Field Benchmarking of IEEE 802.11p and LTE-V2X for Degraded-Mode Train-to-Train Communication in Open and GNSS-Denied Railway Environments

Direct train-to-train (T2T) communication can provide a fallback safety link when railway trackside infrastructure becomes unavailable or degraded. This paper presents a field benchmark of two commercially available vehicle-to-everything technologies, IEEE 802.11p and LTE-V2X, for railway T2T communication under infrastructure-limited conditions. The evaluation was conducted on a full-scale railway testbed in Korea and covered open-track and tunnel environments, stationary and controlled mobile operation, and omnidirectional and directional antenna configurations. Mobile tests were limited to 20 km/h to emulate degraded-mode operation and maintain repeatable inter-train separation. The results show that antenna configuration is a dominant design factor. In open line-of-sight sections, LTE-V2X with omnidirectional antennas outperformed IEEE 802.11p with omnidirectional antennas, whereas both systems achieved reliable operation with directional antennas over the measured open-track range. In tunnel and global navigation satellite system (GNSS)-denied conditions, however, IEEE 802.11p was more robust: with directional antennas, it maintained near-zero packet error rate across the measured tunnel distances, while LTE-V2X exhibited a baseline packet error rate of about 0.1 because of synchronization interruptions associated with roadside unit (RSU)-assisted operation. In long-range stationary tests, IEEE 802.11p with directional antennas maintained zero packet error rate up to 3800 m, whereas LTE-V2X degraded abruptly beyond 2600 m. Latency was also substantially lower and more stable for IEEE 802.11p. These results should be interpreted as a two-train, single-link benchmark for degraded-mode railway operation, not as a validation of dense multi-train or full-speed commercial service.