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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: oscillator's 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.