## 2 Communication Requirements  
The Hyperloop Transportation Technologies (HyperloopTT) system (Figure 1) follows three phases of development. In the first phase, a 320 m-long test track has been built with the basic functional characteristics to allow technological tests to be carried out. This facility has been built in Toulouse, France. Simultaneously, a commercial line will be built with a length of 5 km with speeds reach beyond 600 km/h. This line will allow the certification and validation of the technologies developed at high speed and will be able to enter into commercial exploitation with hundreds of kilometer of infrastructure interconnecting towns, cities, and ports. A fully autonomous and connected Hyperloop will require a robust, scalable, reliable network architecture to provide the transfer and flow of critical, performance and business data required on HST [9] using communications services from the internet and mobile service providers to and from the Operation Control Centre (OCC) to capsule, station, and infrastructure (Figure 2). To properly perform Hyperloop communications functions, many different elements of Hyperloop must be interconnected through digital buses or ethernet switches. The following classification of communication-based services are built taking in mind different stakeholders, the criticality/nature of these services, and their end-users:  
* Critical applications: Continuous data dumping Safety Integrity Level (SIL 4). * Performance applications: Semi-continuous data dumping (SIL 2). * Business applications: Sporadic data dumping (SIL 1). **Critical Communication Applications**: cover all aspects needed for the proper operation of the Hyperloop service. These are mission-critical and safety-related, whereby information generated by these applications must be shared by different stakeholders (e.g., transportation operator and infrastructure operator). This group of systems requires the maximum Safety Integrity Level (i.e., SIL 4 [10]) to minimize the risk associated with the equipment failure. The bandwidth required is low (less than 10 Mbps per capsule) because the information transmitted is capsule position, speed, and movement authorizations. The most important in this case is extremely significant delay requirements: less than 5 ms delay and less than 1 ms jitter in the worst case. These types of communications usually use UDP packets without retransmissions to minimize jitter and because the signalling information has temporal caducity. **Performance Communication Applications**: include all applications necessary to improve capsule operation and are very similar to advanced HST communications [6]. These applications will be considered SIL 2 because the security of the capsule does not rely on them. Most important for this application is the on-board 4K real-time video  
Figure 1: Hyperloop TT system. Figure 2: Hyperloop TT connected architecture. surveillance (CCTV) supporting automatic driving. Video surveillance for the area in front, rear, and inside the capsule is needed to improve operation and security of the passengers and to allow automatic driving. In some ways, CCTV could be considered to be a critical application (SIL 4), but, in this case, it will be very difficult (nearly impossible) to fulfill the delay requirements of the critical communications system, so that they usually are treated as SIL 2. Other performance services are capsule diagnostics and monitoring and passenger information in addition to some basic internet services for the passengers like instantaneous messenger, email, and voice calls that can improve the performance of the capsule and the comfort of the passengers. Considering all these services, the data rate required is around 100 Mbps with a short delay (<10 ms) and using different wireless communications networks, one for the Hyperloop services and another for the passenger's performance services.