There are several different types of games that are played in multiplayer mode over networks. The type of network games that, from a network’s perspective, are the most demanding is real-time based multiplayer games. Users of such games both assume and require that game play interaction happens in near real-time and these games often support a large number of simultaneous players. Most networks are specialized to either voice traffic (such as the first and second generation of mobile networks) or data traffic (such as wired data networks). It is not clear that the requirements for such real time games can always be met on either type of network. The core of this thesis investigates the performance requirements real-time multiplayer games place on packet switched data networks and the connection between network impairments and game quality degradation. Traffic generated by network games distinguishes itself from other traffic both regarding its general characteristics and the requirements it places on the network. Understanding these traffic characteristics, requirements, and what consequences failures to support such requirements entail are of great importance when designing new networks in order to guarantee suitable quality of service for such real-time games. / Det finns idag en stor mängd datorspel som spelas i flerspelarläge över nätverk. De spel som från ett hårdvaru- och nätverksperspektiv ställer högst krav är realtidsbaserade flerspelarspel. Slutanvändare av dessa realtidsspel både förutsätter och tar för givet att interaktionen sker i så nära realtid som möjligt samtidigt som dessa spel ofta stödjer ett stort antal samtidiga användare. De flesta nätverk är i första hand anpassade för rösttrafik (som första och andra generationens mobilnät) eller datatrafik (som trådade datanätverk). Det står inte klart huruvida någon av dessa nätverk kan garantera tillräcklig prestanda för att en acceptabel spelkvalité skall uppnås för slutanvändaren. Kärnan i denna rapport utreder vilka krav som dagens mest krävande realtidsbaserade flerspelarspel ställer på nätverken de spelas över samt kopplingen mellan brister i dessa nätverk och den upplevda spelkvalitén för användarna. Trafik genererad av realtidsbaserade flerspelarspel särskiljer sig från annan trafik både när det gäller generell karaktäristik och när det gäller de krav som de ställer på nätverken. Det är viktigt att ha en förståelse kring den trafik som dessa spel skapar, kraven de ställer, samt de konsekvenser ett misslyckande av upprätthållande av sådana krav medför. Denna förståelse är av yttersta vikt när man designar nya nätverk för att kunna erbjuda en passande Quality of Service för denna typ av interaktiva multimediatjänster.

ZigBee is a substandard of IEEE 802.15 family that is specially designed to take care of factors such as power, data rate and area that primarily affect network performance. This has controlling and monitoring capability, which finds potential applications in different sectors. ZigBee allows the concept of hybrid networks and mobility. A comprehensive analysis of ZigBee networks was carried out by constructing and simulating the networks to evaluate the performance in terms of throughput, delay, network load, and packets dropped. This research is aimed at evaluating the effect of network topology on the system performance. A careful review of simulation platforms brought the conclusion of using OPNET Modeler which has the required frame work. Different network topologies of simple and hybrid were built and simulated. Throughout the simulations, the best-case scenarios were drawn to the conclusion by the graphical analysis of parameters of evaluation. Mobile networks were constructed and simulated to investigate the effect of mobility on communication.

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This dissertation examines the factors and combinations of factors that affect the performance of continuum of care homeless service networks, applying the configurational approach of contingency theory to data sets drawn from federal sources. The study accepts the two key assumptions from the theory: (1) that there are multiple paths to high performance and (2) key conditions have a joint influence on network performance. The data analysis in this study has two parts. The first employs OLS regression to examine the causal relationship between independent variables and the performance of permanent supportive housing (PSH) programs. This study also applies fuzzy set qualitative comparative analysis (fsQCA) to identify multiple combinations of factors that influence the performance of PSH programs. The results identify key factors and multiple combinations of factors that lead to high and low network performance. Federal CoC funding emerges as a core condition for high and low performance, but all relevant conditions can be critical factors depending on how they interact with other relevant conditions. This analysis helps expand the utility of existing contingency theory by using it to explain the dynamic interactions between factors in the context of public service networks. Ultimately, this dissertation confirms that fsQCA can be a useful method for evaluating the performance of public service networks and helping them provide more services more effectively.

Cette thèse considère les réseaux de capteurs sans fil (RCSF) de grande dimension (de l'ordre du million de noeuds). Les questions posées sont les suivantes : comment prédire le bon fonctionnement et calculer avant déploiement les performances d'un tel réseau, sachant qu'aucun simulateur ne peut simuler un réseau de plus de 100 000 noeuds ? Comment assurer sa configuration pour garantir performance, passage à l'échelle, robustesse et durabilité ? La solution proposée dans cette thèse s'appuie sur une architecture de RCSF hétérogène à deux niveaux, dont le niveau inférieur est composé de capteurs et le niveau supérieur de collecteurs. La première contribution est un algorithme d'auto-organisation multi-canal qui permet de partitionner le réseau inférieur en plusieurs sous-réseaux disjoints avec un collecteur et un canal de fréquence par sous-réseau tout en respectant le principe de réutilisation de fréquence. La seconde contribution est l'optimisation du déploiement des collecteurs car leur nombre représente celui des sous-réseaux. Les problèmes traités ont été : l'optimisation des emplacements des puits pour un nombre prédéfini de puits et la minimisation du nombre de puits ou du coût pour un nombre prédéfini de sauts dans les sous-réseaux. Une solution intuitive et appropriée pour assurer à la fois performances réseaux et coût, est de partitionner le réseau inférieur en sous-réseaux équilibrés en nombre de sauts. Pour ce faire, la topologie physique des puits est une répartition géographique régulière en grille (carrée, triangulaire, etc.). Des études théoriques et expérimentales par simulation des modèles de topologie montrent, en fonction des besoins applicatifs et physiques, la méthodologie de choix et le calcul des meilleures solutions de déploiement. / This thesis considers the large-scale wireless sensor network (LSWSN) consisting of million nodes. The questions are: how to predict the good working and to compute before deployment the performances of such a network, knowing that no simulator can simulate a network of more than 100000 nodes? How to ensure its configuration to ensure performance, scalability, robustness and longevity? The solution proposed in this thesis is based on a two-tiered heterogeneous architecture of WSN in which the level 1 is composed of sensors and the level 2 of collectors. The first contribution is a multi-channel self-organization algorithm, which allows partitioning the network of level 1 into several disjointed sub-networks with one collector and one frequency channel while respecting the principle of frequency reuse. The second contribution is to optimize the deployment of collectors because their number represents that of sub-networks. The problems addressed were: the optimization of sinks locations for a predetermined number of sinks, and the minimization of financial cost related of the sinks? number, for a predetermined number of hops in the sub-networks. An intuitive and appropriate solution to ensure both network performance and cost is to partition the network of level 1 into balanced sub-networks in number of hops. To do this, the physical topology of sinks is a regular geographical grid (square, triangular, etc.). Theoretical studies and simulation of topology models show, depending on application requirements (node density, charge application, etc.) and physical (radio range, surveillance zone), the methodology of choice and the computation of the best deployment solutions.

The Transmission Control Protocol (TCP) is one of the core protocols of the Internet protocol suite. In the wired network, TCP performs remarkably well due to its scalability and distributed end-to-end congestion control algorithms. However, many studies have shown that the unmodified standard TCP performs poorly in networks with large bandwidth-delay products and/or lossy wireless links. In this thesis, we analyze the problems TCP exhibits in the wireless communication and develop TCP congestion control algorithm for mobile applications. We show that the optimal TCP congestion control and link scheduling scheme amounts to window-control oriented implicit primaldual solvers for underlying network utility maximization. Based on this idea, we used a scalable congestion control algorithm called QUeueIng-Control (QUIC) TCP where it utilizes queueing-delay based MaxWeight-type scheduler for wireless links developed in [34]. Simulation and test results are provided to evaluate the proposed schemes in practical networks. / by Gee Won Han. / Thesis (M.S.C.S.)--Florida Atlantic University, 2013. / Includes bibliography. / Mode of access: World Wide Web. / System requirements: Adobe Reader.

A crescente complexidade das redes de comunicação de dados tem como conseqüência direta tornar cada vez mais complexas as tarefas de projetar seu dimensionamento e evolução. Um passo preliminar vitalmente importante no projeto de uma rede é a coleta de dados relacionados ao uso esperado da rede. Os padrões de tráfego estimados são usados nos cálculos de dimensionamento dos recursos. Fortemente relacionada a estas atividades está a previsão da performance em termos de throughput da rede, tempos de resposta, probabilidade de congestionamento, entre outras. Uma análise de performance efetiva depende de se representar precisamente a configuração da rede e da carga de tráfego a ela submetida. Técnicas de modelagem analítica ou de simulação podem ser usadas para determinar a performance esperada do sistema. Neste trabalho a usada a técnica de simulação para modelar o tráfego da rede usando dados coletados em uma rede real por monitoração. Trabalhando-se com o modelo validado e possível ajustar a carga de tráfego para representar mudanças esperadas nos volumes de tráfego, e testar o efeito na performance de diferentes configurações de rede. Isso possibilita que os processos de planejamento e projeto sejam executados com confiança, alem dos custos da rede poderem ser otimizados. O sistema apresentado neste trabalho e orientado à gerência de performance de redes, apoiando as atividades de gerência e planejamento de capacidade. Defende-se a idéia de que, a partir do perfil dos usuários de uma rede, derivado do tráfego por eles gerado, pode-se construir um modelo de tráfego significativamente representativo para a análise e previsão do desempenho da rede. O modelo foi desenvolvido para redes de comutação de pacotes com serviço orientado a conexão, e validado sobre o tráfego de uma rede X.25 através de um modelo de simulação, implementado em GPSS. O protótipo do sistema é composto por três processos principais que incorporam as etapas da análise de performance: monitoração do tráfego, análise do tráfego e simulação do tráfego. Na monitoração, são contabilizadas uma série de variáveis para cada conexão gerada na rede. Para cada tipo de aplicação são calculados os respectivos fatores de carga de tráfego. As aplicações são classificadas em dois grandes grupos: interativas e não-interativas. O processo de análise do tráfego gera os fatores de carga de tráfego na forma de tabelas e gráficos. As conexões e as métricas de performance produzidas na simulação do tráfego podem ser analisadas e validadas graficamente. O sistema proposto foi especificado em SDL (Specification and Description Language). / The increasing complexity of communication networks turns each time more complex the task to plan its expansion and evolution. A vitally important preliminar step in computer network design is the gathering of data relating to the expected use of the network. The estimated traffic patterns are used in resource usage computations. Closely related to these activities is the estimation of performance in terms of network throughput, response times, congestion probability, among others. An efective performance analysis requires the accurate representation of computer network configuration and traffic load. Analytical or simulation techniques can be used to establish the expected system performance. This work makes use of simulation to model the network traffic, based on collected data of a real network. network. Working with the validated model is possible to adjust the traffic load to represent future demand, and to test the performance impact under distinct network configurations. This enable a trustful execution of network planning and design, besides of the cost optimization. The system presented at this work is network performance management oriented, giving support to capacity management and capacity planning. The central idea is that, through network users profile achieved from generated traffic, it's possible to build a representative traffic model to aim at the network performance analysis and forecast. The model was developed to connection oriented packet switched networks, and validated by means of a simulation model to X.25 network traffic, implementd in GPSS. The system prototype comprises three process: traffic monitoring, traffic analysis and traffic simulation. In monitoring, a set of variables are registered for each network connection generated. The traffic load factors are computed according the application type. The applications are classified in two groups: interactive and non-interactive. The traffic analysis process produces traffic load factors in form of tables and graphics. Connections and performance metrics generated at traffic simulation can be graphically analyzed and validated. The proposed system was specified in SDL (Specification and Description Language).

I avhandlingen beskrivs ett hypotetiskt system som kan användas av mobila användare, bland andra taxichaufförer, som exempelvis vill följa en viktig fotbollsmatch. Flera faktorer ställer till problem: Ibland står bilen still och föraren har inget annat att tänka på än matchen. Ibland kör denne runt med en kund som inte vill bli störd av matchen. Dessutom kan det vara svårt att titta på rörliga bilder och köra bil samtidigt. I och med att bilen körs runt har man också olika bra anslutning till Internet vid olika tillfällen – det kan variera mellan inget alls, en dålig GSM/GPRS förbindelse (8 kbps) och en snabb WLAN anslutning (100 Mbps). I avhandlingen presenteras en tre-lagers modell som kan användas för att beskriva den här typen av applikationers kvalitet. Modellen delas in i tre lager: nätverk, applikation och användare/använding. Det sistnämnda lagret ligger utanför det tekniska systemet och definieras av att det är där de verkliga informationsutbytet sker. På applikationsnivån samlas data in, packas och packas upp i samband med nätverkstransport och visas sedan för användaren. Det är också här som eventuell interaktion sker med användaren. Nätverkslagret är ansvarigt för ändamålsenlig transport av data. De tre lagren är ömsesidigt beroende av varandra. Dålig prestanda på ettlager påverkar de andra lagren och tvärtom. Tre studier har genomförts av hur problem på nätverkslagret i form av begränsad bandbredd och hög fördöjning påverkar användarna. Låg bandbredd ger låg videokvalitet vilket inte uppskattas av användarnamnen genom att skifta till animeringar som fungerar med lägre bandbredd kan man ändå få användarna nöjda. Om användarna måste välja mellandålig videokvalitet och animeringar väljer de som ser sig som fotbollskunniga det förstnämnda och de som ser sig som okunniga men dock fotbollsfans väljer det sistnämnda. Men i en annan studie där användarna spelade bluffstopp mot varandra över ett datanätverk fick vi ett annat resultat. Där var det negativt med högre videokvalitet (bilder per sekund). En förklaring kan vara att användarna distraherades mer av högre bildfrekvens. I den tredje studien studerades vad som händer i Pong om man läggerin fördröjningar i spelet. Sedan tidigare visste man att det blir svårare attspela med fördröjningar – särskilt om man inte märker dem. Vi ställde ossfrågan om man kan kompensera för dem genom att informera användarna om dem. Det visade sig att användare som får information med i vårtfall en prediktiv visning lättare anpassar sin mentala insats till uppgiftens svårighetsgrad. Det är alltså inte bara möjligt utan ibland också önskvärt att utnyttja en lägre bandbredd från användarens perspektiv. Med det sagt finns det ändå i långt fler situationer där det är bättre med bättre nätverksprestanda. Pongspelet var roligare med lägre delay. Videon uppfattades som bättre medhögre bandbredd i den förstnämnda studien. Multicast, där ett paket skickas till flera användare i stället för att de skafå varsin, identiska paket, är ett viktigt verktyg för att få bättre prestanda i videoapplikationer. Tyvärr är det inbyggda stödet för multicast i den viktiga IEEE 802.11 standardfamiljen för trådlösa nätverk mycket outvecklat. Ettstort problem är att det inte går att veta om ett paket har kommit fram eller om det har försvunnit i en, mycket trolig, krock. Vi har vidareutvecklat och anpassat en föga känd krockdetektionsmekanism från 80-talet för använding i IEEE 802.11 nätverk. Den anpassade algoritmen kallar vi EMCD vilket är en förkortning för ‘‘Early Multicast Collision Detection’’ eller tidig krockupptäckt för multicast. Vi har presenterat en nysannolikhetsbaserad modell för att beräkna algoritmens prestanda undermaximal belastning. Modellen som har verifierats genom simuleringar kanäven användas för att beräkna optimala parametrar för algoritmen. Algoritmen har visats kraftigt reducera risken för oupptäckta kollisioner och reducerar den tid som går åt för dem. EMCD-algoritmen inspirerade till att utveckla en ytterligare algoritm som inte bara kan upptäcka utan också undvika kollisioner: PREMA som står för ‘‘Prioritized Repeated Eliminations Multiple Access’’ eller prioriterad kanal-åtkomst med upprepade eliminationer. Det finns två viktiga skillnader mellanhur de fungerar. I EMCD bygger kollisionsdetektionen på rektangelfördelade slumptal och en enda upptäcktsomgång. I PREMA används i stället geometriskt fördelade slumptal och upprepade omgångar. Effekten blir att man med stor säkerhet får en enda vinnare. även för PREMA presenteras en sannolikhetskalkylsbaserad prestandaanalys för maxlastfallet vilken stöds av simuleringar. Samma formler kan användas för att approximativt skatta prestanda i EY-NPMA som är en närliggande algoritm. Den var tänkt att använda i Hiperlan/1; en standard som aldrig fick något kommersiellt genombrott. Använder man den modell som vi presenterar i avhandlingens sista studiekan man med ganska god noggrannhet beräkna optimala parametrar för EY-NPMA med en beräkningsinsats O(mY S) mot O(mES×mY S) för tidigare kända algoritmer. / Imagine a taxi driver wanting to watch a football game while working. Events in the game cannot be predetermined, the driver's available attentional resources vary and network connections change from non-existing to excellent, so it will be necessary to develop a viewing application that can adapt to circumstances. This thesis presents a system model and sketches a framework for design and run time adaptations. The model has three layers: user/usage, application and network. Quality of service metrics are proposed for each layer. A particular emphasis is placed on the difference between the user/usage layer and the application layer. Satisfaction at the former means a job well done, a match played to your liking etc. Satisfaction at the latter means good picture quality, nice colours etc. The thesis continues by identifying and describing elements required to build the system used by the taxi driver. Three studies are presented where either bandwidth or delay are varied at the network level. Video is better the higher the bandwidth; animations can be used as a complement. They are shown to be better than low quality video but worse than high quality video for watching a football game. Better video in the form of higher frame rates turned out to be worse for playing a card game over the Internet. A possible explanation is the distraction experienced when the image is updated constantly. Another result of our studies is that users can adapt their mental effort to the actual load when given feedback on the network delay affecting a computer game. The results mentioned above show that it is possible to compensate for poor network performance. For the user, improved network performance is generally more satisfactory. Early multicast collision detection is a method for improved multicast performance in high load IEEE 802.11 networks. Prioritised repeated eliminations multiple access is a method for multicast and other traffic which can be used alone or in an IEEE 802.11 network. Probabilistic performance analysis and simulations show that both protocols drastically reduce the time spent in collisions and improve throughput compared to IEEE 802.11. Some of the formulae are applied to EY-NPMA as well; they are used to estimate performance and to estimate optimal operating parameters more efficiently than with previously known methods.

Home networks are evolving vigorously and are also becoming more and more heterogeneous and complex. Home networks contain new services and numerous devices with wired and wireless links. At the same time, users demand high levels of quality of service for many new applications. Hence, the supervision of links quality tends to be mandatory in emergent home networks, to trigger QoS mechanisms. In this context, this dissertation proposes the utilization of the available bandwidth as a performance indicator in hybrid home networks (e.g. for remote service-evaluation, diagnosis and fault detection) and as link-state metric for a number of QoS mechanisms (e.g., admission control, path selection and load balancing). In this dissertation, we firstly explain why available bandwidth probing is a fundamental tool in the new QoS architectures for hybrid home networks and we explore different use cases. We investigate the networking constraints that affect bandwidth probing in hybrid home networks. We explain why most tools to measure available bandwidth on Internet paths are not very efficient on home networks. We make a taxonomic study of a number of state-of-the-art probing techniques and probing tools for available bandwidth. At that aim, we propose a functional framework, called Metrics Profile Capture Filter and Feedback (MPCFF). Based on these studies, we choose Iperf in TCP mode as an attractive tool to estimate available bandwidth. Then, we conduct a performance evaluation on an experimental test bed, to compare Iperf in lightweight TCP-mode vs. various state-of-the-art tools (Wbest, Pathchirp, Pathload and IGI/PTR). We show that Iperf in lightweight TCP mode is superior in terms of accuracy and speed of convergence. Finally, we integrate Iperf in lightweight TCP mode into a path selection protocol using the Inter-MAC software (developed in the Omega European project). We show, on a test bed, how Iperf in lightweight TCP mode enhances the Inter-MAC path selection by eliminating performance deterioration due to time-varying capacity links. Our results show that Iperf in lightweight TCP mode, accurately, triggers path selection and load balancing mechanisms, to adapt the network resources to the strong degradation of WiFi and PLC links. Available bandwidth probing detects and helps to control real-time deviations of the quality of experience, associated of sensitive applications. At the same time, available-bandwidth probing helps the service provider to isolate failures and to monitor the end-to-end residential service, on demand or on long-term periodicity basis.

In recent years, global mobile data traffic has been increasing exponentially as mobile devices pervade our daily lives. To cope with the ever growing demands for higher data rates and seamless connectivity, one solution is to drastically increase the number of macro base stations in the conventional cellular architecture. However, this results in high deployment costs. Deploying low-power nodes such as relays that do not require a wired backhaul connection within a macrocell is one of cost-effective ways to extend high data rate coverage range. Relays are typically deployed to increase signal strength in poor coverage areas or to eliminate dead spots. But more importantly, relays provide a natural diversity, called cooperative diversity. In addition to a direct signal from a base station, extra copies of the same signal are forwarded from relays. Utilizing this diversity at the destination can yield significant performance enhancements. Thus, cooperative relay strategies need to be considered to enable high data rate coverage in a cost-effective manner. In this dissertation, we consider a simple single-relay network and present low-complexity and power-efficient cooperative relay designs that can achieve low error rate. We first study decode-and-forward (DF) relay networks with a single antenna at each node, where the relay decodes the received signal and forwards the re-encoded information to the destination. In DF relay scheme, decoding at the relay is not perfect and the error-propagation phenomenon is a detrimental problem, preventing the destination from collecting the cooperative diversity. To enable cooperative diversity in DF relay networks, we adopt link-adaptive power-scaling relay strategies where the relay scales the transmission power of the re-encoded signal based on the reliability of the source-relay link. We generalize power-profile designs and analyze the diversity order enabled by the general power-profile designs. We provide necessary and sufficient conditions for the designs to enable full cooperative diversity at the destination. In the second part of this dissertation, we extend the power-scaling relay strategy to DF multi-input multi-output (MIMO) relay networks, where multiple antennas are adopted at each node, and show that full cooperative diversity can also be achieved here. To collect spatial diversity provided by multiple antennas without using maximum-likelihood equalizers (MLEs) or near-ML detectors which exhibit high complexity, channel-controlled automatic repeat request (CC-ARQ) scheme is developed for DF MIMO relay networks to enable spatial diversity with linear equalizers (LEs) maintaining low-complexity. We also show that joint cooperative and spatial diversity can be achieved at the destination when the power-scaling strategy and the CC-ARQ with LEs are combined. Finally, amplify-and-forward (AF) MIMO relay designs, where the relay simply amplifies the received signal and forwards it to the destination, are studied with consideration of peak-power constraints at the relay. One practical concern for AF relaying is that the output signal at the relay may suffer from large peak-to-average power ratio (PAR), which may cause nonlinear distortion and/or saturation in the transmitted signal due to the limited linear range of power amplifiers. Thus, we first investigate peak-power constrained power-scaling strategies and find a sufficient condition to enable joint cooperative and spatial diversity at the destination. Based on this study, we propose simple and practical AF MIMO relay designs with peak-power constraint at the relay. CC-ARQ is also applied to AF MIMO relay networks to reduce the decoding complexity.