No description available.

The heterogeneous deployment of small cells (e.g., femtocells) in the coverage area of the traditional macrocells is a cost-efficient solution to provide network capacity, indoor coverage and green communications towards sustainable environments in the future fifth generation (5G) wireless networks. However, the unplanned and ultra-dense deployment of femtocells with their uncoordinated operations will result in technical challenges such as severe interference, a significant increase in total energy consumption, unfairness in radio resource sharing and inadequate quality of service provisioning. Therefore, there is a need to develop efficient radio resource management algorithms that will address the above-mentioned technical challenges. The aim of this thesis is to develop and evaluate new efficient radio resource management algorithms that will be implemented in cognitive radio enabled femtocells to guarantee the economical sustainability of broadband wireless communications and users' quality of service in terms of throughput and fairness. Cognitive Radio (CR) technology with the Dynamic Spectrum Access (DSA) and stochastic process are the key technologies utilized in this research to increase the spectrum efficiency and energy efficiency at limited interference. This thesis essentially investigates three research issues relating to the efficient radio resource management: Firstly, a self-organizing radio resource management algorithm for radio resource allocation and interference management is proposed. The algorithm considers the effect of imperfect spectrum sensing in detecting the available transmission opportunities to maximize the throughput of femtocell users while keeping interference below pre-determined thresholds and ensuring fairness in radio resource sharing among users. Secondly, the effect of maximizing the energy efficiency and the spectrum efficiency individually on radio resource management is investigated. Then, an energy-efficient radio resource management algorithm and a spectrum-efficient radio resource management algorithm are proposed for green communication, to improve the probabilities of spectrum access and further increase the network capacity for sustainable environments. Also, a joint maximization of the energy efficiency and spectrum efficiency of the overall networks is considered since joint optimization of energy efficiency and spectrum efficiency is one of the goals of 5G wireless networks. Unfortunately, maximizing the energy efficiency results in low performance of the spectrum efficiency and vice versa. Therefore, there is an investigation on how to balance the trade-off that arises when maximizing both the energy efficiency and the spectrum efficiency simultaneously. Hence, a joint energy efficiency and spectrum efficiency trade-off algorithm is proposed for radio resource allocation in ultra-dense heterogeneous networks based on orthogonal frequency division multiple access. Lastly, a joint radio resource allocation with adaptive modulation and coding scheme is proposed to minimize the total transmit power across femtocells by considering the location and the service requirements of each user in the network. The performance of the proposed algorithms is evaluated by simulation and numerical analysis to demonstrate the impact of ultra-dense deployment of femtocells on the macrocell networks. The results show that the proposed algorithms offer improved performance in terms of throughput, fairness, power control, spectrum efficiency and energy efficiency. Also, the proposed algorithms display excellent performance in dynamic wireless environments.

No description available.

Unlike traditional cellular networks, where voice calls dominate the network traffic, modern mobile traffic is created by of a mixture of both voice and broadband data services. The heterogeneous mixture of voice and data services in mobile broadband networks includes voice calls, web browsing, file transfers, video streaming, and social media applications. Consequently, network planning and radio resource management strategies must be aware of the quality of experience perceived by the users using various types of applications. In this report, we explore the traffic characteristics, scheduling and resource allocation strategies, and user experience models in mobile broadband networks. / text

No description available.

Spectrum management in wireless broadband networks as regards its cost and its efficient usage has posed a huge challenge for mobile network operators. Traditionally, network operators had exclusive rights to access the band of spectrum allocated to them, but with the high price of spectrum license, it is becoming necessary to find alternative ways to use and access spectrum more efficiently. Resource virtualization is a method which has been extensively adopted in hardware computing for creating abstract versions of physical hardware resources and it has proven to be a powerful technique for customized resource provision and sharing. This idea of resource virtualization is gradually being transferred into the domain of wireless mobile network resource management but the ideas around it are still evolving. Since spectrum is an important wireless network resource, it is imperative to provide an efficient and cost effective means for the resource to be accessed and utilized. Therefore the idea of spectrum virtualization is investigated in this research as a possible solution to this problem. To expand on the notion of spectrum virtualization, this research further explores the idea of network federation. Network Federation involves the interconnection of diverse network components to be operated as a single seamless network. This will enable them share their network resources while the networks are geographically dispersed and managed by different network operators. To fully implement these concepts there is a need for a well-developed network framework. This research proposes two novel architectures for spectrum virtualization and network federation using the WiMAX (Worldwide Interoperability for Microwave Exchange) wireless broadband technology. The proposed WiMAX spectrum virtualization architecture introduces a novel entity known as the Virtual Spectrum Hypervisor (VS-Hypervisor). This VS-Hypervisor bears the responsibility of spectrum management and virtualization within the WiMAX framework. In the implementation of WiMAX network federation, the novel architecture enables the cooperative existence of multiple WiMAX base-stations having virtualization capabilities with overlapping cellular coverage areas for the purpose of sharing their spectrum resources. In this architecture, a novel federation control plane known as the Virtual Spectrum Exchange Locale (VSEL) is proposed. The VSEL facilitates the VS-Hypervisors in the federated physical base-stations to be able to negotiate and exchange spectrum between themselves to match their spectrum needs. The architectures for WiMAX spectrum virtualization and network federation was modelled and implemented using the OPNET Modeler. Results obtained validated their efficacy with respect to the effective management of the wireless network spectrum. Therefore this proposed network architectures would help network operators optimize their radio networks.

When looking towards the deployment of 5G network architectures, mobile network operators will continue to face many challenges. The number of customers is approaching maximum market penetration, the number of devices per customer is increasing, and the number of non-human operated devices estimated to approach towards the tens of billions, network operators have a formidable task ahead of them. The proliferation of cloud computing techniques has created a multitude of applications for network services deployments, and at the forefront is the adoption of Software-Defined Networking (SDN) and Network Functions Virtualisation (NFV). Mobile network operators (MNO) have the opportunity to leverage these technologies so that they can enable the delivery of traditional networking functionality in cloud environments. The benefit of this is reductions seen in the capital and operational expenditures of network infrastructure. When going for NFV, how a Virtualised Network Function (VNF) is designed, implemented, and placed over physical infrastructure can play a vital role on the performance metrics achieved by the network function. Not paying careful attention to this aspect could lead to the drastically reduced performance of network functions thus defeating the purpose of going for virtualisation solutions. The success of mobile network operators in the 5G arena will depend heavily on their ability to shift from their old operational models and embrace new technologies, design principles and innovation in both the business and technical aspects of the environment. The primary goal of this thesis is to design, implement and evaluate the viability of data centre and cloud network infrastructure sharing use case. More specifically, the core question addressed by this thesis is how virtualisation of network functions in a shared infrastructure environment can be achieved without adverse performance degradation. 5G should be operational with high penetration beyond the year 2020 with data traffic rates increasing exponentially and the number of connected devices expected to surpass tens of billions. Requirements for 5G mobile networks include higher flexibility, scalability, cost effectiveness and energy efficiency. Towards these goals, Software Defined Networking (SDN) and Network Functions Virtualisation have been adopted in recent proposals for future mobile networks architectures because they are considered critical technologies for 5G. A Shared Infrastructure Management Framework was designed and implemented for this purpose. This framework was further enhanced for performance optimisation of network functions and underlying physical infrastructure. The objective achieved was the identification of requirements for the design and development of an experimental testbed for future 5G mobile networks. This testbed deploys high performance virtualised network functions (VNFs) while catering for the infrastructure sharing use case of multiple network operators. The management and orchestration of the VNFs allow for automation, scalability, fault recovery, and security to be evaluated. The testbed developed is readily re-creatable and based on open-source software.

Αντικείμενο της παρούσας διπλωματικής εργασίας είναι η ολοκληρωμένη παρουσίαση του προτύπου IEEE 802.16, που χρησιμοποιείται από το σύγχρονο ασύρματο ευρυζωνικό δίκτυο με την εμπορική ονομασία WiMAX και η εκπόνηση μίας μελέτης ράδιο-κάλυψης για τον προσδιορισμό των τεχνικών παραμέτρων, ώστε η εφαρμογή ενός τέτοιου δικτύου να προσφέρει τη βέλτιστη ράδιο-κάλυψη. Αρχικά γίνεται μια εισαγωγική παρουσίαση των ασύρματων τεχνολογιών, που χρησιμοποιούνται στην Ελλάδα για την πρόσβαση στις ευρυζωνικές υπηρεσίες και παρατίθενται στατιστικά στοιχεία, που απεικονίζουν την κατάσταση που επικρατή στον ελλαδικό χώρο. Στη συνέχεια καταγράφεται η ανάπτυξη και η εξέλιξη του προτύπου IEEE 802.16 και γίνεται αναφορά στο ρόλο που διαδραματίζουν το WiMAX Forum και οι επίσημοι κατασκευαστές. Προχωρώντας, εμβαθύνουμε περισσότερο με την παρουσίαση της αρχιτεκτονικής των δικτύων WiMAX, αλλά και των τεχνικών χαρακτηριστικών και των προδιαγραφών, που αυτά προσφέρουν και τα έχουν καταστήσει πρωτοπόρα στην εμπορική αγορά των ασύρματων επικοινωνιών. Τέλος, εκπονούμε μία λεπτομερή μελέτη για τη βέλτιστη ράδιο-κάλυψη σε μία συγκεκριμένη γεωγραφική περιοχή, σύμφωνα με τις προδιαγραφές της τεχνολογίας WiMAX και προσδιορίζουμε την ποιότητα των υπηρεσιών που θα μπορεί να προσφέρει το δικτύου WiMAX, στηριζόμενοι στα αποτελέσματα της μελέτης. / The subject of this thesis is the complete presentation of the standard IEEE 802.16, which is used by the modern wireless broadband network under the trade name WiMAX and the conduction of a radio coverage study to determine the technical parameters, so that the implementation of such a network can offer the optimal radio coverage. First, we make an introduction of wireless technologies used for access to broadband services and we present statistics that reflect the real market condition in Greece. Then we record the development and the progress of the IEEE 802.16 standard and we also make a small reference to the role of the WiMAX Forum and the official manufacturers. In depth, we analyze the architecture of WiMAX networks and all the technical features and specifications, which make the WiMAX technology a pioneer and have consolidate it in the market of wireless communications. Finally, we work out a detailed study on the optimal radio coverage in a specific geographic area, in accordance with the requirements of WiMAX technology and furthermore we estimate the quality of services that can be provided by the WiMAX network, relying on the results of the simulation.

Το αντικείμενο της παρούσας διπλωματικής εργασίας είναι η περιγραφή και ανάλυση συστημάτων IP TV. Στο 1ο κεφάλαιο παρατίθεται ο ορισμός του IP TV και γίνεται αναφορά στην διαφορά του από το internet TV. Στη συνέχεια παρουσιάζεται η υποδομής ενός IP TV δικτύου, οι εφαρμογές του και οι υπηρεσίες που αυτό μπορεί να παρέχει στους χρήστες. Κατόπιν περιγράφονται τα πλεονεκτήματα της ψηφιακής μετάδοσης σήματος και αναλύονται τα μοντέλα συνεργασίας και διαχείρισης περιεχομένου. Στο 2ο κεφάλαιο εμβαθύνουμε στα ευρυζωνικά δίκτυα και στη διανομή του IP TV και πως αυτή επιτυγχάνεται μέσω διαφόρων τεχνολογιών που εφαρμόζονται σήμερα (πιο συγκεκριμένα το ADSL). Ταυτόχρονα επεξηγούνται οι τεχνολογίες του δικτύου πυρήνα που ακολουθούνται από τους παρόχους και αφορούν - κατά το μεγαλύτερο μέρος τους - στα ενσύρματα δίκτυα καθώς και ποιοί παράγοντες αυτών επηρεάζουν το IP TV. Στο 3ο κεφάλαιο ακολουθεί λεπτομερής τεχνική περιγραφή και ανάλυση των συστημάτων IP TV, των υπηρεσιών τύπου Broadcast και των διαδραστικών υπηρεσιών video κατ’ απαίτηση του συνδρομητή. Εξειδικεύονται τα επιμέρους τμήματα ενός ολοκληρωμένου IP TV συστήματος, παρουσιάζεται το πώς αυτά αλληλεπιδρούν μεταξύ τους αλλά και με το σύνολο του δικτύου. Αναλύεται το δίκτυο ασφαλείας που απαραιτήτως δημιουργείται για να είναι δυνατή η λειτουργία αυτών των συστημάτων και οι τρόποι μετάδοσης του περιεχομένου. Επιπρόσθετα περιγράφεται η τεχνολογία multicasting σε IP TV δίκτυο και η αρχιτεκτονική που απαιτείται για να επιτευχθεί. Στο 4ο κεφάλαιο δίνεται ιδιαίτερη έμφαση στις τεχνικές ασφαλείας που εφαρμόζονται και ειδικότερα στα IP TV Conditional Access και στα συστήματα DRM. Αναλύεται το πώς αυτά υλοποιούνται σε επίπεδο hardware και σε επίπεδο software (λογισμικού) και παρουσιάζονται οι τεχνικές κρυπτογράφησης που ακολουθούνται. Γίνεται αναφορά υβριδικών τέτοιων συστημάτων που περικλείουν μέρος και των 2 προαναφερθέντων τεχνικών και μελετώνται τα συστήματα DRM και πως αυτά υλοποιούνται. Η σημαντική εφαρμογή των IP TV συστημάτων, video on demand (χρήση βίντεο υπηρεσίας κατ’ απαίτηση του χρήστη) αναλύεται στο 5ο κεφάλαιο. Αυτό το κεφάλαιο έχει αφιερωθεί στην συγκεκριμένη υπηρεσία, στο πώς αυτή είναι διαθέσιμη σήμερα εμπορικά, πως κατέστη δυνατή η υλοποίηση της τεχνικά, τα πρωτόκολλα που χρησιμοποιούνται στα εν λόγω δίκτυα. Τέλος (6ο και 7ο κεφάλαιο) παρουσιάζονται λύσεις από παρόχους που δραστηριοποιούνται στον Ελλαδικό χώρο (για τους οποίους υπήρχε διαθέσιμη πληροφορία) και στο 8ο κεφάλαιο παρουσιάζονται οι τεχνικές απαιτήσεις για την υπηρεσία IP TV. / --

Στόχος της εργασίας είναι η μελέτη και η παρουσίαση των μοντέλων διάχυσης καθώς και η εφαρμογή τους στα ευρυζωνικά δίκτυα, με απώτερο σκοπό τη μελέτη της αξιοπιστίας τους ως προς τις εκτιμήσεις τους αλλά και την πρόβλεψη του ποσοστού διείσδυσης της ευρυζωνικότητας στην Ελλάδα για τα επόμενα χρόνια. / -