## 3 Design of the Communication Networks  
The design of the communications networks necessary for the operation of the Hyperloop capsules is similar to that of modern high-speed and metropolitan railways that operate in an automated way [12; 13]. The wireless communication systems of HSR, intercity railway, subway, light rail, and other rail traffic are deployed with various wireless standards [5; 14]. To ensure safe and reliable operation of railways, these wireless standards have to be reliable and robust. In addition, due to the ultra-high operation speed, extremely low end-to-end delay and handover delay are required for operational services transmission, such as train location information. Typically, advanced HST and metros use two separate networks, one for critical communications that are used to control trains and a second network that is used for operating aid and passengers [15]. All of these communications are T2I (Train to Infrastructure), T2P (Train to Passengers), although in the last few years, some metros have implemented T2T (Train to Train) communications to perform train convoys [16]. Hyperloop capsules will communicate with multiple entities using wireless communication systems and local area network (LAN) infrastructure. Adopting a similar concept of V2X (Vehicle-to-everything), a C2X (Capsule-to-everything) communication framework will provide the backbone for passing information from capsule to any entity that may affect the capsule and vice versa. This capsule communication system incorporates other more specific types of communications such as C2I (capsule-to-Infrastructure), C2G (Capsule-to-Grid), C2P (Capsule-to-Passenger), C2C (Capsule-to-Capsule), and C2N (Capsule-to-Network). C2X can be supported by the underlying communication technologies such as WLAN (Wi-Fi 6) and cellular fifth-generation new radio (5G NR). On Table 2 we summarise this communications. Traditionally, critical communications in HST use a European Railway Traffic Management System (ERTMS) [17] for train control and monitoring, and it is composed of Global System for Mobile Communications-Railway (GSM-R) that contains both a voice communication network between driving vehicles, line controller, and a bearer path for European Train Control System (ETCS) data. Existing rail communication systems include the nearing obsolescent GSM-R and a replacement for the FRMCS (Future Railway Mobile Communications System) [18] based on 5G NR technology. Nevertheless, this new standard limits their support to trains traveling at 600 km/h or less, but it's important for HST because it provides interoperability between trains of different countries. For urban transit rail systems, WLAN based on IEEE 802.11 xx is currently a prevalent choice due to the available commercial-off-the-shelf equipment. However, WLANs are not specifically designed for high mobility scenarios and there are some problems for WLAN-based Communications-Based Train Control (CETC) systems such as handoff and QoS issues [19]. The 38 GHz millimeter Wave (mmW) wireless communication technology is applied in the Shanghai Maglev system [20]. The 38 GHz mmW system could provide a capacity that reaches up to 100 Mbps, but also ensure a delay of less than 5 ms and the Bit Error Rate (BER) of safe-related data transmission on the order of \(10^{-5}\). \begin{table}
\begin{tabular}{c c c} \hline
**Communications** & **Network** & **Service** \\ \hline Capsule to Grid (C2G) & WLAN & Critical and Performance Control \\ Capsule to Passengers (C2P) & WLAN + 5G & Business/Performance \\ Capsule to Centralized Network (C2N) & WLAN + 5G & Performance \\ Capsule to Capsule (C2C) & WLAN & Critical \\ Capsule to Infrastructure (C2I) & WLAN & Critical and Performance Control \\ \hline \end{tabular}
\end{table} 
Table 2: Types of communications used on the Hyperloop system: Capsule to everything. The mmW communication system is also a candidate for the system offering high-speed communication services in HSR.