Wireless On-board diagnostics functionality, which is a future outlook to vehicle system parameter analysis, enables measurements and controlling without the limitation of a physical connector. Today every vehicle must by law provide the possibility to analyze engine and emission related parameters (OBD II). The wireless connection requires a high security level to prevent unauthorized communication establishment with the truck’s bus system. The aim of the project is to make a survey of the available security mechanisms and to find the most promising solutions. Furthermore, several usage scenarios and access right levels are specified and a risk analysis of the whole system is made. The greatest challenge is the specification and implementation of a proper key-exchange mechanism between the analyzing device and the truck’s bus system, which is therefore carried out with the highest possible level of awareness. Consequently several different concepts have been formulated based on the different usage scenarios.

This thesis proposes a variety of antenna designs suitable for modern of mobile products, such as mobile phones, PDAs and so forth, on both the 2G and 3G communication systems according to the mobile communication development. Based on the integration of monopole or planar inverted-F antenna with the system ground planes, multi-frequency, broadband, and high radiation efficiency can be achieved, which is very promising to be adapted into communication products. Furthermore, an antenna capable of WLAN and UWB is proposed for future wireless communication applications.

It is more and more popular to transmit and receive information with Wireless LAN(WLAN) as the time of science and technology has been approaching. Every type of business gradually has priority on WLAN for marketing. Especially business of agents of real estate, they use WLAN as tool for marketing to improve the service with information and human nature and to break through the shape of traditional human operation. They record characters and functions of surrounding environment of the houses which are entrusted by clients in their system to provide immediate and local information with house-buyer. This becomes personalizing and valuable selling information. It takes both quantitative and qualitative methods as research methods in the study, and agents of real estate using and not using WLAN in Kaohsiung City are picked as research objects. The study takes depth interviews to realize conditions for wireless network marketing using, motivation for wireless network marketing, and using mode for wireless network marketing, and it also analyzes the differences among wireless network marketing, traditional marketing, and internet marketing. Meanwhile the study use questionnaires survey to figure out the reason why some agents of real estate do not use WLAN for marketing. There are four findings in the study as follows: (1) Agents of real estate using WLAN for marketing are mainly direct branches and over 15 years old. (2) The traditional way for marketing used by agents of real estate using or not using WLAN for marketing is newspaper. (3) Agents of real estate using WLAN for marketing know the requirements of clients and can improve the quality of service better then agents of real estate not using WLAN for marketing. (4) The rate of agents of real estate not using WLAN for marketing at present would like to use WLAN for marketing in the future become more. The conclusion of the study indicates the marketing mode of using new science technology can inquire new information anytime and anywhere. The mode of marketing with WLAN provides business of agents of real estate with the immediate and local information, and this is the point that mass media can not achieve. There are difficulties for business of agents of real estate in Kaohsiung City to use high science technology as a kind of marketing mode. Kaohsiung City should try to upgrade M capacity step by step and take both traditional marketing and WLAN marketing to enhance the function of WLAN for marketing in business of agents of real estate.

In this dissertation, we propose using and analytically evaluate the predictive multicast polling scheme and the tree splitting algorithm for medium access control in interference dominating wireless access networks with random traffic and finite nodes. In an interference dominating wireless network, a receiver could simultaneously receive multiple packets from a variety of transmitters, as long as the signal-to-interference-plus-noise ratio exceeds a predetermined threshold. We concentrate on the case of in which the maximum queue size in a node is finite. We use discrete-time Markov chains, reward processes and regenerative processes to derive the throughput, the packet blocking probability, the average packet delay, and the average system size. We show that the system performance of the predictive multicast polling scheme can be significantly improved with a few additional buffers in the queues. Our study also shows that exact performance of the splitting algorithm depends on the total number of nodes in the networks. We verify our numerical results by rigorous mathematical proof and computer simulations.

This paper describes a solution which enables mobile devices to transparently access the campus network and the Internet. Different user classes are provided, and security issues are taken into account. The requirements for user machines are low, and the software is nearly maintenance-free for the network administrator after installation and configuration. / Diese Arbeit realisiert einen transparenten Zugang zum Campusnetz der TU Chemnitz und zum Internet für mobile Geräte. Dabei werden mehrere Nutzerklassen unterschieden und Sicherheitsaspekte berücksichtigt. Die Anforderungen an die Nutzerrechner sind gering, und der Aufwand für den Administrator beschränkt sich im wesentlichen auf die Installation und Konfiguration der Software.

Traditionally radio spectrum was considered a commodity to be allocated in a fixed and centralized manner, but now the technical community and the regulators approach it as a shared resource that can be flexibly and intelligently shared between competing entities. In this thesis we focus on novel strategies to sense and access the radio spectrum within the framework of Opportunistic Spectrum Access via Cognitive Radio Networks (CRNs). In the first part we develop novel transmit opportunity detection methods that effectively exploit the gray space present in packet based networks. Our methods proactively detect the maximum safe transmit power that does not significantly affect the primary network nodes via an implicit feedback mechanism from the Primary network to the Secondary network. A novel use of packet interarrival duration is developed to robustly perform change detection in the primary network's Quality of Service. The methods are validated on real world IEEE 802.11 WLANs. In the second part we study the inferential use of Goodness-of-Fit tests for spectrum sensing applications. We provide the first comprehensive framework for decision fusion of an ensemble of goodness-of-fit tests through use of p-values. Also, we introduce a generalized Phi-divergence statistic to formulate goodness-of-fit tests that are tunable via a single parameter. We show that under uncertainty in the noise statistics or non-Gaussianity in the noise, the performance of such non-parametric tests is significantly superior to that of conventional spectrum sensing methods. Additionally, we describe a collaborative spatially separated version of the test for robust combining of tests in a distributed spectrum sensing setting. In the third part we develop the sequential energy detection problem for spectrum sensing and formulate a novel Sequential Energy Detector. Through extensive simulations we demonstrate that our doubly hierarchical sequential testing architecture delivers a significant throughput improvement of 2 to 6 times over the fixed sample size test while maintaining equivalent operating characteristics as measured by the Probabilities of Detection and False Alarm. We also demonstrate the throughput gains for a case study of sensing ATSC television signals in IEEE 802.22 systems. / text

No description available.

Σε έναν κόσμο που αλλάζει με ταχύτατους ρυθμούς, που η γνώση σχεδόν διπλασιάζεται κάθε 10 χρόνια, η χρήση των κινητών δικτύων τρίτης γενιάς έχει αρχίσει να επεκτείνεται. Ειδικά σε μια χώρα όπως η Ελλάδα που η μορφολογία του εδάφους δεν επιτρέπει την χρησιμοποιήση των οπτικών ινών, η ασύρματη επικοινωνία αποκτά πολύ σημαντικό ρόλο. Το τελευταίο καιρό έχει επεκταθεί η χρήση των κινητών δικτύων 3ης γενιάς, που αντικαθιστούν τα προηγούμενα της 2ης γενιάς προσφέροντας στους χρήστες παραπάνω υπηρεσίες. Οι προηγμένες υπηρεσίες που παρέχονται σε ομάδες κινητών χρηστών είναι εφάμιλες με αυτές των συμβατικών ενσύρματων δικτύων όπως mobile internet, mobile streaming, mobile TV κ.α. Στην περίπτωση του ενσύρματου δικτύου είναι εύκολο να κατανοήσουμε ότι ο multicast αυτός μηχανισμός αποστέλνει τα δεδομένα μόνο μία φορα πάνω απο κάθε σύνδεσμο,που είναι τμήμα των μονοπατιών των προορισμών. Στα κινητά δίκτυα που έχουμε την MBMS υπηρεσία (Multimedia Broadcast / Multicast Service) που υποστηρίζει IP εφαρμογές πανεκπομπής (broadcact) και πολυεκπομπής (multicast) επιτρέποντας με αυτό τον τρόπο την παροχή υπηρεσιών υψηλού ρυθμού μετάδοσης σε πολλαπλούς χρήστες με οικονομικό τρόπο. Η multicast μετάδοση δεδομένων σε κινητά δίκτυα επικοινωνιών βρίσκεται ακόμη στο στάδιο των δοκιμών και της προτυποποίησης της. Ένας multicast μηχανισμός μεταδίδει τα δεδομένα μόνο μία φορά πάνω από κάθε ασύρματο σύνδεσμο που αποτελεί τμήμα των μονοπατιών προς τους προορισμούς-κινητούς χρήστες. Αντικείμενο στην προκείμενη διπλωματική εργασία είναι η μελέτη της τεχνολογιας hsdpa για την μετάδοση multicast δεδομένων σε δίκτυα κινητών επικοινωνών Τρίτης γενιάς .Οπου η σημαντικότερη πρόκληση που αντιμετωπίζει σήμερα η παγκόσμια αγορά κινητών τηλεπικοινωνιών είναι η παροχή νέων, ελκυστικών και διαδραστικών υπηρεσιών προς τους τελικούς χρήστες. Η τεχνολογία High Speed Packet Access (HSPA) αποτελεί τη φυσιολογική εξέλιξη του WCDMA προς αυτή την κατεύθυνση, η οποία πολλές φορές συναντάται και ως 3.5G ή 3G+, προκειμένου να δηλώσει την αναβάθμιση του 3G (UMTS) και ήδη έχει υιοθετηθεί από πολλά δίκτυα κινητής τηλεφωνίας ανά τον κόσμο. Η εισαγωγή του HSPA κρίθηκε απαραίτητη καθώς, στην πράξη, οι μέγιστοι ρυθμοί μετάδοσης για τα UMTS δίκτυα αποδείχθηκαν χαμηλοί για εφαρμογές πολυμέσων. Ουσιαστικά, το HSPA αποτελεί μία σημαντική αναβάθμιση των UMTS δικτύων προσφέροντας υψηλότερο εύρος ζώνης στους κινητούς χρήστες και αυξημένη χωρητικότητα για τους τηλεπικοινωνιακούς παρόχους με αποτέλεσμα την παροχή υπηρεσιών και εφαρμογών αυξημένης διαδραστικότητας. Η ορολογία HSPA αναφέρεται σε μία γενικότερη έννοια που υιοθετήθηκε από το UMTS Forum προκειμένου να τονίσει τις αναβαθμίσεις του UMTS Radio Interface στις εκδόσεις 5 και 6 του 3GPP στάνταρ. Η συμβολή της HSPA τεχνολογίας, προσεγγίζει μόνο το δίκτυο πρόσβασης, δηλαδή το UTRAN, χωρίς να επεμβαίνει καθόλου στη δομή και τη λειτουργικότητα του Core Network του UMTS. Πιο συγκεκριμένα, το HSPA αναφέρεται σε βελτιώσεις που πραγματοποιήθηκαν τόσο στον κατερχόμενο ασύρματο σύνδεσμο, μέσω του High Speed Downlink Packet Access (HSDPA) όσο και στον ανερχόμενο, μέσω του High Speed Uplink Packet Access (HSUPA). Αξίζει να αναφερθεί ότι τόσο το HSDPA όσο και το HSUPA μπορούν να υλοποιηθούν στο ίδιο εύρος ζώνης με το UMTS (των 5 MHz), γεγονός που επιτρέπει την παράλληλη λειτουργία τόσο του HSPA όσο και του κλασσικού UMTS. / Due to rapid growth of mobile communications technology, the demand for wireless multimedia communications thrives in today’s consumer and corporate market. The need to evolve multimedia applications and services is at a critical point given the proliferation and integration of wireless systems. Consequently, there is a great interest in using the IP-based networks to provide multimedia services. One of the most important areas in which the issues are being debated, is the development of standards for the Universal Mobile Telecommunications System (UMTS). UMTS constitutes the third generation (3G) of cellular wireless networks which aims to provide high-speed data access along with real time voice calls. Wireless data is one of the major boosters of wireless communications and one of the main motivations of the next generation standards. Through the 3G mobile networks, the mobile users have the opportunity to run applications and realize services that offered until today only by wired networks. Such broadband services are mobile Internet, mobile TV, mobile gaming, mobile streaming, video calls etc. High Speed Packet Access (HSPA) constitutes a significant step towards the so-called Mobile Broadband. HSPA supports both downlink and uplink communication through the HSDPA and HSUPA channels, respectively. HSPA promises the provision of enhanced end-users’ experience with a wide range of novel, interactive applications, faster performance and reduced delays. Furthermore, from the operators’ prism, HSPA ensures improved network performance, increased capacity and higher coverage. Multimedia Broadcast Multicast Service (MBMS) is a novel framework, extending the existing UMTS infrastructure that constitutes a significant step towards the so-called Mobile Broadband. MBMS is intended to efficiently use network and radio resources, both in the core network and, most importantly, in the air interface of UMTS Terrestrial Radio Access Network (UTRAN), where the bottleneck is placed to a large group of users. Actually, MBMS is a point-to-multipoint service in which data is transmitted from a single source entity to multiple destinations, allowing the networks resources to be shared. MBMS is an efficient way to support the plethora of the emerging wireless multimedia and application services such as IP Video Conferencing, Streaming Video by supporting both broadcast and multicast transmission modes. Long Term Evolution (LTE) will stretch the performance of 3G systems with improved coverage and system capacity, as well as increased data rates and reduced latency. LTE also provides a tight integration between unicast and multicast/broadcast MBMS transport bearers. Moreover, it also takes 3G-MBMS one step further to provide highly efficient multi-cell broadcast. By transmitting not only identical signals from multiple cell sites (with identical coding and modulation), but also synchronize the transmission timing between cells, the signal at the mobile terminal will appear exactly as a signal transmitted from a single cell site and subject to multi-path propagation. There is a growing demand for wireless data applications, which although face low penetration today, are expected to gain high interest in future mobile networks. These applications actually reflect a modern, future way of communication among mobile users. For instance, mobile TV is expected to be a ‘killer’ application for 3G’s. Such mobile TV services include streaming live TV (news, weather forecasts etc.) and streaming video (such as video clips). All the above constitute a series of some indicative emerging applications that necessitate advanced transmission techniques. However, increased improvements have to be made both in the uplink and downlink transmission and in better radio resource management, in order to meet future demands and provide rich multimedia services to large users’ population. In addition, several obstacles, mainly regarding the interoperability and ubiquitous access between different access technologies and services, have to be overcome (thus leading to 4G). The main target of this dissertation is the study of power control issues, the development and the performance evaluation of an efficient power scheme for the provision of broadband, multicast services and applications to mobile users. This will be effectively implemented through the efficient use of MBMS and HSPA technologies in both 3G and its evolution LTE. An important aspect of this work is the investigation of the selection of the most efficient radio bearer for the transmission of MBMS multicast data. MBMS services can be provided in each cell by either multiple Point to Point (PTP) channels or by a single Point to Multipoint (PTM) channel. PTM transmission uses a single channel reaching down to the cell edge, which conveys identical traffic. On the other hand, PTP transmission uses dedicated channel allocated to each user, which conveys identical content. Obviously, a decision has to be made on the threshold between these two approaches. Therefore, improvements of the currently existing Counting Mechanism in MBMS will be studied. Although relative research work in this field considers the need for a power-based Counting Mechanism and not a UE-based Counting Mechanism, the case of HSDPA usage in such a power mechanism could be further investigated, taking also into account the availability of multi-mode cells. This could lead to an optimal scheme for the MBMS Counting Mechanism. The fundamental selection criterion of channel type is the amount of base station power required to transmit to a group of users. To this direction, the role of power control in the MBMS multicast transmission in UMTS is studied and analysed. A power control scheme for the efficient radio bearer selection in MBMS is then proposed. The choice of the most efficient transport channel in terms of power consumption is a key point for the MBMS since a wrong transport channel selection for the transmission of the MBMS data could result to a significant decrease in the total capacity of the system. Various UMTS transport channels are examined for the transmission of the multicast data and a new algorithm is proposed for the more efficient usage of power resources in the base station

No description available.

A administração dos recursos educacionais nas instituições de ensino tem se tornado um problema logístico mediante o aumento da demanda pela utilização de salas, para aulas expositivas e laboratórios, para aulas práticas com recursos computacionais. Este trabalho apresenta um estudo para implementação de uma rede sem fio no padrão IEEE 802.11 em ambiente educacional, flexibilizando os recursos de sala de aula e laboratório de forma que em uma estrutura predial única as salas possam ser montadas como laboratórios ou salas de aula em função da necessidade. Para realizar esse estudo, foram realizados testes de comunicação entre os dispositivos, em um ambiente educacional utilizando recursos e equipamentos com a capacidade de analisar o sinal de propagação do radio no ambiente. Verificou-se que o estudo do ambiente em função da propagação do sinal da rede sem fio, garante eficiência na comunicação de dados entre os recursos computacionais e a rede sem fio garantindo a eficiência do ambiente proposto e economia na sua implementação. / The administration of educational resources in educational institutions has become a logistical problem by increasing the demand for use of rooms, for lectures and laboratories, for practical classes with computing resources. This work presents a study for the design and implementation of a standard IEEE 802.11 wireless network in the educational environment, making the classroom and laboratory resources flexible, in a manner that in a single building structure the rooms can be mounted as classrooms or laboratories depending on the need. To carry out this study, tests were performed between communication devices in an educational environment using resources and equipment with the ability to analyze the radio signal propagation in the environment. It was found that the study of the environment depending on the signal propagation of the wireless network ensures greater efficiency in data communication between computing resources and wireless network, ensuring the efficiency of the proposed environment and economy in implementation.