First-generation, line-of-sight (LOS) fixed broadband wireless access techniques have been around for several years. However, services based on this technology have been limited in scope to service areas where transceivers can communicate with their base stations, unimpeded by trees, buildings and other obstructions. This limitation has serious consequences in that the system can deliver only 50% to 70% coverage within a given cell radius, thus affecting earned revenue. Next generation broadband fixed wireless access techniques are aimed at achieving a coverage area greater than 90%. To achieve this target, these techniques must be based on a point-to-multipoint (PMP) cellular architecture with low base station antennas, thus possessing the ability to operate in true non-line-of-sight (NLOS) conditions. A possible limiting factor for these systems is link degradation due to interference. This thesis presents a new model to estimate the levels of co-channel interference for such systems operating within the 3.5 GHz multichannel multipoint distribution service (MMDS) band. The model is site-specific in that it uses statistical building/roof height distribution parameters obtained from practically modeling several metropolitan cities in the U.S. using geographic information system (GIS) tools. This helps to obtain a realistic estimate and helps analyze the tradeoff between cell radius and modulation complexity. Together, these allow the system designer to decide on an optimal location for placement of customer premises equipment (CPE) within a given cell area. / Master of Science

近年來科技匯流發展日行千里，新興無線寬頻的接取技術（Broadband Wireless Access）不斷升級，為民眾的生活帶來更便利的創新應用，而寬頻接取服務的亦由以往一種技術提供一種服務的方式，逐漸轉換為涵蓋數據（Data）、語音（Voice）及影音內容（Video）等三種服務的匯流。加速了電信、廣電與網路通訊產業升級的需求，也帶來了新的市場動能與發展契機。 本研究以台灣為研究範本，以個案研究方法來探討在網路為基礎的數位匯流環境下數位生活之發展趨勢、個案公司科技產品未來的發展趨勢及因應策略。 而本研究發現未來家用閘道器產品市場，將會朝向整合家中所有可上網設備的整合性產品特性發展。亦將會是國內網通設備商值得切入的新領域。娛樂型家用閘道器，目前市場上多以機上盒(Set top box, STB)加上Router的功能型態出現，惟必須等待STB零售市場打開後，國內的廠商將會有機會創造更大利潤空間。而個案公司在研發方向應以Cable Docsis的核心技術為中心,從水平方向擴展至家庭網路的Home applications。追求更快的速度,更多元化的網路技術和更方便的寬頻服務。在縱向方面,我們則以完整的解決方案為主軸,往頭端CMTS技術和網管為發展重點。

In this research oriented master’s thesis we have proposed a future vision of ITS (Intelligent Transport Systems) by utilizing the novel concept of HWA (Heterogeneous Wireless Access). Our proposal is backed by the investigation of the results of experiments conducted at CERES (Centre for Research on Embedded Systems), Halmstad University, Sweden to evaluate the quality of communication for V2V and V2I by using the IEEE 802.11p standard. We have also identified the expected scenarios with need of any other communication technology in replacement of IEEE 802.11p for V2V and V2I communication. We have also investigated the relevant research projects, experiments and their results on the basis of predefined constraints. In the investigated research projects the concept of HWA has been correlated with our proposal of HWA for ITS. We have identified that for smooth integration of any communication technology with IEEE 802.11p, an efficient and smart vertical handover protocol or method will be required. We have presented a blue print of a custom designed vertical handover technique which can be implemented for future ITS with further enhancements and experimental evaluations. We have also evaluated the worst case scenarios to assess the suitability of the HWA for the ITS. We proposed few solutions based on the evaluation of communication scenarios for the integration of IEEE 802.11p with other wireless communication technologies. Finally we have provided some conclusions and suggested future researches which must be conducted to realize the dream of ITS with support of HWA.

Dans les réseaux d'accès sans fil, l'un des défis les plus récents est la réduction de la consommation d'énergie du réseau, tout en préservant la qualité de service perçue par les utilisateurs finaux. Cette thèse propose des solutions à ce problème difficile considérant deux objectifs, l'économie d'énergie et la minimisation du délai de transmission. Comme ces objectifs sont contradictoires, un compromis devient inévitable. Par conséquent, nous formulons un problème d’optimisation multi-objectif dont le but est la minimisation conjointe de la puissance consommée et du délai de transmission dans les réseaux sans-fil. La minimisation de la puissance est réalisée en ajustant le mode de fonctionnement des stations de base (BS) du réseau d’un niveau élevé de puissance d’émission vers un niveau d'émission plus faible ou même en mode veille. La minimisation du délai de transmission est réalisée par le meilleur rattachement des utilisateurs avec les BS du réseau. Nous couvrons deux réseaux sans-fil différents en raison de leur pertinence : les réseaux locaux sans-fil (IEEE 802.11 WLAN) et les réseaux cellulaires dotés de la technologie LTE. / In wireless access networks, one of the most recent challenges is reducing the power consumption of the network, while preserving the quality of service perceived by the end users. The present thesis provides solutions to this challenging problem considering two objectives, namely, saving power and minimizing the transmission delay. Since these objectives are conflicting, a tradeoff becomes inevitable. Therefore, we formulate a multi-objective optimization problem with aims of minimizing the network power consumption and transmission delay. Power saving is achieved by adjusting the operation mode of the network Base Stations (BSs) from high transmit power levels to low transmit levels or even sleep mode. Minimizing the transmission delay is achieved by selecting the best user association with the network BSs. We cover two different wireless networks, namely IEEE 802.11 wireless local area networks and LTE cellular networks.

L'explosion de demande de bande passante est une conséquence de l'augmentation du volume de trafic. Il est important de proposer des mécanismes pour transférer le trafic entre les réseaux interconnectés de manière efficace. D'autre part, il est prévu que les réseaux d'accès (optiques et mobiles) constituent les plus grands consommateurs d'énergie dans les réseaux optiques pour les dix prochaines années. Cette situation et l'impact croissant des réseaux sur l'environnement ont fait devenir l'efficacité énergétique dans les réseaux de télécommunications un thème important de recherche. Cette thèse se concentre donc sur la proposition de nouvelles solutions aux problèmes liées à l'augmentation du volume de trafic dans différentes segments des réseaux. Tout d'abord, nous avons étudié différents schèmes de transfert du trafic entre les réseaux interconnectes en utilisant la synchronisation. Puis, nous avons exploré la possibilité d'offrir différents services dans les réseaux intégrés optiques-mobiles. Nous avons présenté une nouvelle architecture pour la conception de l'unité de réseau optique (ONU). Ensuite, nous nous sommes focalisés sur l'économie de l'énergie et des solutions efficaces pour l'allocation de bande passante ont été proposées. Nous avons également proposé un algorithme qui fournit l'efficacité énergétique pour les récepteurs sans fil dans les ONUs hybride. Une analyse des performances en utilisant modèles de files d'attente a été présentée. Finalement, nous avons analysé le trafic hétérogène dans l'ONU hybride, et nous avons proposé un cadre pour un algorithme d'ordonnancement qui puisse mettre à jour les règles de service de façon dynamique / A big growth in the number of subscribers is increasing the traffic volume passing through each sector in a telecommunication network. Mechanisms are required to solve the traffic shift problem between two sectors of the network in an efficient way. Additionally, it is expected that the access networks (optical and wireless) will constitute the largest energy consumers among the networks for the next ten years. This situation and the increasing impact of networks on the environment have made become the energy efficiency in telecommunication networks an important theme for researches. This dissertation hence focuses on the proposition of novel solutions for deal with the problems due to the growing of traffic in different segments of the network. Firstly, we have studied the traffic shift between interconnected networks by using the synchronization as technique to solve this problem. Secondly, we have explored the possibility of provisioning different services over the integration of optical-wireless technologies, which has been considered as a promising candidate for the deployment of high-speed access networks. Architecture of design for the Optical Network Unit (ONU) is presented. Then, energy efficiency has been focused and effective bandwidth management solutions have been proposed. We have also proposed an energy efficiency algorithm for wireless receiver at hybrid ONUS. A performance analysis by queuing models was presented for the implementation of proposed solutions. Finally, we have analyzed the heterogeneous traffic at hybrid ONU, and we have proposed a framework for a scheduling algorithm considering the characteristics of different traffic sources

no / Multimedia applications in wireless networks are usually categorized into various classes according to their traffic patterns and differentiated Quality-of-Service (QoS) requirements. The traffic of heterogeneous multimedia applications often exhibits the Long-Range Dependent (LRD) and Short-Range Dependent (SRD) properties, respectively. The integrated scheduling scheme that combines Priority Queuing (PQ) and Generalized Processor Sharing (GPS) within a hierarchical structure, referred to as PQ-GPS, has been identified as an efficient mechanism for QoS differentiation in wireless networks and attracted significant research efforts. However, due to the high complexity and interdependent relationship among traffic flows, modelling of the integrated scheduling scheme poses great challenges. To address this challenging and important research problem, we develop an original analytical model for PQ-GPS systems under heterogeneous LRD and SRD traffic. A cost-effective flow decomposition approach is proposed to equivalently divide the integrated scheduling system into a group of Single-Server Single-Queue (SSSQ) systems. The expressions for calculating the queue length distribution and loss probability of individual traffic flows are further derived. After validating its accuracy, the developed model is adopted as an efficient performance tool to investigate the important issues of resource allocation and call admission control in the integrated scheduling system under QoS constraints.

Επιδίωξη της εργασίας είναι να ανακαλύψουμε κατά πόσο τα αναδυόμενα δίκτυα FWA τεχνολογίας που βασίζονται σε πρότυπα (standards-based) αυξάνουν τις ευκαιρίες ή αντίθετα τις απειλές στην ευρυζωνική επιχειρηματικότητα των παρόχων. Στην εργασία, τίθενται υπό σύγκριση οι δομές κόστους (cost structures) των δικτύων τεχνολογίας FWA και των δικτύων DSL τεχνολογίας. Επίσης, αναγνωρίζονται οι συνθήκες της αγοράς (market conditions) υπό τις οποίες η τεχνολογία FWA θα μπορούσε να γίνει μια πιο οικονομική και οικονομικά αποδοτική (cost-effective) επιλογή. Στο Κεφάλαιο 2 γίνεται μία γενική επισκόπηση των ευρυζωνικών δικτύων και υπηρεσιών, τίθενται υπό συζήτηση τα δίκτυα πρόσβασης και τονίζεται ο ρόλος του ρυθμιστή (regulator) και ο διαχωρισμός ανάμεσα στις επιχειρήσεις εκμετάλλευσης δικτύου και σε αυτές της εκμετάλλευσης της υπηρεσίας. Στο Κεφάλαιο 3, διατυπώνονται οι αρχιτεκτονικές των δικτύων της FWA τεχνολογίας, καθώς επίσης θέματα σχετικά με την τεχνολογία ραδιοεπικοινωνιών. Στο Κεφάλαιο 4, γίνεται εισαγωγή στις γενικές αρχές και μεθόδους για τη διαστασιοποίηση και το σχεδιασμό του δικτύου τεχνολογίας FWA. Επιπλέον, γίνεται εισαγωγή σε κατάλληλα μοντέλα που είναι απαραίττητα προκειμένου να προβλέψουμε με αξιοπιστία τον απαιτούμενο αριθμό των μερών εξοπλισμού δικτύωσης της FWA τεχνολογίας για συγκεκριμένες περιοχές εξυπηρέτησης. Στο Κεφάλαιο 5, γίνεται εισαγωγή σε μεθόδους και μοντέλα για οικονομικές αναλύσεις των ευρυζωνικών δικτύων πρόσβασης. Τελικά, στο Κεφάλαιο 6, γίνεται εφαρμογή των πληροφοριών και των μεθόδων των προηγούμενων κεφαλαίων για να ανακαλύψουμε την οικονομική δυνατότητα επίτευξης (economic feasibility) της ανάπτυξης του δικτύου FWA τεχνολογίας σε διαφορετικά είδη περιβαλλόντων. Οι αναλύσεις εκτελούνται για τρία διαφορετικά περιβαλλοντικά σενάρια, τόσο για την FWA τεχνολογία όσο και για τα ADSL δίκτυα. Στο Κεφάλαιο 7, δίνονται τα συμπεράσματα, οι συστάσεις, και οι εισηγήσεις για περαιτέρω μελέτη. / -

In this effort, we consider the performance of a dedicated short range communication (DSRC) system for inter-vehicle communications (IVC). The DSRC standard employs convolutional codes for forward error correction (FEC). The performance of the DSRC system is evaluated in three different channels with convolutional codes, regular low density parity check (LDPC) codes and quasi-cyclic (QC) LDPC codes. In addition, we compare the complexity of these codes. It is shown that LDPC and QC-LDPC codes provide a significant improvement in performance compared to convolutional codes. / Graduate

Les réseaux ad hoc de véhicules accueillent une multitude d’applications intéressantes. Parmi celles-ci, les applications d’info-divertissement visent à améliorer l’expérience des passagers. Ces applications ont des exigences rigides en termes de délai de livraison et de débit. De nombreuses approches ont été proposées pour assurer la qualité du service des dites applications. Elles sont réparties en deux couches : réseau et contrôle d’accès. Toutefois, ces méthodes présentent plusieurs lacunes. Cette thèse a trois volets. Le premier aborde la question du routage dans le milieu urbain. A cet égard, un nouveau protocole, appelé SCRP, a été proposé. Il exploite l’information sur la circulation des véhicules en temps réel pour créer des épines dorsales sur les routes et les connecter aux intersections à l’aide des nœuds de pont. Ces derniers collectent des informations concernant la connectivité et le délai, utilisées pour choisir les chemins de routage ayant un délai de bout-en-bout faible. Le deuxième s’attaque au problème d’affectation des canaux de services afin d’augmenter le débit. A cet effet, un nouveau mécanisme, appelé ASSCH, a été conçu. ASSCH collecte des informations sur les canaux en temps réel et les donne à un modèle stochastique afin de prédire leurs états dans l’avenir. Les canaux les moins encombrés sont sélectionnés pour être utilisés. Le dernier volet vise à proposer un modèle analytique pour examiner la performance du mécanisme EDCA de la norme IEEE 802.11p. Ce modèle tient en compte plusieurs facteurs, dont l’opportunité de transmission, non exploitée dans IEEE 802.11p. / The fact that vehicular ad hoc network accommodates two types of communications, Vehicle-to-Vehicle and Vehicle-to-Infrastructure, has opened the door for a plethora of interesting applications to thrive. Some of these applications, known as infotainment applications, focus on enhancing the passengers' experience. They have rigid requirements in terms of delivery delay and throughput. Numerous approaches have been proposed, at medium access control and routing layers, to enhance the quality of service of such applications. However, existing schemes have several shortcomings. Subsequently, the design of new and efficient approaches is vital for the proper functioning of infotainment applications. This work proposes three schemes. The first is a novel routing protocol, labeled SCRP. It leverages real-time vehicular traffic information to create backbones over road segments and connect them at intersections using bridge nodes. These nodes are responsible for collecting connectivity and delay information, which are used to select routing paths with low end-to-end delay. The second is an altruistic service channel selection scheme, labeled ASSCH. It first collects real-time service channels information and feeds it to a stochastic model that predicts the state of these channels in the near future. The least congested channels are then selected to be used. The third is an analytical model for the performance of the IEEE 802.11p Enhanced Distributed Channel Access mechanism that considers various factors, including the transmission opportunity (TXOP), unexploited by IEEE 802.11p.

Fixed Broadband Wireless Access (FBWA) is a technology aimed at providing high-speed wireless Internet access, over a wide area, from devices such as personal computers and laptops. FBWA channels are defined in the range of 1-20 MHz which makes the RF front end (RFE) design extremely challenging. In its pursuit to standardize the Broadband Wireless Access (BWA) technologies, IEEE working group 802.16 for Broadband Wireless Access has released the fixed BWA standard IEEE 802.16 – 2004 in 2004. This standard is further backed by a consortium, of leading wireless vendors, chip manufacturers and service providers, officially known as Wireless Interoperability for Microwave Access (WiMAX). In general, any wireless base station (BS), supporting a number of contiguous Frequency Division Multiplexed (FDM) channels has to incorporate an RF front end (RFE) for each RF channel. The precise job of the RFE is to filter the desired channel from a group of RF channels, digitize it and present it to the subsequent baseband system at the proper sampling rate. The system essentially has a bandpass filter (BPF) tuned to the channel of interest followed by a multiplier which brings the channel to a suitable intermediate frequency (IF). The IF output is digitized by an ADC and then brought to the baseband by an appropriate digital multiplier. The baseband samples, thus generated, are at the ADC sampling rate which is significantly higher than the target sampling rate, which is defined by the wireless protocol in use. As a result a sampling rate conversion (SRC) is performed on these baseband samples to bring the channel back to the target sampling rate. Since the input sampling rate need not be an integer multiple of the target sampling rate, Fractional SRC (FSRC) is required in most of the cases. Instead of using a separate ADC and IF section for each individual channels, most systems use a common IF section, followed by a wideband ADC, which operates over a wide frequency band containing a group of contiguous FDM channels. In this case a channelizer is employed to digitally extract the individual channels from the digital IF samples. We formally call this system a receiver channelizer. Such an implementation presents considerable challenge in terms of the computational requirement and of course the cost of the BS. The computational complexity further goes up for FBWA system where channel bandwidth is in the order of several MHz. Though such a system has been analyzed for narrow band wireless systems like GSM, to the best of our knowledge no analysis seems to have been carried out for a wideband system such as WiMAX. In this work, we focus on design of a receiver channelizer for WiMAX BS, which can simultaneously extract a group of contiguous FDM RF channels supported by the BS. The main goal is to obtain a simple, low cost channelizer architecture, which can be implemented in an FPGA. There are a number of techniques available in the literature, from Direct Digital Conversion to Polyphase FFT Filter Banks (PFFB), which can do the job of channelization. But each of them operates with certain constraints and, as a result, suits best to a particular application. Further all of these techniques are generic in nature, in the sense that their structure is independent of any particular standard. With regard to computational requirement of these techniques, PFFB is the best, with respect to the number of complex multiplications required for its implementation. But it needs two very stringent conditions to be satisfied, viz. the number of channels to be extracted is equal to the decimation factor and the sampling rate is a power of 2 times baseband bandwidth. Clearly these conditions may not be satisfied by different wireless communication standards, and in fact, this is not satisfied by the WiMAX standard. This gives us the motivation to analyze the receiver channelizer for WiMAX BS and to find an efficient and low cost architecture of the same. We demonstrate that even though the conditions required by PFFB are not satisfied by the WiMAX standard, we can modify the overall architecture to include the PFFB structure. This is achieved by dividing the receiver channelizer into two blocks. The first block uses the PFFB structure to separate the desired number of channels from the input samples. This process also achieves an integer SRC by a factor that is equal to the number of channels being extracted. This block generates baseband outputs whose sampling rates are related to their target sampling rate by a fractional multiplication factor. In order to bring the channels to their target sampling rate, each output from the PFFB block is fed to a FSRC block, whose job is to use an efficient FSRC algorithm to generate the samples at the target sampling rate. We show that the computational complexity, as compared to the direct implementation, is reduced by a factor, which is approximately equal to the square of the number of channels. After mathematically formulating the receiver channelizer for WiMAX BS, we perform the simulation of the system using a software tool. There are two basic motives behind the simulation of the system which has a mathematical model. Firstly, the software simulation will give an idea whether the designed system is physically realizable. Secondly, this will help in designing the logic for different blocks of the system. Once these individual blocks are simulated and tested, they can be smoothly ported onto an FPGA. For simulation purpose, we parameterize the receiver channelizer in such a way that it can be reconfigured for different ADC sampling rates and IF frequencies, by changing the input clock rate. The system is also reconfigurable in terms of the supported channel bandwidth. This is achieved by storing all the filter coefficients pertaining to each channel type, and loading the required coefficients into the computational engine. Using this methodology we simulate the system for three different IF frequencies (and the corresponding ADC sampling rates) and three different channel types, thus leading to nine different system configurations. The simulation results are in agreement with the mathematical model of the system. Further, we also discuss some important implementation issues for the reconfigurable receiver channelizer. We estimate the memory requirement for implementing the system in an FPGA. The implementation delay is estimated in terms of number of samples. The thesis is organized in five chapters. Chapter 1 gives a brief introduction about the WiMAX system and different existing channelization architecture followed by the outline of the proposed receiver channelizer. In chapter 2, we analyze the proposed receiver channelizer for WiMAX BS and evaluate its computational requirements. Chapter 3 outlines the procedure to generate the WiMAX test signal and specification of the all the filters used in the system. It also lists the simulation parameters and records the results of the simulation. Chapter 4 presents the details of a possible FPGA implementation. We present the concluding remarks and future research directions in the final chapter.