## 4 Impact of Network Latency on Teleoperation
### End-to-End Delay  
The latency sources in this teleoperation feedback loop are shown in Figure 6. Latency sources and components of CAV teleoperation in an end-to-end loop include sensor exposure delay (e.g., camera capture delay) (\(\Delta S_{d}\)), encoding delay (\(\Delta E_{d}\)), data communication delay in terms of transmission (vehicle to the station (\(\Delta T_{d,1}\)) and station to vehicle (\(\Delta T_{d,2}\))), processing or decoding delay (\(\Delta D_{d}\)), visual display delay (\(\Delta V_{d}\)), operator response time \begin{table}
\begin{tabular}{c c c c c c} \hline \hline \multirow{2}{*}{**Category**} & \multirow{2}{*}{**Technology**} & \multirow{2}{*}{\begin{tabular}{c} **Latency during** \\ **Teleoperation (ms)** \\ \end{tabular} } & **User Data Rate** & **Maximum** & \multirow{2}{*}{**Coverage**} \\  & & & **(Mbps)** & & \\ \hline \multirow{6}{*}{Cellular} & 5G [10; 20; 25; 26; 27] & 11–13 & 4–8 & 1–10 Gbps & \begin{tabular}{c} Up to \\ several km \\ \end{tabular} \\ \cline{2-6}  & 4G (LTE) [10; 13; 10; 25; 26; 28; 29] & 100 & 3–8 & \begin{tabular}{c} 100 Mbps- \\ 1 Gbps \\ \end{tabular} & 5–50 km \\ \cline{2-6}  & 3G [10; 13; 20; 28] & 121–217 & Up to 3.1 & 3.1–14.7 Mbps & Up to 10 km \\ \cline{2-6}  & 2.5G (GPRS) & 500–1000 & 0.120 & 56–171.2 kbps & \(\sim\)35 km \\ \hline \multirow{6}{*}{Non-cellular} & Satellite [8] & 2000 & \(\sim\) 10\({}^{4}\) & \begin{tabular}{c} 10 Mbps (UL), \\ 1 Gbps (DL) \\ \end{tabular} & 1000 s of km \\ \cline{1-1} \cline{2-6}  & \
\begin{tabular}{c} LAN/WLAN/ \\ WiFi [8; 10; 13; 30] \\ \end{tabular} & 50 & 500 &
\begin{tabular}{c} 11/54/600/ \\ 1000 Mbps \\ \end{tabular} & \(\sim\)100 m \\ \cline{1-1} \cline{2-6}  & Bluetooth [13; 25] & 34–200 & 2 & 1.5–2 Mbps & \(\sim\)200 m \\ \cline{1-1} \cline{2-6}  & Zigbee [8; 25] & 200 & 0.250 & 250 kbps & 10–300 m \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Wireless technologies used for teleoperation. (\(\Delta O_{d}\)), and vehicle actuation delay (\(\Delta A_{d}\)) [25; 35; 36]. It is challenging to mitigate all these different sources of latency in a system [15]. The one-way latency is calculated as the sum of scheduling, transmission, and re-transmission time [37]. The information might be re-transmitted if lost. The sum of delays from camera capture to display is called capture-to-display latency or glass-to-glass latency [25], which is also the one-way uplink latency. The capture-to-display latency (\(\Delta_{C2D}\)) is given by  
\[UL=\Delta_{C2D}=\Delta S_{d}+\Delta E_{d}+\Delta T_{d,1}+\Delta D_{d}+\Delta V _{d} \tag{1}\]  
Similarly, on the one-way downlink (DL) side, control-to-response latency is the sum of delays from sending operator control commands to the vehicle actuation response. This latency also includes control command processing, encoding, and decoding delays. However, these delays are negligible when compared to delays in capture-to-display latency. Hence, they are not considered in the equation. The modified control-to-response latency (\(\Delta_{C2R}\)) can be represented as  
\[DL=\Delta_{C2R}=\Delta T_{d,2}+\Delta A_{d} \tag{2}\]  
Finally, the overall end-to-end latency (\(\Delta_{E2E}\)) or RTT is the sum of delays of all the components from uplink to downlink over the network. The end-to-end latency can be represented in an equation as  
\[\Delta_{E2E}=UL+DL=(\Delta S_{d}+\Delta E_{d}+\Delta T_{d,1}+\Delta D_{d}+ \Delta V_{d})+(\Delta T_{d,2}+\Delta A_{d}) \tag{3}\]  
For example, the latency values in different sources can be [25; 38]:  
* For camera capture, \(\Delta S_{d}\) = 17-33 ms at a frame rate of 30 fps. * For data encoding, \(\Delta E_{d}\) = 17-50 ms.
* For data transmission, \(\Delta T_{d,1}\) = 25-50 ms.
* For video decoding, \(\Delta D_{d}\) = 17-32 ms.  
Figure 6: Different sources of latency in CAV teleoperation control loop. The latency in the diagram is shown by red lines, which show approximately the magnitude of each component (for illustration purposes). The blue colour region is the uplink data from sensors to the operator perception interface.