Gemeinsamer Workshop von Universitaetsrechenzentrum und Professur "Rechnernetze und verteilte Systeme" der Fakultaet fuer Informatik der TU Chemnitz. Workshop-Thema: Mobilitaet Technik und Anwendungsmöglichkeiten des Mobilfunkstandards der 3. Generation unter Einbeziehung von Vorgänger-, Alternativ-, sowie Nachfolgesystemen.

Vortrag zu den Themen: * mobiles Internet mit UMTS * GPS und digitale Bilder * Einstieg in die Google Maps API

During the last decade, the data rates provided by mobile networks have improved to the point that it is now feasible to provide richer services, such as streaming multimedia, to mobile users. However, due to factors such as radio interference and cell load, the throughput available to a client varies over time. If the throughput available to a client decreases below the media’s bit rate, the client’s buffer will eventually become empty. This causes the client to enter a period of rebuffering, which degrades user experience. In order to avoid this, a streaming server may provide the media at different bit rates, thereby allowing the media’s bit rate (and quality) to be modified to fit the client’s bandwidth. This is referred to as adaptive streaming. The aim of this thesis is to devise an algorithm to find the media quality most suitable for a specific client, focusing on how to detect that the user is able to receive content at a higher rate. The goal for such an algorithm is to avoid depleting the client buffer, while utilizing as much of the bandwidth available as possible without overflowing the buffers in the network. In particular, this thesis looks into the difficult problem of how to do adaptation for live content and how to switch to a content version with higher bitrate and quality in an optimal way. This thesis examines if existing adaptation mechanisms can be improved by considering the characteristics of different mobile networks. In order to achieve this, a study of mobile networks currently in use has been conducted, as well as experiments with streaming over live networks. The experiments and study indicate that the increased available throughput can not be detected by passive monitoring of client feedback. Furthermore, a higher data rate carrier will not be allocated to a client in 3G networks, unless the client is sufficiently utilizing the current carrier. This means that a streaming server must modify its sending rate in order to find its maximum throughput and to force allocation of a higher data rate carrier. Different methods for achieving this are examined and discussed and an algorithm based upon these ideas was implemented and evaluated. It is shown that increasing the transmission rate by introducing stuffed packets in the media stream allows the server to find the optimal bit rate for live video streams without switching up to a bit rate which the network can not support. This thesis was carried out during the summer and autumn of 2008 at Ericsson Research, Multimedia Technologies in Kista, Sweden. / Under det senaste decenniet har överföringshastigheterna i mobilnätet ökat så pass mycket att detnu är möjligt att erbjuda användarna mer avancerade tjänster, som till exempel strömmandemultimedia. I mobilnäten varierar dock klientens bandbredd med avseende på tiden på grund avfaktorer som störningar på radiolänken och lasten i cellen. Om en klients överföringshastighetsjunker till mindre än mediets bithastighet, kommer klientens buffert till slut att bli tom. Dettaleder till att klienten inleder en period av ombuffring, vilket försämrar användarupplevelsen. Föratt undvika detta kan en strömmande server erbjuda mediet i flera olika bithastigheter, vilket gördet möjligt för servern att anpassa bithastigheten (och därmed kvalitén) till klientens bandbredd.Denna metod kallas för adaptive strömning. Syftet för detta examensarbete är att utveckla en algoritm, som hittar den bithastighet som är bästlämpad för en specifik användare med fokus på att upptäcka att en klient kan ta emot media avhögre kvalité. Målet för en sådan algoritm är att undvika att klientens buffert blir tom ochsamtidigt utnyttja så mycket av bandbredden som möjligt utan att fylla nätverksbuffertarna. Merspecifikt undersöker denna rapport det svåra problemet med hur adaptering för direktsänd mediakan utföras. Examensarbetet undersöker om existerande adapteringsmekanismer kan förbättras genom attbeakta de olika radioteknologiers egenskaper. I detta arbete ingår både en studie avradioteknologier, som för tillfället används kommersiellt, samt experiment med strömmandemedia över dessa. Resultaten från studien och experimenten tyder på att ökad bandbredd inte kanupptäckas genom att passivt övervaka ”feedback” från klienten. Vidare kommer inte användarenatt allokeras en radiobärare med högre överföringshastighet i 3G-nätverk, om inte den nuvarandebäraren utnyttjas maximalt. Detta innebär att en strömmande server måste variera sinsändningshastighet både för att upptäcka om mer bandbredd är tillgänglig och för att framtvingaallokering av en bärare med högre hastighet. Olika metoder för att utföra detta undersöks ochdiskuteras och en algoritm baserad på dessa idéer utvecklas. Detta examensarbete utfördes under sommaren och hösten 2008 vid Ericsson Research,Multimedia Technologies i Kista, Sverige.

As the coverage of modern wireless technologies expands, today’s mobile phones and PDAs often have a range of heterogeneous networks to which they may connect. It would benefit mobile applications to use the network which best corresponds to its need. However, making the handovers between networks transparent to allow communication sessions to survive is not trivial as the TCP/IP suite, used by most networking applications today, was initially not designed with mobility in mind. A Vinnova founded research project at Saab (together with associates1) has found that it could prove advantageous to monitor network quality together with the application’s needs and make intelligent decisions regarding what network to use. An algorithm for network classification and evaluation has been proposed. This thesis examined prerequisites and methods for implementing adaptive network connectivity through transparent handovers for mobile devices, resulting in a tentative model to demonstrate the mentioned research results. The prototype, implemented as a user space middleware, utilizes UDP encapsulation and a per-packet basis link evaluation, resulting in small overhead and fast context adaptation. Link monitoring ensures that server and clients are constantly updated about network quality and availability. The prototype yielded transparent handovers between networks, with short handover delays, at the cost of reduced performance for fast networks. 1 Blekinge Institute of Technology, Swedish National Testing and Research Institute, and SwedishRoad Administration / Täckningen av trådlösa nätverk ökar konstant, och dagens mobiltelefoner och handdatorer har ofta ett antal olika nätverk de kan ansluta till. Det skulle vara fördelaktigt för mobila applikationer att använda det nätverk som bäst passar dess behov. Att göra övergångarna mellan dessa nätverk transparenta så att pågående kommmunikationssessioner kan fortgå är dock inte helt trivialt, då TCP/IP protokollen från början inte var tänkta för mobila enheter. Ett av Vinnova finansierat forskningsprojekt utfört på Saab med flera1 har undersökt möjligheterna att övervaka kvaliteten på olika trådlösa nätverk samt kraven från applikationerna, och med detta som grund utföra intelligenta beslut om vilket nätverk som ska utnyttjas. En algoritm för att utföra dessa beslut har också föreslagits. Detta examensarbete undersökte möjligheterna för att implementera adaptiv nätverksroaming genom transparenta övergångar för mobila enheter, och resulterade i en demonstrator, som även kan visa resultaten från den nämnda forskningen. Prototypen, implementerad som en "middleware", använder UDP tunnling och en per-paket nätverksutvärdering, vilket resulterade i liten overhead och snabb anpassning till nya kommunikationssituationer. En länkövervakare såg till att server och klienter alltid var uppdaterade om kvaliteten och tillgängligheten av olika nätverk. Prototypen gav totalt transparenta övergångar mellan nätverk med relativt korta fördröjningar, med nackdelen av viss reducerad prestanda för snabba nätverk. 1 Blekinges Tekniska Högskola, Sveriges Provnings – och Forskningsinstitut, samt Vägverket

Tremendous emphasis has been placed on wireless technologies recently and it is expected that mobile communications will become an even bigger key driver for growth and innovation in the near future. The purpose of this paper is to study the securing, development, integration and implementation of an always on, always available, and accessible from anywhere secure wireless communication environment. Our analysis of the different wireless technologies reveals that a number of obstacles have to be managed before truly transparent wireless public data consumer offering is available. Our concern revolves around the technical development and implementation efforts of integrated wireless technologies enveloped with management processes of change and evolution. Wireless technologies have influenced our daily lives and will undoubtedly continue to play a significant role in the future. This dissertation focuses on the interoperation of wireless technologies, exploring, evaluating and presenting representations of secure, fully integrated wireless environments. The purpose is to find a cost effective, open, viable, sustainable consumer orientated high data speed offering which not only adheres to basic security requirements but surpasses it. By bringing the network to the subscriber we generate an “always-on” and “always-available” solution for data requirements fulfilling an ever increasing human demand for access to resources anywhere, anytime. A background literature of various wireless technologies, techniques and value added services is provided. An approach for the securing of critical content over wireless links in chapter seven provides a basis for access by position concepts presented in chapter eight. This secure approach to location-aware mobile access control is an essential security enhancement in the integration and interoperation models illustrated in chapter nine. These models, appropriately named SWARM 1 and SWARM 2 (System for Wireless and Roaming Mobility), illustrate different approaches to achieving a secure, fully coherent, consumer orientated, wireless data communications environment. / Dissertation (MSc (Computer Science))--University of Pretoria, 2003. / Computer Science / unrestricted

no / This paper is focused on the design of an adaptive Connection Admission Control (CAC) algorithm for a Universal Mobile Telecommunication System (UMTS) based satellite system with variable link capacity. The main feature of the proposed algorithm is to maximize the resource utilization by adapting to the link conditions and the antenna gain of the users. The link quality of the user may vary depending on the weather condition, user mobility and any other propagation factors. The algorithm is compared against a non-adaptive admission control algorithm under different test cases. The proposed CAC algorithm is simulated using MATLAB and the performance results are obtained for a mix of multimedia traffic classes such as video streaming, web browsing, netted voice and email. The simulation results indicate a higher system performance in terms of the blocking ratio and the number of admitted connections.

Silicon CMOS Technology is now the preferred process for low power wireless communication devices, although currently much noisier and slower than comparable processes such as SiGe Bipolar and GaAs technologies. However, due to ever-reducing gate sizes and correspondingly higher speeds, higher Ft CMOS processes are increasingly competitive, especially in low power wireless systems such as Bluetooth, Wireless USB, Wimax, Zigbee and W-CDMA transceivers. With the current 32 nm gate sized devices, speeds of 100 GHz and beyond are well within the horizon for CMOS technology, but at a reduced operational voltage, even with thicker gate oxides as compensation. This thesis investigates newer techniques, both from a systems point of view and at a circuit level, to implement an efficient transceiver design that will produce a more sensitive receiver, overcoming the noise disadvantage of using CMOS Silicon. As a starting point, the overall components and available SoC were investigated, together with their architecture. Two novel techniques were developed during this investigation. The first was a high compression point LNA design giving a lower overall systems noise figure for the receiver. The second was an innovative means of matching circuits with low Q components, which enabled the use of smaller inductors and reduced the attenuation loss of the components, the resulting smaller circuit die size leading to smaller and lower cost commercial radio equipment. Both these techniques have had patents filed by the University. Finally, the overall design was laid out for fabrication, taking into account package constraints and bond-wire effects and other parasitic EMC effects.

In recent years, there has been an exponential growth in the use of multimedia applications. A satellite system offers great potential for multimedia applications with its ability to broadcast and multicast a large amount of data over a very large area as compared to a terrestrial system. However, the limited transmission capacity along with the dynamically varying channel conditions impedes the delivery of good quality multimedia service in a satellite system which has resulted in research efforts for deriving efficient radio resource management techniques. This issue is addressed in this thesis, where the main emphasis is to design a CAC framework which maximizes the utilization of the scarce radio resources available in the satellite and at the same time increases the performance of the system for a UMTS based satellite system supporting unicast and multicast traffic. The design of the system architecture for a UMTS based satellite system is presented. Based on this architecture, a CAC framework is designed consisting of three different functionalities: the admission control procedure, the retune procedure and the pre-emption procedure. The joint use of these functionalities is proposed to allow the performance of the system to be maintained under congestion. Different algorithms are proposed for different functionalities; an adaptive admission control algorithm, a greedy retune algorithm and three pre-emption algorithms (Greedy, SubSetSum, and Fuzzy). A MATLAB simulation model is developed to study the performance of the proposed CAC framework. A GUI is created to provide the user with the flexibility to configure the system settings before starting a simulation. The configuration settings allow the system to be analysed under different conditions. The performance of the system is measured under different simulation settings such as enabling and disabling of the two functionalities of the CAC framework; retune procedure and the pre-emption procedure. The simulation results indicate the CAC framework as a whole with all the functionalities performs better than the other simulation settings.

The third generation of mobile communication systems introduce interactive Multicast and Unicast multimedia services at a fast data rate of up to 2 Mbps and is expected to complete the globalization of the mobile telecommunication systems. The implementation of these services on satellite systems, particularly for broadcast and multicast applications to complement terrestrial services is ideal since satellite systems are capable of providing global coverage in areas not served by terrestrial telecommunication services. However, the main bottleneck of such systems is the scarcity of radio resources for supporting multimedia applications which has resulted in the rapid growth in research efforts for deriving efficient radio resource management techniques. This issue is addressed in this thesis, where the main emphasis is to design a dynamic scheduling framework and algorithm that can improve the overall performance of the radio resource management strategy of a UMTS compatible satellite network, taking into account the unique characteristics of wireless channel conditions. This thesis will initially be focused on the design of the network and functional architecture of a UMTS -compatible satellite network. Based on this architecture, an effective scheduling framework is designed, which can provide different types of resource assigning strategies. A functional model of scheduler is defined to describe the behaviours and interactions between different functional entities. An OPNET simulation model with a complete network protocol stack is developed to validate the performance of the scheduling algorithms implemented in the satellite network. Different types of traffic are considered for the OPNET simulation, such as the Poisson Process, ONOFF Source and Self Similar Process, so that the performance of scheduling algorithm can be analyzed for different types of services. A novel scheduling algorithm is proposed to optimise the channel utilisation by considering the characteristics of the wireless channel, which are bursty and location dependent. In order to overcome the channel errors, different code rates are applied for the user under different channel conditions. The proposed scheduling algorithm is designed to give higher priority to users with higher code rate, so that the throughput of network is optimized and at the same time, maintaining the end users¿ service level agreements. The fairness of the proposed scheduling algorithm is validated using OPNET simulation. The simulation results show that the algorithm can fairly allocate resource to different connections not only among different service classes but also within the same service class depending on their QoS attributes. / Inmarsat Global Ltd. BGAN and the European Space Agency (ESA)

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