Some friends found that it is very hard to implement a routing module (adhoc & wsn) for NS2. Yes, it's so difficult. But We must learn how it works. From my point of view, I think you need to know some interface between routing module and other layers. So, try to learn them from a really simple example (It costs only one day for my collegue in Germany Lab to learn its mechanism, so you can do it too).

1. Read the tutorial: http://masimum.dif.um.es/?Documents

2. A very simple module: NOAH http://icapeople.epfl.ch/widmer/uwb/ns-2/noah/

Any problems, plz contact me:)