Spectrum Without Bounds, Networks Without Borders

Linda Doyle, Jacek Kibilda, Timothy K. Forde, Luiz DaSilva
2014 Proceedings of the IEEE  
The purpose of this paper is to present a vision for future mobile and wireless networks. The vision, which we call Networks without Borders (NwoB), is based on a market-place of virtual network operators which construct networks from a pool of shared resources (e.g. basestations, spectrum, core network components, cloud resources, processing capabilities etc.). The resources will be sourced from traditional industry players as well as crowdsourced from individuals. The paper describes this
more » ... oach from a value-chain perspective. The proposed value-chain is substantially different from the value-chain models that are currently used to illustrate mobile and wireless networks. The economic imperatives and innovation drivers for this approach are discussed. Early work showing the promise of this vision is presented. This work focuses on diverse examples which advocate the removal of traditional and historical restrictions on spectrum and infrastructure and move towards more dynamic use of shared resources. In the first example we look at how frequency-division-duplexing (FDD) and time-divisionduplexing (TDD) restrictions on spectrum usage can be relaxed; we remove the borders between TDD and FDD. In the second example we look at the aggregation and pooling of corporate infrastructure which uses exclusive spectrum and removes the borders between different mobile operators. Finally we look at the aggregation of user-deployed or crowdsourced infrastructure that opportunistically uses spectrum and removes the borders between independently deployed hotspots. These are starting points and the full realization of the vision will involve more dynamic access to spectrum and more extensive sharing of infrastructure. Hence, the final part of the paper describes the resulting research challenges. Moving from static forms of spectrum access to more dynamic scenarios which redirect spectrum resources to where they are needed and which heavily leverage spectrum sharing coupled with the ability to compose networks from a pool of shared infrastructure can have a transformative effect on how mobile and wireless networks are owned and controlled. The purpose of this paper is to present one future vision which is predicated on this greater freedom of access to spectrum and more inclusive view of network infrastructure. Our vision, which we call Networks without Borders (NwoB), is based on a market-place of virtual network operators which construct networks from a pool of shared resources (e.g. basestations, spectrum, core network components, cloud resources, processing capabilities etc.) [1] . The resources will be sourced from traditional industry players as well as crowdsourced from individuals. The new forms of service provider will be facilitated by the virtual network operators. These operators will control virtualised slices of the physical resources aggregated from the pool to create customized virtual networks on which to offer specialised services to end-users. There will be a high level of dynamism involved; unneeded resources will be returned to the pool for redeployment by other service providers. This model broadens the definition of infrastructure provider through significantly leveraging user-deployed infrastructure in a systematic manner. This model extends the sharing economy deeper into the mobile network through extensively embracing sharing of all types of resources, especially the spectrum. The model fundamentally redefines the term mobile network operator as a highly virtualized entity using heavily shared heterogeneous resources. The idea of an over-the-top service no longer exists, as the service and virtual network over which it is delivered are interconnected, which allows for the service provider to extract value from the network while compensating the virtual operator for their services. Our proposed architecture recognizes the pressures on wireless providers to substantially increase their ability to support mobile data, while simultaneously keeping costs to customers January 9, 2014 DRAFT PROCEEDINGS OF THE IEEE 2 fairly constant, pointing to the need for a new, sustainable business model that involves major changes in the way networks are provisioned. The vision is transformative because it challenges the conventional notion that exclusive ownership of spectrum resources over large geographical areas is needed to justify large-scale investment in infrastructure in the first place, leading to subsequent tight control of both the spectrum and the infrastructure in order to recoup the investments. More fundamentally, the vision recognizes the fact that a network cannot continue to be a costly set of pipes from which value is difficult to extract. The future vision of networks is built up over the paper. The paper begins by exploring the mobile network value-chain, identifies the changes that have taken place and are taking place in that chain and discusses the economic imperatives and innovative drivers of the change. Section III draws attention to the fact that these changes do not substantially alter the structure of the value-chain. In particular section III focuses on the fact that sharing of infrastructure and of spectrum is restricted and, as a result, so are the subsequent economic gains that can be achieved. In response to this, a new value-chain is suggested and presented in section IV. This chain starts with the services. The network is composed from a pool of resources in response to this service need, encapsulating the ideas presented in the opening paragraphs of this paper. Section V goes on to detail some early work on some of the possibilities for rethinking networks as suggested and provides details of examples in which spectrum is more dynamically accessed and infrastructure is pooled. Section VI lists the outstanding challenges in the field from a technical and regulatory perspective, and lays the foundation for future research. Section VII draws conclusions. II. THE CHANGING MOBILE NETWORK VALUE-CHAIN PROCEEDINGS OF THE IEEE 4 Secondly we have seen the emergence of competitive/complementary value-chains. WiFi is a good example of this and labelled 2 in Figure 2. WiFi uses license-exempt spectrum and is a user-deployed technology which is configured to offer hotspots of connectivity. In the past number of years WiFi has moved from what was once a competing wireless infrastructure to a complementary one, playing a central role in supporting data off-loading from the mobile networks 1 . The value-chains of the mobile operator and the WiFi hotspot are becoming increasingly intertwined. Relationships exist between mobile operators and WiFi providers, and protocols such as Passbook, Hotspot 2.0 and IEEE 802.11u will make it easier to move from one wireless infrastructure to the other. There are of course value-chains that are still to fully emerge. The machine-to-machine (M2M) value-chain is still evolving. Solutions exist that build this into the value-chain of the mobile operator, and others exist to support M2M on completely separate networks. Hence, how competitive or complementary these value-chains may be is yet to be determined. Thirdly elements of the value-chain are being bypassed by new players. The emergence in the last decade of what are known as over-the-top services (e.g. Skype and WhatsApp) make use of the radio spectrum, radio access network, backhaul and core network of the mobile operator but do not contribute to operator income. In other words no service level agreements exist with the mobile operator. These services are seen as sabotaging value or extracting revenue that would otherwise be generated by the MNO from traditional voice and data services. Content and value-added services are increasingly designed, built and operated by third parties that use this mode of operation. In essence the parts of the value-chain which generate revenue are under the control of different entities than those who control the parts of the value-chain which incur great costs. This is labelled 3 in Figure 2. The increasing complexity and expense of new technologies, the increasing speed at which these new technologies emerge and are in-demand by users, the challenge in providing coverage in areas that are unlikely to generate sufficient revenue to justify heavy infrastructure investment, all have led to significant challenges in the provisioning of networking infrastructure. The loss of revenue and value to other players via over-the-top services, reducing the physical network to 1 Forecasts predicting data offloading of in excess of 60% of mobile data traffic have been made by CISCO and others. Examples of CISCO predictions can be found http://www.cisco.com/en/US/solutions/collateral/ns341/ns525/ns537/ns705/ns827/ white paper c11-520862.html. January 9, 2014 DRAFT PROCEEDINGS OF THE IEEE 5 a set of expensive pipes, compounds this further. To respond to the large costs associated with provisioning of networks we see a fourth major change occurring in the value-chain, and that is a growth in the sharing of ownership and control within the infrastructure elements of the chain (e.g. the RAN, backhaul and core network elements), i.e. the areas in which most costs are accrued. From a technical perspective, sharing is often described as either passive or active [4] . Passive sharing refers to situations in which resources are shared without the need to change the radio access network or the core network. For example the sharing of sites and masts between mobile operators has been ongoing for a long time. Active sharing usually involves some level of virtualisation which tends to have implications for the underlying architecture. Active RAN sharing, for example, refers to the sharing of the basestation between different operators. There are also options for mobile operators to share the core network. In fact 3GPP 2 has identified two architectures for network sharing. In both architectures, the radio access network (RAN) is shared. The first of these is known as the Multi-Operator Core Network (MOCN) configuration and in this case only the RAN is shared [5]. In the Gateway Core Network (GWCN) configuration, elements of the core network are also shared between operators [5]. The implementation of these configurations involves the virtualisation of the network entities so that resources can be shared among operators. Active network sharing is still in its infancy and is not widely deployed. Other architectures that are suited to sharing are also emerging as viable. One such example is the Cloud RAN [6], [7] . In this case the RAN is split between remote radio heads and baseband processing, the latter residing in the cloud. We also see sharing within the elements of the value-chain emerging in other forms. Through the rise in popularity of the femtocell 3 we also see the sharing of ownership of the basestation between the mobile operator and the customers. Many of the femtocell business models involve the customer purchasing a femtocell for their home and connecting to the core network via the customer's own fixed network (i.e. via the customer backhaul). The ownership of the RAN from both a capital expenditure (CAPEX) and operational expenditure (OPEX) perspective is
doi:10.1109/jproc.2014.2302743 fatcat:plm6rgkdqrb2llmfiuf5hcg75a