1. International Journal of Electronics and Communication Engineering & Technology (IJECET), ISSN 0976 –
INTERNATIONAL JOURNAL OF ELECTRONICS AND
6464(Print), ISSN 0976 – 6472(Online) Volume 4, Issue 5, September – October (2013), © IAEME
COMMUNICATION ENGINEERING & TECHNOLOGY (IJECET)
ISSN 0976 – 6464(Print)
ISSN 0976 – 6472(Online)
Volume 4, Issue 5, September – October, 2013, pp. 161-168
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IJECET
©IAEME
IMPROVEMENT OF IEEE 802.11G WLANS BASED ON RESPONSE TIMES
APPLICATION WITH RADIO – FIBER SYSTEM
Dr. Adnan Hussein Ali*, Dalal Abdulmohsin Hammood**, Amal Ibrahim Mahmood***
College of electrical and electronic techniques
ABSTRACT
The Wireless local area networks WLAN performance is a key factor in spreading and usage
of such technologies. The WLAN are more bandwidth limited as compared to the wired networks
because they depend on an inexpensive, but prone to errors, physical medium (air).Hence it is
important to improve their performance. Fibre-optic media will do better transmitting high frequency
radio signals over a longer distance because fibre-optic cables are immune to EMI and noise, provide
excessive bandwidth in the region of THz. Application response times are greatly improved
irrespective of the nature of the application.
Keywords: Wireless LAN, IEEE 802.11g, Radio–Fiber system, OPNET.
1.
INTRODUCTION
Wireless local area network (WLAN) technologies have emerged as a fast-growing market.
Among
the various WLAN technologies available in the market, IEEE 802.11 standard has
emerged as the dominating technology and is vastly used in WLANs. Low cost, ease of deployment
and mobility support has resulted in the vast popularity of IEEE 802.11 WLANs[1,2].
Fibre-optic media will do better transmitting high frequency radio signals over a longer distance
because fibre-optic cables are immune to EMI and noise, provide excessive bandwidth in the region
of THz, and are more secure[3].
OPNET (Optimized Network Engineering Tools) Modeler will be used to model a typical
enterprise wide area network (WAN) network having LAN and WLAN subnetworks as is found in
many installations today[4].
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2. International Journal of Electronics and Communication Engineering & Technology (IJECET), ISSN 0976 –
6464(Print), ISSN 0976 – 6472(Online) Volume 4, Issue 5, September – October (2013), © IAEME
2.
WLAN TECHNOLOGY
Future Wireless local area networks enable people on the move to communicate with anyone,
anywhere at anytime with a range of multimedia services. The wireless networks can be employed to
provide network connectivity almost anywhere, it provides large companies the option to connect the
current wired networks to the new wireless network without any problems and gives user the option
to use any kind of applications regardless of its source or vendors[5]. However, the WLAN
performance is a key factor in spreading and usage of such technologies. Also the Wireless local area
networks (WLAN) are more bandwidth limited as compared to the wired networks because they rely
on an inexpensive, but error prone, physical medium (air)[6].
Discrete event simulations are used as the means of analyzing the system performance and
behaviour. This sophisticated package comes with a range of tools, which allows us to specify
models in detail, identify the elements of the model of interests, execute the simulation, and analyze
the generated output data.
The IEEE released the 802.11 specifications in June 2000[7]. The initial specification, known
as 802.11, used the 2.4 GHz frequency and supported a maximum data rate of 1 to 2 Mbps then the
802.11b specification increased the performance to 11 Mbps in the 2.4 GHz range while the 802.11a
specification utilized the 5 GHz range and supported up to 54 Mbps[8]. The 802.11 standard focuses
on the two lower layers (1 and 2) of the Open System Interconnection (OSI) reference model.
After more than two years in the making, the IEEE 802.11g Draft Standard is nearing
completion. In terms of range and throughput, 802.11g is living up to its billing. It utilizes
Orthogonal Frequency Division Multiplexing (OFDM) technology in the 2.4 GHz band while
preserving backward compatibility with the large installed base of existing 802.11b equipment
(about 40 million units worldwide, and growing)[9]. OFDM was previously adopted for WLAN
applications as part of the IEEE 802.11a Standard (completed in 1999). Since 802.11g operates at 2.4
GHz, it provides much longer range than 802.11a based equipment because the lower operating
frequency has better propagation properties for the indoor WLAN environment[10].
3.
RADIO – FIBER TECHNOLOGY
A system for distributing RF signals over optical fibre consists of a Central Site (CS) and a
Remote Site (RS) connected by an optical fibre link or network. For WLANs, the CS would be the
head-end while the radio access point would act as the RS. Pioneer Fibre-Radio systems such as the
one depicted in Figure 1 were primarily used to transport microwave signals, and to achieve mobility
functions in the CS. That is, modulated microwave signals had to be available at the input end of the
Fibre-Radio system, which subsequently transported them over a distance to the RS in the form of
optical signals [11].
Figure 1: Fibre-Radio System [11]
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3. International Journal of Electronics and Communication Engineering & Technology (IJECET), ISSN 0976 –
6464(Print), ISSN 0976 – 6472(Online) Volume 4, Issue 5, September – October (2013), © IAEME
By delivering the radio signals directly, the optical fibre link avoids the necessity to generate
high frequency radio carriers at the antenna site. Since antenna sites are usually remote from easy
access, there is a lot to gain from such an arrangement. However, the main advantage of Fibre-Radio
systems is the ability to concentrate most of the expensive, high frequency equipment at a centralized
location, thereby making it possible to use simpler remote sites[12].
4.
SIMULATION ENVIRONMENT
OPNET Modeler v14.0 is used for all network simulations. OPNET Modeler is a powerful
communication system discrete event simulator (DES) developed by OPNET Technologies. OPNET
provides a comprehensive development environment supporting the modeling of communication
networks and distributed systems. Both behaviour and performance of modelled systems can be
analyzed by performing discrete event simulations.
The IEEE 802.11 WLAN architecture is built around a Basic Service Set (BSS) [13,14]. A
BSS is a set of stations that communicate with one another. Figure 2 shows an outline to the model
and is followed by the one wireless LAN sites (Figure 3).
The response times of applications (HTTP, FTP, Email, Database and Video Conferencing)
at the mobile nodes are also analysed to ascertain the user perceived performance of the WLAN. A
simulation time of 5 minutes is set for all scenarios with the Start time Offset for all applications set
to 110 seconds.
Results from the simulated network model will show the effect of replacing copper cables
with fibre-optic cables in the WLAN feeder network infrastructure.
4.1 Radio-Fibre Scenario
The baseline scenario is duplicated and then modified. All Fast Ethernet 100BaseT links are
replaced by optical fibre using Fibre Distributed Data Interface (FDDI) links while the serial T1
WAN links remain unchanged.
Figure 2 shows the modified high-level network environment appropriately named
radio_fibre_802_11_g_wlan_deployment. The modified 802.11g WLAN BSS using fibre links and
devices is shown in Figure 3.
Figure 2: Radio-Fibre WLAN Deployment
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4. International Journal of Electronics and Communication Engineering & Technology (IJECET), ISSN 0976 –
6464(Print), ISSN 0976 – 6472(Online) Volume 4, Issue 5, September – October (2013), © IAEME
Figure 3: Radio-Fibre 802.11g WLAN BSS
4.2 WLAN Application Response Times
The user performance of the WLAN is measured using the response times of the applications
deployed on the WLAN. The measured average response times of the applications namely; HTTP
(Web Browsing), FTP (File Transfer), Email (Electronic Mail) and DB Entry/Query (Database
Access), as observed in the WLAN subnetwork of the baseline model are shown in Figure 4.
FIGURE 4 : Response times of applications in baseline WLAN
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5. International Journal of Electronics and Communication Engineering & Technology (IJECET), ISSN 0976 –
6464(Print), ISSN 0976 – 6472(Online) Volume 4, Issue 5, September – October (2013), © IAEME
Approximate average values of the response times are shown in Table 1 below.
Table 1: Response times of applications in baseline WLAN
Application
Response Time (sec)
HTTP
0.57
FTP
0.023
Email
0.43
Database
0.13
4.3 Radio-Fibre Application response time
The user perceived performance of the WLAN is measured using the response times of the
applications deployed on the WLAN. The measured average response times of the applications
namely; HTTP (Web Browsing), FTP (File Transfer), Email (Electronic Mail) and DB Entry/Query
(Database Access), as observed in the WLAN subnetwork of the baseline model
Here, the analysis effect of the radio-fibre model in the response time of the application shown in fig.
5, the response time of the HTTP application shows that a significant improvement in radio-fibre
model with compare with that found in baseline model.
Fig. 5: Comparing HTTP Page Response Times between baseline and radio-fibre models
In the FTP application, the response time of the fibre model is increased more than the
baseline model that make the file transfer be slower typical TCP protocol behaviour explained earlier
is responsible for this due to increased time overhead in acknowledgements causing increased delays,
as shown in figure 6.
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6. International Journal of Electronics and Communication Engineering & Technology (IJECET), ISSN 0976 –
6464(Print), ISSN 0976 – 6472(Online) Volume 4, Issue 5, September – October (2013), © IAEME
Fig. 6: Comparing FTP Download Response Times between baseline and radio-fibre models
In the EMAIL application, the response time that found in radio-fibre model has shown in
figure 7, and relatively the results give a big difference between them.
In the DB also there are little increased as same as that found in FTP application in the radiofibre model with compare with baseline model as shown in figure 8.
Fig. 7: Comparing (Email Download Response Times) between baseline and radio-fibre models
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7. International Journal of Electronics and Communication Engineering & Technology (IJECET), ISSN 0976 –
6464(Print), ISSN 0976 – 6472(Online) Volume 4, Issue 5, September – October (2013), © IAEME
Fig. 8: Comparing DB Query Response Times between baseline and radio-fibre models
5. CONCLUSION
This chapter presented conclusions drawn from the research results and provided
recommended areas for future work. The aim of this research was to design, implement and compare
the performance of a WLAN subnetwork model fed by a copper wired enterprise network with that
of a fibre-optic based feeder network. The results have shown that this research goal was achieved.
They showed that wireless broadband multimedia communication in a WLAN can be achieved with
a fibre-optic based feeder network.
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AUTHOR’S PROFILE
The Author is an assistant Professor in the Computer Engineering Department at
Institute of Technology, Baghdad, IRAQ. He has been awarded a Doctor of
Philosophy in Laser and Opto-Electronics Engineering from University of
Technology, Baghdad, in 2007. He has studied Master of Science in Electronics
Engineering, Cupper Vapor Laser's Power supply at University of Technology,
Baghdad in 2000. He has gained Bachelor in Electrical and Electronic
Engineering from University of Technology, Baghdad, in 1987. Currently he is
the Deputy Dean of Institute of Technology, Baghdad, IRAQ. His research
interests are Radio over Fiber, Wireless Network, Laser's Power supply and OPNET.
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