SAMPLE TOOLS FOR TEACHING SUBMISSION
A Web-based Tool to Enhance
Learning and Teaching Wireless LAN
Design
Nurul I. Sarkar, MIEEE
Auckland University of Technology
Overview
Wireless communication and networking courses are becoming increasingly
popular in universities, polytechnics, post secondary colleges and private training
institutions around the globe. This is partly because of rapid developments in wireless
communication network technology and the high demand for wireless networking skills
in the industry, both nationally and internationally. Unfortunately, it has often proven
difficult to motivate students to learn about wireless local area network (WLAN) design
because they find the subject dry and theoretical. A web-based software tool (named
WLAN-Designer) has been developed at the Auckland University of Technology (AUT)
that gives students an interactive, hands-on learning experience in WLAN design. The
WLAN-Designer is suitable for classroom use in introductory level courses in wireless
networking. The effectiveness of the WLAN-Designer has been evaluated both formally
by students (student evaluation forms) and informally – through discussion within the
teaching team. This chapter describes the WLAN-Designer and its effectiveness as an aid
to learning and teaching about WLAN design. The conclusions drawn are based on
survey data collected from students. The feedback from students indicates that the
development and implementation of the WLAN-Designer were successful. The chapter
concludes by discussing the strengths and weaknesses of the WLAN-Designer and its
future development. The impact of the WLAN-Designer on students’ performance is also
discussed.
Background and Motivation
Wireless local area networks (WLANs) are often included as a topic in computer
science, information technology, engineering, and business courses as WLANs are a
fundamental component of computer networks today. It is believed that incorporating
practical demonstrations into these courses, thereby illustrating theoretical concepts and
providing opportunity for hands-on flexible learning experiences, significantly enhances
student learning about WLAN design. Yet very little material designed to supplement the
teaching of WLAN design is publicly available, as a search of the Computer Science
Teaching Center (Grissom, Knox, Fox, & Heller) and SIGCSE Education Links
(Anonymous) sites reveals. Even less material is available for wireless networking
courses and related topics.
We strongly believe, as do many others (Chandra, 2003; Engst & Glenn, 2003;
Rappaport, 2002), that students learn more effectively from courses that provide for
active involvement in hands-on learning activities. B.F Skinner, a famous behavioral
psychologist is also supports experiential learning (Skinner, 1964).
Traditionally, wireless networking is one of the most difficult subjects to learn
and teach in a meaningful way because students find the subject dry and theoretical.
Researchers at AUT have developed a web-based tool called WLAN-Designer (wireless
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LAN designer) that gives students an interactive, hands-on experience in wireless LAN
design. With WLAN-Designer a teacher is able to use it in the classroom, as a
demonstration, to enhance the traditional lecture environment at an introductory level,
and students can use it tutorials on wireless networking, and to verify (interactively and
visually) the results of in-class tasks and exercises on WLAN design. The WLANDesigner reported here can be accessed at any time either via an intranet or through the
public Internet.
Wireless networking concepts are described in many references e.g. (Bing, 2002;
Ciampa, 2001; Doran, 2002; Palmer & Sinclair, 2003), and web-based tools are discussed
extensively in the literature e.g. (Kofke & Mihalick, 2002; Rokou, Rokos, & Rokou,
2003; Sitthiworachart & Joy, 2003). A number of open source and commercial network
simulators exist for building a variety of wireless LAN models (Chang, 1999; Sanchez &
Manzoni, 2001; Zheng & Ni, 2003). However, these powerful tools can have a steep
learning curve, and while excellent for doing in-depth performance evaluation of wireless
LANs, they often simulate a wireless networking environment in far more detail than is
necessary for a simple introduction of fundamental concepts. Network simulator 2 (NS-2)
(Fall & Varadhan, 2003) is another powerful simulation software package suitable for
performance analysis of wireless networks. However, it is of limited use as a learning and
teaching tool because of its text-based interface that is not user-friendly.
Description of the System
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The system described here is easy to use and reliable, and can be used to enhance
the learning and teaching of various aspects of wireless LAN design. The diagram in
Figure 1 outlines the structure of the system.
Figure 1. Diagram of the Structure of the WLAN-Designer.
The WLAN-Designer reported here has the following main features:
 Home: The home page contains project title, author’s name, and links to various pages
of the WLAN-Designer including design, standards, technology, protocols, topology,
and feedback. The user can easily navigate the web pages using the point-and-click
graphical user-interface (see Fig. 2).
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Figure 2. A screenshot of the ‘design page’ of the WLAN-Designer.
 WLAN information: The web pages listed below provide some general and technical
information about wireless LANs:
o Overview: This page provides an introduction to wireless LAN design.
o Network standard: This page highlights the most common wireless LAN standards
such as IEEE 802.11b/a/g.
o Technology: Wireless networking technologies including frequency hopping spread
spectrum (FHSS), direct sequence spread spectrum (DSSS), and orthogonal
frequency division multiplexing (OFDM) are discussed.
o Protocol: This is an important matter that needs to be considered when designing
wireless LANs. The channel access protocol efficiently controls the transmission
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when multiple users share a common channel. This page provides an overview of
channel access protocols for wireless LANs, including the Carrier Sense Multiple
Access with Collision Avoidance (CSMA/CA) protocol.
o Topology: A topology represents the physical layout (i.e. architecture) of the
network. It is another of the important considerations in LAN design. This page
describes a variety of topology configurations for wired backbone networks,
including physical bus and star topologies.
o Components: The components of wireless LANs, such as wireless network
interface cards and wireless access points, are discussed.
 Design: This page allows users to create a variety of models for wireless LANs. It has
a number of drop-down menus in which a user can easily select the WLAN
architecture (e.g. ad-hoc networks), the number of mobile stations, and the wired
backbone topology (e.g. Bus) for the proposed wireless LAN design. Based on the
user’s selection, the system displays the proposed network diagram on the screen. Fig.
2 shows a screenshot of the WLAN-Designer ‘design page’.
 Feedback: In an endeavour to improve the WLAN-Designer we have provided
contact details to enable users to provide feedback.
Additional information about wireless LAN design and modeling is presented in
the bottom part of relevant pages. The usefulness and educational benefits of WLANDesigner are discussed in the next section.
Usefulness and Benefits of the WLAN-Designer
The WLAN-Designer has been designed with a graphical user interface (GUI)
which is easy to use and self-explanatory (Shneiderman, 1998). The point-and-click GUI
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makes the WLAN-Designer well suited both to students and to teachers. Therefore, the
WLAN-Designer can be an integral part of a two-hour session, enhancing the teaching
and learning of various aspects of wireless LAN design. In the classroom, an in-class
task will be given to the students to design both ad hoc and infrastructure networks on
paper. After a prescribed period of time (for example, 15 minutes), the WLAN-Designer
will be introduced to the students on a step-by-step basis to enable them to verify their
solutions and to learn more about WLAN design. By working through a tutorial using the
WLAN-Designer, students are able to gain hands-on learning experience about wireless
LAN design.
The WLAN-Designer can be accessed at any time either via an intranet or through
the public Internet. Therefore, students can work on their homework exercises in their
own time and at their own convenience. In addition to enhancing face-to-face teaching
with by including an element of online learning in the classroom, the WLAN-Designer
provides online support for off-campus students and enhances learning in by providing a
flexible mode for the delivery of papers.
The main benefits of the WLAN-Designer described in this paper are as follows:

Global access: It can be accessed at any time through the public Internet.

Hands-on: It facilitates an interactive, hands-on introduction to both ad hoc and
infrastructure wireless LAN design.

Modeling: It provides a simple and easy way to develop a variety of wireless LAN
models. Using the ‘design’ page of the WLAN-Designer, students can experiment
with a variety of LAN topologies and hence enhance their knowledge and
understanding of WLAN design.
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
Easy to use: The GUI makes the WLAN-Designer an easy to use and user-friendly
tool.

Challenging: It provides an environment for students to test their knowledge about
wireless LAN design.
Test Results
To evaluate its performance and robustness, the WLAN-Designer has been
installed on a web server. The screenshots of WLAN-Designer test results for
infrastructure and ad hoc networks are shown in Figs. 3 and 4, respectively.
BSS1
BSS2
ESS
Figure 3. Infrastructure-based wireless LANs with 6 mobile stations and two
wireless access points.
To test the WLAN-Designer for use with infrastructure-based wireless LANs, the
following components were selected from the drop down menus of the ‘design page’. The
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WLAN-Designer then produced the valid LAN diagram seen in Figure 3: {Standard:
IEEE 802.11b, Wired backbone topology: Bus, Number of mobile stations: 6}. In the
case of ad hoc wireless LANs, 6 mobile stations were chosen, and the WLAN-Designer
had produced the valid wireless LAN model seen in Figure 4.
Figure 4. An ad hoc wireless LAN with 6 mobile stations.
As can be seen in Fig. 3, there are two wireless access points, which form two
infrastructure-based wireless LANs. Three mobile stations, which are within the same
radio coverage area, communicate with the associated access point (AP) forming a basic
service set (BSS). There are two BSSs namely, BSS1 and BSS2, which are connected via
a wired backbone network (see Fig. 3). In a large scale campus-wide WLAN, a wired
backbone network would connect several BSSs via APs to form a single network and
thereby extend the wireless coverage area. Such a single network is called an extended
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service set (ESS) and has its own identifier, the ESSID, which is the ‘name’ of that
network and is used to distinguish it from different networks.
The complexity of each node in ad hoc networks is higher than that in wireless
infrastructure networks because every node has to implement medium access
mechanisms, and message forwarding and routing functions. However, each mobile
station can communicate directly with other stations, so no AP to control medium access
is necessary (see Fig. 4).
Evaluation and Interpretation
The WLAN-Designer has been evaluated extensively, both formally by students
(student evaluation forms) and informally – through discussion within the teaching team,
in order to assess its educational value. As part of the formal evaluation process, students
were asked to complete a questionnaire. They were asked the following six questions:
(i)
User interface: How convenient did you find the ‘user interface’ of the WLANDesigner to use?
(ii)
WLAN design information: How useful did you find the information about
wireless LANs design to be?
(iii) Easy to use: How easy (overall) did you find the WLAN-Designer to use and
follow?
(iv) Navigation: How easy did you find navigating through the WLAN-Designer web
pages?
(v)
Measure of success: How effective was the WLAN-Designer in helping you to
improve your understanding of WLAN design concepts?
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(vi) Hands-on: Would you like to have more tools of this kind as part of your course?
A Likert scale with 5 points (1-5) was used in the questionnaire. For questions
(i) – (v): 1= poor; 5 =excellent; for question (vi): 1=No, 5=Yes.
40 undergraduate students from both “E-business IT Infrastructure” and
“Networking & Telecommunications” courses completed the questionnaire and their
responses are plotted in Fig. 5. The responses were interpreted as follows:
(i)
The GUI of the WLAN-Designer is found to be easy to use. About 75% of the
students indicated that they were quite satisfied with the WLAN-Designer interface
whereas the rest (25%) were neutral (see Fig. 5(i)).
(ii)
About 75% of the students indicated that the WLAN design information presented
in the web pages is very useful. About 2.5% of the students expressed some concern,
and the rest (22.5%) were neutral (see Fig. 5(ii)).
(iii) The WLAN-Designer was found to be a user-friendly tool. About 77.5% of the
students were happy with the current version of the WLAN-Designer. However,
2.5% of the students indicated that they were not totally satisfied with the current
version of the WLAN-Designer, and the rest (20%) were neutral (see Fig. 5(iii)).
(iv) About 77.5% of the students indicated that they found that the WLAN-Designer is
very robust and that it is easy to navigate through the web pages, whereas the rest
(22.5%) were neutral (see Fig. 5(iv)).
(v)
About 82.5% of the students indicated that the WLAN-Designer had clearly
assisted them in developing a better understanding of the concepts of wireless LAN
design. However, about 2.5% of the students expressed some concern, and the rest
(15%) were neutral (see Fig. 5(v)).
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(vi) About 77.5% of the students indicated that they would like to have more hands-on
activities in the course. About 2.5% of the students were not very interested in trying
more hands-on activities, and the rest (20%) were neutral (see Fig. 5(vi)).
User interface
WLAN design information
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# of responses
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Easy to use
Navigation
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Measure of success
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(vi)
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Figure 5. Student response. Graphs illustrating the number of respondents in each
category for each of the six questions in the questionnaire.
We observed that by participating in the hands-on activities in the classroom,
students became increasingly motivated to learn more about wireless LAN design and
enjoyed this course more than previous courses that consisted of lectures only. We are
seeking feedback regularly both from students and staff for further improvement of the
WLAN-Designer.
Impact of WLAN-Designer on students’ performance
We have trialed run the WLAN-Designer in our two undergraduate courses
namely, “E-business IT Infrastructure (EBITI)” and “Networking & Telecommunications
(N & T)” in semester 2, 2003. Both EBITI (Petrova, 2000) and N&T (Sarkar & Petrova,
2001) courses are at level 6 or first year degree level; and constitute 15 credit points (150
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hours of student learning) at AUT. Most of the EBITI students are studying towards their
Bachelor of Business (BBus) qualification and have a very limited background in IT and
CIS fields. On the other hand, the N&T students are studying towards Bachelor of
Information Technology and have a good background in IT and CIS fields.
The WLAN-Designer has had quite a positive impact on students’ learning about
wireless LAN design. As can be seen in Table 1, the overall student pass rate in semester
2, 2003 is slightly higher compared to students in semester 2, 2002. It is considered that
much of this difference can be accounted for by the fact that the students in semester 2
2003 used the WLAN-Designer whereas the students in semester 2, 2002 did not get an
opportunity to use the WLAN-Designer at all. We also observed that EBITI students
benefited even more from WLAN-Designer (5% pass rate improvement) than the N&T
students (3% improvement) did. This is probably due to EBITI students’ limited
background in the IT and CIS fields compared to N&T students.
Table 1. Comparison of student performance with and without WLAN-Designer
Student pass rate (%)
Semester
Year of study
With WLAN-Designer
2
Without WLAN-Designer
2
EBITI course
N&T course
2003
100
95
2002
95
92
5
3
Pass rate improvement (with WLAN-Designer)
Conclusion
A web-based software tool (WLAN-Designer) has been developed that can be
used either in the classroom or at home (i.e. off campus) to enhance the learning and
teaching of various aspects of wireless LAN design. The WLAN-Designer is an easy to
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use and user-friendly software tool, which can be accessed from the Internet. It was
evaluated by students and their responses to the questionnaire about the WLAN-Designer
were mostly favourable. The students indicated that they had found the WLAN-Designer
easy to use, robust and that it helped them to gain an understanding of wireless LAN
design concepts. The WLAN-Designer has had a positive impact on students’
performance. Results show that both EBITI and N&T students scored better in the final
examination with WLAN-Designer experience than the students without WLAN-designer
experience.
Currently, the WLAN-Designer displays wireless LAN diagrams involving up to
6 mobile stations, which is adequate for demonstration purposes. The software can easily
be upgraded to accommodate any number of mobile stations. The incorporation of
wireless personal area networks (Bluetooth technology) is also suggested for future work.
The WLAN-Designer is freely available to faculty interested in using it to supplement
teaching courses involving wireless LAN design. The WLAN-Designer (prototype) can
be accessed from our home page at http://elena.aut.ac.nz/homepages/staff/Nurulsarkar/software/WlanDesigner/. More information about the WLAN-Designer can be
obtained by contacting the author.
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2004, from http://sigcse.org/topics/
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Wiley & Sons, Inc.
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Ubiquitous Computing. Paper presented at the Proceedings of the 34th Technical
Symposium on Computer Science Education (SIGCSE'03), Reno, Nevada, USA.
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Ciampa, M. (2001). Guide to Designing and Implementing Wireless LANs: Course
Technology.
Doran, A. (2002). The Essential Guide to Wireless Communications Applications (2nd
ed.): Prentice-Hall International, Inc.
Engst, A., & Glenn, F. (2003). Wireless Networking Starter Kit - The practical guide to
Wi-Fi networks for windows and Macintosh: Adam Engst and Glenn Fleishman.
Fall,
K., & Varadhan, K. (2003). The ns Manual. The VINT
http://www.isi.edu/nsnam/ns/, from http://www.isi.edu/nsnam/ns/
project.
Grissom, S., Knox, D., Fox, E., & Heller, R.Computer Science Teaching Center (CSTC).
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Wide Area Networks (2nd ed.): Course Technology.
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Computing & Information Technology, 4(1), 70-77.
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Terms and Definitions
Ad hoc: A class of wireless networking architecture in which there is no fixed
infrastructure or wireless access points. In ad hoc networks, each mobile station acts as
router to communicate with other stations. Such a network can exist on a temporary basis
to share some resources among the mobile stations.
AP: AP stands for Access Point. Typically, infrastructure-based wireless
networks provide access to the wired backbone network via an AP. The AP may act as a
repeater, bridge, router, or even as gateway to regenerate, forward, filter, or translate
messages. All communication between mobile devices has to take place via the AP.
GUI: GUI stands for Graphical User Interface. Most of the modern operating
systems provide a GUI, which enables a user to use a pointing device, such as a computer
mouse, to provide the computer with information about the user’s intentions.
IEEE 802.11b/a/g:
Generally refers to wireless LAN standards. The IEEE
802.11b is the wireless LAN standard with a maximum bandwidth of 11 Mbps operating
at 2.4GHz. The IEEE 802.11a is the high-speed wireless LAN with a maximum
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bandwidth of 54 Mbps operating at 5 GHz. The IEEE 802.11g is backward compatible
with the IEEE 802.11b, with a maximum bandwidth of 54 Mbps operating at 2.4GHz.
Infrastructure: A class of wireless networking architecture in which mobile
stations communicate with each other via access points, which are usually linked to a
wired backbone. Such a network has fixed infrastructure and has a centralized control.
Intranet: An Intranet can be thought of as the Internet restricted to the confines
of an organization, in order that both employer and employees be able to share
information within that organization. An Intranet is based on a local area network.
LAN: LAN stands for Local Area Network. A class of computer network in
which the coverage area is usually limited to a room, building or a campus.
Software tool: This term generally refers to a computer program or software
package.
Wireless LAN: This term refers to a local area network (LAN), which uses either
Infrared or Radio frequencies rather than physical cable as the transmission medium.
WLAN-Designer:
A web-based software tool developed at the Auckland
University of Technology, to enhance the learning and teaching of various aspects of
wireless LAN design.
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