Mobility and stability evaluation in wireless multi-hop networks using multi-player games

Multi-hop networks have gained a lot of interest in recent years. A lot of work was contributed in the field of protocol design and performance of multi-hop networks. It is generally accepted that mobility has a huge impact on the protocol performance; even more for multi-hop networks. Obtaining realistic measurements of mobility, however, is complex and expensive. Thus, we adopt virtual world scenarios to explore the mobility issue, by using the well-known multi-player game, Quake II. The advantage of the Quake II engine is that users move within virtual worlds under realistic constraints, whereas other mobility models may offer insuficient accuracy or operate under unrealistic assumptions. Moreover, it is very easy to create new virtual worlds and to adapt them to specialized needs. In this paper, we propose an analytical framework for mobility measurements in virtual worlds that could be adopted for the design of communication protocols. Our framework enables the study of the impact of mobility on connectivity and stability of the network, giving useful insights for improving communication performance. An interesting application of our approach is the analysis of coverage extension of so called hotspots or emergency situations, where the fixed network infrastructure is insuficient or non-existent. In these extreme cases, multi-hop networks can be used to setup communication quickly. As these situations comprise a plethora of different cases and scenarios, our model is appropriate for their analysis, due to its generality. We use our framework to investigate the performance of multi-hop networks based on IEEE 802.11a technology. In contrast to other contributions focusing only on connectivity, the IEEE 802.11a technology also considers multi-rate connections. Our framework covers the evaluation of simple connectivity as well as link quality stability in the presence of mobility, a combination that has not been considered thus far. Therefore we introduce two simple routing schemes and highlight the performance of these protocols in presence of mobility. Furthermore we come up with four definitions of stability and investigate protocols for multi-hop networks in terms of this parameter. Our other contributions are the changes to the Quake II engine and the availability of mobility trace files.