Gestão de desempenho numa rede celular

A realização desta dissertação tem como principal objetivo a análise de indicadores chave de desempenho numa rede celular de terceira geração - Universal Mobile Telecommunication System (UMTS), bem como a aplicação de técnicas matemáticas de previsão como apoio ao respetivo planeamento e otimização. Para o efeito, foi inicialmente efetuado um estudo sobre a evolução das comunicações de uma forma generalista, até às redes de nova geração, abordando individualmente, as de voz, as de dados e as comunicações móveis, assim como, uma breve descrição das organizações envolvidas nestas mudanças. No seguimento do estudo inicial, dando enfoque à tecnologia UMTS, foram expostas as suas características, a sua estrutura e arquitetura. Foram ainda elaboradas, duas comparações, com base em diferentes parâmetros, uma com a tecnologia da geração anterior e outra, com a de última geração. Com base nos conhecimentos adquiridos em diferentes pesquisas, foram estudados, os indicadores chave de desempenho (KPIs), as técnicas de planeamento e otimização, apresentando propostas de prevenção e soluções para problemas existentes na rede.

Impact of node mobility in user-centric routing

Recent paradigms in wireless communication architectures describe environments where nodes present a highly dynamic behavior (e.g., User Centric Networks). In such environments, routing is still performed based on the regular packet-switched behavior of store-and-forward. Albeit sufficient to compute at least an adequate path between a source and a destination, such routing behavior cannot adequately sustain the highly nomadic lifestyle that Internet users are today experiencing. This thesis aims to analyse the impact of the nodes’ mobility on routing scenarios. It also aims at the development of forwarding concepts that help in message forwarding across graphs where nodes exhibit human mobility patterns, as is the case of most of the user-centric wireless networks today. The first part of the work involved the analysis of the mobility impact on routing, and we found that node mobility significance can affect routing performance, and it depends on the link length, distance, and mobility patterns of nodes. The study of current mobility parameters showed that they capture mobility partially. The routing protocol robustness to node mobility depends on the routing metric sensitivity to node mobility. As such, mobility-aware routing metrics were devised to increase routing robustness to node mobility. Two categories of routing metrics proposed are the time-based and spatial correlation-based. For the validation of the metrics, several mobility models were used, which include the ones that mimic human mobility patterns. The metrics were implemented using the Network Simulator tool using two widely used multi-hop routing protocols of Optimized Link State Routing (OLSR) and Ad hoc On Demand Distance Vector (AODV). Using the proposed metrics, we reduced the path re-computation frequency compared to the benchmark metric. This means that more stable nodes were used to route data. The time-based routing metrics generally performed well across the different node mobility scenarios used. We also noted a variation on the performance of the metrics, including the benchmark metric, under different mobility models, due to the differences in the node mobility governing rules of the models.