It may be helpful you: http://www.q2s.ntnu.no/~paquerea/ns.php.

Btw, you can selectively modify some simulation parameters, making it closer to sensor networks.

http://dl.acm.org/citation.cfm?id=1506539

See this paper it might help you to perform simulation

Also see this link which says about how it supports multichannel

http://ackjack.com/adding-mcmimulti-channel-multi-interface-support-into-ns-2/

I attached NS-2 Manual for you, read it and hopefully you will get your answer easily.

in NS2.33 multichannel version you can use it