Distance measurement system based on visible light communications and ultrasound emitters

Abstract

Distance estimation is an important task in positioning systems, as it is needed for performing the triangulation process used by location algorithms. Different techniques, such as received signal strength indication (RSSI), time of arrival (ToA), and time difference of arrival (TDoA), can be used to estimate the distance between devices. Cricket indoor positioning systems, designed by MIT, are based on TDoA techniques, and they use a combination of ultrasound and radiofrequency signals. In this paper, a new distance measurement scheme based on Cricket technology, but introducing some modifications, is proposed. In this way, some new advantages are obtained. The radiofrequency signal is substituted by an optical signal, making the system applicable to environments where radio emissions are not suitable. Furthermore, a double-way measurement is also introduced, in order to allow both measurement devices (base station and mobile node) to perform the distance estimation, unlike in Cricket systems, where only one of the devices is able to calculate the distance.