WiMAX發展至今已經制定出許多標準的規格，但在call admission control (CAC)、bandwidth request (BR)、bandwidth allocation和schedule的細節設計上並沒有標準的規劃和演算法。本文中，我們提出一個CAC機制叫作multi-modulation CAC。不同於目前大部分的CAC機制僅考慮到單一調變(modulation)的情況，我們的研究聚焦在多調變的環境上。並利用multi-modulation CAC改善傳統CAC無法在多調變底下正常運作的問題。我們提出的理論中，BS的CAC是藉由剩餘slot數決定是否要接受連線。最後，我們用網路模擬器NS-2 (network simulator version 2)作為測試實驗架構並分析評估實驗的系統效能。 / So far, WiMAX forum has worked out many specifications of the IEEE 802.16 standard. However, it does not have detailed mechanisms of connection admission control (CAC)、bandwidth request (BR)、bandwidth allocation and scheduling. In this thesis, we propose an admission control scheme called multi-modulation CAC. Rather than most CAC only considering the single modulation environment, our study focused on multi-modulation environment. We use the multi-modulation CAC to improve the traditional CAC can’t work well in multi-modulation environment. With the proposed scheme, base station performs connection admission control to decide whether or not to accept connection requests by number of the remained slot. Finally, we use NS-2 (network simulator version 2) as network simulator and develop an analytical model to evaluate the system performance.

La recrudescence et le déploiement de nouveaux services et applications dans les systèmes de communication, ainsi que le nombre toujours croissant d'utilisateurs, conduisent à une augmentation de la consommation d'énergie des réseaux et technologies de l'information et de la communication, ce qui contribue de façon significative au réchauffement climatique. Ainsi, pour satisfaire aux exigences énergétiques aussi bien pour les réseaux sans fil que filaires, de nouvelles approches doivent être développées. Dans un premier temps, nos travaux de recherche se focalisent sur les mécanismes d'allocation des ressources de systèmes point-à-point dans deux modes de transmission (mono-porteuse et multi-porteuses) avec pour objectif la minimisation de l'énergie consommée. Dans cette partie, nous présentons une nouvelle approche appelée ultra large bande (ULT) ainsi qu'un nouvelle métrique pour les systèmes de communication. En se basant sur cette nouvelle approche, des algorithmes d'allocation des ressources sont proposés afin d'améliorer l'efficacité énergétique des réseaux sans fil et des réseaux filaires, dont notamment les réseaux CPL (courant porteur en ligne).Dans un second temps, nous étudions les techniques impulsionnelles ultra large bande (ULB). Un simulateur logiciel de laisoon point-à-point ULB impulsionnelle, générique et paramétrable a été développé. L'objectif est d'améliorer l'efficacité énergétique d'une laison ULB. les différents paramètres du systèmes (largeur de l'impulsion, temps de garde, nombre d'impulsions transmises) sont exploités afin d'optimiser les performances du système. / The demand for new services and applications in communication systems, as well as the number of users, are steadily increasing. This growth invoves a great use of energy in information and communications technologies , which contributes significantly to global warming. Furthermore, to satisfy the energy requirements for both wired and wireless networks, new approaches must be developed..Firstly, our researches focus on resources allocation mechanisms in point-to-point systems for two transmission modes (single-carrier and multi-carrier) with the goal of minimizing the energy cosumption. In this part, we present a new approach called ultra wide time (UWT) and a new metric for communication systems. Based on this approach, efficient algorithms for resource allocation are proposed to improve energy efficiency in wireless and wired networks.

The fundamentals for continued growth of broadband wireless remain sound. According to the Ericsson’s official forecasts, the addressable global market of wireless internet broadband connectivity reaches to 320 million users by the end of 2010. The opportunity for BWA/WiMAX to serve those who want to switch to broadband service is huge in many parts of the world where wireline technologies may not be feasible.The current document (Capacity and Cell-range Estimation for Multitraffic Users in Mobile WiMAX) is prepared as a master’s program final thesis to peruse the service provision capabilities of Mobile WiMAX innovate technology in more details. An elaborate excerpt of the technical subjects of IEEE-802.16e-2005 standard is gathered in the first chapter to provide the reader with a practical concept of Mobile WiMAX technology. The following chapter is aimed to collect the required knowledge for WiMAX planning problem. An innovate methodology to calculate the system’s actual throughput and a traffic model for mixed application users are proposed with a step by step description to derive an algorithm to determine the maximum number of subscribers that each specific Mobile WiMAX sector may support. The report also contains a Matlab code –enclose in the appendix– that tries to implement the entire algorithm for different system parameter and traffic cases to ease the Mobile WiMAX planning problem. The last chapter introduces the mostly used propagation models that suit the WiMAX applications.The presented methodology would help those operators that plan to implement a wide coverage network in a city. Using the introduced methodology, service providers will be able to estimate the number of base stations and hence the network investment and profitability. / Uppsatsnivå: D

O padrão IEEE 802.16e é uma tecnologia emergente para redes de próxima geração com suporte à qualidade de serviço para usuários fixos e móveis. No contexto de aplicações móveis, a técnica OFDMA (Orthogonal Frequency Division Multiple Access) deve ser empregada para multiplexação de canais de rádio frequência, suportando a alocação simultânea do canal para múltiplos usuários. Porém, essa alocação, considerando a estrutura do quadro OFDMA, não é definida pelo padrão IEEE 802.16e. A maioria das pesquisas atuais sobre arquiteturas de escalonamento baseadas nessa técnica de multiplexação estão focadas na transmissão downlink ou consideram apenas parcialmente os aspectos decorrentes do emprego da técnica OFDMA. Sendo assim, neste trabalho é apresentada uma arquitetura de escalonamento hierárquica, com dois níveis, para transmissões uplink em redes IEEE 802.16e, baseadas em OFDMA. A arquitetura proposta aborda a divisão do subquadro uplink entre oportunidades de requisição de banda e oportunidades de transmissão de dados, no Nível 1, e a seleção das requisições de banda para atendimento, no Nível 2. A proposta considera, além da técnica de multiplexação do canal, as cinco classes de serviço previstas pelo padrão IEEE 802.16e e o mecanismo de alocação de banda definido para a tecnologia. Uma ferramenta de simulação foi desenvolvida para avaliar o desempenho da proposta, considerando os diferentes aspectos da arquitetura e comparando com trabalhos relacionados. A avaliação é realizada considerando métricas como atraso médio no atendimento de requisições, percentual de requisições descartadas e a utilização do quadro. / The IEEE 802.16e standard is an emerging next generation network technology, designed to provide guaranteed QoS to both fixed and mobile users. In the context of mobile users, OFDMA technique must be used to multiplex the radio frequency channel. This technique allows to allocate the channel to multiple users at the same time. However, details about this allocation, considering the OFDMA frame structure, are not defined by the IEEE 802.16e standard. In this context, most of the current researches found on literature focus on proposing scheduling architectures for downlink transmissions only. Furthermore, researches that consider uplink transmissions, typically consider OFDMA aspects only partially. Therefore, this work presents an hierarchical scheduling architecture designed for uplink transmissions. The proposed architecture is composed of two levels. In the Level 1 the architecture addresses the division of the uplink subframe in bandwidth request opportunities, and data transmission opportunities. Level 2 is used to select among the bandwidth request, those that will be served on the next uplink subframe. The proposal considers OFDMA multiplexing technique, the five classes of service defined for QoS provisioning, and the bandwidth allocation mechanism defined in IEEE 802.16e standard. In order to evaluate the behavior of the proposed architecture, a simulation tool was developed. The approach used for evaluation was to compare the performance of the proposed architecture with related works found in the literature. The performance evaluation considers metrics such as average delay for serving requests, requests discarded, and the overall frame utilization.

行動寬頻技術在21世紀這個人手一機的今日，為一非常重要且背後蘊藏龐大商業利益的產業。正因此等商機，使得行動寬頻技術標準，自2G、3G直到今日即將進入4G以來，始終存在複雜的授權糾紛，包括關鍵技術的認定、合理權利金費率的訂定，以至可能引發之競爭法規範問題，在在都顯示出此產業對人類社會的影響，以及業者、國家對此領域所投注之高度關注。 本論文以2G以來，各個通訊世代所生之授權紛爭為例，分析通訊標準制訂過程將會面臨的問題。並在最後檢視我國通訊產業之結構，就此特性來分析我國通訊業者之優勢與列勢。在行動通訊產業這種具有高度「贏者全拿（Winner takes all）」的領域中，我國業者究竟應如何在此種高度競爭的領域中生存，進而與國際接軌，當為我國政府與通訊業者須認真思考之議題。

Résumé : La thèse développe une contribution à la spécification, la modélisation et l'évaluation de mécanismes destinés à la fourniture de qualité de service dans les réseaux sans fil locaux et métropolitains. La première partie du travail concerne une modélisation en chaîne de Markov du protocole d'accès EDCA de IEEE 802.11e qui, par rapport aux modèles présents dans la littérature, ajoute des mécanismes du standard qui n'avaient pas été introduits (prise en compte explicite de la collision virtuelle) et corrige des erreurs de conception (prise en compte des périodes AIFS de la procédure de Backoff). Ce modèle a été rendu synthétique pour en faciliter l'usage (réductions réalisées à l'aide des règles de Beizer). Ce modèle a ensuite été utilisé pour définir un algorithme de contrôle d'admission hybride, intégrant dans son processus de décision un modèle analytique et des mesures de l'état du réseau. L'algorithme de contrôle d'admission ainsi développé a été en premier lieu validé puis comparé à d'autres algorithmes de contrôle d'admission par simulation sous ns-2. Notons aussi que nous avons proposé, une modification du comportement de EDCA face à une collision virtuelle assurant une meilleure équité aux catégories d'accès. Cette modification a été évaluée à l'aide du modèle. Une deuxième partie du travail consiste en la proposition pour WiMAX d'une architecture de gestion de bande passante pouvant fournir des garanties de qualité de service. Cette architecture se compose de trois parties interagissantes : 1- une gestion de la bande passante sous WiMAX assimilée à une classe de serveurs dite classe des serveurs latence-débit, 2- un mécanisme de requête-réponse de bande passante agrégée simplifiant la gestion de bande passante et la rendant plus flexible, 3- un protocole de contrôle d'admission associé à l'architecture et qui en garantit le bon fonctionnement. L'architecture ainsi conçue s'inscrit dans une prospective de réseaux hétérogènes sans fil (réseaux métropolitain WiMAX connectant entre eux et à Internet des réseaux locaux WiFi). C'est dans cette optique que s'inscrira la suite de notre travail. Elle consistera en la combinaison des mécanismes que nous proposons afin de fournir une solution complète de qualité de service pour des réseaux hétérogènes sans fil.

<p><p>In order to keep up with the increasing demand on speed and reliability in modern wireless systems, new standards have to be introduced. By using Multiple Input Multiple Output technology (MIMO) and Orthogonal Frequency Division Multiplexing (OFDM) technologies the performance can be increased dramatically. Forthcoming standards such as WLAN 802.11n, WiMax and 3GPP LTE are all taking advantage of MIMO technology. To perform realistic tests with these standards it is often not enough to run software simulations in for example Matlab. Instead, as many real world parameters as possible need to be included. This can be done using a testbed, like the LiUMIMO, that actually transmits and receives data through the air.</p><p>The LiUMIMO is designed as a Software Defined Radio (SDR), only the RF front end and the data log are implemented in hardware, while all signal processing will be performed in Matlab.</p></p>

<p>We are very thirsty in terms of everything to fulfil our needs in a sophisticated way, and this leads me choose the so called master thesis titled “Multihop Concept in Cellular Systems”.</p><p>This thesis introduces an approach towards the integration of relaying or multihop scheme in the next generation of cellular networks. In a multihop cellular architecture, the users send their data to the base station via relay station or with direct communication to the base station. These relay stations can either be the nomadic, fixed at specific location or users’ mobile station (i.e. mobile relay station). The main objective of this paper is to compare the difference between the relaying network architecture with different channel bandwidth as well as their performance gain. For this we integrate the relay station into conventional cellular networks using IEEE 802.16j (One of the standard introduced relay station concept in WiMAX) OFDMA (Orthogonal Frequency Division Multiple Access is a transmission technique that is based on many orthogonal subchannels (set of carriers) that transmits simultaneously). The results show that under certain conditions the throughput and coverage of the system has been increased with the introduction of the relay station in to cellular base station zone.</p>

This thesis presents a novel VLSI design of multi-code rate Low-Density Parity-Check code (LDPC) decoder for IEEE 802.16e standard. In order to support the different code rates adopted by the standard, this thesis proposes a programmable LDPC decoder architecture based on the edge-serial approach. This edge-serial architecture can perform the sequential check-node computation according to the internal sequence update commands. Any complex and irregular parity-check matrix can all be realized in the proposed architecture if the number of bit-nodes each check node connects does not exceed a certain bound. In addition to the high flexibility, this thesis also proposes several design optimization techniques suitable for the LDPC decoder. First, the designs of the LDPC decoders in the past all put more emphasis on the realization of check node function. This thesis instead applies a novel bit-node major approach which can lead to more compact design. Secondly, a fine-grain message update method is used which allows more rapid message passing such that the decoder can converge in less cycles. In addition, almost half of the message memory can be reduced. Furthermore, based on the bit-node major decoder design, the early termination scheme can be utilized to partially terminate the function of some bit nodes to reduce the decoding cycles. The other salient features also include the rescheduling of the message update order to allow the overlap of different decoding iterations in order to reduce effect of the possible message update hazard due to the long internal pipeline latency. Based on the proposed optimization methods, our experimental results show that the hardware cost can be reduced by 23.1% while the decoding cycles can be reduced by 27.4%. The proposed LDPC decoder architecture has been realized by using 0.18 &#x00B5;m technology with the total gate count of 316k. Our experimental shows that the proposed LDPC decoder can run up to 235 MHz and deliver the average of 116 Mbps throughput.

The high deployment and maintenance costs of last mile wireline networks (i.e., DSL and cable networks) have urged service providers to search for new cost-effective solutions to provide broadband connectivity. Broadband wireless access (BWA) networks, which offer a wide coverage area and high transmission rates in addition to their fast and low-cost deployment, have emerged as an alternative to last mile wireline networks. Therefore, BWA networks are expected to be deployed in areas with different terrain profiles (e.g., urban, suburban, rural) where wireless communication faces different channel impairments. This fact necessitates the adoption of various transmission technologies that combat the channel impairments of each profile. Implementation scenarios of BWA networks considered in this thesis are multicarrier-based direct transmission and single carrier-based cooperative transmission scenarios. The performance of these transmission technologies highly depends on how resources are allocated. In this thesis, we focus on the development of practical resource allocation schemes for the mentioned BWA networks implementation scenarios. In order to develop practical schemes, the imperfection of channel state information (CSI) and computational power limitations are among considered practical implementation issues. The design of efficient resource allocation schemes at the MAC layer heavily relies on the CSI reported from the PHY layer as a measure of the wireless channel condition. The channel estimation error and feedback delay renders the reported CSI erroneous. The inaccuracy in CSI propagates to higher layers, resulting in performance degradation. Although this effect is intuitive, a quantitative measure of this degradation is necessary for the design of practical resource allocation schemes. An approach to the evaluation of the ergodic mutual information that reflects this degradation is developed for single carrier, multicarrier, direct, and cooperative scenarios with inaccurate CSI. Given the CSI estimates and estimation error statistics, the presented evaluation of ergodic mutual information can be used in resource allocation and in assessing the severity of estimation error on performance degradation. A point-to-multipoint (PMP) network that employs orthogonal frequency division multiple access (OFDMA) is considered as one of the most common implementation scenarios of BWA networks. Replacing wireline networks requires not only providing the last mile connectivity to subscribers but also supporting their diverse services with stringent quality of service (QoS) requirements. Therefore, the resource allocation problem (i.e., subcarriers, rate and power allocation) is modeled as a network utility maximization (NUM) one that captures the characteristics of this implementation scenario. A dual decomposition-based resource allocation scheme that takes into consideration the diversity of service requirements and inaccuracy of the CSI estimation is developed. Numerical evaluations and simulations are conducted to validate our theoretical claims that the scheme maximizes resource utilization, coordinates with the call admission controller to guarantee QoS, and accounts for CSI inaccuracy. Cooperation has recently received great attention from the research community and industry because of its low cost and fast deployment in addition to the performance improvement it brings to BWA networks. In cooperative scenarios, subscribers cooperate to relay each other's signals. For this implementation scenario of BWA networks, a robust and constrained Kalman filter-based power allocation scheme is proposed to minimize power consumption and guarantee bit error probability (BEP) requirements. The proposed scheme is robust to CSI inaccuracy, responsive to changes in BEP requirements, and optimal in allocating resources. In summary, research results presented in this thesis contribute to the development of practical resource allocation schemes for BWA networks.