# IoTactileSim: A Virtual Testbed for Tactile Industrial Internet of Things Services
## 3 Result and Discussion
### Scenario I: Teleoperation with 3 DoF  
Scenario I considers the offline experimentation, where publicly available 3 DoF haptic traces in [22] on teleoperations were utilized. To record the haptic traces, a human operator employs a haptic device (Phantom Omni) at the master to interact with the virtual environment, which acts as a slave domain. The virtual environment is comprised of a rigid movable cube lying on a wooden, smooth surface. The human operator makes an interaction (static and dynamic) with the rigid cube via the haptic device and receives force feedback. Figure 7 illustrates the 3 DoF position and velocity control by the human operator via the haptic device and the received force feedback of the used haptic dataset [22] for experimentation. In the proposed IoTactileSim testbed, we transmit the control signals (position/velocity) from the master side to the slave side and get the haptic feedback (force). To minimize the E2E communication delay, a common practice is to transmit the haptic traffic packets instantly after receiving sensors' data, resembling a real-time tactile industrial IoT application. We adopt the same method in our experiments; after reading the sensors data, the system makes packets of the haptic traces as following:  
\[PacketSize=\mathit{Ethernet}/\mathit{UDP}/\mathit{IP}/8\times N_{DoF} \tag{1}\]  
where \(\mathit{Ethernet}/\mathit{UDP}/\mathit{IP}\) indicates the header of the ethernet, user datagram protocol, and internet protocol layer, respectively. \(N_{DoF}\) is the number of DoF in the experimental data. We are using 3 DoF, so the formulation can be evaluated as:  
\[Packet\;Size=14/8/20/8\times 3\] \[Packet\;Size=14+8+20+24=78\]  
The interface of the IoTactileSim during communication between master and slave domain is depicted in Figure 8. At the master domain, control signals from utilized 3 DoF haptic traces are selected and transmitted to the slave domain through the network domain. Similarly, after receiving specific control signals, the slave domain returns the corresponding force feedback to the master domain. The overview of the data flow interfaces between master and slave for the scenario \(I\) is depicted in Figure 8.  
The performance analysis for a scenario I in terms of round trip delay is presented in Figure 9. To investigate the effect of the number of haptic data packets on round trip delay for IoT applications, the scenario I was simulated for the number of haptic data traces \(=\) 10 to 10,000. The latency investigation using IoTactileSim for a scenario I with the number of packets \(=\) 10, 100, 1000, 10,000 is depicted in Figure 9a-d, respectively. It can be seen clearly from the results, the tendency with an increase in the number of haptic data packets the round trip delay decreases from 5 to 2 ms. In Figure 9a, with the number of packet \(=\) 1, the packet latency approaches 6 ms as compared to Figure 9b-d, where packet latency is below 5 ms. To elaborate this latency decrement in detail, Figure 10 illustrates the packet delay histogram for a scenario I.  
Figure 7: Dynamic interaction of the human operator with virtual application via haptic device. ( **a**) positions of the human operator’s hand at master side device, (**b**) velocity traces of the operator (**c**) force data traces of the teleoperator x, y and z-axis. Figure 8: IoTactileSim interface for scenario I experiment. Figure 9: Packet latency investigation for scenario I haptic data transmission; (**a**) data packets = 10, (**b**) data packets = 100, (**c**) data packets = 1000, (**d**) data packets = 10,000. Contrary to Figure 9, the results in Figure 10 reveal the latencies of the most frequent haptic data packets. Similar to the results presented in Figure 10a-d, the simulation results in Figure 10a-d also indicate the decrease in packet latencies from 5.8 to 2.1 ms. From Figure 10a-d, it can be seen clearly that most of the haptic traces latencies centered between 1 to 2 ms, which is one of the stringent requirements for the tactile IoT services.