Forgalom modellezési módszerek fejlesztése = Advanced traffic modeling techniques

A projekt alapvetően sikeresen járult hozzá a vizsgált szakterület eredményeinek bővítéséhez és a résztvevő kutatócsoport fejlődéséhez. A projekt eredményihez kapcsolódó dolgozatok alapján PHD fokozatot szerzett Bodrog Levente és Saffer Zsolt. A projekt eredményeit összegző publikációk együttes impakt faktora ~22. A szakmai eredmenyek közül Markov érkezési folyamatok alapvető tulajdonságait összegző cikk (A minimal representation of Markov arrival processes and a moments matching method) emelhető ki, amelyik időközben az ezen folyamatok illesztési korlátait vizsgálló munkák alapjává vált. | The project successfully enhanced the field of traffic modeling of computer and communication systems and helped to improve the carrier of the involved research group. Based on the their theses summarizing parts of the results of the project Bodrog Levente and Saffer Zsolt were awarded the doctor of philosophy degree. The cumulated impact factor of the journal papers publish the research results of the project is about 22. The most remarkable research results are in the paper summarizing some basic properties of Markov arrival processes (A minimal representation of Markov arrival processes and a moments matching method), which become a basic reference for subsequent works dealing with the fitting properties of these processes

Non-atomic Games for Multi-User Systems

In this contribution, the performance of a multi-user system is analyzed in the context of frequency selective fading channels. Using game theoretic tools, a useful framework is provided in order to determine the optimal power allocation when users know only their own channel (while perfect channel state information is assumed at the base station). We consider the realistic case of frequency selective channels for uplink CDMA. This scenario illustrates the case of decentralized schemes, where limited information on the network is available at the terminal. Various receivers are considered, namely the Matched filter, the MMSE filter and the optimum filter. The goal of this paper is to derive simple expressions for the non-cooperative Nash equilibrium as the number of mobiles becomes large and the spreading length increases. To that end two asymptotic methodologies are combined. The first is asymptotic random matrix theory which allows us to obtain explicit expressions of the impact of all other mobiles on any given tagged mobile. The second is the theory of non-atomic games which computes good approximations of the Nash equilibrium as the number of mobiles grows.Comment: 17 pages, 4 figures, submitted to IEEE JSAC Special Issue on ``Game Theory in Communication Systems'

Fuzzy Depth Based Routing Protocol for Underwater Acoustic Wireless Sensor Networks

Underwater Wireless Sensor Networks consist of a variable number of sensors and vehicles that are implemented to perform collaborative monitoring tasks over a given area. However, designing energy-efficient routing protocols for this type of networks is essential and challenging because the sensor nodes is powered by batteries, underwater environment is harsh and propagation delay is long. Most of the existing routing protocols used for underwater wireless sensor networks, such as depth based routing (DBR) protocol use a greedy approach to deliver data packets to the destination sink nodes at the water surface. Further, DBR does not require full-dimensional location information of sensor nodes. Instead, it needs only local depth information, which can be easily obtained with an inexpensive depth sensor that can be equipped in every underwater sensor node. DBR uses smaller depth as the only metric for choosing a route. This decision might lead to high energy consumption and long end to end delay which will degrade network performance. This paper proposes an improvement of DBR protocol by making routing decisions depend on fuzzy cost based on the residual energy of receiver node in conjunction with the depth difference of receiver node and previous forwarder node and the number of hops traveled by the received packet. Our simulation was carried out in Aquasim an NS2 based underwater simulator and the evaluation results show that the proposed fuzzy multi metric DBR protocol (FDBR) performs better than the original DBR in terms of average end to end delay, packet delivery ratio and energy savin

Multimodal, software defined networking for subsea sensing and monitoring.

The prevalence of oceanic industry and ocean borne interests has given rise to the concept of the Underwater Internet of Things as a vector for automation and data analytics in an environment hostile to anthropomorphic activity. Through the Internet of Underwater Things, it is theorised that sensors along the ocean floor or otherwise can be densely connected to the internet through wireless acoustic or optical links. However, both technologies have significant disadvantages that prevent either becoming a dominant technology. This project proposes a wireless software defined multimodal network infrastructure, that is proven using channel modelling and power analysis calculations, to be capable of robustly transmitting sensor data from source to sink by managing each technology according to its optimal environment. It was found that it is achievable to populate an opto-acoustic network in such a way that Successful Delivery Ratio becomes 90%-100% in clear water whilst achieving a 17% saving in overall energy consumption in a network mounted on a pipeline at 200 m depth when compared to a stand-alone equivalent acoustic network

On the challenges of establishing disjoint QoS IP/MPLS paths across multiple domains

MPLS is being actively adopted as the core switching infrastructure at the intradomain level. This trend is mainly attributable to the undeniable potential of MPLS in terms of virtual private networks (VPNs) management, traffic engineering (TE), QoS delivery, path protection, and fast recovery from network failures. However, little progress has been made to attain the expected extension of MPLS label-switched paths (LSPs) across domain boundaries. Among the problems that remain unsolved is how to efficiently find and establish primary and protection interdomain LSPs for mission-critical services subject to QoS constraints. This article explores the major limitations hindering the deployment of these kinds of LSPs across multiple domains, in the context of the current interdomain network model. We describe the critical problems faced by the research community, and present our vision on how to rationally overcome some of the problems exposed. Our perspective is that we should be prepared for rather coarse-grained solutions as long as we need to coexist with the current interdomain network modelPostprint (published version

Reactive and proactive routing in labelled optical burst switching networks

Optical burst switching architectures without buffering capabilities are sensitive to burst congestion. The existence of a few highly congested links may seriously aggravate the network throughput. Proper network routing may help in congestion reduction. The authors focus on adaptive routing strategies to be applied in labelled OBS networks, that is, with explicit routing paths. In particular, two isolated alternative routing algorithms that aim at network performance improvement because of reactive route selection are studied. Moreover, a nonlinear optimisation method for multi-path source-based routing, which aims at proactive congestion reduction is proposed. Comparative performance results are provided and some implementation issues are discussed.Postprint (published version

Mecanismos de descubrimiento de gateways adaptativos para redes ad hoc conectadas a redes fijas

Los principales objetivos de este TFC son el análisis de un nuevo mecanismo de descubrimiento de gateways para las redes ad hoc conectadas a redes fijas y la propuesta de un nuevo mecanismo, variante del mecanismo anterior. Una vez analizados los dos mecanismos los compararemos con los mecanismos que se implementan en la actualidad y sacaremos conclusiones sobre que mecanismo es más eficiente para las aplicaciones en tiempo real que funcionan sobre redes ad hoc conectadas a redes fijas. Hemos fragmentado el proyecto en varios puntos, para entender el funcionamiento de este tipo de redes, sus protocolos, sus características, y finalmente llevar a cabo nuestros objetivos. Los puntos son los siguientes: • Estudio de las redes ad hoc • Estudio de los diferentes mecanismos de descubrimiento de gateways de redes ad hoc que existen en la actualidad. • Estudio de un nuevo protocolo de descubrimiento de gateways con provisión de QoS. • Propuesta y estudio de una nueva variante basada en protocolo anterior. • Simulación de los protocolos de descubrimiento de gateways híbrido, adaptativo y nuestra variante. • Comparación de los resultados de las simulaciones y conclusiones. • Realización de la patente de los protocolos propuestos.La gran evolución que han sufrido las comunicaciones en los últimos años y la necesidad surgida de estar conectado en cualquier momento y en cualquier lugar, ha permitido que las redes inalámbricas tomen un papel relevante en las comunicaciones actuales, permitiendo movilidad y conectividad permanentes. En este TFC nos centraremos en el estudio, análisis y simulación de las redes ad hoc conectadas a una red fija a través de gateways. Analizaremos los tres mecanismos de descubrimiento de gateways que se utilizan actualmente para las comunicaciones en las redes ad hoc. Presentaremos un nuevo protocolo de descubrimiento de gateways que mejora el rendimiento y la eficiencia de la red y añadiremos una nueva variante, derivada de este nuevo protocolo, ideada por nosotros. Con estas nuevas propuestas se consigue añadir QoS (Quality of service, calidad de servicio), inexistente en los protocolos actuales, priorizando el tráfico de las aplicaciones de tiempo real (VoIP) frente al resto de flujos de la red. Para obtener los datos necesarios sobre el comportamiento de estos nuevos protocolos, se ha optado por utilizar el programa de simulación de redes NS (Network Simulator). En estas simulaciones se ha comparado el comportamiento del protocolo de descubrimiento de gateways híbrido, con el protocolo propuesto y con nuestra variante. Analizando los resultados de las simulaciones vemos que el comportamiento del protocolo propuesto y de nuestra variante mejoran la eficiencia de la red ad hoc conectada a la red fija. Por último, se han seguido los pasos necesarios para presentar una solicitud de patente en la Oficina Española de Patentes y Marcas, del protocolo de descubrimiento de gateways presentado y nuestra variante