Keywords
Signal fading
Multipath effect
Sensor fusion
Railway communications
Submitted : 2026-03-04
Accepted : 2026-03-19
Published : 2026-04-03
Abstract
Accurate and reliable train positioning is a fundamental requirement for modern rail transit signal systems. This requirement faces particular challenges in tunnel environments, as wireless signals are severely affected by multipath fading, shadowing effects, and attenuation. This study systematically analyzed the impact of specific fading phenomena in tunnel environments on positioning accuracy through ray-tracing simulations and random channel modeling. We simulated typical urban subway tunnel environments and evaluated the performance of positioning technologies such as received signal strength indication, arrival time, and carrier phase in damaged channels. The results showed that signal fading could cause positioning errors ranging from several meters to several tens of meters, and the error distribution was closely related to the type of fading, tunnel cross-section, and algorithm robustness. Deep fading would lead to local failure of positioning capabilities, while shadow fading would cause systematic deviations. To address these challenges, the study proposed comprehensive strategies, such as using inertial navigation units for multi-sensor fusion, deploying distributed antenna systems, and applying advanced channel estimation and filtering algorithms. Only through the organic combination of physical layer redundancy, intelligent infrastructure, and advanced data processing can high-integrity positioning required for safety-critical applications in tunnel environments be achieved, ensuring the safety and efficiency of underground rail transit operations.
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