ISSN: 2229-6948(ONLINE) DOI: 10.21917/ijct.2014.0145 ICTACT JOURNAL ON COMMUNICATION TECHNOLOGY, DECEMBER 2014, VOLUME: 05, ISSUE: 04 1015 RSSI BASED LOCATION ESTIMATION IN A WI-FI ENVIRONMENT: AN EXPERIMENTAL STUDY M. Ganesh Madhan 1 , U.S. Susaritha 2 , R. Ragupathi 3 and Ashita Priya Thomas 4 Department of Electronics Engineering, Madras Institute of Technology, Anna University Chennai, India E-mail: 1 mganesh@annauniv.edu, 2 susarithasekar30@gmail.com, 3 ragu4584@gmail.com, 4 ashitaprincess@yahoo.co.in Abstract In real life situations, location estimation of moving objects, armed personnel are of great importance. In this paper, we have attempted to locate targets which are mobile in a Wi-Fi environment. Radio Frequency (RF) localization techniques based on Received Signal Strength Indication (RSSI) algorithms are used. This study utilises Wireless Mon tool, software to provide complete technical information regarding received signal strength obtained from different wireless access points available in a campus Wi-Fi environment, considered for the study. All simulations have been done in MATLAB. The target location estimated by this approach agrees well with the actual GPS data. Keywords: RSSI, Access Point (AP), Root Mean Square Error (RMSE), Signal Strength Set Identifier (SSID), RF Localisation 1. INTRODUCTION Wireless communication has become an inevitable part of our life. It has significant impact in high end applications such as complex defence operations as well as simple application of accessing internet or remote control. In the present era of wireless communication seamless connectivity, accessibility and portability are essential requirements [1]. A large number of electronic systems ranging from mobile phones to missiles have to be tracked. This brings in the need for location identification in the first stage. Under these circumstances, an optimal solution for target detection and tracking becomes necessary. Traditional methods of target detection and positioning include the use of satellite based Global Positioning System (GPS). But there do exist certain constraints in satellite navigation that cannot be overlooked. In urban and indoor environments, the signals are too weak and suffer from severe multipath and interference degradation making GPS ineffective [2][3]. Hence alternate methods for localization were investigated. A widespread deployment of Wireless Local Area Networks (WLANs) for establishment of point to point and multipoint communication links has been quite successful in urban areas. Using such wireless networks along with their receiver signal strength information, target positioning becomes easy and can be used in those areas where GPS is not effective. The advantage of this alternative approach is the ease of accessibility and cost effectiveness. There are different localization estimation and identification techniques like RSSI, Time of Arrival (TOA), Time Difference of Arrival (TDOA) and Angle of Arrival (AOA) [2]. Of all the above schemes RSSI based algorithms are preferred as they require minimum hardware and software without the need for synchronisation as in TOA and TDOA. Moreover their implementation is easier. Thus, RSSI based location estimation is a better choice in a Wi-Fi environment. RSSI based techniques require accurate signal power measurement to infer the range using appropriate path loss models. Using RSSI, any of the algorithms such as trilateration, multilateration and triangulation [2] can be applied to achieve localization. In this paper, RSSI technique for position estimation has been used to determine the target location in a Wi-Fi environment. Further the target location obtained in this approach is compared with actual location coordinates derived from GPS. 2. NETWORK ARCHITECTURE Target detection and tracking is achieved by designing a cooperative network. In order to implement Received Signal Strength (RSS) algorithm, we consider the following requirements and the scenario is depicted in Fig.1.  Minimum of three base cum control stations (APs)  A mobile device (target) which can access these stations and transmit to stations the information regarding the received signal strength from them This will let the control stations know about the RSS at the device due to itself and due to other stations. This information will help in localizing the target device. Fig.1. Network Scenario The mobile device i.e. the target sends the RSS information due to every access point to all the control-base stations. Based on this RSS information, target is localized by employing RSSI