Time Synchronization in Wireless Sensor Networks: Estimating Packet Delay Shiu Kumar 1,* , Yeonwoo Lee 2 , and Seong Ro Lee 1 1 Department of Information Electronics Engineering, Mokpo National University 2 Dept. of Information and Communication Engineering, Mokpo National University shiu748@gmail.com, ylee@mokpo.ac.kr, srlee@mokpo.ac.kr Abstract. A significant challenge when implementing time synchronization protocols is minimizing timestamp uncertainties. The major problem of time synchronization is not only that this packet delay exists, but also being able to predict the time spent on each can be difficult. This paper aims to reduce these uncertainties by estimating them in the transmitter and receiver thus greatly increasing the performance of the time synchronization technique. Keywords: Time synchronization, packet delay, timestamp 1 Introduction Wireless sensor networks have drawn much attention from the academia to the industry in recent years [1] due to changes in electronics and communication technologies, and are becoming an increasingly popular research topic. Low cost, multi-functionality, small size and mobility are the advantageous characteristics of WSN that make it suitable for applications such as health monitoring [2], agriculture [3], surveillance [4], etc. Synchronization is typically based on some sort of message exchange among sensor nodes. However, these message exchanges that take place during synchronization are subject to numerous delays. Such latency depends on the amount of time taken from the moment when the sender timer is read to the instant when the receiver timer is updated. The total latency in terms of end-to-end single-hop transmission includes the following terms: send time, access time, propagation time and receive time. The RBS protocol is based on the receiver-receiver synchronization method that synchronizes a cluster of wireless sensors within transmission range of the reference sensor node [5]. TPSN [6] is a timing synchronization algorithm for sensor networks based on the sender-receiver synchronization comprising of two phases: level discovery phase and synchronization phase. To mention, a few other time synchronization methods reported are Pairwise Broadcast Synchronization, Pairwise Lightweight Protocol, and Flooding Time Synchronization Protocol. ICCA 2013, ASTL Vol. 24, pp. 68 - 71, 2013 © SERSC 2013 68