Research On Indoor Localization Method Based On Sound Propagation

With the rise of the Internet of things application, the practicability and necessity of indoor positioning technology of certain situations has become increasingly significant. It is currently one of the hottest researches and has broad prospects. On one hand, satellite signal cannot penetrate buildings so that it will be out of action in indoor environments. On the other hand, the positioning accuracy of mobile base stations is too low to meet the needs of indoor positioning requirement. Because of the changeable indoor environment, it is very difficult to give consideration to both precision and stability. Thus, building a positioning system suitable for indoor environments has the vital practical significance.This paper introduces the characteristics of sound propagation channel first and puts forward a digital communication system which is suitable for sound wave transmission. At the same time, we build a system simulation platform with Matlab to verify the performance of the acoustic communication system. The simulation results show that the system has a certain anti-noise and anti-multipath capability.Then it presents the indoor positioning principle based on the designed acoustic communication system and analyses two factors which affect the positioning accuracy of the scheme mostly, that is time synchronization between base stations and geometric layout of transmitting base stations. This paper proposes a response synchronization mechanism which can achieve high precision base station time synchronization of nanosecond order, and a broadcast synchronization mechanism which can achieve time synchronization of microsecond order. We introduce the base station layout geometric dilution of precision, then choose several practical and feasible layout methods according to the experimental site, and determine experimental layout scheme at last.Afterwards, this paper introduces the principles of the least square method adopted in position calculation, then verifies it by simulation and analyzes its performance. Simulation results show that the errors of most points are in the range of target accuracy, which meets the phased objectives of the scheme. Since the exact moment of the positioning signals transmitted by base stations to reach the receiving terminal relates to the signal demodulation and pseudo-range measurement. Through a lot of actual measurement and analysis, we design a determining method of double sliding threshold window to conduct the LFM signal reach retrieval, the results indicate that this method also meets the phased objectives of the scheme.At last, the paper introduces the design scheme of each module of positioning system platform. Then we carry out the base station sound wave communication experiment and indoor positioning experiment. Experimental results show consistence with the previous simulation of base station distribution and location calculation. The indoor positioning experiment shows that the indoor positioning method based on sound spread spectrum communication still has certain feasibility and good application value.