Teses / dissertações sobre o tema "Decentralized transmission"

The remarkable evolution of wireless networks into the next generation to provide ubiquitous and seamless broadband applications has recently triggered the emergence of Wireless Mesh Networks (WMNs). The WMNs comprise stationary Wireless Mesh Routers (WMRs) forming Wireless Backbone Mesh Networks (WBMNs) and mobile Wireless Mesh Clients (WMCs) forming the WMN access. While WMCs are limited in function and radio resources, the WMRs are expected to support heavy duty applications : that is, WMRs have gateway and bridge functions to integrate WMNs with other networks such as the Internet, cellular, IEEE 802.11, IEEE 802.15, IEEE 802.16, sensor networks, et cetera. Consequently, WMRs are constructed from fast switching radios or multiple radio devices operating on multiple frequency channels. WMRs are expected to be self-organized, self-configured and constitute a reliable and robust WBMN which needs to sustain high traffic volumes and long "online" time. However, meeting such stringent service expectations requires the development of decentralized dynamic transmission power control (DTPC) approaches. This thesis addresses the DTPC problem for both single and multiple channel WBMNs. For single channel networks, the problem is formulated as the minimization of both the link-centric and network-centric convex cost function. In order to solve this issue, multiple access transmission aware (MATA) models and algorithms are proposed. For multi-radio multi-channel (MRMC) WBMNs, the network is modelled as sets of unified channel graphs (UCGs), each consisting of interconnected active network users communicating on the same frequency channel. For each UCG set, the minimization of stochastic quadratic cost functions are developed subject to the dynamic Link State Information (LSI) equations from all UCGs. An energy-efficient multi-radio unification protocol (PMMUP) is then suggested at the Link-Layer (LL). Predictive estimation algorithms based on this protocol are proposed to solve such objective functions. To address transmission energy and packet instabilities, and interference across multiple channels, singularly-perturbed weakly-coupled (SPWC) control problems are formulated. In order to solve the SPWC transmission power control problem, a generalized higher-order recursive algorithm (HORA) that obtains the Riccati Stabilizing Solutions to the control problem is developed. The performance behaviours of the proposed models and algorithms are evaluated both analytically and through computer simulations. Several simulations are performed on a large number of randomly generated topologies. Simulation and analytical results confirm the efficacy of the proposed algorithms compared to the most recently studied techniques

Abstract This thesis focuses on transceiver optimization for heterogeneous multi-user multiple-input multiple-output (MIMO) wireless communications systems. The aim is to design decentralized beamforming methods with low signaling overhead for improved spatial spectrum utilization. A wide range of transceiver optimization techniques are covered, with particular consideration of decentralized optimization, fast convergence, computational complexity and signaling limitations. The proposed methods are shown to provide improved rate of convergence, when compared to the conventional weighted minimum MSE (WMMSE) approach. This makes them suitable for time-correlated channel conditions, in which the ability to follow the changing channel conditions is essential. Coordinated beamforming under quality of service (QoS) constraints is considered for interfering broadcast channel. Decomposition based decentralized processing approaches are shown to enable the weighted sum rate maximization (WSRMax) in time-correlated channel conditions. Pilot-aided decentralized WSRMax beamformer estimation is studied for coordinated multi-point (CoMP) joint processing (JP). In stream specific estimation (SSE), all effective channels are individually estimated. The beamformers are then constructed from the locally estimated channels. On the other hand, with direct estimation (DE) of the beamformers, only the intended signal needs to be separately estimated and the covariance matrices are implicitly estimated from the received pilot training matrices. This makes the pilot design more robust to pilot contamination. These methods show that CoMP JP is feasible even in relatively fading channel conditions and with limited backhaul capacity by employing decentralized beamformer processing. In the final part of the thesis, a relay-assisted cellular system with decentralized processing is considered, in which users are served either directly by the base stations or via relays for WSRMax or sum power minimization subject to rate constraints. Zero-forcing and coordinated beamforming provide a trade-off between complexity, in-band signaling and spectrum utilization. Relays are shown to be beneficial in many scenarios when the in-band signaling is accounted for. This thesis shows that decentralized downlink MIMO transceiver design with a reasonable computational complexity is feasible in various system architectures even when signaling resources are limited and channel conditions are moderately fast fading
Tiivistelmä Tämä väitöskirja keskittyy lähetin- ja vastaanotinoptimointiin heterogeenisissä monikäyttäjä- ja moniantennijärjestelmissä. Tavoitteena on parantaa tilatason suorituskykyä tutkimalla hajautettuja keilanmuodostusmenetelmiä, joissa ohjaussignaloinnin tarve on alhainen. Erityisesti keskitytään hajautetun keilanmuodostuksen optimointiin, nopeaan konvergenssiin, laskennalliseen kompleksisuuteen sekä signaloinnin rajoitteisiin. Esitettyjen menetelmien osoitetaan parantavan konvergenssinopeutta ja vähentävän signaloinnin tarvetta, verrattaessa tunnettuun WMMSE-menetelmään. Nämä mahdollistavat lähetyksen aikajatkuvissa kanavissa, joissa kanavan muutosten seuraaminen on erityisen tärkeää. Näiden menetelmien osoitetaan mahdollistavan hajautetun ja priorisoidun tiedonsiirtonopeuden maksimoinnin monisolujärjestelmissä sekä aikajatkuvissa kanavissa käyttäjäkohtaisilla siirtonopeustakuilla. Pilottiavusteisten lähetys- ja vastaanotinkeilojen estimointia tutkitaan yhteislähetysjärjestelmissä. Yksittäisten lähetyskanavien estimoinnissa effektiiviset kanavat estimoidaan yksitellen, ja lähetys- ja vastaanotinkovarianssimatriisit muodostetaan summaamalla paikalliset kanavaestimaatit. Suoraestimoinnissa ainoastaan oman käyttäjän effektiivinen kanava estimoimaan erikseen. Tällöin kovarianssimatriisit saadaan suoraan vastaanotetuista pilottisignaaleista. Tämä tekee estimaateista vähemmän herkkiä häiriölle. Hajautetun yhteislähetyksen osoitetaan olevan mahdollista, jopa verrattain nopeasti muuttuvissa kanavissa sekä rajallisella verkkoyhteydellä lähettimien välillä. Viimeisessä osassa tutkitaan välittäjä-avusteisia järjestelmiä, joissa käyttäjiä palvellaan joko suoraan tukiasemasta tai välittäjä-aseman kautta. Optimointikriteereinä käytetään siirtonopeuden maksimointia sekä lähetystehon minimointia siirtonopeustakuilla. Nollaanpakottava sekä koordinoitu keilanmuodostus tarjoavat valinna laskennallisen kompleksisuuden, ohjaussignaloinnin sekä suorituskyvyn välillä. Välittäjä-avusteisen lähetyksen osoitetaan olevan hyödyllisiä useissa tilanteissa, kun radiorajanpinnan yli tapahtuvan signaloinnin tarve otetaan huomioon keilanmuodostuksessa. Tässä väitöskirjassa osoitetaan hajautetun keilanmuodostuksen olevan mahdollista verrattaen vähäisillä laskennallisilla resursseilla heterogeenisissä moniantennijärjestelmissä. Esitetyt menetelmät tarjoavat ratkaisuja järjestelmiin, joissa ohjaussignalointiresurssit ovat rajallisia ja radiokanava on jatkuvasti muuttuva

This thesis study focuses on transmission expansion planning (TEP) problem for restructured power systems and addresses challenges specifically in countries where electricity market is in developing phase after liberalization of power industry for establishing a competitive market, like Turkey. A novel multi-year TEP approach is developed which considers generation investment cost and transmission congestion level in the planning horizon. The model assesses the impact of generation investments on TEP problem. Benders decomposition methodology is utilized successfully to decompose the complex mixed-integer programming TEP problem into a master problem and two subproblems. Security subproblem assesses single-contingency criteria. Transmission congestion cost is considered within operational subproblem given that congestion level is a proper criterion for measuring competitiveness level of an electricity market. The proposed approach is applied to the Turkish power system. The proposed approach could be utilized to provide indicative plans, which might be quite necessary particularly during development of a competitive market. However, there is no guarantee that independent power producers (IPPs) will follow those plans which concern the maximization of social-welfare. Given the necessity of coordinating monopoly transmission and decentralized generator investment decisions, the proposed approach is improved further to include promoting decentralized generator investments through incentive payments. Such incentives might be necessary to trigger IPPs earlier than their projections, as illustrated by numerical examples including IEEE 30-bus system.

During the last two decades, significant efforts towards the deregulation of the electricity industry have been observed worldwide, involving the unbundling of vertically integrated monopoly utilities, the introduction of competition in the generation and supply sectors, and the open access to the electricity network. In contrast with traditionally regulated paradigm, deregulation calls for more involving participants for bringing more competition. In order to facilitate the participation of large number of players, a novel market structure, where individual player seeking for its own interest, is proposed by a project called 'Autonomic Power System'; according to which, the new structure will accommodate both the operation(short-term) and investment(long-term) need for the future complex electricity market in decentralised pattern. Specifically, players are encouraged to enter the market and participate in the sectors they are interested in. Players can be existing and new generating units, demand suppliers that represent aggregated customers and even merchant companies who are neither generating units nor demand suppliers. The sectors they could participate include power scheduling, generation investment and transmission network investment etc. Game theory and Agent-based modelling are both good tools to model the behaviours of numerous players and their mutual effect with each other. A central entity will be present for reconciling conflicting objectives if necessary. In this thesis, due to the incompetence in allocating investment cost among system users given traditional centralised planning paradigm, we mainly focus on proposing methods for decentralised investing in the network; under which circumstance, transmission planning will rely on market forces and profit-driven decisions of self-interested players. This paradigm will gain continuous grounds as it accounts for the interests of the different market agents and is deemed as a further step towards the liberalisation and efficient operation of the electricity industry. An iterative method is employed to search for Nash equilibrium of the game and a heuristic approach is adopted for deriving a coordinated solution when no or multiple NE are reached. Case studies will demonstrate the individual investment intentions for different situations and the physical/economic significance of the obtained solutions.

När fler människor flyttar ut till sina fritidshus och bor där hela året om bildas så kallade omvandlingsområden där användningen av vatten och avlopp förändras. Detta leder ofta till högre vattenanvändning och kraven på avloppssystemen ökar därmed. Det finns tre huvudtyper av lösningar som vanligtvis används för att möta kravet på bättre avloppssystem i omvandlingsområden: enskilda lösningar på varje fastighet, en samfälld lösning eller en lösning i kommunal regi. Syftet med studien var att utvärdera kostnader för VA-system i omvandlingsområden i Sverige. Fem olika områden studerades med avseende på beräknade kostnader jämfört med det verkliga utfallet. Beräkningar gjordes på totala investeringskostnader, kostnad per fastighet såväl som kapitalkostnad och drift- och underhållskostnad. Jämförelser gjordes också med andra lösningar som var aktuella innan området byggde ut den valda VA-lösningen. Arbetet berörde även metodiken för hur kommuner väljer VA-system i omvandlingsområden. Det var billigare för en samfällighetsförening, 1 000 kr/m, att gräva ledningar än för en kommun, 4 400 - 5 900 kr/m. Grundare ledningsgravar var en av orsakerna till detta. En annan slutsats var att befintlig infrastruktur från tidigare VA-system kan göra samma typ av VA-system billigare om delar av det befintliga fortfarande är i gott skick. Driftkostnaden för enskilda system beror mycket på hur många personer som nyttjar systemet och under hur stor del av året. Vid samtal med kommuner framkom det att valet av VA-system i omvandlingsområden i regel inte föregås av en jämförelse mellan olika VA-system. Istället är det oftast en överföringsledning till ett befintligt kommunalt nät som väljs.
More and more people choose to live permanently in houses built as vacation houses, thereby creating transition areas. The increased occupancy in the houses tends to lead to larger water usage and often demands improved wastewater systems. There are three main ways in which this demand usually is met: each property builds an on-site system, the properties jointly build a facility through a community association, or the properties connect to the municipality’s network. The aim was to evaluate the costs of water and wastewater systems in transition areas in Sweden. This was done by studying five different improved transition areas and comparing the estimated costs with the actual cost of the systems. Both total investment costs and cost per property were calculated, as well as capital costs, and operation and maintenance costs. How the municipalities choose the sanitation system to be implemented was also a part of the study.  It was much more expensive for the municipality to build pipes than for a community association. One reason for this was shallower pipe placement. Another conclusion was that if part of a sanitation system already exists and is in good shape, this will lead to lower investment costs for a new system using that part. The operation costs for on-site systems on each property will be much higher for a family living there permanently, compared to that of a family living there only part time. Municipalities in Sweden generally do not compare different types of systems before deciding on an improved water and sanitation system in a transition area. Instead they almost always build a transmission line for water and wastewater to connect the area to an already existing centralized system.

This thesis presents a comprehensive study of a smart aircraft double panel for active vibroacoustic control. The control of the double panel vibration is implemented using Multi-Input-Multi-Output (MIMO) decentralised velocity feedback loops. The loops are applied via an array of electrodynamic force actuators and collocated velocity sensors. The actuators are located in an air cavity between the two panels such that they can react against the two panels. Two velocity sensors per actuator are used. Either sensor is located at the source and radiating panel footprint of an actuator. The error velocity is formed by subtracting weighted sensor outputs. In the introductory part of the thesis a survey of aircraft interior noise is given, and stateof- the-art passive and active noise control methods are presented. In Chapter two the mathematical model for the theoretical analysis of the smart double panel is formulated and a parametric study of passive sound transmission is performed using the mathematical model. In Chapter three the performance of decentralised feedback control systems using absolute and relative velocity is analysed theoretically. In Chapter four the stability and performance of decentralised feedback control systems using reactive actuators driven with weighted velocity error signals is analysed theoretically. In Chapter five the stability of decentralised feedback control systems using weighted velocity error signals and electrodynamic reactive actuators is analysed experimentally. In Chapter six the performance of decentralised feedback control systems using weighted velocity error signals and reactive actuators is analysed experimentally.

Face à la prolifération des technologies mobiles et à l’augmentation du volume des données utilisées par les applications mobiles, les périphériques consomment de plus en plus de bande passante. Dans cette thèse, nous nous concentrons sur les réseaux Wi-Fi denses comme cela peut être le cas lors d’événements à grande échelle (ex: conférences, séminaire, etc.) où un serveur doit acheminer des données à un grand nombre de périphériques dans une fenêtre temporelle réduite. Dans ce contexte, la consommation de bande passante et les interférences engendrées par les téléchargements parallèles d’une donnée volumineuse par plusieurs périphériques connectés au même réseau dégradent les performances. Les technologies de communication Device-to-Device (D2D) comme Bluetooth ou Wi-Fi Direct permettent de mieux exploiter les ressources du réseau et d’améliorer les performances pour offrir une meilleure qualité d’expérience (QoE) aux utilisateurs. Dans cette thèse nous proposons deux approches pour l’amélioration des performances de la dissémination de données. La première approche, plus adaptée à une configuration mobile, consiste à utiliser des connexions D2D en point-à-point sur une topologie plate pour les échanges de données. Nos évaluations montrent que notre approche permet de réduire les temps de dissémination jusqu’à 60% par rapport à l’utilisation du Wi-Fi seul. De plus, nous veillons à avoir une répartition équitable de la charge énergétique sur les périphériques afin de préserver les batteries les plus faibles du réseau. Nous avons pu voir qu’avec la prise en compte de l’autonomie des batteries et de la bande passante, la sollicitation des batteries les plus faibles peut être réduite de manière conséquente. La deuxième approche, plus adaptée à des configurations statiques, consiste à mettre en place des topologies hiérarchiques dans lesquelles on regroupe les périphériques par clusters. Dans chaque cluster, un périphérique est élu pour être le relais des données qu’il recevra depuis le serveur et qu’il transmettra à ses voisins. Cette approche permet de gérer plus efficacement les interférences en adaptant la puissance du signal afin de limiter la portée des clusters. Dans ce cas, nous avons observé jusqu’à 30 % de gains en temps de dissémination. Dans la continuité des travaux de cette thèse, nous discutons de plusieurs perspectives qu’il serait intéressant d’entreprendre par la suite, notamment l’adaptation automatique du protocole de dissémination à l’état du réseau et l’utilisation simultanée des deux types de topologie plate et hiérarchique
We are witnessing a proliferation of mobile technologies and an increasing volume of data used by mobile applications. Devices consume thus more and more bandwidth. In this thesis, we focus on dense Wi-Fi networks during large-scale events (such as conferences). In this context, the bandwidth consumption and the interferences caused by the parallel downloads of a large volume of data by several mobile devices that are connected to the same Wi-Fi network degrade the performance of the dissemination. Device-to-Device (D2D) communication technologies such as Bluetooth or Wi-Fi Direct can be used in order to improve network performance to deliver better QoE to users. In this thesis we propose two approaches for improving the performance of data dissemination. The first approach, more suited to a dynamic configuration, is to use point-to-point D2D connections on a flat topology for data exchange. Our evaluations show that our approach can reduce dissemination times by up to 60% compared to using Wi-Fi alone. In addition, we ensure a fair distribution of the energy load on the devices to preserve the weakest batteries in the network. We have observed that by taking into account the battery life and the bandwidth of mobile devices, the solicitation of the weakest batteries can be reduced significantly. The second approach, more adapted to static configurations, consists in setting up hierarchical topologies by gathering mobile devices in small clusters. In each cluster, a device is chosen to relay the data that it receives from the server and forwards it to its neighbors. This approach helps to manage interference more efficiently by adjusting the signal strength in order to limit cluster reach. In this case, we observed up to 30% gains in dissemination time. In the continuity of this thesis work, we discuss three perspectives which would be interesting to be undertaken, in particular the automatic adaptation of the dissemination to the state of the network and the simultaneous use of both topology types, flat and hierarchical

Chan Chi Yuk.
Thesis (M.Phil.)--Chinese University of Hong Kong, 2004.
Includes bibliographical references (leaves 41-42).
Abstracts in English and Chinese.
Acknowledgement --- p.i
Abstract --- p.ii
摘要 --- p.iii
Chapter Chapter 1 --- Introduction --- p.1
Chapter Chapter 2 --- Background --- p.4
Chapter 2.1 --- Server-less Video Streaming Architecture --- p.4
Chapter 2.2 --- Network Congestion --- p.6
Chapter Chapter 3 --- Network-Neutral Schedulers --- p.9
Chapter 3.1 --- Randomized Scheduler --- p.9
Chapter 3.2 --- Staggered Scheduler --- p.10
Chapter 3.3 --- Staggered-on-Request Scheduler --- p.11
Chapter Chapter 4 --- A Model for Transmission Scheduling --- p.13
Chapter 4.1 --- Matrix Representation --- p.13
Chapter 4.2 --- Parameter Estimation --- p.17
Chapter Chapter 5 --- Network Aware Schedulers --- p.20
Chapter 5.1 --- Gradient Descent Scheduler --- p.20
Chapter 5.2 --- Least Schedulable First Scheduler --- p.23
Chapter 5.3 --- Performance Analysis --- p.26
Chapter Chapter 6 --- Performance Evaluation --- p.30
Chapter 6.1 --- Sensitivity to Clock Jitter --- p.32
Chapter 6.2 --- Sensitivity to System Size --- p.34
Chapter 6.3 --- Sensitivity to System Utilization --- p.35
Chapter 6.4 --- Sensitivity to Delay Variation --- p.36
Chapter 6.5 --- Sensitivity to Router Buffer Size --- p.38
Chapter Chapter 7 --- Conclusions --- p.39
Bibliography --- p.41

Context. Scalability and bittrate is an large concern when build-ing infrastructure and application for video content delivery. Manyresearch and companies have for a long time looked at peer to peertechnology as a way of solving the issue by utilizing the clients capac-ity.Objectives. The first objectives is to see if Dat protocol would be agood fit for video file delivery. Comparing with the widely used HTTPtoo see the differences in scalability and bitrate. The challenges withimplementing such a solution and tactic for the future if choosing to.Methods. In order to achieve the objectives of our research a compar-ing network experiment in similar manners and with the same clientbase was conducted.Conclusions. The Dat protocol show good scalability and perfor-mance especially on larger number of clients. Some future works suchas peer-selecting and load balancing are needed before Dat can be usedas protocol for video delivery on commerical sites.Keywords:P2P, Decentralized, Video, conten

The field buses, and particularly the ‘PROFIBUS’, are currently widely used in automation systems, with the intention to automate industrial applications. It is of the utmost importance that one should understand how these systems operate, because failure to understand may result in improper applications, which can ultimately lead to intense network problems and, consequently, lead to potential catastrophic failures in industrial equipment, as well as compromising the health and safety of the people. This research was the performance evaluation of SAMANCOR PROFIBUS network that controls the chrome manufacturing plant. The problem with the network was that it was failing intermittently. These network failures resulted in loss of production, loss of throughput, compromised quality, downtime due to reworks, high costs in energy used to rework, and equipment damage or failure. One of the OBJECTIVES of the research was to carry out a performance evaluation of the PROFIBUS network in terms of the possible electromagnetic interference (EMI) within the plant’s PLC network. This topic emanated from the network service providers that kept insisting that the network was unstable, due to possible electromagnetic interference caused by possible high voltage cables running next to the plant network cables. This assumption was without fact, and hence the research was conducted. The QUANTITATIVE research method was used to conduct the research, where simulation of the plant network, using external parameters, were used to carry out the research. Furthermore, experiments were conducted and the physical measurements were performed on the network, where parameters derived from these measurements were used to compare the two networks. In essence, the network was tested under known configurations. The manner in which the network was simulated was that of stepping up the electrical current from the external device, and recording the response of the network. A stand-alone network rig was built and used to carry out the tests, and the results were compared with those obtained from the plant network.
Electrical and Mining Engineering
M. Tech. (Electrical Engineering)