I used Cooja, which comes with Contiki OS (http://www.contiki-os.org/start.html). It helps evaluate interoperability among network stacks (e.g., Contiki vs. TinyOS), energy consumption, among other things. It includes simple radio propagation models and cycle accurate processor emulation for major sensor platforms, such as SKY, Z1, etc.
I was tested NS-2 ( I was Previously Supervised 4 MSc. students to work on ' namely .. Ahmed, Enas, Mohammed and Alla ), but another students ( Alyaa used Net logo ) and Fawziyah is now working on Net Logo.
Another MSc student ( SURRA) Still Working on network Scalability Using OpNet.
The optimal way to select the best network simulator depends on your project requirements. For example, NS-2 is the best if you need to simulate mobility in WSNs.
Wireless Networks simulators exhibit different features and models. Each has advantages and disadvantages, and each is appropriate in different situations. In choosing a simulator from the available tools, the choice of a simulator should be driven by the requirements. Developers must consider the pros and cons of different programming languages, the means in which simulation is driven (event vs. time based), component-based or object oriented architecture, the level of complexity of the simulator, features to include and not include, use of parallel execution and ability to interact with real nodes.