REPLAY: Modeling Time-Varying Temporal Regularities of Human Mobility for Location Prediction over Sparse Trajectories
This work addresses location prediction for users with sparse mobility data, offering a novel method to model time-varying patterns, though it is incremental in enhancing existing RNN-based approaches.
The paper tackles the problem of location prediction from sparse mobility traces by addressing the limitation of existing distance-based methods in capturing time-varying temporal regularities, such as more regular patterns in the morning. It proposes REPLAY, an RNN architecture that incorporates smoothed timestamp embeddings, achieving a 7.7%-10.5% improvement over state-of-the-art methods on real-world datasets.
Location prediction forecasts a user's location based on historical user mobility traces. To tackle the intrinsic sparsity issue of real-world user mobility traces, spatiotemporal contexts have been shown as significantly useful. Existing solutions mostly incorporate spatiotemporal distances between locations in mobility traces, either by feeding them as additional inputs to Recurrent Neural Networks (RNNs) or by using them to search for informative past hidden states for prediction. However, such distance-based methods fail to capture the time-varying temporal regularities of human mobility, where human mobility is often more regular in the morning than in other periods, for example; this suggests the usefulness of the actual timestamps besides the temporal distances. Against this background, we propose REPLAY, a general RNN architecture learning to capture the time-varying temporal regularities for location prediction. Specifically, REPLAY not only resorts to the spatiotemporal distances in sparse trajectories to search for the informative past hidden states, but also accommodates the time-varying temporal regularities by incorporating smoothed timestamp embeddings using Gaussian weighted averaging with timestamp-specific learnable bandwidths, which can flexibly adapt to the temporal regularities of different strengths across different timestamps. Our extensive evaluation compares REPLAY against a sizable collection of state-of-the-art techniques on two real-world datasets. Results show that REPLAY consistently and significantly outperforms state-of-the-art methods by 7.7\%-10.5\% in the location prediction task, and the bandwidths reveal interesting patterns of the time-varying temporal regularities.