CrossTrace: Privacy-Aware Cross-System Trajectory Recovery via Hybrid Split and Federated Learning
Zijian Cao, Dong Yang Zhao, Qiyue Wang, Haitao Yuan, Huadóng Ma, Shui Yu · IEEE Transactions on Mobile Computing · 2025
Massive urban-scale vehicle trajectories benefit various downstream applications. However, trajectories collected from existing sensing systems are often incomplete, necessitating the recovery of coarse-grained trajectories. Considering that mobility knowledge learned from a single system is less representative of all vehicles or covers only partial road segments, it becomes essential to combine diverse data from multiple systems to support trajectory recovery. Therefore, we learn the impacts of mobility intentions and dynamic traffic conditions on the movement of vehicles from trajectories aggregated across different systems to recover their travel routes on unobservable road intersections. Nonetheless, aggregating raw data across multiple systems raises privacy concerns. This data isolation compounds challenges in acquiring comprehensive mobility intentions and traffic conditions, thereby impairing recovery performance. In this paper, we proposeCrossTrace, a two-stage framework for privacy-aware cross-system trajectory recovery: in theTraffic Condition Inferencestage, a Split Learning pipeline with a multi-view graph neural network is utilized to infer complete traffic conditions for all road segments; in theTrajectory Recoverystage, a Federated Learning pipeline with dedicated modules is utilized to recover missing points by fusing inferred traffic conditions and mobility intentions. Extensive experiments on two large-scale trajectory datasets demonstrate thatCrossTraceoutperforms all alternative schemes.