WSN is a discrete-event system [1]. Research activities in the area of WSNs need expositive performance statistics about systems, scenario, protocols, applications, and gathered data. Various experimental tools are in existence for fullling these requirements; some are in practical use though

Abstract .......................................................................................................................................... 495 18.1 Introduction ........................................................................................................................ 495 18.2 Prior Research Work .......................................................................................................... 496 18.3 Simulation Evaluation Criteria ........................................................................................... 498 18.4 Necessity of Simulation ...................................................................................................... 499 18.5 Type of Simulation .............................................................................................................500 18.6 Classication/Categorization of Simulators .......................................................................500 18.7 Phases in a Simulation Study .............................................................................................502 18.8 Simulators (or Simulation Environments) for WSNs: Study and Recent Advances ..........502 18.9 Emulators (or Emulation Environments) for WSNs: Current Status ..................................503 18.10 Future Research Directions ................................................................................................ 503 18.11 Conclusion .......................................................................................................................... 514 References ...................................................................................................................................... 514

others are in literature. Three main popular techniques are used for analyzing the performance of wired and wireless networks:

• Analytical methods: Analytical methods may provide quick insight but fail to give near about realistic results for the reasons like limited energy, memory, and processing power and sheer number and unattended and harsh deployment environments of sensor nodes [2].