high-end services to under-served regions. We propose a do-it-yourself (DIY) model for deploying mobile networks in such regions that is in the spirit of earlier community cellular networks but aimed at provisioning high-end (4G and beyond) mobile services. Our proposed model captures and incorporates some of the key trends underlying 5G mobile networks and look to expand their scope beyond urban areas to reach all by empowering small-scale local operators and communities to build and operate modern mobile networks themselves. We showcase a particular instance of the proposed deployment model through a trial deployment in rural UK to demonstrate its practical feasibility.

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