LTE Edge Network Enhancement with NFV-basedCore Functionalities

Ioannis Giannoulakis∗, Emmanouil Kafetzakis∗, Michail Alexandros Kourtis∗, George Xylouris∗,Anastasios Kourtis†, Dimitrios Makris∗

∗ORION Innovations, P.C., GreeceEmail:{giannoul; mkafetz; akourtis; gxilouris; dmakris}@orioninnovations.gr

†National Centre for Scientific Research “Demokritos”, Greece.Email: kourtis@iit.demokritos.gr

Abstract—This paper describes the experimentation on theFuture Internet Research & Experimentation (FIRE) Long TermEvolution (LTE) testbeds for open experimentation (FLEX)facilities by combining the existing Evolved Node B (eNB)with an execution infrastructure. In this direction, LTE EdgeNetwork Enhancement with Core Functionalities (LENA) projectwill enhance the LTE FLEX testbed with a Network FunctionVirtualization (NFV) Point-of-Presence, for deploying core func-tionalities as Virtual Network Functions (VNF) at the networksedge. This practice is consistent to the major trends in currentcommunication network technologies. From technical point ofview, the proposed experiment will investigate the deploymentand migration of Evolved Packet Core (EPC) S-GW as a VNF,aiming to increase responsiveness and to reduce the traffic loadof the core network. Edge S-GW VNF solution is expected to bebeneficial in cases of high end-user density and nomadic end-userbehavior. To achieve its goals, LENA will be based upon well-established, open-source NFV orchestration and virtualizationmanagement tools. Following the experimentation described byLENA, the upgraded environment of the FLEX facility willbe exploited and verified, leveraging on the high potential forimprovements relevant to the NFV domain.

I. INTRODUCTION

The developments introduced by Long Term Evolution(LTE) are driven by the continuously increasing demand forcellular access and the fact that new demanding services andapplications enter the scene of licensed wireless networks.This comes on top of the intense competition between mobileoperators, new requirements on the spectrum use and simi-lar challenges from complementary technologies for mobilecommunications. As a result, fresh advances in the fieldare expected to enforce revolutionary changes in networkinfrastructure and management, offering the power to alignwith a demanding set of diverse use cases and scenarios [1].

The need for higher data rates and network capacity isnot the only objective at the scene. There also exists therequirement for an agile and flexible network management,capable of delivering full potential to operators, decreasingtheir costs and enabling an all new type of coordination.Specifically, one of the envisaged key elements of the evolvingtechnological frameworks is the capability to provide intelli-gence directly to the networks edge [2], in the form of virtualnetwork appliances, jointly exploiting the emerging paradigmsof Network Functions Virtualisation (NFV) [3] and Edge

Cloud Computing/Mobile Edge Computing [4]. Evidently,network infrastructures will turn to offer rich virtualisationcapabilities and dynamic processing capabilities on-demand,which will be optimally deployed close to the user.

The current vision about NFV involves the efficient intro-duction of new network services across heterogeneous networkelements, virtualized or not, and underlying technologies. Thisessential shift is revolutionizing the telecommunications busi-ness, affecting the core value chain of the sector (operators,manufacturers, Over-The-Top (OTT) players):

1) The decoupling of network functions from the hard-ware vendor creates an entirely new source of busi-ness for third-party developers, including Small andMedium Enterprises (SMEs), previously unable to enterthe hardware-controlled segment, matching NFVs verticalgrowth (adoption) in the industry with horizontal expan-sion (fresh competition from new sources).

2) Previously locked-in to their hardware vendors, telecomoperators will have greater choice and operational controlof network functions to integrate into their equipment,cutting down functional and maintenance costs.

3) NFV represents not just growth, but also improvementin time-to-market of novel services. Current hardware-constrained network functions suffer from slow imple-mentation and testing, beginning within the hardwarevendor and later in increasingly complex integration atthe telecom operator, and highlight the technological andorganizational challenges that have hindered the industry.

4) Continuous integration and dynamic update has alwaysbeen an issue with legacy hardware equipment. In theNFV spectrum, these are some of the key features ad-dressed in order to provide an always maintained system,while maximizing system availability.

LENA’s main goal is the enhancement of FLEX facilities bybringing NFV to the network edge (i.e., LTE access network),by shifting traffic processing load closer to end users. This willbe achieved by enriching the existing FLEX Evolved NodeBs (eNBs) with edge servers, for hosting both core LTE andapplication service Virtual Network Functions (VNFs).

The deployment of NFV Points-of-Presence (PoPs) andrelevant mechanisms could be beneficial for virtualisation of

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Figure 1. Edge network service deployed in the LENA experiment

macro/small cell Radio Access Network (RAN) [5]. Depend-ing on the available fronthaul solutions (i.e., dark fiber, S1,mmWave, etc.), as well as the capabilities of the eNB, severalvirtualization strategies can be considered; either the virtual-ization of the entire stack into central Base Band Units (BBUs)with distributed Remote Radio Heads (RRHs centralizedapproach) or the exploitation of the conventional backhaul[6]. The virtualization of telecommunication infrastructure canalso lead to moving core LTE transport services to the edgesegment, in cases that this make sense.

II. LENA ARCHITECTURE

While several vendors, including SMEs, are heavily invest-ing in building NFV services, it is true that a combined LTEand NFV environment for the development and testing ofedge VNFs does not exist today. Moreover, most of SMEslack the resources and the complexity needed to test andexperiment on large- (medium-) scale services under a widerange of traffic conditions found in experimental networks.LENA project directly addresses the gap between the virtu-alisation of the communications infrastructure (that has beenextensively studied by several industry and research initiativesup to now) and the applicability of this paradigm to LTE FLEXinfrastructure. Thus, the ambition of LENA is to: a) enhanceFLEX facilities with a diverse set of NFV capabilities andexperimentation tools as well as with sufficient resources fortesting novel core/service VNFs and b) conduct one cuttingedge research experiment (based on the highly configurableopen source Open Air Interface (OAI) Evolved Packet Core(EPC), as shown in Figure 1 and described later on).

The starting point of LENA will be the enhancement of theLTE eNB with an execution infrastructure, capable to executecore network services. LENA will build upon the existing LTEinfrastructure of FLEX, providing an agile environment forproper VNF execution. The instantiation environment of VNFswill be dispersed at the edge of the network footprint, whichis what is referred by ETSI as Network Function Virtualisa-tion Point-of-Presence (NFV-PoPs). The composed servicesprovisioned over these infrastructures impose a number ofchallenges to be addressed. They can be composed of severalfunctions, each of which is developed for a specific purpose,

executed in a combined manner over a shared infrastructurethat may experience continuous workload variations.

The implementation of an enhanced experimentation infras-tructure, tailored to the current FLEX LTE network platform,is presented in more detailed in Figure 2. As shown in theleft-hand side of Figure 2, LENA incorporates existing FLEXexperimentation tools. The experiment will be imported andmonitored through the Experiment Controller module. Thecontroller interfaces the Aggregate Manager that is in chargeof collecting the measurements, providing storage capabilitiesand also storing a list of the available resources. The AggregateManager also interacts with the Resource Controller whichallocates and coordinates the platform resources and the Mea-surement Library, which is in charge of communicating theoutcomes of the experiment to the Measurement Collectionmodule, inside the FLEX Aggregate Manager.

For the experimentation part, LENA integrates a hierar-chical architecture, which is fully compliant with the ETSINFV concepts, terminology and recommendations. On top itimplements the Experiment Orchestrator (which will be basedon T-NOVA Orchestrator TENOR [7]), a management layer toenable orchestration of experiments that encompasses the NFVOrchestrator (NFVO). Furthermore, the Element ManagementSystem of the LTE network and the Monitoring module for theongoing experiment are include here. The LENA ExperimentOrchestrator is in charge of the overall experiment lifecycle,i.e., it handles and interacts with existing resource controlmodules, as well as to the underlying NFVI. It also enablesefficient orchestration and performance-related evaluations ofthe experimentation testbed VNF synchronization and qualifi-cation in a reliable manner.

The NFVO will be in charge of realizing network serviceson the virtualized infrastructure and will include interfaces tointeract with the existing system for high level service man-agement (e.g., exchange of network service descriptors). TheNFVO coordinates groups of VNF instances that jointly realizemore complex functions. To that end, the NFVO uses theservices exposed by the VNF Manager, which will be in chargeof the instantiation, update, query, scaling and termination ofthe VNFs. The Element Management System (EMS) is theprovider of the Fault, Configuration, Accounting, Performanceand Security (FCAPS) functionalities of the LTE network andit consists the framework for handling the network elements.Finally, the Monitoring mechanism will provide a frameworkespecially tailored for NFV services, offering validation of theaccuracy and precision of the monitoring data.

For the NFV layers of the architecture, LENA will exploitwork performed under other NFV-oriented research initiatives(such as, e.g., FP7 ICT T-NOVA and H2020 5G-PPP SESAMEprojects), which will need to be adapted in a degree inorder to match LENA needs. Figure 2 shows an indicativebreakdown of a testbed architecture. The Edge Server providesthe execution environment for the VNFs attached to the LTEeNBs (through Gb Ethernet GbE ). The NFVI is organizedin several NFVI-PoPs (Points-of-Presence in line with ETSIterminology). Also, each NFV-PoP is managed by the Vir-

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Figure 2. LENA Architecture overview

tual Infrastructure Manager (VIM), which is the architecturalcomponent controlling the network and IT resources. TheVIM is responsible for the allocation and management of thecomputing and storage resources for the instantiation of theVirtual Machines (VMs) that host the VNFs as well as theallocation of network resources and internetworking.

III. PROPOSED EXPERIMENTS

Expanding NFV to the network edge, means to deployVNFs in PoPs or locations that are close to the end-user [8].Following that approach, LENA will exploit the concept ofvirtualizing parts of the core network and moving them tobase stations that host the NFV infrastructure.

To that end, VNFs can be deployed, migrated and terminatedat the networks edge in an on-demand fashion to addressspecific system requirements or for optimization purposes. Forexample, flash crowd events may demand the allocation ofextra functionality to cope with the high traffic demand, andallocating that functionality close to the event location allowskeeping latency low and improving throughput while reducingthe Core Network traffic load. In the same way, that extrafunctionality should be dislocated when the crowd disperses.Other possibilities include moving network functions in orderto follow users mobility paths in case it involves efficiencygains, dynamic allocation of functionality in appearing anddisappearing base stations (e.g., user-deployed femtocells), etc.

The experiments aim to achieve and showcase experimentalevaluation of on-demand orchestration (deployment, migrationand destruction) of mobile edge VNFs. On-demand impliesa systems response to changing conditions. This means thatVNFs are deployed, migrated or terminated upon changes onmeasurable aspects. In the experiments, LENA will considertwo kind of variable aspects that may trigger that demand ofmobile edge VNFs: traffic load and users mobility.

Figure 3 depicts two possible edge NFV scenarios. Inthe left hand-side, the increase of the number of users, andtherefore the traffic demand, may require a better configura-tion of the placement of the S-GWs (aggregation gateways).Therefore, the S-GW functionality is duplicated and relocatedat the edge, balancing the traffic towards the Core Network. Inthe right-hand side, the shift of the user traffic load demands

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Figure 3. Deploying (left) and migrating (right) VNFs in the network edge

S-GWs to be migrated to a more suitable location where theoverall network traffic load gets minimized.

Clearly, shifting traffic processing load closer to the end-users allows to reduce latency, improve throughput, and reducethe traffic load in the core network. Additionally, it allows amore convenient scaling procedure for the virtualized EPCfunctions providing clear advantages for the operator side.

In the experiment, the management application senses thetraffic demand and the mobility/distribution of the user termi-nals and deploys/migrates the S-GWs appropriately, gatheringthe specified measurements at the relevant points, and return-ing the results to the experimenter.

The experimentation process performed by LENA permitsoperators to reach the following goals:

1) To evaluate that an edge NFV deployment performs asrequired in the operators network infrastructure.

2) To verify edge NFV performance in terms of: a. Trafficload that the edge NVFs pose to the operators infras-tructure. b. Overhead (in terms of delay, computingcost, service downtime, etc.) of performing the deploy-ment/migrations of the edge NFVs, c. Resource utiliza-tion by the edge VNFs (computing load, memory, net-work, etc.), d. Reliability of the edge NFV deployment.

3) To compare the obtained performance results with theperformance of current network infrastructure.

IV. CONCLUSIONS

LENA aims to reinforce the FLEX FIRE capacity andcontribute to the diversity of the FIRE testbeds portfolio(which already supports domains such as cloud, SDN, IoT,wireless/cellular networks, etc.) by enhancing the LTE exper-imentation facility with the required NFV framework, testbedequipment and VNF benchmarking methodology.

Finally, as mentioned in the Amplifire report Conclusionsand recommendations for FIREs future [9] at the FIRE Board-ing meeting in January 15, FIRE must position itself and moregenerally the concept of experimental testbeds at the coreof the experimental large-scale trials of other Future Internetinitiatives and thematic innovation domains of Horizon 2020.Taking that into account, LENA is the essential piece to bridge

FLEX towards the 5G experimentation in the NFV innovationstrand of the 5G PPP initiative [10].

V. ACKNOWLEDGEMENTS

The work carried out within this manuscript has been fundedby the European Commission through the FLEX G.A. 612050project.

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[5] Small Cell Forum, Release 5.1 Virtualization.[6] Small Cell Forum, 159.05.1.01, Small Cell Virtualization Functional

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