Στόχος της διπλωματικής αυτής είναι η παρουσίαση τεχνικών στα πλαίσια της Διαχείρισης Ραδιοπόρων με σκοπό την βελτιστοποίηση της παρεχόμενης υπηρεσίας (QoS), σε δίκτυα κινητής τηλεφωνίας 3ης γενιάς. Στο πρώτο κεφάλαιο γίνεται μια εισαγωγή στα δίκτυα κινητών επικοινωνιών και μια ιστορική αναδρομή. Στη συνέχεια παρουσιάζεται μια επισκόπηση της τεχνολογίας του CDMA και γίνεται καταγραφή και ανάλυση τεχνικών RRM. Στο σύστημα UMTS είναι αφιερωμένο ολόκληρο το δεύτερο κεφάλαιο. Το UMTS εξετάζεται από πλευράς αρχιτεκτονικής και πρωτοκόλλων. Το handover ως βασικό στοιχείο της Διαχείρισης Ραδιοπόρων μελετάται στο τρίτο κεφάλαιο. Ιδιαίτερη αναφορά και μελέτη γίνεται για το Soft Handover, ως το βασικό Handover του συστήματος WCDMA, που χρησιμοποιείται προκειμένου να διασφαλιστεί η απαιτούμενη υπηρεσία. Στο τέταρτο κεφάλαιο περνάμε στην multicast μετάδοση. Σε αυτή την περίπτωση εξετάζουμε την αποδοτική επιλογή καναλιού (Efficient Channel Selection), με στόχο την διασφάλιση του ίδιου QoS για όσο το δυνατόν περισσότερους χρήστες κάνοντας την καλύτερη δυνατή διαχείριση των πόρων του συστήματος. Τέλος το πέμπτο κεφάλαιο αφιερώνεται στην συνολική παρουσίαση των συμπερασμάτων που έχουν εξαχθεί στα προηγούμενα κεφάλαια. / -

Τα ασύρματα δίκτυα έχουν αρχίσει να κατακλύζουν την παγκόσμια αγορά υψηλής τεχνολογίας. Αυτό μπορεί να αποδοθεί στα πολλά πλεονεκτήματα που προσφέρουν καθώς και στο ότι πλέον τα περισσότερα προβλήματα που είχαν στο παρελθόν έχουν αντιμετωπιστεί σε πολύ μεγάλο βαθμό. Ακόμα προσφέρουν ιδιαίτερη ευκολία στην ανάπτυξη λύσεων σε ειδικά προβλήματα. Ωστόσο, όλα τα ασύρματα δίκτυα υιοθετούν κάποια μέθοδο ασφάλειας, η οποία έχει κάποιον αντίκτυπο στις επιδόσεις του δικτύου. Σκοπός της παρούσης εργασίας είναι να μελετηθεί η επιβάρυνση που επέρχεται σε ένα ασύρματο δίκτυο με τη χρήση διαφόρων επιπέδων ασφάλειας. Η μέθοδος και το μέγεθος της ασφάλειας αυτής πρέπει να είναι ισορροπημένη, προκειμένου όπως θα αναλυθεί και στη συνέχεια, και να διασφαλιστεί και η καλή συμπεριφορά του δικτύου αλλά και η ακεραιότητα των προσωπικών δεδομένων. Τα προβλήματα που εμπλέκονται είναι αυτή της δρομολόγησης με χρήση κόμβων περιορισμένης μνήμης και υπολογιστικής ισχύος. Δηλαδή, συσκευές οι οποίες δεν έχουν πλεονασμό υπολογιστικής ισχύος αλλά ούτε και μνήμης, καλούνται να κρυπτογραφήσουν, να αποκρυπτογραφήσουν ή να αναμεταδώσουν πακέτα προς τον προορισμό τους. Η μεθοδολογία αντιμετώπισης του προβλήματος που ακλουθείται είναι αυτή των εξομοιώσεων. Ο λόγος για αυτήν την επιλογή είναι ότι μας προσφέρει τη δυνατότητα να μελετήσουμε πληθώρα περιπτώσεων και στη συνέχεια με χρήση αναλυτικών μεθόδων μας δίνεται η δυνατότητα να αναλύσουμε τα αποτελέσματα που προκύπτουν. / -

WiMax or the IEEE 802.16 standard is one of the most promising broadband wireless technologies nowadays. It is characterized by its high data rates, large coverage area, flexible design and QoS support. The standard defines two modes of operation: Point-to- Multi-Point (PMP) and the Mesh Mode. In the first mode, all nodes are connected directly to the base station and communication is not allowed amongst nodes. In the mesh mode, nodes are placed in an ad hoc manner communicating to neighbors and relaying the traffic of other nodes. The goal of this thesis is to design a partitioning scheme for the frame structure of the Mesh mode. Increasing the frame utilization would result in better support for QoS applications and optimized resource allocation, and thus revenue increase from the service provider’s perspective. The mesh frame is divided into control and data, which are further divided into centralized and distributed portions. We propose a novel and efficient scheme for partitioning the data subframe between the two schedulers. We use a Markovian model that studies the system behavior in the long run, and provides predictions based on analysis of previous window of frames. We further enhance the decision by tuning the partitioning through statistical analysis of smaller windows to accommodate demand changes. Our simulations show that the proposed scheme achieves high utilization under different network and traffic conditions and decreases the packet overflow. / Thesis (Master, Computing) -- Queen's University, 2008-10-02 18:41:36.551

The main goal of today’s wireless Service Providers (SPs) is to provide optimum and ubiquitous service for roaming users while maximizing the SPs own monetary profits. The fundamental objective is to support such requirements by providing solutions that are adaptive to varying conditions in highly mobile and heterogeneous, as well as dynamically changing wireless network infrastructures. This can only be achieved through well-designed management systems. Most techniques fail to utilize the knowledge gained from previously tested reconfiguration strategies on system and network behaviour. This dissertation presents a novel framework that automates the cooperation among a number of wireless SPs facing the challenge of meeting strict service demands for a large number of mobile users. The proposed work employs a novel policy-based system configuration model to automate the process of adapting new network policies. The proposed framework relies on the assistance of a real-time simulator that runs as a constant background process in order to continuously find optimal policy configurations for the SPs’ networks. To minimize the computational time needed to find these configurations, a modified tabu-search scheme is proposed. An objective is to efficiently explore the space of network configurations in order to find optimal network decisions and provide a service performance that adheres to contracted service level agreements. This framework also relies on a distributed Quality of Service (QoS) monitoring scheme. The proposed scheme relies on the efficient identification of candidate QoS monitoring users that can efficiently submit QoS related measurements on behalf of their neighbors. These candidate users are chosen according to their devices’ residual power and transmission capabilities and their estimated remaining service lifetime. Service monitoring users are then selected from these candidates using a novel user-to-user semantic similarity matching algorithm. This step ensures that the monitoring users are reporting on behalf of other users that are highly similar to them in terms of their mobility, used services and device profiles. Experimental results demonstrate the significant gains achieved in terms of the reduced traffic overhead and overall consumed users’ devices power while achieving a high monitoring accuracy, adaptation time speedup, base station load balancing, and individual providers’ payoffs.

Existing methods used for service discovery assume that the world is static, con- sidering a predetermined set of attributes. As a result, current discovery techniques return many results that are irrelevant. Our approach to high quality service dis- covery improves the results’ relevancy by considering dynamic attributes with values changing over time. Using this approach, we reveal structure from the data to satisfy the consumers’ experiences. Web service quality is a set of dynamic attributes used to rank services with similar functionalities. When picking a service to execute financial transactions effi- ciently, we might consider availability, reliability, response time, and transaction cost as quality indicators. Supporting dynamic attributes is a feature critical to providing exceptional quality service discovery. In addition, effective service discovery requires detailed context models that describe both static and dynamic features. The context takes into consideration the situation of the service, the operating environment, the users’ circumstances, and their preferences. For instance, latency is an important issue in stock trading services with direct impact on revenue. One of the main challenges in enabling dynamic service discovery is developing techniques and models to handle the novel aspects of the web service paradigm. This challenge leads to a variety of research questions related to measuring, monitoring, or querying of dynamic attributes, while guaranteeing integrity and validity. We outline an architecture framework called Static Discovery Dynamic Selection (SDDS) to gather and manage dynamic attributes considering both context and do- main information at discovery time—augmenting static mechanisms. The architec- ture of SDDS defines individual components that collectively satisfy flexible and ac- curate service selection with a robust resource management approach capable of con- sidering high-frequency data. Moreover, we devised a multi-criteria decision making algorithm that considers the knowledge domain and the user context, and accordingly, the algorithm returns a small set of accurate and reliable results. As part of the SDDS framework, autonomic computing adds self-adaptability by taking highly dynamic context information into account. The impact of our method is demonstrated in an implementation of the model. We demonstrate that increasing the adaptability of the web service discovery by including context information provides a noticeable reduction in the number of results returned compared to static web service discovery methods. We extend the proposed infrastructure to ascertain whether a particular service satisfies, at execution time, specific security properties. We introduce the notion of certified web service assurance, characterizing how consumers of the service can specify the set of security properties that a service should satisfy. In addition, we illustrate a mechanism to re-check security properties when the execution context changes. To this end, we introduce the concept of a context-aware certificate and describe a dynamic, context-aware service discovery environment. / Graduate

Currently, a viable solution to provide multicast provision over a multiprotocol label switch with traffic engineering (MPLS-TE) domain is unavailable because of the missing link able to couple multicast traffic distribution with an MPLS-TE enabled network. This is due to the limited or less research investigation that was done in this area. Most of the investigation methods tackle the problem individually such as deploying internet protocol (IP) multicast in a plain network or MPLS domain but without considering a combination of both technologies that is aware of differentiated services requirements. This thesis presents an alternative solution for the multicast differentiated services provision problem over a MPLS-TE enabled network. The approach is exposed and analyzed through a practical solution that was developed within a network simulation environment. The research presented in this thesis orchestrates the already available technologies offered by the multicast protocols suite and differentiated services (DiffServ) aware MPLS-TE that allows applying separately the constraint-based routing and admission control to different classes of services. The novelty and solution of this thesis relies on using MPLS constraint-based routing concepts (e.g.traffic trunks) in order to solve TE issues revealed during multicast traffic distribution.

The emerging vehicular ad-hoc networks (VANETs) offer a variety of applications and new potential markets related to safety, convenience and entertainment, however, they suffer from a number of challenges not shared so deeply by other types of existing networks, particularly, in terms of mobility of nodes, and end-to-end quality of service (QoS) provision. Although several existing works in the literature have attempted to provide efficient protocols at different layers targeted mostly for safety applications, there remain many barriers to be overcome in order to constrain the widespread use of such networks for non-safety applications, specifically, for video streaming: 1) impact of high speed mobility of nodes on end-to-end QoS provision; 2) cross-layer protocol design while keeping low computational complexity; 3) considering customer-oriented QoS metrics in the design of protocols; and 4) maintaining seamless single-hop and multi-hop connection between the destination vehicle and the road side unit (RSU) while network is moving. This thesis addresses each of the above limitations in design of cross-layer protocols for video streaming application. 1) An adaptive MAC retransmission limit selection scheme is proposed to improve the performance of IEEE 802.11p standard MAC protocol for video streaming applications over VANETs. A multi-objective optimization framework, which jointly minimizes the probability of playback freezes and start-up delay of the streamed video at the destination vehicle by tuning the MAC retransmission limit with respect to channel statistics as well as packet transmission rate, is applied at road side unit (RSU). Two-hop transmission is applied in zones in which the destination vehicle is not within the transmission range of any RSU. In the multi-hop scenario, we discuss the computation of access probability used in the MAC adaptation scheme and propose a cross-layer path selection scheme; 2) We take advantage of similarity between multi-hop urban VANETs in dense traffic conditions and mesh connected networks. First, we investigate an application-centric routing scheme for video streaming over mesh connected overlays. Next, we introduce the challenges of urban VANETs compared to mesh networks and extend the proposed scheme in mesh network into a protocol for urban VANETs. A classification-based method is proposed to select an optimal path for video streaming over multi-hop mesh networks. The novelty is to translate the path selection over multi-hop networks to a standard classification problem. The classification is based on minimizing average video packet distortion at the receiving nodes. The classifiers are trained offline using a vast collection of video sequences and wireless channel conditions in order to yield optimal performance during real time path selection. Our method substantially reduces the complexity of conventional exhaustive optimization methods and results in high quality (low distortion). Next, we propose an application-centric routing scheme for real-time video transmission over urban multi-hop vehicular ad-hoc network (VANET) scenarios. Queuing based mobility model, spatial traffic distribution and prob- ability of connectivity for sparse and dense VANET scenarios are taken into consideration in designing the routing protocol. Numerical results demonstrate the gain achieved by the proposed routing scheme versus geographic greedy forwarding in terms of video frame distortion and streaming start-up delay in several urban communication scenarios for various vehicle entrance rate and traffic densities; and 3) finally, the proposed quality-driven routing scheme for delivering video streams is combined with a novel IP management scheme. The routing scheme aims to optimize the visual quality of the transmitted video frames by minimizing the distortion, the start-up delay, and the frequency of the streaming freezes. As the destination vehicle is in motion, it is unrealistic to assume that the vehicle will remain connected to the same access router (AR) for the whole trip. Mobile IP management schemes can benefit from the proposed multi-hop routing protocol in order to adapt proxy mobile IPv6 (PMIPv6) for multi-hop VANET for video streaming applications. The proposed cross-layer protocols can significantly improve the video streaming quality in terms of the number of streaming freezes and start-up delay over VANETs while achieving low computational complexity by using pattern classification methods for optimization.

IEEE 802.16標準是針對無線城域網路(Wireless Metropolitan Area Network)而設計的，它支援服務品質(QoS)，而且具有相當高的傳輸速率。每一種應用服務都有不同的型態，根據這些不同的型態，802.16 定義了四個不同的服務品質類別。然而，最關鍵的部份－封包排程卻沒有被定義在802.16標準裡面。在這篇論文中，我們提出了一套完整的允入控管(call admission control)和上行封包排程的架構。首先，我們先以令牌桶(token bucket)機制為基礎，設計了一套802.16專用的允入控管和上行封包排程的模組。接著我們介紹如何將令牌桶機制套用至一般的連線。我們找出了一個預測連線的延遲(delay)和漏失率(loss rate)的模型，接著可以利用這個模型，並透過簡單的搜尋演算法來找出適合的令牌速率和令牌桶的大小。模擬的結果表示，我們的允入控管和上行封包排程能夠確實對具有即時性質的連線的提供保證，且我們將令牌桶機制套用到一般連線的模組也能準確的運作。最後，我們也提出了一個簡單的整合實例並評估其效能。 / The IEEE 802.16 standard was designed for Wireless Metropolitan Area Network (WMAN). It supports QoS and has very high transmission rate. According to different application types, there are four QoS classes defined in the IEEE 802.16 standard. The key part of 802.16 for QoS– packet scheduling, was undefined. In this thesis, a complete call admission control (CAC) and uplink packet scheduling is presented. We first proposed a token-bucket based uplink packet scheduling combined with CAC. Then a model of characterizing traffic flows by token bucket parameters, namely token rate and bucket size, is presented. We proposed a queuing model to predict the delay and loss rate for a token bucket controlled traffic flow. In order to fulfill token bucket based CAC, we need to find appropriate token rate and bucket size for any flows. A simple search algorithm coupled with our queuing model can be used to achieve this. Multiplexing of two traffic flows is also introduced. The simulation results show that our CAC and uplink packet scheduling can promise the delay requirement of real-time flows and prevent each class from starvation. The precision of our token rate estimation model is also validated. Finally, a simple integration of our CAC, uplink scheduling, and multiplexing is evaluated.

Les xarxes WLANs possibiliten un accés de banda ampla a Internet des d'un terminal mòbil, essent una possible solució alternativa a les xarxes cel·lulars. Tanmateix, aquest tipus de tecnologia presenta certes limitacions, com és la difícil coexistència entre fluxos de tràfic rígids (VoIP) i fluxos de tràfic elàstic (TCP), degut al propi protocol d'accés al medi. En aquesta tesi es proposa la utilització d'un nou mecanisme de control d'admissió que utilitzant el nou estàndard de qualitat de servei en xarxes WLAN (EDCA). La utilització del mecanisme de control d'admissió millora notablement les prestacions que es poden obtenir de la xarxa, solucionant les diferents limitacions de la tecnologia. Per a l'avaluació i optimització del mecanisme de control d'admissió s'ha desenvolupat un conjunt d'eines matemàtiques que permeten capturar tant la dinàmica del protocol d'accés com el comportament dels diferents fluxos de tràfic multimèdia que s'han consideren (VoIP i tràfic elàstic, TCP). / WLANs provide a broadband access to Internet from a mobile terminal, which can be a possible alternative solution to cellular networks. However, this technology presents several limitations, as it is the difficult coexistence between rigid traffic flows (VoIP) and elastic traffic flows (TCP), due to the medium access protocol itself. In this thesis a new admission control mechanism is proposed. It uses the set of QoS mechanisms provided by the new EDCA standard. The use of the proposed admission control mechanism improves the overall WLAN performance, solving the different technology limitations. In order to be able to evaluate and optimize the admission control mechanism, several mathematical tools have been developed in order to capture the dynamics of both, the access protocol and of the different multimedia traffic flows that have been considered.

Applications with timing requirements, such as multimedia and live multi-user interaction, are becoming more prevalent in wide area networks. The desire to provide more predictable performance for such applications in packet switched wide area networks is evident in the channel management provided by Asynchronous Transfer Mode (ATM) networks and in the extensions to the Internet protocols proposed by the Internet Engineering Task Force (IETF) working groups on integrated and differentiated service. The ability to provide guarantees on the performance of traffic flows, such as packet delay and loss characteristics, relies on an accurate model of the traffic arrival and service at each node in the network. This thesis surveys the work in bounding packet delay based on various proposed queuing disciplines and proposes a method for more accurately defining the traffic arrival and worst case backlog experienced by packets. The methods are applied to the first in first out (FIFO) queuing discipline to define equations for determining the worst case backlog and queuing delay in multihop networks. Simulation results show a significant improvement in the accuracy of the delay bounds over existing bounds published in the literature. An improvement of two orders of magnitude can be realised for a ten hop path and the improvement increases exponentially with the length of the path for variable rate network traffic. The equations derived in the thesis also take into consideration the effect of jitter on delay, thereby removing the requirement for rate controllers or traffic shaping within the network. In addition to providing more accurate delay bounds, the problem of providing fault tolerance to channels with guaranteed quality of service (QoS) is also explored. This thesis introduces a method for interleaving resource requirements of backup channels to reduce the overall resource reservations that are required to provide guaranteed fault recovery with the same QoS as the original failed channel. An algorithm for selecting recovery paths that can meet a channel's QoS requirements during recovery is also introduced. / Thesis (Ph.D.)--Computer Science, 2003.