Check this report and these slides. 

http://cordis.europa.eu/docs/projects/cnect/9/317959/080/deliverables/001-D512Ares20143639863.pdf

https://www.nsnam.org/tutorials/consortium15/Vehicular-Comms.pptx

You may consider using VSimRTI: https://www.dcaiti.tu-berlin.de/research/simulation/

Hope they help.

You need to generate a VANET in a hierarchical cluster with one node chosen as the cluster head and all communications must be done through the cluster head.

AFAIK, RSU & Nodes are the same things except RSU do not moving

in my research, i just add static nodes as RSUs

nb: i use NS2

Thanks for the answer Johan. Should I use the same approach to model CAs (certification authorities) ?

Instead of NS3, you can go for SUMO, OMNET++ and VEINS for the implementation of RSU in VANET.

Johan Ericka i am using a scenario generated from openstreetmap . Any idea how to go about adding RSUs in it ? ( NS2 being used )

Gopal Singh Rawat just create a static node in NS2 (as a RSU) and then adjust the RSU coordinates (manually) so it will placed at intersection :)

sorry, still can't find better approach to add RSU at intersection

hope this help

Gopal Singh Rawat I would also suggest you use a tool like SUMO and combine it with NetSim than waste time with NS-2.