Wireless networking research is fundamentally dependent upon simulation. Analytically quantifying the performance and complex behavior of even simple protocols on a large scale is often imprecise. On the other hand, performing actual experiments is onerous: acquiring hundreds of devices, managing their software and configuration, controlling a distributed experiment and aggregating the data, possibly moving the devices around, finding the physical space for such an experiment, isolating it from interference and generally ensuring ceteris paribus, are but some of the difficulties that make empirical endeavors daunting.
At a minimum, one would like to simulate networks of many thousands of nodes.
However, even though a few parallel discrete event simulation environments
have been shown to scale to networks of beyond 
nodes, slow sequential
network simulators remain the norm [8]. In particular, most
published ad hoc network results are based on simulations of few nodes only
(usually fewer than 500 nodes), for a short duration, and over a small
geographical area. Larger simulations usually compromise on simulation detail.
For example, some existing simulators simulate only at the packet level
without considering the effects of signal interference. Others reduce the
complexity of the simulation by curtailing the simulation duration, reducing
the node density, or restricting mobility.
SWANS is a Scalable Wireless Ad hoc Network Simulator built atop the JiST platform, a general-purpose discrete event simulation engine. SWANS was created primarily because existing wireless network simulation tools are not sufficient for current research needs. SWANS also serves as a validation of the virtual machine-based approach to simulator construction.