RADIO NAVIGATION IN WIRELESS OFDM SYSTEM

Jang Gyu Lee and Hye-jung Bang: School of Electrical Engineering, Seoul National University, Seoul 151-744, Korea, (E-Mail) jgl@snu.ac.kr, ilovely0@snu.ac.kr

Abstract

Recently, developments in the Enhanced-911 (E-911), location-based business, and electronic mobile commerce call for accurate location for cellular subscribers. Wireless location techniques that use signals propagating between the base station and the mobile station in a cellular network are widely sought to meet this need. Besides voice communication, the next generation cellular network systems for data service such as the wireless internet system can provide subscribers with the automatic location identification (ALI), that is, the location-determination anywhere, anytime, on any device.

The objective of this paper is to demonstrate a positioning possibility for a wireless internet system. The wireless internet system considered in this paper is a mobiled version of the WiMAX system that has been developed to send a higher-bandwidth signal of several tens of megabits per second to fixed receivers over a distance of several tens of kilometers. WiMAX is part of the IEEE 802.16 standard. The wireless internet system is designed to provide high-speed access of a maximum 1 megabits per second to receiver devices moving at speeds of 60 to 70 kilometers per hour and is to provide high data rate wireless internet access with mobile user under the stationary or mobile environment, anytime and anywhere. It is based on IEEE 802.16e standard.

In this paper, a time difference of arrival (TDOA) method is used to determine the user position. The TDOA method has been used in several wireless signal of communication networks such as Global System for Mobile communication (GSM) network and Code Division Multiple Access (CDMA) network besides Global Positioning System (GPS). According to the IEEE 802.16e standard, all base stations are synchronized using GPS time. So we can use the TDOA method to determine the mobile user position in the wireless internet system assuming that we know the location of base stations.

And the preamble symbol can be used to detect the received time of signal transmitted from base station. It is placed in front of frame of DownLink. And base stations can be distinguished because each base station uses the different preambles. So positioning can be feasible in the wireless internet system. According to the IEEE 802.16e standard, the preamble symbol length in the system is 115.2us. This preamble symbol has cyclic prefix to avoid multipath effect. The length of cyclic prefix is 12.8us. So the active symbol of the preamble symbol has a length of 102.4us. And the sample interval of the active symbol is 0.1us because the active symbol is composed of 1,024 samples, Therefore the resolution of positioning can be around 30m. This satisfies E-911 accuracy.

The positioning method, algorithm, and the expected accuracy through simulation will be discussed in this paper. The simulation will be using the preamble symbol for hearability and accuracy test. Hearability of one mobile user from multiple base stations should be checked for the location determination of a mobile user since the location of a mobile user can be determined through triangulation using more than three relative delays. It is expected that location determination using the wireless internet system satisfies E-911 accuracy without using GPS.

Short Biography

Jang Gyu Lee received the B.S. degree from Seoul National University in 1971, and the M.S. and Ph.D. degrees from the University of Pittsburgh in 1974 and 1977, respectively, all in electrical engineering.

In 1977, he was employed by The Analytic Sciences Corporation (TASC), Reading, Massachusetts, doing research in the areas of missile parameter identification, missile guidance, and security assessment of power plants. From 1981 to 1982, he was with the Charles Stark Draper Laboratory, Cambridge, Massachusetts where he worked in the areas of inertial navigation systems and optimal control of underwater vehicle. In 1982, Dr. Lee joined the faculty of Seoul National University, College of Engineering, School of Electrical Engineering, as an Assistant Professor, and since 1992 he is Professor at the same school where he is engaged in both teaching and research. He is also responsible for the graduate course sequences in inertial navigation theory, and optimal control and estimation theory. In 1998 and 1999, he was a visiting professor with the Bradley Department of Electrical and Computer Engineering and the Center for the Study of Science in Society, Virginia Polytechnic Institute and State University in Blacksburg, Virginia, U.S.A.

Dr. Lee is the author of more than 100 journal papers and 250 conference papers in inertial navigation, optimal control and estimation theory. In addition to his academic duties at Seoul National University, he has been named as director of Automatic Control Research Center from the inception in December 1994, which is one of academic research centers in Korea sponsored and supported by the Ministry of Defense. His current research interests include theory and applications of linear and nonlinear filtering, navigation technologies, and MEMS-based inertial sensors.

Dr. Lee is a member of National Academy of Engineering of Korea, Sigma Xi, KIEE(Korean Institute of Electrical Engineers), AIAA, IEEE, IFAC Technical Committee on Aerospace, and IFAC Technical Committee on Education.