# Communication Architecture in Mixed-Reality Simulations of Unmanned Systems
## 7 Experiments
### Results  
The mean values and standard deviations of the measured data rates in the HW scenario are shown in Figure 9. The results indicate the above-proclaimed transmission data rates of the HWEs.  
In the MR scenario, the GCS uses the modem of the HWE\({}_{1}\) from the previous case. The measured average data rates and standard deviations are shown in Figure 10. The characteristics are almost similar to those from the first experiment. The data rates measured between the two SWEs are higher with a lower variance, which may be caused by a low precision of the employed wireless network model and by the fact that the environmental background noise has not been taken into account during the simulation. On the other hand, the variances of the real traffic (data from HWE\({}_{3}\) as shown in Figure 10a,b, and data from SWE\({}_{1}\) and SWE\({}_{2}\) shown in Figure 10c) are higher. This is most likely caused by the MAC in situation when the GCS's modem tries to send twice as much data compared to the modems in the HW scenario. The similarity in the characteristics of the SWE transmissions arises from the fact that the same modem is used for the message exchange; thus, the system operates in similar conditions during the transmission. It is obvious that, in this configuration, the GCS's modem needs to transmit twice as much data compared to the first experiment since it is now transmitting data  
Figure 8: Two experimental scenarios—(**a**) the three-HWE (HW) scenario with three hardware entities and (**b**) the MR scenario where one hardware and two simulated entities communicate via GCS relay.  
for both SWEs. However, thanks to the lower bandwidth occupancy caused by one missing modem, and because the model is physically capable of transmitting this amount of data, the packets are transmitted with almost no change in bandwidth in comparison with the first experiment. The results of this experiments demonstrate that both configurations can be used without a significant difference nor with any effect on simulation accuracy.  
Besides the first comparison, we also performed MR experiments with the testbed configuration similar to the MR scenario, but without any wireless network modeling, and the UDP packets were sent at a rate of 20 kBps to see how the system would behave in situations where the entities are trying to send more data than the real RF modems can transmit without any regulatory mechanism. The achieved results are depicted in Figure 11.  
According to Figure 11c, the results indicate what happens when the modem tries to send more data of which it is physically capable. There is a significant drop in transmitted data rates and a significant increase in their variance. The Microhard modems have their MAC mechanisms, but they are not satisfactory in this case, and many packets are lost. SWEs transmit much more data between each  
Figure 10: Mean values and standard deviation of data rates of transmissions from neighbors measured at entities (**a**) SWE\({}_{1}\); (**b**) SWE\({}_{2}\); and (**c**) HWE\({}_{3}\) in the MR scenario using the high-fidelity MR architecture.  
Figure 9: Mean values and standard deviation of data rates of transmissions from neighbors measured at entities (**a**) HWE\({}_{1}\); (**b**) HWE\({}_{2}\); and (**c**) HWE\({}_{3}\) in the HW scenario.  
other than with the HWE (as can be seen in Figure 11a,b), and the simulation of the communication cannot be used for high-fidelity validation of the communication system.