I receive many emails after commenting in a post in Sensor network, that's why I'm going to share some of my experiences in form of these articles to all the beginner researchers in WSN.

There is a compilation of various Network simulators, however which is the best can only be determined by yourself for your purpose:

1. Comparison of simulators: http://ow.ly/8Cr8P

2. How to choose best simulators: http://ow.ly/8Cr7r

OPNET is commercial version, and it is NOT OPNET++, but it is OMNET++; see this guide: http://ekendraonline.com/sensor-networks/basic-guide-to-omnet-installation-configuration-and-building-2232.html

Please, share the links if they are helpful to you.

Thank you.