Hindawi Publishing Corporation ISRN Sensor Networks Volume 2013, Article ID 941489, 12 pages http://dx.doi.org/10.1155/2013/941489 Research Article Faulty Sensor Node Detection Using Round Trip Time and Discrete Paths in WSNs R. N. Duche and N. P. Sarwade Electrical Engineering Department, Veermata Jijabai Technological Institute, Matunga, Mumbai 400019, India Correspondence should be addressed to N. P. Sarwade; nishasarvade@vjti.org.in Received 16 July 2013; Accepted 18 August 2013 Academic Editors: Y.-C. Wang and Y. Yu Copyright © 2013 R. N. Duche and N. P. Sarwade. Tis is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Wireless sensor networks (WSNs) with efcient and accurate design to increase the quality of service (QoS) have become a hot area of research. Implementing the efcient and accurate WSNs requires deployment of the large numbers of portable sensor nodes in the feld. Te quality of service of such networks is afected by lifetime and failure of sensor node. In order to improve the quality of service, the data from faulty sensor nodes has to be ignored or discarded in the decision-making process. Hence, detection of faulty sensor node is of prime importance. In the proposed method, discrete round trip paths (RTPs) are compared on the basis of round trip delay (RTD) time to detect the faulty sensor node. RTD protocol is implemented in NS2 sofware. WSNs with circular topology are simulated to determine the RTD time of discrete RTPs. Scalability of the proposed method is verifed by simulating the WSNs with various sensor nodes. 1. Introduction Wireless sensor networks (WSNs) consist of portable sensor nodes distributed in the feld according to the requirement of specifc application. WSNs with large numbers of sen- sor nodes found applications in the area of environmental monitoring, military operations, smart homes, surveillance, industries, and hospitals [1, 2]. In most of the applications, portable sensor nodes are placed randomly. If a sensor node deployed in the feld becomes faulty, dead, or malfunction, then the resultant processed value will deviate from the mean and can lead to inaccurate analysis [3, 4]. Sensor node in the feld can become faulty due to various reasons such as battery failure, hardware or sofware failure, and wireless device problem. Lifetime of WSNs is afected due to failure in portable sensor nodes [5, 6]. Tis will degrade the quality of service (QoS) of WSNs. Hence, fault detection becomes a critical issue in WSNs. Designing the efcient fault detection method to reduce the detection time as well as energy consumed by sensor node during fault detection is a need of time. Faulty sensor nodes in WSNs can be neglected or discarded during the decision making to achieve the accuracy in detection [7, 8]. Jiang [9] has suggested the fault detection based on neighbor nodes data analysis. In this method, fault detection accuracy will decrease rapidly if the numbers of neighbor nodes to be diagnosed are small and the node’s failure ratio is high. Confdence factor measurement based neighbor data analysis proposed by Zhipeng et al. [10] to detect the faulty node has limitations due to the weak and inaccurate algorithm. In [11], link failure detection based on monitoring cycles (MCs) and monitoring paths (MPs) is presented. Tree-edge connectivity in the network, separate wavelength for each monitoring cycle (MC), and monitoring locations are the limitations of this method. Time delay based direction of arrival (DOA) estimation to detect and compensate failure of one sensor in an array is suggested in [12]. Te performance of DOA estimation is limited due to quantization error, wave fronts are not perfectly planar, and source movements. Te diferent failure detection approaches in WSNs are centralized, distributed, and clustering [1]. We have used the discrete clustering approach to detect the faulty sensor node. Detection of fault is based on inspecting the discrete RTPs for their round trip delay (RTD) time. Few RTPs are analyzed during fault detection; therefore involvement of sensor node in investigating the fault is rare. Tis will improve the lifetime