I think that NS2, NS3, or OMNET++  are the best choices for you.

I would suggest ns3

NS2, NS3 or OMNET++ are better simulators

i think Ns2 with CRCN implementation is very gud environment for CR-MAC

However, if you go with NS3 or Matlab then you have more flexibility .......

I would suggest  NS2 , QualNet

OPNET now bought by RIVERBED can be us to Simulate.

There are a lot of suitable software you could use such as OPNET, NS2 or NS3. 

Check out NS3.

The simulators which are mentioned by the researchers are well known and very good however, keep in mind that there is a learning time associated with them, so if u have a tight time frame, I would suggest that you write your own simulator (simulation environment), which u can do using C, Java, Matlab or any other language. 

Of course on the long run u are better to work with simulators like NS2, NS3 however (if u want to reduced the the learning time) u can always write ur own.

I agree with Osama........... 

Agree. there is steep learning curve for ns2 or ns3. Writing your own simulator is good option, but for the authenticity of results obtained a well known simulator is better choice in long run

Mr. Karyakarte brings a very important and valid point regarding the authenticity of the results.

I totally agree with you on that one.

Thank you for all your suggestions.

I totally agree with mandar as n's simulator are well known for network solutions  so keep working on NS  nd be patiance.  Research takes time am working since last for years on qos for CRN