The emergence of two new technologies, namely Software Defined Networking (SDN) and Network Function Virtualization (NFV) have radically changed the development of network functions and the evolution of network architectures. These two technologies bring to mobile operators the promises of reducing costs, enhancing network flexibility and scalability, and shortening the time-to-market of new applications and services. With the advent of SDN and NFV and their offered benefits, the mobile operators are gradually changing the way how they architect their mobile networks to cope with ever-increasing growth of data traffic, massive number of new devices and network accesses, and to pave the way towards the upcoming fifth generation (5G) networking. This paper aims at providing a comprehensive survey of state-of-the-art research work, which leverages SDN and NFV into the most recent mobile packet core network architecture, Evolved Packet Core (EPC). The research work is categorized into smaller groups according to a proposed four-dimensional taxonomy reflecting the (1) architectural ap- proach, (2) technology adoption, (3) functional implementation, and (4) deployment strategy. Thereafter, the research work is exhaustively compared based on the proposed taxonomy and some added attributes and criteria. Finally, the paper identifies and discusses some major challenges and open issues such as scalability and reliability, optimal resource scheduling and allocation, management and orchestration, network sharing and slicing that raise from the taxonomy and comparison tables that need to be further investigated and explored. 

The current mobile packet core network is evolving to cope with the pressure of the mobile traffic explosion and the advent of new services. Software-defined networking (SDN) is currently being adopted as one of the promising drivers for redesigning the mobile packet core network toward a 5G network. SDN-based mobile packet core approaches are expected to deliver features, such as fast service deployment, flexibility, and capital expenditure and operational expenditure reduction within future 5G networks. However, current SDN-based mobile packet core approaches only focus on providing unicast services without considering multicast and broadcast services. In this article, we propose an efficient SDN-based mobile packet core network architecture for supporting multicast and broadcast services. The proposed architecture takes advantage of the SDN paradigm and enables multicast and broadcast service deployment. In addition, a new SDN-based multicast subscription procedure is introduced to reduce network bandwidth resources. By numerical analysis, our scheme improves the current multicast and broadcast solution in terms of signaling cost.

For many years, the continuous proliferation of mobile devices and their applications generate a surge of signaling traffic in the control plane of the mobile packet core network. As a consequence, the control plane will potentially become a bottleneck if not properly managed. We focus on the load balancing of a virtualized and distributed Mobility Management Entity (vMME), which is the key control plane element in the 4G and 5G non-standalone cores. Most of existing works use the simple and static load balancing approaches such as roundrobin and consistent hashing, which do not work well in a heterogeneous environment. In this paper, we developed three adaptive algorithms in which the balancing decision takes into account the dynamics of the system such as the vMME load, the completion time of a request served by a vMME, and the number of pending requests queued at a vMME. The evaluation of our three proposed load-balancing algorithms in an Open5GCore testbed suggests that the latency-aware scheme helps shorten the completion time of the signaling requests by up to five times the static and dynamic schemes in those cases the link delay between the load balancer and the vMMEs differ significantly.

In this paper, we aim at tackling the scalability problem of the Mobility Management Entity (MME), which plays a crucial role of handling control plane traffic in the current 4G Evolved Packet Core as well as the next generation mobile core, 5G. One of the solutions to this problem is to virtualize the MME by applying Network Function Virtualization principles and then deploy it as a cluster of multiple virtual MME instances (vMMEs) with a front-end load balancer. Although several designs have been proposed, most of them assume the use of simple algorithms such as random and round-robin to balance the incoming traffic without any performance assessment. To this end, we implemented a weighted round robin algorithm which takes into account the heterogeneity of resources such as the capacity of vMMEs. We compare this algorithm with a random and a round-robin algorithm under two different system settings. Experimental results suggest that carefully selected load balancing algorithms can significantly reduce the control plane latency as compared to simple random or round-robin schemes.

Protection and automation in a smart grid environment often have stringent real-time communication requirements between devices within a substation, as well as between distantly located substations. The Generic Object Oriented Substation Event (GOOSE) protocol has been proposed to achieve this goal as it allows to transfer time-critical information within a few milliseconds. However, the transmission of GOOSE messages is often limited to a small Local Area Network (LAN). An earlier work has proposed to use the fifth generation of mobile networks (5G) as a means to transport IP-based GOOSE messages in a large-scale smart grid environment. On the basis of this work, this paper designs and implements an alternative solution for Ethernet-based GOOSE communication over a virtualized 5G core network that does not require any modification of the existing network protocol stack and thus is much easier to deploy. Our experimental results show that the delay introduced by the core network is in the order of sub milliseconds, while the oneway delay without a real radio access network, and without background traffic, is less than 1 ms. Moreover, these delays can be significantly reduced with a container-based deployment rather than a virtual machine-based one. Assuming a 1-ms delay budget for a 5G radio access network, our evaluation confirms that it is indeed feasible to use 5G for GOOSE transmission in IEC 61850 substation automation systems.

Communication within substatation automation systems in a smart grid environment is often time-critical. The time required for exchanging information between intelligent devices should be within a few milliseconds. The International Electrotechnical Commission (IEC) 61850 standard has proposed the Generic Object Oriented Substation Event (GOOSE) protocol to achieve this goal. However, the transmission of GOOSE messages is often limited to a small Local Area Network (LAN). In this demo, we demonstrate the feasibility of using 5G for GOOSEbased time critical communication in a large-scale smart-grid environment, and present a deployable 5G core solution using container-based virtualization technology. The radio part of the demo is emulated. The demo also shows that the delay introduced by the core network is in the order of sub milliseconds, while the one-way delay without a real radio access network is less than 1 ms, which is well below the total delay budget for GOOSE.