This paper presents an approach to designing critical railway voice communication applications, which follows the principles of a service-oriented architecture. It relies on stable connections and innovative services. The digitalization of railways allows for improvements in service reliability, safety, security, and predictability. To accommodate multiple frequency bands with a single antenna, along with the aerodynamic radome cover, design techniques allowing multiple frequency bands are reviewed in this paper. We review recent studies of railway antennas over various frequency bands, such as LTE-R, LTE, and the lower and upper 5G bands. As the communication scheme advances toward 5G technology, high directivity is required for the railway antenna to compensate for the high path loss at high-frequency bands, i.e., 28-GHz band. In a low-frequency band (<5 GHz), railway antennas used to be omnidirectional in the horizontal plane. This paper reviews aerodynamic simulations to account for the drag coefficient of the antenna.
While size constraints on railway antennas are not as critical as for mobile consumer counterparts, a radome structure is required to cover the antenna to minimize the aerodynamic resistance antenna. There are various aspects that one should consider when designing an antenna, such as antenna size and directivity. This paper presents a review of the state-of-the-art antennas for the railway communications.
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