A fast simulation framework for IEEE 802.11-operated wireless LANs

In this paper, we develop a fast simulation framework for IEEE 802.11-operated wireless LANs (WLANs), in which a large number of packets are abstracted as a single fluid chunk, and their behaviors are approximated with analytic fluid models and figured into the simulation. We first derive the analytical model that characterizes data transmission activities in IEEE 802.11-operated WLANs with/without the RTS/CTS mechanism. All the control overhead incurred in the physical and MAC layers, as well as system parameters specified in IEEE 802.11 are faithfully figured in. We validate the model with simulation in cases in which the network is and is not saturated. We then implement, with the use of the time stepping technique, the fast simulation framework for WLANs in ns-2, and conduct a comprehensive simulation study to evaluate the framework in terms of speed-up and errors incurred under a variety of network configurations. The simulation results indicate that the proposed framework is indeed effective in simulating IEEE 802.11-operated WLANs. It achieves as much as two orders of magnitude improvement in terms of execution time as compared to packet-level simulation. The performance improvement is more pronounced when the number of wireless nodes, the number of applications running on each wireless node, or the number of WLANs increases. The relative error, on the other hand, falls within 2 % in all cases, as long as the value of the time step is appropriately determined.