Cross-layer sensor network synchronization

Traditional network synchronization assumes perfect physical-layer (PHY) timing. However, the operating environment of wireless sensor networks is quite challenging to warrant perfect PHY timing. To account for PHY timing errors, we pursue a joint PHY/network-layer synchronization approach. At the PHY, we adopt a timing synchronization scheme that offers cost-effective wireless ad hoc access. The variance expression of this synchronizer is derived to shed light on its deviation from the ideal timestamps involved in a network timing protocol. This variance also motivates altering the random medium access control to effect a new network-level timing protocol based on time-stamp broadcast synchronization (TSBS), capable of attaining accurate clock synchronization with low energy consumption. Our design and analysis account for cross-layer issues in synchronizing practical wireless sensor networks.