## 1 Introduction
Moreover, the deployment environment of CDL usually refers to a line-of-sight (LOS) scenario without any reflected radio waves, whereas the closed propagation environment will lead to a severe multipath effect. To our best knowledge, little research on the communication issue has been conducted, among which our team has performed a series of systematic works. In [13], [PERSON] summarized the challenges as well as communication quality-of-service (QoS) quantitatively and proposed a leaky waveguide solution for wireless coverage. In [14], we proposed two novel structures to reduce the Doppler effect using the distributed antenna system (DAS) method. In [15], [PERSON] performed a series of work on the wireless channel analysis, including Doppler shift, power delay spectrum, and multi-input and multi-output (MIMO) capacity, in the vacuum tube scenarios based on the propagation-graph channel modelling theory. However, [14] lacks a channel modelling-based simulation result, and [15] neglects the large-scale characterization, especially in terms of the path loss. As such, we adopt the two-slope path loss model to depict its attenuation trend in this paper. Moreover, the radio coverage analysis of both DAS and leaky waveguide system (LWS) is performed and the corresponding handover judgment conditions are presented herein. In terms of the network architecture, literature [16] and [17] proposed a novel baseband unit-to-remote radio unit (BBU-RRU) mapping relationship in the criss-cross railway lines for HSRs and presented an optimal baseband units (BBUs) pool selection algorithm. This scheme dedicated to the Hyperloop leads to a high equipment expenditure. Thereby, we apply this scheme in the 5G network architecture for the Hyperloop. Moreover, the trackside CUs can also provide services for public mobile cellular communication in the vicinity, indicating a full use of resources when no vactrain runs inside this cell. As for the physical resources management (mainly referring to the physical resource of time and frequency domain), the ultra-reliable and low latency communication (uRLLC) in 5G can satisfy the demands of those latency-sensitive communication services by using the flexible numerology [18]. Therefore, the multiplexing of uRLLC and enhanced mobile broadband (eMBB) traffic attracts extensive attention [19; 20; 21]. Different from the conventional multiplexing idea, i.e., puncturing the eMBB physical resource block (PRB) in the next mini-slot of the arriving time, we consider the unique required latency of each uRLLC traffic and propose a flexible multiplexing scheme. In our proposal, each uRLLC traffic is assigned to a PRB position within its maximum tolerable latency. A heuristic algorithm is employed to solve the optimization problem considering maximizing the eMBB throughput and minimizing the uRLLC power. With regards to the passengers Internet resource management, the cache-based algorithm can yield not only a high throughput but also a low transmission latency [22; 23]. Herein, we employ the cache in trackside active antenna unit (AAU) and formulate two resource management schemes by using the predictable vactrain trajectory, which can result in a higher throughput performance than the conventional cache-based scheme. Although the cache-based prefetching idea for the HSRs has been explained in our previous work [24], we formulate another resource management scheme dedicated to the video surveillance data, i.e., post-uploading scheme. These works provide some insights into the design of the communication system, but also with some limitations, e.g., focusing only on parts of the communication procedure. As such, we aim to propose a wireless communication solution that can provide a reliable connection train-to-ground link from several important communication procedures. Moreover, it should be compatible with existing public mobile cellular communication systems not only to reduce the equipment expenditure but also to use mature and low-cost off-the-shelf technologies based on the previous work.