IEEE Consumer Electronics Magazine - January/February 2022 - 69

demand fashion to reduce battery consumption.
FinderX is compatible with Android 6.0 and iOS
12.1 or a newer version. The preconfigured beacon
information comes up with the installation
package. However, there is a provision to update
the list of beacons and their responsibility in
real time. Although the application shows only
the nearest distance from multiple beacons, it
periodically stores all available signal data for
future calculations. Figure 4 shows FinderX application
interface for nearest amenities.
Distance Calculation
We calculate the distance between user and
Figure 4. FinderXmobile applicationwith an
approximate distance. (a) Nearest trash bin with
distance inmeters. (b) Nearest restroomwith distance.
on average 32% battery, where Android phones
are responsible for on average 38% battery. We
used the same numbers of smartphones for
Android and iOS to measures the battery consumption
for GPS, Bluetooth, and the FinderX
application. To eliminate the battery-capacity
differences due to manufactures and models, we
counted the percentage values.
SYSTEM DESIGN
There are three components in the FinderX
system-preconfigured beacons, a mobile application,
and a backend server. We configured the
beacons based on their purpose (e.g., indicator
beacons, helper beacons, etc.). The mobile application
runs on the receiver devices (e.g., smartphone,
smartwatch, etc.) as a background
service and is responsible for all types of calculations.
The server is not required for the basic
operation, but it helps update and modify the
beacon list in real time.
Mobile Application
The mobile application helps to build an
interface between users and beacons. To receive
the BLE signal and calculate the distance, we
developed the FinderX mobile application for
Android and iOS platforms. Only some benign
permission is needed for positioning, and the
application use required services in an onJanuary/February
2022
beacon position by Received Signal Strength
Indicator (RSSI). The RSSI and distance are
inversely proportional; if the signal strength
increases, the distance decrease and vice versa.
The mathematical formula to distance calculation
from RSSI is as follows:
RSSI ¼ð10nÞlog10ðdÞþ A:
(1)
Here, A is the transmission power, d is the distance,
and n is the signal propagation constant.14
Modern beacons come up with manufacturerspecific
SDK that also provide the distance. The
receiver must uniquely identifies the beacons
with multiple values (e.g., UUID, Major, Minor,
etc.) to calculate the distance. We can regulate
how frequently the receiver application will get
signals and perform the calculation. The frequent
distance calculation provides a more
accurate reading but drains the smartphone battery.
FinderX application receives a signal and
calculates the distance once in every second.
Theoretically, the receiver gets a BLE signal
immediately within a beacon radius. However,
we found that it takes up to two seconds to get
the signal at the study site (in the outdoor
environment).
Direction Toward Beacon
Beacon's broadcasts signals spherically and
does not have any indication for directions. The
FinderX application calculates direction using
the distance-over-time approach. If the distance
decreases over time, it indicates that the user
is going toward the beacons. The distance
increases if the user goes in the opposite
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