Analysis and Development of a Localization System Based on Radio Frequency D. M. Ferreira 1 , A. F. Ribeiro 2 , J. P. Carmo 3 and J.G. Rocha 4 1,2,4 Industrial Electronics Department, University of Minho, Campus de Azurém, 4800-058 Guimarães, Portugal 3 Technology and Administration High School, Polytechnic Institute of Bragança, Apartado 134, 5301-857 Bragança, Portugal 1 dvd.matos@gmail.com, 2 fernando@dei.uminho.pt, 3 jcarmo@ipb.pt, 4 gerardo@dei.uminho.pt Abstract-This paper presents an analysis on several strategies for location based on Radio-Frequency. The purpose of this study is to develop an infrastructure able to determine the position of a target within an area of 0.1 acres (aprox.11000 ft2 or 1000 m2) with an acceptable precision for the specific task. Along with the analysis of the many strategies and approaches on Radio- Location, this study tries to determine the best solution to implement a working system of location in an easy, secure and less expensive way, a solution able to be used in football field, without the use of large and/or expensive infrastructures like the Global Position System (G.P.S.) network. I. INTRODUCTION As technology grows at an amazing rate, everyday we have to face numerous and various tools which, only a few years back, were only part of our imagination. Radiolocation is one of those tools, where the most commonly known system is the G.P.S. Not long ago, this technology was only available for the USA army. Nowadays, it is present in our everyday life, from airplanes to cars, from laptop computers to mobile phones. But, what if a restrictive and isolated network is required? What if the requirement is a system to use in places where the satellite signal is not available? What if the requirement is a location in a restricted area with accuracy to the centimeter, in which the G.P.S cannot guarantee security? Following is a short analysis. Parking spaces in big metropolis are becoming a huge problem, so a frequent solution is to build parks under the ground and under buildings. It is hard to receive GPS signal on underground floors. The largest building in the world, by volume, is the “Future of Flight Aviation Center & Boeing Tour” with a volume of 472,000,000 ft 3 [1], where the 747, 746, 777 and soon the 787 [2], are built. Several persons work in this building, from engineers to technicians, janitors and caterers. To know the location of each person on the working area (for example, to know if the Master Engineer is in the assembly line area or if he is in the cafeteria) would be a tremendous tool. At the same time, Automated Guided Vehicles (or AGV) could be easily controlled and tracked down because the system would known its position on the working area, all within a restricted area, with full control of it. For e.g.: the location of a ball in a field during a football game, its direction, speed and height, but with a precision to a point where you can determine if the ball passed the side line. FIFA has recently approved the use of microchips in soccer balls [3], in order to assist the referees in their decisions concerning the goal line. The project, proposed by Adidas, is being implemented by the company Hawk-Eye [4] which has previous experience in tennis and cricket. Although, it has proven, with good results, in the Miami Tennis Master Series, it is still an image based system. With a radio-frequency system, the implementation would be simpler and probably less expensive. In this case, there is a factor that could become a problem: update ratio. The system would have to be able to keep up the speed at which a ball can reach in a professional football game. In a regular game, a ball can reach up to (v b ) 30 m/s (about 70mph). If the system has a maximum error (d) of 3 cm, the time (T err ) need to travel that distance is: ms m s m d v T err 1 03 . 0 / 30     (1) And, the update ratio would be: Hz T ratio update err 1000 1   (2) Therefore, the system has to be able to update the target position, a thousand times (1000) a second, for a precision of 3 cm, in order to be acceptably reliable. And the possibilities must not be restricted to the ball. If a coach has a tool that records all the moves of each player on the field, he can easily create personal statistics like average speed, maximum speed, tendencies to play more on the left (or right) side, etc. II. STRATEGIES There are three fundamental strategies of radiolocation to consider: - Strength of signal - Angle of reception - Time based The first one, Strength of signal, is probably the easiest strategy to implement. It is used in mobile phones, cordless phones, and Bluetooth and WiFi networks. Even so, the applications using this method are as common as they are old. It is used by radio-amateurs to calibrate their transmitters, to detect interferences when implementing a wireless network 1441 978-1-4244-1666-0/08/$25.00 '2008 IEEE