Experimental Study of Single-Transmitter-Based Precise Indoor Positioning System

A single-transmitter-based positioning system using an antenna array has been designed and developed to minimize the number of transmitters needed for environments where satellite-based navigation systems are unavailable. One of its suitable applications is for indoor navigation. The user receives the signals from the antenna array and calculates the position using the carrier-phase measurements. A key feature of the system is that the number of cycle ambiguity candidates is geometrically bounded. If the length of the antenna baseline is smaller than half the wavelength, the ambiguity resolution process is unnecessary. To improve the positioning performance for practical use, the antenna baseline must be enlarged. Even in this case, the cycle ambiguity resolution issue can be resolved fast and accurately. For instance, there are only nine candidates according to the setting of the study. To investigate the performance of the system, experiments for a dynamic rover using multiple “pseudolites,” pseudo-satellite transmitters, were conducted. In addition, low-cost inertial measurement unit (IMU) sensors were combined to investigate the improved positioning accuracy. Experimental results showed that positioning root-mean-square errors were 18 cm and 25 cm with IMU and without IMU, respectively, at the scale of a conventional meeting room. All integer-cycle ambiguities were solved accurately during the experiments, and more than 93% were resolved within 5 s.