doi:10.1109/MWC.2011.5714029engMarco, A.Casas, R.Sevillano, J.L.Coarasa, V.Asensio, A.Obaidat, M.S.Synchronization of Multi-hop Wireless Sensor Networks at the Application layerART-2011-68185Time synchronization is a key issue in wireless sensor networks; timestamping collected data, tasks scheduling, and efficient communications are just some applications. From all the existing techniques to achieve synchronization, those based on precisely time-stamping sync messages are the most accurate. However, working with standard protocols such as Bluetooth or ZigBee usually prevents the user from accessing lower layers and consequently reduces accuracy. A receiver-to-receiver schema improves timestamping performance because it eliminates the largest non-deterministic error at the sender's side: the medium access time. Nevertheless, utilization of existing methods in multihop networks is not feasible since the amount of extra traffic required is excessive. In this article, we present a method that allows accurate synchronization of large multihop networks, working at the application layer while keeping the message exchange to a minimum. Through an extensive experimental study, we evaluate the protocol’s performance and discuss the factors that influence synchronization accuracy the most.2011http://zaguan.unizar.es/record/13091110.1109/MWC.2011.5714029http://zaguan.unizar.es/record/130911oai:zaguan.unizar.es:130911info:eu-repo/grantAgreement/EC/FP6/035147/EU/Mainstreaming on ambient intelligence/MONAMIinfo:eu-repo/grantAgreement/ES/MCYT/TIN2006-15617-C03IEEE WIRELESS COMMUNICATIONS 18, 1 (2011), 82-88All rights reservedhttp://www.europeana.eu/rights/rr-f/info:eu-repo/semantics/openAccess