## 2 Communication Challenges and Service Types
### Demands and Requirements of Communication Services  
The primary task of the communication system research and design is to identify every service type and quantify the corresponding requirements. As a new mode of transportation, the train-to-ground communication of Hyperloop requires a variety of communication services to assure the safe operation. In [13], we have already presented a summary of accurate communication key performance indicators (KPIs), including data rate, end-to-end transmission latency, and bit error rate (BER), which is presented in Table 2.  
Generally, the communication service types of the Hyperloop can be divided into two categories: mission-critical services and passenger communication service data from the aspects of the intended applications. The former one is used to ensure the security of train safe-operation and usually refers to the communication served for operation control system (OCS), traction control system (TCS), operational voice communication system (OVCS), video surveillance (VS), train operation status monitoring (TOSM), and passenger information service (PIS). Different from the HSR, the Hyperloop puts up with more stringent requirements on data rate, end-to-end latency, and BER, which can be regarded as the uRLLC requirements in the 5G communication system [26]. As for the passenger service, it mainly involves the service data such as on-vehicle video conference, online games, chatting, live broadcast, etc., generated by passengers, but having little effect on the safe-operation. We mainly consider the high-speed Internet access service with a large bandwidth requirement. Assume a per-passenger requires a data rate of 0.1-1 Gbps for 5G access, mobile user penetration rate of 90%, 5G terminal penetration rate of 80%, an activation rate of 70%, and a use rate of Internet access service to be 50%. Hyperloop has a total passenger capacity of 15. It follows that the total passenger throughput of the train is ((0.1, 1) \(\times\) 70% \(\times\) 50%) \(\times\) (15 \(\times\) 90% \(\times\) 80%) = 0.378-3.78 Gbps, which far exceeds the capability of the existing public mobile cellular system [27]. This type of service can be considered as the eMBB communication in 5G. Based on above analysis, we list some important train-to-ground wireless communication KPIs for communication based train control system (CBTC), HSR, Shanghai maglev, and Hyperloop in Table 2[28; 29]. Since detailed descriptions of each service along with the explanations about the KPI values are given in our previous work [13], we just present a brief overview herein. \begin{table}
\begin{tabular}{l c c c c c c c c c c c c} \hline \hline
**Data** & \multicolumn{3}{c}{**Data Rate/kbps**} & \multicolumn{3}{c}{**Latency Requirement/ms**} & \multicolumn{3}{c}{**BER**} \\ \cline{2-13}
**Type** & & & & & & & & & & & & & \\ \hline \multicolumn{13}{c}{**Mission-critical services**} \\ \hline \multirow{3}{*}{CBTC} & \multirow{3}{*}{CBTC} & HSR & Maglev & Hyperloop & CBTC & HSR & Maglev & Hyperloop & CBTC & HSR & Maglev & Hyperloop \\ \cline{2-13}  & & & & & & & & & & & & \\ \hline TCS & \multirow{3}{*}{200/train} & \multirow{3}{*}{1000/train} & \multirow{3}{*}{100} & \multirow{3}{*}{50} & 5 & 1 & 10\({}^{-6}\) & 10\({}^{-6}\) & 10\({}^{-6}\) & 10\({}^{-6}\) \\ \cline{1-1} \cline{5-13}  & & & & & & & & & & & & & \\ \cline{1-1} \cline{5-13}  & & & & & & & & & & & & \\ \hline OVCS & \multicolumn{3}{c}{32/channel} & \multirow{3}{*}{100} & \multirow{3}{*}{300} & \multirow{3}{*}{150} & 40 & 40 & 10\({}^{-2}\) & 10\({}^{-3}\) & 10\({}^{-5}\) & 10\({}^{-5}\) \\ \cline{1-1} \cline{5-13}  & & & & & & & & & & & & \\ \hline TOSM & 100 & 200 & 200 & 1000 & 300 & 150 & 300 & 300 & 10\({}^{-3}\) & 10\({}^{-6}\) & 10\({}^{-3}\) & 10\({}^{-3}\) \\ \hline VS & 6000 & 4000 & 4000 & 18000 & 300 & 150 & 300 & 300 & 10\({}^{-3}\) & 10\({}^{-3}\) & 10\The mission-critical communication services account for the safe operation of the Hyperloop.