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Low-power intelligent displaying system with indoor
mobile location capability
Marius Vochin 1[0000-0003-1962-035X] Alexandru Vulpe 1 0000-0003-1970-1117] Ioana Marcu1 and
George Suciu2
1 University POLITEHNICA of Bucharest, Sector 6, Romania
2 Beia Consult International, Bucharest, Romania
marius.vochin@upb.ro
Abstract. Modern buildings require different IT facilities, therefore integrated
communication services have become a must. Although there are already com-
mercial products on the market, most of them need well trained operators, while
others require manual and time-consuming operations. The present paper intro-
duces an intelligent displaying and alerting system (SICIAD), implemented
over a communication infrastructure with support for wireless ePaper and iBea-
con technologies to enhance displaying static and dynamic information, as well
as to ease the indoor orientation of guests using smartphones. An Android mo-
bile application is developed which enables indoor user location and guidance.
Possible beneficiaries of such systems are educational and research institutions
due to remote authentication support in research facilities through Eduroam
technology. The paper gives functional validation and performance evaluation
aspects are presented for the indoor positioning component of the proposed sys-
tem.
Keywords: ePaper, iBeacon, alerting system, indoor positioning, low power
display.
1 Introduction
Nowadays, the need for an intelligent, integrated, sustainable and easily managed
system for digital and up-to-date room signage for offices, meeting rooms and confer-
ences has an increase importance for modern public and office buildings. The emer-
gence of Internet of Things (IoT) and digital interactions using electronic paper (ePa-
per) [1][2] technology has marked a new phase of technological innovation in this
direction. Important advantages are also brought by iBeacon [3] technology, which
relies on the Bluetooth Low Energy (BLE) standard to create stationary constellations
of low-power beacons which can be used to determine the indoor position of mobile
terminals or signaling points of interest.
This work is part of the SICIAD [4][5][6] research project which proposes an intel-
ligent displaying and alerting system that relies on wireless ePaper and iBeacon tech-
nologies to create custom displays for both static and dynamic information, as well as
to ease the indoor orientation of guests.
2
In this paper, the iBeacon capabilities of the SICIAD system are investigated in re-
spect to indoor advertising, guidance and location.
The paper is organized as follows: in Section 2 there is presented the mobile device
positioning system, Section 3 contains detailed experimental validation scenarios,
while Section 4 outlines the conclusions.
2 Mobile positioning system
A mobile application was developed for Android system which enables the user to
detect its location based on the availability of Wi-Fi and iBeacon (BLE based radio
packets) signal presence. The main functionalities of this software module are to cap-
ture BLE packets, to extract location relevant information and to process them in
order to display notification or alerts related to current status and user position. The
application functional validation was performed on a commodity hardware such as
LG K8 mobile phone with BLE 4.2 support and Android 6.2 operating system.
The application tests if the device is Bluetooth enabled, whether the adapter is
turned on, if multiple Bluetooth notifications are allowed, and whether access to the
current location of the phone is allowed. As the instructions are parsed, a checkup is
made to see if the permissions have been granted, and the user is asked to allow ac-
cess. If all the conditions are met, the necessary processes are created, and the appli-
cation continues to function. If something is missing, a corresponding error message
will be displayed, and the application will stop.
The list of retrieved devices is presented with details (name, address, time since
the last occurrence, current and average RSSI level, relative distance estimation, RSSI
mediated levels, and details display button). Only details about the rooms where
LANCOM devices with iBeacon capabilities are located are shown; other received
BLEs beacons are displayed by the app, but as no details are known about their
location or configuration, only a general message will be displayed if the user selects
them. These unknown devices can be filtered before adding them to the list, resulting
in faster application performance (no need to process their data).
Different measurements were conducted on the access points in the University
Politehnica of Bucharest (UPB) campus, which is a reinforced concrete building, with
30 centimeter thick walls. The location chosen to test the positioning solution is on
the 3rd floor of Building A from Faculty of Electronics, Telecommunications and
Information Technology, Bucharest, which is an area with offices and laboratories, as
shown in Fig. 1. Commodity hardware has been used at the BLE receiver part, such as
SM-G361F, G930FD smartphones, and also a HP ENVY x360 laptop. Three Lancom
access points with integrated iBeacon transmitters were installed, one LN-830 E [7]
model and two L-151E [8]. They were scheduled to periodically emit BLE advertising
beacons to be visible to mobile devices, and a maximum power lever was choosen
from three available levels.
3
Fig. 1. Testbed location plan
Lancom iBeacon has been factory calibrated to provide three power levels at a dis-
tance of 1 m: high (-52 dBm), medium (-58 dBm), and low (-75 dBm) of the broad-
casted beacon message, which allows an approximation of the distance between the
access point and BLE receiver. For beacon broadcasting dedicated frequencies can be
used: 2402 MHz, 2426 MHz, and 2480 MHz. With our off-the-shelf smartphone, the
measurements at reception indicate -40, -46, -62 dBm, at a distance of several cm of
the antenna.
3. Experimental evaluation
It has been concluded from the measurements that a -10dBm attenuation is induced by
a campus wall placed between the sender and receiver BLE device. Therefore, by
setting the access point emission power at the lowest level and having one beacon in
each room we would accurately provide room signage capability.
Each router used a unique MAC physical address, and different major and minor
beacon values were set allowing the packets to be differentiated according to their
source.
In the lobby, the points of measurement are aligned along two straight lines
parallel to the hall walls. These two straight lines are 0.5 meters from the nearest
hallway, and within a distance of one meter. Along each straight line there were six
measuring points, which represent a total of twelve locations. To calculate the
distance between the router and the mobile terminal at each of these points, a simple
Pythagoras' theorem for rectangular triangles was used.
4
(a)
(b)
(c)
Fig. 2. Variation of RSSI with distance increasing for AP1 (a), AP2 (b) and AP3 (c)
The corresponding colors in Fig. 2 are: green for "x" - the measured average values of
the RSSI, red for the maximum values obtained and blue for the minimum values
corresponding to the respective distance between the terminal and each of the three
acces points. Thus, there can be observed the variation and distribution of values for
each location. There can be noticed quite large variations, although the transmitter
5
and the receiver were fixed during the measurements. These variations occur because
the radio signal reaches the receiver on several paths that have different lengths and
are attenuated due to passing through various objects or by the reflection of radio
waves.
With green, curves were plotted considering the average values of the RSSI. They
have different characteristics, being influenced by the walls through which the signals
have been propagated. Their descriptive mathematical formulas are shown below:
1. F1(x) = -8.04738496*ln(x)-61.27611836
Distance variation of the reception power level for AP1 transmitter.
2. F2(x) = -13.73284621*ln(x)-54.99489558
Distance variation of the reception power level for AP2 transmitter.
3. F3(x) = -12.23482004*ln(x)-53.26174039
Distance variation of the reception power level for AP3 transmitter.
It can be noted that each function is different from the other. In addition, they
depend on the placement of objects in the building. Table 1 illustrates how good
the approximations were with the actual measured values.
Table 1. Comparison between estimated and measured values for access point AP1 (a), AP2
(b) and AP3(c)
Distance [m]
Computed RSSI
[dBm]
Measured RSSI
[dBm]
Error [dBm]
Mean error
[dBm]
1
-61.28
-58
3.28
2.45
1.48
-64.43
-71
6.57
2.47
-68.55
-69
0.45
3.6
-71.58
-73
1.42
4.11
-72.65
-69
3.65
6.46
-76.29
-77
0.71
6.76
-76.65
-74
2.65
9.41
-79.32
-74
5.32
9.62
-79.49
-79
0.49
12.39
-81.53
-81
0.53
12.54
-81.63
-82
0.37
15.37
-83.26
-85
1.74
15.49
-83.33
-88
4.67
(a)
6
Distance
[m]
Computed RSSI
[dBm]
Measured RSSI
[dBm]
Error [dBm]
Mean error
[dBm]
1.72
-62.44
-71
8.56
3.31
2.7
-68.64
-68
0.64
3
-70.08
-63
7.08
3.64
-72.74
-62
10.74
3.87
-73.58
-76
2.42
4.39
-75.31
-78
2.69
6.71
-81.14
-83
1.86
7.02
-81.76
-82
0.24
9.64
-86.11
-89
2.89
9.86
-86.42
-85
1.42
12.61
-89.8
-91
1.2
12.78
-89.98
-90
0.02
(b)
Distance
[m]
Computed RSSI
[dBm]
Measured RSSI
[dBm]
Error
[dBm]
Mean Er-
ror [dBm]
1
-53.26
-57
3.74
5.47
2
-61.74
-55
6.74
3.19
-67.45
-77
9.55
4.02
-70.28
-70
0.28
4.18
-70.76
-63
7.76
4.71
-72.22
-85
12.78
4.84
-72.56
-64
8.56
5.43
-73.96
-72
1.96
6.34
-75.86
-71
4.86
6.89
-76.88
-69
7.88
7.22
-77.45
-82
4.55
7.71
-78.25
-78
0.25
10.01
-81.45
-86
4.55
10.37
-81.88
-85
3.12
(c)
7
4 Conclusions
The system presented in this work implements an integrated communication infra-
structure which offers dynamic display capabilities using the ePaper technology, as
well as enables indoor location-based services such as visitor guidance and alerting
using iBeacon-compatible mobile devices.
Being based on the BLE standard, iBeacon technology can potentially operate
with almost all off the shelf smart mobile terminals, providing a cost-effective solu-
tion for an indoor positioning system. In combination with a smartphone application
and a wireless communication system, BLE can enable advertising and distribution of
location-based content.
In order to maintain real-life relevance of achieved data, commodity hardware was
chosen to be used in test scenarios. A professional mobile BLE receiver was consid-
ered in order to improve indoor location awareness precision, but this would question
relevance of data obtained in the context of commercial and industrial applicability.
While the iBeacon emitters integrated in the used Wireless access points can ena-
ble location-based services, accurately determining each users’ location may require
additional, battery-powered BLE beacons. Such a network (or constellation) of bea-
cons could provide a more performant indoor guidance system, due to its effective-
ness at a range of several meters (compared to several centimeters for NFC tags).
Moreover, although the investment in Beacon devices may be significant, the already
widespread use of compatible smart devices may reduce the necessity of other hand-
held devices.
ACKNOWLEDGMENT:
This work has been funded by UEFISCDI Romania under grant no. 60BG/2016 “In-
telligent communications system based on integrated infrastructure, with dynamic
display and alerting - SICIAD”, and partially funded by grants no. 270CI ⁄ 2018 Intel-
ligent Hive Colony Monitoring System- SIMCA, grant of the Ministry of Innovation
and Research, UEFISCDI, project number 33PCCDI/2018 within PNCDI III and
supported in part by Minister of Research and Innovation Ro-mania through project
SmartAgro (contract no. 8592 / 2018).
Engineer CALIN Mihai-Catalin contributed to this work, during the preparation of
his master thesis.
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