Research on positioning and re-measurement mechanism of underground precise personnel positioning system

During the underground transmission of wireless signal, the measurement between card reader and marker card fails due to signal strength attenuation and interference. When the measurement fails, the marker card can only wait until the fixed measurement time slot in the next super-frame to measure the distance with the card reader again. As the marker card and the card reader re-measurement interval time is long, it is not conducive to control the real-time dynamic distribution of underground personnel in time. In order to solve this problem, a positioning and re-measurement mechanism of underground precise personnel positioning system is proposed. When the marker card measurement fails, the positioning and re-measurement mechanism uses the idle time slot to re-measure the marker card. When multiple marker cards compete for idle time slots for re-measurement, the hierarchical analysis method is used to determine the re-measurement priority of marker cards using idle time slots according to the accumulated re-measurement times, signal strength and movement speed of the marker cards. And the positioning card reader gives priority to the marker cards which fail in measurement according to the re-measurement priority level. The test results show that when the number of marker cards is less than 70, the positioning re-measurement mechanism can improve average the measurement success rate, reduce average the re-measurement delay, improve the time average slot utilization rate, and enable to monitor the uninterrupted marker card movement track in real time.