Multi-Horizon Delay Asymmetry Prediction and Compensation for IEEE 1588 Precision Time Protocol on Copper and Fiber Links by Means of Ground-Truth Measurements.

IEEE 1588 Precision Time Protocol (PTP) synchronization accuracy is degraded by delay asymmetry in physical links. Accurate prediction and compensation of this asymmetry are essential for high-precision timekeeping. This paper presents a multi-horizon delay asymmetry prediction framework validated on a cesium-referenced testbed. The experimental platform integrates a cesium atomic clock (frequency stability <5×10-12), a Syncedge C10 PTP analyzer, and an RK3568 embedded TimeReceiver, providing hardware-timestamped ground-truth measurements over 24 h periods on both copper and fiber links under real operating conditions. A unified multi-output encoder architecture is compared against per-horizon recurrent models and classical baselines to predict delay asymmetry at five future horizons (h∈{1,2,4,8,16}, corresponding to 0.125-2.0 s ahead). On copper links at an 8 s observation window, the unified model achieves a mean absolute error of 2.15 ns and an R2 of 0.714 at the nearest horizon, statistically tied with the best per-horizon model (2.16 ns, R2=0.713) while using 1.9-6.1× fewer total parameters (655 K vs. 1.2-4.0M). On fiber links, all models achieve comparable accuracy with an MAE of 2.16-2.18 ns. The method requires ground-truth labels from a calibrated 1PPS or cesium reference; both training and inference require the same physical link and environmental conditions. Generalization to other settings remains untested.