Shawn: A new approach to simulating wireless sensor networks
  We consider the simulation of wireless sensor networks (WSN) using a new approach. We present Shawn, an open-source discrete-event simulator that has considerable differences to all other existing simulators. Shawn is very powerful in simulating large scale networks with an abstract point of view. It is, to the best of our knowledge, the first simulator to support generic high-level algorithms as well as distributed protocols on exactly the same underlying networks. 
Alexander Kroeller, Dennis Pfisterer, Carsten Buschmann, Sandor P.   Fekete, and Stefan Fischer