Measurement-based Modeling of End-to-end Delays in Wlans with Ns-2

We enhance the standard ns-2 model for IEEE 802.11 WLANs such that it reflects the delays that are measured in a real ad-hoc network composed of laptops. From timestamps for UDP transmissions, which are recorded at several points on the way from application layer to application layer in a lowly-loaded system, we derive various empirical distributions, which we incorporate into the ns-2 model in order to better capture the real system. For validation, we compare simulated and measured end-to-end delays for UDP transmissions under different load conditions. Our experiments demonstrate the difficulties encountered when tuning a generic and widely used simulation model to a real scenario and suggest that cross-correlation among subsequent delays need to be considered for a satisfactory match of simulation and measurements.