I am new to cognitive radio networks so i am not sure which simulation tool to use to develop my algorithm and which site to visit to gain further understanding of the tool.
MATLAB is suitable . it is possible to model using simulink. few sample demo programs are available. it can support CR hardware and we can check it in real time system as well
I had worked in spectrum sensing algorithm with RTL SDR hardware and matlab & simulink in real time . many open source codes are available. it looks quite interesting with hardware rather than explicitly providing the input signals.
If it is MAC layer simulator I would suggest using NS3. They have a tool for coex simulation of WiFi and LTE which is the right in the topic of cognitive radio. And also you can build your own simulator with WiFi co-ex with WiFi, which would be pretty cool.