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

O crescente aumento da demanda de tráfego nas redes celulares vem aumentando a necessidade de uma melhor utilização dos recursos do sistema, já que sua expansão é custosa. Nas estações rádio base (ERB), a disponibilidade de largura de faixa de freqüências é limitada e desta maneira, em uma rede de comunicação móvel celular, o controle de admissão de chamadas exerce grande influência no desempenho do sistema, pois determina a utilização de banda das ERBs e se uma determinada quantidade de recursos (banda) será alocado ou não para uma determinada chamada. O desempenho da rede pode ser atrelado a determinados parâmetros, como a probabilidade de bloqueio de novas chamadas, probabilidade de bloqueio de chamadas handoff e a utilização de banda da rede. Este trabalho propõe um controle de admissão de chamadas que, no atendimento de uma chamada, faz o empréstimo de banda de chamadas em andamento na célula no caso de banda insuficiente. O sistema adota um mecanismo heurístico que determina a banda disponível para novas chamadas conforme os valores de certos parâmetros do sistema. O empréstimo de banda é realizado em chamadas em andamento nas células até níveis mínimos estabelecidos para cada tipo de chamada, que se diferenciam pelas necessidades de banda de cada uma. O algoritmo foi aplicado às bandas e características de uma rede de terceira geração (3G), que possui chamadas de voz, videoconferência, interação multimídia, e-mail, downloads e transferência de arquivos e a uma rede GSM/GPRS (global system for mobile communications/ general packet radio service), que possui chamadas de voz e de dados. Os resultados mostram melhorias na probabilidade de bloqueio de novas chamadas, probabilidade de bloqueio de handoff e na utilização de banda do sistema. / The recent growth in traffic loads in cellular networks has seen the need for a better use of system resources as its expansion is expensive. In the base transceiver station (BTS), the bandwidth availability is limited. Thus, in cellular networks the call admission control greatly influences the system performance because it determines the bandwidth use of the BTSs and if an amount of resources will or will not be allocated to a call. The network performance can be evaluated by parameters such as blocking probability of new calls, dropping probability of handoff calls and bandwidth use. This work proposes a call admission control that carries out the bandwidth borrowing when a call arrives and there is not enough bandwidth. The system makes use of a heuristic mechanism that determines the available bandwidth for the new calls according to some parameter values of the system. The bandwidth borrowing is applied to the cell ongoing calls until the minimum levels for each type are met. The algorithm was applied to the bandwidths and characteristics of a third generation cellular network, which supports voice calls, videoconference, multimedia interaction, e-mails, downloads and file transfers. It was also applied to a GSM/GPRS (global system for mobile communications/ general packet radio service), which supports voice and data calls. The results show improvements in the blocking probability of new calls, dropping probability of handoff calls and in the bandwidth use of the system.

Submitted by Fabio Sobreira Campos da Costa (fabio.sobreira@ufpe.br) on 2017-03-02T14:56:30Z No. of bitstreams: 2 license_rdf: 1232 bytes, checksum: 66e71c371cc565284e70f40736c94386 (MD5) moises.rodrigues-phd.thesis-final-v3.pdf: 4286662 bytes, checksum: 9e67a238c996afd5b50b91cf3c59c86a (MD5) / Made available in DSpace on 2017-03-02T14:56:30Z (GMT). No. of bitstreams: 2 license_rdf: 1232 bytes, checksum: 66e71c371cc565284e70f40736c94386 (MD5) moises.rodrigues-phd.thesis-final-v3.pdf: 4286662 bytes, checksum: 9e67a238c996afd5b50b91cf3c59c86a (MD5) Previous issue date: 2016-10-03 / During the last decades, the world web went from a way to connect a handful of nodes to the means with which people cooperate in search of knowledge, social interaction, and entertainment. Furthermore, our homes and workstations are not the only places where we are connected, the mobile broadband market is present and changing the way we interact with the web. According to Cisco, global network traffic will be three times higher in 2018 than it was in 2013. Real-time entertainment has been and will remain an important part of this growth. However, the internet was not designed to handle such demand and, therefore, there is a need for new technologies to overcome those challenges. Content Delivery Networks (CDN) prove to be an alternative to overcome those challenges. The basic concept is to distribute replica servers scattered geographically, keeping content close to end users. Following CDN’s popularity an increasing number of CDNs, most of them extremely localized, began to be deployed. Furthermore, Cloud Computing emerged, making software and hardware accessible as resources through well-defined interfaces. Using Cloud services, such as distributed IaaS, one could deploy complex CDNs. Despite being the best technology to scale content distribution, there are some scenarios where CDNs may perform poorly, such as flash crowd events. Therefore, we need to study content delivery techniques to efficiently accompany the ever increasing need for content contemplating new possibilities, such as growing the number of smaller localized CDNs and Cloud Computing. Examining given issues this work presents strategies towards improvements in Content Delivery Networks (CDN). We do so by proposing and evaluating algorithms, models and a prototype demonstrating possible uses of such new technologies to improve CDN’s resource management. We present P2PCDNSim, a comprehensive CDN simulator designed to assist researchers in the process of planning and evaluating new strategies. Furthermore, we propose a new dynamic Replica Placement Algorithm (RPA), based on the count of data flows through network nodes, that maintains similar Quality of Experience (QoE) while decreasing cross traffic during flash crowd events. Also, we propose a solution to improve the mobile backhaul’s replica placement flexibility based on SDN. Our experimental results show that the delay introduced by the developed module is less than 5ms for 99% of the packets, which is negligible in today’s LTE networks, and the slight negative impact on streaming rate selection is easily outweighed by the increased flexibility / Durante a última década, a rede mundial de computadores evoluiu de um meio de conexão para um pequeno grupo de nós para o meio de pelo qual pessoas obtém conhecimento, interação social e entretenimento. Além disso, nossas casas e estações de trabalho não são nossos únicos pontos de acesso à rede. De acordo com a Cisco, o tráfego global da rede em 2018 será três vezes maior do que era em 2013. Entretenimento em tempo real tem sido e continuará sendo uma parte importante nesse crescimento. No entanto, a rede não foi projetada para lidar com essa demanda, portanto, existe a necessidade de novas tecnologias para superar tais desafios. Content Delivery Networks (CDN) se mostram como uma boa alternativa para superar esses desafios. Seu conceito básico é distribuir servidores de réplica geograficamente, mantendo assim o conteúdo próximo aos usuários. Seguindo sua popularidade, um número crescente de CDNs, em sua maioria locais, começaram a ser implementadas. Além disso, computação em nuvem surgiu, tornando software e hardware recursos acessíveis através de interfaces bem definidas. Os serviços na nuvem, tais como Infrastructure as a Service (IaaS) distribuídos, tornam possível a implementação de CDNs complexas. Apesar de ser a melhor tecnologia para entrega de conteúdo em termos de escalabilidade, existem cenários que ainda desafiam as CDNs, como eventos de flash crowd. Portanto, precisamos estudar estratégias de entrega de conteúdo para acompanhar de maneira eficiente o constante crescimento na necessidade por conteúdo, aproveitando também as novas possibilidade como, o crescimento de CDNs localizadas e popularização da computação em nuvem. Examinando os problemas levantados, essa tese apresenta estratégias no sentido de melhorar Content Delivery Networks (CDN). Fazemos isso propondo e avaliando algoritmos, modelos e um protótipo demonstrando possíveis usos de tais tecnologias para melhorar o gerenciamento de recursos das CDNs. Apresentamos o P2PCDNSim, um simulador de CDNs planejado para auxiliar pesquisadores no processo de planejamento e avaliação de novas estratégias. Além disso, propomos uma nova estratégia de posicionamento de réplicas dinâmica, baseada na contagem de fluxos de dados passando pelos nós, que mantém uma Quality of Experience (QoE) similar enquanto diminui tráfego entre Autonomous System (AS). Ademais, propomos uma solução baseada em Software Defined Networks (SDN) que aumenta a flexibilidade de posicionamento de servidores réplica dentro do backhaul móvel. Nossos resultados experimentais mostram que o atraso introduzido pelo nosso módulo é menor que 5ms em 99% dos pacotes transmitidos, atraso mínimo nas redes Long-Term Evolution (LTE) atuais.

O crescente aumento da demanda de tráfego nas redes celulares vem aumentando a necessidade de uma melhor utilização dos recursos do sistema, já que sua expansão é custosa. Nas estações rádio base (ERB), a disponibilidade de largura de faixa de freqüências é limitada e desta maneira, em uma rede de comunicação móvel celular, o controle de admissão de chamadas exerce grande influência no desempenho do sistema, pois determina a utilização de banda das ERBs e se uma determinada quantidade de recursos (banda) será alocado ou não para uma determinada chamada. O desempenho da rede pode ser atrelado a determinados parâmetros, como a probabilidade de bloqueio de novas chamadas, probabilidade de bloqueio de chamadas handoff e a utilização de banda da rede. Este trabalho propõe um controle de admissão de chamadas que, no atendimento de uma chamada, faz o empréstimo de banda de chamadas em andamento na célula no caso de banda insuficiente. O sistema adota um mecanismo heurístico que determina a banda disponível para novas chamadas conforme os valores de certos parâmetros do sistema. O empréstimo de banda é realizado em chamadas em andamento nas células até níveis mínimos estabelecidos para cada tipo de chamada, que se diferenciam pelas necessidades de banda de cada uma. O algoritmo foi aplicado às bandas e características de uma rede de terceira geração (3G), que possui chamadas de voz, videoconferência, interação multimídia, e-mail, downloads e transferência de arquivos e a uma rede GSM/GPRS (global system for mobile communications/ general packet radio service), que possui chamadas de voz e de dados. Os resultados mostram melhorias na probabilidade de bloqueio de novas chamadas, probabilidade de bloqueio de handoff e na utilização de banda do sistema. / The recent growth in traffic loads in cellular networks has seen the need for a better use of system resources as its expansion is expensive. In the base transceiver station (BTS), the bandwidth availability is limited. Thus, in cellular networks the call admission control greatly influences the system performance because it determines the bandwidth use of the BTSs and if an amount of resources will or will not be allocated to a call. The network performance can be evaluated by parameters such as blocking probability of new calls, dropping probability of handoff calls and bandwidth use. This work proposes a call admission control that carries out the bandwidth borrowing when a call arrives and there is not enough bandwidth. The system makes use of a heuristic mechanism that determines the available bandwidth for the new calls according to some parameter values of the system. The bandwidth borrowing is applied to the cell ongoing calls until the minimum levels for each type are met. The algorithm was applied to the bandwidths and characteristics of a third generation cellular network, which supports voice calls, videoconference, multimedia interaction, e-mails, downloads and file transfers. It was also applied to a GSM/GPRS (global system for mobile communications/ general packet radio service), which supports voice and data calls. The results show improvements in the blocking probability of new calls, dropping probability of handoff calls and in the bandwidth use of the system.

Environmental change is a fact in today’s society. Temperatures are increasing around the world. A reason for this is thought to be an increase in emissions of carbon dioxide and other hazardous substances.To reduce the load on the environment, it is important that each and every one of us works towards a greener planet. A simple and effective way to reduce the strain on the planet is by recycling. In this project, we have designed a product that will facilitate and streamline recycling.The product uses the microcontroller ATMega328P, whose task is to measure and inform about filling levels in recycling containers with the help of ultrasonic sensors. This data will then be transmitted with GPRS for further processing.The product has a transmitter and a receiver part. The transmitter part amplifies a PWM signal before it is transmitted. The ultrasonic waves reflect against an object before it gets picked up by the receiver part. The receiver part filters and amplifies the reflected signal which is then used to calculate the distance to the object. To make sure that it is the correct distance, the outdoor temperature is used for the calculations.It is a battery-powered product that is designed to withstand extreme temperatures and have a long battery life without allowing the price to be too high. The product is small, compact and discrete product because everything but the GPRS module sits on a 5x5 cm printed circuit board. The product is also cheap. The most expensive parts are the batteries. By making them easily exchangeable it allows for cheaper batteries to be used and therefore also makes the product as a whole cheaper.Through measurements of the needed data the product can streamline the logistics and management of recycling. The users of the product can through this gain an economical and environmental profit.KeywordsUltrasonic, sensor, low energy, battery, microcontroller, transistor amplifier, PCB, GPRS, sustainability, M2M, Internet of things. / Miljöförändringar är ett faktum i dagens samhälle. Det sker temperaturökningar runt om i världen. En anledning tros vara ett ökat utsläpp av koldioxid och andra miljöfarliga ämnen i naturen.För att minska belastningen på miljön är det viktigt att varje individ arbetar mot en grönare planet. Ett enkelt sätt att minska belastningen på planeten är genom att återvinna. I detta projekt har vi konstruerat en produkt som ska underlätta och effektivisera återvinning.Produkten använder mikrokontrollern ATMega328P, vars uppgift är att mäta och informera om fyllnadsnivåer i behållare med hjälp av ultraljudsensorer. Denna data sänds sedan ut med en GPRS-enhet för vidare behandling.I produkten finns en sändardel som förstärker en PWM-signal innan den sänds ut från produkten. Ultraljudsvågen reflekteras mot ett föremål och mottas sedan av mottagardelen i produkten, som sedan filtrerar och förstärker den reflekterade signalen. Produkten kan sedan beräkna avståndet till föremål genom en mätning och kalkylering av temperaturen på omgivningen och data från ultraljudsmätningen.Produkten är batteridriven och är anpassad för att tåla extrema temperaturer samt ha en lång batterilivslängd utan att priset rinner iväg. Produkten är liten, kompakt och diskret eftersom allt utom GPRS-modulen sitter på ett 5x5 cm kretskort. Produkten är också billig. Batterierna är de dyraste på produkten. Genom att göra batterierna utbytbara tillåter det för användande av billigare batterier, vilket också gör att produkten som helhet sjunker i pris.De noggranna mätningarna kan genom data som samlats in och distribuerats, effektivisera logistiken och hantering kring återvinning. Användarna av produkten kan genom detta tillhandahålla en ekonomisk och en miljömässig vinst.

Fallolyckor bland äldre är ett stort folkhälsoproblem. Således har det utvecklats en rad olika system för fjärrövervakning av äldre för att möjliggöra en tidig detekte- ring av fallolyckor. Majoriteten av de forskningar som hittills har gjorts inom fallo- lyckor har fokuserat på att utveckla nya mer framgångsrika algoritmer just för att identifiera fall från icke-fall. Trots det visar statistiken att dödsfall och skador orsa- kade av fallolyckor ökar för varje år i samband med den ökande andel äldre perso- ner i befolkningen. Detta examensarbete handlar om att förbättra nuvarande falldetekteringsanord- ningar genom att täcka de brister och tillgodose de behov som finns i nuvarande tekniker. De förbättringar som har kartlagts är att kunna ge en säkrare bedömning av patientens hälsa och kunna påkalla snabbare hjälpinsats när en fallolycka har inträffat. En annan förbättring är rörelsefriheten för äldre. De ska kunna befinna sig utomhus och ha möjlighet att utföra sina dagliga aktiviteter utan att vara be- gränsade av platspositionen. Sammanfattningsvis kan det konstateras att ett multisensorsystem i form av en prototyp har konstruerats för att täcka de brister som har kartlagts. Utöver att pro- totypen detekterar fall och kroppsrörelser med hjälp av en accelerometersensor innehåller den även en sensor för detektering av livstecken i from av EKG. Den in- nehåller dessutom cellulära och trådlösa nätverksanslutningar i form av GPRS och Wi-Fi för att möjliggöra rörelsefriheten hos äldre. Vidare innehåller prototypen en sensor för GPS som ger information om platsposition. / Accidental falls among the elderly is a major public health problem. As a result, a variety of systems have been developed for remote monitoring of the elderly to permit early detection of falls. The majority of the research that has been done so far in fall accidents has focused on developing new more successful algorithms spe- cifically to identify fall from non-fall. Although the statistics show that mortality and injuries caused by falls are increasing every year in conjunction with the in- creasing proportion of older people in the population. This thesis is about improving the current fall detection devices by covering the gaps and meet the needs of the current fall detection techniques. The improve- ments that have been identified is to provide a secure assessment of the patient's health and be able to call for aid more quickly when a fall occurs. Another im- provement is the mobility for the elderly to be outdoors and have the ability to per- form daily activities without being limited by the location position. In summary it can be said that a multisensor system in form of a prototype has been designed to cover the deficiencies and improvements that have been identi- fied. Apart from detection of falls and body movements through an accelerometer sensor the prototype does also include a sensor for detecting vital signs in form of ECG. It also supports cellular and wireless network communication in form of GPRS and Wi-Fi to enable freedom of movement for the elderly. Furthermore, the prototype includes a sensor for GPS that provides information about location position.

The GSM platform is a extremely successful wireless technology and an unprecedented story of global achievement. The GSM platform is growing and evolving and offers an expanded and feature-rich voice and data enabling services. General Packet Radio Service, (GPRS), will have a tremendous transmission rate, which will make a significant impact on most of the existing services. Additionally, GPRS stands ready for the introduction of new services as operators and users, both business and private, appreciate the capabilities and potential that GPRS provides. Services such as the Internet, videoconferencing and on-line shopping will be as smooth as talking on the phone. Moreover, the capability and ease of access to these services increase at work, at home or during travel. In this research the traffic channel of a GSM system was studied in detail and simulated in order to obtain a performance analysis. Matlab, software from Mathworks, was used for the simulation. Both the forward and the reverse links of a GSM system were simulated. A flat fading model was used to model the channel. Signal to Noise Ratio, (SNR), was the primary metric that was varied during the simulation. All the building blocks for a traffic channel, including a Convolutional encoder, an Interleaver and a Modulator were coded in Matlab. Finally the GPRS system, which is an enhancement of the GSM system for data services was introduced.

<p>The most widely used protocol for providing reliable service and congestion control in the Internet is the Transmission Control Protocol (TCP). When the Internet is moving towards more use in mobile applications it is getting more important to know how TCP works for this purpose.</p><p>One of the technologies used for mobile Internet is the Enhanced General Packet Radio Service (EGPRS) extension to the popular GSM system. This thesis presents a low-level analysis of TCP performance in an EGPRS system and an overview of existing TCP, GSM and EGPRS technologies.</p><p>The bottleneck in an EGPRS system is the wireless link – the connection between the mobile phone and the GSM base station. The data transfer over the wireless link is mainly managed by the complex RLC/MAC protocol.</p><p>In this thesis, simulations were made to identify some problems with running TCP and RLC/MAC together. The simulations were made using existing EGPRS testing software together with a new TCP module. The simulation software is also briefly described in the thesis.</p><p>Additionaly, some suggestions are given in order to enhance performance, both by changing the EGPRS system and by modifying the TCP algorithms and parameters.</p>

Στην εν λόγω εργασία, έγινε μια προσπάθεια καταγραφής του τεχνολογικού τοπίου της τηλεπικοινωνιακής αγοράς, με έμφαση την διαλειτουργικότητα μεταξύ των Δικτύων Κινητής Τηλεφωνίας και των Ασύρματων Δικτύων Δεδομένων και των σχετικών αλλαγών που έχει επιφέρει αυτή η διαλειτουργικότητα, τόσο στις παρεχόμενες υπηρεσίες, όσο και στα εφαρμοζόμενα επιχειρηματικά μοντέλα από πλευράς εταιρειών της συγκεκριμένης αγοράς. Στα πλαίσια αυτής της προσπάθειας, χρειάστηκε να πραγματοποιηθεί μια λεπτομερής καταγραφή των τεχνολογικών εξελίξεων, σε επίπεδο τεχνικών προδιαγραφών και προτύπων, στις παραπάνω δύο κατηγορίες δικτύων, ώστε να καταλήξουμε σε εκείνα τα πρότυπα που πλέον μπορούν να οδηγήσουν στην υλοποίηση δικτύων τα οποία θα χαρακτηρίζονται από τα παρακάτω: • θα είναι ενοποιημένα ώστε οι διαφορετικές τεχνολογικές πλατφόρμες των εταιρειών να λειτουργούν απρόσκοπτα, • θα χαρακτηρίζονται από χαμηλό κόστος, • ο τελικός χρήστης θα μπορεί να είναι συνεχώς συνδεδεμένος με κάποιο δίκτυο ασύρματης πρόσβασης και να απολαμβάνει τις υπηρεσίες που επιθυμεί, οποτεδήποτε και οπουδήποτε. Η δομή της διπλωματικής εργασίας ακολουθεί τον προαναφερθέντα τρόπο σκέψης. Στο 1ο Κεφάλαιο γίνεται μια σύντομη παρουσίαση του στόχου σε επίπεδο τεχνολογιών αλλά και υπηρεσιών, δηλαδή των αναμενόμενων αποτελεσμάτων αυτών των δικτύων νέας γενιάς, στα οποία έχουμε συνηθίσει να αναφερόμαστε ως δίκτυα 4G (4th Generation) ή δίκτυα B3G (Beyond 3G) ή τέλος ως All – IP ασύρματα δίκτυα. Στο 2ο Κεφάλαιο, γίνεται μια λεπτομερής παρουσίαση των Δικτύων Κινητής Τηλεφωνίας από τις πρώτες τους εκδοχές (1G) έως τις πλέον σύγχρονες (3.5G) που έχουν εμφανιστεί μέχρι σήμερα. Αναλύονται τόσο οι γενιές των δικτύων όσο και τα χρησιμοποιούμενα πρότυπα, σε επίπεδο αρχιτεκτονικής όσο και σε επίπεδο πρωτοκόλλων. Στη συνέχεια του κεφαλαίου υπάρχει η τεχνική περιγραφή των επικρατέστερων δικτύων κινητής τηλεφωνίας, σήμερα, δηλαδή των GSM, GPRS και UMTS, ενώ στο τέλος του κεφαλαίου υπάρχει μια σύντομη περιγραφή της διαδικασίας intersystem handover μεταξύ των GSM και UMTS. Στο 3ο Κεφάλαιο, περνάμε πλέον στα Ασύρματα Δίκτυα Δεδομένων. Γίνεται μια εκτενής περιγραφή των προτύπων που έχουν καθοριστεί και συγκεκριμένα στα πρότυπα IEEE 802.15 Wireless Personal Area Networks (WPANs) με κυριότερους εκφραστές τα δίκτυα βασιζόμενα σε Bluetooth και IrDA, το πρότυπο IEEE 802.11 Wireless Local Area Networks (WLANs) με σημαντικότερος εκπροσώπους τα WiFi και HyperLan/2, το πρότυπο IEEE 802.16 Wireless Metropolitan Area Networks (WMANs) ή αλλιώς γνωστότερο ως WiMAX και τέλος το πρότυπο IEEE 802.20 Wireless Wide Area Networks (WWANs) ή διαφορετικά Mobile Broadband Wireless Access (MWBA) το οποίο είναι υπό διερεύνηση ακόμα και φιλοδοξεί να αποτελέσει το ασύρματο ανάλογο της τεχνολογίας xDSL, καθώς θα προσφέρει ασύρματες ευρυζωνικές υπηρεσίες. Στο 4ο Κεφάλαιο παρουσιάζονται μεθοδολογίες υλοποίησης του integration μεταξύ δικτύων των δύο κατηγοριών και συγκεκριμένα παραδείγματα διαλειτουργικότητας, όπως μεταξύ GPRS ή UMTS και WLANs ή μεταξύ UMTS και WiMAX. Γίνεται εκτενής συζήτηση γύρω από τα προβλήματα που θα πρέπει να αντιμετωπιστούν, όπως η εξασφάλιση ανεκτού επιπέδου QoS, οι μηχανισμοί για handover μεταξύ των δικτύων, η διαχείριση της κινητικότητας των χρηστών και των τερματικών και δίνονται παραδείγματα δημιουργίας ενοποιημένων δικτύων, τόσο με τη τεχνική της χαλαρής όσο και με την τεχνική της ισχυρής ζεύξης. Στο τελευταίο τμήμα του Κεφαλαίου, γίνεται μια εκτενής αναφορά στις αρχιτεκτονικές διασύνδεσης ετερογενών δικτύων με IP δίκτυα κορμού, τα γνωστά All – IP networks. Ιδιαίτερη έμφαση δίνεται στους μηχανισμούς πραγματοποίησης των handovers βάσει πολιτικών (policy based) και η χρήση τεχνικών για micromobility και macromobility σε σχέση με την κινητικότητα των τερματικών. Το 5ο Κεφάλαιο αφορά τις εφαρμογές και υλοποιήσεις ασυρμάτων δικτύων δεδομένων στον Ελληνικό χώρο, στα πλαίσια του Επιχειρησιακού Προγράμματος «Κοινωνία της Πληροφορίας» και πιο συγκεκριμένα τα «Εξοπλισμός και δικτύωση σε όλες τις βαθμίδες της εκπαίδευσης», «Ασύρματα Ευρυζωνικά Δίκτυα ΟΤΑ»και «Μητροπολιτικά Ευρυζωνικά Δίκτυα Οπτικών Ινών ΟΤΑ» και ουσιαστικά αποτελούν παραδείγματα και υλοποιήσεις διασύνδεσης WiFi, WiMAX και IP backbone δικτύων όπως το ΣΥΖΕΥΞΙΣ με δυνατότητες για παροχή VoIP. / In this thesis, an effort of presenting the technological landscape of the telecommunication market takes place, with focus on the interoperability between the Mobile Telephony Networks and the Wireless Data Networks and the relative changes that have evolved through this interoperability, both regarding the provided services and the applied business models by the enterprises of the specific market. Within the frames of this effort, a detailed recording of technological developments is realised, in terms of technical specifications and standards, in the two aforementioned categories of networks, so as to conclude to those standards that are utilized by the next generation networks (4G) which will be: • Networks that will be unified so as the different technological platforms will function smoothly. • Networks that will be characterized by low cost of deployment. • The end user will be continuously connected with a wireless access network, enjoying the preferred services anywhere and anytime. The master thesis structure follows the aforementioned methodology. The 1st Chapter includes a short presentation of expected results, both in terms of technologies and services for next generation networks, which we usually refer to as 4G networks (4th Generation) or B3G networks (Beyond 3G) or finally as All - IP wireless networks (AIPN). In the 2nd Chapter, a detailed presentation of Mobile Telephony Networks takes place, from their first versions (1G) until the most modern (3.5G) that have been presented up to today. The analysis includes both the various generations of networks and the used standards, in terms of modulation and multiplexing techniques. The rest of the chapter focuses on the technical description of the prevailing networks, GSM, GPRS and UMTS, while the chapter ends with a short description of intersystem handover processes between GSM and UMTS. Τhe 3rd Chapter, includes an extensive description of the Wireless Data Networks standards such as: IEEE 802.15 Wireless Personal Area Networks (WPANs) with main representatives networks based on Bluetooth and IrDA, standard IEEE 802.11 Wireless Local Area Networks (WLANs) mainly represented by WiFi and HyperLan/2, IEEE 802.16 Wireless Metropolitan Area Networks (WMANs) standard, widely known as WiMax and finally the IEEE 802.20 Wireless Wide Area Networks (WWANs) standard, namely Mobile Broadband Wireless Access (MWBA) that is still under development and aspires to constitutes the wireless version of the xDSL technology, since it aims to provide wireless broadband services. In the 4th Chapter methodologies for integrating the two types of networks, are presented along with examples of interoperability between GPRS / UMTS and WLANs or between UMTS and WiMAX. Extensive discussion around the problems that should be faced, as the guarantee of bearable QoS level, the mechanisms for handover between the networks and the management of mobility of users and terminals, is held. Moreover, examples of integrated networks with both loose and tight coupling methodologies are presented. The last section of the chapter concerns a detailed description of architectures for interconnecting heterogeneous wireless networks over IP – based backhaul networks, namely All – IP networks, with special focus on policy based handover mechanisms and techniques for managing micromobility and macromobility issues. The 5th Chapter concerns the changes taking place in the telecommunications market deriving from the technological progress in the subject of heterogeneous wireless networks interconnection. New service packets are created, as a result of new business plans that are drawn up by the big telecommunications organizations. Finally, we present the developments in the Greek market and subsidised projects from Information Society AE, via which wireless networks have been materialised, with aim to promote Broadband Services.

The most widely used protocol for providing reliable service and congestion control in the Internet is the Transmission Control Protocol (TCP). When the Internet is moving towards more use in mobile applications it is getting more important to know how TCP works for this purpose. One of the technologies used for mobile Internet is the Enhanced General Packet Radio Service (EGPRS) extension to the popular GSM system. This thesis presents a low-level analysis of TCP performance in an EGPRS system and an overview of existing TCP, GSM and EGPRS technologies. The bottleneck in an EGPRS system is the wireless link – the connection between the mobile phone and the GSM base station. The data transfer over the wireless link is mainly managed by the complex RLC/MAC protocol. In this thesis, simulations were made to identify some problems with running TCP and RLC/MAC together. The simulations were made using existing EGPRS testing software together with a new TCP module. The simulation software is also briefly described in the thesis. Additionaly, some suggestions are given in order to enhance performance, both by changing the EGPRS system and by modifying the TCP algorithms and parameters.