5G networks can not only provide high-quality video entertainment services for passengers on high-speed trains but also offer a reliable and efficient vehicle-to-ground information transmission channel for intelligent operation and maintenance of trains. To achieve 5G coverage inside the train carriages

signal propagation through 5G base stations located alongside the railway tracks is exploited. However

due to significant signal attenuation caused by the metallic body of trains

the above coverage method requires dense deployment of trackside stations and high-power transmission to guarantee adequate signal strength

resulting in high costs for providing 5G services of trains. This paper investigates enhancement schemes of 5G services on high-speed trains by leveraging onboard 5G devices. According to the onboard coverage method and services offloading approach

the enhancement schemes of 5G services can be categorized into four options: customer premise equipment (CPE) combined with edge user plane function (UPF) offloading

onboard Wi-Fi combined with content delivery network (CDN) node offloading

5G small cells onboard combined with edge UPF offloading

and 5G small cells combined with CDN node offloading. This paper provides a detailed description of the technical implementation for each scheme and investigates a comprehensive analysis of the advantages

disadvantages

and technical challenges of the above schemes. Finally

considering the technical challenges of providing 5G services on high-speed trains

recommendations for further practical validation are proposed.