Emerging infrastructure-less network architectures such as WSNs consist of devices that perform packet processing in software. General-purpose network simulators do currently not possess models to simulate the intra-node delay of such devices. Consider a real TelosB mote that runs TinyOS which spends seven and fifteen ms on processing packets of size 36 and 124 bytes. Failing to simulate that results in inaccurate simulation of packet loss, jitter, and latency. In this thesis, we create a communication software model of TelosB to include its temporal behavior for more accurate WSN simulations in the ns-3 simulator. A challenge in doing so is to create a tracing framework for TinyOS that can be used to accurately and reliably trace its behavior. The evaluation of the model shows that it is accurate, scalable, and has a significant impact when including it in a simulation.