Performance comparison of Wireless IEEE 802.11 a, b, g and n used for Ad-Hoc Networks in an ELearning Classrooms Network

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Performance comparison of Wireless IEEE 802.11a,b,
g and n used for Ad-Hoc Networks in an ELearning
Classrooms Network
Fatima LAKRAMI
Department of physics
STIC Laboratory, Chouaib Doukkali
University
El Jadida, Morocco
fatima.lakrami@gmail.com
Najib ELKAMOUN
University
El Jadida, Morocco
Elkamoun@gmail.com
Ouidad LAOUIDYA
University
El Jadida, Morocco
Labouidya.o@ucd.ac.ma
Abstract—This paper presents a comparative study of IEEE
802.11 a/b/g/n wireless LAN standards in an ELearning
classroom network using adhoc networks as communication
support. The evaluation is performed through a series of
scenarios schematizing communication between students and
practitioners in an educational context. The first objective is to
plan the physical layer via the choice of the suitable transmission
standard that satisfy the implementation specifications. Given the
real-time traffic considered, a good traffic transmission must be
ensured.
Keywords- Wirless networks, adhoc network, 802.11, e-learning
I. INTRODUCTION
The use of ad hoc networks in educational institutions is
seen as an innovative, convenient and flexible teaching aid to
both professors and students, since multimedia support (video,
interactive animations) represents the new teaching medium
in learning environments recently adopted by universities.
The fields of application of ad hoc networks are constantly
multiplying, that of education remains a very active one. The
current trend in distant learning is primarily to ensure a certain
comfort and flexibility in teaching procedure, both for
teachers and students. The availability of resources is no
longer an issue, but the way to access to these resources is the
problem beginning to take over.
The main outcome of this project will be the development of
an AD-HOC system that consists of three layers: network
architecture (including transmission), service delivery and
learning environment. The goal is to successfully build the
learning platform on a flexible network architecture, creating
mappings between content and services. Users are placed at
the center of an educational environment, always available,
independent of the peripheral.
Indeed, and rather than adopting traditional concepts and
dealing with the effects of ad hoc mobile networks, the
inherent physical and dynamic characteristics are analyzed.
Following the notion of a spontaneous connection of a
computer terminal, an efficient infrastructure should be
developed. Therefore, a spontaneous exchange of experience
and knowledge should be supported. As start, and as a first
step, we must plan the physical layer, by choosing the best
standard of communication for the given architecture. the
current wireless cards support several standards, that continue
to raise their bit rates, but the physical characteristics
(frequency, modulation ...) remain specific to each standard.
And therefore it will be necessary to reveal the best
transmission characteristics adaptable to an environment such
as the one considered in this project.
the rest of the paper is organized as follow: Section 3 explains
the deployment of ad hoc architecture in universities for
learning purposes. Section 3 reviews different 802.11
standards, with a remainder of their physical and transmission
characteristics. Section 4 presents the contribution proposal.
Section 5 is about simulations and results. Section 6 concludes
the paper.
II. AD HOC NETWORKS
With the prominent development of communication
technologies, the use of information systems has evolved, it is
expressed in particular by a need for user mobility. Wired
networks are not able to ensure such flexibility of use.
Wireless networks, and wifi in particular, have made it
possible to a part of this lack. Users can thus move freely with
their terminal mobile (computer, telephone, PDA ...) while
remaining connected to their personal or corporate network
[2].
The use of mobile terminals requires the use of an
infrastructure (access points) that is sometimes expensive or
difficult to implant. So, this solution is not always feasible. As
a result, mobile networks with no infrastructure have been
International Journal of Computer Science and Information Security (IJCSIS),
Vol. 15, No. 9, September 2017
229 https://sites.google.com/site/ijcsis/
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deployed. These networks are better known as mobile [3] ad
hoc networks or MANETs (Mobile Adhoc NETworks).
An Ad Hoc network is a wireless network capable of self-
organizing without any predefined infrastructure. Such a
network is composed of mobile stations or nodes that can
communicate directly between them, if they are within radio
range. Since the coverage of the stations is relatively limited,
the deployment of a large-scale network requires that the Ad
Hoc network [2] be multi-hop, that is, stations act as a relay
point. Ad Hoc networks, through their self-organization, and
lack of infrastructure, can easily be deployed in many areas :
(integrated recently in the automotive sector to increase the
safety of the users in the information about possible obstacles
on their route), during rescue operations (rescue at sea, in
disaster victims ...) or during military operations. One of the
fields of use of the manets is that of education. Manets can be
used to communicate mobile units dispersed on a university
campus. classrooms for example, students with professors ...
The exchange of a varied traffic is possible, in addition, no
prior planning of the network is indispensable. which will
provide a certain ease of communication, and a great
flexibility of deployment [4].
III. REVIEW OF DIFFERENT 802.11 STANDARDS
Wi-Fi was born in the late 1990s, Wi-Fi covers many
different standards that all have the prefix 802.11. A suffix in
the form of a letter makes it possible to distinguish the norms
between them. For individuals, there are five different
standards: 802.11a / b / g / n / ac. Each represents an evolution
of the previous standard.
A. 802.11 a/b/g
The 802.1 1a / b / g standards are the least problematic since
their operation is simple. The first one operates in the 5 GHz
band, and this is what allows it to have a high bit rate at the
time, at 54 Mbps. However, its range is low since the higher is
the frequency, the smaller the range become. On the other
hand, the advantage of the 5 GHz band is its low congestion (=
less interference), which in fact makes it possible to achieve
higher bit rates and a better stability of the connection. For
information, the 2.4 GHz band is congested since many
devices also use it: microwaves, or Bluetooth devices.
Concerning the norms b and g, they are very close to each
other since the second one is a slight evolution of the first one
which nevertheless allows to increase strongly the flows with
a different functioning: of 11 Mbps, one passes to 54 Mbps,
the same as the version a, with better range. Here is a
summary of the specificities of each standard [5]:
The 802.11a standard: With a maximum speed of 54 Mbit / s
this standard was one of the fastest at the time. This speed is
due to the use of the 5 Ghz band which allows a good transfer
of data. This frequency also limits the range of the signal
which will be 35 m. This frequency is less congested and
allows for a more stable connection and with less interference.
The 802.11b standard: it has the lowest bit rate that is found
with this standard, it is limited to 11 Mbit / s. This limited
bandwidth is due to the use of frequency 2.4 Ghz. The range is
again limited to 35 m.
The 802.11g standard: Dating from 2003, it is the latest of
the 3, it allows to reach a rate of 54 Mbit / s using the
frequency 2.4 Ghz. The designers of this new standard have
succeeded in extending the range of the signal up to 40 m. In
2003 it is the best existing Wifi standard at the same time
stable, fast and with the best range of the signal ever observed.
B. 802.11n
The standard n introduced two important elements to be taken
into account for the calculation of the maximum theoretical
throughput: the MIMO and the channel width. MIMO is the
acronym for Multiple Input Multiple Output. As the name
suggests, it allows a device to have multiple antennas to send
and receive information. Basic, a device has a single antenna
(one speaks of stream or spatial channel) to download the
information (download) and to send them (upload). With the
MIMO 2 × 2, a device has two antennas. Up to 3 × 3 (3
receiving and 3 transmitting antennas) or more exotic
configurations such as 3 × 2 (3 for reception and 2 for
broadcast) can be installed. Switching to 2 antennas (MIMO 2
× 2) doubles the flow compared to a single antenna.
The following table resumes the characteristics of transmission
of different cited standards:
TABLE I. COMPARATIVE TABLE OF 802.11 STANDARDS
802.11
Frequency
Band
Throughtput Range Congestion Bandwidth MIMO
A 5 GHz 54 Mbps Weak weak 20 MHz No
B 2,4 GHz 11 Mbps Correcte High 20 MHz No
G 2,4 GHz 54 Mbps Correcte High 20 MHz No
N 2,4 GHz from 72 to
288 Mbps
good High 20 MHz No
N 5 GHz from 72 to
600 Mbps
good Weak 20 / 40
MHz
Yes
The recent Wireless cards are designed as dual. They are
engineered to be faster, stronger than previous generation.
Actually, it is the standard 802.11ac that is the most
implemented on wireless cards, it delivers up to 3x faster Wi-
Fi speeds (up to 433 Mbps) than 802.11n, with up to 3x more
bandwidth per stream for more users and devices. It’s
specification features implemented that improve channel
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reliability resulting in better coverage and performance. In
plus it Supports seamless roaming between respective access
points (802 .11b, 802.11g, 802.11a/b/g, 802.11a/b/g/n , and
802.11ac) [6].
IV. CONTIBUTION
The present work, is part of a project of an implementation of
an learning platform at the basis of ad hoc networks [1]. The
omnipresence of information and the instantaneousness of the
network remain the main objectives of such experiment. The
whole campus must be able to communicate and exchange
various types of traffic, of which the category and the priority
may vary. Teachers can give courses or conferences in real
time to students who are delocalized. The first step is to study
the different wireless communication standards in order to
detect which one offers the best performances in terms of
coverage, quality of service and other.
V. SIMULATION AND RESULTS
We use OPNET network simulator 17.5 [7] for the different
simulations. we simulated a network composed of 30 nodes
spread over 3 classrooms, a streaming server is located in one
of these three classes. different nodes communicate via an ad
hoc network. The routing is provided by the AODV protocol. 3
other nodes are located in the corridor leading to the two
classes. the different nodes are attending a video course loaded
at the local server, which in this case represents the teacher's
computer. we have modeled a simple case starting from 1, 5 up
to 10 clients. the goal is to identify the limits of the different
standards simulated here, which are 802.11a / b.g / n. The case
of mobility has been also treated, the last scenario schematizes
the same network but by considering that 5 nodes are moving
in the hall between the two classrooms with a walk average
speed of 3m/sec. performance metrics are presented by: packet
delay variation, End To End Delay, % of loss rate, and medium
access delay.
In this work we focus on studying 802.11a/b/g/n, we presume
that not all communicating mobiles has new wireless cards.
Here is a summary of different 802.11 simulation parameters:
802.11b direct sequence 11mbps
802.11a (OFDM) 54Mbps
802.11g 54 Mbps
802.11 n (5Ghz) up to 65 Mbps
Figure 1 schema of the network topology
A. 1Client/traffic light
In this first scenario, one station is communicating with the
server, all stations are fixed.
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Figure 2 performance results for 1 clients
For the case of 1 client connected to the server, results are very
satisfying for almost all 802.11 standards. 802.11b represent
the higher delay. Due to the limited bite rate which is 11 Mbps.
The lowest delay and delay variation values are observed for
802.11n. while 802.11 a and 802.11g give roughly the same
results.
B. 5 Clients / Light traffic
In the second scenario, we increase the number of clients to 5.
All nodes are still fixed.
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When we increase the number of clients, we can observe that
802.11b suffers a huge performance degradation, the delay
remains acceptable for the others standards. For the loss rate,
the lowest value is obtained for 802.11a, with a minimal
difference with 802.11g and 802.11n. always for delay, it is the
801.11n that gave best performances.
C. 10 clients /Light traffic
For this scenario, 10 clients are now communicating with the
server.
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for 10 clients, we can notice that 802.11b has reached its limits.
802.11n give the best values for all the considered metrics,
which is completely reasonable, due to the huge improvements
that has undergone the 802.11n standard, more details are given
in paragraph 3.
D. 10 clients With mobility
We consider for this scenario that 5 clients are moving from
one classroom to another.
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Figure 4 performance results for 10 clients with mobility
Even when considering 50% of nodes in movement, the
802.11n still perform better. The packet loss rate and delay are
very low in comparison with all other obtained values.
VI. CONCLUSION AND PERSPECTIVES
In this paper, an experiment comparison between different
802.11 standards is given. the presented study is part of a
project that aim to implement ad hoc network as a learning
infrastructure. Students, researchers and professors, can
henceforth communicate through a unified platform, broadcast
their courses and establish an audio/video conference session
with each other. the achievement of such project has to begin
by planning the physical layer, here it is about a wireless
network, so a wireless standard has to be chosen. Therefore, a
comparative study through simulation is performed here. We
aim to reveal limits of different standards in such deployment.
We demonstrate that standard 802.11n and 802.11g give better
results compared with the others, even with the presence of
mobility, and the increase of the number of clients. the
standard 802.11 b is not suitable at all.
REFERENCES
[1] F. Lakrami, N. Elkamoun, and M. El Kamili. "An enforced QoS shceme
for high mobile adhoc networks." In Wireless Networks and Mobile
Communications (WINCOM), 2015 International Conference on, pp. 1-
8. IEEE, 2015.
[2] Frodigh M, Johansson P, Larsson P. Wireless ad hoc networking: the art
of networking without a network. Ericsson review. 2000 Jan;4(4):249.
[3] F. Lakrami, N. Elkamoun “Mobility support in OLSR routing protocol”.
In Network computing and information security. 2012 Jan 1;345:804-12.
[4] D. Halperin, B. Greenstein, A. Sheth, D. Wetherall “Demystifying
802.11 n power consumption”. InProceedings of the 2010 international
conference on Power aware computing and systems 2010 Oct 3 (p. 1).
[5] M. Lauer, M. Matthes, M. Elan: “ An e-learning infrastructure for ad-
hoc networks” . InProceedings of the eighth ACM International
Conference on Mobile Computing and Networking 2002 Sep (Vol. 7,
No. 1, pp. 53-55).
[6] Skafidas, Efstratios, et al. "Method and apparatus for coverage and
throughput enhancement in a wireless communication system." U.S.
Patent No. 7,136,655. 14 Nov. 2006.
[7] Modeler, O. P. N. E. T. "Riverbed Technology." Inc. http://www.
riverbed. com (2016).
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