International Journal of Application or Innovation in Engineering & Management (IJAIEM)
Web Site: www.ijaiem.org Email: editor@ijaiem.org, editorijaiem@gmail.com
Volume 2, Issue 3, March 2013
ISSN 2319 - 4847
Performance Analysis of Group Mobility
Handover in Wimax Networks With and
Without Group Leader Concept
Shalini E.1, Sundararajan T. V. P.2
1
PG Student, Department of Electronics and Communication Engineering, Bannari Amman Institute of Technology,
Sathyamangalam-638401, Erode, Tamilnadu
2
Professor, Dept of Electronics and Communication Engineering, Bannari Amman Institute of Technology,
Sathyamangalam-638401, Erode, Tamilnadu
ABSTRACT
Cheaper establishment, wider coverage area and high data rates, makes WiMAX (Worldwide interoperability for microwave
access) to be one of the most developing technology for offering wireless last-mile connection. Group mobility scenarios are
widely seen in military environment, emergency and rescue activities. Group mobility refers to the scenarios that multiple
mobile nodes (MNs) move in a group at the same time, usually in the same direction with a small distance of separation. There
are various challenges associated with group mobility concept. In the group handover mechanism in WiMAX networks,
initiation of the handover at the same time due to different users results in network congestion. So, when a group leader is
introduced, it paves a solution for this problem. The Group Leader integrates several handover processes for the group of MSs
into only one, which could eliminate the collision of the ranging requests from the individual MNs in a group in to a single
request and shorten the latency incurred in the network.
Keywords: WiMAX, Mobility Model, Group Mobility, Group Leader
1. INTRODUCTION
WiMAX is a fourth generation wireless communication technology and it is based on IEEE 802.16 specification which
is a standard for Wireless Metropolitan Area Network (WMAN). It is a promising technology that offers higher data
rate, supports large number of users and covers a larger area [1]. Mobility in a network describes the movement of the
nodes in the network. Group mobility is a concept in which a group of MNs moves at a same time particularly in the
same direction with small space of the interval between individual nodes in a particular group [2,3]. Military tactical
communication, disaster recovery, emergency and rescue operations are some of the widespread scenarios of group
mobility. Handover is one of the most essential process because mobile nodes cannot acquire contact to the same BS
during mobility [4]. There are various challenges associated with the concept of group mobility handover. In a group
handover mechanism, network congestion would occur as a large number of mobile nodes in a group initiates handover
at an equivalent time, which in turn raises the chances of handover blocking and also raises the handover latency due to
collision involved and the corresponding backoff. So, when a group leader concept is introduced, it paves a solution for
this problem. The Group Leader integrates numerous handover processes from the group of MN’s into single request,
which could eliminate the collision of the ranging request at the base station and reduce the latency found in the
network.
The work has been implemented using Qualnet version 5.0.2 and performance analysis is made between the network
With group leader and Without group leader respectively. The paper is structured as follows: Section II describes the
Related Work, Section III tells about the system architecture, Section IV deals with Results and Discussion and Section
V concludes the paper.
2. RELATED WORK
Mobility models depict the movement pattern, location, acceleration change over time and the velocity of the mobile
nodes. This movement pattern is responsible for determining the performance of the protocol. These mobility models
are classified based on the restrictions and dependencies as,
 Random based: Nodes move randomly and there are neither dependencies nor restrictions modeled
 Temporal dependencies: The movement of the past decides the movement of the nodes at present
 Spatial dependencies: The movement of a node is influenced by the nodes present around that node
 Geographic restrictions: The node movement is restricted to a particular area
Volume 2, Issue 3, March 2013
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International Journal of Application or Innovation in Engineering & Management (IJAIEM)
Web Site: www.ijaiem.org Email: editor@ijaiem.org, editorijaiem@gmail.com
Volume 2, Issue 3, March 2013
ISSN 2319 - 4847
 Hybrid characteristics: It is the combination of Temporal dependencies, Spatial dependencies and Geographic
restrictions
Figure 1: Different Mobility Models
Random Waypoint Model (RWP) [5] is a random model for the movement, their location, acceleration change over
time and the velocity of the mobile nodes. As they are random based mobility model, mobile nodes move freely and
randomly without any limitations. In this model, the destination, speed and directions are chosen randomly. Random
Walk Model and Random Direction Model are the variants of Random Waypoint Model. This model consists of pause
time between changes in direction or speed. When the specified pause time is crossed, the mobile node selects the
destination randomly and chooses the speed uniformly between the minimum and maximum speed and travels with the
speed of interval (0,
).
gives the degree of mobility. The mobile node moving towards the destination stays
there for the specified pause time and vice versa. This model is widely used in simulations due to its simplicity.
Random Walk Model is originally used for emulating the random movement of the particles which is also termed as
Brownian motion in physics. It is similar to Random Waypoint Model but with zero pause time. Here, the nodes can
change their speed and direction at each time interval. This model is a memory less mobility process in which previous
information is not used for taking the future decisions. In Random Direction Model, each node moves until they reach
the specified boundary of the simulation. After reaching the boundary, it again starts moving in another direction.
Gauss Markov model which is based on temporal dependencies is used to overcome the drawbacks of the RWP model.
According to this model, the node determines the new vector based on the past direction and speed. However, this
model is not widely used for simulation studies since the computational complexity of the movement of the node is
high, that is, it has larger trace file compare to RWP model. All these models are used for simulating the individual
mobile node but whereas Reference Point Group Mobility Model [3] is used for simulating the group behavior, where
each node belongs to a group with a group leader which determines the movement of the group. All the nodes in a
group are distributed randomly around the reference point. The nodes in a group may use different mobility model and
added to the reference point for driving the individual nodes in the direction of the group. Each node has a unique
speed and direction at every instant, which has been derived by randomly deviating from that of the leader of the group.
This makes it useful for creating a variety of models for different mobility applications. Such group mobility models are
used for military battlefield applications, where a number of soldiers move together in a group.
3. SYSTEM ARCHITECTURE
The work deals with the performance analysis of group mobility concept without group leader and With group leader in
WiMAX network respectively. A group that does not use the group leader concept for mobility found to introduce
much delay since heavy collision occurs at the base station due to the collision of requests from the individual base
station. So, a group leader introduction in a group overcomes this delay by integrating the ranging request from the
individual mobile nodes in a group into a single request to the base station. Here, the group leader selection is made
manually but not dynamically. The group mobility concept in this work is implemented in the WiMAX network.
Volume 2, Issue 3, March 2013
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International Journal of Application or Innovation in Engineering & Management (IJAIEM)
Web Site: www.ijaiem.org Email: editor@ijaiem.org, editorijaiem@gmail.com
Volume 2, Issue 3, March 2013
ISSN 2319 - 4847
WiMAX stands for Worldwide Interoperability for Microwave access is a developing technology which is a fourth
generation wireless technology with the standard IEEE 802.16. It is a broadband wireless access (BWA) system mainly
designed for the Wireless Metropolitan Area Network (WMANs).The standard IEEE 802.16-2004 is mainly designed
for providing broadband access to internet for the users who are fixed with small business and the standard IEEE
802.16e supports broadband access to mobile users resulting in Mobile Wimax [6 & 7].Thus IEEE Std 802.16e offers
improvement to IEEE Std 802.16-2004 for supporting users moving at vehicular speeds and thereby specifies a system
for combined fixed and mobile broadband wireless access (BWA) [8]. It plug-in the gap between the very high data rate
wireless local area networks and very high mobility cellular systems. Group Mobility scenario occurs mainly in the
military environment where a troop of soldiers moves from one location to the other. During movement, handover is an
essential process for switching the signal strength from one base station to the other. This handover causes latency in
the network due to the collision of the ranging request from the individual MNs in a group. The introduction of group
leader concept overcomes this drawback by adding the entire request from the MNs in a group into a single request.
4. SIMULATION RESULTS AND DISCUSSION
4.1Simulation Setup Of Group Mobility Scenario
The group mobility scenario is simulated using Qualnet 5.0.2. Two scenarios are constructed With Group Leader and
Without Group Leader respectively. These two scenarios are analyzed with different CBR connections and also based
on Throughput and jitter. Each scenario consists of two groups with the minimum of 2 nodes to the maximum of 10
nodes respectively. The simulation parameters used for scenario simulation is given in the table given below. The
scenarios are analyzed by varying the CBR connections. Figure 2 represents group mobility scenario with two groups in
WiMAX networks without Group Leader and one CBR connection. Here, nodes 1 to 10 are grouped as Group 0 and
nodes 11 to 20 are grouped as Group 1. As the number of CBR connection is increased, latency increases since the
network congestion increases which is analyzed from the scenario shown in the figure 3. Similarly figure 4 represents
the group mobility scenario with two groups in WiMAX networks with Group Leader and one CBR connection and
figure 5 shows the same scenario with 3 CBR connections respectively.
Table 1: Simulation parameters
Simulation time
Terrain
Propagation Model
Mobility
Traffic
Radio type
Transmission Power
No of mobility Groups
Minimum and Maximum speed of
Group 0
Minimum and maximum speed of
Group 1
Routing Protocol
300 seconds
1500 X 1500
Two ray propagation model
Group mobility
CBR
802.16
20 dBm
2 (Group 0 and Group 1)
40s and 60s
10s and 20s
AODV
Figure 2: Group Mobility between two groups without Group Leader with 1 CBR
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International Journal of Application or Innovation in Engineering & Management (IJAIEM)
Web Site: www.ijaiem.org Email: editor@ijaiem.org, editorijaiem@gmail.com
Volume 2, Issue 3, March 2013
ISSN 2319 - 4847
Figure 3: Group Mobility between two groups without Group Leader with 3 CBR
Figure 4: Group Mobility between two groups with Group Leader with 1 CBR
Figure 5: Group Mobility between two groups with Group Leader with 3 CBR
4.2Results and Discussion
4.2.1 Handover Latency
Handover latency is defined as the latency incurred in the network during the handover process from one base station to
the another base station. The figure 6 depicts that the handover latency is high for the network that does not uses Group
Leader and the network that uses more CBR connections since there is more collision of requests from the individual
MS in a group at the base station. The introduction of Group Leader integrates all these requests from individual MS in
a group into a single request and thus avoids latency in the network.
Figure 6: Handover Latency
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International Journal of Application or Innovation in Engineering & Management (IJAIEM)
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Volume 2, Issue 3, March 2013
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4.2.2 Throughput
Throughput is the amount of number of packets effectively transferred in a network, in other words throughout is data
transfer rate that are delivered to all terminals in a network. It is measured in terms of packets per second or per time
slot. Figure 7 shows the throughput performance for the scenarios Without Leader MS and With Group Leader
involving one CBR connection. Here, the throughput value is found to be high for the network that does not involves
Group Leader and similarly as the speed of the nodes gets increases there is decrease in the throughput subsequently.
Figure 8 depicts the throughput value for the similar networks with three CBR connections. Here, as the number of
CBR connections increases, there is a decrease in the throughput value due to increase in congestion involved the
network.
Figure 7: Throughput of the networks with 1 CBR connection
Figure 8: Throughput of the networks with 3 CBR
4.2.3 Average Jitter
Jitter can be observed as the end-to-end delay variation between two consecutive packets. The value of jitter is
calculated from the end to end delay. Jitter reveals the variations in latency in the network caused by congestion, route
changes, queuing, etc. It determines the performance of the network and indicates how much consistence and stable the
network is. The table 2 shown below depicts the average jitter value for a group with ten mobile nodes. It says that, the
jitter is high for the network that does not use Group Leader and for the network that uses more CBR connections.
Table 2: Average Jitter for a group with ten mobile nodes
Leader MS with 1
CBR
Leader MS with 3
CBR
No Leader with 1 CBR
No Leader with 3 CBR
0.0039
0.0042
0.0241
0.0455
5. CONCLUSION
In this work, performance analysis of group mobility handover With group leader and Without group leader is made in
a WiMAX network. The results depicts that the group with group leader reduces the latency incurred in the network by
integrating the ranging request from individual MNs in a group into a single request and thereby avoiding the delay
associated with the network. Throughput and Jitter is found to be decreased in the network with group leader concept.
It is also found that the network with more CBR connections has given least performance compare to the network with
one CBR connection.
Volume 2, Issue 3, March 2013
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International Journal of Application or Innovation in Engineering & Management (IJAIEM)
Web Site: www.ijaiem.org Email: editor@ijaiem.org, editorijaiem@gmail.com
Volume 2, Issue 3, March 2013
ISSN 2319 - 4847
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AUTHOR’S PROFILE
Shalini .E has received her B.E degree in Electronics and Communication Engineering from Anna University,
Coimbatore, 2011. She is currently pursuing her Master of Engineering in Communication Systems in Bannari
Amman Institute of Technology under Anna University, Chennai. Her areas of interest in research are
Wireless Communication & Wireless Networks. She has published 2 articles in international journal and 4
papers in national and international conferences.
T.V.P. Sundararajan received the BE Degree in Electronics and Communication from Kongu Engg. College,
Perundurai in 1993 and the ME Degree in Applied Electronics from the Government college of technology,
Coimbatore in 1999. He is Professor, working in Bannari Amman Institute of Technology, Sathyamangalam.
He has published 12 articles in National and International journals and more than 25 papers in International
and National conferences. He has completed his Ph.D research in Anna University, Chennai. His current
research focuses are on mobile ad hoc networks and wireless security. He is member of the IEEE, ISTE and
the IEEE computer society.
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