Abstract
Localization systems are the source of data that allows to evaluate elderly person’s behaviour, to draw conclusions concerning his or her health status and wellbeing, and to detect emergency situations. The article contains a description of a system intended for elderly people tracking. Two novel solutions have been implemented in the system: a hybrid localization algorithm and a method for wireless anchor nodes synchronization. The algorithm fuses results of time difference of arrival and received signal strength measurements in ultrawideband (UWB) and Bluetooth Low Energy (BLE) radio interfaces, respectively. The system allows to change the intensity of UWB packets transmission to adapt localization accuracy and energy usage to current needs and applications. In order to simplify the system installation, communication between elements of the system infrastructure instead of wire interfaces is performed over wireless ones. The new wireless synchronization method proposed in the article consists in retransmission of UWB synchronization packets by selected anchor nodes. It allows for extension of the system coverage, which is limited by the short range of UWB transmission. The proposed solution was experimentally verified. The synchronization method was tested in a laboratory, and the whole system’s performance was investigated in a typical flat. Exemplary results of the tests performed with older adult participation in their own homes are also included.
Highlights
Europeans are living longer, and it is prognosed that, by 2060, one third of the population will be aged 65 or older [1]
The system should provide localization accuracy and precision needed for particular application, the system should assure reliable coverage of the whole area where the person’s activity takes place, the system tags should be energy efficient, the system tag size and weight should be reasonable, not disturbing everyday activities of the user, the system infrastructure should be as unobtrusive as possible
The best results are achieved with UWB solution, whereas the accuracy using only Bluetooth Low Energy (BLE) is worse
Summary
It is prognosed that, by 2060, one third of the population will be aged 65 or older [1]. The radio-based device-free systems performance is the best in line of sight (LOS) conditions; if the sensors are obstructed, the localization accuracy may suffer Another factor which influences tracking system acceptance, especially in the case of people living in their homes, is the unobtrusivity of the system infrastructure. The system should provide localization accuracy and precision needed for particular application (e.g., room level accuracy is sufficient for occupancy determination and submeter precision is needed for wandering detection), the system should assure reliable coverage of the whole area where the person’s activity takes place, the system tags should be energy efficient, the system tag size and weight should be reasonable, not disturbing everyday activities of the user, the system infrastructure should be as unobtrusive as possible.
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