Gradient clock synchronization in wireless sensor networks

TLDR

Accurately synchronized clocks are crucial for many sensor‑network applications, yet existing algorithms often leave close‑by nodes poorly synchronized. The authors propose the Gradient Time Synchronization Protocol (GTSP) to achieve accurate synchronization between neighboring nodes. GTSP is a fully decentralized protocol where each node periodically broadcasts its time, calibrates its logical clock using neighbor messages, requires no tree or reference node, and is implemented on Mica2 with TinyOS. Evaluation on a 20‑node testbed and simulations on larger topologies demonstrates GTSP’s effectiveness.

Abstract

Accurately synchronized clocks are crucial for many applications in sensor networks. Existing time synchronization algorithms provide on average good synchronization between arbitrary nodes, however, as we show in this paper, close-by nodes in a network may be synchronized poorly. We propose the Gradient Time Synchronization Protocol (GTSP) which is designed to provide accurately synchronized clocks between neighbors. GTSP works in a completely decentralized fashion: Every node periodically broadcasts its time information. Synchronization messages received from direct neighbors are used to calibrate the logical clock. The algorithm requires neither a tree topology nor a reference node, which makes it robust against link and node failures. The protocol is implemented on the Mica2 platform using TinyOS. We present an evaluation of GTSP on a 20-node testbed setup and simulations on larger network topologies.