This talk introduces gr-winelo, an in-the-loop simulation framework for communication networks which are based on the GNU Radio software radio toolkit. gr-winelo mimics the behavior of common RF frontends such as the USRP, but instead of sending the signal over the air, a central server plays the role of the wireless communication channel. Arbitrary channel models can be simulated, by passing their respective GNU Radio processing block to the server. Since this whole setup is completely transparent to GNU Radio applications, it is at any moment possible to switch between simulations and real-world tests. For the Demo a frequency hopping network will be simulated and analyzed using gr-winelo.