Journal Editorial Board Editor-in-ChiefProf. Thomas Byeongnam YOON, PhD.
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Copyright ⓒ 2015 GiRI (Global IT Research Institute)Dr. Youssef SAID, Tunisie Telecom, Tunisia
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Copyright ⓒ 2015 GiRI (Global IT Research Institute)Dr. Il Kwon Cho, National Information Society Agency, Korea
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Prof. Li-Der Chou, National Central University, Taiwan
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Prof. Dimiter G. Velev, UNWE(University of National and World Economy), Bulgaria
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Dr. Brownson ObaridoaObele, Hyundai Mobis Multimedia R&D Lab , Korea
Prof. Anisha Lal, VIT university, India
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Prof. Chwen-Yea Lin, Tatung Institute of Commerce and Technology, Taiwan
Dr. Ting Peng, Chang'an University, China
Prof. ChaeSoo Kim, Donga University in Korea, Korea
Prof. kirankumar M. joshi, m.s.uni.of baroda, India
Dr. Chin-Feng Lin, National Taiwan Ocean University, Taiwan
Dr. Chang-shin Chung, TTA(Telecommunications Technology Association), Korea

Copyright ⓒ 2015 GiRI (Global IT Research Institute)Dr. Che-Sheng Chiu, Chunghwa Telecom Laboratories, Taiwan
Dr. Chirawat Kotchasarn, RMUTT, Thailand
Dr. Fateme Khalili, K.N.Toosi. University of Technology, IranDr. Izzeldin Ibrahim Mohamed Abdelaziz, Universiti Teknologi Malaysia , Malaysia
Dr. Kamrul Hasan Talukder, Khulna University, Bangladesh
Prof. HwaSung Kim, Kwangwoon University, Korea
Prof. Jongsub Moon, CIST, Korea University, Korea
Prof. Juinn-Horng Deng, Yuan Ze University, Taiwan
Dr. Yen-Wen Lin, National Taichung University, Taiwan
Prof. Junhui Zhao, Beijing Jiaotong University, China
Dr. JaeGwan Kim, SamsungThales co, Korea
Prof. Davar PISHVA, Ph.D., Asia Pacific University, Japan
Ms. Hela Mliki, National School of Engineers of Sfax, Tunisia
Prof. Amirmansour Nabavinejad, Ph.D., Sepahan Institute of Higher Education, Iran

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Copyright ⓒ 2015 GiRI (Global IT Research Institute)Journal Procedure
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Copyright ⓒ 2015 GiRI (Global IT Research Institute)Journal Submission Guide
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Copyright ⓒ 2015 GiRI (Global IT Research Institute)Volume. 4 Issue. 5

1

A Cell Biology Inspired Model for Managing Packet Broadcasts in Mobile Ad-hoc Networks

6J

664

Sulochana J. Sooriyaarachchi*, Anil Fernando*, Chandana D. Gamage**Department of Computer Science and Engineering, University of Moratuwa, 10400, Sri Lanka, **Centre for Vision Speech and Signal Processing (CVSSP),
Faculty of Engineering and Physical Sciences, University of Surrey, Guildford, Surrey, GU2 7XH

2MPEG-SCORM: an Ontological Approach of Interoperable Metadata for Digital Television and e-Learning

673

Marcelo Correia Santos, Yuzo Iano
Department of Telecommunications of the Electrical and Computer Engineering School, UNICAMP (São Paulo State University of Campinas) Campinas-SP,
Brazil 13083-852

3

APEM: Automatic paraphrase evaluation using morphological analysis for the Korean language

680

Sung Won Moon*, Gahgene Gweon*, Hojin Choi**, Jeong Heo****Dep. Of Knowledge Service Engineering, KAIST, Daejeon, Rep. Of Korea, ** Dep. Of Computer Science, KAIST, Daejeon, Rep. Of Korea, *** Knowledge
Mining Research Team, ETRI, Daejeon, Rep. Of Korea

4

Fault Resilient Communication Network Architecture for Monitoring and Control of Wind Power Farms

685

Young-Jae Lee*, Eung-Kon Kim*
* Department of Computer Engineering, Chonbuk National University, Jeonju 561-756, South Korea, ** Smart Grid Research Center, Chonbuk National
University, Jeonju 561-756, South Korea

5

A Practical RFID Grouping Authentication Protocol in Multiple-Tag Arrangement with Adequate Security Assurance

693

Jian Shen* ** *** ****, Haowen Tan****, Yongjun Ren****, Qi Liu****, Baowei Wang*****Jiangsu Engineering Center of Network Monitoring, Nanjing University of Information Science & Technology, China, **Jiangsu Technology & Engineering
Center of Meteorological Sensor Network, Nanjing University of Information Science & Technology, China, *** Jiangsu Collaborative Innovation Center on
Atmospheric Environment and Equipment Technology, Nanjing University of Information Science & Technology, China, **** School of Computer & Software,
Nanjing University of Information Science & Technology, China

Copyright ⓒ 2015 GiRI (Global IT Research Institute)

ICACT Transactions on Advanced Communications Technology (TACT) Vol. 4, Issue 5, September 2015

664

A Cell Biology Inspired Model for Managing
Packet Broadcasts in Mobile Ad-hoc Networks
Sulochana J. Sooriyaarachchi∗ , Anil Fernando∗∗ , Chandana D. Gamage∗∗ Department of Computer Science and Engineering, University of Moratuwa, 10400, Sri Lanka∗∗ Centre for Vision Speech and Signal Processing (CVSSP), Faculty of Engineering and Physical Sciences,

University of Surrey, Guildford, Surrey, GU2 7XH
sulochanas@cse.mrt.ac.lk, w.fernando@surrey.ac.uk, chandag@cse.mrt.ac.lk

Abstract—The modern computing paradigm is moving towards
personal devices that incorporate wireless networking, mobility, and collaborative applications. The networking paradigm
that best matches this scenario is the mobile ad-hoc network(MANET). A common instance of a MANET is the dense
MANET that can be expected in any setting where large numberof people congregate such as movie theatres, sports stadiums,
shopping malls, transportation hubs, lobby of public offices,
lecture rooms, etc. The existing packet transmission protocols
for MANETs are inefficient for dense MANETs due to packet
broadcast storms for stateless protocols and non-availability ofanchor nodes for stateful protocols. This paper presents a new
packet broadcast model developed based on cell biology andprovides simulation results on protocol efficiency. As smart phonedevices and collaborative applications proliferate among users,
the proposed dense MANET protocol could provide real benefits
to Internet enabled users and devices.
Index Terms—Mobile ad-hoc networks, Packet broadcasts,
Cellular automata.

I. I NTRODUCTIONT

HE current trend in day-to-day communication of averagepeople is towards the intensive use of mobile devices
such as smart phones and slate type computers. These devices
are generally capable of connecting via cellular networks,
WiFi or Bluetooth. The abundance of such portable communication devices with wireless capabilities gives rise topotential ubiquitous computing experiences. For example a
traditional classroom can be converted into a collaborative
learning environment via a stand-alone ad hoc network ofmobile phones. Another application would be for friends
roaming in a shopping mall to detect each other and shareideas using an on-the-fly ad hoc network without the supportof cellular networking infrastructure or WiFi hotspots in the——————————————————————————–
Manuscript received May 30, 2015. This work is a follow-up of the invitedjournal to the accepted out-standing conference paper of the 17th International
Conference on Advanced Communication Technology (ICACT2015).
S. J. Sooriyaarachchi is with the Department of Computer Scienceand Engineering, University of Moratuwa, 10400, Sri Lanka, (corresponding author, phone: +94112640380, fax: +94112650912, e-mail: sulochanas@cse.mrt.ac.lk)
W. A. C. Fernando is with the Centre for Vision Speech and Signal
Processing (CVSSP), Faculty of Engineering and Physical Sciences, University of Surrey, Guildford, Surrey, GU2 7XH, (phone: +441483682353, fax:
+441483686031, e-mail: w.fernando@surrey.ac.uk)
C. D. Gamage is also with the Department of Computer Science and Engineering, University of Moratuwa, 10400, Sri Lanka, (phone: +94112640380,
fax: +94112650912, e-mail: chandag@cse.mrt.ac.lk)

arena. In this research we focus on a dense network of such
mobile devices that could be visualized as a dense Mobile
Ad-hoc Network (dense MANET).
MANETs are generally dynamic in terms of topology thus
making it challenging to device a routing mechanism. Thereis added complexity into routing when these MANETs aredense in nature. For example the routing tables maintained in
mobile nodes with the existing routing schemes such as AODV,TORA and DSR will become unmanageably large in size andthe network will get overloaded with flooded control packets.
Therefore, it is essential that the nodes in a dense MANET
keep less or no state information, specifically pertaining to
global network and even the neighboring nodes. It is also
important that the nodes send the least amount of control
packets to conserve resources such as battery life. Due tothe unavailability of a suitable routing mechanism the users
have to rely on cellular networks without utilizing the powerfulnear-field communication technologies such as Bluetooth evenwhen the devices are at line of sight.
Blind rebroadcasting is the simplest form of packet routingthat allows the nodes to be stateless. Consequently, there ishigh probability that the intended destination will receive thepacket. However, this scheme will cause broadcast storms,
thus, resulting in severe degradation in performance, scalability and efficiency. Hence our aim is to find a mechanism
to send a data packet from one node to another in a dense
MANET while minimizing broadcast storms and leaving thenodes to be stateless. However, this is a difficult problem.
Biological inspirations have given promising results in arriving at satisfactory solutions for difficult problems similar
to above, especially in communication networks. For instance
Wedde et.al proposes an energy efficient routing algorithm
known as BeeAdHoc for MANETs inspired by the foraging
principles of honey bees to address the energy dilemma in
MANETs [1]. Gunes et.al in [2] addresses the issue of packet
overhead in routing and proposes Ant-Colony-Based Routing Algorithm (ARA) inspired by swarm intelligence in ant
colonies. Similarly a number of studies base their solutions on
ant colony optimizations [3], [4]. Moreover, Sarafijanovic and
Boudec address the problem of node misbehavior in MANETs
and gain inspirations from the human immune system for theirsolution [5]. Similarly, Kefalas et.al bases their solution for the
problem of modeling dynamic behavior of multi-agent systems
on the evolution of human tissues [6].

Copyright ⓒ 2015 GiRI (Global IT Research Institute)

ICACT Transactions on Advanced Communications Technology (TACT) Vol. 4, Issue 5, September 2015

There are biological systems that show similar
characteristics of a dense MANET that tries to achieve
a common task by cooperating among autonomous entities.
An organ in human body for instance is also made out ofa dense population of biological cells. These cells divide
themselves repetitively in the process called cell proliferationand that is analogous to re-broadcasting of packets in a
MANET. It is an interesting question to ask “On what basis
our ears end up growing into a particular size?”. The nature
has its regulatory mechanisms for controlling the cell divisionin an organ. These biological regulatory mechanisms would
inspire us in finding a mechanism to manage redundantbroadcasts in a dense MANET with a simple rebroadcasting
scheme.
II. R ELATED W ORKThis section briefs the routing approaches available in thearea of MANETs and how our approach differs.
A. Traditional Approaches
Traditional routing approaches proposed and implemented
in MANETs are based on existing routing protocols of wired
networks. Data communication networks originated with theintention of connecting fixed wired terminals. Need for routing
mechanisms arose as a result of the growth of the networks bysize and geographical spread. The networks started to support
wireless nodes with the intension of using existing communication networked resources [7]. Hence, the wireless nodes
always had the support of some kind of fixed infrastructureso that the then-existed wired routing protocols were tweakedand customized to support a few number of wireless nodes.
Dedicated fixed infrastructure were implemented such as basestations in cellular networks and wireless access points in local
area networks when the mobile nodes increased in number[8]. However, the concepts behind almost all routing protocols
used in MANETs are hooked to fixed infrastructure at leastby assuming few key nodes in the network to act as fixed androuting nodes. The most recent work in the area of MANETs
is IEEE 802.11s which defines MANETs as Wireless Mesh
Networks. Mesh Stations even in IEEE802.11s standard act as
Access Points in infrastructure mode wireless networks thus
managing routing and control [9]. We consider the routing
paradigm that bases on fixed infrastructure and requires tomaintain routes as the fixed-stateful approach.
However, the current trend in MANETs seeks a paradigm
shift in approaching the problem of routing as various mobile
devices emerge in large numbers and with powerful near-field
wireless networking capabilities. In parallel the supporting
technologies and concepts for ubiquitous computing and connectivity develop at a rapid phase. For example IPv6 allow
a large population of mobile devices to connect in a single
network, while WiFi and Bluetooth provide powerful near fieldcommunication. Hence we seek routing mechanisms that baseon the other extreme in contrast to fixed-stateful paradigm intraditional MANET routing. So we dare to take the oppositeof the traditional routing paradigm and bases our solution on
the mobile-stateless approach.

665

B. Mobile-stateless Routing Paradigm
A comparison of our approach and the traditional approaches of MANET routing is summarized in figure 1. The
simplest and stateless mechanism of sending a packet from
one node to another in a MANET is blind-rebroadcasting.
In this mechanism a node re-broadcasts each and every
packet it receives, except for those destined to the node
itself. However, it causes unnecessary amount of redundantrebroadcasts especially when the MANET is dense. Hence
we base our solution on blind-rebroadcast and try to reduce
redundant rebroadcasts using biologically inspired regulatory
mechanisms. These regulations in turn requires us to maintaincertain amount of states thus shifting our approach slightly
towards stateful side. Consequently, our approach is placed at
a position shown in figure 1 rather than at the mobile-statelessextreme. However, the states maintained in our approach does
not gather global information from nodes network-wide as intraditional routing approaches. Information that our approachrequires is of itself and immediate neighborhood along withthose carried by the received data packets.
Although there are routing protocols proposed based on cellbiological inspirations, such as in [10] they also base theirsolution on existing AODV-like protocols and maintain routing
tables while not considering node densities. Cellular Automata
based models are also found as in [11] and [12] for mobile
networks but they are not in the scope of dense MANETs or
related to routing as in our work.
C. Network wide Reach in MANETs
It is often essential that the packets should be sent to every
node in a MANET, at least for house keeping tasks such as
discovering routes and updating routing tables in traditional
MANET routing. For example, AODV which is the mostpopular routing protocol in MANETs, relies on Sequence
Number Controlled Flooding as the mechanism to send RREQ
packets throughout the network [13]. IEEE802.11s also uses
AODV as the routing protocol [14]. Hence flooding is a
decisive aspect of MANETs. The initial idea for our work was
intended to route data packets based on blind rebroadcasting or
on flooding. However, the findings are applicable in enhancing
the available routing protocols which rely on some kind offlooding to reach all nodes in a network. Hence this work canalso be considered as a contribution to the improvement offlooding in MANETs.
III. B IOLOGICAL I NSPIRATIONSThis section explains the biological inspirations for limiting
the packet rebroadcasts in a MANET based on biologicalliterature related to organ growth.
A. Limiting the Packet Growth inside the MANET
Our aim was to control the growth of the number ofrebroadcasts of a data packet inside the MANET with theinspiration from the organ growth control by inhibition ofcell proliferation. Since a human organ is generally made outof millions of cells it is an ideal system to mimic the dense

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666

Fig. 1. Summary of comparison of our routing approach with reference to fixed-stateful and mobile-stateless routing paradigms

nature of the mobile network of our interest. Any regulatory
mechanism that controls the cell proliferation in the growthof such organs would be a candidate biological inspiration to
manage broadcast storms in the target network.
According to Lui and Baron [15], the human body has a
growth deceleration mechanism driven at the physiologicallevel by growth itself and at a molecular level by a cell intrinsic
genetic program. This claim is supported by the authors in[16]. Lui and Baron in [15] further elaborate that the local
communication mechanisms play the central role in growth
deceleration rather than the systemic mechanism. Bryant andSimpson in [17] also highlight the evidence for organ intrinsic
mechanisms in growth control in organs. However, the growth
deceleration program is not cell autonomous but it depends
on the interaction of the cell with the extra-cellular microenvironment [15].
B. Using Growth as the Inhibitor of Growth
The genetic program explained in [15] is responsible for
growth inhibition according to the inputs related to growth
itself such as the number of accumulated cells, organ functionality and the number of cell divisions undergone. This
genetic program up or down-regulates growth promoting genes
according to a negative feedback loop. The hypothesis thatthe growth itself causes growth inhibition is also proved by
Forcinito et.al in [18].
C. Terminal Conditions
According to the authors in [15] the Growth Program
described above down-regulates the growth-promoting genes
when (i) the accumulated number of cells reach the saturationlevel, (ii) the organ is adequately grown to perform the intended functionality or (iii) the number of divisions undergone
is equal to the particular number set during the embryonicstage.
D. Growth Sensing Mechanisms
Individual cells sense the growth in terms of number ofaccumulated cells by means of the concentration of somesecreted molecules known as chalones [15]. Bullough [19]coined the term chalone and hypothesized it as the inhibitorsof cell growth by negative feedback to control the size of atissue. A number of studies provide experimental evidence insupport of this hypothesis [20], [21], [22], [23]. Growth interms of the level of functionality is sensed for example in theliver by flux of bile acids. Bile acids are synthesized in liverand secreted into small intestine to facilitate digestion. Bile
acid is then reabsorbed and returned to liver. The number ofcell divisions undergone is measured using cell cycle counting
mechanisms such as telomere shortening [15].
IV. C ELL B IOLOGY I NSPIRED PACKET T RANSMISSIONM ODELOur work at the current stage is heavily inspired by thechalone method of growth inhibition in biological organ
growth explained in section III-D. This section explains how
we apply the chalone mechanism in order to limit the packet
rebroadcasting in MANETs.
The number of packets in our MANET grows by rebroadcasts in analogy to the cells that proliferate by dividing
themselves. Hence we map a data packet residing in a mobile
node, to a biological cell in an organ. Also the packet rebroadcasting is mapped to biological cell division. Similar tothe case that the biological cell has the growth-controllinggenetic program running inside itself the broadcast-controlling
program runs in the mobile node that contains a packet. Table I
summarizes the mapping from biological system to MANETs.
The chalone concentration sensed by a cell in its microenvironment represents the number of cells in the neighborhood in the biological system. Similarly we map chalone
concentration to the number of neighbors who have alreadybroadcast a particular data packet. We borrow the term chalone
for the control packets that we introduce as cues for carrying
information about the neighborhood in MANETs. Thereby weintroduce a set of control packets that are never forwarded
beyond the transmission range of a node. A node that receives
a data packet obtains information in order to decide whether torebroadcast the packet. The information requested is whether

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ICACT Transactions on Advanced Communications Technology (TACT) Vol. 4, Issue 5, September 2015

TABLE IS UMMARY OF M APPING FROM B IOLOGICAL S YSTEM TO MANET
Biological System

MANET

Biological cell

Data packet in a node

Cell division

Packet rebroadcasting

ChaloneA control packet exchanged onlywith the neighbors. Neighbors are thenodes within the transmission range ofa node.

Chalone concentration

Number of neighboring nodes who
have already broadcast the Data
Packet.

Chalone threshold

Threshold for the number of neighboring nodes who have already broadcast
the Data Packet for rebroadcasting.

Organ maturity

The state that the Data Packet reached
its destination.

the neighbors have already rebroadcast the particular data
packet in hand. We name the control packet that does theabove request as chaloneInit to denote the initiation of chalone
mechanism. The control packet sent by neighbors in responseto chaloneInit is named Chalone packet.
V. T HEORETICAL M ODEL
A. Operational Model based on Cellular Automata
Typically cell biological systems are modeled in terms of
Cellular Automata as in [24], [25], [26], [27]. In analogy the
biologically inspired MANET model is theoretically analyzed
based on Cellular Automata in this section.
Cellular Automata (CA) are defined as mathematical idealization of problems or physical systems in which space
and time are discrete and the physical values take on finite
set of discrete values [28]. This was invented by John von
Neumann in 1940s as a result of biological motivation with anintention to design self-replicating artificial systems. Power of
CA lies in its fundamental properties that are also found in thephysical world: CA are massively parallel, homogeneous andall interactions are local [29]. Therefore a variety of physicaland biological systems have successfully been modeled andsimulated using CA [30], [25], [31], [32], [33].
One-dimensional two-state CA is extensively elaborated in[28]. Formalism of CA is found in [34] for multi-dimensions
which is an exhaustive algebraic treatment of the subject. The
type of CA of our interest is two-dimensional as the nodes in
the MANET lie effectively on a plane. Authors in [35] further
analyze two-dimensional CA and cites [34] for additive twodimensional CA. According to [35], a two-dimensional CA
consists of a regular lattice of sites. Each site takes on k
possible values. Each site is updated in discrete time steps
according to a rule φ that depends on the values of sites
in some neighborhood around it at the previous time step.
Authors in [35] addresses the special class of φ known as
totalistic rules in which the values of a site depends only on
the sum of values of the neighbors.
Our CA model of MANET is also viewed as a regularlattice on which mobile nodes are randomly placed. Each sitetakes only two values: 1 - node has rebroadcast a specified

667

data packet, 0 - otherwise. Neighborhood for our CA is thecircular region captured by the radio range of a mobile node.
Any node within the range will respond as a neighbor. We
also apply totalistic rule in which we count the total numberof neighbors who have rebroadcast a specified data packet.
We set a threshold for this number so that a node decides
to rebroadcast a received data packet only if the number ofneighbors who have already rebroadcast the packet does notexceed the threshold. This threshold will be referred to as
chalone threshold hereafter.
B. Graph based Evaluation Model
We also assess the reachability of our protocol against thatof flooding. As our protocol suppresses broadcasts using athreshold value there is a possibility that the data packet may
not be received by certain nodes in the network. However
flooding will make sure that all nodes in an unpartitioned
network will receive a broadcast message.
In order to assess reachability we model the MANET asa unit disk graph of the following manner: vertices are themobile nodes and the edges denote the availability of a direct
wireless link between nodes at a given point in time. We
first take the Euclidean distance between every node pair andthen determine the immediate neighborhood by considering
the transmission ranges. It is analogous to superimposing thecommunication ranges of nodes on the physical location mapof the network. The graph may also change as the nodes
connect or disconnect due to mobility, user actions or power
availability.
In order to evaluate reachability of the resulting graph,
we use Floyd-Warshall algorithm for its simplicity, parallel
computation for all node pairs, and less pre-processing needs.
If a path can be found by the algorithm then we can conclude
that a node can reach any other node by simple flooding.
VI. S IMULATION
We used OMNET++ 4.4 with inet-2.2.0 for our simulation.
OMNET++ is an event-driven and modular simulation framework [36].
The simulation model under study comprises an array ofhosts configured as nodes of a single private network. The
number of nodes is specified as a parameter at runtime as directed by the omnetpp.ini configuration file. We identify a data
packet uniquely by its source address and a sequence number
which in combination referred to as Packet ID hereafter. The
sequence number is assigned to a packet by the originator ofthat packet. A node maintains a list of Packet IDs it sees orit creates. It also keeps a list of neighbors who responds for achaloneInit Message. When a node receives a data packet theflow of events occurs as given in figure 2.
On the receipt of a chaloneInit message the source node
ignores it while the destination is supposed to initiate anothertype of negative feedback mechanism similar to mechanism(ii) given in section III-B. However, the feedback mechanism
is not in the scope of this paper. Flooding is for the global
broadcast in a MANET in typical routing mechanisms andthe terminal condition is when a packet reaches all the nodes

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668

Fig. 2. Event flow at a receipt of a data packet by a nodeFig. 3. Performance of Cellular Automata based Rebroadcasting (CA) protocol compared with Blind Rebroadcasting (Blind) and Sequence Number Controlled
Flooding (SNCF)

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ICACT Transactions on Advanced Communications Technology (TACT) Vol. 4, Issue 5, September 2015

50mX50m and range 50m th3

30

30

20

20

rebroadcasts

rebroadcasts

30mX30m and range 30m th3

10

0

0

10

20

30

10

0

40

0

10

20

Euclidean distance

20

20

10

20

40

60

80

100

0

120

0

10

20

40

20

rebroadcasts

rebroadcasts

30

20

20

30

30

40

50

60

130mX130m and range 30m th3

50mX50m and range 30m th3

10

60

Euclidean distance

60

0

50

10

Euclidean distance

040

100mX100m and range 30m th330

rebroadcasts

rebroadcasts

100mX100m and range 50m th3

030

Euclidean distance

30

0

669

40

50

10

0

60

0

20

Euclidean distance

40

60

80

Euclidean distance

150mX150m and range 30m th3

150mX150m and range 50m th3

20

30

rebroadcasts

rebroadcasts

15

10

20

10

5

0

0

20

40

60

Euclidean distance

80

0

0

20

40

60

80

100

120

140

Euclidean distanceFig. 4. Number of rebroadcasts Vs distance between node pairs

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ICACT Transactions on Advanced Communications Technology (TACT) Vol. 4, Issue 5, September 2015100

transmission ranges
threshold values

Value
15
30m×30m,
50m×50m,
100m×100m and 150m×150m
30m and 50m
1,2,3 and 4

at least once. For unicast the terminal condition is reachedwhen the packet reaches its intended destination. The negative
feedback initiated by destination therefore is supposed toreduce the redundant rebroadcasts upon reaching the terminal
condition at unicast in a MANET. Nodes other than the source
and the destination that receive a chaloneInit would respondwith a Chalone message. Chalone message carries the neighborstate defined in section V.
In this paper we investigate the case of unicast by specifying
a source node and a destination for a data packet, thus the
success of a transmission is indicated when the packet reaches
the destination. We compare blind-rebroadcasting, sequencenumber controlled flooding and cellular automata based rebroadcasting in Section VII.
We test whether the reachability depends on node densities
and chalone threshold. We first set the chalone threshold at 3
and assess reachability for different node densities by placing
15 nodes randomly on maps of different sizes and changing
the transmission ranges as given in table II. Values for transmission ranges were selected based on commonly operational
distances of commercial WiFi products. The node placement
was decided based on common application scenarios for dense
and extremely-dense MANETs.
VII. R ESULTS AND D ISCUSSION
Performance metric for the protocol evaluation is the number of times a particular data packet is received by all
the nodes in the MANET until the specified destination isreached. The scenario at startup is for the MANET to havea single data packet originated by the specified source node.
Figure 3 illustrates the obtained results for the comparison of
the proposed protocol (CA protocol) against simple flooding(SNCF) and blind rebroadcasting for different node densitiesof the MANET. The reachability is assessed in terms of theratio between the number of node pairs reached using theprotocol and the theoretically reachable number of node pairs.
According to figure 3 the CA protocol outperforms bothblind rebroadcasting and SNCF for all node densities. For
example in a MANET with 50 nodes, blind rebroadcast caused
the network to reach the same packet 206 times while SNCF
recorded 104 times. CA protocol however reported only 23
times. Thus the CA protocols saves nearly 90% of redundantrebroadcasts compared to blind rebroadcasting whereas thesaving is nearly 80% compared to SNCF. Also for node densityof 100, the counts were: more than 80000 packets for blind
rebroadcasting, 451 for SNCF and just 49 packets for CA
protocol. Blind rebroadcasts are unacceptable for MANETs
beyond 100 nodes in terms of redundant rebroadcasts as thegrowth of the curve is steeply exponential. Though SNCF is

Reachability (%)

TABLE IIS IMULATION PARAMETERS
Parameter
number of nodes
playground sizes

670

80
60
40
20
0

0

1

2
3
4
Chalone threshold

5

Fig. 5. Reachability as a percentage of node pairs reached with respect totheoretically reachable number of node pairs for the case of 150mX150m andrange 30m

better compared to blind rebroadcasting, it does not perform
acceptably beyond 600 node density. CA on the other handshows a slow growing curve thus making it a better protocol
for all node densities shown. Further analysis into the CA
protocol alone for higher node densities such as 2000 nodes
proves the satisfactory performance and the usability of our
protocol in dense MANETs as the number of redundantrebroadcasts has linear and slow growth against node density.
According to figure 4 it was observed that in a map of
30m×30m with range of 30m and 50m×50m with rangeof 50m the data points show similar clustering. Hence wedefine the case of map sizes of r × r with range of r
where r is the transmission range as extremely dense MANETs
that have highly specific behavioral characteristics. Therefore,
these extremely dense MANETs cannot be studied alongside
the dense MANETs which are the focus of this research. Restof the graphs in figure 4 show no such special clustering ofdata points and are considered dense MANETs in this study.
In order to assess the impact of chalone threshold onreachability we selected the case of 150m×150m with range of
30m and evaluated for chalone threshold 1, 2, 3 and 4 as shownin figure 5. Theoretically reachable number of node pairs
for this MANET configuration was 76. It was observed thatchalone threshold 1 fails to deliver the data to destination for
9 of the reachable node pairs. In contrast, chalone thresholds
2 and above gives full reachability.
It was also noted in figure 6 that chalone threshold 2 andabove gives the same numbers of redundant rebroadcasts. Thisis due to the fact that maximum number of neighbors in thisconfiguration is 3 and that gives same number of redundantrebroadcast as of chalone threshold 2. Therefore the chalone
threshold value depends on number of neighbors and should
be tuned for each node for optimal reachability and reduction
in redundant rebroadcasts.
VIII. C ONCLUSION
Network wide packet broadcasting is an essential aspect ofany routing protocol including AODV which is the Wireless
Mesh Routing protocol in the latest IEEE 802.11s standard. However AODV uses flooding as the mechanism tobroadcast its control packets throughout the network. We

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ICACT Transactions on Advanced Communications Technology (TACT) Vol. 4, Issue 5, September 2015

th2-th3-th4

20

20

15

15

rebroadcasts

rebroadcasts

th1

10

5

0

671

10

5

0

20

40

60

80

Euclidean distance

0

0

20

40

60

80

Euclidean distanceFig. 6. Number of rebroadcasts Vs distance between node pairs for the case of 150mX150m and range 30m

found through the simulations that flooding as well as theblind-rebroadcasting is unusable at higher node densities in
MANETs. In contrast we propose a Cellular Automata based
broadcast mechanism inspired by biological cell proliferationin human organs. We borrow the chalone mechanism from organ growth process into MANET rebroadcasting and propose
a limited broadcast scenario which gives a saving of over 80%
of redundant rebroadcasts compared to both sequence number
controlled flooding and blind rebroadcasting. Our protocol isalso proved to be usable in MANETs with much higher nodedensities compared to networks that the flooding can support.
The chalone threshold should be a function that partly depends
on number of neighbors of each node for optimal results interms of redundant rebroadcasts and reachability.
IX. F UTURE W ORK
In the next phase of this research project, the bio-inspired
CA based MANET routing approach presented in this paper
will be tested with different mobility models applicable inpractical dense MANETs. It is proposed to simulate thedeveloped solution in a scenario such as a smart classroomof hundreds of students which allows collaborative learning.
ACKNOWLEDGMENTS
We gratefully acknowledge the OMNET++ and INET developer communities for making available the source code andtools for simulation work.
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Sulochana Sooriyaarachchi was born in Anuradhapura, Sri Lanka on the 18th of October 1981.
She obtained her BSc Eng. (Hons) in Electricaland Electronics Engineering from the University of
Peradeniya, Sri Lanka in 2006. She then joined theDepartment of Computer Science and Engineeringin the University of Moratuwa as a lecturer andobtained her MSc in Computer Science from thesame department in 2010. She is currently pursuing
her PhD in the University of Moratuwa conducting
research in the area of routing and control mechanisms in mobile ad-hoc networks.
Anil Fernando leads the Video Communicationsgroup at the University of Surrey, UK. He has beenworking in video coding and communications since1998 and has published more than 270 internationalrefereed journal and proceeding papers in this area
including a book on video communications. Furthermore, he has published more than 150 internationalrefereed journal and conference papers in multimedia communications. He has contributed to several
international (ROMEO, MUSCADE, DIOMEDES,VISNET, etc) projects and currently he is leading
an interactive video communications project (ACTION-TV) funded by theEuropean Union on Media communications.
Chandana Gamage is a senior lecturer in the
Department of Computer Science and Engineering,
University of Moratuwa, Sri Lanka. He received
his PhD from Monash University, Australia, MEngfrom AIT, Thailand and BSc Eng Hons from University of Moratuwa and worked as a postdoctoral
research scientist in Vrije Universiteit Amsterdam,
The Netherlands. Dr Gamage has research interests
in computer security and cryptography, enterprisesoftware architectures and embedded systems andhas published in leading conferences in these areas.

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ICACT Transactions on Advanced Communications Technology (TACT) Vol. 4, Issue 5, September 2015

673

MPEG-SCORM: an Ontological Approachof Interoperable Metadata
for Digital Television and e-Learning
Marcelo Correia Santos, Yuzo Iano
Department of Telecommunications of the Electrical and Computer Engineering School, UNICAMP (São Paulo State
University of Campinas) Campinas-SP, Brazil 13083-852
m134163@dac.unicamp.br, yuzo@decom.fee.unicamp.br
Abstract— The convergence of digital media offers an integrationof ICT focused on telecommunications and multimedia domain(under responsibility of the Moving Picture Experts Group,
ISO/IEC JTC1 SC29) and the ICTE (the ICT for Education),managed by the ISO/IEC JTC1 SC36, highlighting the MPEG
standards, employees as content and metadata to the multimedia
Digital TV and the technologies applied to e-Learning. Regarding
this, there is the problem of developing an interoperable
matching for normative bases, achieving an innovative proposal
in the convergence between digital telecommunications andapplications for e-Learning, also essentially multimedia. To reachthis purpose it is proposed to create a standard ontology ofinteroperable metadata for web, digital TV and extensions formobile devices based on the integration between MPEG-21 and
SCORM metadata standards. The methodology used consists onbuilding ontology between MPEG-21 SCORM which can beachieved on making a correspondence through the XPathlanguage, managed by the W3C. The employ of the XPathlanguage is desirable for matching and mapping both metadata
schema patterns – integrating MPEG-21 (mostly Digital Item
Declaration Language) and SCORM metadata schema. The
practical purpose is the creation and storage of objects for use indigital telecommunications as Digital Television, in aninteroperable way with the e-Learning industry, here as
description metadata for all sorts of media and hypermedia tocreate learning objects.
Keywords— Digital Television, e-Learning, Metadata, MPEG,
SCORM


T

I. INTRODUCTION
HE technological innovation issue comprehends a
research in a hybrid field that comprises a breakthroughon the media convergence process, on purposing an

Manuscript received by May 25, 2015. This work is a follow of the accepted
conference paper as an outstanding paper for the 17th International
Conference on Advanced Communication Technology, and has been partially
supported by the Brazilian agency CAPES.
Marcelo CORREIA SANTOS is a researcher in the Electrical and Computer
Engineering School, São Paulo State University of Campinas, SP 13083852
Brazil (Corresponding author, phone: 019-3521-3809; fax: 019-3521-3703; email: m134163@dac.unicamp.br).
Yuzo IANO is a professor in the Electrical and Computer Engineering
School, São Paulo State University of Campinas, SP 13083852 Brazil (e-mail:yuzo@decom.fee.unicamp.br).

interface between the norms and standard implemented in thefield of interactive multimedia, highlighting the Digital
Television (standardized by the ISO SC29 subcommittee), andthe field of the technologies for e-Learning (standardized by
the ISO SC36 subcommittee).
The whole bunch of ICT is subject to convergence andinterdependence of media. These techniques rely heavily on
standards that are negotiated and designed in standard-setting
bodies. An important role of ISO / IEC JCT1 is to converge
instances that define both components and services attached tothese topics.
It is proposed to analyze the constraints of possible
convergences between the MPEG family norms (conceived by
the JCT1 SC29, the standards body that carries MPEG) andthose of the ICTE (the ICT for Education, work underresponsibility of the JCT1 SC36), in particular the SCORM
metadata standard, as well the future "SCORM 2.0" standard.
As a second decisive state, it is therefore mapped theprospective normative framework matched between MPEG-21
multimedia document and the normative world of ICTE SCORM. The purpose of the project is to provide thespecification of a hybrid Ontology mapping the MPEG-21 and
SCORM metadata standards.
From this context, the research in conclusion propose thestudy based on the convergence of digital media working on
the hypothesis of the integration of both ICT and ICTE
focused on the telecommunications and the multimedia
domain.
This convergence covers two breaking questions up to besolved in our digital era: the interoperability of data andformats; and the integration of cited ISO working groups
Technically, Digital Television lies within the field of
MPEG multimedia, since it employs as its exhibition format
the digital video standard MPEG-4 AVC H264, the worldwide
industry standard today.
However, the standardization of the multimedia MPEG is
not restricted to MPEG-4, since other MPEG technologies arein process of specification by the SC29 subcommittee andactually are more powerful in terms of metadata description
and so on, as MPEG-7 and MPEG-21.
These distinct MPEG norms and its main defining
characteristics are highlighted in the Fig. 1, translated from thesource reference in French [1]:Copyright ⓒ 2015 GiRI (Global IT Research Institute)

ICACT Transactions on Advanced Communications Technology (TACT) Vol. 4, Issue 5, September 2015

Fig. 1 Different MPEG norms and its main characteristics in terms of
encoding quality, compression performance and user interaction [1].

According the Moving Picture Experts Group (MPEG),
MPEG-1 is a “suite of standards for audio-video and systems
particularly designed for digital storage media”. MPEG-2 is a“suite for standards for digital television”. On the other hand,
MPEG-4 is a “suite of standards for multimedia for the fixed
and mobile web”; and MPEG-7 is a “suite of standards fordescription and search of audio, visual and multimedia
content”.
MPEG-21, however, is a “suite of standards that defines anormative open framework for end-to-end multimedia
creation, delivery and consumption that provides content
creators, producers, distributors and service providers withequal opportunities in the MPEG-21 enabled open market, andalso be to the benefit of the content consumers providing themaccess to a large variety of content in an interoperable
manner”.
It can be noticed from these definitions and from theinterpretation of the graphic demonstrated in Fig. 1 that themain characteristic for MPEG-4 is the possibility of object
creation and manipulation.
For MPEG-7, the main gain achieved by its adoption would
be the metadata description of all media content only.
MPEG-21, as its major characteristic, allows the modellingof entities, entities which could comprehend content and an
object oriented domain of descriptors as well.
Still from the perspective of this analysis, in this research
we could conclude that MPEG-21 become the most suitableoption for metadata description as a breakthrough in this field
since its framework allows not only content description, but
all kinds of elements presented within the consumption
channel, from the content and object creation, throughbroadcasting and reaching the end user (who otherwise canperform the role of a producer as well).
Regarding this, the main objective on this work is
contributing on the development of an interoperable matching
between the normative bases in question, achieving an
innovative proposal in the convergence between digitaltelecommunications and applications for e-Learning, also

674

essentially multimedia, integrating MPEG-21 (mostly its
Digital Item Declaration Language) and SCORM metadata
schema. To reach this purpose the proposition is developing astandard ontology of interoperable metadata for web, digital
TV and extensions for mobile devices based on the integration
between MPEG-21 and SCORM metadata standards.
This hybrid ontology, possibly claimed as a new hybrid
metadata standard, would allow the creation and storage ofobjects for use in digital telecommunications, operating on
media like Digital Television, in an interoperable way with thee-Learning industry, which in its turn employs all sorts ofmedia and hypermedia technologies to create learning objects.
Regarding the challenges for the standardization of the ICT
applied to e-Education, it comprises a telecommunications
engineering problem still in developing the issue concerning
how the MPEG Video family, specially the MPEG-21 [2]standard, could offer a normative basis for the implementationof multimedia metadata related to e-Learning.
This development demands the adoption and employ ofsome tools to match all these learning and media objects,
further to the content itself (video, still images, sound, text,
hypertext etc), and must lie within a normative frame toguarantee interoperability, reusability and referring to themajor platforms or digital environments in both fields,
multimedia and e-learning.
For this purpose it was adopted in this research the XPathlanguage, managed by the W3C.
The software engineering to support this normalization
comprehends XML, MPEG-7, MPEG-21, themes approachedby the SC36. Otherwise, experts from ADL, entity whichdeveloped the SCORM standard, are engaged in SC36
subcommittee too, and already proposed to in a certain way
explore the capabilities of MPEG-21 to make this idea viable.
ADL strategy lies on capitalize the other subcommittees
norms, and encourage the adoption of the Part 5 of MPEG-21[3] (REL, or Rights Expression Language), to solve copyrightissues, besides it delegates to the LOM standard its metadata
description (or parts to other standards like IMS or DCMI –Dublin Core). This reveals a very converging approach andacceptation concerning the metadata and MPEG-21 issue on
the industry and market.
II. LEARNING OBJECTS AND METADATA STANDARDS
A Learning Object can be defined, in a perspective ofEngineering, according to IEEE 1484.12.1 standard (Standard
for Learning Object Metadata) [4], “For this standard, alearning object is defined as any entity, digital or non-digital,
that may be used for learning, education, or training”.
According to the IEEE LTSC [4], the LOM standard focus
on the minimum attributes needed to allow a learning object tobe found and evaluated. Metadata allow the cataloging andcoding of the objects to turn them comprehensible within moste-learning platforms.
For instance, SCORM doesn’t define itself a metadata
model – it recognizes the LOM standard as the standard in fact[5]. Yet, SCORM defines XML as the syntax for metadata
representation (process called XML binding). That is the

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reason why the LOM standard is used for represented
metadata on SCORM mapped elements on this research.
Actually, the standard SCORM 2014, or SCORM 1.4,
presents 3 Parts (or sub-specifications) [5]: Content Packaging (CAM) section: specifies how
content should be packaged and described. It isbased primarily on XML.
 Run-Time section: specifies how content should belaunched and how it communicates with the LMS.
It is based primarily on ECMAScript (JavaScript).
 Sequencing section: specifies how the learner cannavigate between parts of the course (SCOs). It isdefined by a set of rules and attributes written in
XML.
Within its CAM model published by ADL [5], SCORM
defined in its part related to Metadata nine categories to
describe learning objects attributes. The definition must be
applied to assets, SCO (groups of assets), activities, content
organizations and content aggregations, for their identification,categorization, consult and findability, to facilitate sharing andreusability.
For instance, it is presented an example of SCORM
metadata XML coding in Fig. 2:

Fig. 2 SCORM metadata file highlighting the description of a hypermedia
document resource for the web.

To match specifications of theses metadata standards theproceeding is mapping their categories using, in this research,
the XPath language, as it was primary done mapping andmatching DCMI–Dublin Core and SCORM metadata
standards, as shown in Table I. Mapping is expressed in XPath
syntax.
As we can observe in Table I, these identifiers cover fromthe most generic ones to the most specifics, related to the
Rights, for example, which is a focus of ADL standardization
concerning MPEG-21 and SCORM.

675

TABLE IMAPPING OF SCORM AND DCMI METADATA (XPATH SYNTAX)

Matching SCORM (LOM) / DCMI
SCORM
DCMI
/lom/general/identifier/entry/dc/identifier/lom/general/title/dc/title/lom/general/language/dc/language/lom/general/description/dc/description/lom/general/keyword or/dc/subject/lom/classification/keyword
com classification/purpose equals to“Discipline” or “Idea”/lom/general/coverage/dc/coverage/lom/educational/learningresourcetype /dc/type/lom/lifecycle/contribute/date/dc/date
com lifecycle/contribute/role equals to“Publisher”/lom/lifecycle/contribute/entity/dc/creator
com lifecycle/contribute/role equals to“Author”/lom/lifecycle/contribute/entity/dc/othercontributor
with the contributing type specified inlifecycle/contribute/role/lom/lifecycle/contribute/entity/dc/publisher
com lifecycle/contribute/role equals to“Publisher”/lom/technical/format/dc/format/lom/rights/description/dc/rights/lom/relation/resource/description/dc/relation/lom/relation/resource/dc/source
com relation/kind equals to“IsBasedOn”

From the Table I, concerning the matching between
SCORM and Dublin Core metadata standards, it is possible toanalyze a projection for the expected results achieved throughthe work on the further mapped hybrid ontology proposed,
implying in its turn SCORM and MPEG-21 metadata
standards.
It can be noticed the syntax of the XPath language used forthe mapping and matching system, in a neutral way, between
both metadata structures of representation.
It were found out the matches among the 15 (fifteen)elements presented in the Dublin Core standard and in theother hand 15 equal elements found within the SCORM
metadata structure, actually LOM structure, as alreadyexplained in this article.
III. DIGITAL TELEVISION AND E-LEARNING METADATA
The metadata systems integration is already a longtime
issue of investigation for the telecommunications community,
mostly linked to Digital Television. In [1], [6], [7] and [8], wehave samples of the discussion involving MPEG-7, MPEG-21
and TV-Anytime. Even the issue of Digital TV and SCORM
was initially discussed [11].

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ICACT Transactions on Advanced Communications Technology (TACT) Vol. 4, Issue 5, September 2015

MPEG-21 became the modular development andstandardization platform (a framework) [12] towards global
integration of all multimedia documents. The multimedia are
not the product of an specific area of knowledge, but is adirect consequence of standardization of digital practices suchas telecommunications, audiovisual, informatics.
Although the fact that MPEG-21 came up from acommunity that focuses on audio and video, the so called
MPEG-21 Framework [12] can host all kinds of complex
digital objects, such as electronic text, digital magazines,
scientific data etc.
As can be seen from the scientific literature [13], [7] and [1]and from the norm itself [3], the MPEG-21 standard have a
non-rigid structure of metadata, and Part 2 standard, DID,
exposes the digital Item as the most generic approach for thispurpose structural description of use of metadata in digital
objects of all kinds.
The MPEG-21 standard holds today 21 parts [3]. MPEG-21
is an XML-based metadata specification that brings two
fundamental pillars: The definition of a unit or essential object of
distribution and transaction, which is called
Digital Item; And the notion of "reader" – the concept of users
interacting with it.
The MPEG-21 metadata standard, however, is currently
partitioned in 22 parts, as follows [3]:1. Vision, Technologies and Strategy (Digital Item
definition)
2. Digital Item Declaration
3. Digital Item Identification
4. IPMP (Intellectual Property Management and Protection)
5. Rights Expression Language
6. Rights Data Dictionary
7. Digital Item Adaptation
8. Reference software
9. MPEG-21 file format
10. Digital Item Processing
11. Evaluation methods for persistent association
Technologies
12. Test bed for MPEG-21 resources delivery
13. Scalable Video Encoding – Transferred to MPEG-4
AVC standard
14. Conformance testing
15. Event reporting
16. Binary format
17. Fragment identification of MPEG-21 resources
18. Digital Item Streaming
19. Media Value Chain Ontology
20. Contract Expression Language
21. Media Contract Ontology
22. User Description
The central concept within the MPEG-21 metadata standard
can be understood as the DI - Digital Item, as defined in Part 2of the standard [12].

676The DID, or Digital Idem Declaration, relates a digitalproduct, which can be simple or composite. A typical example
is a webpage, containing different multimedia resources.
The use of MPEG-21 DIDL (Digital Idem Declaration
Language) as a generic standard for the representation,
cataloging and storage of digital learning objects in the libraryhas been proposed by [14]. It demonstrated the applicability of
the DIDL for representing complex objects of any type of
media or content to create a digital collection in the library.
The second key concept in MPEG-21 format is thedescription of the production and interaction with the media,
for all stakeholders in the process, from content producer tothe end user. Therefore, it can be said that the main objectiveof MPEG-21 is to define the technologies needed to support
the exchange, access, consumption, trade or handling ofDigital Items in an efficient and transparent way [12].
A workflow exemplifying the metadata representation of amedia like a digital music album, in the MPEG-21 standard,
can be represented as designed on Fig. 3:

Fig. 3MPEG-21 metadata representation of a descripted media – adigital music album [3].

As we can infer from the Fig., there are key elements likean identifier and a descriptor whose coding is mandatory for
representing data aspects of each subpart of the hereby
exemplified digital media.
IV. METHODOLOGY: A CONVERGENT ONTOLOGY FOR THE
INTEGRATION BETWEEN MPEG-21 SCORM
The intended Ontology between SCORM and MPEG-21
can be carried out by matching their syntax correspondences,through the W3C XPath language.
The use of XPath language is directed to carry out thecomparative study of mapping between the standards of
SCORM metadata and MPEG-21, applying this methodology.
XPath is a language maintained by the W3C with the primaryobjective of addressing parts of an XML document, and it isalso used to test whether a code matches a pattern, or anothercode.
There are some key features regarding XPath language
which were strongly considered on the decision for this
proposed methodology:

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ICACT Transactions on Advanced Communications Technology (TACT) Vol. 4, Issue 5, September 2015

 XPath is a syntax for defining parts of an XML
document XPath uses path expressions to navigate XML
documents XPath contains a library of standard functions
 XPath is a major element in XSLT* XPath is a W3C recommendation*XSL stands for EXtensible Stylesheet Language (and it isapplied on XML files).
The MPEG-21, as already stated, provides the DIDL
(Digital Item Declaration Language), but also other schemes
and their languages, within other of the many parts of thestandard, for the cataloging of objects and the flow of
information, the case also DII (Digital Item Identification),and DIA (Digital Item Adaptation); but also for dealing withcopyright data (MPEG-21 Part 5 REL - Rights Expression
Language), CEL (Contract Expression Language), IPMP
(Intellectual Property Management and Protection); and evenuse cases (UD - User Description).
The orientation of the work of JTC1 SC36, as can beaccompanied by papers published by IEEE [13] and [17] isbased essentially on the portability, interoperability andadaptability of technologies for education, teaching andlearning. The SC36 does not, therefore, calling to extend thework carried out by other technical committees, such as the
SC29 itself, the media committee, which deals with soundencoding, image, multimedia and hypermedia information.
However, the SC36 was a pioneer in pointing to the needfor synergy with the SCORM MPEG-21 standard, proposition
however limited to addressing issues of copyright andeventually the e-commerce of ICTE (Part 5 of the standard).
The MPEG-21 normalization lies in perfect continuity withthe ones previously carried out within the MPEG-7 framework.
And many MPEG-7 standard descriptors are part of the
MPEG-21 metadata schema [12] scope.
The descriptors and corresponding description schemes aredeveloped under the responsibility of MDS group, whose data
description is founded on the semantics of XML markup
language.
The interrelationships between MPEG and e-Learning
metadata standards are outlined in Table II [15] and in Table
III [16]:677

TABLE III
MAPPING BETWEEN MPEG-7 AND SCORM [16]

DIDL documents are actually XML 1.0 documents. The
DIDL syntax is based on an abstract structure defined in the
Digital Item Declaration Model.
This model defines the DIDL elements, namely: Container;
Item, Component, Anchor, Descriptor, Choice, Selection,
Condition, Annotation, Assertion, Resource, and Statement.
Thus structurally represented as Fig.s 4 and 5:

TABLE II
MAPPING AMONG THE MPEG AND E-LEARNING MAIN METADATA
STANDARDS [15]Fig. 4
Partial graphical representation ofHighlighting the Declarations and Item elements.

DIDL

schema[12].

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ICACT Transactions on Advanced Communications Technology (TACT) Vol. 4, Issue 5, September 2015678

To perform the integration of standard patterns, the solution
being implemented is to make the correspondence between the
categories of SCORM metadata and those defined by MPEG21 metadata schema.
Using the XPath language as the default to format the
taxonomies and create a new ontology, there were first
mapped the following standard SCORM metadata (LOM),
which would correspond to the multimedia standard MPEG21, aligned to the concept of platforms convergence. As
follows in Table IV:
TABLE IVSCORM AND MPEG-21 METADATA STANDARDS MAPPEDSCORM Multimedia Metadata

Fig. 5
Partial graphical representation of the DIDL schema generalized
from the ISO/IEC norm 21000-2:2003 [12].

The DIDL XML code for Declarations element (a special
element that defines a selection of elements without instantiatethem) would be displayed in the following generic form [12]:<xsd:element name="DECLARATIONS"><xsd:complexType><xsd:choice maxOccurs="unbounded"><xsd:element ref="ITEM"/><xsd:element ref="DESCRIPTOR"/><xsd:element ref="COMPONENT"/><xsd:element ref="RESOURCE"/><xsd:element ref="ANNOTATION"/></xsd:choice></xsd:complexType></xsd:element>/lom/general/identifier/entry/lom/general/title/lom/general/language/lom/general/description/lom/general/keyword/item[@identifier]/lom/general/coverage/lom/educational/learning/resource/type/lom/lifecycle/contribute/role/lom/lifecycle/contribute/date/lom/technical/format/lom/technical/size/lom/technical/location/lom/technical/duration/lom/rights/description/lom/relation/kind/lom/relation/resource/description/lom/relation/resource/catalogentry

MPEG-21
Metadata (underdevelopment)<mpeg21><mpeg21><mpeg21><mpeg21><mpeg21><mpeg7><mpeg21><mpeg21><mpeg7><mpeg7><mpeg7><mpeg7><mpeg7><mpeg7><mpeg21><mpeg7><mpeg21><mpeg21>

Table IV stands for the mapping and matching between
both metadata standards: SCORM and MPEG-21.
The mapped elements of both standards are up to bematched, on the purpose of achieving the hybrid ontology
witch establishes the convergence between e-learning
SCORM metadata standard with multimedia MPEG-21
metadata standard, interoperable and applicable for the wide
range of digital media, including the web, mobile media oreven digital television.
This proposed interoperable SCORM MPEG-21 ontology,
employing the W3C XPath language, focus on the main items
whose approaching is mandatory for achieving a significant
representation of the metadata elements necessary to both amultimedia digital item description and a learning object
description as well, developing a common hybrid new
ontology based on the body and syntax of the existing ones.
Fig. 6 Hierarquical metadata structure within an expected MPEG-21 general
purpose file in its complete structure [18].

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ICACT Transactions on Advanced Communications Technology (TACT) Vol. 4, Issue 5, September 2015

V. CONCLUSIONS
Until the present moment it was possible to obtain
successful results concerning the stages already overcame on
this research, which progresses at an advanced pace regarding
to the implementation of the specific goal of correspondence
between metadata standards of the knowledge domains issued.
The development work has consisted in creating an
Ontology focused on these mapped taxonomies in order topropose, from this ontology, an integration between the fieldsof Multimedia (comprehending Digital Television) and MPEGICTE for distance education / e -Learning.
In other words, the convergence between MPEG-21 and
SCORM as a standard for describing objects used forcataloging and for use in e-learning, in a broader sense, and elearning via Digital Television in a specific perspective of the
field of research.
A SCORM MPEG-21 Ontology, employing the W3C
XPath language, is already in an advanced stage in order tomake its contribution to the body of knowledge and theprocess of standardization in the metadata study domain, as
well to further the research there have been in development
the run-time and sequencing sections within this ontology.
It also contributes to a latent need for integration between
the universes of Multimedia and ICTE, represented byworking groups of SC29 and SC36 standards subcommittees,
ISO / IEC JTC1, in this context of convergence.
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T. Laquet, F. Prêteux, Vaucelle, A, and T. Zaharia, “Les normes
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A. Vaucelle, “MPEG-21: la norme des ICTE du XXIème siècle?”,Rétrospective et Perspective H2PTM’09, Paris, 2009.
MPEG-21 ISO/IEC N5231. MPEG21 Overview v.5. 2002.
IEEE LTSC. Standard 1484.12.1 for Learning Object Metadata. New
York: IEEE, 2002.
ADL Advanced Distributed Learning, SCORM 2004 4th Edition:
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L.G.P. Alves, G. Bressan, P. Jucá. R. Kulesza, F. Silva, “Compared
analysis on Digital Television Metadata”, Workshop DTV SBRC2006,
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S. Kalli, A. Lugmayr, S. Niiranen. Digital interactive TV and Metadata:
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S. Pfeiffer, U. Srinivasan, “TV-Anytime as an application scenario for
MPEG-7”, Proc. ACM Multimedia, Los Angeles, 2000, pp. 89-92.
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299-325.
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for T-Learning”, XXII SBIE - XVII WIE, Aracaju (Brazil), 2011.
MPEG-21 ISO/IEC 21000-2:2003. Multimedia framework (MPEG21)
Part 2: Digital Item Declaration. 2003.
J. Bormans, I. Burnett, F. Pereira, R. Van Walle, K. Hill, “MPEG-21:
Goals and Achievements”, IEEE Multimedia, vol.10, OctoberDecember 2003, pp.60-70.
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M. Ben Henda, F. Prêteux, A. Vaucelle et al. MPEG-21: une Base
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Télécom SudParis, 2008.
L. Lyon, M. Patel, S. Christodoulakis et al., “Project n507618 DELOS:
status report for work package 5”. In: Joint Programme of Activities(JPA3), February-September 2006.
I. Burnett, S. Davis, G. Drury, “MPEG-21 Digital Item Declaration and
Identification”, IEEE Multimedia, vol. 7, n. 3, June 2005, pp.400-407.
F. Schreiner. Content management and protection using Trusted
Computing and MPEG-21 technologies. Dissertation (Master inInformatics) – Munich Technical University (Germany), 2010.

Marcelo CORREIA SANTOS. Marcelo Correia
Santos received his B.S. in Communication from the
University of São Paulo, Brazil; MSC. degrees in
Communication and Informatics Applications fromthe University of São Paulo State and University ofParis Sorbonne Nouvelle, in São Paulo and Paris,
respectively, and is currently a researcher finishinghis Ph.D. followed since 2012 in ElectricalEngineering for Telecommunications at Campinas
State University of São Paulo. He worked as a
researcher at University of São Paulo and São Paulo State from 2003 to
2006. He worked as Assistant Professor of University of São Paulo
State in 2012 and as Titular Professor of the National Commerce
Service University, in São Paulo, since 2013.
Yuzo IANO. Yuzo Iano, IEEE Member, received the
B.S., M.S. and Ph.D. degrees in Electrical Engineeringfrom the Campinas State University of São Paulo in
1972, 1974 and 1986, respectively. He joined that
University as a Titular Professor in 1991, where healso worked as an Assistant Professor since 1975. Heserved as a Telecommunications Researcher at
Telebras, the Brazilian Telecommunications agency,from 1986 to 1990.

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680

APEM: Automatic paraphrase evaluation usingmorphological analysis for the Korean language
Sung Won Moon*, Gahgene Gweon*, Hojin Choi**, Jeong Heo****Dep. Of Knowledge Service Engineering, KAIST, Daejeon, Rep. Of Korea** Dep. Of Computer Science, KAIST, Daejeon, Rep. Of Korea*** Knowledge Mining Research Team, ETRI, Daejeon, Rep. Of Korea
augustmoon@kaist.ac.kr, hojinc@kaist.ac.kr, ggweon@kaist.ac.kr, jeonghur@etri.re.kr
Abstract— Paraphrase evaluation is used to determine
whether two input sentences share a same meaning. The
automatic analysis for paraphrase evaluation technology has apotential use in the area of information retrieval technology
since correctly paraphrased sentences can be used as alternative
input sentences in the retrieval process. In this paper, wesuggest an automatic paraphrase evaluation method usingmorphological analysis (APEM), which is suitable for the
Korean language. Using APEM and its variations, we present
preliminary results on how our automatic evaluation scorescompare to the existing method of bilingual evaluation
understudy (BLEU).
Keyword— Morphological analysis, Paraphrase evaluation

I. INTRODUCTION

paraphrase technologies has potential use in the area of
information retrieval technology since paraphrased sentences
can be used as alternative input sentences in the retrieval
process. For instance, if a user wants to know in whatcountries U2 has held concerts, he can ask, “What nations
have U2 held concerts in”. A Google search with this query
sentence yields 19,200,000 answers. However, the top ten
returned pages do not contain the answer. Instead, if aparaphrased sentence “What countries have U2 played in?” isused as a query sentence, google outputs 1,240,000 answers.
Although the number of answers has decreased by tenfold,
the top page among the returned pages lists the intended
answer by listing all the countries where U2 has played aconcert. Figure 1 shows the screen capture from the Google
search engine using these two paraphrased sentences.

P

ARAPHRASE EVALUATION is used to determine whether
two input sentences share a same meaning. In this paper,
we suggest an automatic evaluation method given a pair ofparaphrased sentences. An evaluation is a necessary step inorder to use paraphrased sentences in various applications,since we need to first determine whether the paraphrased
sentences are suitable for such usage. Thus far, research onparaphrase evaluation has been largely conducted for the
English language [1], [2], [3]. Therefore, for other languages,
such as Korean, modified versions of evaluation methods
used in the English language have been used. However, suchmethods are not ideal considering that the two languages
differ in structure. Given such need, we suggest an automaticparaphrase evaluation method using morphological analysis(APEM) for the Korean language. Automatic evaluation for———————————————————————
Manuscript received June 10, 2015. This work was supported in part by
ICT R&D program of MSIP/IITP, Grant ID : R0101-15-0062, Developmentof Knowledge Evolutionary WiseQA Platform Technology for Human
Knowledge Augmented Services.
S. Moon is with the Department of Knowledge Service Engineering,
Korean Advanced Institute of Science and Technology, Daejeon, Rep, of
Korea (phone: 82-10-9028-8724; e-mail: augustmoon@kaist.ac.kr).
G. Gweon is with the Department of Knowledge Service Engineering,
Korean Advanced Institute of Science and Technology, Daejeon, Rep, of
Korea (corresponding author phone: 82-42-350-1618; fax: 82-42-350-1610;
e-mail: ggweon@kaist.ac.kr).
H. Choi is with the Department of Computer Science, Korean Advanced
Institute of Science and Technology, Daejeon, Rep, of Korea (phone:82-42-350-3561; fax: 82-42-350-3510; e-mail: hojinc@kaist.ac.kr).
J. Heo is with the Automatic Speech Translation and Knowledge
Analytics Research Center, Electronics and Telecommunications ResearchInstitute (ETRI), Daejeon, Rep. of Korea (phone:82-42-860-6870;
fax:82-42-860-4889; e-mail: jeonghur@etri.re.kr)

Fig 1. Example of different results using paraphrased sentences

As seen in the example above, despite the advancements in
hardware and information retrieval techniques, there is room
for improvement in the area of information retrieval by using
alternative search phrases. Obtaining a desired answer to aquery is not a matter of increased number of returned answers,

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ICACT Transactions on Advanced Communications Technology (TACT) Vol. 4, Issue 5, September 2015

but more about providing a query that captures a user’s
intention. Therefore, evaluation of the resulting paraphrased
sentences is also an important research field that can be usedin the process of information retrieval along with research on
automatic paraphrase techniques. In addition, the paraphrase
evaluation technique can be used in natural language
processing applications such as text-to-text generation or
information extraction applications [4].
Our proposed evaluation methodology of APEM is suitable
for the Korean language, which is an agglutinative language.
This method is valuable in that much of the existing work inparaphrase evaluation has been geared towards inflectional
language, such as English. We consider two characteristics ofagglutinative language in our suggested method: use ofendings and postpositions. In agglutinative languages,“endings” are added at the end of a verb to convey
information such as tense, mood, or social relationships
between speaker and listener. In contrast, an inflectional
language, such as English, makes extensive use of auxiliaries
to convey such information. In addition to endings,
postpositions are used in agglutinative languages todetermine a case of a noun or relationship between multiple
words. Since an agglutinative language has many variations
using endings and postpositions, using the same evaluation
methodology as that used in inflectional language yields
evaluation results that are too strict. Therefore APEM
discards morphemes that do not carry meanings, such as
endings and postpositions, to reflect the characteristics ofagglutinative languages.
We also examine whether two types of APEM variation
methods would improve the performance of paraphrase
evaluation, namely APEM+synonym dictionary (APEM_SD)
and APEM + synonym dictionary +Google distance(APEM_SDGD). In the rest of this paper, we first present
existing work on paraphrase evaluation. Next, a simple
experiment that is designed to assess our proposed evaluation
method is presented, followed by the results of theexperiment.
II. BACKGROUND
The task of paraphrase evaluation has recently been
receiving increased attention along with the advancement in
the task of paraphrase generation [5]. The evaluation task is
one of the three main subtasks of the paraphrase generation
process, i.e. extraction, recognition/evaluation, andgeneration [6]. The paraphrase evaluation task can be
conducted either manually or automatically. Table 1
summarizes previous research on paraphrase evaluation
using both manual and automatic evaluation processes.
TABLE IRESEARCH ON PARAPHRASE EVALUATIONFirstAuthor

Year

MethodBangalore [7]Barzilay [8]Papineni[1]Fujita [9]Glickman [10]Dolan [11]Snover[2]Callison-Burch [12]Snover[13]Chen [3]Fujita [14]

2000
2002
2002
2004
2004
2005
2006
2008
2009
2011
2012

String accuracy, Bag accuracy
Readability, Fidelity
N-gram precision (BLEU)
Longest Common Subsequence(LCS)
A case study for verbs
Correctness
Translation Edit Rate (TER)
5-point Likert scale
TER, Stem match, Synonym match
Paraphrase In N-gram Changes (PINC)
5-point Likert scale681

For a manual evaluation, human evaluators assess thequality of paraphrased sentences according to the provided
standards. The main advantage of a manual evaluation is thathuman judgment, which is difficult to capture with rules,
such as idioms or jokes, can be correctly evaluated. However,
due to the nature of human judgement, different evaluators
will assign varying scores even if they are using the same
standards. Therefore, a method for checking the reliability ofthe evaluated scores, such as a correlation analysis, should
follow a manual evaluation process. In addition to variationsin judgement, a manual evaluation has limitations in terms ofthe number of sentences that can be evaluated due to time andmonetary constraints.
An automatic evaluation can address some of thedisadvantages of a manual evaluation. Compared to a manual
evaluation, an automatic evaluation is cheaper and can yield
results that are more consistent when the system is provided
with a clear set of rules. However, it is difficult to provide
such clear rules and there exist limitations on the level ofexpressions that machines can comprehend. Despite suchdifficulties of automatic evaluation, as the amount of datathat needs evaluation increases, it becomes infeasible forresearchers to conduct a manual evaluation. Therefore,
attempts in improving the accuracy of automatic evaluations
are increasing.
Automatic paraphrase evaluation can be conducted using
features at the surface or semantic level. The main surface
level feature used for paraphrase evaluation is n-gram, which
is a simple yet powerful feature in that the methods using
n-gram yield paraphrase evaluation results with highperformance. Popular methods that use n-gram as a mainfeature are Bilingual evaluation understudy (BLEU),
Translation edit rate (TER), and Paraphrase in n-gramchanges (PINC) [1], [2], [3]. However, using n-gram without
any processing is not suitable for an agglutinative language
such as Korean. In an agglutinative language, a word can takemany different surface forms by using various endings or
postpositions. Therefore, using n-gram as a feature would be
too strict of a rule for detecting words that are different on thesurface but are semantically identical in Korean. Therefore adifferent evaluation method adapted to the agglutinative
language in paraphrase needs to be developed. Thus, in thispaper we suggest automatic paraphrase evaluation usingmorphological analysis (APEM), which accounts for thevariations of surface forms in agglutinative languages.
In addition to APEM, which mainly uses surface levelfeatures for evaluation, we also suggest two additionalvariations of APEM by considering semantic level features as
used in existing methods [13], [15], [16]. In particular, a
popular semantic tool used for paraphrase evaluation issynonym dictionaries as used in the Translation edit rate –plus (TERp) method. We suspect that APEM + synonym
dictionary (APEM_SD)
could
improve
APEM’sperformance since words that are paraphrased with adifferent syntactic form, yet carry the same semantic meaning
can be evaluated as having the same meaning. However,
APEM_SD is a very naïve approach in that it uses data fromsynonym dictionaries without addressing word sense
disambiguation (WSD). For example, consider the following
sentence: “The power went out last night”. In this example,
although ‘power’ and ‘force’ are synonyms in a dictionary,

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ICACT Transactions on Advanced Communications Technology (TACT) Vol. 4, Issue 5, September 2015

they cannot be replaced with each other due to inappropriate
context. Therefore, we also propose a third method of APEM
+ synonym dictionary + Google distance (APEM_SDGD)
that considers context by using semantic similarity of words
in a sentence. In the next section, we explain how the threemethods of APEM, APEM_SD, and APEM_SDGD are
implemented.
III. METHODSThis section describes the data source as well as the details
on how the manual and automatic evaluations are conducted.

682

and reference sentences that are used for paraphrase
evaluations. Here the candidate sentence is the target
sentence that will be evaluated in terms of paraphrase
accuracy compared to a set of reference sentences. Typically
BLEU calculates an evaluation score between the candidate
and four reference sentences. The final evaluation score is the
maximum score of these four scores. Note that both thecandidate and reference sentences are translated versions of
the original sentence. To calculate the evaluation score, thenumber of identical words in the candidate and reference
sentences is divided by the total number of words in thecandidate sentence.

A. Data source
As stated in the introduction, one application of theparaphrased sentences is using them as alternative input
sentences in question and answering (QA) systems. Thus, weselected one hundred question sentences from a QA system,
which is a Korean quiz show called “Janghak quiz”. Thesehundred sentences were given as inputs to an automaticparaphrase generation system to produce paraphrased pairsthat were evaluated using manual and automatic evaluation
methods [17].
B. Gold standard using manual evaluation
To validate the quality of the paraphrased Koreansentences generated by the automatic system, we conducted amanual evaluation. Three human evaluators were asked toassess one hundred sentences using the guidelines proposedby Callison-Burch et al [12]. Figure 2 shows the specificguidelines. The interclass correlation (ICC) score of 0.87
suggests that our manual evaluations results are reliable.
The gold standard value was determined by calculating themean value of the three human evaluators’ scores [3]. The
mean value of the gold standard evaluation scores for the one
hundred sentences is 2.89 (s.d=1.08). Since the scales for the
manual and automatic evaluation score are difficult tocompare due to the difference in the scales, we normalizedeach score by converting it into a standardized score. The
mean value of the manual evaluation scores using
standardization is 0.47 (s.d=0.27).

Fig 3. Example of paraphrased sentences. Circles are words that are identicalacross the given sentences.

Figure 3 shows sample sentences with two reference
sentences as an example. The evaluation score for the
candidate and reference 1 is 2/5, whereas the score for the
candidate and reference 2 is 4/5. Thus the final BLEU score is
4/5, which is the maximum score between these two scores.
D. Automatic paraphrase evaluation using morphologicalanalysis(APEM)
In this section, we introduce APEM along with its twovariations, APEM_SD and APEM_SDGD.Figure 4 shows anexample pair of sentences that will be used to explain thethree evaluation processes. Sentence 1 is the original input
sentence, and sentence 2 is the paraphrased sentence.

Fig 4. Example of paraphrased sentences. Circles are words that are identical
whereas rectangles are words in synonym relationships.

Fig 2. Evaluator rated paraphrases along a 5-point Likert scale

C. Bilingual evaluation understudy (BLEU)
BLEU is a popular method used for various tasks in thearea of machine translation, including automatic paraphrase
evaluation [1]. Since BLEU was developed originally for
conducting evaluations of foreign language translations, theoriginal sentence is in a different language than the candidate

To implement APEM, we first extracted morphemes for an
input sentence using ETRI morpheme analyser [18]. Next,
we removed morphemes that are labeled as endings andpostpositions and kept the ones that carry real meaning in a
sentence, such as nouns or predicates. The highlighted words
in Figure 4 indicate morphemes that are kept after removing
the unnecessary morphemes. Note that the unhighlighted
words are discarded because these do not involve theessential meaning of the sentence, but merely function to
make a sentence grammatically correct.
After identifying the critical morphemes that carry
meanings, we calculate the evaluation score according to theequation (1). The numerator is the number of identical words
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ICACT Transactions on Advanced Communications Technology (TACT) Vol. 4, Issue 5, September 2015

in sentence 1 and sentence 2. In our example sentences, theword pairs “U2/U2” are identical words. Thus, the numerator
is one. The denominator is the number of meaningful
morphemes in sentence 1, which is four in our example
sentence. Therefore, the evaluation score for the paraphrased
sentences in our example is 0.25. Note that according to theformula presented in equation (1), the evaluation score canrange from 0 to 1, unlike the manual evaluation score, whichranges from 1 to 5.Using APEM, the mean value of the 100
sentences is 0.76 (s.d=0.17).
Score =

𝑁𝑢𝑚𝑏𝑒𝑟 𝑜𝑓 𝑚𝑎𝑡𝑐ℎ𝑒𝑑 𝑚𝑜𝑟𝑝ℎ𝑒𝑚𝑒𝑠
𝑁𝑢𝑚𝑏𝑒𝑟 𝑜𝑓 𝑚𝑒𝑎𝑛𝑖𝑛𝑔𝑓𝑢𝑙 𝑚𝑜𝑟𝑝ℎ𝑒𝑚𝑒𝑠 𝑖𝑛 𝑜𝑛𝑒 𝑠𝑒𝑛𝑡𝑒𝑛𝑐𝑒(1)

For APEM_SD, the method for calculating the numerator
differs from APEM. In APEM_SD, if paired words aresynonyms, they are regarded as “matched” whereas in AEPM,
only identical words were counted as matched morphemes.
Therefore, in our example sentences, the word pairs of“countries/ nations”, “U2/U2”, “held concert/ played” arepairs that are either identical or share synonyms. Thus, thenumerator is three. The denominator is the number of
meaningful morphemes in sentence 1, which is four.
Therefore, the APEM_SD evaluation score for theparaphrased sentences in our example is 0.75.
For APEM_SDGD, we conduct an additional step from
APEM_SD to calculate the numerator of the equation (1) byusing an API from the Mechanical Cinderella project [19].
Since using APEM_SD yields “matched” words that are notin synonym relationships when considering context, we used
Google distance to measure semantic similarity of words.
The main assumption of the Google distance measure is thatwords that are used in a similar context would have a higher
probability of appearing together in a document. Therefore, if
a paired set of words has a high level of semantic similarity,
the number of web pages that are returned in the Google
search engine using those words would be higher compared
to words with a low level of semantic similarity. Based on
this idea, the equation uses four main numbers to calculate
Google distance between two words, x and y as shown inequation (2). In the equation, f(x) and f(y) are the number ofpages returned by the Google search engine using each term.
F(x, y) is the number of pages where both x and y occurs, andM is the total number of web pages returned by the Google
search engine.

NGD(𝑥, 𝑦) =max{log 𝑓(𝑥),log 𝑓(𝑦)}−log 𝑓(𝑥,𝑦)log 𝑀−min{log 𝑓(𝑥),log 𝑓(𝑦)}(2)

We selected the threshold of Google distance score as 0.35
for filtering the synonyms. The threshold is heuristicallycalculated based on the normalized Google distance scoresfor a set of randomly selected words from the sentences in ourdataset. We calculated approximately 600 pair of words andobserved that, in general, a score of 0.35 or larger iscalculated for correctly paired synonyms. For example, for
the words used in Figure 4, the Google distance score
between ‘nations’ and ‘countries’, which are commonly used
together, is 0.352. The Google distance score for the words
that do not appear frequently together, such as ‘power’ and‘force’is 0.163.

683

IV. RESULTS AND DISCUSSION
In this section, we present the correlation scores among thegold standard, BLEU, and the three variations of APEM. The
positive medium correlation between the gold standard andthe comparison method suggests that our automatic
evaluation score captures some part of human evaluation
scores. However, we acknowledge that at the current stage,
the correlation is not accurate enough for use in place ofhuman evaluation.
TABLE ⅡPERFORMANCE OF THE PARAPHRASE EVALUATION
MethodCorrelation

BLEU
APEM
APEM_SD
APEM_SDGDBLEU_APEM(2:8)
BLEU_APEM(5:5)
BLEU_APEM(8:2)

0.57
0.62
0.30
0.60
0.64
0.64
0.61

As seen in Table 2, BLEU_APEM, which mixes the scoresof both BLEU and APEM, performed best. In addition, oursuggested method of APEM and APEM_SDGD performed
slightly better than the existing method of BLEU. It was
surprising to see that APEM_SD scores were much lower at
0.3 compared to other methods. Thus, our experiment showsthat using synonyms without considering context has a highpenalty.
V. CONCLUSION
Korean paraphrase evaluation is an important research areathat has much room for improvement. Research from thisarea can help improve the effectiveness in information
retrieval technology. Although the Korean evaluation methodthat we suggested in this paper is a beginning step towards
automatic paraphrase evaluation, the higher correlation of
APEM compared to BLEU shows promise in that usingmorphemes in agglutinative languages is helpful. However,
APEM_SD, which is our naïve approach for including asemantic feature that simply utilizes a synonym dictionary,hurts performance. Efforts for considering contextual
information, such as in APEM_SDGD, are necessary ifsemantic features are to be used.
In future work, we plan to extract more features of
agglutinative languages for use in evaluation. For example,
our current method uses a single morpheme as a feature. A
more advanced approach would be considering multiple
morphemes that constitute a meaningful unit as a feature.
Additionally, the inclusion of advanced measurements thatconsider context would increase the accuracy of ourtechnique. For example, compared to using synonyms fromdictionaries, the use of words from sentences with varying
expressions in Wikipedia could be helpful.
ACKNOWLEDGMENT
This work was supported by ICT R&D program of
MSIP/IITP. [R0101-15-0062, Development of Knowledge
Evolutionary WiseQA Platform Technology for Human
Knowledge Augmented Services]

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ICACT Transactions on Advanced Communications Technology (TACT) Vol. 4, Issue 5, September 2015

REFERENCES
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[14]

[15]

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[18]

[19]

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study of translation edit rate with targeted human annotation,” In
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Chen, David L., and William B. Dolan, "Collecting highly parallel
data for paraphrase evaluation," Proceedings of the 49th Annual
Meeting of the Association for Computational Linguistics: Human
Language Technologies-Volume 1, Association for Computational
Linguistics, 2011.
Madnani, Nitin, and Bonnie J. Dorr, "Generating phrasal andsentential paraphrases: A survey of data-driven methods,"
Computational Linguistics 36.3: pp. 341-387, 2010.
Liu, Chang, Daniel Dahlmeier, and HweeTou Ng, "PEM: A
paraphrase evaluation metric exploiting parallel texts," Proceedingsof the 2010 Conference on Empirical Methods in Natural Language
Processing, Association for Computational Linguistics, 2010.
Androutsopoulos, Ion, and ProdromosMalakasiotis, "A survey ofparaphrasing and textual entailment methods," Journal of Artificial
Intelligence Research: pp. 135-187, 2010.
Bangalore, Srinivas, and Owen Rambow, “Corpus-based Lexical
Choice in Natural Language,” Proceedings of the 38th Annual
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for Computational Linguistics, 2000.
Barzilay, Regina, and Lillian Lee, “Bootstrapping Lexical Choice via
Multiple-Sequence Alignment,” Proceedings of the ACL-02
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processing-Volume 10, Association for Computational Linguistics,
2002.
Fujita, A., Furihata, K., Inui, K., Matsumoto, Y., & Takeuchi, K,“Paraphrasing of Japanese light-verb constructions based on lexicalconceptual structure,” In Proceedings of the Workshop on Multiword
Expressions: Integrating Processing, Association for Computational
Linguistics, pp.9-16, 2004.
Glickman, Oren, and I. Dagan, “Acquiring lexical paraphrases from asingle corpus,” Recent Advances in Natural Language Processing III,John Benjamins Publishing, Amsterdam, Netherlands, pp. 81-90,
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Dolan, W. B., & Brockett, C, “Automatically constructing a corpus ofsentential paraphrases,” In Proc. of IWP, 2005.
Callison-Burch, Chris, "Syntactic constraints on paraphrases
extracted from parallel corpora," Proceedings of the Conference on
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Computational Linguistics, 2008.
Snover, M. G., Madnani, N., Dorr, B., & Schwartz, R, “TER-Plus:paraphrase, semantic, and alignment enhancements to Translation
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Fujita, A., Isabelle, P., & Kuhn, R, “Enlarging paraphrase collections
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Sungwon Moon is a master student in thedepartment of knowledge service engineering,
Korea Advanced Institute of Science andTechnology (KAIST). He received his Bachelor’s
degree from Handong Global University, Korea(2013). His current interests are in the area of
natural language processing, data mining andcomputer supported collaborative learning.

Ho-Jin Choi is an associate professor in KAIST
Computer Science Dept. In 1995, he received a
PhD in artificial intelligence (AI) from Imperial
College London. Since 2010, he participates
inSystems Biomedical Informatics ResearchCenter at Seoul National University Medical
School. He is in the boards of directors for
Software Engineering Society of Korea, for
Artificial Intelligence Society of Korea, and for
Korean Society of Medical Informatics. His
current interests include AI, knowledge
engineering, data mining, topic mining,
intelligent personal assistant, natural language
QA, and biomedical informatics.
GahgeneGweon is an assistant professor in thedepartment of knowledge service engineering,
Korea Advanced Institute of Science andTechnology (KAIST). She received her PhD in
human computer interaction from Carnegie
Mellon University, United States (2012). Her
current interests are in the area of human
computer interaction, computer supported
collaborative learning, and natural language
processing.

Jeong Heo is a senior researcher inElectronics
andTelecommunications
Research Institute, Daejeon, Rep. of Korea, He
received his MS degree in computer science
for the University of Ulsan(2001), His
research interests include natural language
processing, text mining, social big data
analytics, and question answering.

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ICACT Transactions on Advanced Communications Technology (TACT) Vol. 4, Issue 5, September 2015

685

Fault Resilient Communication Network
Architecture for Monitoring and Control of Wind
Power Farms
Shahid Hussain*, Young-Chon Kim*** Department of Computer Engineering, Chonbuk National University, Jeonju 561-756, South Korea** Smart Grid Research Center, Chonbuk National University, Jeonju 561-756, South Korea*shahiduop@jbnu.ac.kr, **yckim@jbnu.ac.kr
Abstract— Real time monitoring and control of wind power
farm (WPF) require a highly reliable communication network
infrastructure. The monitoring and control can be guaranteed
through the communication network by using redundantresources and ensuring quality of service (QoS) for different
applications. In this paper, we study and simulate fault-resilient
network architecture for monitoring and controlling of WPF.
First, communication network topologies are explored. Then we
propose a fault-resilient communication network architecture
which consists of three different levels: (1) data generation level,(2) data aggregation level, and (3) control center level. Eachlevel is defined by its function, physical location, network
topology, communication link bandwidth, redundant nodes, andlinks. In accordance to IEC 61400-25 standard, the monitoring
traffic of wind turbine is classified into critical and non-critical
data according to the required QoS. Due to low cost,
non-proprietary standard, and guaranteed real-time services,
the Ethernet technologies are currently used in various
industrial applications. Several network failure scenarios basedon Ethernet technology are used to simulate the networkarchitecture through OPNET. The performance of the networkarchitecture is evaluated on the basis of the amount of received
data, end-to-end delay, and data loss at control center. The
simulation results show that the communication networkarchitecture can guarantee the transmission of WPF criticaldata.
Keyword— Communication Networks; IEC61400-25;
Monitor and Control; Reliability and Resiliency; Wind PowerI.

W

INTRODUCTION

IND is a natural and low cost resource that is neverdepleted and can be used for an environment friendly
renewable energy production. These characteristics of windlead to a fast increase in WPF around the world. Mountains
and offshore locations are the suitable choices for wind power
because of stable and strong wind with space availability.
———————————————————————
Manuscript received August 24, 2015. This work was supported by the
National Research Foundation of Korea (NRF) funded by the Korea
government (MSIP) under the Grant no. 2010-0028509.
Shahid Hussain is with Department of Computer Engineering, Chonbuk
National University, Jeonju 561-756, South Korea. (e-mail:shahiduop@jbnu.ac.kr).
Young-Chon Kim is with Smart Grid Research Center, Chonbuk
National University, Jeonju 561-756, South Korea.(Corresponding author,
phone:+82-63-270-2413; fax: +82-63-270-2394;
e-mail: yckim@jbnu.ac.kr).

Some European countries such as Germany, Denmark, andUnited Kingdom are rapidly installing offshore WPF withlarger size wind turbines (WTs) and higher power capacity.
The offshore wind power generation is facing several issues:high construction cost, offshore installation, and maintenancecost. The construction and installation are considered to be
initial investment expenditure. However, the maintenance andrepair need a special attention because it is a long term andcontinuous task. The communication networks can play asignificant role in the reduction of maintenance and repair
expense by providing real time monitoring and control
mechanism to these WPF. Communication networks canenable the control center (CC) to monitor the status of WTs inreal time. The CC then controls the operation of the WT with
control commands. Currently, various monitoring techniquessuch as sensor and infrared camera based monitoring are used
[1,2]. Fig.1 shows a schematic diagram of WPF
communication network. In this figure, the monitoring andcontrol system for WPF is divided into three parts. In the firstpart, all WPF are connected to a remote terminal through awired communication link. The second part is thecommunication network by using wired or wireless according
to the requirements. At the third part, there is a CC withdifferent monitoring and control servers system. An efficientmonitoring and control operation strongly relies on the highavailability of data with a minimum latency. In view ofcommunication network, the resiliency can be defined that thecommunication network should be able to route the traffic via
secondary resources to ensure the data transmission under any
failure of device and link. The issues in communication
network that can influence the WPF system include plane
maintenance, component failure and accident/disaster [3].
Therefore, designing a fault-tolerant communication network
is highly required for WPF. In this regards, several
communication architectures have been proposed in theliteratures. The authors in reference [4] proposed an Ethernet
passive optical network (EPON) based communication
network architecture. The communication network wasmodeled through optical network unit (ONU) and optical line
terminal (OLT). In reference [5] a resilient communication
network for large-scale offshore wind farm was proposed withthe focus on redundant resources in the network. An open
shortest path first (OSPF) protocol and rapid spanning tree
protocol (RSTP) was used for avoiding loop in the network.

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ICACT Transactions on Advanced Communications Technology (TACT) Vol. 4, Issue 5, September 2015

686

Fig. 1. Schematic diagram of communication network for wind power farm monitoring and control

Resilient wireless communication network architecture forsmart grid in building area network (BAN) was proposed by
the authors in reference [6]. To achieve resiliency with highdegree, the paper focused on wireless mesh network among
the different communicating entities in BAN. To the best of
our knowledge, simulation study towards the fault-resilient
communication network for monitoring and control of WPF
has not been considered.
In this paper, we extend our previous work titled“Simulation Studies of Resilient Communication Network
Architecture for Monitoring and Control Wind Power Farms”[7]. First, we explore various topologies that can be applied tothe communication network for WPF. The advantages anddisadvantages of each topology are discussed. Then,fault-resilient communication network architecture withhybrid topology is proposed. To achieve fault-tolerance in the
network with a higher degree, we considered redundantresources at WPF, offshore platform, and control center level.
The IEC 61400-25 standard is used for monitoring various
components of WT. The standard mapped the physicalcomponents of WT into different logical nodes (LNs). Someof the LNs are mandatory while the others are optional. These
different kinds of LNs have different QoS requirements.
According to the IEC 61400-25 standard optional andmandatory LNs, the monitoring data are classified into criticaland non-critical data to satisfy the QoS requirements. Several
network failure scenarios are simulated through OPNET toevaluate the proposed architecture performance. The
performance of the communication network architecture isanalyzed in terms of end-to-end delay, data loss, and theamount of received data.
The rest of this paper is organized as follows: related work
is discussed in Section II. The different network topologies
and the proposed communication network architecture arepresented in Section III. WPF communication network withdata modeling and simulation set-up is given in Section IV.
Simulation results and discussion is presented in Section V.
Finally, Section VI summarizes the paper with concluding
remarks and related future work.

network diagram. The network is equipped with redundantdevices both at offshore (WPF site) and onshore (CC)locations. All the communication is made through the primary
wired link. This wired link uses a single mode fiber with link
bandwidth of 1Gbps to support the 80 WTs traffic and cover
longer distance between WPF and CC. An open platform
communication (OPC) interfaces are enabled within the
network equipment. The data is transmitted through filetransfer protocol (FTP), serviced by TCP/IP. The secondary
wireless radio communication channels use a 34Mbps
channel bandwidth. The secondary wireless channel has theadvantages of low installation cost, simple configuration, andis easy to deploy. When the primary link fails the traffic isrouted to the secondary wireless channels for datatransmission. However, some of the limitations associatedwith this architecture are: According to the IEC 16400-25
standard LNs, a WT generates approximately 1.8 Mbps ofmonitoring data [9]. In the case of Horns Rev WPF the fiber
link has a huge capacity of 1Gbps which is not utilized. Also,
the secondary wireless channels have a limited bandwidth of
34 Mbps. The limited channel capacity may result in data loss
with an increased latency. Furthermore, different applications
require different service qualities but the Horns Rev WPF do
not consider any QoS requirements.

Fig. 2. Horns Rev Communication Network

II. RELATED WORK
A. The Horns Rev Communication Network
Elsam, a Danish energy company, installed the first largest
offshore WPF in the North Sea. It consists of 80 Vestas
V80-2.0 MW unit WTs with 160 MW power capacities. The
80 WTs are connected in 10 rings with a total of 8 WTs ineach ring. The network architecture is designed with a
primary wired and secondary wireless radio communication
channels [8]. Fig 2 shows the Horns Rev communication

B. The Greater Gabbard Project Communication Network
The Greater Gabbard project is developed by Scottish andSouthern Energy (SSE) Company. The project covers a loadof 40% with a total annual production of 1,900-GWh
electricity. The project consists of 140 WTs with 3.5 MW
power generations for a WT. The turbines are located aroundtwo sand banks called Inner Gabbard and the Galloper in the
North Sea, off the coast of Suffolk in Eastern part of England.
The total distance of these wind farms is about 25 kilometers

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ICACT Transactions on Advanced Communications Technology (TACT) Vol. 4, Issue 5, September 2015

off the coast. The turbines are installed in water depths ofbetween 24 and 34 meters. The WTs are connected to twotransformers located at the offshore platform via 33kv cable.
The power is then exported to the onshore substation through132kv submarine cable. The WPF is connected to the onshore
substation through three different set of backbone gigabit
Ethernet based communication networks. The network
infrastructure consists of 8-rings connected to offshore
substation with 10-20 switches. Each of the communication
networks is designed to support different type of applications.
A virtual local area network (VLAN) is used to isolate thetraffic for each of the application. The RSTP protocols are
adopted for network loop avoidance and traffic re-routing incase of any failure in the network. The details of these
dedicated networks are discussed as follows.
 Balance of plant network: This network is called as“substation protection and control network” withthe main function to connect all the protection andcontrol IDE’s at WTs, offshore and onshore
substation.
 Wind turbine generator network: The WT
controllers are connected to central supervisory
controlled and data acquisition (SCADA) control
system through Ethernet communication link.
 Telephone and security network: The video
surveillance cameras and IP telephony services areprovided by this network.
All these networks are connected to the onshore substation
through gigabit Ethernet backbone with redundant switches
and routers [10]. The network provides resiliency with higher
degree using ring topology and redundant network resources.
The QoS can be achieved through independent network foreach application. However, some of the associated limitations
are: the physically connected network is logically separated
through VLAN for three different types of applications. The
VLAN can cause an increasement in the delay of sensitive ortime critical data. Another limitation is the cost factor,
because the network infrastructure is fully connected with abundle of resources (network switches and links) whichassociates a high cost. Hence, in view of cost it cannot be
considered as an optimized solution.

687

solution. Fig. 3a and Fig. 3b show the two kind of linear
topology.
Star Topology: All WTs are connected to the Ethernet
switch (ESW) of a central WT. This ESW operates as acoordinator for all the others WTs. The central WT has apoint-to-point communication link with the offshore platform.
A second kind of this topology is star-ring topology. All the
WTs are connected to the central WT through a ring topology.
The star topology is simple to setup and configure where thestar-ring is more robust. However, failure of central WT instar topology could result in disconnecting the reaming WTs.
The star-ring topology is more robust than simple star, but inthis case failure of central WT results in linear topology. Fig.
3c and Fig. 3d show star topology and star-ring topology,
respectively.
Ring Topology: In this topology, all WTs are connected inring. This topology is high robust, simple, and cost effective.
The failure of WT or link does not affect the communicationof other WTs. A point-to-point redundant communication tothe offshore platform provides a higher reliability in the
network. Ring topology can be a fully connected or partiallyconnected. The fully ring-topology is more reliable and robust
but require more cables, devices and ports. Fig. 3e and Fig. 3f
show the partial and fully connected ring topologies.

a) Linear topologyb) Linear topology with direct linkc) Star topologyd) Star-ring topology

III. PROPOSED FAULT RESILIENT COMMUNICATIONNETWORK ARCHITECTURE FOR WPF
In this section, we discuss various communication network
topologies that can be used for monitoring and control of
WPF. Then, we define the level of the communication
network architecture according to the network topologies.
A. Communication Network Topologies
Linear Topology: In this topology the WTs are connected
in a point-to-point communication link. The communication
among WTs, offshore platform, and CC is carried out throughthe same point-to-point links. The advantage of this type of
topology is that, it is simple to install and configure. However,the failure of a node/link results in disconnecting rest of the
WTs. A variation of this topology is that each of the WT is
directly connected to the offshore platform with a separate
dedicated link. In this case the failure of a link/node does notaffect the communication of other WTs. However, in view ofcabling requirements and cost, it is a complex and costlye) Fully connected ring
Primary linkf) Partial ring
Backup link

Fig. 3. WPF Communication Network Topologies

B. Three Level Communication network architecture
In this study, we consider an Ethernet based resilient
communication architecture for WPF. A schematic diagram isshown in Fig 4. To obtain reliability with a higher degree, theaforementioned architecture is divided into three levels: data
generation level, data aggregation level, and control center
level. Each level is based on a specific function, location, andnetwork topology. To maintain fault-tolerance in the network,
each level has redundant network resources. The WPF and
offshore platform are located at offshore site while the CC is

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ICACT Transactions on Advanced Communications Technology (TACT) Vol. 4, Issue 5, September 2015

located at onshore. Rapid spanning tree protocols (RSTP) are
adopted to avoid loop in the network. The following section
describes these levels in detail.
Data generation level (DGL): Embedded sensors
continuously monitor the components of WTs at DGL. EachWT has a WT controller (WTC) at its bottom. An ESW
located at WTC maintains communication with previous andnext WTC through an Ethernet link. The WTs within the WPF
is connected through partial ring topology. The partial ring
topology provides resiliency with higher degree at the DGL.
The WPF is connected to the offshore platform throughpoint-to-point connection. The resiliency between WPF and
offshore platform is achieved through a secondary
point-to-point link. The traffic is routed to the alternate
backup link if the primary link fails.
Data aggregation level (DAL): DAL is the middle levelof the communication network architecture between WPF and
CC. The function of this level is to aggregate the WPF data to
the CC. The offshore platform has redundant resources tomaintain primary and secondary links. Primary ESW
maintains a point-to-point primary link while the secondary
ESW is reserved for backup. To provide resiliency withhigher degree the primary and secondary ESW at this level arealso connected through point-to-point link.
Control center level (CCL): The CC collects data throughthe offshore platform for processing. Control commands arethen transmitted to WTs within WPF for appropriate action
using primary and/or secondary link. At CCL the SCADA
systems are connected through LANs using star topology. The
resiliency at this level is achieved through redundant switches
and links. The secondary network resource is used with the
failure of primary network resources.

Ring topology

Within the CC the devices are connected through local area
network using star topology. All the monitoring and control
operations are performed through primary ESWs and links.
For resiliency reserved backup network resources are used ateach level of the architecture.

IV. WPF NETWORK MODELING
A. Traffic Modeling
The integration of WPFs into electricity grid explores new
requirements in communication capabilities of WTs andelectricity grid. The standard information model andcommunication system can make it possible to integrate the
WPF into the electricity system. The IEC standard series
16400-25 defines a standardized way for accessing wind
power data [11]. As discussed previously that this standard
relates the components of WT into LNs. This work considers
nine LNs including WROT, WTRM, WGEN, WCNV,
WNAC, WYAW, WTOW, WTRF, and WMET. These LNs
are categorized into status, analogue, and control information.
Each category is sub-divided into different attributes. Table I
shows the details about WROT and its associated attributes[12]. In accordance to the mandatory and optional LNs
concept, we classified the WT monitoring data into criticaland non-critical data to support different QoS requirements.
Table II shows the critical and non-critical data for one WT.

StatusInformation
Analogue
Information
Control
Information

C. Proposed fault-resilient communication architecture
The proposed communication network architecture isbased on hybrid network topology. The proposed architectureis shown in Fig 5. A partially connected ring topology is used
to connect WTs within the WPF at the DGL. The WPF,
offshore platform, and CC communicate through a
point-to-point linear link.

Star topology

Fig. 5. Proposed architecture with hybrid communication network Topology

Category

Fig. 4. Schematic diagram of network architecture with three levels

Point-to-Point topology

688

TABLE ISUB-ATTRIBUTES FOR WROT LN
Attribute
Explanations
RotSt
Status of rotor
BlStB1
Status of blades
PtCtlSt
Status of pitch control
RotSpdValue of rotor speed at rotor side
HubTmpTemperature in the rotor hub
PtHyPresB1 Pressure of hydraulic pitch for blades
PtAngValB1 Pitch angle for blades
BlkRotSet rotor to blocked position
PtEmgChk
Check emergency pitch system

TABLE II
CLASSIFICATION OF WT CRITICAL AND NON-CRITICAL DATALN Class Description
M/O
Type
WROT
WT rotor information
M
WGEN
WT generator information
M
Critical Data
WNAC
WT nacelle information
M
WYAW
WT yawing information
M
WTOW
WT tower informationO
WMET
WPF meteorological information O
Non-critical
WTRF
WT transformer information
O
Data
WCNV
WT converter informationO
WTRM
WT transmission informationO

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ICACT Transactions on Advanced Communications Technology (TACT) Vol. 4, Issue 5, September 2015

Measurement
Temperature
Speed
Pressure
Pitch Angle
Vibration
Voltage
Current
Power
Power Factor
HumidityWind Direction
Wind Speed
Displacement
Oil Level
Frequency
TorqueStatusTemperature

Sampling Frequency
1 Hz
3 Hz
100 Hz
3 Hz
200 Hz2048 Hz
2048 Hz
5 Hz
1 Hz
1 Hz
3 Hz
3 Hz
10 Hz
1 Hz
10 Hz
50 Hz
1 Hz
1 Hz

TABLE IIIWT MONITORING MEASUREMENTS
Number of Channels
Data Transmissions(bytes/s)
1
2
1
6
1
200
1
6
3
1200
3
12288
3
12288
1
10
1
2
1
2
1
6
1
6
2
40
1
2
1
20
3
300
1
2
1
2
Total

The WT monitoring traffic depends on the sampling
frequencies, the number of channels, and the number of
sensors nodes. Table III shows monitoring measurements for
102 sensors. In our previous work we, proposed multilayer
communication network architecture for WPF [13]. We
considered 102 sensors that generate a total of 225,602
byte/sec (approximately 1.8 Mbps) monitoring traffic for a
WT. The following formula is used to calculate themonitoring traffic for one WT.
Data rate = 2*NC*FS
Where NC is the number of channels or measurements devices(sensors) and FS is the sampling frequency of each device.
Each sample is of 2-byte in size. For example the vibration
sensor generates 200 samples/sec, thus the total amount oftraffic is 1200 byte/sec for 3 channels with 2 byte of data foreach sample. Based on mandatory and optional data shown in
Table I, the WT critical and non-critical monitoring traffic
can be calculated. Table IV shows the critical and non-criticaltraffic for stand-alone WT.
TABLE IVWT CRITICAL AND NON-CRITICAL TRAFFIC DATA
Traffic calculation for mandatory LNs
LN Classes
No of sensors
Data transmission byte/s
WROT
14
642
WGEN
14
73764
WNAC
12
112
WYAW
7
220
Sub-total
47
74,738 byte/sec
Traffic calculation for optional LNs
LN Classes
No of sensors
Data transmission byte/s
WTOW
4
8
WMET
7
228
WTRF
12
73740
WCNV
14
74060
WTRM
18
2828
Sub-total
55
150,864 byte/sec
Total
102
225,602 byte/s ≈ 1.8Mbps

By considering the above classification for critical andnon-critical data, Table V shows the amount of traffic for
single WT and for a small scale WPF consisting of 12 WTs.
The overall traffic is then summed up as cumulative traffic.

689

No. of Measurement Devices
16
3
7
6
2
12
6
2
2
3
3
3
2
4
1
1
29
16
102

TABLE VCRITICAL AND NON-CRITICAL TRAFFIC FOR SMALL SCALE WPF
WT/WPF monitoring data in Mbps
No of
WT/WPF
CriticalNon-critical
Total
WTs
data
data
Stand-alone WT
1
0.57
1.15
1.8
Small Scale WPF 12
6.84
13.81
20.64

B. Network Modeling
The communication network for WPF can be defined on
the basis of electric power system topologies. The authors inreference [14] defined various electric topologies for WPF.
To achieve high reliability the proposed communication
network architecture in this paper follows hybrid topology.
Fig 5 shows the OPNET [15] topology of a small scale WPF.
It consists of 12 Ethernet work stations. Each workstation
represents one WT. Offshore platform consists of primary andsecondary ESWs. WPF is connected to primary ESW throughprimary link while the secondary link maintains a secondary
connection. The CC uses three ESWs. The primary ESW
maintains a primary connection with offshore primary ESW.
The secondary ESW is used for backup/secondary connection.
Both the primary and secondary ESWs are connected to the
CC central ESW. The SCADA servers are connected to thecentral ESW. A link bandwidth of 100Mbps is used for the
primary connection to support the WPF monitoring traffic.
Similarly, link bandwidth of 10Mbps is used for thesecondary connection. A low link bandwidth for thesecondary link provides a cost effective solution. The
SCADA servers system supports critical and non-critical data
of WPF. In order to execute the network topology, different
type of OPNET objects are needs to be configured. In our
simulation scenarios, the following objects are used:
1. Application configuration: The application object is used
to define and configure the traffic according to the user
requirements. This object defines six common applications
including: HTTP, E-mail, video, FTP, Voice, and database. In
this work, we used this object as WT_Application andconfigure for two FTP applications (i.e. critical_app &non_critical_app) to generate two different types of WT
monitoring traffic at application layer of the OSI model.

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ICACT Transactions on Advanced Communications Technology (TACT) Vol. 4, Issue 5, September 2015

690

Fig. 5. OPNET Model for WPF Communication Network

2. Profile configuration: The profile object is used to create
user profiles, which can support one or more application. The
profile configuration defines the type of application to be used
for the transmission of the traffic between the communicating
nodes. It provides the starting and ending time for eachapplication within the profile. In our work, we used the profile
object as WT_Profile. This WT_Profile supports both criticaland non-critical FTP applications. All the Ethernet work
stations and server system support this profile. It enables thetransmission and receiving of the WTs monitoring data
between work stations and server systems across the network.
3. Failure recovery configuration: The failure recovery
object is used to configure different failure points for link andnodes. The configuration of this object defines the type of
failure, the time of failure (failure point), and the time ofrecovery (recovery time). In our simulation we used thisobject as Failure_Recovery. It is configured for primary link
failure and recovery at three different times.
4. QoS configuration: This object is required for resource
allocation to support the different QoS requirements. Thisobject mainly deals with the three queuing policies: First inFirst out (FIFO), Priority queuing (PQ), and weighted-fairqueuing (WFQ). These policies are discussed as follows.
4.1 FIFO Queue: The FIFO queuing discipline issimple as the first packet that arrives at a node is the first
packet to be transmitted. The buffer space is finite and thenodes (Switch or router) discard an incoming packet if thebuffer is full. This policy does not care, whether a packet isimportant or not. Hence it cannot support any QoS
requirements.
4.2 Priority Queue (PQ): In the PQ configuration eachpacket is marked with a priority in the IP Type-of-Service(ToS) field. The communicating nodes then maintain multiple
FIFO queues, one for each priority class. Within each priority
class, the packets are still managed in a FIFO manner. Thisqueuing discipline allows packets with a high priority to betransmitted before those with a low priority. The PQ policy
supports the QoS requirements for different application.

4.3 Waited-Fair Queue: In the weighted-fair queuing(WFQ) discipline multiple queues are maintained by thenodes. For each packet a weight is assigned in the ToS field of
the IP header. This weight effectively controls the percentageof the link bandwidth. According to the link bandwidth, ittransmits the data with high priority. The nodes manage the
WFQ services through round robin manner. In our simulation
model we configure the WFQ queuing policy to prioritize thecritical data over the non-critical data. Thus, the transmissionof critical data is guaranteed with secondary link in case of
primary link failure.

V. SIMULATION RESULTS AND DISCUSSION
The performance of the proposed fault-resilient
communication network architecture is analyzed throughend-to-end delay, data loss, and data received. Several link
failure and recovery scenarios are simulated. The firstscenario is normal network operation without any failure. The
result in Fig. 6 shows that the amount of data received, whichis 6.84 Mbps and 13.81 Mbps for critical and non-criticalmonitoring traffic, respectively. These results are validating
our simulation according to the numerical calculation in Table
V. The Fig. 7 shows that the end-to-end delay is 6.5 ms and9.5 ms for critical and non-critical monitoring data,
respectively.
The second scenario considers link failure. In this scenario,
the primary link is failed and recovered at three different
points. Fig. 8 shows the cumulative transmitted and received
traffic. The result indicates data drop in the received trafficwith the failure of primary link. This data drop is in total(cumulative) traffic, and it difficult to differentiate whether
critical or non-critical data are lost. This is because in this
scenario no QoS requirements are considered. This data dropis due to the fact, that with the primary link failure the traffic
diverts to the secondary link. The peak lines in the figure
shows the retransmission of the data packets in the waiting
queue. The third scenario considers QoS of requirements. The
WFQ policy configuration is adopted to prioritize the critical

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ICACT Transactions on Advanced Communications Technology (TACT) Vol. 4, Issue 5, September 2015

data. In this scenario, the primary link is also failed andrecovered at three points. Fig. 9 shows the amount of received
traffic for critical and non-critical monitoring data. The resultclearly indicates that with failure of primary link the
non-critical data is dropped. The transmission of critical data
is guaranteed. Thus the non-critical data are sacrificed for thetransmission of critical data. The result in Fig. 10 shows thatthe end-to-end delays are 69 ms and 353 ms for critical andnon-critical data, respectively. There are two main reasons forthis increased delay. First, the secondary link has a lower link
capacity. Second, the queuing delay is increased by the
packets waiting for retransmission at the time of primary link
failure.

691

Drop in non-critical data No loss in critical data

Fig. 9. Total amount of received data with primary link failure

353 ms13.81 Mbps
6.84 Mbps
69 ms
Fig. 6. Total amount of received data without failure

Fig.10. ETE delay with primary link failure

9.5 ms

6.5 msFig. 7. ETE delay under normal operation

Packets retransmission

Data drop

VI. CONCLUSION
In this paper, we proposed fault resilient communication
network architecture for monitoring and control of WPF inreal time. The proposed architecture was based on a hybrid
topology consisting of three levels: DGL, DAL, and CCL. At
the DGL, the WTs are connected in a ring topology. DAL
supports the connection through point-to-point linear
topology between the WPF and CC. The communication
network architecture was designed with different link
bandwidth of 100Mbps and 10Mbps for primary andsecondary link, respectively. The traffic of LNs was modeled
into critical and non-critical data according to the IEC
61400-25 standard. The monitoring data was prioritized by
WFQ policy according to the required QoS. We investigate
the end-to-end delay, data loss, and data received withdifferent scenarios. Under the normal, operation theend-to-end delay was about 6.5 ms and 9.5 ms for critical andnon-critical data, respectively. In the case of primary link
failure the data was lost. However, considering the QoS thecritical data (6.84 Mbps) was successfully received. The
non-critical data sacrificed for the transmission of critical data.
Thus it can be concluded that in the case of network fault the
proposed fault-resilient communication architecture can
support the transmission of critical data. In future, the work
will be extended for large scale WPF.

Fig. 8. The impact of primary link failure

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ICACT Transactions on Advanced Communications Technology (TACT) Vol. 4, Issue 5, September 2015

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Shahid Hussain (M’15) was born in 1982 at
Wazir Garhi, District Nowshera, Khyber
Pakhtunkhwa, Pakistan. He received his B.Sc in
mathematics 2002 and M.Sc in computer science
2005 from University of Peshawar, Peshawar
Pakistan. He worked as Network Administrator at
Pakistan Oilseed Development Board (PODB),Agricultural Research Institute (ARI) Tarnab
Farm Peshawar, Pakistan from July, 2005 to Oct.
2008. Then he joined CSD zonal office Peshawar
Pakistan as Network Engineer. He also worked as lecturer at department ofcomputer science, university of Peshawar, Peshawar Pakistan. He iscurrently working toward his MS in Computer Engineering at the Chonbuk
National University, South Korea. His research interests include wirelesssensor networks, and communication networks for next generation wind
power farms.

Young-Chon Kim: He received the B.S.,
M.S., and Ph.D. degrees from Korea University,
Seoul, South Korea, in 1980, 1982, and 1987,
respectively. He joined the Department ofComputer Engineering at Chonbuk National
University, Jeonju, South Korea, in 1986 and is
now a Professor in the School of Information
Technology at Chonbuk National University.
From 1989 to 1990, he was a post-doctorate
fellow at the University of California, Irvine. Also,from 1998 to 2000, he worked as a visiting researcher at the Network
Research laboratory at the University of California, Davis. He was awarded
Best Professor from the College of Engineering, Chonbuk National
University, in 2002. He was also awarded the Motorola Academic
Excellence award in 2003. His research interests include high-speed opticalcommunication networks, next generation IP networks, and broadband
wireless communication networks.

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ICACT Transactions on Advanced Communications Technology (TACT) Vol. 4, Issue 5, September 2015

693

A Practical RFID Grouping Authentication Protocol
in Multiple-Tag Arrangement with Adequate
Security Assurance
Jian Shen* ** *** ****, Haowen Tan****, Yongjun Ren****, Qi Liu****, Baowei Wang*****Jiangsu Engineering Center of Network Monitoring, Nanjing University of Information Science &Technology, China**Jiangsu Technology & Engineering Center of Meteorological Sensor Network, Nanjing Universityof Information Science & Technology, China*** Jiangsu Collaborative Innovation Center on Atmospheric Environment and Equipment Technology,
Nanjing University of Information Science & Technology, China**** School of Computer & Software, Nanjing University of Information Science & Technology, Chinas shenjian@126.com, tan halloween@foxmail.com, renyj100@126.com, qrankl@163.com, wbw.first@163.com

Abstract—Radio Frequency Identification (RFID) is considered
to be an authentication technology of great potential. Due tothe bright future of low-cost RFID tags in practical situations,the authentication towards multiple tags and tag groups has
become the research hotspot. However, there are many concerns
about the security risks and privacy issues in lightweight RFID
authentication scenarios. Many researches achievements havebeen made focusing on the existence of single tag in one object,while the arrangement that multiple tags attached to one object isout of consideration. In this paper, we propose a practical RFID
grouping authentication protocol in multiple-tag arrangementwith adequate security assurance. In our assumption, one object
to be authenticated is attached with a group of RFID tags.
The feedback towards various cases of the RFID tags is timely
provided, which is necessary in practical situations. Additionally,
the probable position and status of the object can be ascertained————————————————————————Manuscript received date is April 9, 2015. This work is supported by the
research fund from Nanjing University of Information Science and Technology
under Grant No. S8113003001, the National Science Foundation of China
under Grant No. 61300237, No. 61232016, No. U1405254, and No. 61402234,
the National Basic Research Program 973 under Grant No. 2011CB311808,
the research fund from Jiangsu Technology & Engineering Center of Meteorological Sensor Network in NUIST under Grant No. KDXG1301, theresearch fund from Jiangsu Engineering Center of Network Monitoring in
NUIST under Grant No. KJR1302, the 2013 Nanjing Project of Science andTechnology Activities for Returning from Overseas, the CICAEET fund, and
the PAPD fund.
J. Shen (corresponding author, phone: 86-25-5873-1400, fax: 86-25-58731323, e-mail: s shenjian@126.com) is with Jiangsu Engineering Center of
Network Monitoring, Jiangsu Technology & Engineering Center of Meteorological Sensor Network, Jiangsu Collaborative Innovation Center on
Atmospheric Environment and Equipment Technology, School of Computer &Software, Nanjing University of Information Science & Technology, Nanjing,
210044, China.
H. Tan is with School of Computer & Software, Nanjing University ofInformation Science & Technology, Nanjing, 210044, China, phone: 86-1515181-3390, fax: 86-25-5873-1323, e-mail: tan halloween@foxmail.com.
Y. Ren is with School of Computer & Software, Nanjing University ofInformation Science & Technology, Nanjing, 210044, China, phone: 86-1876187-0612, fax: 86-25-5873-1323, e-mail: renyj100@126.com.
Q. Liu is with School of Computer & Software, Nanjing University ofInformation Science & Technology, Nanjing, 210044, China, phone: 86-1855171-9567, fax: 86-25-5873-1323, e-mail: qrankl@163.com.
B. Wang is with School of Computer & Software, Nanjing University ofInformation Science & Technology, Nanjing, 210044, China, phone: 86-1391292-6757, fax: 86-25-5873-1323, e-mail: wbw.first@163.com.

with a number of tags combined with the object. Moreover, theprotocol is proved to offer enough security assurances and haveresistance to various attacks under the security analysis. The
regular operation of RFID system will not be severely damagedby the incidents occurred during the authentication process.
Keywords—RFID, lightweight, grouping authentication, multiple tag, security.

I. I NTRODUCTIONR

FID technology does not require line-of-sight contact
in the communication process, which is superior to thebarcodes. The basic structure of RFID system is composedof three parts: the reader, the BPS and the RFID tags. The
reader can contact with more than one RFID tags and acquires
related information from the tags. Consequently, the evidence
that one or more RFID tags are verified at the same time isgenerated after several communication passes. Note here that
the RFID tag cannot directly contact with the BPS. Instead,the reader performs as the bridge between the tag and the BPS.
As a result, the reader is assumed to have enough computation
power and storage. As a matter of fact, the communication
channel between the reader and the tag is not secure. The
transmitted information is vulnerable to eavesdropping as wellas other kinds of attacks. For example, the RFID tag releases
radio signals to the reader through the wireless channel. Thus
the location of the RFID tag can be acquired by the malicious
reader from eavesdropping only with small expenses. The
tracing towards the tag can be possible in this occasion.
The BPS, regarded as the database containing important
information, also plays the role of verifier which decides thevalidity of the generated evidence received from the reader.
Thus the BPS is considered to be trustworthy and reliable
during the entire authentication procedure. Actually the BPS
is assumed to have full authority of the entire RFID system.
The RFID tag, which can be divided into three varieties:
active tag, passive tag and semi-passive tag, is the most concerned RFID device that is vulnerable to security risks. Thanks
to the recent technology development, the cost of RFID tags

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ICACT Transactions on Advanced Communications Technology (TACT) Vol. 4, Issue 5, September 2015

has been dropped to a relatively low level. At the sametime, these low-cost tags have large probability to suffer fromsecurity attack and privacy leakage due to resource limitationin terms of computation, communication and memory. We
assure that these security and privacy problems can be solved
by adopting impeccable authentication protocols and secure
strategies. Note here that the RFID tag referred in this paper
is low-cost passive tag which gets power from the interaction
with the reader.
As a matter of fact, many RFID authentication schemes
have been presented in order to improve the security leveland guarantee the regular operations of the RFID system. The
researches focusing on grouping authentication of multiple
tags and tag groups have become the primary tendency in
RFID authentication field, while the security problems alongwith the privacy leakages remain barriers of practical use [1],[2].
As assumed in most of the protocols devoted to grouping
authentication, single RFID tag is attached on one object.
However, in the situation that the object is of big size, theRFID tag on a part of the object may not be within thecommunication range. Consequently, the object with otherparts of it staying in the communication range cannot be
identified. In other words, the detection probability of theobject with single tag is not large in practical situations. The
BPS cannot ascertain whether all parts of the object with large
size is precisely in the supposed position so that the controlling
power of the entire RFID system towards the objects is notadequate [3], [4], [5].
To meet the practical requirements, one object can be
attached with multiple RFID tags in different parts. In thisassumption, if all the tags on the object are identified, it isobvious that the object is well arranged in the right position.
Note that the RFID tags on the object guarantee the integrationof the object and increase the detection probability as well [6],[7], [8]. Even in the harsh situations where some tags on thesame object may be compromised or missed, the RFID system
can still identify the existence of the object with the rest of
the tags. On the other hand, the precise location of the object
can be arranged by identifying the tags, which indicates the
new attempt for locating on low-cost RFID tags.
In this paper we propose a practical RFID grouping authentication protocol in multiple-tag arrangement with adequate
security assurance. In our assumption, all the tags on one
object are considered as one tag group. The BPS takes control
of behaviors of all these tags and reader. The object can beplaced in the accurate spot with small deviation according toour design, which is practical and creative in real applications.
This paper is organized as follows. In the following section,
the related original protocols about grouping authentication
are presented in brief. The detailed scheme of the proposed
protocol is shown in Section III. Next is the security analysisof the protocol in Section IV. Then we conclude all this paper
in Section V.
II. R ELATED W ORK
Many RFID grouping authentication protocols have beenpresented with the purpose of offering enough secure require-694

ments and preventing possible attacks to the RFID system.
J. Saito and K. Sakurai [9] proposed the original grouping
proof using time stamp in order to alleviate the weaknessof the protocol presented by Ari Juels [10], [11]. Generally
speaking, it is the relatively earlier protocol in multiple tags
authentication. In this protocol, the reader derives the timestamp from database and submits it to all the RFID tags. The
tags of the protocol are divided into two parts: the ordinary
product tags and pallet tag. However, the entire RFID systemin this protocol does not provide enough resistance to replay
attack.
The chaining proof protocol is proposed in 2007 [12]. The
main idea of this protocol is to combine all the tags intended
to be authenticated together and form a chain with purpose of
integrity preserving. However, the identities of the tags underauthentication are transmitted in plaintext, which makes thetags vulnerable to illegal tracing. In addition, this protocol
also depends on certain reading order of the tags, which is
not convenient for practical situation.
Reading order independent grouping proof [13] is proposedin order to meet the practical requirements. In the assumption,
the reader has enough computational power and the pallet tag
can be merged into the reader. As a matter of fact, this protocol
is applicable for special use in supply chain. The structures thatthe reader is bound to the pallet tag offers new research topic.
H. Liu et al. proposed grouping-proofs-based authentication
protocol [14] for distributed RFID systems. In this protocol,
all the tags are divided into several groups and are sequentiallychecked. This protocol provides strong protection on privacy
and is resistant to various attacks. However, the checking
sequence of the tags is required to be arranged in advance.
A RFID authentication protocol for multiple tag arrangement [15] is proposed by S. Dhal and I. S. Gupta in 2014. In
the assumption multiple numbers of RFID tags are attached in
one object in order to increase the detection probability. Basedon it, we propose our grouping authentication protocol in thispaper, which is relatively available in the practical situations.
III. P ROPOSED AUTHENTICATION S CHEME
In this section we describe our RFID grouping authentication protocol which is available for the scenario that multiple
tags are attached to one object with large size. Note that thesetags in one object are classified into the same tag group. In ourassumption, the sequence numbers of the tags in the group aredelivered to the reader after mutual authentication with eachother. We would like to emphasize that the real identifiersof the RFID tags are not used in our protocol, preventing the
RFID system from tracing problem. The reader communicateswith each tag according to their sequence number of the groupand gathers all the secret information to generate the proof.
The authentication process completes when all the tags in thegroup are verified successfully, which means that the tags arein the right position so that the object is safe and well arranged.
In addition, unusual situations are under consideration [15],[16], [17]. For example, when some of the tags are broken ordamaged, the reader can generate the proof containing othertags’ secrets. Consequently, the BPS acquires the information

Copyright ⓒ 2015 GiRI (Global IT Research Institute)

ICACT Transactions on Advanced Communications Technology (TACT) Vol. 4, Issue 5, September 2015that some specific tags need to be repaired but the object
remains safe, which is practical in real applications.
A. Problem Definition
We assume the occasion that a set of objects with large
size need to be verified where each of the objects is attachedwith more than one RFID tags in its different parts. Notethat the tags combined with the same object are considered
as one tag group. The object is arranged to be successfullyauthenticated after all the tags of the tag group are fully
verified, which guarantees that the object is precisely inthe scheduled location. The proposed RFID authentication
scheme should meet most of the security requirements without
affecting its efficiency or increasing the cost. Moreover, the
BPS should be available with the feedback of all the tags ofthe group. The disabled tag should be notified to the BPS for
convenience of the facilities maintenance. Hence the invalid
tag can be removed from the RFID authentication system intime.
B. Protocol Design
The protocol we propose in this paper is divided into fourphases for better description. In the initialization phase, theRFID tags are initiated with group identifiers along with thesequence numbers as soon as being attached to the object.
The number of the tags in the group g is assumed to ben. The reader acquires n tags’ identities and combines themwith the received random numbers from the BPS in the tag
acquisition phase. The proof of group g is generated in themain authentication phase, which links the entire tag group.
In the verification phase, the proof is delivered to the BPS.
It is necessary to emphasize that the communication between
the BPS and the reader and through secure channel, whilethat between the reader and the RFID tags are not safeand vulnerable to various attacks. The notations used in our
proposed protocol are provided in Table I.
TABLE INOTATIONS
Notation
BPS
Rm
g
Ti
n
rRm
IDRm
GIDg
rTi
ei
Sg
re1 , ..., rei , ..., ren
STi
ZGIDg

Description
Backend processing system
The m-th reader
The g-th tag group
The i-th tag of tag group g
Number of tags in tag group g
Pseudo-random number generated by the BPS
Identifier of reader Rm
Group identifier of tag group g
Pseudo-random number generated by the tag Ti
Sequence number of the tag Ti
Group secret of the tag group g
Pseudo-random numbers generated by the BPS
Secret of the tag Ti
Generated proof of the tag group g1) Initialization Phase: In this phase, the initialization of
the RFID tags is conducted. As we describe above, one object
is assumed to be combined with several tags in order to ensurethat this object is totally in the right position. The group
information as well as the sequence number ei is input in695

the memory of RFID tag. Note that the tag referred to here
can be the reusable tag, which means that the RFID tag canbe attached to another object after the authentication process
is completed. In this assumption, the tag will be through theinitialization phase again and equipped with new secrets.
2) Tag Acquisition Phase: In this phase, the tags responding to the reader are registered after verification. According toour design, it is not necessary for the RFID system to collect
all the n tags. The RFID system allows authentication towards
more than one tag. We assume there are j tags in group that are
successfully registered. When in extreme situations, only one
tag which passes the authentication of the RFID system canprove that the object is not missing. But whether the object isprecisely in the right position remains a question.
The detailed steps of this phase are as follows:• The BPS generates a pseudo-random number rRm forthe reader Rm . Then the BPS chooses the tag group to
be authenticated and delivers (IDRm , GIDg , rRm ) to thereader Rm through secure channel.
• The reader Rm computes Mg = (GIDg ⊕ IDRm ) + (Sg ∨rRm ) and broadcasts (IDRm , Mg , rRm ) to all the tags.
• The tag Ti of group g checks the validity of the received
Mg and generates its own pseudo-random number rTi .
Then Ti computes NTi = Mg − (GIDg ⊕ IDRm )] ∨ rTi
and QTi = ei ⊕ (Sg ∨ rTi ). Next the tag Ti responds(NTi , QTi , rTi ) to the reader Rm .
• After receiving the information form the tag, the reader
Rm checks validity of the acquired NTi and derives
ei from QTi . After all the n tags have been collected or the timer has timed out, the reader sends(IDRm , GIDg , e1 , ..., ej ) to the BPS in the secure way.
• The BPS compares the received information withdata in the database and replies to the reader with
(IDRm , GIDg , re1 , ..., rej ), where re1 , ..., rej denote thepseudo-random numbers generated for each tag separately. The reader stores all this in its memory for theauthentication in the next phase.
The brief description of this phase is shown in Fig. 1.
3) Main Authentication Phase: As the important sectionof the entire authentication process, this phase focuses ongathering the secrets of each tag and combining them following their sequence numbers ei . Instead of using the tag’s
identifier, we compute TempIDTi as the temporary identifier
during the communication between the reader and the tags,
which shows enough resistance to the tracing problem towards
the RFID tags. In the authentication process, the reader will
not terminate the authentication process when the requested
tag does not give the respond. Instead, the reader will skip to
the next tag after the timer times up. The entire RFID system
will not be interfered by abnormal tags or tag groups, whichmakes it more efficient.
The detailed steps of this phase are as follows:• The reader Rm computes rT0 1 = rT1 ⊕ re1 andTempIDT1 = (GIDg ⊕ e1 ) ∨ (rT0 1 ⊕ IDRm ) and delivers(QT1 , TempIDT1 , F irst, re1 ) to the first tag in group g.
• The first tag T1 checks the validity of the received
TempIDT1 from the reader and computes ZGIDg =Copyright ⓒ 2015 GiRI (Global IT Research Institute)

ICACT Transactions on Advanced Communications Technology (TACT) Vol. 4, Issue 5, September 2015

696

Fig. 1. Tag acquisition phase of the proposed protocol

TempIDT1 ∨ (re1 + ST1 ) and CT1 = (e1 ⊕ rT0 1 ) ∨ NT1 .
Then (TempIDT1 , CT1 , ZGIDg ) is replied to the reader.
• The reader checks the validity of CT1 and sends(QT2 , TempIDT2 , ZGIDg , re2 ) to the next tag of the group.
• The tag T2 computes ZGIDg = [TempIDT2 ∨ (re2 +ST2 )] ⊕ ZGIDg and CT2 = (e2 ⊕ rT0 2 ) ∨ NT2 . Note that
ZGIDg is generated with the value from the previous tag
T1 .
• The process continues to operate in this way and finallythe reader acquires private secret information of all theactivated legal tags.
The brief description of this phase is shown in Fig. 2.
4) Verification Phase: In this phase, the reader sends thegenerated proof ZGIDg as well as the sequence numbers of all
the legal tags to the BPS through secure channel. When all
the tags in group g pass the authentication, it is certain thatthe object is in the right place. However, if only some of thetags are successfully authenticated, we can still guarantee thatthe object is here, while it is not totally in the right place.
In addition, the BPS can be aware of the identities of thedisabled tags, which is convenient for facilities maintenancewithout checking all the tags.
The brief description of this phase is shown in Fig. 3.
IV. S ECURITY A NALYSIS
In this section, we analyze the security properties of our
protocol in order to prove that our protocol is reliable. The
proposed protocol is resistant to various kinds of attacks. The
RFID system has large potential in the practical situations
because it is convenient for the system to deal with different
kinds of occasions. Moreover, only simple computations are
required for the RFID tag, which is appropriate for market
promotion of low-cost passive tags. In addition, the key information of the tag is preserved in every communication session,
showing strong privacy protection to the tags. In addition, theFig. 2. Main authentication phase of the proposed protocol

Fig. 3. Verification phase of the proposed protocol

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ICACT Transactions on Advanced Communications Technology (TACT) Vol. 4, Issue 5, September 2015

proposed protocol is resistant to the tracing problem towards
the specific RFID tags. The BPS takes control of all theauthentication processes and can monitor the changes of theentire system, which improves the security and is available forpractical use.

697

important facility of the entire RFID system, the reader and the
BPS are assumed to be well protected in safe place [1], [10],[18]. As a result, physical attacks towards the reader and the
BPS are not taken into consideration in this paper. As a matterof fact, we attach significance to the security requirements of
the RFID tag more than the reader and the BPS.

A. Replay Attack
In our protocol, the pseudo-random number generator is in
use with the purpose of preventing the replay attack. As we
describe above, in the tag acquisition phase, the random numbers rRm and rej are all generated by the BPS and delivered to
the reader through secure channel. In this situation, the BPS
takes full control of the key generation. As for communication
between the reader and the RFID tags, the tag itself generates
the random number in the tag acquisition phase of every
session. Thus the reuse of the previous messages cannot pass
the verification of both the tag and the reader. As a result, thereplay attack is prevented.
B. Eavesdropping
The malicious reader may try to get the secret information
through eavesdropping during the communication process,which is the most common way for the adversary to damage
the RFID system. In our scheme, the identifiers of the tags
as well as the secret keys are all under encryption. We apply
temporary identifier TempIDTi to the communication between
the tag and reader so that it is not easy for the adversary to acquire key information of the specific tag througheavesdropping. The transmitted messages don’t directly reveal
the identifier of the tag so that the detected information is
unreadable for the adversary. Moreover, the BPS takes controlof the generation of all the random numbers. Consequently,
these random numbers are necessary ingredients of the final
generated proof, which ensures the variability. As a result, theentire RFID authentication system in our protocol is resistantto eavesdropping.
C. Physical Attack
In our design of this protocol, we assume that the adversary
is able to destroy the tags physically and get all the secret
information of the destroyed tag. The physical attack is always
possible if the adversary can get access to the RFID tag
physically. In this situation the detailed information stored in
the memory of the tag is not safe anymore. The adversary
can get full authority of the RFID tag and acquire the secret
information. In RFID authentication field, physical attackis inevitable so that we have to take it into our security
consideration. Our purpose is to ensure that the entire RFID
system will not be compromised because of the acquired
information from the tag. In some occasions, the adversary
may even manage to clone the tag and use it to cheat the
RFID system. However in our protocol, one object is attachedwith a group of RFID tags. The object can be authenticatedwith several disabled tags in the group. In order to interrupt
the authentication process, the adversary has to damage all
the tags in the group, which is difficult and worthless. As theD. Man-In-The-Middle Attack
Our protocol is resistant to man-in-the-middle attack. As
we describe above, in our protocol, the adversary cannot
collect the ID or secret key of the tag. In the main authentication phase, we assume the situation that the message(TempIDTi , CTi , ZGIDg ) sent by the RFID tag is blocked
by the adversary. The adversary cannot get the real ID andsequence number of the RFID tag. The reader will skip to
the next tag after the timer times out, and the object canstill be recognized without the message of the blocked tag.
In conclusion, the man-in-the-middle attack is prevented [15],[19], [20].

E. Tracing attack
In the RFID authentication area, tracing attack towards
the RFID tag, especially the low-cost passive tag, remains
big threat to both the RFID system and the users of the
RFID tags. Tracing attack can be classified into two kinds:
tracing attack during the session and tracing attack between
two successful sessions. On the one hand, in order to prevent
tracing attack during one session, the delivered messages
between the reader and the tags are all under encryption. The
use of temporary identifier provides strong protection throughtracing during the session. On the other hand, with the useof random number rT0 i , the temporary identifier of the tag ischanged after every successful authentication session. Thus itis difficult for the adversary to trace the specific tag throughthe relevance between two successful authentication sessions.
As a result, tracing attack between two successful sessions isstill impossible.

F. De-Synchronization Attack
In the de-synchronization attack, an adversary disturbs theinteractions between a tag and a reader by intercepting or
blocking the messages. In our protocol, the real ID of the tag is
not applied in the authentication process. Instead, temporary
identifiers are used in our protocol and these identifiers areavailable for one session. As a result, it is not necessary forthe low-cost RFID tags to update their secrets in every session.
In addition, the RFID tags are relatively independent of eachother. The privacy information stored in one tag is not relevantto that of the others. The compromising through single tag
will not affect the entire group and the RFID system. In thisoccasion, if one or more tags are blocked for several times,
the tags can also contact with the reader. In a word, the RFID
tags in the group will not suffer from de-synchronization attack
according to our design [15], [21], [22].

Copyright ⓒ 2015 GiRI (Global IT Research Institute)

ICACT Transactions on Advanced Communications Technology (TACT) Vol. 4, Issue 5, September 2015

G. Forward Security
In our protocol, if the adversary obtains the secret information of the RFID tag in the present session, the secure
information of the previous sessions will not be leaked tothe adversary. The temporary identifier in every session is
generated and valid only in the present session, which meansthat the secret information is not related to the previous
session. The secret information as well as the identifier ofthe RFID tag will be initialized at the beginning of every
authentication session. The adversary cannot acquire essential
messages of the previous sessions from the compromised tag
since the information is only used for one session. In a word,
the forward security property is provided in the proposed
protocol.
Comparison of security assurance: We have compared the
proposed protocol with some existing RFID authentication
protocols. The result of the comparison is given in Table II
below. The possible attacks are specified using the symbols a,b, c, etc. The meanings of the symbols are written under thetable.
TABLE IICOMPARISON RESULTGrouping proof [9]Chaining proof protocol [12]GUPA [14]APCMA [15]
Our protocol

a
N
Y
Y
Y
Y

b
P
P
Y
Y
Y

c
N
N
N
N
Y

d
N
P
Y
Y
Y

e
N
N
Y
Y
Y

f
P
N
Y
Y
Y

g
N
P
P
Y
Y

a: Replay attack, b: Eavesdropping, c: Physical attack, d: Man-inthe-middle attack, e: Tracing attack, f: De-synchronization attack, g:
Forward security, Y: Satisfy, N: Not satisfy,P: Partially satisfy

V. C ONCLUSION
In the grouping authentication of RFID tags, the use ofmultiple tags in one object not only increases the detection
probability, but also provides the chance for accurate positioning of the object, which satisfies the practical requirements.
In this paper we propose a practical RFID grouping authentication protocol in multiple-tag arrangement with adequate
security assurance. In our assumption, the entire authentication
process is in the control of the BPS. The feedback towards
various cases of the authentication process is also provided.
Moreover, with multiple tags combined with the object, theaccurate position of the object can be arranged. The RFID
system in our protocol shows enough resistance to various
attacks and security risks. We are working to improve ourprotocol in order to make it more efficient and practical in the
future work.
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ICACT Transactions on Advanced Communications Technology (TACT) Vol. 4, Issue 5, September 2015

699

Jian Shen received the B.E. degree from Nanjing
University of Information Science and Technology,
Nanjing, China, in 2007 and the M.E. and Ph.D. degrees in Computer Science from Chosun University,
Gwangju, Korea, in 2009 and 2012, respectively.
Since late 2012, he has been a faculty member in
the School of Computer and Software at Nanjing
University of Information Science and Technology,
Nanjing, China. His research interests include computer networking, security systems, mobile computing and networking, ad hoc networks and systems,
and ubiquitous sensor.
Haowen Tan received the B.E. degree in 2013 and iscurrently working toward the M.E. degree at Nanjing
University of Information Science and Technology,
Nanjing, China. He focuses on the security andprivacy issues in radio frequency identification. His
research interests include authentication protocol design, security formal modeling and analysis.

Yongjun Ren obtained the PhD degree in thecomputer and science department at the NanJing
University of Aeronautics and Astronautics, China,
in 2008. Now he is serving as a full time faculty in
the NanJing University of Information science andTechnology. His research interests include network
security and applied cryptography.

Qi Liu received his BSc degree in Computer Scienceand Technology from Zhuzhou Institute of Technology, China in 2003, and his MSc and PhD in
Data Telecommunications and Networks from the
University of Salford, UK in 2006 and 2010. His
research interests include context awareness, data
communication in MANET and WSN, and smart
grid. His recent research work focuses on intelligent
agriculture and meteorological observation systems
based on WSN.
Baowei Wang received his B.S. and Ph.D. degrees
in Computer Science from Hunan University in 2005
and 2011, respectively. He is currently working as alecturer in School of Computer and Software, Nanjing University of Information Science and Technology. His research interests include steganography,
wireless networks and securing ad hoc networks.

Copyright ⓒ 2015 GiRI (Global IT Research Institute)