IEEE Consumer Electronics Magazine - January/February 2022 - 70

Special Section on Security and Sustainability Technologies for Smart Cities
Figure 5. Some samples of the installed beacons are at the study sites. The beacons in the circle are
installed on the targeted amenities surface to localize them.
direction. The application keeps track of user's
movements and gives a warning if they go in the
opposite direction. We assumed the average
human walking speed is 1-1.50 meters per second
to identify the user activity.
TEST DEPLOYMENT OF FINDERX
We set up a testbed in the urban university
campus to test the feasibility of the FinderX system.
We define the trash bins and restrooms as
the amenities and installed two types of preconfigured
beacons. Usually, one beacon is sufficient for
one location. However, we installed multiple
helper beacons to reach the amenities situated in
the far distance. There were eight beacons for the
trash bins and three for the restrooms. Figure 5
shows installed beacons at the testing site.
We faced several challenges while setting up
a testbed in the outdoor environment. Here, we
discuss the challenges and how we resolved
them in an actual setup.
Height of the Installed Beacons
The height of the installed beacons is a crucial
factor in getting an accurate signal. The signal
strength decreases if we install it on or near the
ground within 0-0.2 meters. We found that the optimal
height would be at least 0.6meters (2 feet) from
the groundby trial and error. Another indicationwe
found during distance calculation is that the user
70
carries their phone at that height. We did not try
more than 3 meters of height (15 feet) in our study.
As the Bluetooth signal strength decreases over distance
and some points were not at the same
distance, we have installed two supporting beacons.
These beacons do not provide a direct location
but give the direction toward a point.
Power Consumption
The battery issue is one of the main concerns
of beacon technology. Consumption depends on
multiple factors, such as the manufacturer settings,
broadcasting power, and advertising interval.
Modern beacons broadcast signals for up to
five years without any replacement of power
cells. We set the broadcasting power as +4 dBm
and the advertising interval as 100 ms, sufficient
for the testing sites. There was an automatic battery
health checking portal to identify the consumption
in the FinderX system. However, we
did not need to charge the battery during the
study. On the mobile application, we need to
turn on the Bluetooth service to get the BLE signal.
Besides, FinderX uses some other services
to get the user movement data (e.g., accelerometer,
light sensor, etc.). Continuous use of these
services causes battery drainage. FinderX only
turns on the services when the application is in
the foreground; it automatically turns off all
services after it goes to the background.
IEEE Consumer Electronics Magazine

IEEE Consumer Electronics Magazine - January/February 2022

Table of Contents for the Digital Edition of IEEE Consumer Electronics Magazine - January/February 2022