The other week there was an interesting interview published on the NeBeans Zone by Geertjan Wielenga about RaPSor - a framework that can simulate the propagation of radio channels built using the NetBeans platform. The man answering the questions was Lilian Aveneau, who carries out his research into 3D rendering of radio communications at the XLIM/SIC laboratory of the University of Poitiers.
I've only just had a chance to download and have a play with the RaPSor application from its sourceforge project site. There are example scenes that can be downloaded from the files download page to try simulations on and it is quite interesting to see the application simulate the coverage of radio signals around buildings. The simulations can be shown in 2D or, if you have the Java 3D API installed, 3D.
If you want to get some background on the research and what RaPSor hopes to achieve there's also a paper called RaPSor: a Radio Propagation Simulator, Presentation and Use Cases in the files download page .