I and all other students from my college have received MATLAB from the college. They all have the Communications Toolbox in their MATLAB, but I don't have it. How to add the toolbox in existing MATLAB software?
If you already have MATLAB installed, you can go to Add-ons -> Communications Toolbox. Add-ons is available on the toolstrip from MATLAB’s home tab.
If you do not have MATLAB installed, go to the Does your school have a MATLAB campus license? page to see if your university has a campus wide license for MATLAB. If they do, then that page will lead you to instructions to get MATLAB (and available toolboxes) installed.