Ultrasonic Trilateration Methods for Low-Cost Indoor Positioning

Trilateration is a process where distances to known control points or beacons can be used as inputs to algorithms to calculate an object’s position. Most of the common trilateration methods known are fast and reliable, and based on estimating one or more location-dependent signal parameters like Times-of-arrival (TOA), Angle of Arrival (AOA) or Received Signal Strength (RSS). However, costly hardware is needed for such approaches to run reliably, and are too computationally complex both in speed and memory for low-cost hardware. The demand for low-cost hardware has greatly increased in recent years mostly due to the rapid emergence of internet of things, that promises to bring connectivity to just about everything. As such, leveraging on cheap hardware is an important step to take to achieve accurate indoor positioning. Because of convenience in generation and transmission, ultrasound is widely and commonly used electronically for distance measurement. The use of ultrasound with cheap hardware for accurate indoor positioning is discussed in this paper. Three localization methods that are reliable and fast enough for cheap hardware are analyzed with emphasis on the speed and memory demands. Experimental results show that the Maximum Likelihood estimation approach is the most accurate. Keywords: Time of arrival; Trilateration; Ultrasound; Localization; Indoor positioning. DOI: 10.7176/ISDE/10-5-04 Publication date:June 30th 2019