John Heidemann

Low-latency Synchronization of Loosely-coupled Sensornet Republishing

TitleLow-latency Synchronization of Loosely-coupled Sensornet Republishing
Publication TypeTechnical Report
Year of Publication2009
AuthorsU. Park, and J. Heidemann
Date Publishedapr

Today many individual deployments of sensornets are successful, but they will have much greater impact when, rather than standing alone, they share data across deployments so each can build upon the others. We expect data to be shared over the Internet, and as the number of processing and reprocessing steps grows, \emphtimely data synchronization is increasingly important. Today, such sharing is often hard-coded or driven by fixed-interval polling. Fixed-interval polling can provide poor worst-case performance (mean latency approaching the data generation period), and best performance requires careful manual configuration of both poll period and phase. We instead propose \emphData Generation Tracking (DGT), a new family of adaptive polling algorithms that \emphlearn and predict good times to pull data to minimize both latency and unfruitful queries. Our approach avoids manual configuration and automatically adapts to outages and changes in data generation rate. To evaluate our work, we examine four sensornet deployments and develop a rough \emphmodel of sensornet data generation. We then use this model and replay of real traces to evaluate DGT, finding that, depending on application, its median latency is only 10–30% of that of fixed-interval polling, with a configurable rate of network load that is the same or slightly higher.