We present Simulation-based Radio (SimbaR), an extension to our open-source prototyping system LAN Radio to couple IEEE 802.11-based communication channels of real world and simulation using commodity hardware. These coupled radio channels enable testing of prototypes (e.g., vehicular ECUs) in large scale simulation studies without the need for changing the IEEE 802.11 access layers (i.e., MAC and PHY) of these devices. However, fairness for channel access has not been investigated for such systems, yet. By applying MAC layer adjustments to the testbed at runtime, SimbaR can control the fairness for channel access between simulated stations and real world prototypes (e.g., an ECU). Besides transceiving information from simulation to the real world and vice versa, SimbaR can recreate interference observed in the simulation in the real world. In first experiments we show the effectiveness of our open-source prototyping approach by highlighting the necessity of proper channel access schemes and interference generation for coupled radio channels.