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Journal of Marine Science and Technology, Vol. 26, No. 1, pp. 11-18 (2018) 11
DOI: 10.6119/JMST.2018.02_(1).0002
A ZIGBEE/RFID SAFETY SYSTEM
AT THE SEAPORT
Sanja Bauk1, Diego Garcia Gonzalez2, and Anke Schmeink3
Key words: seaport, workers’ safety, ZigBee/RFID.
ABSTRACT
The paper examines three potential safety solutions for the
protection of port workers, which are based on a junction of
Radio Frequency IDentification (RFID), as an automatic iden-
tification, data collecting and positioning system from one side,
and ZigBee, as a low energy consumption communication tech-
nology from another. The considered solutions are placed in
the context of the individual needs and capacities of the devel-
oping Port of Bar in Montenegro (South East Europe), which
has been operating in the transitional environment for the past
two decades. The transitional circumstances prevent the port
from adopting advanced occupational and environmental safety
systems. Therefore we are proposing models for improving
the workers’ safety that are at the same time cost-effective, re-
liable and flexible. More precisely, the on port workers’ body
area sub networks formed by RFID active/passive devices are
treated in the paper as end nodes of the ZigBee network. On
the other hand, the forklifts’ RFID warning systems are treated
as the moving routers of the ZigBee network. Some simulation
experiments with such RFID/ZigBee hybrid system in an OPNET
environment have been implemented over the Port of Bar con-
tainer and general cargo terminal layout, while corresponding
conclusions have been derived, along with some directions for
further research work in the field.
I. INTRODUCTION
Seaports (hereafter ports) are traditionally viewed as an eco-
nomic springboard for the country development, since their ser-
vices and manufacturing activities create economic benefits and
socio-economic wealth via labor income, business earnings, taxes,
etc. (Park and Seo, 2016). Ports also have catalytic economic
and social impacts on their corresponding hinterlands. Over the
past years, advances in Information and Communication Tech-
nologies (ICT) have played a key role in transforming the way
they function. The successful transfer and implementation of
the actual ICT applications is a prerequisite for their greater
business achievements. However, port innovations cannot be
restricted to the adoption of new technologies, which have been
mostly ICT driven in the recent years. The so-called soft in-
novation is currently used to refer to non-technological dimen-
sions such as: people and organization, markets and relationships,
knowledge and integration, meanings and experiences (Martino
et al., 2013), etc. It seems that both technological and soft in-
novations can ensure a sustainable advantage to a port. The afore
remarked holds true for highly developed leading class ports,
but unfortunately not for the developing ones, e.g., the Port of
Bar in Montenegro. It has been operating for decades in a tran-
sitional environment and it combats with the lack of investments
and rigid administration structures, which permanently reproduce
crises and prevent its economic development. Through several
projects and research papers we have tried to at least enlighten
and merely alleviate these problems (Bauk, 2014; Bauk, 2015;
Bauk et al., 2015; Bauk at al., 2016). We have been focused on
conceiving and developing ICT models for enhancing on port
workers’ safety and uprising the level of their occupational cul-
ture. This paper provides a continuation in this regard, and it is
organized in the following manner: (i) it gives a short overview
in terms of how working on port can be dangerous; (ii) it con-
siders three available RFID solutions for reducing the workers’
safety risks; (iii) it presents some channel analysis in an OPNET
environment, while workers’ body central units (BCUs) and ac-
tive RFID identification (ID) badges are treated as moving end
nodes of the ZigBee network; (iv) it also analyses the channel
between the workers’ and/or pedestrians’ RFID active ID ba-
dges (tags) as end nodes, and forklift trucks’ (hereafter forklifts)
RFID warning systems as moving routers of the ZigBee net-
work. Finally, the paper gives some concluding remarks based
on the simulation experiments’ results, as well as directions for
further examinations in this domain.
II. ON PORT WORKING RISKS
Work at ports takes place throughout the day and night in all
weather conditions (HSE, 2011; HSE, 2013). It involves a num-
ber of different employers and contractors carrying out various
activities: harbor authorities, stevedoring firms, haulers, ship’s
P
aper submitted 04/19/16; revised 05/03/17; accepted 07/17/17. Author for
correspondence: Sanja Bauk (e-mail: bsanjaster@gmail.com).
1 Department of Maritime Studies, University of Montenegro, Montenegro.
2 E.T.S.I. de Telecomunicacion, UPM-Madrid, Spain.
3 UMIC Research Center, RWTH Aachen University, Germany.
12 Journal of Marine Science and Technology, Vol. 26, No. 1 (2018 )
masters, crews, etc. This requires a synchronized co-operation
and communication between all the involved parties. There
are frequent pressures to load or unload ship’s cargo quickly to
catch a tide or to free up a wharf for another ship; or, for example,
visiting drivers want to pick up or drop off their cargo as quickly
as possible and get back on the road.
Ports also tend to be associated with emerging environmental
problems (Darbra and Casal, 2004): water and air pollution,
soil contamination, problems related to dust and noise, genera-
tion of waste, dredging operations, warehouse storage of hazard-
ous substances, etc. Therefore, they can be dangerous places
especially for on port workers and/or pedestrians in terms of
operational risks connected to un-loading operations, managing
on port traffic and transportation, handling manipulative equip-
ment, warehousing dangerous cargoes (Roberts and Gray, 2013),
etc. All these make the port work challenging, but also highly
risky.
Under the regulations, both employers and employees in ports
must ensure the health and safety of themselves and others. In
developed ports, employers have specific obligations concern-
ing the provision and use of the Personal Protective Equipment
(PPE) by the employees who are exposed to risks. This is still
not the case in the Port of Bar, but it should become obligatory.
In this regard, within the following section we shall refer to
several PPE intelligent solutions proposed and/or employed in
highly developed harsh working environments. PPE can include
items such as safety helmets, gloves, eye protection, highly visi-
ble clothing, safety footwear, safety harnesses, etc., but it is com-
monly limited to the 3 Point PPE, i.e., helmet, safety vest and
protective shoes. Garments equipped with passive or active RFID
devices can help in identifying each protective piece, examining
its functionality and proper use. By a corresponding alarm
system, workers are alerted if some PPE garment is missing or
is not properly worn, or if some of the RFID tags embedded-
attached to the PPE do not function properly. Furthermore,
using active RFID ID badges allows smart back-end software
system monitoring the workers’ presence at the port, their ac-
cess to dangerous zones, and, in the case of emergency, the
workers can be alerted to come to the appointment place which
is well covered by the anchor readers. Thanks to the numerous
interrogators installed at strategic points of the appointment
zone, the workers can be automatically identified, located, and
the inspection of using and correctness of their PPE garments
can be carried out. Additionally, the RFID locating system can
be used for both the workers equipped with ID cards (i.e., ac-
tive RFID tags) and forklifts equipped with RFID light/audio
alerting system for warning the workers and/or pedestrians and
providing them with enough time to get themselves to safety.
These safety solutions will be described in some more detail
within the next section.
III. SOME PPE-RFID SAFETY SOLUTIONS
For the purpose of giving support to the managers of the de-
veloping Port of Bar in providing justification to their senior
management and stakeholders regarding a secure buy-in and
implementation of smart safety solution(s) for preventing and
reducing occupational risks, we described within this section
some of the previously mentioned smart PPE-RFID systems.
The first one is described at large in Barro-Torres et al. (2012).
However, it is still at the level of a prototype, with the inten-
tion to be implemented at construction sites. The second sys-
tem, which is presented here, is implemented in the North Sea
oil and gas industry (Vermesan, 2010), and the third one can be
implemented at a port or at any other industrial and transporta-
tion environment of high density. In any case, there are no severe
restrictions for implementing these solutions at any rough and
commercially intensive port environment whatsoever. Introduc-
ing the ZigBee network for establishing communication between
workers’, pedestrians’, and forklifts’ RFID enabled devices and
warning systems at the port perimeter, including port’s backend
info-communication system, might be considered as a novelty
of this paper in comparison with the previous research works
in this domain (Sole and Musu, 2013a; Sole and Musu, 2013b;
Musu, 2014; Sole, 2014; Musu, 2015; Bauk et al., 2016).
1. The RFID System for Monitoring the Use of PPE
This system is composed of a body area network (BAN) that
collects information from the readers located throughout the
workers’ clothing (Barro-Torres et al., 2012). The short range
RFID readers are located at strategic points within the clothing,
for checking the correctness of wearing 3 Point PPE. The de-
tection rate clearly increases when the antennas of the reader
and the tag attached to each 3 Point PPE garment are in parallel,
while it decreases dramatically when the antennas are oriented
orthogonally. To avoid the null spots, different alternatives
have to be weighted up in order to modify the antenna radiation
pattern. The central unit microcontroller (CUM) processes
data from the readers and transmits them by a radio module to
the ZigBee mesh network composed of the set of end nodes
(workers’ BANs), routers, and the coordinator. CUM contains
the XBee module for ZigBee communications. This module has
a transmitting power of 2 [mW] and works at 2.4 [GHz], while
its range varies significantly depending on the environment (tem-
perature, humidity, size, and material of obstacles). The coor-
dinator collects and stores the data coming from the end nodes,
configures the nodes and performs synchronization. The end
nodes are the critical part of the system. The scheme of this
scenario is given in Fig. 1. We do not recommend it to be im-
plemented in the Port of Bar at the present moment, since it is
complex, intrusive, and the central microcontroller is currently
in the developing phase. In any case, we believe it is worth pre-
senting to the management of the Port of Bar as a potential en-
vironmental safety solution, which might be adopted in the future.
2. Active RFID Tags and PEE
A cost effective RFID technology solution for locating and
tracking personnel in case of emergency situation was deployed
at oil and gas rigs in the North Sea in the first decade of 2000’s.
This system is conceived as an offshore emergency prepared-
S. Bauk et al.: A ZigBee/RFID Safety System at the Seaport 13
RFID
passive tag
E
C
R
E
R
R
G
R
E
E
Internet
RFID
short-range
reader
Fig. 1. Scenario 1: Worker’s BAN as an end node. (Legend: E-end node;
R-router; C-coordinator; G-gateway/coordinator).
ness system, rather than a personnel surveillance one. Its two
key components are RFID readers and tags. In the event of an
emergency, the system determines the current and past locations,
and the identities of all the personnel wearing an active RFID
tag (ID badge, or card) for the purpose of tracking. Naturally,
in addition to this emergency safety system, using PPE at oil and
gas rigs is obligatory. The extended version of the personnel
tracking system may also include the use of environmental sen-
sors, e.g., for temperature, humidity, gas detection, etc. In some
cases, the active ultra high frequency (UHF) Gen2 tags are in-
stalled onto the hard helmet of each worker. By installing RFID
readers at each entry gate of the floating ship or another enclosed
space, the system can track the number of persons on board. This
way the fire and security officials are provided with real-time
information on head count and are able to decide on the neces-
sary escape routes (Hild, 2007).
Platforms operating in an offshore environment typically em-
ploy hundreds of people. Some of them are connected via bridges
creating a center that can hold up to thousands of persons. Each
person on the rig has an RFID active ID badge which can be
worn around the neck, attached to the clothing or placed in the
pocket. The badge has a battery powered UHF tag working at
868 [MHz] (EU standard) and transmitting the ID number at
preset intervals. The tags can be read from the distance of up
to 500 [m]. Back-end software stores each worker’s name, shift,
job, education, etc., which is linked to the unique ID number
on the badge. When the reader captures the tag’s ID number, it
forwards that information via a wireless connection to a com-
puter, which can then pass on that data, either to the company’s
back-end server or to a server on-site via Wi-Fi or the Internet
connection (Swedberg, 2011).
We propose here the employment of the ZigBee mesh network
as a connector to the smart back-end control system, while the
end nodes would be the workers’ active RFID tags. Simplified,
the worker has an RFID active tag, while the router reads the
tag and sends the information to the ZigBee network. At the end,
the data arrive to the coordinator which is connected to a geo-
graphic information system (GIS) map (Grupo Autolog, 2010).
The basic scheme of this workers’ RFID safety scenario is given
in Fig. 2. If there are several readers on the site, the system can
determine each employee’s location, while the accuracy of the
RFID ID
badge
E
C
R
E
R
R
G
R
E
E
Internet
Fig. 2. Scenario 2: Worker’s RFID active ID badge as an end node. (Legend:
E-end node; R-router; C-coordinator; G-gateway/coordinator).
position depends on the number of readers used. The system ty-
pically tracks the zone of the employee’s presence, rather than
the worker’s specific location. The system also provides an alert-
ing function, in case certain personnel are not allowed to enter
one or more specific zones. Using active ultra-wideband RFID
tags, which operate at 3.1-10.6 [GHz], should allow for the de-
termination of the worker’s position with the precision of a few
inches (Roberti, 2013). However, such tags can be fairly expen-
sive, especially if we bear in mind the specific economic and
administrative working conditions of the Port of Bar. Therefore
we suggest using UHF active RFID ID badges for the workers’
identification and their locating within a certain zone or read
field within the range of about 5-10 [m].
3. The RFID Supported Forklift Warning System
Workplace accidents involving moving vehicles (e.g., forklifts)
cost ports huge amounts of money in terms of expensive down-
time, investigations and increased insurance premiums (Or-
bitcoms, 2016). Above all are fatal injuries and loss of human
lives. In 2014, e.g., the number of casualties in the transporta-
tion sector in the USA was 734, according to the Bureau of
Labor Statistics (Grayson, 2015). Fortunately, the fatal accidents
have not been recently recorded in the Port of Bar, but this should
not be excluded as a potential danger and should be prevented
anyway.
There are several ready made, commercial solutions for re-
ducing the risk of collision between moving vehicles and workers/
pedestrians at the workplace, such as: Forklift Safety RFID
Solutions (SPT, 2016), BodyGuard (Orbit, 2016), Pedestrian
Alert System (IcnitaSafety, 2016), EGOpro Safety Move Proxi-
mity Warning Systems (AME, 2016), etc. They all improve safety
through a proximity alert system for forklifts and workers/
pedestrians. The main operating features of these systems are:
the detection of workers/pedestrians in frontal (0.5-6.5 [m]),
back (0.5-6.5 [m]), and side area (up to 4 [m]) of the forklift in
operation to warn the forklift’s driver (while maximum detec-
tion range can be adjusted to smaller). They also alert the worker/
pedestrian by visual and/or audible alarms and automatically
reduce the speed or stop the forklift, while its maximum speed
is limited to 10 [km/h] (IcnitaSafety, 2016).
14 Journal of Marine Science and Technology, Vol. 26, No. 1 (2018 )
RFID
long-range
reader
R
C
R
E
R
R
G
R
E
E
Internet
Fig. 3. Scenario 3: Forklift’s RFID reader as a moving router. (Legend:
E-end node; R-router; C-coordinator; G-gateway/coordinator).
The systems help in overcoming the typical risks caused by
factors such as driver inattention, poor visibility (e.g., blind
entry/exit, warehouse aisles, etc.), worker’s non-compliance with
exclusion areas around vehicles, collision between a worker and
moving vehicle at a common working area, etc.
Through the simulation experiments (Section 5) we are con-
sidering the case when a forklift contains an RFID long-range
reader and an alerting system and is treated as a moving router
of the ZigBee network at the port area (Fig. 3).
IV. BLENDING ZIGBEE AND RFID
The ZigBee networks can collaborate with RFID devices to
enhance the reduction of battery power consumption, robustness,
extension of ranges, communication with applications and other
network devices, etc. In other words, an integrated ZigBee/
RFID system architecture has the performances of multiple ap-
plications and of more capability than stand-alone RFID pro-
ducts. It can deliver an extended range through multi hops and
considerable savings in power consumption when all the network
components are well coordinated. In the ZigBee/RFID system,
a ZigBee end device like a worker’s BAN, an active on port
worker’s ID badge and a forklift RFID warning system have
the ability of returning a unique identifier to a nearby scanning
reader. The ZigBee transceivers automatically form a mesh net-
work with any ZigBee transceiver in the range of the same net-
work ID and frequency range (Rubio, 2010; Abdula and Widad,
2011). The XBee product (Digi, 2016) is a radio frequency tran-
smission module programmed to be used as a ZigBee end device
with a transparent operation as an active RFID tag and receiv-
ing and transmitting capabilities in a wireless transmission phy-
sical layer. In the following simulation experiments we assumed
that the workers’ BANs composed of active/passive RFID de-
vices (Fig. 1 and Fig. 2) are end nodes of the ZigBee network
the features of which we analyzed. Also, we considered the fork-
lifts’ RFID sub network composed of a reader, warning devices,
and driver’s ID badge as a moving router of the analyzed ZigBee
mesh network on the port parameter (Fig. 3). Some of the re-
sults of the performed experiments in OPNET (Sahraei, 2009;
Saha, 2013; Kaur, 2014; Hammoodi et al., 2015) are presented
and discussed in the following section. In addition to improving
Berths
Berths
Mole
Coordinator
Fixed router
Forklift (moving router)
Worker (end-node)
L
egend:
Fig. 4. Layout of the Port of Bar container and general cargo terminal.
the on port workers’ and pedestrians’ safety, the ZigBee/RFID
systems can also be used for enhancing the building security
(Infanta, 2013), traffic flow management (Chao and Chen, 2014),
intelligent traffic control and patient monitoring for efficient
ambulance services (Suneesh, 2015), etc.
V. SIMULATION EXPERIMENTS AND RESULTS
The simulation experiments with the ZigBee network with
end nodes being the workers’ RFID sub networks, and moving
routers being the forklifts’ RFID warning systems sub network,
are performed in OPNET Modeler (Riverbed Modeler v.17.5.A)
on PC (Intel-Core™ i7, 2.50 GHz, 8GB RAM) over the layout
of the Port of Bar container and general cargo terminal which
covers the area of 650 350 [m2] (Fig. 4).
For the needs of the simulation experiments, the fixed routers
and the coordinator of the ZigBee network are set on the top of
the main warehouse buildings at the terminal, which are ap-
proximately 10 [m] high, in order to be higher than the container
blocks at the container yard. We used a mesh topology since it
generally has superior performances in comparison with star and
tree topologies (Mihajlov and Bogdanovski, 2011; Vats et al.,
2012; Vancin and Erdem, 2015).
Workers and forklifts are moving over the operational area
between wharfs and storage (warehousing) area. We suppose
that a worker’s speed is 2 [km/h], and the forklift’s speed is 10
[km/h]. The paths of the workers and forklifts are chosen ran-
domly. Since the Port of Bar has about 100 on port workers who
are allocated at seven terminals depending on the workload: (1)
container and general cargo terminal; (2) wood terminal; (3) ter-
minal for grains; (4) bulk cargo terminal; (5) container and ge-
neral cargo terminal; (6) liquid cargo terminal, and (7) passenger
S. Bauk et al.: A ZigBee/RFID Safety System at the Seaport 15
18
17
16
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
0 h 0 m 0 h 5 m 0 h 10 m 0 h 15 m 0 h 20 m 0 h 25 m 0 h 30 m 0 h 35 m 0 h 40 m
Fig. 5. Traffic received by coordinator for different on port scenarios.
terminal, we supposed (according to the usual turnover) that
mostly 18 workers might be engaged daily at the container and
general cargo terminal. Also, according to some previously made
consultations with port managers, we assumed that 2 forklifts
are usually in operation on the terminal daily. In order to get a
better insight into the simulation experimentsʼ results, we tested
the network for various combinations of the workers and fork-
lifts, e.g., for: (a) 4 workers and 1 forklift; (b) 9 workers and 1
forklift; (c) 13 workers and 2 forklifts, and (d) 18 workers and
2 forklifts. The main settings for the network end nodes are as
follows:
(1) Packet Interval Time: constant (1);
(2) Packet Size: constant (32);
(3) Start time: constant (30);
(4) Stop time: infinite; and,
(5) Transmition power: 5 [mW].
The forklifts, treated as moving routers, have the same appli-
cation traffic parameters, but the transmission power is greater,
i.e., it is 50 [mW]. The routers do not generate application traf-
fic. The coordinator is responsible for the configuration of the
network parameters. It sets the network topology (tree, star, or
mesh; here the mesh one), the number of children that each node
can have, the number of routers, the depth on the network tree,
it defines PAN, etc. The coordinator does not generate any
application traffic either, but will be the final destination for all
the application traffic generated in the end nodes.
Fig. 5 presents the traffic received by the coordinator in the
cases (c) and (d) at the frequencies 868 [MHz] and 2.45 [GHz],
respectively. It is obvious that the received traffic is about
12-18 packages per second for 2.45 [GHz], and that it is con-
0.50
0.34
0.32
0.30
0.28
0.26
0.24
0.22
0.48
0.46
0.44
0.42
0.40
0.38
0.36
0.20
0.18
0.16
0.14
0.12
0.10
0.08
0.06
0.04
0.02
0.00
0 h 0 m 0 h 5 m 0 h 10 m 0 h 15 m 0 h 20 m 0 h 25 m 0 h 30 m 0 h 35 m 0 h 40 m
Fig. 6. End-to-end delay for 868 [MHz] carrier’s frequency.
0.18
0.16
0.14
0.12
0.10
0.08
0.06
0.04
0.02
0.17
0.15
0.13
0.11
0.09
0.07
0.05
0.03
0.01
0.00
0 h 0 m 0 h 5 m 0 h 10 m 0 h 15 m 0 h 20 m 0 h 25 m 0 h 30 m 0 h 35 m 0 h 40 m
Fig. 7. End-to-end delay for 2.45 [GHz] carrier’s frequency.
siderably lower, i.e., it is between 6-9 packages per second for
868 [MHz]. This is due to the increased performances that we
have in the 2.45 [GHz] band, compared to 868 [MHz], such as
the data rate, the number of channels, or the use of more effi-
cient modulation protocols. We may also remark that each end
node sends the traffic each second, therefore some packet losses
are acceptable, as long as not all the data from one worker is
completely lost.
Figs. 6 and 7 present end-to-end delays for (a), (b), (c), and (d)
scenarious, for 868 [MHz] and 2.45 [GHz] carrier frequencies.
16 Journal of Marine Science and Technology, Vol. 26, No. 1 (2018 )
1.00
0.60
0.55
0.50
0.45
0.40
0.35
0.30
0.95
0.90
0.85
0.80
0.75
0.70
0.65
0.25
0.20
0.15
0.10
0.05
0.00
0 h 0 m 0 h 5 m 0 h 10 m 0 h 15 m 0 h 20 m 0 h 25 m 0 h 30 m 0 h 35 m 0 h 40 m
Fig. 8. Traffic received by destination from different routers and end nodes
at 868 [MHz].
It is clear that the delay is consideralby lower for 2.45 [GHz]
than for 868 [MHz]. More precisely, in the better case (at 2.45
[GHz]) it is about 0.07-0.16 seconds, while in the worse one
(at 868 [MHz]) it is about 0.12-0.44 seconds. This happens
because the data rate increases at 2.45 [GHz], and because of the
more efficient QPSK modulation scheme used (in comparison
with BPSK one).
It is also interesting to consider the traffic received by destina-
tion, i.e., network coordinator from certain end nodes (workers)
or moving routers (forklifts) as it is shown in Figs. 8 and 9. The
traffic received by destination reaches 1 package per second
for 2.45 [GHz] and 0.75 package per second for 868 [MHz].
Although the received traffic has oscillations which mostly de-
pend on the distance between the end nodes and/or moving routers
from the destination within the time interval covered by the simu-
lation period, there is no permanent interruption in receiving.
This is of particular importance.
The simulations were performed for the actual number of
workers and forklifts usually employed per shift based on the
workload on the container and general cargo terminal in the
Port of Bar. In the forthcoming analysis, a larger number of
workers and mobile mechanization units should be involved in
order to confirm the experimental ZigBee technology function-
ality for a greater number of network nodes, i.e., its reliability
and scalability. Furthermore, the impacts of different obstacles
and environmental parameters should also be analyzed. The on
port workers’ readiness to become constitutive parts of the pro-
posed smart safety solutions is to be examined, as well. All these
should assist the managers in making the port safer and greener
at the global market of un-loading, manipulation, transportation,
and various added-value services.
1.15
0.75
0.7
0.65
0.6
0.55
0.5
0.45
1.1
1.05
1
0.95
0.9
0.85
0.8
0.4
0.35
0.3
0.2
0.1
0.25
0.15
0.05
0
0 h 0 m 0 h 5 m 0 h 10 m 0 h 15 m 0 h 20 m 0 h 25 m 0 h 30 m 0 h 35 m 0 h 40 m
Fig. 9. Traffic received by destination from different routers and end nodes
at 2.45 [GHz].
VI. CONCLUSION
The paper presents a continuation of the previous authors’
research work (Bauk et al., 2015; Bauk et al., 2016) and at-
tempts towards repositioning the Port of Bar at the market of
safety ports. It considers the RFID based occupational safety
solutions in ports and other similar harsh environments and
proposes the RFID system co-work with ZigBee technology in
a satisfactory and efficient way for the purpose of enhancing
the on port workers/pedestrians safety. The ZigBee was ana-
lyzed as a communication technology because it provides low
energy consumption, a larger range, and it works properly with
quite a large number of end devices. An XBee module was pro-
posed as a link between the workers’ and forklifts’ RFID sub net-
works and ZigBee communication channel. The simulations are
focused on the ZigBee performances over the Port of Bar con-
tainer and general cargo terminal. They were realized in OPNET
(Riverbed Modeler v.17.5.A) environment, while the following
have been obtained:
(1) As the number of end-nodes increases (from 15 to 20), the
traffic received by the coordinator decreases (from about
12 to 7 packages per second), but there are no interruptions
such as the coordinator not receiving any traffic at all;
(2) The experiments show that the performances of the ZigBee
network are in general significantly better at 2.45 [GHz]
than in the case of 868 [MHz] carrying frequency. This is due
to the greater data rate at 2.45 [GHz], greater number of avai-
lable channels, more efficient modulation schemes, etc.;
(3) Better performances at 2.45 [GHz] than at 868 [MHz] are
noticed when it comes to the number of packages received
by the coordinator per second, and when it comes to the
end-to-end delay of the received signal;
S. Bauk et al.: A ZigBee/RFID Safety System at the Seaport 17
(4) The number of packages received by the destination (co-
ordinator) from different routers and end nodes varies de-
pending on the current location of these devices. It is greater
in the case of using 2.45 [GHz] than 868 [MHz]; and,
(5) Concerning the received power, it is in all the cases higher
than the power reception sensibility threshold, which is the
minimum reception power needed by the receiver. In all
our scenarios, it was set to -85 [dBm] to all the devices.
The experiments were done for the real number of workers
and forklifts being commonly in operation at the Port of Bar
container and general cargo terminal. They show a completely
satisfying level of the ZigBee network performances. In our si-
mulation experiments we assumed that the ZigBee end nodes
and moving routers are RFID sub networks joint to the ZigBee
via XBee modules. In the forthcoming research, a larger number
of end nodes and routers should be involved. Additionally, some
more detailed explanations of connecting possibilities for RFID
and ZigBee technologies are to be considered.
Our goal here was to familiarize the managers and stakeholders
of the developing Port of Bar, operating in a transitional eco-
nomy, with contemporary ICT solutions which might be adapted
for improving the safety of human lives and environmental
management system. Since the industrial safety systems use a
whole panoply of technologies, our intention was not to offer
the best solution, but just to open a discussion about cost and
energy effective and, at the same time, reliable occupational
safety measures. It is upon the port’s management to develop
strategies for their implementation in the future, with the ulti-
mate goal of protecting the on port workers’/pedestrians’ lives
and maritime ecosystem. These should promote the Port of
Bar in the future as safe and green at the maritime market and
upgrade its current position at the customers’ perception maps.
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