Comments on “High-Speed Train Positioning Using Deep Kalman Filter With 5G NR Signals”

Recently, Ko et al. (2022) proposed a high-speed railway positioning scheme based on an improved Kalman filter using 5G NR signals. Although the proposal was promising, our research and analysis have revealed that the method has serious design flaws in the proposed filtering principles, rendering the algorithm infeasible. Specifically, the flaws are related to the computation and usability of high-order terms in the prediction error after Taylor expansion and prediction error derivation.