## 4 Development and Validation of the Platform
### Application Performance
#### 4.4.1 QoS Metrics and Measurement Goals  
To ensure a comprehensive evaluation of KPIs, each measurement process must be designed with practical, real-world conditions in mind, as shown in Table 3.  
In terms of network performance, KPIs like RTT, throughput, and reliability provide essential insights into the system's communication robustness and efficiency. RTT measures the time for a data packet to travel to its destination and back, indicating the latency in the network path. According to our preliminary laboratory tests, we estimate that more than 30 ms latency would impede real-time video streaming. Throughput, captured in both the uplink (UL) and downlink (DL) directions, evaluates the system's capacity to handle data-intensive applications, especially under high-load conditions. In order to eventually support the immersive remote control of four robots (two per site), we estimate that 32 Mb/s per site is required in the uplink (two 15 Mb/s 4K 360 video streams plus two 1 Mb/s telemetry flows), whereas only 1 Mb/s per site is required in the downlink (two 500 kb/s telecontrol flows). Since the cockpits are placed only at n78 in one of the sites, this band requires double the capacity of n40. Reliability is tracked continuously to assess the consistency of network connectivity, which is crucial for applications requiring uninterrupted, real-time data transmission. According to our experience, packet loss must be maintained below 1% for efficient video decoding. For video streaming, metrics like the streaming bitrate and latency are key for assessing the quality and responsiveness of transmitted visual information. The streaming bitrate reflects the amount of video data transferred per unit time, impacting image quality and visual clarity. We are limited by the parameters of the camera used in this prototype, which generates 15 Mb/s of traffic for a 4K 360 video using the RTSP protocol. Latency in video streaming is measured for 360-degree video streams, capturing the time delay between capturing the video feed and its display. Early measurements carried out in our laboratory show that the streaming latency is 300 ms on average for RTSP streaming over the 5G network, including its visualization in the user interface. These thresholds, however, are close to the ones defined in industry best practices [56] and empirical studies [57] in teleoperation and VR systems. For telecontrol and feedback, precision is critical, as it directly affects the efficacy of the operation. The Command-to-Reception delay is recorded from the moment a command is issued by the user until the corresponding action is received on the robot. On the other hand, the Command-to-Execution delay also considers that the corresponding action is executed by the robot. Note that the execution depends on mechanical and electrical aspects \begin{table}
\begin{tabular}{l l l} \hline \hline
**Application Metrics** & **Measurement Attributes** & **Measurement Goals** \\ \hline \multirow{4}{*}{**Network performance**} & - Round-Trip Time & - \(<\)30 ms \\  & - Throughput for n40 & - UL: \(>\)32 Mb/s, DL: \(>\)1 Mb/s \\  & - Throughput for n78 & - UL: \(>\)2 Mb/s, DL: \(>\)64 Mb/s \\  & - Reliability & - \(>\)99\% \\ \hline \multirow{2}{*}{**Video streaming**} & - Streaming bitrate (UL) & - \(<\)15 Mb/s \\  & - Streaming latency (360) & - \(<\)300 ms \\ \hline \multirow{4}{*}{**Telecontrol and feedback**} & - Command-to-Rec delay & - \(<\)50 ms \\  & - Command-to-Exec delay & - \(<\)350 ms \\ \cline{1-1}  & - E2E latency & - \(<\)650 ms \\ \cline{1-1}  & -Haptic feedback delay & - \(<\)30 ms \\ \hline \hline \end{tabular}
\end{table} 
Table 3: Application performance metrics of Immersive Robot Racing, comprising key metrics and corresponding measurement goals that are essential for ensuring effective teleoperation. The metrics cover aspects like network performance, video streaming, and telecontrol and feedback. not related to data communication, which is not the scope of our work but certainly has an impact on the user experience.