Recent years have witnessed an increasing diversity of network services and novel applications, which are subject to a wide spectrum of service requirements with respect to bandwidth, throughput, and latency. Energy-efficiency of networks and systems becomes a dramatically growing concern, due to both increasing energy cost and CO2 emission. 5G mobile networks are being recognised as the next-generation Internet to meet the varying needs of diversified services and to reduce the carbon emissions of telecom infrastructure and data centres. In contrast to the network functions built with dedicated equipment in the current network, network elements in 5G mobile networks are provided as Virtual Network Functions (VNF, software implementations of network functions), which are elastically orchestrated in the form of Service Function Chains (SFC) to meet dynamic service demands and energy-efficiency goals.

The SFC orchestration can be performed in two steps: (i) VNF chaining, to define the order in which network functions are connected to form an SFC; (ii) SFC placement, to define how the SFC is embedded into the physical network. The essential features in 5G, such as cross-domain differentiated service and network dynamicity and uncertainty, have made traditional chaining methods and placement models inapplicable for 5G mobile services. Therefore, significant efforts have been devoted to tackling the research challenges of SFC orchestration.

Existing studies have primarily leveraged obvious mutual VNF dependencies to perform VNF chaining. However, such a method cannot determine the global ordering for all involved VNFs of an end-to-end 5G service. Furthermore, it narrows the channel to create SFCs with the aim of optimising the differentiated services and energy-efficiency when being instantiated in a physical network. In addition, SFC placement has been considered as a deterministic scheduling problem with the complete service and network information known as a priori. However, when applied to 5G mobile networks, additional challenges are presented in that network resource and service requirements vary at runtime due to the factors of e.g. time-varying user mobility and dynamic network management. Until now, an energy-efficient SFC orchestration in 5G mobile networks, considering both optimal VNF chaining and dynamic service demands and substrate resource capacities, has not been reported in the existing literature.

This project will investigate VNF chaining and SFC placement in order to achieve energy-efficient and proactive SFC orchestration in the context of 5G mobile networks. To tackle this challenging problem progressively, our work will be focused on three major objectives: 1) propose a uniform VNF chaining framework, that can integrate VNF dependencies, differentiated service policies, and energy-efficiency objectives, to efficiently construct SFCs; 2) develop a proactive model, considering future network and service variations at the initialisation of SFC placement, to perform practical service deployment in 5G mobile networks; 3) propose a real-time deterministic model to perform SFC placement for unforeseen variations with the aim of minimising the negative effects on network performance due to service demand violations. The insights into the energy-efficient VNF chaining framework obtained in Objective 1 will be fed into the SFC placement models in Objective 2 and Objective 3. The research proposed in this project is the first of its kind on the energy-efficient SFC orchestration in 5G mobile networks. In the long-term aim, the implications of this research will contribute to 5G service orchestration in both theoretical and practical sides and pave the way for future green 5G mobile networks.

Potential Impact:
Economic Impact
This project makes a significant contribution to the proactive and green service deployment in 5G mobile networks, by addressing two main research challenges: service function chaining and placement. Research outcomes will contribute to the UK leadership in 5G, which plays a key role in defining industry standards to support an estimated 5 to 6% of UK GDP per annum indicated by a recent UK Government report. In addition, research outcomes will have wider impact by contributing to the Internet service providers, mobile network/service operators, content providers, and Internet services and applications, through providing necessary mechanisms to satisfy dynamic user demands and time-varying substrate network resources in an energy-efficient manner. This will open up new business models for network operators and widen the market for service providers.

Mobile Internet Users
Mobile users are increasingly expected to receive content with high Quality-of-Experience (QoE). 5G mobile network is expected to provide excellent QoE for mobile Internet users, by realising swift, flexible, scalable, and differentiated service deployment. The proposed research is vital and investigates necessary components on achieving these goals. Research outcomes can help bring 5G-enabled service deployment closer to practice, which will ultimately offer mobile users best QoE in an energy-efficient way by minimising the service response time and optimising the network resource utilisation.

Mobile Network/Service Operators
Scenarios for example online service deployment with uncertain service demands, addressed by this project are not considered by today's network due to enormously high cost of conventional solutions. One of the main objectives of this project is to propose solutions for such scenarios that are commercially viable and academically challenging. The market for mobile network/service operators will thus naturally expand. Energy-efficiency is a growing concern due to both increasing energy costs and CO2 emissions. Due to explosive growth of emerging and diverse mobile services, it would be desirable to adopt dynamic and proactive orchestration approaches to reduce energy consumption, which is the general research theme of this project. Hence, the project outcome facilitates more sustainable ICT in UK.

Internet Industries
The exponential growth of mobile traffic poses a significant challenge because the Internet was designed to accommodate static service deployment, which impacts every part of the Internet ecosystem. The whole Internet industry needs novel and economical ways to solve these problems. A possible solution to provide dynamic service deployment is to develop flexible 5G mobile networks. In moving to 5G, Internet industries will find themselves at an advantage with the outcomes of this research, in terms of low energy consumption, high QoE, and proactive service deployment, which will undoubtedly enhance their competitiveness and profitability.

Public Impact
To facilitate the understanding of this scientific technologies by public, this project will deliver the public impact through Exeter's public engagement and outreach programmes, such as School Visits, and through science fairs, such as The Big Bang Fair. In addition, a version of the project website will be maintained using plain English and animations to facilitate public understanding and engage public participation.

Education and Training
University of Exeter aims to constantly enhance its teaching quality by introducing new research findings and applied technologies into the curriculum. The outcomes of this research are highly relevant to the Computer Science programme. The project endeavours to enhance the knowledge and skill base of the UK through training and developing researchers. The PDRA employed on the project will receive valuable training in this highly marketable sector, which is useful for future career advancement.