  Providing high-capacity radio connectivity for high-speed trains (HSTs) is
one of the most important use cases of emerging 5G New Radio (NR) networks. In
this article, we show that 5G NR technology can also facilitate high-accuracy
continuous localization and tracking of HSTs. Furthermore, we describe and
demonstrate how the NR network can utilize the continuous location information
for efficient beam-management and beamforming, as well as for downlink Doppler
precompensation in the single-frequency network context. Additionally, with
particular focus on millimeter wave networks, novel concepts for low-latency
intercarrier interference (ICI) estimation and compensation, due to residual
Doppler and oscillator phase noise, are described and demonstrated. The
provided numerical results at 30 GHz operating band show that sub-meter
positioning and sub-degree beam-direction accuracies can be obtained with very
high probabilities in the order of 95-99%. The results also show that the
described Doppler precompensation and ICI estimation and cancellation methods
substantially improve the throughput of the single-frequency HST network.
