Journal of Communication and Computer 9 (2012) 340-344 Message-Efficient Localization in Mobile Wireless Sensor Networks Javad Rezazadeh, Marjan Moradi and Abdul Samad Ismail Department of Computer Systems and Communication, Universiti Teknologi Malaysia, UTM Skudai 81310,Johor, Malaysia Received: October 12, 2011 / Accepted: October 18, 2009 / Published: March 31, 2012. Abstract: Locations of sensors in wireless sensor networks (WSNs) play a vital role in many applications. Regarding the mobility of the nodes in some of the applications, it is necessary to have a localization algorithm that can support the mobility of nodes. In this paper a demand-based algorithm has been presented which uses information of messages for update their tables so they can help to localize the unknown nodes. This technique suggested method that called ELoc(Efficient Localization) has been able to present a higher speed and range of success, by reducing the sent messages and consequently reducing the energy consumption quite significantly. Key words: Localization message, mobility of sensors, Localization table, mobile sensor networks. 1. Introduction Some applications and protocols, such as tracking and routing, require knowing the place of node in wireless network systems. Because of the random distribution of the nodes, and in some application, the mobility (or the ability to change the place) of the nodes, we need an algorithm for localization. Localization can be performed physically or relatively. In physical localization we need some nodes with known locations which are called guide nodes or beacon. Several researches have been done about localization and other relevant subjects and various algorithms have been proposed. A review of the presented algorithms can be seen at Ref. [1-6]. Most algorithms require an additional hardware. For instance, the methods which are proposed at Ref. [7-12] need hardware to measure the distance. The Marjan Moradi, master research student, research fields: localization, underwater wireless sensor networks, E-mail: marjanmoradi@ieee.org. Abdul Samad Ismail, associate prof. Dr., research fields: networks and communication, E-mail: abdsamad@utm.my. Corresponding author: Javad Rezazadeh, Ph.D. candidate, research fields: mobile and wireless sensor networks, E-mail: rezazadeh@ieee.org. proposed algorithm in Ref. [1], requires hardware to measure the angle, and Ref. [13] needs hardware to measure the range of radio transmission. On the other hand, there are some algorithms that do not require an additional hardware. Although sometimes we have to use GPS, because the physical localization needs some guide nodes, but in order to avoid using that, we can manually place some of the nodes in known locations, these nodes are called guide nodes. In this paper, an algorithm for localization of sensor networks is proposed which supports the mobility of the nodes, and in which each node only through knowing the number of distance hops from the adjacent nodes, which have a valid place, knows its own physical place with a suitable approximation and consuming energy very efficiently. This paper is organized in this way: in Section 2 the problem and the presuppositions are stated and in Section 3 the proposed algorithm is described. In Section 4, the results of the simulation are represented and finally in Section 5 the conclusion is discussed. 2. Problem and Presuppositions Assume, L1, L2 ,…, Lm, Lm + 1, Lm + 2,..., Lm+n DAVID PUBLISHING D