A new position detection method using leaky coaxial cable

Recently, the demand on position detection system using WiFi[1] and cellular phone[2] have been appeared. Car navigation system and 3G cellular phone use GPS(Global Positioning System) for position detection. However, it is impossible to use GPS underground because GPS signal cannot be received due to obstacles. Therefore, many position detection methods to use at narrow area have been proposed[3]-[5]. A method in [3] is a method using wireless sensor nodes. At the underground, the LCX(Leaky CoaXial cable) is considered as a preferable infrastructure, because LCX has already been constructed in the underground shopping center. Another position detection methods[4], [5] use LCX. The LCX is considered as a preferable infrastructure, because LCX has already been constructed in the underground shopping center. In [4], LCX performs as an intruder sensor by using two parallel LCXs are located. But it cannot detect two-dimensional position. A method in [5] can detect two-dimensional position. But two kinds of RF-band and two LCXs are required. In this paper, a new position detection method using one kind of RF-band and one LCX is proposed. Proposed method utilizes two TOA (time of arrival) parameters which are direct wave from the feeding point and reflected wave from the end of LCX. Two-dimensional position could be estimated from two propagation delay time.