Development of Ultimate Seamless Positioning System Based on QZSS IMES

TLDR: Hideyuki Torimoto is president of GNSS Technologies Inc. he is managing GNSS R&D including IMES to promote the technology internationally.

Abstract: Satellite-based navigation systems generate huge location based service markets and it is expected that the market will drastically increase in near future due to necessity of GNSS enabled mobile phones for emergency services in USA, Japan and many other countries. In order to realize such huge growth, it is necessary to address the problems of seamless navigation which are limited by the current GNSS based applications alone. These systems are not strong enough to provide navigation in indoor and deep indoor environments with required resolutions. In order to solve these problems and provide indoor position, we have developed Indoor Messaging System (IMES). The basic concept of the IMES is to transmit position data and/or unique ID and/or other user defined data from the transmitter while keeping the similar signal structure as of QZSS/GPS signal. IMES has the same RF properties as GPS/QZSS and PRN IDs from 173 to 182 are assigned for IMES. The only difference is in the contents of navigation message which can be set as per user’s necessity and application fields. It is not necessary to compute pseudorange, hence a single unit is enough for position data. We have developed prototype IMES device based on QZSS-IS document. Experiments have been conducted using software receiver and prototype IMES capable mobile phone devices. The seamless navigation capability has been demonstrated by using the IMES capable mobile phone device. The mobile phone shows the user position in seamless fashion when the user moves indoors and outdoors. The interference analysis results showed that with proper separation of other GNSS devices from IMES transmitter, there is no harmful interference to the GNSS user. Based on these experiments, minimum threshold distance has been estimated, which is about 1.6m from the IMES antenna at transmission power of -70dBm. This paper discuss about IMES concept, signal structure, prototype device, various experiments and their results.