A Strategy for Checking Timing Constraint Violation in Wireless Sensor Networks Jaecheol Kim, Juil Kim, Woojin Lee, and Kiwon Chong Department of Computing Soongsil University Sangdo-5Dong, Dongjak-Gu, Seoul KOREA jckim@hannaeng.co.kr, {sespop, bluewj, chong}@ssu.ac.kr Abstract: - This paper proposes a strategy for checking timing constraint violation in wireless sensor networks. We present the process for checking timing constraint violation and the techniques for calculation of clock drift, collection of sending and receiving time, and calculation of data transfer time. Through the techniques of this paper, the user can know about data transfer time on each node and total data transfer time from a sensor node to the server. Then, the user can confirm whether the expected data transfer time is satisfied by analyzing the information. If the expected data transfer time is not satisfied in the sensor network, the user can find out where the delay has occurred. Real-time data processing is a key factor in sensor networks, so the sensing data should be transferred to the server in right time in order to perform the correct action at proper time. The proposed strategy will help the user to maintain correct real-time processing in the sensor network because the user can debug timing constraint violation. Key-Words: - debugging, timing constraint, violation checking, sensor networks 1 Introduction According to the advancement in wireless communications and electronics, low-cost, low-power, multifunctional sensor nodes have been developed. These tiny sensor nodes are composed of sensing, data processing, and communicating components, so they can make sensor network [1]. A sensor network [2, 3] is a wireless network which is composed of a large number of lightweight, low-powered sensor nodes. The sensor networks can be used for various application areas such as health, military, home, and environment monitoring. Real-time data processing is a key factor in sensor networks. To perform the correct action at proper time, the sensing data should be transferred to the server in time. Accordingly, it is very important to confirm whether the nodes in a sensor network transmit the sensing data to the server in right time. In this paper, we propose a strategy for checking timing constraint violation in wireless sensor networks. Section 2 describes the process for checking timing constraint violation. We propose the techniques for performing each step in the proposed process in section 3. We discuss the techniques for calculation of clock drift, collection of sending and receiving time, and calculation of data transfer time. We conclude, and present future works in section 4. 2 The Process for Checking Timing Constraint Violation Figure 1 presents the overall process for checking timing constraint violation in the sensor network. Calculate clock drift Step1 Calculate clock drift Step1 Collect sending and receiving time Step2 Collect sending and receiving time Step2 Calculate data transfer time Step3 Calculate data transfer time Step3 Analyze data transfer delay Step4 Analyze data transfer delay Step4 Fig.1. The process for checking timing constraint violation In step 1, clock drift of each node in the sensor network is calculated. Each node uses its own timer, so clock drift between nodes can be occurred. To calculate correct data transfer time, it is necessary to know clock drift of each node. The clock drift of each node is calculated on the basis of server clock. In step 2, sending and receiving time of data packets are collected. To transfer a data packet from a sensor node to the server, several nodes should send and receive the packet because there are a lot of nodes in the sensor network. It is necessary to collect sending and receiving time of a data packet on each node in order Proceedings of the 6th WSEAS International Conference on Applied Computer Science, Hangzhou, China, April 15-17, 2007 553