Takamasa Kawaguchi

Methods for improving IMES transmitters: Transmission diversity, variable beamwidth antenna, and leaky coaxial cable

IMES is an indoor messaging and positioning system. In the present work, three methods for improving the IMES transmitter are proposed based on the result of a radio acquisition analysis: transmission diversity, a variable beamwidth antenna, and a leaky coaxial cable (LCX). The transmission diversity method increases the possibility of signal acquisition in areas with weak signal. A small-sized variable beamwidth antenna is developed to mitigate the multipath interference in narrow spaces. A field experiment with a LCX in an actual train setup is conducted to verify the effect of the LCX for the positioning of moving vehicles. The evaluation results of the proposed methods suggest their potential to be applied to practical applications.

Development of IMES signal transmitters

An indoor messaging system named the Indoor Messaging System (IMES) is expected to be an indoor positioning infrastructure. However, conventional IMES signal transmitters have three major issues: oscillators cost, low usability, and wired-configuration. In the present work, a transmitter aimed to avoid these issues is developed and evaluated in conjunction with a prototype IMES receiver. The developed transmitter generates its carrier wave by using an HP-TCXO. It uses a whip antenna instead of an RHCP antenna, and its operation parameters are configured through a wireless communication. The evaluation results show that the developed transmitter can improve the usability and maintainability of IMES. A transmission space diversity method is also proposed to mitigate the influence of multipath interference. A transmitter based on this method is developed and experimentally evaluated in a practical setup (Hankyu Third Avenue underground mall in Osaka). The experimental results show that the proposed method can improve the availability of the cell of the IMES signal service area. These findings contribute further to development of a practical IMES transmitter and receiver.