555 research outputs found
Simulation and Evaluation of Wired and Wireless Networks with NS2, NS3 and OMNET++
Communication systems are emerging rapidly with the revolutionary growth in terms of networking protocols, wired and wireless technologies, user applications and other IEEE standards. Numbers of industrial as well as academic organizations around the globe are bringing in light new innovations and ideas in the field of communication systems. These innovations and ideas require intense evaluation at initial phases of development with the use of real systems in place. Usually the real systems are expensive and not affordable for the evaluation. In this case, network simulators provide a complete cost-effective testbed for the simulation and evaluation of the underlined innovations and ideas. In past, numerous studies were conducted for the performance evaluation of network simulators based on CPU and memory utilization. However, performance evaluation based on other metrics such as congestion window, throughput, delay, packet delivery ratio and packet loss ratio was not conducted intensively. In this thesis, network simulators such as NS2, NS3 and OMNET++ will be evaluated and compared for wired and wireless networks based on congestion window, throughput, delay, packet delivery and packet loss ratio. In the theoretical part, information will be provided about the wired and wireless networks and mathematical interpretation of various components used for these networks. Furthermore, technical details about the network simulators will be presented including architectural design, programming languages and platform libraries. Advantages and disadvantages of these network simulators will also be highlighted. In the last part, the details about the experiments and analysis conducted for wired and wireless networks will be provided. At the end, findings will be concluded and future prospects of the study will be advised.fi=Opinnäytetyö kokotekstinä PDF-muodossa.|en=Thesis fulltext in PDF format.|sv=Lärdomsprov tillgängligt som fulltext i PDF-format
Conectividade definida por software em ambientes móveis
Broadband Internet access on trains has become an expected service for passengers,
and the rise in quality demand has been posing a challenge to service
providers. There are solutions for Internet access on trains that lack the
flexibility and redundancy needed for an improved QoS in the network. Thus,
this dissertation studies two new load balancing solutions, one distributed and
the other centralized. In an emulated train network, routers of each car communicate
their network statistics to other nodes of the network, to be used
in load balancing decisions. In the distributed solution, each router has the
capacity to make load balancing decisions, while in the centralized solution,
an onboard controller makes those decisions. The latter solution is based on
load balancing in an SDN environment. In this system, a remote entity aggregates
the passengers’ traffic and forwards it to an external network, or to the
Internet. The systems must provide an improved quality of experience to the
passengers on the train and the total avaliable bandwidth should be distributed
evenly by all cars. Requirements were established for the systems, which were
developed after an in-depth analysis of solutions for Internet access on board
found in the literature. After obtaining the results of the performance tests, it
was concluded that the systems improve the QoE of the passengers, as long
as the network conditions are approximately constant for an extended period.O acesso à Internet de banda larga em comboios tornou-se num serviço esperado
por parte dos passageiros e o aumento na exigência de qualidade tem
constituído um desafio para os prestadores de serviços. Existem soluções de
acesso à Internet em comboios que carecem da flexibilidade e redundância
necessárias para uma melhor qualidade de serviço na rede. Assim, esta
dissertação estuda duas novas soluções de balanceamento de carga, uma
distribuída e outra centralizada. Numa rede de comboio emulada, routers
de cada carruagem comunicam as suas estatísticas de rede para outros nós
da rede, para posteriormente serem tomadas decisões de balanceamento de
carga. Na solução distribuída, cada router tem capacidade de tomar decisões
de balanceamento de carga, enquanto que na solução centralizada, um controlador
dentro do comboio toma essas decisões. Esta última solução baseiase
num balanceamento de carga em ambiente SDN. Neste sistema, uma entidade
remota agrega o tráfego dos passageiros e encaminha-o para uma rede
externa, ou para a Internet. Os sistemas devem proporcionar uma qualidade
de experiência melhorada aos passageiros do comboio e a largura de banda
total disponível deve ser distribuída mais uniformememente por todas as carruagens.
Requisitos foram estabelecidos para os sistemas, que foram desenvolvidos
após uma análise aprofundada das soluções de acesso à Internet
em comboios encontradas na literatura. Após a obtenção dos resultados dos
testes de desempenho, concluiu-se que as duas soluções melhoram o QoE
dos passageiros, desde que as condições da rede sejam aproximadamente
constantes durante um certo período.Mestrado em Engenharia de Computadores e Telemátic
Prediction assisted fast handovers for seamless IP mobility
Word processed copy.Includes bibliographical references (leaves 94-98).This research investigates the techniques used to improve the standard Mobile IP handover process and provide proactivity in network mobility management. Numerous fast handover proposals in the literature have recently adopted a cross-layer approach to enhance movement detection functionality and make terminal mobility more seamless. Such fast handover protocols are dependent on an anticipated link-layer trigger or pre-trigger to perform pre-handover service establishment operations. This research identifies the practical difficulties involved in implementing this type of trigger and proposes an alternative solution that integrates the concept of mobility prediction into a reactive fast handover scheme
- …