International Journal of Advanced Science and Technology Vol.77 (2015), pp.37-48 http://dx.doi.org/10.14257/ijast.2015.77.04 ISSN: 2005-4238 IJAST Copyright ⓒ 2015 SERSC Impact of using Mobile Sink on Hierarchical Routing Protocols for Wireless Sensor Networks Ahmed Salim 1 , Asmaa Ahmed Badran 2 1 Math. Dept., Fac. of Sci., Univ. of Zagazig, Zagazig, P. O. Box 44519, Egypt Math. Dept. Fac. of Sci. and Arts, Al-mithnab, Qassim Univ., P. O. Box 931, Buridah 51931, Al-mithnab, Kingdom of Saudi Arabia 2 Math. Dept. Univ. of Zagazig, Zagazig, Egypt 1 a.salim@zu.edu.eg, 2 asmaa.ahmedbadran@gmail.com Abstract Wireless sensor networks (WSNs) are composed of many low cost, low power devices with sensing, local processing and wireless communication capabilities. In these networks energy constraint is very important. Routing protocols form one of the most important communication paradigms that greatly affect the performance of the wireless sensor networks. In this paper, we compare the performances of six hierarchical based routing protocols when mobile sink is used. We perform analytical simulations in terms of network lifetime and average energy consumption. Keywords: wireless sensor networks, hierarchical routing protocols, static sink, mobile sink 1. Introduction WSNs are consisting of a large number of sensor nodes that transform physical data into a form that would make it easier for the user to understand [1]. The naive approach to collect data from sensor nodes is direct one where each sensor node transmits the data directly to the sink which is located far away. The cost of data transmission from each sensor node to the sink is very high, thus nodes die quickly and hence reducing the lifetime of the network. Therefore, use a few transmissions as possible leads to efficient energy utilization. Routing protocols from one of the most important communication paradigms that greatly affect the performance of the wireless sensor networks; so that designing routing protocols for sensor networks is a vital aspect. In earlier research, static sink is used to gather data in WSNs. However, if the sink is able to move, sensors can communicate with the sink when it is near to them, and so hop by hop delivery path of data becomes shorter. Mobile sink even can move close to nodes when the nodes’ power is reduced. So the set of nodes near the mobile sink can change, which provide more balance of energy and as a result, network lifetime can increase [2]. The use of mobile sink in WSNs introduces some complications, such as detecting and tracking sink location to ensuring reliable data transfer between sensor nodes and the mobiles sink, and managing sensor nodes to support sink mobility [3, 17]. In this paper, our goal is to adding the concept of sink mobility in the hierarchical chain based routing protocols, like, PEGASIS [5], PEGASIS-E [8], COSEN [10], ECBSN [11], IECBSN [12], and EAPHRN [13], and then compare the performance of these protocols in terms of network life time and average energy consumption. The rest of the paper is organized as follows: Section 2 briefly reviews related work. In Section 3, we introduce