Information-Centric Networking (ICN) is a new research area concerning creating a new network architecture that would be more suitable for both current and the future's network. The MOSES (Mobile Opportunistic Services for Experience Sharing) project is part of this development. The project works with the development and demonstration of the Network of Information (NetInf) protocol, which is an implementation of the ICN concept. This Master’s thesis project is part of the MOSES project and aims to assist the MOSES project with the demonstration of a mobile opportunistic sharing concept based on the NetInf protocol. Demonstrating the MOSES concept in practice requires deep understanding of networking, localization, transport, and dissemination of digital content in an ad hoc network. This implementation requires an analysis of the previous work, development of new functionalities, and finally an analysis of a series of controlled experiments. This Master’s thesis project has designed, implemented, and evaluated an Android application within the MOSES framework by using the previously developed NetInf Android library. This prototype is used to demonstrate how mobile Android users can opportunistically share and disseminate content based on their location using the MOSES/ICN concept. The functionality and efficiency of the prototype Android application built during this thesis project has been analyzed and evaluated by conducting a series of controlled experiments under the supervision of MOSES researchers. The results of these controlled experiments has provided insight for MOSES researchers as well as explored the concept of using ICN (NetInf) for opportunistic content distribution. The experiment results aim at assisting MOSES researchers to extend and further develop the prototype application and the involved algorithms to create a fully functional mobile application for experience sharing services tailored to large-scale events. / Information-Centric Networking (ICN) är ett nytt forskningsområde för att bygga en ny nätverksarkitektur mer passande för dagens och framtida nätverk. MOSES projektet är en del av denna utveckling och arbetar med utveckling och demonstration av Network of Information (NetInf) protokollet, som är en implementering av ICN konceptet. Detta examensarbete är en del av MOSES (Mobile Opportunistic Services for Experience Sharing) projektet som syftar till att bistå MOSES projektet med demonstrationen av "mobile opportunistic sharing" konceptet som bygger på NetInf protokollet. Att demonstrera MOSES konceptet i praktiken krävs djupt förståelse om nätverk, lokalisering, transport och spridning av digitalt data i en "ad hoc" och infrastruktur miljö. Genomförandet av denna implementering kräver en analys av tidigare arbete, utveckling av nya funktioner och slutligen analys av genomförda experiment och resultaten. Detta examensarbete har utformat, genomfört och utvärderat en Android applikation inom ramen för MOSES med hjälp av tidigare utvecklat NetInf Android bibliotek. Denna prototyp används för att visa hur mobila Android användare opportunistiskt kan dela och sprida innehåll baserat på deras plats med hjälp av MOSES/ICN konceptet. Funktionaliteten och effektiviteten av prototypen byggd under detta examensarbete har analyserats och utvärderats genom att utföra en serie kontrollerade experiment under ledning av MOSES forskare. Resultaten av dessa kontrollerade experiment har gett insikt åt MOSES forskare samt utforskat konceptet att använda ICN (NetInf) för opportunistisk distribution av innehåll. Experimentens resultat syftar till att hjälpa MOSES forskare att utöka och vidareutveckla prototypen och de involverade algoritmer för att skapa en fullt fungerande mobil applikation för "experience sharing services" anpassad för stora evenemang.

Gram-negative infection has been linked to hospital water although few studies have examined whether water systems are reservoirs of nosocomial pathogens. This study investigated longitudinal recovery of the opportunistic pathogens Pseudomonas aeruginosa, Stenotrophomonas maltophilia and Acinetobacter baumannii from water outlets of a haematology unit and evaluated Point-Of-Use Filtration (POU-F) as a control measure. In a two-year double cross-over trial, water samples and swabs were taken weekly from 39 showers/taps on the unit. Four study phases alternated between non-filtered (Phases 1 & 3), and filtered outlets (Phases 2 & 4) using Pall AquasafeTM 14-day filters. In Phases 1 & 3; 99% of 1396 samples yielded bacterial growth, with colonies generally too numerous to count. Target species were isolated from 22% of water samples (P. aeruginosa 14%; S. maltophilia 10%) and 10% of swabs. P. aeruginosa was particularly associated with handwash stations and S. maltophilia with showers. A. baumannii was not isolated. With POU-F; 22% of 1242 samples yielded bacterial growth (mean CFU/100ml ,4.6). S. maltophilia was isolated only once from water but never from outlet swabs. PCR typing identified clusters of isolates colonizing different outlets over time but no clear association between water and patient isolates was identified. The incidence of Gram negative infections remained low throughout the study. Without POU-F, water from taps/showers represented a source of bacteria including the target species. POU-F substantially reduced the frequency and number of target species from every outlet, and merits further investigation as an intervention to protect immunocompromised patients from opportunistic pathogens. / School of Life Sciences, University of Bradford and Pall Medical (Pall Europe Ltd)

Radio spectrum has become increasingly scarce due to the proliferation of new wireless communication services. This problem has been exacerbated by fixed bandwidth licensing policies that often lead to spectral underutilization. Cognitive radio networks (CRN) can address this issue using flexible spectrum management that permits unlicensed (secondary) users to access the licensed spectrum. Supporting real-time quality-of-service (QoS) in CRNs however, is very challenging, due to the random spectrum availability induced by the licensed (primary) user activity. This thesis considers the problem of real-time voice transmission in CRNs with an emphasis on secondary network ``friendliness''. Friendliness is measured by the secondary real-time voice capacity, defined as the number of connections that can be supported, subject to typical QoS constraints. The constant bit rate (CBR) air interface case is first assumed. An offline scheduler that maximizes friendliness is derived using an integer linear program (ILP) that can be solved using a minimum cost flow graph construction. Two online primary scheduling algorithms are then introduced. The first algorithm is based on shaping the primary spectral hole patterns subject to primary QoS constraints. The second applies real-time scheduling to both primary traffic and virtual secondary calls. The online scheduling algorithms are found to perform well compared to the friendliness upper bound. Extensive simulations of the primary friendly schedulers show the achievable secondary voice capacity for a variety of parameters compared to non-friendly primary scheduling. The thesis then considers the variable bit rate (VBR) air interface option for primary transmissions. Offline and online approaches are taken to generate a primary VBR traffic schedule that is friendly to secondary voice calls. The online VBR schedulers are found to perform well compared to the friendliness upper bound. Simulation results are presented that show the effect of the primary traffic load and primary network delay tolerance on the primary network friendliness level towards potential secondary voice traffic. Finally, secondary user friendliness is considered from an infrastructure deployment point of view. A cooperative framework is proposed, which allows the primary traffic to be relayed by helper nodes using decode-and-forward (DF) relaying. This approach decreases the primary traffic channel utilization, which, in turn, increases the capacity available to potential secondary users. A relay selection optimization problem is first formulated that minimizes the primary channel utilization. A greedy algorithm that assigns relay nodes to primary data flows is introduced and found to perform well compared to the optimum bound. Results are presented that show the primary network friendliness for different levels of primary channel utilization. / Dissertation / Doctor of Philosophy (PhD)

De senaste åren har den digitala utvecklingen lett till stor utveckling inom konsumenters köpbeteenden online. I takt med att det uppkommit fler aktörer på marknaden har e-handelsföretag konkurrerat inom pris, fraktalternativ och andra kostnader för att underlätta köpupplevelsen för kunder. Det har lett till att kundens köpbeteende förändras och produkt returerna ökat. Studien undersöker konsumenters returbeteende inom e-handel kopplat till konsumentens personlighet för att hitta samband i beteenden som kan bidra till kunskap kring vilka personlighetsdimensioner som är mer benägna att returnera varor. För att undersöka om det finns ett samband mellan konsumentens personlighetsdimensioner och returbeteende testar studien hypoteser utformade efter femfaktorsteorins dimensioner och de legitima- samt opportunistiska returbeteendet. Studien kommer att bidra med vidare forskning inom returbeteende genom en enkätundersökning av svenska konsumenter. Slutsatsen som kan dras i studien är att vissa personlighetsdimensioner kan kopplas till opportunistiskt och legitimt returbeteende. Denna studie har kunnat visa att neuroticism, välvillighet och samvetsgrannhet är viktiga faktorer som påverkar en individs returbeteende. Den har även visat att det finns ett stort behov av framtida forskning inom området, eftersom det finns indikationer till fler samband. / This essay is in Swedish. In recent years, digital developments have led to major developments in consumers' purchasing behavior online. As more players emerged in the market, e-commerce companies have competed on price, shipping options and other costs to facilitate the shopping experience for customers. This has led to a change in the customer's buying behavior and an increase in product returns. The study examines the return behavior of artifacts in e-commerce linked to the consumer's personality in order to find connections in behaviors that can contribute to knowledge about which personality dimensions are more likely to return goods. To investigate whether there is a relationship between the consumer's personality dimensions and return behavior, the study tests hypotheses designed according to the dimensions of the five-factor theory and the legitimate and opportunistic return behavior. The study will contribute to further research in return behavior through a survey of Swedish consumers. The conclusion that can be drawn in the study is that certain personality dimensions can be linked to opportunistic and legitimate return behavior. This study has been able to show that neuroticism, agreeableness and conscientiousness are important factors that influence an individual's return behavior. It has also shown that there is a great need for future research in the area, as there are indications of more connections.

No description available.

[pt] Reclamações de consumidores podem ser feitas por diversos motivos, em sua maioria, a partir de episódios negativos de consumo. No entanto, há um grupo de indivíduos que realizam reclamações a empresas sem estarem necessariamente insatisfeitos. A essa conduta dá-se o nome de reclamação fraudulenta, que ocorre quando a finalidade do consumidor em realizar a reclamação visa algum lucro monetário ou social à custa da empresa. Apesar da relevância do tema, há poucos estudos a seu respeito na área de marketing, principalmente no Brasil. Ainda que existam autores que investiguem o assunto, é difícil afirmar o que motiva indivíduos a seguirem essa linha de comportamento. À frente desse quadro, o presente estudo visou analisar a relação entre as reclamações fraudulentas e a cultura brasileira, a partir das motivações que levam à adesão desse tipo de comportamento. Para isso, foi realizada uma pesquisa qualitativa, utilizando-se para a coleta de dados entrevistas em profundidade com 27 consumidores, guiadas pelo uso da técnica projetiva. A análise dos dados indica diferentes reações dos entrevistados a reclamações fraudulentas, divergindo entre a aceitação e a rejeição dos comportamentos oportunistas. Foi possível perceber que existe uma relação estreita entre cultura brasileira e reclamações fraudulentas, que giram em torno da ideia do jeitinho brasileiro, da malandragem, da esperteza, e da má fé, além da ligação entre religião e comportamentos considerados como errados. / [en] Consumer complaints can be made for many reasons, mostly from negative episodes of consumption. However, there is a group of individuals who make complaints to companies without necessarily being unsatisfied. This conduct is called a fraudulent claim, which occurs when the purpose of the consumer in making the claim is for some monetary or social profit at the expense of the company. Despite the relevance of the theme, there are few studies about it in the area of marketing, mainly in Brazil. Although there are authors who investigate the subject, it is difficult to affirm what motivates individuals to follow this line of behavior. Ahead of this framework, the present study aimed to analyze the relationship between fraudulent claims and Brazilian culture, based on the motivations that lead to support this type of behavior. For this, a qualitative research was carried out, using data interviews in depth with 27 consumers, guided using the projective technique. The analysis of the data indicates different reactions of respondents to fraudulent complaints, diverging between acceptance and rejection of opportunistic behavior. It was possible to perceive that there is a close relationship between Brazilian culture and fraudulent claims, which revolve around the idea of Brazilian way, trickery, cleverness, and bad faith, as well as the link between religion and behaviors considered as wrong.

As wireless technologies evolve, novel innovations and concepts are required to dynamically and automatically alter various radio parameters in accordance with the radio environment. These innovations open the door for cognitive radio (CR), a new concept in telecommunications. CR makes its decisions using an inference engine, which can learn and adapt to changes in radio conditions. Fuzzy logic (FL) is the proposed decision-making algorithm for controlling the CR's inference engine. Fuzzy logic is well-suited for vague environments in which incomplete and heterogeneous information is present. In our proposed approach, FL is used to alter various radio parameters according to experience gained from different environmental conditions. FL requires a set of decision-making rules, which can vary according to radio conditions, but anomalies rise among these rules, causing degradation in the CR's performance. In such cases, the CR requires a method for eliminating such anomalies. In our model, we used a method based on the Dempster-Shafer (DS) theory of belief to accomplish this task. Through extensive simulation results and vast case studies, the use of the DS theory indeed improved the CR's decision-making capability. Using FL and the DS theory of belief is considered a vital module in the automation of various radio parameters for coping with the dynamic wireless environment. To demonstrate the FL inference engine, we propose a CR version of WiMAX, which we call CogMAX, to control different radio resources. Some of the physical parameters that can be altered for better results and performance are the physical layer parameters such as channel estimation technique, the number of subcarriers used for channel estimation, the modulation technique, and the code rate. / Ph. D.

Auf dem Gebiet der drahtlosen Kommunikation und insbesondere auf den tieferen Netzwerkschichten sind gewaltige Fortschritte zu verzeichnen. Innovative Konzepte und Technologien auf der physikalischen Schicht (PHY) gehen dabei zeitnah in zelluläre Netze ein. Drahtlose Maschennetzwerke (WMNs) können mit diesem Innovationstempo nicht mithalten. Die Mehrnutzer-Kommunikation ist ein Grundpfeiler vieler angewandter PHY Technologien, die sich in WMNs nur ungenügend auf die etablierte Schichtenarchitektur abbilden lässt. Insbesondere ist das Problem des Scheduling in WMNs inhärent komplex. Erstaunlicherweise ist der Mehrfachzugriff mit Trägerprüfung (CSMA) in WMNs asymptotisch optimal obwohl das Verfahren eine geringe Durchführungskomplexität aufweist. Daher stellt sich die Frage, in welcher Weise das dem CSMA zugrunde liegende Konzept des konkurrierenden Wettbewerbs (engl. Contention) für die Integration innovativer PHY Technologien verwendet werden kann. Opportunistische Kommunikation ist eine Technik, die die inhärenten Besonderheiten des drahtlosen Kanals ausnutzt. In der vorliegenden Dissertation werden CSMA-basierte Protokolle für die opportunistische Kommunikation in WMNs entwickelt und evaluiert. Es werden dabei opportunistisches Routing (OR) im zustandslosen Kanal und opportunistisches Scheduling (OS) im zustandsbehafteten Kanal betrachtet. Ziel ist es, den Durchsatz von elastischen Paketflüssen gerecht zu maximieren. Es werden Modelle für Überlastkontrolle, Routing und konkurrenzbasierte opportunistische Kommunikation vorgestellt. Am Beispiel von IEEE 802.11 wird illustriert, wie der schichtübergreifende Entwurf in einem Netzwerksimulator prototypisch implementiert werden kann. Auf Grundlage der Evaluationsresultate kann der Schluss gezogen werden, dass die opportunistische Kommunikation konkurrenzbasiert realisierbar ist. Darüber hinaus steigern die vorgestellten Protokolle den Durchsatz im Vergleich zu etablierten Lösungen wie etwa DCF, DSR, ExOR, RBAR und ETT. / In the field of wireless communication, a tremendous progress can be observed especially at the lower layers. Innovative physical layer (PHY) concepts and technologies can be rapidly assimilated in cellular networks. Wireless mesh networks (WMNs), on the other hand, cannot keep up with the speed of innovation at the PHY due to their flat and decentralized architecture. Many innovative PHY technologies rely on multi-user communication, so that the established abstraction of the network stack does not work well for WMNs. The scheduling problem in WMNs is inherent complex. Surprisingly, carrier sense multiple access (CSMA) in WMNs is asymptotically utility-optimal even though it has a low computational complexity and does not involve message exchange. Hence, the question arises whether CSMA and the underlying concept of contention allows for the assimilation of advanced PHY technologies into WMNs. In this thesis, we design and evaluate contention protocols based on CSMA for opportunistic communication in WMNs. Opportunistic communication is a technique that relies on multi-user diversity in order to exploit the inherent characteristics of the wireless channel. In particular, we consider opportunistic routing (OR) and opportunistic scheduling (OS) in memoryless and slow fading channels, respectively. We present models for congestion control, routing and contention-based opportunistic communication in WMNs in order to maximize both throughput and fairness of elastic unicast traffic flows. At the instance of IEEE 802.11, we illustrate how the cross-layer algorithms can be implemented within a network simulator prototype. Our evaluation results lead to the conclusion that contention-based opportunistic communication is feasible. Furthermore, the proposed protocols increase both throughput and fairness in comparison to state-of-the-art approaches like DCF, DSR, ExOR, RBAR and ETT.

IEEE 802.11 wireless LANs operating in the infrastructure mode are extremely popular and have seen widespread deployment because of their convenience and cost efficiency. A large number of research studies have investigated the performance of DCF, the default MAC protocol in 802.11 WLANs. Previous studies have pointed out several performance problems caused by the interaction of DCF in infrastructure-based WLANs. This thesis addresses a few of these issues. In the first part of the thesis, we address the issue of head-of-line (HOL) blocking at the Access Point (AP) in infrastructure WLANs. We use a cooperative ARQ scheme to resolve the obstruction at the AP queue. We analytically study the performance of our scheme in a single cell IEEE 802.11 infrastructure WLAN under a TCP controlled file download scenario and validate our analysis by extensive simulations. Both analysis and simulation results show considerable increase in system throughput with the cooperative ARQ scheme. We further examine the delay performance of the ARQ scheme in the presence of both elastic TCP traffic and delay sensitive VoIP traffic. Simulations results show that our scheme decreases the delay in the downlink for VoIP packets significantly while simultaneously providing considerable gains in the TCP download throughput. Next, we propose a joint uplink/downlink opportunistic scheduling scheme for maximising system throughput in infrastructure WLANs. We first solve the uplink/downlink unfairness that exists in infrastructure WLANs by maintaining a separate queue and a backoff timer at the AP for each mobile station (STA). We also increase the system throughput by making the backoff timer a function of the channel gains. We analyse the I performance of our scheme under symmetric UDP traffic with i. i. d. channel conditions. Finally, we discuss several opportunistic scheduling policies which aim to increase the system throughput while satisfying certain Quality of Service (QoS) objectives. The standard IEEE 802.11 DCF protocol only offers best-effort services and does not provide any QoS guarantees. Providing QoS in 802.11 networks with time varying channel conditions has proven to be a challenge. We show by simulations that by an appropriate choice of the scheduling metric in our opportunistic scheduling scheme, different QOS objectives like maximizing weighted system sum throughput, minimum rate guarantees and throughput optimality can be attained.

[ES] La disponibilidad y el rendimiento de las actuales tecnologías inalámbricas como WiFi o 4G, pueden tener serios problemas de congestión y propagación, especialmente en espacios muy concurridos, o bien ser inaccesibles en sitios remotos o con baja densidad de personas. La utilización de las Redes Oportunistas en este tipo de escenarios puede ser la solución a estos problemas. Estas redes se basan en la oportunidad de intercambiar mensajes utilizando algún tipo de tecnología de comunicación directa entre dispositivos móviles como son Bluetooth o WiFi. El rendimiento de las Redes Oportunistas depende principalmente de la movilidad de los nodos y los protocolos de enrutamiento utilizados, siendo estos últimos los encargados de decidir como son intercambiados los mensajes cuando un contacto ocurre, intentando encontrar la mejor ruta para que un mensaje alcance su destino. Por otra parte, la eficiencia de la difusión en estas redes está ligada especialmente a la movilidad de los usuarios y al comportamiento humano. Entonces, para el análisis y la evaluación del rendimiento de las Redes Oportunistas es necesario considerar tanto los aspectos técnicos relacionados con los protocolos de encaminamiento, como los aspectos de la movilidad humana. Esta tesis doctoral se centra principalmente en evaluar la diseminación de la información usando redes oportunistas en escenarios urbanos, en los que existen diferentes densidades y tasas de renovación de personas, es decir, con usuarios que puedan entrar y salir del escenario evaluado. Dado que la existencia de este tipo de trazas reales es muy limitada, en esta tesis se plantea la generación de este tipo de trazas de forma sintética. Para ello, mediante el uso de un simulador de movilidad peatonal, se han generado trazas realistas de movilidad con diferentes grados de densidad y tasas de renovación de usuarios con el objeto de evaluar diferentes aspectos de la difusión de mensajes en las Redes Oportunistas. El análisis de las características temporales y espaciales de estas trazas generadas refleja el realismo de los escenarios que se han considerado. Además, los experimentos relativos a la difusión de mensajes realizados con estas trazas, confirman que la tasa de renovación tiene un gran impacto en el rendimiento de los protocolos, lo que es particularmente evidente cuando el tamaño de los mensajes es mayor. Por otra parte, también se ha realizado el estudio, utilizando en este caso trazas reales, de la difusión de información a través de las Redes Oportunistas Vehiculares. Ya que de la misma manera la movilidad de estos vehículos está ligada al comportamiento humano, nos hemos centrado en la diseminación de la información en determinadas horas del día dependiendo del número de vehículos en circulación, debido a que este aspecto tiene un gran impacto en el reenvío de datos. Los resultados de estos experimentos confirman que los dos principales factores que afectan a la difusión de información son el grado de movilidad y el tamaño de mensaje. Aunque es bien sabido que al aumentar la densidad de nodos aumenta la velocidad de difusión, mostramos que, al mantener la densidad de nodos fija, las tasas de renovación más altas hacen que la relación de entrega disminuya. Además, descubrimos que la relación entre el tamaño del mensaje y la duración del contacto también es un factor clave, lo que demuestra que la transmisión de los mensajes grandes puede llevar a un rendimiento general muy bajo. Basándonos en todo lo expuesto anteriormente, se ha propuesto una mejora al protocolo Epidemic, a la que hemos denominado EpidemicX2, que se basa en la fragmentación de los datos a ser enviados con el fin de aprovechar la corta duración de los contactos para aumentar así la posibilidad de su entrega. Este protocolo es particularmente efectivo para la difusión de los mensajes grandes. Los resultados muestran que la tasa de entrega se increment / [CA] La disponibilitat i el rendiment de les actuals tecnologies sense fil com WiFi o 4G, poden tindre seriosos problemes de congestió i propagació, especialment en espais molt concorreguts, o bé ser inaccessibles en llocs remots o amb baixa densitat de persones. La utilització de les Xarxes Oportunistes en este tipus d'escenaris pot ser la solució a estos problemes. Estes xarxes es basen en l'oportunitat d'intercanviar missatges utilitzant algun tipus de tecnologia de comunicació directa entre dispositius mòbils com són Bluetooth o WiFi. El rendiment de les Xarxes Oportunistes depén principalment de la mobilitat dels nodes i els protocols d'enrutamiento utilitzats, sent estos últims els encarregats de decidir com són intercanviats els missatges quan un contacte ocorre, intentant trobar la millor ruta perquè un missatge abast el seu destí. D'altra banda, l'eficiència de la difusió en estes xarxes està lligada especialment a la mobilitat dels usuaris i al comportament humà. Llavors, per a l'anàlisi i l'avaluació del rendiment de les Xarxes Oportunistes és necessari considerar tant els aspectes tècnics relacionats amb els protocols d'acarrerament, com els aspectes de la mobilitat humana. Esta tesi doctoral se centra principalment a avaluar la disseminació de la informació usant xarxes oportunistes en escenaris urbans, en els que hi ha diferents densitats i taxes de renovació de persones, és a dir, amb usuaris que puguen entrar i eixir de l'escenari avaluat. Atés que l'existència d'este tipus de traces reals és molt limitada, en esta tesi es planteja la generació d'este tipus de traces de forma sintètica. Per a això, per mitjà de l'ús d'un simulador de mobilitat de vianants, s'han generat traces realistes de mobilitat amb diferents graus de densitat i taxes de renovació d'usuaris amb l'objecte d'avaluar diferents aspectes de la difusió de missatges en les Xarxes Oportunistes. L'anàlisi de les característiques temporals i espacials d'estes traces generades reflectix el realisme dels escenaris que s'han considerat. A més, els experiments relatius a la difusió de missatges realitzats amb estes traces, confirmen que la taxa de renovació té un gran impacte en el rendiment dels protocols, la qual cosa és particularment evident quan la grandària dels missatges és major. D'altra banda, també s'ha realitzat l'estudi, utilitzant en este cas traces reals, de la difusió d'informació a través de les Xarxes Oportunistes Vehiculares. Ja que de la mateixa manera la mobilitat d'estos vehicles està lligada al comportament humà, ens hem centrat en la disseminació de la informació en determinades hores del dia depenent del nombre de vehicles en circulació, pel fet que este aspecte té un gran impacte en el reexpedició de dades. Els resultats d'estos experiments confirmen que els dos principals factors que afecten la difusió d'informació són el grau de mobilitat i la grandària de missatge. Encara que és ben sabut que a l'augmentar la densitat de nodes augmenta la velocitat de difusió, mostrem que, al mantindre la densitat de nodes fixa, les taxes de renovació més altes fan que la relació d'entrega disminuïsca. A més, descobrim que la relació entre la grandària del missatge i la duració del contacte també és un factor clau, la qual cosa demostra que la transmissió dels missatges grans pot portar a un rendiment general molt davall. Basant-nos en tot el que exposa anteriorment, s'ha proposat una millora al protocol Epidemic, a la que hem denominat EpidemicX2, que es basa en la fragmentació de les dades a ser enviats a fi d'aprofitar la curta duració dels contactes per a augmentar així la possibilitat del seu entrega. Este protocol és particularment efectiu per a la difusió dels missatges grans. Els resultats mostren que la taxa d'entrega s'incrementa, el temps mitjana en l'entrega es reduïx, sense un substancial increment en termes de sobrecàrrega. / [EN] The availability and performance of current wireless technologies such as WiFi or 4G, can have severe problems of congestion and information diffusion, especially in crowded spaces, or, on the other side, be inaccessible in places with a low density of people. The use of Opportunistic Networks in these types of scenarios can be a solution to these problems. These networks are based on the opportunity to exchange messages using some type of direct communication technology between nearby mobile devices such as Bluetooth or WiFi. The performance of these networks depends mainly on the mobility of the nodes and the routing protocols used. The goal of these protocols is to decide how messages are exchanged when a pair of nodes are in contact, trying to find the best route for a message to reach its destination. The efficiency of the diffusion in these networks is related mainly to the mobility of users and human behaviour. Therefore, for the analysis and evaluation of the performance of the Opportunistic Networks, it is necessary to consider both the technical aspects related to the routing protocols, as well as the aspects of human mobility. This thesis mainly focuses on evaluating the dissemination of information using Opportunistic Networks in urban scenarios, in which there are different densities and renewal rates of people, that is, with users who can enter and leave the evaluated scenario. Given that the existence of this type of real traces is very limited, this thesis proposes the generation of realistic traces. For this, through the use of a pedestrian mobility simulator, realistic traces of mobility have been defined with different degrees of density and renewal rates of users to evaluate different aspects of the Opportunistic Network with this approach. The analysis of the temporal and spatial characteristics of these generated traces reflects the realism of the scenarios that have been considered. The experiments related to the diffusion of messages made with these traces, confirm that the renewal rate has a high impact on the performance of the protocols, which is particularly evident when the message size is longer. Furthermore, considering vehicular scenarios, a study has also been carried out using real traces, following the same methodology to evaluate the dissemination of information. Since in the same way the mobility of these vehicles is linked to human behaviour, we have focused on the dissemination of information at certain times of the day depending on the number of vehicles in circulation, since this aspect has a significant impact on data diffusion. The results of all these experiments show that the diffusion of contents is affected mainly by two factors: degree of mobility and message size. Although it is well known that increasing the density of nodes increases the speed of diffusion, we show that, by maintaining the density of fixed nodes, the higher renewal rates cause the delivery ratio to decrease. In addition, we discovered that the relationship between message size and contact duration is also a key factor, showing that large messages can lead to very reduced overall performance. Based on these results, an improvement to the Epidemic protocol has been proposed, called EpidemicX2, which is based on the fragmentation of the data to be sent in order to take advantage of the short duration of the contacts. This protocol is particularly effective for the dissemination of large messages. The results show that the delivery rate increases, the average time in the delivery is reduced, without a substantial increase in terms of overload. / Finalmente, quiero agradecer a la República del Ecuador junto con la “Secretaría de Educación Superior, Ciencia y Tecnología e Innovación” - SENESCYT, por su programa de apoyo y financiar mis estudios. / Chancay Garcia, LJ. (2019). Evaluación y Modelado de Redes Oportunistas [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/124339