Localization with Enhanced Location Accuracy using RSSI in WSN Abstract— Recent advances in wireless communication, low power sensors and microcontrollers enable the deployment of large-scale wireless sensor networks. A fundamental problem in wireless sensor networks is localization i.e. determination of geographical locations of sensor nodes. This paper addresses the problem of location discovery of the nodes in wireless sensor network. We propose a localization technique by means of which a sensor node can determine its location with enhanced accuracy by listening wireless transmissions from three or more beacons. The proposed method is based on RSSI technique that does not require any additional complexity in construction of the sensor nodes. Performance of the proposed localization scheme is compared with one of the existing schemes. Qualitative analysis is done considering communication, storage and computational overhead as performance metrics, whereas quantitative analysis is done considering localization error as a performance metric. The results confirm our scheme’s supremacy over the competing scheme. Keywords- Wireless sensor network; localization; received signal strength indication; trilateration I. INTRODUCTION Recent advances in wireless communications, coupled with the availability of low power sensors and microcontrollers have evolved a new wide area monitoring paradigm commonly known as wireless sensor networking. Wireless sensor networks (WSNs) [1] allow inexpensive, high quality monitoring of large geographical areas. WSNs are usually implemented as a potentially large number of wireless sensor nodes that communicate over multiple hops to one or more sink(s) or base station(s). The sink processes and transmits the received data to the outside world. Generally nodes are static in wireless sensor network (WSN), while some modern applications require the nodes to be mobile. Determining location of nodes i.e. localization is a fundamental problem for applications in WSN with large number of nodes. Location information in WSNs enables efficient routing, power saving in applications like target tracking, locating the source of the data etc. Manual configuration of locations is not feasible for large-scale network with mobile nodes. Providing each node with localization hardware such as global positioning system (GPS) receiver is not a valid option for such tiny devices as GPS is expensive in terms of cost and energy consumption. A more reasonable solution to the localization problem is to allow some nodes called seeds/beacons to have their location information available at all times, and allow other nodes to inform their locations by exchanging messages with beacons. Localization algorithms can be divided into two categories: range-based or fine-grained and range-free or coarse-grained approach [2]. Range-based approaches normally require accurate distance or angle measurements to compute the location of unknown node. Range-based localization schemes such as Time Difference of Arrival (TDOA) [3], Angle of Arrival (AOA) [4], Radio Interferometric Positioning System (RIPS) [5] and Received Signal Strength Indication (RSSI) [6] rely on extra hardware other than radio transceiver to get accurate measurements. Range-free approaches, on the other hand, normally rely on parameters e.g. proximity information, less accurate distance estimation to infer the location of unknown node. Some of the important localization techniques based on range-free approach are Centroid [7], Multidimensional Scaling Map (MDS-MAP) [8], Amorphous localization algorithm [9]. Many works have been reported so far that deal with the issue of node localization. In one such work [3] A. Savvides et al. have proposed a localization system AHLoS (Ad-Hoc Localization System) based on TDOA. In AHLoS, the beacons periodically broadcast position information over RF and ultrasound signals concurrently. A normal node receives the RF signal earlier than the ultrasound signal and based on this time difference it measures the distance of the beacon. The measurements may not be accurate due to several phenomenons such as multi-path fading, noise interference etc. Further drawback of TDOA technique lies in its reliance on energy consuming and expensive hardware making it less suitable for resource-constrained nodes in WSN. Niculescu and Nath [4] have proposed a localization algorithm APS (Ad hoc Positioning Systems) based on AOA. Each node receives radio signal from beacons and estimates its own position by bearing/angular separation between beacons and itself. To be more specific, the location of a node is determined by the intersection of all bearings and the distance between node and beacon. Once the nodes become localized it acts as a beacon and that information is forwarded in a hop by hop fashion to localize the others nodes. With the help of this newly transformed beacons, the nodes which are not in direct Avishek Dan Dept. of Computer Science & Engineering Indian Institute of Technology Bombay Mumbai, India avishekdan@cse.iitb.ac.in Subir Halder Dept. of Computer Sc. & Engg. Dr. B C Roy Engineering College Durgapur, India subir_ece@rediffmail.com Sipra DasBit Dept. of Computer Science & Technology Bengal Engineering and Science University, Shibpur Howrah, India siprad@hotmail.com