To simulate WSN, I think omnet++ can be a good choice.

Even, ns2 ns3 coud be possible, but I have experience with omnetpp, and it's a good tool for WSN and Easy to learn.

Thanks and how about the MiXim and castalia which one is the better choise as an extention on omnetpp

Castalia supported by OMN++ . I have an experience with OPNET, but it was so difficult.

I was working with OPNET but in my point of view is much easier than omnet :)

I will suggest Castalia.

I am not programming guy but it was very easy to learn castalia.

Castalia is considered good for WSN.

Some time back I did a coparative study of various open source WSN simulators.

You may find it useful (file is attached). Although I would recommend Catalia which is framework on top of Omnet++.

To view the realtime operation and 3D view of the sensor nodes and packet flow within the wirless network Omnet++ or Qualnet are the best tool but these are licensed one. for simple simulation like calculating QoS and measering the performance of WSN the NS-2 or NS-3 is preferable one.

Thanks all for providing these useful answers.

omnet++

Castalia/OMNET++ is considered good for WSN

Thanks for your feedback. I am relatively new in Omnet, how can I simulate the RSSI? 

You can start by using Castalia and OMNET++ when clustering is considered. For example, nodes belong to each cluster in  LEACH use  RSSI to select the best cluster head. 

how to transmit the video pkt thr omnetpp

Hi Anupama,

I think Castalia and omnet using M3WSN model can be used to transmit video packets over WSNs. More can be found here

http://dl.acm.org/citation.cfm?id=2512774

Thank you sir

Welcome

Castalia Simulator is the best framework based on omnet++. It is specifically designed to simulate wide range of protocols for WSN and WBAN.