Hyperloop Communications: Intra-Tube Channel Capacity and its Enhancement

Hyperloop is a futuristic transfortation system to carry passengers and frieght in the vehicle called 'pod', which travels at the speed of 1,200 km/h within a near-vacuum 'tube'. To ensure safety and to provide Internet connectivity to passengers, wireless communications is an essential building block whose development necessitates evaluating and enhancing intra-tube wireless channel capacity. In this regard, this paper presents an in-depth investigation of per-pod downlink channel capacity, leveraging our previously-developed novel evaluation methodology on intra-tube electromagnetic (EM) propagation characteristics. Specifically, we first show that metallic pods (as considered in most Hyperloop proposals) cannot satisfy the per-passenger capacity requirement for on-board Internet service. As a remedy, we propose a double-layered pod structure to enhance the channel capacity, consisting of an EM absorbing outer layer and a metallic inner layer enclosing the passenger cabin. Our intensive evaluations revealed that double-layered pods achieve per-pod channel capacity large enough to support 4K UHD video streaming for all the passengers, thanks to the outer layer absorbing the power of interference signals. Furthermore, we present how to maximize the channel capacity via an optimized thickness of the EM absorbing layer and the choice of the best EM mode for communications.