Real-Time Simulation of Multi-Hop Ad hoc Networks

An ad hoc network comprises a collection of mobile hosts such as laptops with wireless radio interfaces dynamically to a temporary network. Due to the limited transmission range of these interfaces, multiple network hops may be needed for two hosts to communicate with each other. Numerous new and innovative developments particularly in the telecommunication and (mobile) network sector call for new or extended network simulators. In this work we want to emphasize the range of use and elaborate on the development of a tool for simulating network delay and loss characteristics in real-time for multi-hop ad hoc networks (MANETs) [Per01]. A real-time network delay and loss simulator (RDLS) is understood as a system providing network interfaces where other systems can connect to. These systems can host distributed applications communicating over the RDLS without noticing any differences between the simulator and a physical network. The main issue of a RDLS is to compute the effects of the path of packets through a simulated switching network, which results in delays or losses. Also it has to deliver each packet if not decided to be lost with the computed delay accurately. The simulated network may include network-internal sources of background load as well as interfaces for external sources of load (e.g. real or modeled applications, possibly combined with artificial load generators, etc). With an RDLS two main tasks can be addressed without building up a complete physical network: On the one hand the behaviour of a distributed application can be evaluated assuming different network configurations (e.g. different levels of load, more or less loss-affected links, etc). On the other hand the behavior of the network can be evaluated with changes made on the application side (e.g. load dependant application-layer encoding). Examples for commonly used distributed real-time applications are video conferencing systems or voice over IP. Main requirements an RDLS has to fulfill are