International Journal of Engineering Trends and Technology (IJETT) - Volume4Issue4- April 2013
Improved Quality of voice in mobile environment
using integrated WiMAX and WiFi
Karthika A L1, SumithraM G2, Shanmugam A3
1
1,2,3
M.E. Student, 2,3Professor
Dept. of Electronics and Communication Engineering, Bannari Amman Institute of Tech, Sathyamangalam, India
Abstract—In recent days, compare to fixed users, the mobile
users are increasing day by day.It becomes necessary to provide
better quality of data delivery to the end mobile user. Formerly,
the quality of data delivery at the destination is good for
pedestrian users when compared to the users in vehicular
environment. It is due to the lack of coverage of area. The
coverage area can be increased with the help of heterogeneous
network which improves the quality of service for vehicular
environment. In this paper, the integrated WiMAX-WiFi
networkis implemented and analyzed by comparing the
performance of vehicular environment and pedestrian
environment by transmitting the voice packets based on Mean
Opinion Score value, jitter, end to end delay and throughput.
IndexTerms—WiMAX, WiFi, Heterogeneous network, VoIP,
MOS
I. INTRODUCTION
Currently, internet is not only used for the transmission of
text and images but also used for voice and video transmission.
The efficient transmission of voice is done by VoIP which uses
traditional Internet Protocol to transmit the voice packets.
Since it uses the existing Internet Protocol [17], the cost for
voice/video transmission is low (transmission between mobile
phone and PC) or completely free (transmission between two
PCs). Example Skype, Oovoo.
The transmission of voice over VoIP is done better by
WiMAX [16]. But highly developed areas are using only WiFi.
Since WiFi is a wireless technology and have many benefits,
the number of fixed and mobile users in the particular coverage
area also increases. The users in pedestrian environment get
frequent connection to the network than the users in vehicular
environment especially train [23]. The solution to this problem
is integrating WiMAX and WiFi[15],since it is very difficult to
replace the WiFi with WiMAX and also many of the handset
supports WiFi and not WiMAX. This integrated network gives
better quality of voice by increasing the coverage area.
Generally, the increase in number of users and increase in
coverage area reduces the performance of voice transmission
also the clarity of voice at the destination. This drawback can
be easily overcome by the real time switches, routers, and
firewall.
A. Heterogeneous network
It represents the combination of two or more network into a
single network. The integration between the networks is easy
when they are infrastructure networks.
BS
AP
ss
Fig. 2. Heterogeneous network
Fig. 1. VoIP
The above diagram shows the VoIP calls function.
The voice quality is easily determined with the help of
Mean Opinion Score (MOS) value [19] which has the range of
1 to 5. The range 1 indicates the very poor voice quality and 5
denotes the better quality of voice at the destination. The MOS
value is of different types: Network MOS, Listening MOS,
Conversational MOS and Sending MOS. In this paper,
Network MOS is taken into account since it considers network
parameters like jitter, delay and voice codec used.
ISSN: 2231-5381
The figure 2 indicates the heterogeneous network where the
WiFi Access Point (AP) gets signal from the WiMAX Base
Station (BS). The user who can access both the network can
get signal from the network which gives high signal strength.
For example, if a man is between wifi AP and WiMAX BS,
and he can get both the signal, then he will choose one network
which gives better signal strength.
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International Journal of Engineering Trends and Technology (IJETT) - Volume4Issue4- April 2013
B. Pedestrian environment vs. Vehicular environment
voice application is mainly depends on the type of encoder
scheme and the MOS value which is described in paper [15].
The authors in paper [16] said that the distance plays an
important role in the transmission of voice. The shorter distant
communication has more latency than larger distance which is
due to interference is in paper [17]. The authors in paper [20][22] gave an idea about the scenario model for the
heterogeneous network.
III. SIMULATION RESULTS
Fig. 3. Pedestrian and Vehicular Environments
Figure 3 depicts the pedestrian and vehicular environment.
The pedestrianenvironment has the mobility speed as normal
walking speed of human and thevehicular environment has the
speed of mobility as the speed of modern train in China,Tokyo
and so on. The nodes in this set up is mobile i.e. move
frequently from oneplace to another. These mobile nodes are
connected to the server via wireless andwired link with the
help of server and switch. The wireless communication is
donebetween the node and the station and the wired
communication is made between IP andserver.
C. Simulation Tool
For networks and communication, there are many tools like
NS 2, Qualnet and so on. But when compare to these tools,
OPNET supports easy real time routers, switches. It also
provides broader coverage area which is very helpful in trying
out the interworking network architecture [18]. So in this
paper, the comparison between users in pedestrian
environment and improved vehicular environment is done with
the help of OPNET simulation tool.
II. RELATED WORKS
In paper [1] and [2], the authors said that the WiMAX
gives better quality of service with the help of UGS service
flow since it offers low jitter, low delay and high throughput.
The WiMAX is better for VoIP due to its cost, data rate and
coverage area [3]. The WiMAX gives guaranteed better quality
for real time applications and also for interactive audio and
video which has been reported in paper [4]. In WiMAX, the
64-QAM modulation gives better performance than adaptive
and QPSK is in paper [5]. The WiFi is very sensitive to delay
factor and packet loss and also has some challenges in security
issues due to increasing number of users which is reported in
paper [6]. In paper [7], the authors stated that the security
issues can be solved by using IPsec and firewall. It provides
data integrity, authenticity and encryption. In paper [8]-[11],
the authors said that the integrated WiMAX and WiFi covers
larger area and also reduces the cost. So the voice transmission
over this heterogeneous network is very efficient. The best
voice codec for the best voice at the end user is G.711 since it
gives good MOS value which is in paper [12] and [13]. The
authors in paper [14] described about the types of MOS values
and also offered the formula to calculate the MOS values. The
ISSN: 2231-5381
Fig. 4. OPNET Scenario model for both the environments
Figure 4 illustrates the outlook of mobile environment. The
three subnets contain the mobile nodes and its specifications.
TABLE I
PARAMETERS USED IN THIS SETUP
Parameters
No. of subnets
No.of nodes in
WiMAX& WiFi
Mobility of nodes
Application Coder
Traffic Type
Simulation Time
Simulation Area
Speed
Pedestrian
Environment
3
Vehicular
Environment
3
4 (each subnet)
4 (each subnet)
Mobile
G.711
VoIP
1 hour
100x100km
2.8 mph
Mobile
G.711
VoIP
1 hour
100x100km
302 mph
The above table shows the parameters that are used in this
simulation setup.
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Fig. 5. Voice Application: Jitter
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International Journal of Engineering Trends and Technology (IJETT) - Volume4Issue4- April 2013
As it is one of the important parameter for voice
application, the vehicular environment must have less jitter.
The above figure describes that the jitter is more for vehicular
environment at the starting time, since it takes some time for
the network to adapt to the router configuration. But after the
environment gets adapted to the configuration, the jitter got
reduced in it and its value is approximately equal to the value
of pedestrian environment.
i.e. approx. 15 mins, the delay for vehicular environment than
pedestrian but both are more or less same.
Fig. 8. WiMAX: Delay
Fig. 6. Voice Application: Network Mean Opinion Score value
Figure8 illustrates the delay for pedestrian environment and
vehicular environment. The delay is more for pedestrian
environment since the user moves from one place to another
place in a frequent manner. So it becomes very difficult to
deliver the voice to the destination.
Figure 6 says that the quality of voice in vehicular
environment achieves the voice quality in pedestrian
environment which is because of the integrated network which
gives more coverage area, less jitter (both are nearly 0.01sec)
at the receiver side and effective encoder scheme as G.711.
Here the NMOS value is above 4 which represent the good
voice quality.
Fig. 9. WiMAX: Throughput
As the delay and jitter is less for vehicular environment and
also the effective router and switch configuration is used, the
throughput gets increased. Figure 9 illustrates that the
throughput of vehicular environment and pedestrian
environment.
Fig. 7. Voice Application: End to End Delay
In figure 7, for first 8 mins, the end to end delay for
vehicular environment is 7% more than the pedestrian
environment which is due to the heavy traffic at the initial
stage. Later on this problem is solved with the help of getting
adaptive to the effective Cisco router. So after some more time
ISSN: 2231-5381
IV. CONCLUSION
In this paper, we proposed a heterogeneous network to
improve the quality of voice over vehicular environment. The
basic idea is to increase the coverage area by integrating
WiMAX and WiFi network and reducing the jitter and delay
by using effective router and switch so as to maximize the
voice quality in vehicular environment. In order to prevent the
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International Journal of Engineering Trends and Technology (IJETT) - Volume4Issue4- April 2013
network from attacks, the firewall and IPsec is implemented in
this paper. Finally, the experimental results show the better
performance at the end mobile user.
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