Ioannis P Chochliouros
email: ichochliouros@oteresearch.gr

Anastasia S Spiliopoulou
email: aspiliopoul@ote.gr

Ioannis M Stephanakis

Evangelos Sfakianakis

Evangelia Georgiadou
email: egeorgiadou@oteresearch.gr

Maria Belesioti
email: mbelesioti@oteresearch.gr

Luís Cordeiro
email: cordeiro@onesource.pt

João Gonçalves

Modern Video-to-Video Communications to Enhance Citizens' Quality of Life and Create Opportunities for Growth in "Smart" European Cities

Keywords: Future Internet (FI), interoperability, Living-Lab, quality of service (QoS), right of way (RoW), video-to-video (v2v) communication

ou non, émanant des établissements d'enseignement et de recherche français ou étrangers, des laboratoires publics ou privés.

The Scope of the LiveCity Initiative

In the past decade several video-based communications have entered the market [START_REF] Wang | Video Processing and Communications[END_REF], to become usual in some domains including our working environment, our homes and applications on mobile devices ( [START_REF] Wang | 4G Wireless Video Communications[END_REF], [START_REF]4G Wireless Video Coding for Mobile Communications: Efficiency, Complexity and Resilience[END_REF]). However, we are still lagging behind from the goal of video calls being as easy and ubiquitous as phone calls are today -across any network and between variable devices. There are a number of existing gaps on the pathway to the realization of the Future Internet (FI) ( [START_REF]Future Internet Assembly (FIA): Position Paper: Real World Internet[END_REF], [START_REF] Tselentis | Towards the Future Internet -A European Research Perspective[END_REF]) with live video-tovideo (v2v). These "gaps" do appear at a number of different aspects (i.e.: end-user, service provider, network infrastructure, infrastructure design, service delivery platform, applications provider, end-point device). LiveCity aims to fill most -if not allof the above mentioned gaps, by providing detailed and appropriate responses, per separate case. To this aim, LiveCity considers standard video encoding already available in "off-the-shelf" devices and seeks to resolve diverse issues relevant to the following matters: (i) Intercarrier interoperability; (ii) Service interoperability between different carriers; (iii) Compatibility with most used laptops, notebooks, smart-phones & tablets; (iv) Promotion of the "First-for-consumers" option, by supporting simplicity of installation and usage; (iv) Seamless operation between endpoint devices; (v) Right of Way (RoW) to be provided over various network types; (vi) Consideration of a large number of contacts addressable, together with globally reachable solutions; (vii) Integration of video application within vertical applications; (viii) Extension of the FI ecosystem to include mass-market in several types of communities [START_REF]Organization for Economic Co-operation and Development (OECD): The Seoul Declaration for the Future of the Internet Economy[END_REF].

LiveCity considers a variety of existing underlying network infrastructures and/or related facilities to explicitly serve its defined purposes [START_REF] Chochliouros | Developing Innovative Live Video-to-Video Communications for Smarter European Cities[END_REF]. This includes, for example: 4G wireless technology (i.e.: LTE and WiMAX) coupled with 3.5G wireless technology as well as fixed line xDSL broadband technology in those cases where fixed line is more appropriate than wireless, in urban environments. The "core" aim is to establish a real network with the involved cities together with the inclusion of a RoW without interference from unwanted traffic; this shall permit any potential user, in any of the involved cities, to "experience" live HD v2v. Thus, LiveCity is a pure "technological incorporation trial", that provides modern Internet-based services to over 2,750 users in the involved cities, via the implementation of selected pilot actions. LiveCity creates a wide ecosystem consisting of a variety of market "actors" including public service providers, network infrastructure operators, technology providers and subject matter experts, with the aim of supporting several well-defined public service use cases. LiveCity establishes a "Living-Lab"-like infrastructure [START_REF] Chochliouros | Living Labs in Smart Cities as Critical Enablers for Making Real the Modern Future Internet[END_REF] for the implementation of the selected pilots with diverse user communities, by sharing common service platforms [START_REF] Mulvenna | Living Labs as Engagement Models for Innovation[END_REF]. It actually includes five European cities (i.e.: Athens, Dublin, Luxembourg (city), Valladolid and Greifswald) within an operational public-private-people (PPP) partnership-like framework [START_REF]Commission of the European Communities: Communication on "A Public-Private Partnership on the Future Internet[END_REF] (as shown in Fig. 1). This "Living-Lab"-like scheme offers the possibility for a methodical user co-creation approach, which integrates v2v-based technology for the design and the final delivery of modern services, adopted to conform to the requirements of real-life use cases [START_REF] Kusiak | Innovation: The Living Laboratory Perspective[END_REF].

Pat ient s

Cit y M useu ms

Sch ool

The original LiveCity concept permits to all involved actors-stakeholders to take into account both the global performance of the v2v service as well as its expected potential adoption by users. LiveCity structures a European network of "smart cities", where its smartness attribute originates from the capability to be interactive and live between (remote) locations between citizens in any appropriately connected city. LiveCity public service use cases are driven by public service operators to ensure a proper orientation towards fulfilling real market-born requirements. The technology and network partners come together to leverage both already existing and emerging network infrastructure combined with emerging "off-the-shelf" Virtual Path Slice (VPS) control software platforms and v2v applications software components, together with display/camera devices to realize video communication. This "unifying" approach leads to an operational and exploitable FI-based platform, which can later be rolled-out to other cities and communities, on a broader mass-market basis [START_REF] Chesbrough | Open Innovation: The New Imperative for Creating and Profiting from Technology[END_REF].

LiveCity supports technology that has the ability to massively scale. During the recent years, previous "barriers" to video calling have been remarkably reduced as a result of the widely penetrating high-bandwidth Internet access in most urban areas, together with lower cost of cameras and high-definition multimedia display devices in the market sector. LiveCity "joins together" all necessary components in a low-cost manner and offers a "testing ground" for a v2v mass-market deployment to cities in Europe. Also, it gathers and activates several user groups who can obtain economic and social benefit(s) from the proper deployment-use of live HD interactive v2v service. LiveCity assesses the effect of v2v usage by these "actors" to demonstrate that a "homogenized service" can be available on a mass-market basis, over heterogeneous network infrastructure as actually happens in modern cities. The present public Internet provides a globally reachable "best-effort" network [START_REF] Sood | Technological Evolution and Radical Innovation[END_REF]. It is foreseen that FI should comprise a RoW for a user's traffic, lacking interference from unwanted traffic. Such RoWs are already implemented in virtual private networks by using diverse quality of service (QoS) mechanisms; nevertheless, a RoW without interference from unwanted traffic is not offered to the broad spectrum of users in the mass European market [START_REF]Commission of the European Communities: Communication on "Future Networks and the Internet[END_REF]. In order to offer maximum utility for all potential users, such RoW has to be globally reachable and must be supported on most -if not at all-Internet environments, and at low -or at least at affordablecost so that to be applicable by the users. LiveCity's explicit vision is to "conduct" v2v pilots for a range of user communities initially in the five participating European cities for a range of diverse applications and to support the network infrastructure with a proper RoW, in order that the inelastic traffic can get to the user and support the live experience [START_REF] Klaue | Evalvid -A Framework for Video Transmission and Quality Evaluation[END_REF].

Developing Scenarios of Societal & Economic Impact

LiveCity's core aim is to permit the involved citizens of the participating cities to really interact with each other in a more creative, effective and simultaneously socially useful way, via the use of high quality v2v over the Internet [START_REF] Afuah | Internet Business Models and Strategies: Text and Cases[END_REF]. Video-tovideo communication can be incorporated -or can be the central elementin a huge variety of services/applications, as a "means" to offer advanced services so that to: improve city administration; enhance education and learning capabilities for pupils/teachers; improve or extend cultural, educational and artistic applications offered by involved museums/cultural institutions, thus enhancing city experiences; support patient tele-monitoring and related medical applications in the eHealth sector, and; save patients' lives via v2v inclusion in ambulances, to assist medical personnel for the realization of more effective emergency services. Furthermore, v2v also implicates significant environmental benefits via the reduction of fuel costs and carbon footprint, as it reduces travels within cities, in the scope of all previous purposes. To perform its promising visions, LiveCity is structured around the development of some selected and well-defined scenarios and/or use-cases, of major business and societal impact, as described below, per distinctive case:

Municipal Services: The use of v2v for public administration and/or public information services can drastically enhance the access to and range of services reachable by the Internet. Likewise, this proves to the citizens' communities the effectiveness of a direct face-to-face communication for several municipal services which, in turn, leads to a more efficient user-service provider relationship and can so support the penetration of new services as opposed to voice-only or web-based services. Furthermore, this can decrease fuel costs and green-house emissions as a result of the reduction of travel and traffic within a city [START_REF] Parkinson | Competitive European Cities: Where Do The Core Cities Stand?[END_REF]. LiveCity focuses upon the provision of pilot platforms for use within specific local contexts. It undertakes extensive user requirements capture and development of use-cases drawn from working with real end-users. Besides, v2v can further enhance efficiency and utility of the proposed services-facilities and this is expected to improve accessibility and "comfort in use" of e-government services and physical service to the less ICT savvy, disabled and elderly citizens. As obvious, the above may have significant social and economic impact, resulting in remarkable benefits for individuals. (Effort for this purpose is deployed in the city of Valladolid, in Spain, and is mainly guided by Fundación Cartif and Ayuntamiento de Valladolid). Two specific use cases have been implemented: (1) the "Advisory service for entrepreneurs and enterprise initiatives" and; (2) the "Education for Adults" (see Fig. 2). For the former, the main goal is to offer an integral service for entrepreneurs, having all the required and necessary support during the process of creation for a new enterprise so these initiatives could be properly arranged. In this scope, the phases of the intended activity comprise: (i) A video link for a Valladolid citizen to the interactive municipal online service office; (ii) A proactive advising session; (iii) Purpose/aim to explain -or to support-citizens about their questions concerning entrepreneur service, and; (iv) More approachable communications to be offered from the municipal offices to interested citizens.

Regarding the latter use case, most of the libraries in Valladolid are sited into multifunctional buildings called as "civic centres", where many activities are developed (i.e.: theatre, music, adult education). The "Education for Adult support" is a high-demand service and LiveCity aims to cover the need for the creation and development of volunteering platforms, through which the older people could "channel" their knowledge-experiences to "benefit" others, and enhance both their quality of living and social welfare of the community, in general. The goal here is to encourage the active participation of older people through the volunteer labour in technological and social projects, inter-alia with an innovating will that would imply an active social role and will also generate relationship and coexistence. The work performed -still being in progress-also includes the further refinement of testing methodologies for each use-case and will identify specific elements of the pilots which can bring added social, economic and environmental benefits. City Education: As ICT turns out to be increasingly widespread within the environment of schools, a corresponding LiveCity pilot action focuses on the development of a framework where a v2v network is established between city secondary schools to improve learning and education, as well as to support/extend interactivity-collaboration between pupils and teachers. This latter option offers the possibility, to the involved schools, to work together to realize several projects via a proper "use and sharing" of any available resources and of teachers ( [START_REF] Chochliouros | Enhancing Education and Learning Capabilities via the Implementation of Video-to-Video Communications[END_REF], [19]).

Besides, this scope of interactivity can offer benefits of social value such as: (i) Ability, for leading teachers, to organize classes for students across the globe; (ii) Possibility to provide teachers' training facilities between the involved schools; (iii) Option for enhanced cultural exchanges between participating European schools, thus raising awareness of arts, science and social issues; (iv) Increase of parental participation in education, through the provision of teacher-parent training; (v) Capability to generate richer educational experiences to advance pupil attainment; (vi) Upgrading of the learning understanding of pupils; (vii) Better transfer of skills between pupils and teachers from different participating schools, in a cost-efficient way; (viii) Support of political ambitions -both at EU and national level-to get better education standards; (ix) Support for the formation of an EU-wide education system, potentially reachable by all sections of society, able to sustain gain of knowledge through access to expert teachers; (x) Contribution to the generation of new knowledge, new ideas for learning and teaching through the use of video archives. Work to fulfill these expectations takes places in Dublin and in Athens.

User scenarios that are under exploration include using v2v in a literacy education scenario, in the subject area of arts and in a sport education scenario. LiveCity implements two educational use cases by using FI capabilities to realize v2v in the involved schools in Dublin. These are: [START_REF] Wang | Video Processing and Communications[END_REF] The "School-to-School" (S2S) use case, where v2v is established between schools for applications such as projects, culture awareness and other topics (as in Fig. 3a), and; (2) the "Ask-the-Expert Channel" use case, where v2v is used between children/students after school from their school to a central educational support provider. The purpose is to assist and enhance school activities (see Fig. 3b). (The effort is mainly realized by Skryne School, in cooperation with other LiveCity partners such as RedZinc Services Ltd., QuartzSpark Ltd., Magnet Networks Ltd. and OneSource, Consultoria Informatica Lda). This use case also implicates for one more beneficial impact as it can improve the interactive and social nature of the (participating) museum's exhibits and can thus "be a magnet" for extra visitors who will stay connected for longer periods of time. Through the use of suitable IT equipment which also includes multi-touch tables (MTs), cameras, TV screens and appropriate content management system (CMS) -as shown in Fig. 4this initiative can "make bigger and longer" the cultural experience also with the intention of covering a greater part of the involved city; this can be done by opening-up the possibility for creating exhibits with "mixed" content which is created by the original museum in cooperation with real-world originating content, potentially promoted/created by museum visitors. The core aim is to enable telecom museums visitors to "interact with one-another in a joint experience", via the deployment of fitting games [START_REF] Montola | Pervasive Games: Theory and Design[END_REF]. Games should: be of a well-known concept and be familiar to visitors; flexible and adjustable to different content; multiplayer, but can also be played alone; enhance knowledge about museum exhibits (local and remote). Developed applications are useful for the participating museums to generate common, shared and multi-user experiences that include visitors both onand off-site; this is a remarkable aspect as it implicates potential for "cooperation and content sharing" between geographically diverse locations. Such actions also promote the development of cultural-oriented tourism within the participating cities as well as in a wider EU framework. This can advance the visits and profitability of tourist locations and operate as "a way of creating new revenue streams" [START_REF] Chochliouros | Semi-) Pervasive Gaming Educational and Entertainment Facilities via Interactive Video-to-Video Communication over the Internet, for Museum Exhibits[END_REF]. The pilot takes place between the "twin" cities of Athens and Luxembourg (via an active collaboration between OTE's Telecoms Museum and the P&T Museum, correspondingly) as shown in Fig. 5. (The main partners participating to the realization of this use case are OTE, the University of Luxembourg/SnT and the Municipality of Vrilissia-Athens).

Homework Channel Homework Channel Homework Channel Homework Channel

City Emergency: This specific use case considers a city hospital emergency department (ED) team who has reduced/limited effectiveness because they cannot "see" -and optimally treat-the patient remotely, during the critical "golden hour" before the patient gets to hospital in the ambulance [START_REF] Palma | Tutamen: An Integrated Personal Mobile and Adaptable Video Platform for Health and Protection[END_REF]. The related pilot activity experiments with live high-quality v2v between the ambulance and the hospital and examines options to enhance patient outcomes (e.g., shorter time to administer thrombolysis clot busting drugs in the case of a stroke or survival in a case of a polytrauma) and, consequently, to have early availability of expert opinion at the scene [START_REF] Padki | Healthcare Provider Perspective on Telemedicine in Pre-Hospital Care: A LiveCity Survey of Doctors and Nurses in Emergency Department of Beaumont Hospital[END_REF], when necessary (see Fig. 6a). This implicates speedier access to senior decision making and optimal referring to appropriate centre to facilitate further medical management-treatment [START_REF] Houlihan | Perceptions and Views of Use of Telemedicine in Emergency Care: A LiveCity Survey of Patients attending the Emergency Department[END_REF]. The three specific cases which are being implemented with ambulance video link are: (i) Elevation Myocardial infarction fast track; (ii) Cerebrovascular event/stroke, and; (iii) Entrapment of injured patient (trauma) [START_REF] Panayides | An Overview of Recent End-to-End Wireless Medical Video Telemedicine Systems Using 3G[END_REF]. The corresponding pilot action takes place in the city of Dublin (via the participation of RCSI (Royal College of Surgeons in Ireland) personnel (stationed at the Beaumont Hospital) and working collaboratively with Health Service Executive-HSE and Telefónica O2 Ireland Ltd.). This use case is also to be simulated and is expected to be later implemented in a live clinical setting. A realistic patient simulator test phase [START_REF] Metelmann | Videoübertragung in Echtzeit zur Verbesserung der Notfallmedizin[END_REF] will allow the LiveCity to adopt the needed technical and educational needs for the real world implementation (see Fig. 6b). Simulation takes place in the city of Greifswald, in Germany (via the participation of the Ernst-Moritz-Arndt University of Greifswald).

City eHealth: This use case is related to a glaucoma patient who needs monitoring and/or medical treatment (see Fig. 7). The use of v2v between the home of a patient and hospital/clinic support group enables medical personnel (GP, doctor specialist or nurse) to provide enhanced support and have regular contact with that patient during his/her medical treatment, at lower cost and higher utility [START_REF] Diamantopoulos | E-health Applications for Smart Cities Infrastructures based on Live Video-to-Video Solutions[END_REF], [START_REF] Stamatelatos | Video-to-Video for e-Health: Use Case, Concept and Pilot Plan[END_REF]. By being able to provide faster and more reliable video feeds and medical telemetry tests (telediagnosis and tele-monitoring) [START_REF] Corchado | Using Heterogeneous Wireless Sensor Networks in a Telemonitoring System for Healthcare[END_REF], LiveCity facilitates and improves: the quality of the health service as more often than usual contacts may apply; the quality of life, and; ambient-living conditions for the patients. The inclusion of v2v -that may be also accessible at community level and at mass accesses and least possible price-can provide better solutions to the health problems and it can result in fewer complications and lower medical costs, in parallel with reduced travels and traffic. This pilot initiative is actually deployed in Athens (via the participation of the National & Kapodistrian University of Athens-UoA, mainly in cooperation with the Attikon University Hospital and Innovators S.A.).

All previous use cases are fairly representative among those "shaping the wider profile" of citizen's living in a "smart city" where Internet-based facilities are conceived as the "means" to perform transition to a more inclusive and digitallybased economy and society. Therefore, LiveCity covers a variety of services that are expected to be developed conformant to real users' needs. As v2v planned actions are realized via the joint effort of city authorities and (public) service operators, resulting outcome is important, applicable and beneficial in real-life terms. This can also further strengthen the role of the "user-citizen" in the social and technological innovation lifecycle. For all use cases, stakeholder evaluation and key performance indicators (KPIs) are measured, analyzed and disseminated, appropriately [START_REF] Weerakkody | Utilising a High-Definition Live Video Platform to Facilitate Public Service Delivery[END_REF]. The essential hypothesis is that these indicators -once properly identified-can then be significantly enhanced with the usage of v2v communication [START_REF] Molnar | A Framework Reference for Evaluating User Experience when Using High Definition Video-to-Video to Facilitate Public Services[END_REF]. Work, for this purpose, is coordinated for all use cases by the Brunel University, UK.

Concluding Remarks

The previously discussed LiveCity use cases are all "active and indispensable parts" of the local cities ecosystems and may have major benefits to improve citizens' living standards. The full scope of the related effort focuses upon interoperable actions for testing and validation processes of the proposed facilities, for the uptake of new services and for the benefit of multiple recipients, in real and applicable scenarios [START_REF]Commission of the European Communities: Communication on Europe 2020: A Strategy for Smart, Sustainable and Inclusive Growth[END_REF]. It is worth mentioning that end-users are dynamic "participants" and also "assessors" of the proposed solution(s), while their feedback is taken into account and affects further evolutionary steps.

LiveCity creates of a city-based Living-Lab and associated ecosystem to pilot live interactive high-definition v2v on a variety of existing Internet infrastructure, among 5 EU cities. It implements public service use cases with over 2,750 involved users, by focusing on the application of v2v in a number of selected domains (i.e.: Municipal Services, City Experience, Education and Learning, Emergency and eHealth) with a significant validity for the citizen, also intending enhance a range of KPIs. It also aims to support the acceleration of v2v mass-market start across cities in Europe, by showcasing successful use cases, producing "how-to guides" and providing a "get-up and go" solution to public service operators.

LiveCity considers the proper use and the exploitation of already existing infrastructures-technologies that are truly offered by market operators and so its solutions can be applicable without necessitating any additional investment of resources. It implements selective pilots for motivating the development of innovative FI-based platforms and services; this is performed in a "balanced" partnership scheme including "actors" from different sectors (industry and business sector, citizens, public authorities and academia) with the aim of developing possible "synergies" of value [START_REF] Blumenthal | Rethinking the Design of the Internet: The End-to-End Arguments vs. The Brave New World[END_REF]. Expected results should be important for market development, for supporting local economies and for deploying new services and products, implicating social, technical and economic impacts [START_REF] Castells | The Information Age: Economy, Society, and Culture[END_REF].

Fig. 1 .

 1 Fig.1. LiveCity "Living-Lab"-like infrastructure.

Fig. 2 .

 2 Fig.2. Physical locations for municipal services in the city of Valladolid.

Fig. 3a .

 3a Fig.3a. The "School-to-School" use case, with video interaction.

Fig. 3b .

 3b Fig.3b. The "Ask-the-Expert Channel" use case, with video interaction.City Experiences: With the purpose of enhancing tourism, cultural and city marketing information, a dedicated LiveCity pilot action considers v2v use between museums and/or involved cultural institutes. In the same context, local city administrations can also be involved in the related effort "by choosing the figure and further promoting it". This "opens new horizons" in the corresponding domains as it can widen the capability of any involved legal entities -located across Europe-to offer modern and shared (occasionally mobile) content and/or experiences for both real and virtual visitors.

Fig. 4 .

 4 Fig.4. Diagram of the proposed solution for the LiveCity Museum v2v City Experience use case.

Fig. 5 .

 5 Fig.5. The LiveCity Museum v2v City Experience use case.

Fig. 6a .

 6a Fig.6a. Use of v2v in Ambulances for the City Emergency use case

Fig. 7 .

 7 Fig.7. City eHealth use case, for patient glaucoma treatment.

Acknowledgments:

The present article has been structured in the context of the LiveCity ("Live Video-to-Video Supporting Interactive City Infrastructure") European Research Project and has been supported by the Commission of the European Communities -DG CONNECT (FP7-ICT-PSP, Grant Agreement No.297291). The present work has been realized by the support of all involved LiveCity partners and their contributions to the various work packages, per case.


Ioannis M Stephanakis

Ioannis P Chochliouros
email: ichochliouros@oteresearch.gr

George L Lymperopoulos

Kostas Berberidis
email: berberid@ceid.upatras.gr

Optimal Video Delivery in Mobile Networks Using A Cache-Accelerated Multi Area eMBMS Architecture

Keywords: LTE, Evolved Multimedia Broadcast/Multicast Service (eMBMS), Single Frequency Network transmission, DVB-NGS, cache optimization, ON/OFF Chain Models, traffic modeling

Long-Term Evolution (LTE) evolved into enhanced Multimedia Broadcast/Multicast Service (eMBMS) that features improved perfomance, higher and more flexible LTE bit rates, Single Frequency Network (SFN) operations and carrier configuration flexibility. Multiple eMBMS service areas allow for efficient spectrum utilization in the context of mobile Content-Delivery-Networks (CDNs) as well as for delivering broadcast and push media over modern broadband networks. This paper intends to highlight novel service architectures for efficient content delivery. Content caching is a widely used technique in the networking industry that brings content closer to end-users improving, thus, servive performance and latency. Next generation wireless networks use edge located cache as well as core located cache in order to reduce traffic between the gateway and the internet and make the response of mobile network faster. This is referred to as hierarchical/distributed caching. Dimensioning of individual scenario-based traffic models for health care, museum virtual tours and interactive educational use cases in the context of the LiveCity European Research Project is attempted in this work. ON/OFF source models featuring state dependent active and inactive periods are used in order to describe multi-threaded resource transmissions. A group of chain ON/OFF models holds the parameters of the basic services and defines cache requirements. An architecture that associates distributed cache deployed at eMBMS Gateways per service area is proposed in order to reduce backhaul traffic. A simple algorithm that determines the optimal cache size in a mixture of chain ON/OFF modeled services is presented.

Introduction

Recent advances in the delivery of multimedia content are investigated in this paper. They allow for enhanced user experience and for novel offering from telecom providers. The Third Generation Parnership Project (3GPP) defined multimedia broadcast/multicast service in 2005 in order to optimize the distribution of video traffic in 3GPP specifications release 6 (Rel-6) for Universal Mobile Telecommunications System (UMTS). The standard refers to terminal, radio, core network, and user service aspects. MBMS standard eventually evolved into enhanced MBMS (eMBMS) [START_REF]Evolved Universal Terrestrial Radio Access (E-UTRA) and Evolved Universal Terrestrial Radio Access Network (E-UTRAN); Overall description; Stage 2[END_REF] that features improved perfomance, higher and more flexible LTE bit rates, single frequency network (SFN) operations and carrier configuration flexibility. The introduction of MBMS over Single Frequency Network (SFN) transmission (MBSFN), which is described in Rel-7 of 3GPP specification version, overcomes cell-edge problems of MBMS and allows for the increase of the capacity of broadcast channels by a factor up to 3 or 4 in certain deployment conditions [START_REF]Improvement of the Multimedia Broadcast Multicast Service (MBMS) in UTRAN[END_REF]. An identical waveform is transmitted from multiple cells with a tight synchronization in time in SFN operation. Nevertheless, it is not possible to use the same frequency for MBMS and non-MBMS transmissions in UMTS deployments making. Current 3GPP Rel-11 (2012) specifies improvements in the areas of service layer and Coordinated Multipoint Operation (CoMP) and allows for offloading the LTE network and mobile backhaul through eMBMS. Pushed content via user equipment caching as well as machine-to-machine services are distinctive enhancements. The evolution of the MBMS standard and its performance are presented in many scientific and technical papers [START_REF] Alexiou | Cost optimization of MBSFN and PTM transmissions for reliable multicasting in LTE networks[END_REF][START_REF] Hartung | Delivery of Broadcast Services in 3G Networks[END_REF][START_REF] Hartung | MBMS -IP Multicast/Broadcast in 3G Networks[END_REF][START_REF] Nguyen | Implementation and Validation of Multimedia Broadcast Multicast Service for LTE/LTE-Advanced in OpenAirInterface Platform[END_REF]. Its efficiency in content delivery is addressed in [START_REF] Wang | A Novel Transmission Policy for Reliable eMBMS Download Delivery[END_REF].

eMBMS enables the possibility to deliver premium content to many users with secured quality of service in defined areas. It efficiently delivers rich media to mass users over unicast and broadband/multicast transmissions. A user may send and receive data individually over one-to-one transmissions in the context of such applications as Video-On-Demand, e-mail services, web-browsing and media downloads. One-to-many transmissions on the other hand utilize mobile spectrum more efficiently and result in lower cost for common content. They are used for live video and audio streaming, push media, e-publications, application downloading and other services. Several telecommunication companies adopt eMBMS as an efficient and low-cost means to deliver multimedia content. Qualcomm and Ericsson1 demonstrated their eMBMS solution at Mobile World Congress (MWC) in 2012. Alcatel-Lucent and Huawei have also introduced their end-to-end solution to support broadcast video delivery in LTE networks. Verizon and Telstra announced plans to launch a live video broadcast service for sport events based on eMBMS technology after conducting live tests. Vodafone Germany has conducted live tests with LTE Broadcast in collaboration with Ericsson and Qualcomm as well 2 .

Fig. 1. eMBMS new entities

Cache-accelerated architectures are suggested for current deployments of broadband and content delivery networks (CDNs). Dynamic site acceleration is a suite of technologies that make websites reliant on dynamically served content. The adoption of such technologies makes internet applications perform better and load faster. Traditional CDNs improved performance of telecommunication networks by caching critical content closer to end users. Software-as-a-Service (SaaS) and novel enterprise applications (B2B and B2C) base their functionality upon such notions as personalized recommendations, transactional and secure check-out and shopping carts. This poses stringent requirements on the delivery of dynamic, transactional content, as well as on the demand for e-commerce and web retailers. Traditional cache-accelerated architectures implement most or all of the following technologies (most of which are dealing with optimizing bit delivery across the network):

TCP optimization, which includes algorithms designed to handle network congestion and packet loss. Route optimization, which is a technology that optimizes the route of the request from the end-user to the origin and ensures the reliability of the connection. Connection management, that includes persistent connection provision and HTTP multiplexing. Reusable and optimized HTTP connections from the edge servers to the origin servers as well as between the edge servers themselves are maintained rather than initiating a new connection for every request.

On-the-fly compression, that compresses text objects shortly after they leave the origin servers alleviating, thus, computational burden from the origin servers without requiring additional bandwidth or hardware. SSL offload in order to speed up the critical secure transaction processes such as a check-out at an online store. Pre-fetching, that will parse through a served HTML file and will prefetch from the origin server the cacheable objects embedded in the file. A CDN can prefetch only cacheable content. Dynamic content by definition is contextual and can only be requested by the user. Whole-site delivery, that identifies cacheable and dynamic content and whether dynamic site acceleration techniques are applicable to the dynamic content of a site instead of simple fetches from the origin server. Novel approaches have introduced such techniques as preresolving (performing DNS lookup in advance), preconnecting (opening a TCP connection in advance) and prewarming (sending a dummy HTTP request to the origin server) [START_REF] Cohen | Prefetching the Means for Document Transfer: A New Approach for Reducing Web Latency[END_REF]. Response time for a mobile application is defined as the time between clicking to request information and loading a web page. Specifying cache size requires accurate modeling of application traffic. ON/OFF internet traffic models are frequently used for such a cause [START_REF] Adas | Traffic Models in Broadband Networks[END_REF]. Measuring analysis and modeling of traffic has still been one of the main research challenges. Several studies have been carried-out over the last fifteen years on analysis of network traffic in the internet [START_REF] Abrahamsson | Traffic measurement and analysis[END_REF][START_REF] Williamsson | Internet traffic measurement[END_REF], traffic measurements in high speed networks [START_REF] Celeda | High-speed network traffic acquisition for agent systems[END_REF] as well as measurements in next generation networks [START_REF] Pezaros | Network Traffic Measurement for the next Generation Internet[END_REF]. A brief description of the novel features and the architecture of eMBMS is presented in Section 2 whereas a comparison with the DVB-NGH standardwhich is currently under development -is attempted is Fig.

Flexible spectrum allocation between unicastbroadcast services

Section 3. Dimensioning issues for cache acceleration are considered in Section 5 and a novel approach for dynamic parameterization of buffers at edge servers based upon optimal storage for chain ON/OFF modeled services in the context of eMBMS is proposed and evaluated.

2 Evolved Multimedia Broadcast/Multicast Service (eMBMS) in LTE-Advanced

Features And Services

An evolved architecture is required to support eMBMS transmission in LTE network. The novel logical network entities proposed for eMBMS operation are the following [START_REF] Lecompte | Evolved Multimedia Broadcast/Multicast Service (eMBMS) in LTE-Advanced: Overview and Rel.-11 Enhancements[END_REF]: BM-SC (Broadcast Multicast Service Center), which is the entity that connects the Content Provider and the Evolved Packet Core. This entity plays the role of traffic shaper and authorizing content provider/terminal request. It is in charge of SYNC protocol to synchronize transmitted data among eNBs. SYNC protocol associates a specific header to IP packets, providing Time Stamps and session information. eMBMS Gateway, which is the entity located between BM-SC and all eNB. Its principal function is to deliver MBMS user data packets to eNBs by means of IP Multicast. When an MBMS session arrives, it allocates IP mulicast address to which the eNB should join to receive MBMS data and maintains the IP Multicast group. Furthermore, eMBMS Gateway is responsible for MBMS session announcement and it also performs MBMS Session control Signaling (Session Start/Stop) toward E-UTRAN. MCE (Multi-cell Coordination Entity), which is the logical entity whose function is admission control and allocation of the radio resource use for MBSFN operation. The MCE is expected to be part of e-UTRAN and can be integrated as a part of a network element. MCE may be either part of eNB (a "distributed MCE architecture") or be a stand-alone MCE ( "centralized MCE architecture"). Interfaces M1, M2 and M3 (see Fig. 1) connect the aforementioned new entities with each other. M1 interface is a user plane interface that connects e-MBMS-GW and eNB. M2 interface is a control plane interface between MCE and eNBs whereas M3 interface connects MME and MCE. M3-Application Part allows for MBMS Session Control Signaling on E-RAB level.

MBMS defines three MBMS-specific radio bearers, i.e. MICH (MBMS indicator channel) which is used to notify terminals about the imminent start of an MBMS transmission session, MCCH (MBMS control channel), which carries control information about all ongoing MBMS transmission sessions and MTCH (MBMS traffic channel), which carries the actual data of an MBMS transmission session. Since HTTP cannot be used on unidirectional links, a unidirectional protocol was introduced for delivery of files or file segments, the socalled FLUTE protocol (File Delivery over Unidirectional Transport -RFC 3926). FLUTE protocol is carried over the User Datagram Protocol (UDP) and IP multicast toward end-user devices.

3 GPP Rel. 11 enhancements of eMBMS specify a mechanism that allows end-user devices to retrieve missing parts of a file after a broadcast session is over. This is due to the fact that it is impossible to use hybrid automatic repeat request (HARQ) on lower layers of unidirectional bearers. This mechanism is called file repair. Adaptive HTTP streaming, that is adopted by the Moving Pictures Experts Group as the baseline of MPEFG-DASH is specified in 3GP-DASH [START_REF]Release 10: Transparent end-to-end packet-switched streaming Service (PSS); Progressive download and dynamic adaptive Streaming over HTTP (3GP-DASH)[END_REF] as a compatible to MPEG-DASH profile. LTE resources reserved for eMBMS only when needed and there is no impact on LTE unicast capacity at other times (see Fig. 2).

Network Architecture And eMBMS Service Areas

A synchronous LTE network allows broadcast over a Single Frequency Network (MBSFN). An MBSFN area is defined as the set of cells participating in the same SFN transmission. Should different services be transmitted in the same cell but have different coverage areas, the cell transmits them in different time intervals where a different set of cells participate to the same SFN transmission (the cell/eNB may belong to up to eight MBSFN areas). The maximum extension of MBSFN areas is determined by the size of areas where cells are synchronized, which is called synchronization area. MBSFN transmissions not only include the data of the MBMS services but also periodic MBMS control and scheduling information messages indicating which services are currently transmitted and in which time intervals they may be transmitted. Efficient signal combining at user terminals achieves high operating SNR. Key Use Cases that take advantage of such an architecture include streaming video for real-time situational awareness, Push-To-Talk, file delivery for non-real-time services such as all points bulletin (e.g. amber alert), software updates/upgrades etc. Scalable push file delivery and delivery of content services are described in [START_REF] Lohmar | Delivering content with LTE Broadcast[END_REF][START_REF] Lohmar | Scalable Push File Delivery with MBMS[END_REF].

Comparison With Digital Video Broadcasting (DVB-NGH)

At the time MBMS over UMTS terrestrial radio access network (UTRAN) was standardized, the industry was focused on the mobile TV use case. Digital video broadcasting for handheld (DVB-H) networks was being deployed in several countries, and MBMS seemed like a way for mobile broadband operators. Alternative technologies for multimedia broadcasting that emerged were DMB (Digital Multimedia Broadcasting) deployed mainly in South Korea, ISDB 1-seg in Japan and in South America and MediaFLO (Forward Link Only) [START_REF]Forward Link Only Air Interface; Specification for Terrestrial Mobile; Multimedia Multicast[END_REF] in the USA. Qualcomm had conducted MediaFLO technical trials internationally at the time but discontinued development in 2010 whereas Japan has moved forward with ISDB-Tmm (Terrestrial mobile multi-media), which is a variant of the existing standard.

Digital video broadcasting for handheld (DVB-H) networks is a standard which is compatible with digital terrestrial TV (DVB-T) and transmits through digital terrestrial channels taking advantage of the digital dividend. Nevertheless DVB-H has been a commercial failure and the service is no longer on-air. Finland was the last country to switch-off signals in March 2012. The DVB group made a "call for technologies" for a successor system (DVB-NGH -Next Generation Handheld) in November 2009 in order to update and replace the DVB-H standard for digital broadcasting to mobile devices. The schedule was for submissions to be closed in February 2010. The new ETSI standard [19] published in 2013 and rollout of the first DVB-NGH devices is planned for 2015. DVB-NGH defines the next generation transmission system for digital and hybrid broadcasting to handheld terminals, i.e. a combination of digital terrestrial and digital satellite transmissions. The standard is based on the DVB-T2 system and reuses or extends lot of novel concepts introduced in the DVB-T2 specification. It adopts SFN transmission.

Cache Acceleration in CDNs And Dimensioning Considerations For Several Use Cases

Web is considered as a set of servers and clients, i.e. web browsers and any other software that is used to make a request of a Web server. Requests and responces of the hypertext transfer protocol (HTTP) before the establishment of a new connection determine the delays in retrieving some resource. It is estimated that the amount of time that is required can be approximated by two round-trip times plus the time to transmit the response and any additional DNS resolution delays. Caching is performed in various locations throughout the Web including at the two end locations. Proxy caches are intermediary caches between the client machine and the origin server. They generate new requests on behalf of the users if they cannot satisfy the requests themselves. Next generation wireless networks use edge located cache as well as core located cache in order to reduce traffic between the gateway and the internet and make mobile network response faster. This is refered to as hierarchical/distributed caching. Internet Cache Protocol (ICP) is an example of a popular mechanism used for coordinating caches in many different locations. The ICP protocol is described in RFC 2186 and its application to hierarchical web caching in RFC 2187. Hypertext Caching Protocol (TCP) (RFC 2756) is designed as a successor to ICP. Object hit rate and byte hit rate are used as measures in dimensioning cache size by network operators. Response time for mobile applications is determined by server processing time, delays in the network (bandwidth availability, round-trip time-RTT and tower connect time) as well as delays in the client device (parse time, resource fetches, layout and render processing and JavaScript delays). Less bandwidth, which is subject to frequent changes, is dedicated to downloading in mobile networks compared to the bandwidth which is dedicated to downloading in fixed networks. Furthermore processing speeds of mobile devices are up to ten times slower as compared to desktops. The path to faster mobile delivery therefore lies in reducing the number of round-trips as much as possible, reducing content payload size as much as possible, defer as much as possible and parse as little as possible.

One needs to classify and model traffic patterns at the edge of the mobile network in order to dimension cache. Chain ON/OFF models are adopted to this end. The design and development of a chain ON/OFF model relies on an accurate description of traffic entities from link level to application level. The model is generally used, Process of Type A Process of Type B Fig. 3. Chain ON/OFF models used in the numerical simulations when it is necessary to capture the scaling behaviors of network traffic. A chain ON/OFF model uses two states, namely ON & OFF for each state of a Markov model [START_REF] Adas | Traffic Models in Broadband Networks[END_REF]. ON and OFF periods are usually heavy tailed processes. ON times correspond to resource transmissions while the OFF times correspond to intervals of browser inactivity. Furthermore, OFF times are classified either as Active (which account for client processing delays like document parsing and resource rendering) or as Inactive (i.e. user think time). The Weibull [20] and the Pareto [21] distributions are used to model ON and OFF times. Data generated by a specific type of application/service are discribed by a distinctive chain ON/OFF model. A queue that stores content at the edge of the mobile network is shared by different chain ON/OFF sources that are assumed to be statistically independent. The overall traffic through the edge aggregation link is modeled as a mixture of N chain ON/OFF sources belonging to M different groups, i.e.

M M Proc N n Proc N n Proc N n ... , 2 2 1 1
. The chain ON/OFF sources which belong to a specific group are characterized by the transition probabilities between states as well as the mean number of packets/cells generated during the ON states and the relationship between ON and OFF periods. The probability of accessing one of the resources stored in a proxy cache resembles accessing a word in a written text of a natural language and can be calculated through the Zipf distribution [START_REF] Glassman | A Caching Relay for the World Wide Web[END_REF][START_REF] Cunha | Characteristics of WWW Client-based Traces[END_REF]. Specifically, the number of references to cached item i, NR i , is given as follows,

Z i i rank NR ) ( ~ , (1)
where rank(i) denotes the position of cached item i after the sorting of the cache population on the basis of references (i.e., the most popular item is ranked first, the second most popular is ranked second and so forth), is a constant value while Z is the Zipf parameter, which assumes a value close to 1. Should one choose so as to normalize the sum of all references to a unit probability, he gets,

size cache i z size cache i i hit i rank a NR P 1 1 ) ( , (2)
LiveCity use cases include medical tele-monitoring for patients' treatment, city experiences (like interactivity in museums and cultural institutes, educational activities etc), municipal services and a school channel. One may use the chain ON/OFF model, which is illustrated in Fig. 3 as process of Type A, in order to describe such use cases as interactive guided tours in museums and other cultural institutes and the chain ON/OFF mo-del illustrated as process of Type B in order to describe tele-monitoring sessions and several municipal services. Streaming video for real-time situational awareness, Push-To-Talk municipal services and file deli-very for non-realtime ser-vices such as allpoints bulletin (e.g. amber alert), software updates /upgrades etc as well as a regional school channel may be implemented as broadcast services in the context of eMBMS deployment. Accessing a set of WWW resources (like HTML pages with embedded images) is modelled as a process of Type B in [START_REF] Hadjiefthymiades | Using Proxy Cache Relocation to Accelerate Web Browsing in Wireless/Mobile Communications[END_REF][START_REF] Barford | Generating Representative Web Workloads for Network and Server Performance Evaluation[END_REF].

Numerical Simulations Using ON/OFF Chain Models

Not all content is cacheable. Personal data such as digital medical images and examinations as well as patients' records in the context of a telemedicine session are in general not cacheable. This holds true for personal data that may be transmitted in the context of a distance learning broadcasting. Overall 19.80-32.20% of unique URLs are uncacheable as estimated in [START_REF] Sunghwan | Understanding and Improving Modern Web Traffic Caching[END_REF]. This accounts for 21.50-28.32% of the total requests and 10.48-14.81% of the total bytes. HTML and JavaScript are dynamically generated and, thus, less cacheable. Analysis of real data in [START_REF] Sunghwan | Understanding and Improving Modern Web Traffic Caching[END_REF] indicates that, finally (after a certain buffer size) the slope of byte_hit_rate, which is denoted as ) _ ( size buffer service , decreases as the size of the buffer increases. This leads to the following straightforward proposition regarding the optimal buffer size, Proposition The maximum value of the total (byte_hit_rate x users x reguests) for a constraint size of a buffer used for caching requests for a mixture of M services is given as the sum of the buffer sizes allocated to each service for which the following condition holds, . Total byte hit requests (byte hit rate x users x requests per user) are added for the same slope. The optimal slope decreases for higher budgets of buffer storage. Hit rates are up to 30%. Changing the mixture of the two services results in a different optimal value for the buffer size.

Conclusion

LTE eMBMS takes advantage of single frequency network features and allows for flexible content delivery via unicast, multicast and broadband services. Live tests have been conducted by several companies. There is an increasing interest in launching commercial deployments and offering localized services through enhanced infrastructure. Service delivery and user experience may be boosted by web caching and acceleration by storing frequently accessed content at the edge of the network. A dynamic dimensioning scheme for optimal cache allocation is herein proposed. It requires traffic modeling of the services offered to the users. It assumes that the frequently accessed content is stored at the eMBMS gateway, which receives unicast streams and delivers MBMS user data packets to eNBs by means of IP multicast. Future work will emphasize upon dynamic buffer dimensioning according to the proposed approach taking into consideration such novel cache-accelerated techniques as request multiplexing and multi-resolution chunking. The proposed optimality condition may be applied in conjunction with such novel approaches as well.

Simulation results are consistent with actual traffic measurements that are reported in the literature [START_REF] Ahmad | Scenario-Based Traffic Modeling for Data Emanating from Medical Instruments in Clinical Environment[END_REF].

Table 1 .

 1 Parameters of the chain ON/OFF models according to Fig.3

Fig. 4 .

 4 Fig. 4. Hit rate (upper row) & byte hit rate (lower row) per service (left for service modeled as Type A, right for service modeled as Type B). Buffer sizes indicate optimal allocation.

Table 1 .

 1 Process Type B, one with state ON1 and two with state ON2. It is assumed that the sizes of the embedded objects are equal for each distribution. The selection of parameters of chain ON/OFF models is based upon actual measurements for web traffic caching like those presented in[START_REF] Sunghwan | Understanding and Improving Modern Web Traffic Caching[END_REF] and results for modelling data emanating from medical instruments in clinical environment ([START_REF] Ahmad | Scenario-Based Traffic Modeling for Data Emanating from Medical Instruments in Clinical Environment[END_REF]). A 10 Gbps link is assumed to connect cached content at the gateway to the backbone network. The gateway is assumed to provide services for 500 concurrent users. Active ON times for non-cached objects are modeled according to Pareto distribution[21] with mean equal to Object_size/User_bandwidth. The delay for all cached objects is assumed to equal 200 ms. Active OFF or client processing delay is modeled according to the Weibull distribution[20]. It ranges from 1 msec to 1 sec. Inactive OFF times follow the Pareto distribution. All parameters are summarized in Simulation results are illustrated in Fig.4. Both hit rate and byte hit rates are given. Optimal buffer size is estimated as

		byte _ (	hit	_	size users buffer rate _ x	x	requests	)	|	per	service	service	(	buffer	_	size	)	opt	(3)
	for all of the M services.
		A				mixture						of			two	services	modeled	as
	0 {	.	67	Pr	ocess	Type	, A	0	.	33	Pr	ocess	Type	} B	is simulated. Three distinctive
	reference distributions are associated with ) ' ( ) ' ( 2 1 s s

Ericsson at http://www.ericsson.com/res/docs/whitepapers/wp-lte-broadcast.pdf last accessed 30th of April

2 GlobeNewswire at http://globenewswire.com/news-release/2014/02/25/612970/10069866/en/ Europe-s-first-live-trial-of-LTE-Broadcast-revolutionizing-video-delivery-across-mobilenetworks.html last accessed 30th of April 2014.

Acknowledgments. This research work has been funded by the LiveCity European Research Project supported by the Commission of the European Communities -Information Society and Media Directorate General (FP7-ICT-PSP, Grant Agreement No. 297291).


Panagiotis Diamantopoulos

Eleni Patouni
email: elenip@di.uoa.gr

Nikolaos Bompetsis
email: nbompetsis@di.uoa.gr

Nancy Alonistioti

João Gonçalves

Luís Cordeiro
email: cordeiro@onesource.pt

Ioannis P Chochliouros
email: a.ichochliouros@oteresearch.gr

George Lyberopoulos

Video-to-Video E-Health Applications Supporting Medical Use Cases for Remote Patients

Keywords: e-Health, emergency, telemonitoring, video-to-video (v2v) communication

Information and Communication Technologies (ICT) relevant to health and healthcare systems can rise their effectiveness, expand quality of life and "reveal" innovation and novelty in modern health-related markets, thus implicating options for further growth. The broadly used term "e-Health" regularly implicates the use of ICT in health products, services to improve health of citizens, efficiency and productivity in healthcare delivery, and the economic and social value of health, in general. In this end, the LiveCity Project aims at empowering the citizens of a city to interact with each other in a more productive, efficient and socially useful way, by using high quality video-to-video (v2v) over the Internet. In this work, the LiveCity platform for e-Health is presented, along with two use cases for remote patients telemonitoring and emergency cases.

Introduction

Over the past few years the vast advances on both wired and wireless technology has changed the face and aim of many service providers, including social ones. The uses of Internet and Video-to-Video (v2v) applications have provided users across the globe with the ability to overcome significant obstacles on their communication, including geographical and language barriers. Furthermore, the integration of Future Internet (FI) application in sectors of social welfare has become a subject of extensive research from many organizations. One of these sectors, which can be significantly enhanced by the use of FI technology, is the health care [START_REF]European Commission: Communication on "e-health Action Plan 2012-2010 -Innovative Healthcare for the 21s Century[END_REF].

Despite the advancements on medicine and health care systems, the rates of treatment failures remain significantly high for some cases where their treatment could be relatively easy. This is attributed mainly due to the inability of the patient to be physically present to the hospital and/or his difficulty to conform to the treatment ( [START_REF] Pawar | A Framework for the Comparison of Mobile Patient Monitoring Systems[END_REF], [START_REF] Doukas | Digital Cities of the Future: Extending@ Home Assistive Technologies for the Elderly and the Disabled[END_REF]). Also, serious medical incidents are often failed to be addressed successfully due to delays between the incident and the provided treatment.

There are several systems that have managed to integrate successfully ICT applications to the health-care domain ( [START_REF] Vargiu | Context-Aware Based Quality of Life Telemonitoring[END_REF], [START_REF] Corchado | Using Heterogeneous Wireless Sensor Networks in a Telemonitoring System for Healthcare[END_REF]). However, none of the aforementioned systems tackle the problem of high quality video calls across multiple devices. Existing video platforms that can be used for realizing v2v services do not provide the facility to integrate additional features. Furthermore, many of these platforms fail to guarantee the necessary data protection or QoS such applications require [6]. The LiveCity project aims on creating a set of plugins that integrate high quality video streaming that is used for the communication between patients and health care providers, while ensuring both security and high Quality of Service (QoS) ( [START_REF] Chochliouros | Developing Innovative Live Video-to-Video Communications for Smarter European Cities[END_REF], [START_REF] Iliadis | CIP/LiveCity -Live Video-to-Video Supporting Interactive City Infrastructure[END_REF]).

The rest of the paper is organized as follows: Section 2 provides an overview of the network infrastructure used for the realization of two different use cases. Section 3 and Section 4 present these use cases along with their respective applications. Finally conclusion remarks and directions for future research are drawn in Section 5.

LiveCity E-Health Platform

The LiveCity Network allows the communication of different plugins and provides the infrastructure for achieving high quality end-to-end video streaming. Furthermore, since this network is designed to accommodate use cases addressing serious medical conditions, as well as patient monitoring, the network incorporates a series of encryption and security mechanisms. These mechanisms implement state-of-the-art secure communication channels and protocols, thus ensuring data protection and preventing the extraction of sensitive medical information.

To guarantee the high quality bidirectional video streaming between two individual plugins, the network has integrated a QoS mechanism, called as "Virtual Path Slice" (VPS) engine. The VPS engine is a network resource reservation mechanism. It can be accessed through a specialized interface installed on every end-user plugin and allows the on-demand bandwidth reservation for providing constant bandwidth during video calls.

Figure 1 provides an overview of the underlying infrastructure of the related Live-City network.

The Client Plugin provides a simple Graphical User Interface (GUI) that exposes a series of commands that a user can give to the v2v Module. Also this plugin is responsible for presenting both local and remote video feed to the user. The v2v Module is the software component that is integrated to each Client Plugin and works as an intermediate layer between the end-user device and the v2v server. It is responsible for handling the communication between each plugins and the server, as well as, for initiating and maintaining the video stream during an active video session. Furthermore, the v2v Module is responsible for interacting with the VPS engine and request specific bandwidth reservation for a video call.

The v2v server is the main message dispatcher between the individual plugins connected to the LiveCity network as well as the means of authenticating different connection requests. Finally, the v2v server integrates the aforementioned encryption mechanisms ensuring the protection of data. This use case allows the direct video-to-video connection between different healthcare providers and patients. Through the use of LiveCity Telemedicine plugin, a doctor can communicate and interact with patients, on remote or inaccessible locations, providing useful advice to persons in need. Furthermore, the use of public Internet as a main design axis renders the application easy-to-use, without the need of specialized hardware or software.

This use case was materialized for the monitoring of glaucoma patient in coordination of the Attikon Hospital in Athens, Greece and the National and Kapodistrian University of Athens.

Application

This LiveCity Telemedicine plugin provides two different end user applications, one addressing the need of the doctor and the other the needs of the patients.

Both applications have a simple, user oriented graphical interface, which exposes all the core functionality provided by the v2v module. By pressing the respective buttons, a user can connect or disconnect from the LiveCity network, provide his opinion and feedback regarding the application and reconfigure it.

The plugins also allow the modification of the characteristics of the transmitted video through a settings interface. To accommodate inexperienced user, four standardized profiles have been implemented that allow different quality of the transmitted video ranging from 360p to 1080p (Full high definition-HD). When a video call is active between two clients, each one can modify its respective settings of the received image in order to obtain better video and audio quality.

Despite their common functionality, the Doctor Telemedicine plugin differentiates from the one targeting patients, since it provide the means for establishing a direct video-to-video communication with connected patients. Furthermore, it can "adjust" the remote video that is transmitted from the patient by determining higher or lower video profile. Finally, this plugin allows the doctor to retrieve a snapshot of the patient as complement information to his examination.

On the other hand, the Patient Telemedicine plugin aims on providing a notification system that allows the immediate notification of the doctor, when a patient requires his assistance via the application or a SMS (Short Message Service). Finally, this plugin does not provide the aforementioned functionality for changing the remote video received from the doctor or for retrieving a snapshot of the video feed.

Use Case Description

This use case aims at accommodating patients in emergency medical situation, such as heart attacks or strokes, during the "golden hour" (that is the critical time period when a patient is transferred, e.g. via an ambulance, to the nearest emergency center of a hospital for immediate medical care). Through the use of video-to-video application, emergency personnel in ambulances can communicate directly with qualified personnel to the hospital and ask for proper advice. With this kind of communication the time to provide important treatment is significantly reduced, thus increasing the chances of patient's successful recovery.

Application

This use case was materialized through the use of specialized equipment for the emergency personnel, while the hospital side used commodity laptops and simple xDSL1 lines.

This specialized equipment is a wearable backpack computer that consists of offthe-self items and provides all the necessary components for achieving high definition video transmission thought wireless networks. It is comprised by: A microcomputer which acts as the main component for transmitting the video feed to the hospital as well as for receiving the audio feed from the hospital. A modem that allows the connection of the backpack computer to any wireless network.

A simple 4 button interface that allows the immediate issue of commands to the computer.

The necessary hardware (HD camera, headset) for receiving and transmitting the best possible quality of video and audio.

The software used on this use case was designed as a command line interface mainly for energy efficiency reasons. It receives input through the buttons and provides audio feedback to the user. Upon activating the backpack, it connects to the hospital side allowing the immediate communication between the two ends. Finally, a set of additional commands can be issued from the user that allows him to notify the hospital side, requesting immediate attention.

Conclusions

Fueled by advances in mobile and wireless communications, the last decade has seen an unprecedented proliferation in the service delivery and devices interconnection across the globe. This is particularly important towards the vision of "Smart Cities", where physical infrastructure is complemented by the availability of intellectual and social capital, increasing both urban competitiveness and quality of life. However, before such a paradigm shift can be realized, significant challenges need to be resolved to support remote communications with high QoS / QoE (Quality of Experience) "anywhere and anytime", thus serving remote patients. Such gaps are investigated by the EU-funded LiveCity Project ("Live Video-to-Video Supporting Interactive city Infrastructures"). In this paper, we presented the LiveCity platform and two respective e-health use-cases. The first use case builds upon the use of v2v for remote telemonitoring of glaucoma patients while the second one analyzes the benefits of v2v for emergency cases. In the next steps, we plan to analyze the results of these two ongoing pilots.

Fig. 1

 1 Fig. 1. Network Infrastructure

The term "xDSL" stands for any type of Digital Subscriber Line access technology.

Acknowledgments. The present article has been structured in the context of the LiveCity Project and has been supported by the Commission of the European Communities -DG CONNECT (FP7-ICT-PSP, Grant Agreement No.297291).


Dimitrios Alonistiotis

Evgenia Kontou

Nikolaos Karachalios

Eleni Patouni
email: elenip@di.uoa.gr

Panagiotis Diamantopoulos

Nikolaos Bompetsis
email: nbompetsis@di.uoa.gr

Nancy Alonistioti

Ioannis P Chochliouros
email: ichochliouros@oteresearch.gr

Remote Video-to-Video Eye Telemonitoring Use Case for Glaucoma Patients

Keywords: e-Health, glaucoma, telemonitoring, video-to-video (v2v) communication

des établissements d'enseignement et de recherche français ou étrangers, des laboratoires publics ou privés.

Introduction

According to the World Health Organization (WHO) and all the available surveys, glaucoma is the second leading cause of blindness globally as well as in most regions of the world, following only cataract, and the third in the developed world, following Age-related Macular Degeneration and Diabetic Retinopathy ( [START_REF] Resnikoff | Global Data on Visual Impairment in the Year 2002[END_REF]- [START_REF]The World Health Report 2003: Shaping the Future[END_REF]). It is also considered to be the second most common cause of avoidable visual impairment [START_REF] Quigley | The Number of People with Glaucoma Worldwide in 2010 and 2020[END_REF].

Glaucoma is an optic neuropathy with certain features including an intraocular pressure that is too high for the continued health of the eye, which leads to ganglion cell death. Ophthalmology so far has focused in the management of glaucoma through the lowering of the intraocular pressure and the preservation of the remaining visual ability [START_REF] Leske | Factors for Progression and Glaucoma Treatment The Early Manifest Glaucoma Trial[END_REF]. This is achieved primarily by eye drop instillation daily and only in few selected cases by surgery or laser. Normal intraocular pressure values vary from 10 to 21 mmHg, and most glaucoma patients tend to have more than 24 before diagnosis [START_REF] Heijl | Early Manifest Glaucoma Trial Group. Reduction of Intraocular Pressure and Factors for Progression and Glaucoma Progression: Results from the Early Manifest Glaucoma Trial[END_REF]. Regaining some of the impaired vision due to glaucoma is impossible.

At the same time, glaucoma treatment heavily reduces the quality of life of the patient. The European Glaucoma Society has insisted that glaucoma therapy must abide by a good quality of life for the patient, according to the stage of the disease, the patient's age, general health and even life expectancy and also his abilities and needs [START_REF] Kholdebarin | Multicenter Study of Compliance and Drop Administration in Glaucoma[END_REF]. The main reason that Glaucoma influences the patient's attitude towards his therapy is that it stays an asymptomatic disease until the end-stage of the glaucomatic damage (when preservation of vision is impossible by then) and can only be detected through preventive examination of the intraocular pressure and the optic nerve. Secondly, chronic use of eye drops causes topical side effects like redness of the eye, discomfort, itching, conjunctivitis, blurry vision, even hyperpigmentation of the iris and enlargement of the eye lashes in the most common anti-glaucoma drug category. Even systemic side effects from long lasting anti-glaucoma therapy, including depression, respiratory and cardiac side effects and sexual impotency have been noticed. So, in most cases, a healthy otherwise and asymptomatic individual who goes for a check-up to the Ophthalmologist and is suddenly considered and treated as glaucomatic ends up with many different symptoms not from the disease itself but from the medications with an aim to maintain -and not restore-his vision. Last but not least, the cost of therapy for the entire lifetime becomes an economic burden for the citizen.

For all the above reasons Glaucoma holds a record in noncompliance to therapy from the patients. Several surveys have shown that glaucomatic patients do not take their medications correctly in a percentage up to 50% [8]. Besides that, because of the nature of the disease, it is estimated that there is also a 50% of undiagnosed glaucomatic patients in the general population and that almost half of the people under anti glaucoma therapy may not need it after all. Moreover, because many glaucoma patients need more than one medication (eye drop) and in different daily frequency or time of instillation (once or twice by day), are geriatric patients or with specific difficulties with applying medication, (e.g. due to tremor), noncompliance to therapy increases according to the number of eye drops per day, number of medications, age, general mental condition ([9]- [START_REF] Bloch | Patient Compliance in Glaucoma[END_REF]).

Pharmacy companies have tried to improve this by producing more effective drugs, reducing the daily need for eye drops, introducing drugs with less side effects and preservative free single use blisters. Nevertheless, glaucoma patients need close follow up for their obedience to therapy and even training for the correct instillation of eye drops [START_REF] Busche | Improved Eyedrop Administration and Compliance in Glaucoma Patients. A Clinical Study[END_REF].

The rest of the paper is organised as follows. Section 2 analyses the Livecity project research in the area of e-health, focusing on the description of the telemedicine platform and software application for remote patients telemonitoring. The telemonitoring use case for glaucoma patients is introduced in section 3. Finally conclusion remarks and directions for future research are drawn in section 4.

The LiveCity e-Health Research for Smart Cities

The LiveCity Project [START_REF]FP7-ICT-PSP LiveCity project[END_REF] is based on live high-definition interactive video communication easily available on user equipment. LiveCity e-Health for glaucoma is a part of this European program, which aims to improve the quality of life of chronic patients, reduce their need for transportation to the Hospital and facilitate communication with the doctor through a high definition video-to-video telemonitoring from the patient's home [START_REF] Patouni | CIP/Live City -Live Video-to-Video Supporting Interactive City Infrastructure[END_REF]. More benefits from this include reduction of morbidity, limiting of therapy's side effects, reduction of healthcare cost because of increased compliance to therapy, less car traffic in the cities, reduced greenhouse emissions, less fossil fuel consumption, less air pollution.

For the glaucoma patients in particular, the study involves the Hellenic Telecommunications Organization S.A. (OTE), the Informatics & Telecommunications Department of the National and Kapodistrian University of Athens and the Glaucoma Department of the 2 nd Ophthalmological University Clinic of Athens in Attikon Hospital. The essential aim is to communicate with glaucomatic patients at their home, from the Hospital, both in regular appointments and in case of emergency. Regular appointments include monitoring of their compliance to therapy, eye drop instillation reminding, eye drop instillation training and display [START_REF] Patel | Compliance in Patients prescribed Eyedrops for Glaucoma[END_REF], common examination with a high definition video-to-video communication and even the use of camera snapshots. At the same time, the patient can call the Glaucoma Department in case of emergency for a 24/7 follow-up. This may include cases of a common but very impressive subconjuctival haemorrhage which needs no transportation to the hospital and can be easily diagnosed from the camera, any acute symptoms from the eyes or side effects from therapy, even postsurgical examination. Authorized doctors have also the ability to send communication request to a specific patient, if needed.

LiveCity Telemedicine Platform

The LiveCity Telemedicine platform supports high definition video streaming between an eye doctor and a patient over public Internet. In this end, two different end-user applications, the Doctor Plugin and the Patient Plugin, have been designed and developed to address the needs of the doctor and the patient respectively. The plugin allows to doctor to establish high definition quality video-to-video communication with a chosen patient. The core functionality of the application is provided by a simple graphical user interface. Specifically, the following functionality is supported:

• Connect and Disconnect: The doctor can register the client software in the LiveCity network and obtain access to the LiveCity services by pressing the button Connect and filling-in his certified credentials. By pressing the button Disconnect the doctor unregisters his client from the LiveCity network. • Call: This button allows the doctor to establish video-to-video communication with patients that are currently connected to the LiveCity network.

• Notifications: The notifications area is used to inform the doctor that a patient requires his attention. When a patient issues a call request the application shows the caller's name in the notifications area informing the doctor.

• Feedback: This button provides the doctor the ability to report to the developers issues arising during the application use. The doctor can issue a report for a bug or unexpected application behavior providing a short description of the problem. • Adv. Settings: Provides a set of additional configurations that extend the overall flexibility of the application. Through these configurations the doctor can change the network parameters of the application, determine new video and audio devices and even define the video resolution. During an active video session the doctor can manually adjust the settings of his own video resolution. Through the Adv. Settings the doctor can choose between four individual video profiles: platinum (1080p video streaming), gold (720p video streaming), silver (480p video streaming) and bronze (360p video streaming). In addition, the doctor can adjust the volume, contrast, brightness and saturation of the remote video. This functionality is available by pressing the button Controls. Moreover the doctor may save a snapshot of the received video by pressing the button Screenshot. The image is stored in the LiveCity database and can be used later by the doctors to assist the patient examination. The doctor may change the resolution of the streamed video using the button Remote Video. Finally, the doctor can terminate the call session by pressing the button Hang up.

The LiveCity Telemedicine Patient Plugin is a simple and lightweight application used by the patients and it mainly targets the inexperienced users. It provides exactly the same high definition video-to-video communication profiles and the same core functionality of the Hospital side plugin. It should be noted however, that the Patient Plugin does not provide the same call functionality. By pressing the call button the patient application sends a notification to the doctor application. Thus, the doctors can initiate a call, so that they have the full control of the video communication establishment.

The patient's access to the v2v service is realized through a fixed and low-cost xDSL connection. In addition, at the hospital side, a high quality and bandwidth vDSL line has been established with the network provider for ensuring high quality video delivery to the medical personnel. The upload bandwidth utilization of the patient and, as a consequence, the download utilization of the doctor, is nearly linear at 1,3Mbps. On the other hand, the upload utilization of the doctor is gradually increasing up to 3Mbps, due to the additional traffic generated by the doctor movement during examination. Patients are equipped with common laptops supplied with the software developed for the LiveCity e-Health Project and with individual web cam. Camera snapshots have reached a quality of analysis better than the human eye and sometimes equal to that of an examination slitlamp and can even detect a contact lens wearer (as shown on Fig. 1).

Telemonitoring Use Case for Glaucoma Patients

The telemedicine plugin has been developed from the Informatics Department of the University of Athens and used from the Attikon Hospital in practise including: patient's medical history, baseline slit-lamp examination, intraocular pressure measurements, list of all available anti glaucoma drugs, individual file for each patient with his previous appointment findings, comments and eye snapshots.

The technical part has absorbed most of the preparation time for this use case, allowing for only a short period for the patients' telemonitoring up to now. Training of the patients for the use of laptops, the web cam and the software is necessary, despite the fact that both the hardware and the software are user friendly. This is due to the geriatric patients [START_REF] Gurwitz | Treatment for Glaucoma: Adherence by the Elderly[END_REF] and their limited experience with the use of computers and Internet. Regular appointments are weekly and more often in the first month. The doctor-patient communication scenario for the eye telemonitoring is shown in Table 1.

For quality control we have decided to include in the study patients with borderline control of their glaucoma, with the purpose to improve the results of conservative therapy via increased compliance. Also, advanced stage patients are included in the study group with the aim to postpone surgical treatment through closer follow-up. Numerical measurements like initial and intermediate intraocular pressure values, number of drugs and the number of eye drops used for each eye are monitored throughout follow-up, in order to reach medical conclusions. Also, record is kept for the number of regular appointments, emergency calls and the number of visits that have been avoided because of video-to-video telemonitoring, for the final evaluation ( [START_REF] Tsai | Medication Adherence in Glaucoma: Approaches for Optimizing Patient Compliance[END_REF], [START_REF] Zimmerman | Facilitating Patient Compliance in Glaucoma Therapy[END_REF]). Subjective satisfaction report of each patient and doctor for the program and the quality of the video is asked. An unavoidable two (2) second delay in sound and video image has been noticed during the v2v communication with the patients. Because of the advanced technical infrastructure needed for the program and the cost for each patient included in this, so far only 2 patients (females, 70 and 81 years old respectively) have been enrolled and 2 more have been recruited and waiting for the connectivity establishment. A control group for comparison, with similar demographic characteristics but without access to LiveCity, has been formed. Because of the small number of participants so far, no comparative conclusions can be reached. Both the enrolled patients are scheduled for cataract extraction in the next 6 months and postoperative examination with video-to-video communication will be assessed (One patient is treated for glaucoma since 10 years with one medication -the second patient is newly diagnosed and under triple therapy).

Conclusion

Telemonitoring of glaucoma patients with high definition video-to-video communication is a novel approach. Various imaging examinations exist in everyday practice in Ophthalmology and the bases of the ophthalmological diagnosis. Glaucoma patients besides being suitable for tele-examination with high definition video and imaging have also a record in noncompliance to therapy. Telemonitoring is expected to improve training, reminding, correct instillation of eye drops and therefore compliance to therapy. Existing video platforms candidates for realizing v2v services (e.g. Skype, Oovoo) do not offer any facility to integrate additional features to support such e-health use cases. The LiveCity project develops a user-friendly software plugin that can be easily used in wide scale for community connection with the reference Hospital in smart cities [START_REF] Merentitis | Virtualization as a Driver for the Evolution of the Internet of Things: Remaining Challenges and Opportunities Towards Smart Cities[END_REF]. A larger number of will be enrolled in the project in the months for deriving more accurate statistical results.

Fig. 1 .

 1 Fig.1. Eye monitoring camera snapshot.

Table 1 .

 1 Scenario of Doctor-Patient Communication in the LiveCity project.

	Questions of Regular	Questions of Emergency Call	Additional Questions
	Appointments		for the First Call
	General condition of the	What is the cause of the call?	Ease of use of the
	treated eye.		hardware/software.
	Remark any troublesome	When did the disturbing	Level of satisfaction
	symptoms after starting	symptoms appear?	with the new type of
	treatment		communication.
	Difficulty in applying eye	What is the duration of the
	drops?	symptoms?
	Demonstrate eye to the	Is there any decrease in
	camera.	vision?
	Application of eye drops	Feeling any pain?
	demo.
	Follow instructions for	Demonstrate eye to camera.
	implementing drip-hours?
	Confirm details for next	Possible questions from the
	appointment.	patient.
	Possible questions from	Confirm details for next
	patient.	appointment.

Acknowledgments:

The present article has been structured in the context of the LiveCity ("Live Video-to-Video Supporting Interactive City Infrastructure") European Research Project and has been supported by the Commission of the European Communities -DG CONNECT (FP7-ICT-PSP, Grant Agreement No.297291).