30 research outputs found
Quality of service management for non-guaranteed networks
The increasing dominance of multimedia communication posed new requirements for the underlying systems. Multimedia data, formally called continuous media, has time constraints that impose real time limitations for their transmission. Certain levels of service, called Quality of Service (QoS), need to be considered when handling continuous media. The present work utilizes QoS concepts for networks that do not have inherent QoS support. The thesis aims at verifying the possibility of having QoS-controlled communication on non-guaranteed networks. A basic QoS architecture is designed where already existing QoS concepts are adapted to work with non-guaranteed networks. The architecture provides the facilities of QoS specification, mapping, admission, maintenance, monitoring and notification. In addition, a new concept for predictive QoS admission is introduced. The proposed architecture was verified using a prototype system. The results showed an increased percentage of continuous media that arrive on time to their receivers (good put) with higher network loads. The increased good put was at the expense of high network overhead
Network-Integrated Multimedia Middleware, Services, and Applications
Today, there is a strong trend towards networked multimedia devices. However, common multimedia software architectures are restricted to perform all processing on a single system. Available software infrastructures for distributed computing — commonly referred to as middleware — only partly provide the facilities needed for supporting multimedia in distributed and dynamic environments. Approaches from the research community only focus on specific aspects and do not achieve the coverage needed for a full-featured multimedia middleware solution. The Network-Integrated Multimedia Middleware (NMM) presented in this thesis considers the network as an integral part. Despite the inherent heterogeneity of present networking and device technologies, the architecture allows to extend control and cooperation to the network and enables the development of distributed multimedia applications that transparently use local and remote components in combination. The base architecture of this middleware is augmented by several middleware services that especially aim at providing additional support for developing complex applications that involve mobile users and devices. To this end, previously not available services and corresponding abstractions are proposed, realized, and evaluated. The performance and applicability of the developed middleware and its additional services are demonstrated by describing different realized application scenarios.Eine wachsende Anzahl von Multimedia-Geraeten verfuegt heute bereits ueber Netzwerkschnittstellen. Verfueugbare Multimedia Software-Architekturen beschraeanken jedoch die gesamte Datenverarbeitung auf ein einzelnes System. Verbreitete Software-Infrastrukturen fuer Verteilte Systeme — ueblicherweise Middleware genannt — bieten nur teilweise die Eigenschaften, die fuer die Multimedia-Datenverarbeitung in vernetzten und dynamischen Umgebungen benoetigt werden. Ansaetze aus der Forschung behandeln nur spezielle Teilaspekte und erreichen deshalb nicht den Funktionsumfang einer vollwertigen Middleware fuer Multimedia.
Die in dieser Arbeit beschriebene Netzwerk-Integrierte Multimedia Middleware
(NMM) betrachtet das Netzwerk als integralen Bestandteil. Die Architektur erlaubt trotz der inhaerenten Heterogenitaet der vorhandenen Netzwerk- und Geraetetechnologie die Kontrolle und das Zusammenspiel von Systemen auf das Netzwerk auszuweiten.
Dies ermoeglicht die Entwicklung verteilter Multimedia-Anwendungen, die transparent lokale und entfernte Komponenten zusammen einsetzen. Die Kernarchitektur dieser Middleware wird durch verschiedene Dienste erweitert, die speziell die Realisierung komplexer Anwendungsszenarien mitmobilen Geraeten und Benutzern unterstuetzt. Insbesondere werden neue, bisher nicht vorhandene Middleware-Dienste und zugehoerige Abstraktionen vorgeschlagen, realisiert und evaluiert. Anhand verschiedener Anwendungsszenarien
wird die Leistungfaehigkeit, die Effizienz und die praktische Relevanz der entwickelten Middleware und der ergaenzenden Dienste demonstriert
Techniques and Patterns for Safe and Efficient Real-Time Middleware
Over 90 percent of all microprocessors are now used for real-time and embedded applications. The behavior of these applications is often constrained by the physical world. It is therefore important to devise higher-level languages and middleware that meet conventional functional requirements, as well as dependably and productively enforce real-time constraints. Real-Time Java is emerging as a safe, real-time environment. In this thesis we use it as our experimentation platform; however, our findings are easily adapted to other similar platforms. This thesis provides the following contributions to the study of safe and efficient real-time middleware. First, it identifies potential bottlenecks and problem with respect to guaranteeing real-time performance in middleware. Second, it presents a series of techniques and patterns that allow the design and implementation of safe, predictable, and highly efficient real-time middleware. Third, it provides a set of architectural and design patterns that application developers can use when designing real-time systems. Finally, it provides a methodology for evaluating the merits and benefits of real-time middleware. Empirical results are presented using that methodology for the techniques presented in this thesis. The methodology helps compare the performance and predictability of general, real-time middleware platforms
Deployment and operational aspects of rural broadband wireless access networks
Broadband speeds, Internet literacy and digital technologies have been steadily evolving
over the last decade. Broadband infrastructure has become a key asset in today’s
society, enabling innovation, driving economic efficiency and stimulating cultural inclusion.
However, populations living in remote and rural communities are unable to
take advantage of these trends. Globally, a significant part of the world population is
still deprived of basic access to the Internet.
Broadband Wireless Access (BWA) networks are regarded as a viable solution
for providing Internet access to populations living in rural regions. In recent years,
Wireless Internet Service Providers (WISPs) and community organizations around the
world proved that rural BWA networks can be an effective strategy and a profitable
business.
This research began by deploying a BWA network testbed, which also provides
Internet access to several remote communities in the harsh environment of the Scottish
Highlands and Islands. The experience of deploying and operating this network
pointed out three unresolved research challenges that need to be addressed to ease
the path towards widespread deployment of rural BWA networks, thereby bridging
the rural-urban broadband divide. Below, our research contributions are outlined with
respect to these challenges.
Firstly, an effective planning paradigm for deploying BWA networks is proposed:
incremental planning. Incremental planning allows to anticipate return of investment
and to overcome the limited network infrastructure (e.g., backhaul fibre links) in rural
areas. I have developed a software tool called IncrEase and underlying network
planning algorithms to consider a varied set of operational metrics to guide the operator
in identifying the regions that would benefit the most from a network upgrade,
automatically suggesting the best long-term strategy to the network administrator.
Second, we recognize that rural and community networks present additional issues
for network management. As the Internet uplink is often the most expensive part
of the operational expenses for such deployments, it is desirable to minimize overhead
for network management. Also, unreliable connectivity between the network operation
centre and the network being managed can render traditional centralized management
approaches ineffective. Finally, the number of skilled personnel available to maintain
such networks is limited. I have developed a distributed network management platform called Stix for BWA networks, to make it easy to manage such networks
for rural/community deployments and WISPs alike while keeping the network management
infrastructure scalable and flexible. Our approach is based on the notions of
goal-oriented and in-network management: administrators graphically specify network
management activities as workflows, which are run in the network on a distributed set
of agents that cooperate in executing those workflows and storing management information.
The Stix system was implemented on low-cost and small form-factor embedded
boards and shown to have a low memory footprint.
Third, the research focus moves to the problem of assessing broadband coverage
and quality in a given geographic region. The outcome is BSense, a flexible framework
that combines data provided by ISPs with measurements gathered by distributed
software agents. The result is a census (presented as maps and tables) of the coverage
and quality of broadband connections available in the region of interest. Such information
can be exploited by ISPs to drive their growth, and by regulators and policy
makers to get the true picture of broadband availability in the region and make informed
decisions. In exchange for installing the multi-platform measurement software
(that runs in the background) on their computers, users can get statistics about their
Internet connection and those in their neighbourhood.
Finally, the lessons learned through this research are summarised. The outcome is
a set of suggestions about how the deployment and operation of rural BWA networks,
including our own testbed, can be made more efficient by using the proper tools. The
software systems presented in this thesis have been evaluated in lab settings and in real
networks, and are available as open-source software
Architectural support for ubiquitous access to multimedia content
Tese de doutoramento. Engenharia Electrotécnica e de Computadores (Telecomunicações). Faculdade de Engenharia. Universidade do Porto. 200
IP Mobility in Wireless Operator Networks
Wireless network access is gaining increased heterogeneity in terms of the types of IP capable access technologies. The access network heterogeneity is an outcome of incremental and evolutionary approach of building new infrastructure. The recent success of multi-radio terminals drives both building a new infrastructure and implicit deployment of heterogeneous access networks. Typically there is no economical reason to replace the existing infrastructure when building a new one. The gradual migration phase usually takes several years.
IP-based mobility across different access networks may involve both horizontal and vertical handovers. Depending on the networking environment, the mobile terminal may be attached to the network through multiple access technologies. Consequently, the terminal may send and receive packets through multiple networks simultaneously. This dissertation addresses the introduction of IP Mobility paradigm into the existing mobile operator network infrastructure that have not originally been designed for multi-access and IP Mobility.
We propose a model for the future wireless networking and roaming architecture that does not require revolutionary technology changes and can be deployed without unnecessary complexity. The model proposes a clear separation of operator roles: (i) access operator, (ii) service operator, and (iii) inter-connection and roaming provider. The separation allows each type of an operator to have their own development path and business models without artificial bindings with each other. We also propose minimum requirements for the new model.
We present the state of the art of IP Mobility. We also present results of standardization efforts in IP-based wireless architectures. Finally, we present experimentation results of IP-level mobility in various wireless operator deployments.Erilaiset langattomat verkkoyhteydet lisääntyvät Internet-kykyisten teknologioiden muodossa. Lukuisten eri teknologioiden päällekkäinen käyttö johtuu vähitellen ja tarpeen mukaan rakennetusta verkkoinfrastruktuurista. Useita radioteknologioita (kuten WLAN, GSM ja UMTS) sisältävien päätelaitteiden (kuten älypuhelimet ja kannettavat tietokoneet) viimeaikainen kaupallinen menestys edesauttaa uuden verkkoinfrastruktuurin rakentamista, sekä mahdollisesti johtaa verkkoteknologioiden kirjon lisääntymiseen. Olemassa olevaa verkkoinfrastruktuuria ei kaupallisista syistä kannata korvata uudella teknologialla yhdellä kertaa, vaan vaiheittainen siirtymävaihe kestää tyypillisesti useita vuosia.
Internet-kykyiset päätelaitteet voivat liikkua joko saman verkkoteknologian sisällä tai eri verkkoteknologioiden välillä. Verkkoympäristöstä riippuen liikkuvat päätelaitteet voivat liittyä verkkoon useiden verkkoyhteyksien kautta. Näin ollen päätelaite voi lähettää ja vastaanottaa tietoliikennepaketteja yhtäaikaisesti lukuisia verkkoja pitkin. Tämä väitöskirja käsittelee Internet-teknologioiden liikkuvuutta ja näiden teknologioiden tuomista olemassa oleviin langattomien verkko-operaattorien verkkoinfrastruktuureihin. Käsiteltäviä verkkoinfrastruktuureita ei alun perin ole suunniteltu Internet-teknologian liikkuvuuden ja monien yhtäaikaisten yhteyksien ehdoilla.
Tässä työssä ehdotetaan tulevaisuuden langattomien verkkojen arkkitehtuurimallia ja ratkaisuja verkkovierailujen toteuttamiseksi. Ehdotettu arkkitehtuuri voidaan toteuttaa ilman mittavia teknologisia mullistuksia. Mallin mukaisessa ehdotuksessa verkko-operaattorin roolit jaetaan selkeästi (i) verkko-operaattoriin, (ii) palveluoperaattoriin ja (iii) yhteys- sekä verkkovierailuoperaattoriin. Roolijako mahdollistaa sen, että kukin operaattorityyppi voi kehittyä itsenäisesti, ja että teennäiset verkkoteknologiasidonnaisuudet poistuvat palveluiden tuottamisessa. Työssä esitetään myös alustava vaatimuslista ehdotetulle mallille, esimerkiksi yhteysoperaattorien laatuvaatimukset.
Väitöskirja esittelee myös liikkuvien Internet-teknologioiden viimeisimmän kehityksen. Työssä näytetään lisäksi standardointituloksia Internet-kykyisissä langattomissa arkkitehtuureissa