Efficient Decentralized Context Sharing via Smart Aggregation

Sensing applications often require participants to share context information about the physical social, or network environment in which they operate. Building shared views of context requires exchanging sensed information, often via peer-to-peer links. In-network aggregation enables efficient distributed data collection, but the goal has been almost exclusively collect a single aggregate value at a single sink node. In contrast, we design and implement a simple protocol for exchanging context information in aggregate in a peer-to-peer fashion, where every node needs to acquire a shared view of the aggregate context. In our protocol, when a node receives new context information from a neighboring node, it aggregates the new information into its local view of the shared state of the world which it then subsequently shares with its neighbors. We demonstrate (both theoretically and empirically) the situations in which participants´ raw context information is fully or partially recoverable by other participants from an aggregate and quantify the tradeoffs in communication overhead for the quality of shared context knowledge. Compared with non-aggregation communication for sharing context values among 100 nodes in a simulated network, we show an overhead savings of at least 78.0%, and an overhead savings of 66.0% with 99.8% average accuracy in a 54 node emulated network driven by real world data.