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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
251

The eve of Saint Agnes; symphonic poem for symphonic orchestra [after the poem of Keats] ... transcribed for two pianos

Johnson, Henry Pickens, 1911- January 1935 (has links)
No description available.
252

El baptisme, evolució històrico-litúrgica i qualitats artístiques i sacramentals de les piles baptismals de la província eclesiàstica de Barcelona

Serra Sanmiquel, Juan 16 June 2014 (has links)
Els motius que m’han mogut a fer aquest treball han estat dos. Primerament, he observat que no hi havia un estudi exhaustiu i unitari en el temps, sobre l’evolució del baptisme. És cert però, que hi ha moltes monografies sobre qüestions puntuals, estudis parcials, llibres sagramentals d’èpoques diverses, que evidencien que els rituals són els mateixos, o poc han canviat, etc. Per tant, el meu interès ha estat estudiar a fons i amb el màxim rigor històric possible per treure conclusions, els períodes històrics, sobretot els que van des dels inicis del cristianisme fins el segle XVI. He observat que a partir d’aquest segle els estudis eclesiàstics sobre el baptisme han patit una davallada en profunditat i en quantitat. Els Concilis de l’Església, generals i locals, aporten molta informació sobre qüestions doctrinals i de disciplina, força interessant per conèixer el que en pensaven a cada època, i quins eren els seus problemes, moltes vegades lligats a l’entorn social i polític del moment. Pensem que, durant segles, la societat vivia en una època de cristiandat que ho amarava tot. He intentat donar unes pinzellades sobre cada moment històric. L’Església, en el transcurs dels segles, ha sofert desavinences que han desembocat en separacions de grups cristians. Per tant, he estudiat les diferents confessions cristianes segons la seva incidència en la història i en el nostre entorn de la Província Eclesiàstica de Barcelona, sobre el fet concret de la celebració del baptisme: el per què el celebren i com el celebren. El segon motiu que m’ha empès a completar aquest treball, han estat les piles baptismals: l’objecte material concret on històricament s’hi ha desenvolupat el ritu del baptisme. Comencem pensant que antigament el baptisme s’havia de celebrar en aigua viva. La pràctica va desembocar a celebrar-lo en piscines d’immersió. Aquestes, amb el temps, van esdevenir més petites, on només hi cabia el nou batejat i no el celebrant, com era norma fer-ho en les piscines grans. Obligats per qüestions d’higiene, es va passar del bateig d’immersió al bateig d’infusió; i les piscines o piles, que ja eren de mida reduïda, encara es van reduir més, i només servien per col•locar-hi l’aigua i al mateix temps recollir-hi la que queia del cap del batejat. Tot i que el Concili Vaticà II ha dictat normes per a la celebració digne del sagrament del baptisme, avui en dia en moltes esglésies es bateja amb un gibrell o palangana. És interessant aquesta evolució històrica, ja que és paral•lela a l’evolució de les tendències artístiques de cada moment. Partint del principi que només els bisbats i les parròquies tenen encomanada la celebració del baptisme, s’han estudiat totes les piles baptismals que hi ha o hi ha hagut en aquests centres de culte, per tal de confeccionar una catalogació històrica i actual de les piles existents o que han existit. La informació necessària per desenvolupar aquest treball s’ha obtingut de documents existents en arxius, entrevistes personals i treball de camp, recollint informació in situ i creant un complet arxiu fotogràfic. S’hi ha incorporat tota la informació que s’ha pogut recollir de piles situades en ermites, monestirs, o oratoris particulars. I s’ha fet un paral•lelisme amb piles artístiques característiques fora de l’àmbit d’aquest estudi, a títol comparatiu. / Los motivos que me han llevado a desarrollar este trabajo han sido dos. En primer lugar, he observado que no existia un estudio exhaustivo y unitario en el tiempo, sobre la evolución del bautismo. Es cierto que existen muchas monografias sobre cuestiones puntuales, estudios parciales, libros sacramentales de distintas épocas, que ponen en evidencia que los rituales son los mismos, o poco han variado, etc. Por tanto, mi interés ha sido estudiar a fondo y con el máximo rigor histórico posible para extraer conclusiones, los períodos históricos, en especial los que van desde el inicio del cristianismo hasta el siglo XVI. A partir de este siglo los estudios eclesiásticos sobre el bautismo han sufrido un menoscabo, tanto en profundidad como en cualidad. Los Concilios de la Iglesia, generales y locales, aportan mucha información sobre cuestiones doctrinales y disciplinares, muy interesante para conocer lo que pensaban en cada época, y cuales eran sus problemas, muchas veces unidos al entorno social y político del momento. Durante siglos la sociedad vivia en una época de cristiandad que lo condicionaba todo. He intentado dar unas pautas sobre cada momento histórico. La Iglesia, en el devenir de los siglos, ha sufrido separaciones de grupos cristianos. Por tanto he estudiado las distintas confesiones cristianas según su incidencia en la historia y en el entorno de la Provincia Eclesiástica de Barcelona, sobre la cuestión concreta de la celebración del bautismo: el por que lo celebran y como lo celebran. El segundo motivo que me ha llevado a completar este trabajo, han sido las pilas bautismales: el objeto material donde históricamente se ha desarrollado el rito del bautismo. Antiguamente el bautismo tenia que celebrarse en agua viva. La práctica hizo que terminara por celebrarse en piscinas de immersión. Éstas, con el tiempo, se redujeron, y en ellas solamente podia entrar el bautizado y no el celebrante, como era norma hacerto en las piscinas grandes. Obligados por cuestiones de higiene, se pasó del bautismo de immersión al de infusión; y las piscinas o pilas, se redujeron aún más; solamente servian para colocar el agua, y al propio tiempo recoger la que caia de la cabeza del bautizado. El Concilio Vaticano II dictó normas para una digna celebración del bautismo. Pero, hoy en día en muchas iglesias se bautiza en una jofaina. Es intersante esta evolución histórica, paralela a la evolución de las tendencias artísticas de cada momento. Ya que solamente los obispados y las parroquias pueden bautizar, se han estudiado todas las pilas bautismales que tienen o han tenido estos centros de culto, confeccionando una catalogación histórica y actual de Las pilas existentes, o que han existido. La información necesaria para desarrollar este trabajo se ha obtenido de documentos existentes en archivos, entrevistas personales i trabajo de campo, recogiendo información in situ y creando un completo archivo fotográfico. Se ha incorporado la información que se ha podido recoger de pilas situadas en ermitas, monasterios, u oratorios. Paralelamente se han estudiado pilas bautismales características, que no entran en el àmbito de este estudio; solamente a título comparativo. / Two have been the reasons moved me to develop this research work. First, I have noticed that there was not a comprehensive study on the evolution of the Baptism over time although many monographs are written on punctual subjects, partial studies, sacramental books over time, etc., that make evidence the rituals are the same or they have little changed. My interest has been to study in depth and with maximum historical rigor in order to draw conclusions, the historical periods, especially those from the beginnings of Christianity until the sixteen century. I have observed that from this century ecclesiastical studies on the baptism have suffered a decline in depth and in quantity. The general and local Councils of the Church, provide much information on matter of doctrine and discipline, interesting enough in order to know the thought of every time, and what were the problems, very often linked to social and political environment of the time. We consider that, for centuries, the society was leaving an era of Christianity that drenched everything. I have tried to give an overview of each historical period. The disagreements the Church has suffered along the centuries have led to the separation of groups of Christians. Therefore, I have studied the different Christian confessions according to their effect on history and around the Ecclesiastical Province of Barcelona, on the specific fact of the celebration of the baptism: why to celebrate and how to celebrate. The second reason that has driven me to complete this research work has been the Baptismal Fonts: the particular material object where the rite of the baptism has developed. Formerly the baptism was to be held in living waters. The practice led to celebrate it in plunge pools. These, over time, became smaller where only fit the new baptized and not the celebrant, as was norm to do so in large pools. Obliged as a matter of hygiene, baptism by immersion moved to infusion baptism; and pools or baptismal fonts, which were already reduced in size, still further reduced, and only served to place the water and, at the same time, collect the water falling from the head of the baptized. Although the Second Vatican Council has issued rules for the dignified celebration of the sacrament of Baptism, nowadays in many churches are used bowls or basins. This historical evolution is interesting because it is parallel to the evolution of artistic trends of the time. Assuming that only the dioceses and parishes have been entrusted with the celebration of Baptism, in order to make an historical and current catalog of the existing and those that have existed, baptismal fonts have been studied all there are or there have been in these places of Worship. The informations in which is based this study has been obtained from written documents collected in archives, personal interviews and field work, collecting information “in situ” and creating a comprehensive photo archive. All information collected from baptismal fonts located in chapels, monasteries, shrines, private oratories, … has been incorporated. A parallelism has been done with other artistic baptismal fonts outside the scope of this study, as a comparison.
253

Μυασθένεια με anti-MuSK αντισώματα : επιδημιολογία και ανοσολογικά χαρακτηριστικά

Τσιάμαλος, Παντελής 09 October 2009 (has links)
Σκοποί της εργασίας ήταν η επιδημιολογική μελέτη της MuSK-MG (μυασθένεια με αντι-MuSK αντισώματα) στην Ελλάδα, ο προσδιορισμός των υποτάξεων των IgG αυτοαντισωμάτων της MuSK-MG, η επίδραση της χορήγησης 4 MuSK-MG ορών στον AChR (υποδοχέα ακετυλοχολίνης) των κυττάρων της μυϊκής κυτταρικής σειράς ΤΕ671 και ο προσδιορισμός των ανοσογόνων επιτόπων της MuSK. Η επιδημιολογική μελέτη της MuSK-MG έλαβε χώρα μεταξύ 1 Ιανουαρίου 1986 και 30 Ιουνίου 2006 κι αφορούσε σε 33 ασθενείς. Ο προσδιορισμός των υποτάξεων των IgG αυτοαντισωμάτων πραγματοποιήθηκε με ραδιοανοσοκατακρήμνιση στους ορούς 14 ασθενών. Ο προσδιορισμός των ανοσογόνων επιτόπων της MuSK πραγματοποιήθηκε συνθέτοντας το εξωκυτταρικό κομμάτι της MuSK με τη μέθοδο Geysen της σύνθεσης πεπτιδίων σε στερεά φάση κι ελέγχοντας, στη συνέχεια, με τη μέθοδο ELISA, τη δέσμευση μιας σειράς MuSK-MG ορών στο τμήμα της MuSK που συνθέσαμε. Η μέση ετήσια επίπτωση της MuSK-MG στην Ελλάδα ήταν 0,32 ασθενείς/εκατομμύριο πληθυσμού/έτος. Στις γυναίκες, η έναρξη της MuSK-MG εμφανίστηκε μετά τα 30, ενώ, στους άνδρες, η νόσος εμφανίζεται σε κάθε δεκαετία. Οι περισσότεροι ασθενείς εμφάνισαν συμπτώματα από τους προσωπικούς κι αυχενικούς μύες. Η συντριπτική πλειονότητα των αυτοαντισωμάτων της MuSK-MG ήταν IgG4 υποτάξης. Σχετικά με την επίδραση των 4 MuSK-MG ορών στον AChR, οι οροί αυτοί ήταν ανίκανοι στην πρόκληση αποδόμησης του AChR των κυττάρων. Τέλος, δεν κατέστη δυνατός ο προσδιορισμός των ανοσογόνων επιτόπων της MuSK, αφού υπήρχαν αμινοξικές αλληλουχίες, στις οποίες ο αρνητικός μάρτυρας του πειράματος δεσμευόταν ισχυρότερα σε σχέση με τους MuSK-MG ορούς που δοκιμάσαμε. / The purposes of this study were to determine the epidemiological characteristics of muscle-specific kinase-myasthenia gravis (MuSK-MG) in Greece, the IgG subclass of the anti-MuSK antibodies, the effect of 4 MuSK-MG sera on the AChR of the cells of muscle cell line TE671 and the immunodominant epitopes of MuSK. This population-based study was performed on MuSK-MG patients in Greece between 1 January 1986 and 30 June 2006. Epidemiological and clinical data for 33 patients were collected. In addition, the distribution of anti-MuSK IgG autoantibody subclasses in the sera of 14 patients was determined by immunoprecipitation. The determination of the immunodominant epitopes on MuSK was performed by synthesizing the extracellular part of MuSK via Geysen method of peptide synthesis. Then, we performed ELISA method in order to determine the epitopes. The average annual incidence was 0.32 patients/million population/year. In females, onset of MuSK-MG occurred after the age of 30, whilst, in males, the disease appears in any decade. Most patients presented with involvement of the facial and bulbar muscles. The vast majority of anti-MuSK antibodies were IgG4. As far as the the effect of 4 MuSK-MG sera on the AChR of the cells is concerned, these sera were incapable of destroying the AChR effectively. Finally, we did not determine the immunodominant epitopes on MuSK, as there were amino acid sequences on which the negative control was bound with greater affinity than the MuSK-MG sera we tested.
254

THE ROLE OF ALDEHYDE DEHYDROGENASE 2 IN NITRATE TOLERANCE

D'Souza, YOHAN 21 October 2008 (has links)
Organic nitrates such as glyceryl trinitrate (GTN) are commonly used to treat myocardial ischemia and congestive heart failure. GTN is proposed to act as a prodrug that requires bioactivation for pharmacological activity. However, continuous administration results in tolerance development, limiting its clinical usefulness. Aldehyde dehydrogenase 2 (ALDH2) has been proposed to be the primary enzyme responsible for GTN bioactivation, and ALDH2 inactivation has been proposed as the sole basis of nitrate tolerance. In the present study, we utilized an in vivo GTN tolerance model to investigate the role of ALDH2 in GTN bioactivation and tolerance. We assessed changes in ALDH2 protein, mRNA and activity levels in rat blood vessels during chronic GTN exposure (0.4 mg/hr for 6, 12, 24 and 48 hr) in relation to changes in vasodilator responses to GTN. A time-dependent decrease in both ALDH2 expression and activity occurred (80% in tolerant veins and 30% in tolerant arteries after 48 hrs exposure to GTN), concomitant with decreased vasodilator responses to GTN. However, after a 24 hr drug-free period following 48 hr GTN exposure, the vasodilator responses to GTN had returned to control values, whereas ALDH2 expression and activity were still markedly depressed. The dissociation between reduced ALDH2 activity and expression, and the duration of the impaired vasodilator responses to GTN in nitrate-tolerant blood vessels, suggest factors other than changes in ALDH2-mediated GTN bioactivation contribute to nitrate tolerance. / Thesis (Master, Pharmacology & Toxicology) -- Queen's University, 2008-10-03 16:14:49.313
255

METABOREFLEX-INDUCED FLOW IMPROVEMENT IS ABSENT IN OLDER MALES WITH TYPE II DIABETES

BRAVO, MICHAEL FRANCIS 02 February 2012 (has links)
Background: Exercise is widely recognized as the cornerstone of management of type II diabetes (T2D). However, it is also known that people with T2D have poor adherence to exercise regimens, which is largely thought to be because of poor exercise tolerance. Recent studies have suggested that this exercise intolerance may be caused by a reduction in exercising muscle blood flow. One physiological mechanism which could potentially contribute is the muscle metaboreflex (MMR). This mechanism is thought to be a pressure-based flow-improving mechanism, but as a result of reduced efficacy of vasodilators and sympatholytic agents, might in fact be restraining the flow-improvement in persons with T2D. Hypothesis: Persons with T2D would not improve exercising muscle blood flow upon MMR activation. This absence of flow-improvement will be due to an augmented vasoconstriction in the exercising muscle. Methods: T2D (n=7) and CTL (n=6) participants performed rhythmic forearm handgrip exercise at an intensity equivalent to 20% MVC for 9 minutes with and without the application of ischemic plantar flexion (IPF). Forearm blood flow (FBF), mean arterial pressure (MAP), cardiac output (CO), heart rate (HR), total peripheral resistance (TPR) and forearm vascular conductance (FVK) were quantified for the last thirty seconds of each of four time points during the protocol. Plasma norepinephrine was measured via deep venous and arterialized venous blood sampling. Results: Steady state exercising FBF was increased in CTL but not in T2D during MMR activation (mean ± SE mL/min: CTLControl 161.16 ± 5.95, CTLMMR 212.72 ± 9.49, T2DControl 156.71 ± 13.08, T2DMMR 144.22 ± 10.55). This occurred despite similar increases in MAP, CO, HR, and TPR (across groups and treatment conditions, NS). FVK increased in CTL during the MMR protocol compared to the Control protocol, but decreased in the T2D group using the same comparison (mean ± SE mL/min/100 mm Hg: CTLControl 144.74 ± 5.63, CTLMMR 176.76 ± 11.99, T2DControl 143.29 ± 13.44, T2DMMR 103.53 ± 8.44). Conclusions: In the exercise model utilized, persons with T2D do not demonstrate the MMR-induced flow improvement seen in CTL. This impaired muscle blood flow in T2D is the result of MMR induced exercising limb vasoconstriction. / Thesis (Master, Kinesiology & Health Studies) -- Queen's University, 2012-01-31 09:30:42.604
256

Characterization of IL-2 inducible cytotoxic LAK function in HIV-1 infected individuals

Gryllis, Chryssa January 1992 (has links)
Inducible LAK cell responses were studied in HIV-seropositive individuals lacking clinical symptoms, and overt AIDS patients. Inducible LAK cell responses have been operationally defined as, non-MHC-restricted and antigen-nonspecific cytotoxic activity observed following IL-2 stimulation. HIV-seropositive asymptomatic individuals exhibited an enhanced LAK cell response against HIV-infected targets while lysis of uninfected targets remained at control levels. LAK activity of AIDS patients however, was significantly diminished when compared to healthy controls. Immunomagnetic negative selection depletion experiments indicated that LAK cell activity is mediated primarily by CD56-expressing lymphocytes, both at the progenitor and effector cell level. Of interest, in HIV-seropositive asymptomatic individuals we observed the emergence of a second CD8-expressing cytotoxic population that mediates IL-2-induced non-MHC-restricted and antigen-nonspecific cytotoxicity. Overall we demonstrated that CD56-expressing LAK cells of HIV-seropositive patients exhibited a decreased ability to mediate cytotoxicity on a per cell basis against a panel of different targets. In vivo, this inhibition may be amplified by decreases in absolute numbers of CD56-expressing lymphocytes per ml of blood. HIV-infection therefore results in dramatic changes on the number, function and phenotype of the effector cells mediating IL-2 inducible LAK cell responses.
257

Context-Aware Handoff Support for Wireless Access Networks

Mokhesi, Lekometsa 01 December 2010 (has links)
The phenomenal emergence of several heterogeneous wireless networks and technologies has allowed users to have access IP services anywhere at anytime from any network with whatever terminal they use. This computing platform has also been driven by the rapid evolution of mobile devices that are equipped with multiple network interfaces and the development of IP based applications. One of the challenging tasks with this Next-Generation Networks (NGN) computing platform is service continuity when users roam around different wireless networks e.g. Wi-Fi, Bluetooth and Cellular networks. This challenge is elevated more when dealing with applications that distribute time continuous data with stringent Quality of Service (QoS) requirements. One of the adaptation methods to ensure service continuity by minimizing flow interruptions when users are mobile is session handoff. The main contribution of the thesis is to present a handoff support system which implements a handoff decision engine using a Multi-Criteria Decision Making (MCDM) method based on a Bayesian Belief Network (BBN) and a handoff execution procedure based on buffering and doublecasting techniques. The handoff support system is built around the following features: 1) It utilises a proxy-based middleware architecture, 2) It uses a BBN based MCDM for handoff decision, 3) It is able to represent the full context information which represents the execution environment, 4) It is able to perform decision making under both certainty and uncertainty, 5) It is able to decide correctly on the target network under dynamic context, 6) It performs decision making in the midst of conflicting, interdependent and constraint criteria, and 7) It uses a profile-based handoff decision to offer personalisation to users. The experimental results showed that when compared with Analytical Hierarchy Process (AHP), the handoff decision method based on BBN performs better on: 1) Modelling of the handoff decision problem and the full representation of the context information, 2) Decision making under uncertainty, 3) Modelling of constraints and interdependent criteria and 4) Support for user preferences. When evaluating the handoff execution, further results revealed that the underlying handoff management strategies provide service continuity by minimising handoff latency and packet losses.
258

Design of an intelligent parking system using Wireless sensors and Multiprotocol Label Switching

Mwebaze, A. 01 June 2010 (has links)
The challenge of parking management has increasingly posed the need for smart solutions. Motorists in today’s busy world seek the best option in locating available parking points. The need for an efficient parking system stems from increased congestion, motor vehicle pollution, driver frustration and fatigue to mention but a few. This study was conducted at a time when the world was experiencing a financial crisis and more than ever motorists needed intelligent parking systems to reduce the cost of gas spent driving around to find parking. Indeed, the time spent driving around would be beneficial if used to do work that would put one at an advantage in the credit recession. The study was also conducted at a time when South Africa was preparing to host the 2010 soccer world cup. In the preparation to manage motor vehicle congestion, this study was a viable solution to manage the expected challenge of parking. This study presents the design and illustrates the performance of an intelligent parking system based on an integrated architecture where (1) Wireless Sensor networks (WSNs) using Small Programmable Object Technology (SPOT) motes are launched into parking places to monitor the activity of the parking area through light intensity sensing and (2) the sensed information is gathered and channeled through a gateway into databases used for parking space visualization and information dissemination over the World Wide Web technology and mobile devices via a Multi Protocol label Switching (MPLS) network. Using an illustrative simulation model of a small parking system built around a new generation of SUNspot motes, the study demonstrates how a real life smart parking system can be deployed to benefit motorists in today’s busy World and serves as a foundation to future work on how this emerging generation of motes can be used to provide better ways of finding parking.
259

Cross-Layer RaCM Design for Vertically Integrated Wireless Networks

Pileggi, Paolo 01 January 2009 (has links)
IEEE 802.16 wireless metropolitan area network (WMAN) technology is an improvement on its wireless local area network (WLAN) counterpart, namely IEEE 802.11, in that it provides longer range and higher bandwidth capabilities. More importantly, it specifies a connection-oriented medium access control layer (MAC) and scheduling services to support quality of service (QoS) in IEEE 802.16 networks. However, in the standard, scheduling and connection admission control (CAC) mechanisms are left unspecified, leaving this for network operators to decide. This allows implementers to create market and performance advantages, making it a rich field of research and performance analysis. Typically, researchers studying scheduling and admission control in such wireless networks consider these resource and connection management (RaCM) algorithms in isolation: They investigate (1) schedulers while fixing the admission control processes or using static connection scenarios and (2) admission controllers while fixing the scheduling processes. We hypothesize that there exists an interdependent relationship between RaCM components which is an essential aspect to cross-layer inter-RaCM algorithm design. In order to prove our hypothesis that you cannot consider the scheduler and the CAC in isolation, where it involves the performance of IEEE 802.16 networks, we require a performance model: Analytic modelling is an ideal solution but the system is far too complex. Experimental test beds are expensive, making hardware experimentation another impractical solution. The only other feasible solution is simulation. General simulation environments, such as NS2 and OMNeT++, offer IEEE 802.16 libraries and some degree of development community support. However, for several reasons, as we shall discuss, we developed our own deep simulator – a discrete-event simulation model of an IEEE vertically integrated wireless Internet scenario. In particular, we concentrate our effort on the fixed IEEE 802.16 WMAN (802.16-2004), simulating admission control and scheduling processes exactly. Both the machine model and workload model play an integral part in obtaining useful performance data: Our machine model includes particular MAC and physical layer (PHY) functions of the standard, such as framing, adaptive modulation and coding, fragmentation, and so on, as well as the admission control and scheduling algorithms. For the workload model, we developed a Markov Modulated Arrival Process (MMAP) by combining existing traffic models of different Internet applications, such as VoIP, P2P, etc. Each application is associated with one of the IEEE 802.16 traffic categories (TCs). The MMAP generates both connection– and packet level data, maintaining traffic volume ratios, as reported by previous studies of Internet application traffic volumes. Performance metrics of delay and jitter are calculated per TC connection. This allows a comparison of the quality of experience (QoE) of an individual user for the duration of a connection. At the connection level, we report the blocking probability. By simulating the RaCM with various admission control and scheduling configurations, we were able to show that there is a significant difference in performance when using different CAC and scheduler combinations. Although hardly surprising, it is still proof that one cannot simply consider either in isolation, as is done in various performance studies reported in the literature. This interdependent relationship should be considered when designing complementary admission control and scheduling algorithms.
260

Routing Protocols for Meshed Communication, Networks Targeting Communication Quality of Service (QoS) in Rural Areas

Chissungo, Edmundo B.F. 01 January 2013 (has links)
Rural areas in Africa often have poor telecommunication infrastructure. Mobile phones, if available, are frequently unaffordable to most users. Wireless mesh networks (WMNs) offer an alternative possibility of low cost voice and data communications. The focus of this research is a laboratory study of WMNs that mimic conditions found in rural areas. This work investigates routing strategies for the Mesh Potato (MP). The MP is an effective alternative communication technology that has minimal configuration requirements, low cost of deployment, low power consumption and resilience that make it an attractive choice for rural areas. The MP runs a new mesh networking algorithm called the better approach to mobile ad hoc networking (B.A.T.M.A.N or Batman). This allows a WMN to be established in which users can use plain old telephones to talk to each other using Voice over IP (VoIP). Batman daemon (Batmand) is the implementation of Batman algorithm used by the MP. Batmand is a minimalistic routing protocol which performs well in laboratory experiments. The question raised is whether adding more service specific routing metrics improve the quality of service (QoS) observed in Batmand network in practice. The research investigates delay, packet loss, throughput and jitter as performance parameters (metrics) that may serve as options to improve the simplistic Batman algorithms route selection process. These metrics are essential for QoS in voice- and data-sensitive networks. Specific focus was given to delay and it is the metric added to Batmand. In addition the research examines how well the different applications such as voice and data are supported on the Batmand network under different routing scenarios. The research approach adopted in this dissertation was experimental and an indoor testbed was created to replicate the basic scenarios encountered in the rural environment. The essential characteristics found in the Mdumbi region of the Eastern Cape, South Africa, were taken as a case study in this dissertation. The testbed was used to compare the original Batman algorithm implemented as Batmand, referred to here as O-Batmand, routing protocol and the resultant Batmand version obtained from the addition of the delay-routing metric called modified Batmand (M-Batmand). The research produced a number of findings. As the number of hops increased the per-formance of the network decreased for both protocols. O-Batmand is well suited for the task of routing packets inside a wireless network. It is designed and works for voice packets and supports data services. This is also true for the M-Batmand implementation. M-Batmand was developed as an improvement to the O-Batmand implementation at the cost of increased complexity, experienced by the protocol through modifications of its route selection process. The modification involved adding network delay values to its route selection process. This addition resulted in a protocol that is delay sensitive; however, the overall performance gains were inexistent. The main conclusions drawn from this study are that O-Batmand cannot be modified to include additional metrics and be expected to improve its performance. Second conclusion is that M-Batmand did not improve the overall performance of the O-Batmand protocol. The addition of the delay metric actually hindered O-Batmand's performance to the extent that no overall performance gains were realised. Sources of performance degradations are: increased overhead, from added delay data, in the network control packets called originator messages (OGMs). M-Batmand performs calculation which O-Batmand did not increasing CPU cycle needs. Lastly upon further internal protocol investigation it is seen that the rate of route delay data updates is slower than the original metric used by the protocol. This creates route fluctuations as route selection process will change when the updated delay values are added and change again when there are not as the network obtains the updated delay data. Both protocols support voice and data, however, the results show that the quality of the network deteriorates in the testbed with increasing hops. This affects voice more so then it does data as routes become more unstable with each increasing hop. Further Batmand is best at supporting voice and data as it outperforms M-Batmand in the laboratory experiments conducted. This dissertation argues that while there may exist one or a combination of metrics amongst the researched list (delay, packet loss, throughput and jitter) that may actually improve the performance of the protocol, it is extremely hard to realize such gains in practice.

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