The paper presents the Timing-sync Protocol for Sensor Networks (TPSN), a novel approach to time synchronization in wireless ad-hoc sensor networks. TPSN aims to provide network-wide time synchronization by establishing a hierarchical structure and performing pairwise synchronization along the edges of this structure. The algorithm is designed to be scalable and energy-efficient, suitable for the dense and resource-constrained nature of sensor networks. The authors compare TPSN with Reference Broadcast Synchronization (RBS), showing that TPSN achieves an average accuracy of less than 20 μs between neighboring motes, compared to RBS, which has a worst-case accuracy of around 50 μs. TPSN is also evaluated over small multihop networks and large-scale simulations, demonstrating its scalability and robustness. The paper discusses the contributions, system model, error analysis, and implementation details, including modifications to the Berkeley Motes to support TPSN. The results highlight the effectiveness of TPSN in providing accurate and efficient time synchronization for sensor networks.The paper presents the Timing-sync Protocol for Sensor Networks (TPSN), a novel approach to time synchronization in wireless ad-hoc sensor networks. TPSN aims to provide network-wide time synchronization by establishing a hierarchical structure and performing pairwise synchronization along the edges of this structure. The algorithm is designed to be scalable and energy-efficient, suitable for the dense and resource-constrained nature of sensor networks. The authors compare TPSN with Reference Broadcast Synchronization (RBS), showing that TPSN achieves an average accuracy of less than 20 μs between neighboring motes, compared to RBS, which has a worst-case accuracy of around 50 μs. TPSN is also evaluated over small multihop networks and large-scale simulations, demonstrating its scalability and robustness. The paper discusses the contributions, system model, error analysis, and implementation details, including modifications to the Berkeley Motes to support TPSN. The results highlight the effectiveness of TPSN in providing accurate and efficient time synchronization for sensor networks.