Abstract
We consider the problem of estimating the location of people as they move and work in indoor environments. More specifically, we focus on the scenario where one of the persons of interest is unable or unwilling to carry a smartphone, or any other “wearable” device, which frequently arises in caregiver/cared-for situations. We consider the case of indoor spaces populated with anonymous binary sensors (Passive Infrared motion sensors) and eponymous wearable sensors (smartphones interacting with Estimote beacons), and we propose a solution to the resulting sensor-fusion problem. Using a data set with sensor readings collected from one-person and two-person sessions engaged in a variety of activities of daily living, we investigate the relative merits of relying solely on anonymous sensors, solely on eponymous sensors, or on their combination. We examine how the lack of synchronization across different sensing sources impacts the quality of location estimates, and discuss how it could be mitigated without resorting to device-level mechanisms. Finally, we examine the trade-off between the sensors’ coverage of the monitored space and the quality of the location estimates.
Highlights
According to a 2012 study commissioned by the Alzheimer’s Society of Canada, 747,000 Canadians have some type of cognitive impairment, including dementia, and this number is expected to double by 2031
In this paper we focus on (a) the fusion of data collected by passive infrared (PIR) motion sensors with data collected from tiny Bluetooth Low-Energy (BLE) beacons attached with simple adhesive glue on surfaces around the home and collected through an application running on the occupants’ Android smartphones
While we take some measures to consider the kinematic behavior of the individuals, we do not rely on it, as the activities in which an individual is engaged in a small indoor space call for frequent changes of direction and speed, and some tasks are fundamentally unsuitable for dead-reckoning approaches
Summary
According to a 2012 study commissioned by the Alzheimer’s Society of Canada, 747,000 Canadians have some type of cognitive impairment, including dementia, and this number is expected to double by 2031. The occupants can be provided with a smartphone, running a background service that collects, and transmits to the SmartCondoTM platform, signal-strength measurements from any nearby BLE beacons These two types of data sources—sensors and beacons—are used to infer the occupants’ locations at each point in time. [3] has utilized the impact of humans on the RF environment to estimate the locations of multiple subjects, based on models of how the fingerprints of radio signal strength indicators (RSSIs) change in the presence of people in the space This method requires a large set of transmitters and receivers to cover the entire area in each room and the placement of the transmitters/receivers needs to be exact to ensure that they are in line of sight (LoS).
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