346 IEEE TRANSACTIONS ON EDUCATION, VOL. 56, NO. 3, AUGUST 2013
A Web-Based Educational Interface for an AnalogCommunication Course Based on MATLAB
Builder NE With WebFiguresSezgin Kaçar and Cüneyt Bayılmış
Abstract—Experimental experience has a significant effecton students’ engineering education and improves their prac-tical skills. However, experiments are high-cost, requiringlaboratory space, experimental sets, and so on. Computer-as-sisted learning (CAL) can provide a similar educational effect.Web-based interfaces, a type of CAL often used in distance educa-tion, are therefore economical solutions in that they require neitherlaboratories nor experimental equipment. In particular, they fa-cilitate students’ understanding of the practical applications oftheir engineering education. This paper proposes the Web-basedsimulation of analog modulation techniques using MATLAB. Tothis end, a Web-based educational interface, called AnalogWeb,was designed and implemented as part of an analog communica-tion course. AnalogWeb was developed using MATLAB Builderfor NE with WebFigures and ASP.NET platform; it can be easilyaccessed by users/students using only a Web browser and re-quires no installation of MATLAB or any special program on theserver or the clients. AnalogWeb is a user-friendly educationalinterface providing advanced visualization tools such as zoom,moving graphics, and three-dimensional imaging. AnalogWeb wasvalidated, and its educational contributions tested, with 60 under-graduate students at Sakarya University, Turkey; the results arepresented here.
Index Terms—Analog communication, communication engi-neering education, computer-assisted learning (CAL), distancelearning, MATLAB Builder for NE and WebFigures, Web-basededucational interface.
I. INTRODUCTION
E NGINEERING education uses practical applications andlaboratory experiments in its principal aim of improving
the skills of engineering students. These applications and ex-periments provide students with experience in solving practicalproblems. To perform practical applications, a real laboratoryenvironment and instrumentation are required, which have thedisadvantage of being expensive and needing curriculum timeand facility space. Some of the many academic and commer-cial experimental/training setups and equipment are shown inTable I [1]–[5]. These can cost up to several thousand dollars,
Manuscript received April 27, 2012; revised August 08, 2012; acceptedNovember 30, 2012. Date of publication January 08, 2013; date of currentversion July 31, 2013.S. Kaçar is with the Department of Electrical—Electronic Engineering,
Technology Faculty, Sakarya University, Sakarya 54187, Turkey (e-mail:[email protected]).C. Bayılmış is with the Department of Computer Engineering, Tech-
nology Faculty, Sakarya University, Sakarya 54187, Turkey (e-mail:[email protected]).Color versions of one or more of the figures in this paper are available online
at http://ieeexplore.ieee.org.Digital Object Identifier 10.1109/TE.2012.2236329
TABLE ICOMPARISON OF ANALOG COMMUNICATION EXPERIMENTAL SETUPS
so equipping a laboratory for 20 students, say, becomes exces-sively expensive. This presents a major problem in schools andin countries that have limited budgets.Computer-assisted learning (CAL) is an extremely easy, fast,
effective, and economic solution to these disadvantages. CALsignificantly increases the efficiency of traditional/theoreticalengineering education and also reinforces the practical trainingof engineering students when there are many students in a classor when many experiments are to be implemented. Linn’s studyin the communication field and Bhunia’s study in the signalprocessing field can be given as examples of the CAL litera-ture [6], [7]. This paper deals with Web-based interfaces, cur-rently a very popular type of CAL. Web-based educational en-vironments are more useful than other types of CAL. In partic-ular,Web-based solutions enable e-learning, distance education,cost reduction, time saving, flexibility, and advanced visualiza-tion tools. Recently, Web-based educational environments con-sisting of educational interfaces to virtual and remote laborato-ries have been widely used in engineering education. Users/stu-dents can easily access and use interactive Web-based educa-tional tools and environments for practical teaching, with nolimitations imposed by schedule or geographic location [8], [9].The literature describes many Web-based educational appli-
cations with Web-based educational interfaces and virtual andremote laboratories for engineering education using variousplatforms such as MATLAB, Java, C, C++, and LabVIEW.Most of these studies are related to virtual and remote labora-tories for control systems applications such as motor control orrobots. A Web-based laboratory focusing on signal processingand control algorithms for engineering education is introducedin [9]. Current trends in virtual laboratories are discussedin [10]. Tzafestas et al. [11] presented an experimental evalu-ation comparing virtual and remote laboratories in the area ofrobotics. A MATLAB Builder NE implementation of a virtual
KAÇAR AND BAYILMIŞ: WEB-BASED EDUCATIONAL INTERFACE FOR ANALOG COMMUNICATION COURSE 347
remote electrical engineering laboratory is presented in [12]. Aneducational computer system and its Web-based simulator weredeveloped to teach a computer architecture and organizationcourse in [13]. Nowadays, Web-based educational interfacesdepending on MATLAB server technology are widely used inmedicine and biomedical engineering education, [14], [15].Furthermore, a Web-based interface using MATLAB BuilderNE with WebFigures was designed by Bayilmis for teachingand analyzing digital modulation techniques, including ASK,PSK, and FSK, in a communications course [8].This paper describes a Web-based educational interface
AnalogWeb, designed and implemented for teaching andtraining in an analog communications course. AnalogWebwas developed using MATLAB Builder for NE with Web-Figures and the ASP.NET platform. MATLAB Builder forNE [16], which replaces the MATLAB Web server with theMATLAB 2008 version, is becoming an increasingly populartool for engineering applications [17], [18] and educationalplatforms [8], [12], [13]. It enables supporting server tech-nology and powerful features of MATLAB such as its library,analysis tools, numeric computation, advanced visualizationtools and so on.AnalogWeb has several important advantages compared
to those used in the studies mentioned above. One is thatAnalogWeb runs standard services without requiring the down-loading and installation of any extra software, giving fasterrunning time and lower response time and workload. Anotheris its easy access via a Web browser from a PC, laptop, PDA, ormobile/smart phone or other device connected to the internet.A third advantage is the use of MATLAB Builder for NEwith WebFigures and .Net platform in its design; this allowsMATLAB features to be used in simulations without MATLABneeding to be installed on the server or the user computers. Inparticular, MATLAB Builder for NE with WebFigures tech-nology provides high flexibility with advanced visualizationtools such as zoom, moving graphics, and three-dimensionalimages. AnalogWeb has been validated, and its educationalcontributions tested with 60 senior undergraduate students atSakarya University, Sakarya, Turkey; the results of the test arepresented here.The rest of this paper is organized as follows. The theoret-
ical background of AnalogWeb is briefly explained in Section II.Section III introduces the proposed system architecture and thedesign stages of AnalogWeb. Section IV presents the developedAnalogWeb and gives examples of its use. The evaluation ofAnalogWeb’s educational results are described in Section V. Fi-nally, conclusions are drawn in Section VI.
II. THEORETICAL BACKGROUND OF ANALOGWEB
This section is intended to provide the theoretical backgroundused in the interface, not to explain analog modulation tech-niques. In this context, in Section II-A, the analog modulationtechniques used in the interface are classified, with a brief de-scription of their theoretical basis. Section II-B then presents thetheoretical infrastructure of discrete-time simulation of analogmodulation techniques.
A. Analog Modulation Techniques
The two types of analog modulation techniques are ampli-tude modulation and angle modulation. Both use two signals for
Fig. 1. Amplitude and angle modulations.
modulation: the message signal and the carrier signal. In ampli-tude modulation, the amplitude of the carrier signal changes ac-cording to the message signal amplitude. In angle modulation,the frequency of the carrier signal varies according to the mes-sage signal amplitude. Fig. 1 shows both amplitude and anglemodulations.Amplitude modulation can be further diversified as
double sideband (DSB), double sideband–suppressed car-rier (DSB-SC), single sideband (SSB), and vestigial side-band (VSB). The mathematical formulas and general frequencyspectra for amplitude modulation techniques are given inTable II [19], [20].Similarly, there are two types of angle modulation techniques:
frequency modulation (FM) and phase modulation (PM). Thesemodulation techniques are mathematical operations, effectivein the frequency domain since the components of the mod-ulated signal can be clearly seen in the frequency spectrum.Table III shows the formulas and frequency spectra for FM andPM [19], [20].
B. Theoretical Background of Discrete-Time Simulation ofAnalog Modulation Techniques
Two types of graphical results are obtained from AnalogWebsimulations. The first consists of a plot of the message, carrierand modulated signals in the time-domain. The second showsthe frequency spectra of the signals. Since the signals andmodu-lation techniques in this work are analog, the graphics should beobtained by continuous-time operations and transforms. How-ever, since AnalogWeb is a simulation tool designed to simulateanalog modulation techniques, running on a computer as a dig-ital system, the simulation results have to be obtained by dis-crete-time operations and transforms after the signal sampling.It is thus necessary to discuss how analog signals are sampledand simulated in AnalogWeb.If an analog signal is to be simulated with a digital system
such as a computer, it must be sampled, and a discrete-time se-quence must be created from the sampled signal. The samplingrate (or frequency, ) must be more than twice the frequency(in hertz) of the maximum frequency component of thesignal according to the Nyquist sampling ratein sampling theory [21]. In AnalogWeb, for every process, the
348 IEEE TRANSACTIONS ON EDUCATION, VOL. 56, NO. 3, AUGUST 2013
TABLE IIMATHEMATICAL FORMULAS AND FREQUENCY SPECTRA OF AMPLITUDE MODULATION TECHNIQUES, WHERE IS THE AMPLITUDE OF THE CARRIER SIGNAL,
IS THE FREQUENCY OF THE CARRIER SIGNAL, IS THE MESSAGE SIGNAL, IS HILBERT TRANSFORM OF THE MESSAGE SIGNAL,AND IS THE BANDPASS FILTERED SIGNAL OF THE MESSAGE SIGNAL
maximum frequency signal is the carrier signal. For that reason,for time-domain graphics, the sampling frequency is determinedover the carrier frequency . Although makingis adequate for an accurate sampling, is made greater than
to achieve better graphics in time-domain presentations inAnalogWeb.If the sampling has been correctly done, making the time-do-
main presentation of the sampled signals is a very easy opera-tion. The graphics can be created by plotting the time sequencesand discrete signal samples together; there are few differencesbetween the continuous-time and discrete-time presentations.
However, the same cannot be said for the frequency-domainpresentations of continuous-time and discrete-time signals be-cause the discrete-time Fourier transform (DFT) is used for fre-quency-domain presentation of discrete-time signals, while thecontinuous-time Fourier transform (FT) is used for frequency-domain presentation of continuous-time signals. FT and DFTare different transforms with different features. However, ingeneral, the fast Fourier transform (FFT), a more efficient al-gorithm for DFT, is preferred for practical applications; it hasbeen used in AnalogWeb for the frequency-domain presenta-tion of discrete-time signals.
KAÇAR AND BAYILMIŞ: WEB-BASED EDUCATIONAL INTERFACE FOR ANALOG COMMUNICATION COURSE 349
TABLE IIIMATHEMATICAL FORMULAS AND FREQUENCY SPECTRA FOR ANGLE MODULATION TECHNIQUES, WHERE REPRESENT AMPLITUDES
OF BESSEL FUNCTION
Although the most accurate results for continuous-timeanalog signals are obtained in the frequency-domain by usingFT, the frequency spectra in AnalogWeb have to be obtainedwith FFT because of the discrete-time signals. There are differ-ences between the results of the FT of the analog signals and theFFT of the simulated signals since FFT is discrete and of finitelength in both the time and frequency domains [21]. In addition,using the FFT raises issues such as synchronization, frequencyresolution , and spectral leakage. If the sample rate andnumber of samples used in FFT are not selected properly, goodsynchronization and frequency resolution cannot be obtained.This produces spectral leakage, and the results of the FFTare inaccurate, as seen in the right-hand side of Fig. 2, whichshows the FFT of . It is possible to get the sameresults with the FT, when the FFT is used as seen in Fig. 2,if synchronization is provided and the frequency resolution isselected properly.Synchronization is ensured by beginning and ending the
sampled signal at the same phase and choosing the appropriatenumber of samples according to the phase. However, this
is not always possible since the number of samples beinganalyzed must be a power of 2 for the FFT [22]. This posesa big problem for FFT applications; some techniques, such aswindowing, attempt to circumvent this, but cannot eliminatethe synchronization problem entirely.The frequency resolution can be improved to minimize spec-
tral leakage by considering the following equation, which showsthat the sampling rate and the number of samples must be se-lected appropriately to improve the frequency resolution
(1)
where is the number of samples. To realize this inAnalogWeb, is selected according to Table IV. Then,the sampling rate and the number of samples are determinedaccording to the selected . However, this may increase thecomputing time. Finally, it can be said that the results of the FTof the analog signals and the FFT of the simulated signals arenearly the same, with both giving a good frequency resolution.
350 IEEE TRANSACTIONS ON EDUCATION, VOL. 56, NO. 3, AUGUST 2013
Fig. 2. Signal spectra of : (left) accurate and (right) with spectral leakage.
TABLE IVSELECTION OF THE FREQUENCY SOLUTION
III. TOOLS FOR DESIGN AND USE OF ANALOGWEB
AnalogWeb is a Web-based interface developed on both.Net and MATLAB platforms. A Web-based .Net applicationneeds .NET framework and the Visual Studio program as wellas ASP.NET editor. Furthermore, if .NET and MATLAB areto work together in the application, MATLAB Compiler andMATLAB Builder NE must be used in developing the appli-cation. When developing Web-based .Net applications withMATLAB, the first task is using the MATLAB platform, andthe second is to use the .NET platform. Using the MATLABplatform includes the creation of MATLAB functions that per-form complex processes, compiling the functions and building.NET components with MATLAB Compiler and MATLABBuilder NE. Using the .NET platform can be investigated in twoparts. The first is integrating deployed components (.dll files)and MATLAB WebFigures tool, which provides visualizationof MATLAB figures in browsers, to .NET, and the second is todesign Web interface with ASP.NET [16]. The tools used in theinterface design were the following:1) MATLAB Functions;2) MATLAB Compiler;3) MATLAB Builder NE (which includes MATLABWebFigures);
Fig. 3. Design steps and tools used in developing AnalogWeb.
4) .NET Framework;5) Visual Studio program as ASP.NET editor.The use of these tools in the design steps for AnalogWeb is
shown in Fig. 3.For using a .NET application with a deployed MATLAB
component and MATLAB WebFigures, .NET Framework andMATLAB Compiler Runtime (MCR) are required. MCR isan execution engine that executes deployed MATLAB files(.dll files) on computers/servers without an installed version ofMATLAB [16]. There is thus no license requirement or cost.Fig. 4 shows the architecture and use of AnalogWeb.
KAÇAR AND BAYILMIŞ: WEB-BASED EDUCATIONAL INTERFACE FOR ANALOG COMMUNICATION COURSE 351
Fig. 4. Architecture and use of AnalogWeb.
IV. USE OF ANALOGWEB
This section details the use of AnalogWeb, which isvery simple and easy to understand. When a user accessesAnalogWeb, the home page allows them to click a button toselect the type of modulation they want to use—either DSB,DSB-SC, SSB, or VSB amplitude modulation, or FM or PMangle modulation.Clicking the “Theoretical Information” button brings up a
Web page giving the theory of the selected technique. Users canalso access theoretical information on the discrete-time simula-tion of the technique (Sampling theory, the FFT, etc.). Clickingthe “Simulation Interface” button opens aWeb page for the sim-ulation of the selected modulation type. The first time the sim-ulation pages are opened, only the MATLAB symbol figure isshown in the figure frames. At the left of the pages, there is apanel that includes the simulation parameters; Fig. 5 shows thepanel for DSB modulation and is typical of the other panels.Two subpanels in the panel in Fig. 5 are used to set the mes-
sage signal and a carrier signal. In the message signal panel,users can choose a defined signal or use a real sound signal. Ifthey select a defined signal, they can define the message signal’sshape, amplitude, frequency, and length. The signal shape is de-termined by selecting one of five signal shapes from a drop-down list, seen in Fig. 5. Amplitude and frequency values areset by sliders. The length of the message signal is entered in asignal time textbox as seconds only for time-domain graphics. Ifa real sound signal is chosen, the user must upload an audio fileof that sound. Similarly, users can then define a carrier signal, ei-ther sine or cosine, using the drop-down list on the carrier signalpanel. There is no option to uploading a carrier signal. Oncethe message and carrier signals are defined, users click the StartSimulation button.At the end of the simulation, the graphical results are shown in
the figure frame by MATLAB WebFigures Control as in Fig. 6,which shows the results of a sample simulation for DSB mod-ulation. For this simulation, the message signal was defined as
for 0.001 s, and the carrier signal was definedas . The graphical results consist of the mes-sage signal, carrier signal, modulated signal, and their frequencyspectra. To obtain frequency spectra without spectral leakage,the sampling rates and the number of samples were appropri-ately determined by AnalogWeb as mentioned in Section II-B.As a second example, the results of a simulation of DSB-SC
modulation are shown in Fig. 7. For the simulation, the messagesignal was set as and the carrier signal was setas by the user.
Fig. 5. Panel for entering simulation parameters.
In the examples seen in Figs. 6 and 7, the message sig-nals were single sinusoids with 10- and 3.4-kHz frequencyvalues. The carrier frequency values were 80 and 40 kHz.The frequency resolution was selected automatically as 0.1 Hzaccording to Table IV by AnalogWeb. The sampling rates andthe number of samples were determined to provide the selected. Thus, the frequency spectra were obtained accurately
without spectral leakage. Their accuracy can be seen whencompared to the general spectra of in Table II.For angle modulations, there is a little variation on the carrier
signal panel because users must enter the kp and kf coefficientsof (5) and (6) to select between PM and FM, as shown at theleft in Fig. 8. Fig. 8 illustrates the results of a sample FM simu-lation with a randomly defined message signal. When users de-fine a random message signal for any technique in AnalogWeb,
352 IEEE TRANSACTIONS ON EDUCATION, VOL. 56, NO. 3, AUGUST 2013
Fig. 6. Graphical simulation results for DSB modulation.
Fig. 7. Graphical simulation results for DSB-SC modulation.
the entered amplitude value is the highest value that the mes-sage signal can approach, and the entered frequency value isthe bandwidth of the random message signal. In the examplein Fig. 8, the bandwidth is 20 kHz, and the carrier frequency is500 kHz. Therefore, was selected automatically as 0.1 Hzaccording to Table IV. The accuracy of the frequency spectracan be seen in comparison to the general spectra of Table III.The icons displayed in Fig. 8 are features of MATLAB
WebFigures. If users move the cursor on MATLABWebFigures, a bar appears above. Three of the icons are
in the middle of the bar and the fourth is on the right. The firsticon in the middle is used to move the figure, the second tozoom and the third to rotate the figure in the frame of MATLABWebFigures. The last icon on the right is to return the figure toits original dimensions.
V. ASSESSMENT OF ANALOGWEB
In order to facilitate the learning and teaching of analog mod-ulation techniques, AnalogWeb was used in conjunction withexperimental setups in the laboratory environment during an
KAÇAR AND BAYILMIŞ: WEB-BASED EDUCATIONAL INTERFACE FOR ANALOG COMMUNICATION COURSE 353
Fig. 8. Graphical simulation results for the FM angle modulation technique.
TABLE VSURVEY ITEMS
analog communication course taught by the authors in the Elec-tronic Education Department of the Technical Education Fac-ulty at Sakarya University during the Fall term of 2011. All ofthe 60 senior undergraduate students used AnalogWeb beforeusing the laboratory experimental setups. As a result, they hada higher level of understanding when they performed the actualanalog communication experiments. A survey was administeredto evaluate AnalogWeb in terms of educational contributionsand validity.The students were asked to rate AnalogWeb for eight items,
listed in Table V, on a five-point Likert-type scale excellentvery good good fair very poor . The
results are shown in Fig. 9.The first three items are about simplifying the teaching and
learning of analog modulation techniques with AnalogWeb.Students gave an average 85% positive response, suggesting
that AnalogWeb is useful as an educational tool. The fourth,fifth, and sixth items are intended to elicit feedback in the useof AnalogWeb. Because of the given negative responses for thesixth item, working and response time, the average satisfactionlevel was 766%. This is because users have to wait for nearlyhalf a minute for the results since the communication betweenthe client and server takes some time. The seventh item is aboutoverall success; the majority (65%) of the students thoughtAnalogWeb successful. The aim of the last item was to decidewhether to implement similar tools in different courses; 80% ofstudents thought the structure of AnalogWeb is appropriate foradaptation to other courses in engineering education.The effectiveness and the validity of the AnalogWeb simula-
tion tool were further evaluated by comparing students’ perfor-mance in the analog communication course’s laboratory examover two years. In the first year, without AnalogWeb, the passrate was 45 %. In the second year, with AnalogWeb, the passrate was 65%. The increase of the pass rate is attributed toAnalogWeb giving students the opportunity to carry out moreexperiments.
VI. CONCLUSION
Practical work plays an important role in engineering edu-cation in improving students’ technical skills. However, this ishigh-cost and needs a laboratory environment. When high num-bers of students and experiments are considered, Web-based in-terfaces are economical, flexible, and easy solutions, in that theydo not require laboratories or experimental equipment, and canfacilitate students’ understanding of practical applications in en-gineering education. To this end, Web-based educational inter-faces have now become one of the most important parts in CALand distance education applications and are commonly used byeducators.The most important feature of the AnalogWeb tool proposed
here is that it can be accessed with only aWeb browser; there are
354 IEEE TRANSACTIONS ON EDUCATION, VOL. 56, NO. 3, AUGUST 2013
Fig. 9. Assessment results.
no other software requirements. This, and the other features de-tailed in this paper, make AnalogWeb an appealing tool for ed-ucational purposes. AnalogWeb’s evaluation results also showit to be a successful and useful tool.
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Sezgin Kaçar received the M.Sc. degree in electronics and computer educationfrom Sakarya University, Sakarya, Turkey, in 2010.Since 2009, he has been with the Department of Electrical—Electronic En-
gineering, Sakarya University, as a Research Assistant. He performs researchin the areas of nonlinear systems analysis, Web and .net-based GUI design, andembedded systems design.
Cüneyt Bayılmış received the Ph.D. degree in electrical education fromKocaeliUniversity, Kocaeli, Turkey, in 2006.Since 2008, he has been with the Department of Electrical—Electronic En-
gineering, Sakarya University, Turkey, as a Lecturer. He became an AssociateProfessor in 2011. He performs research in the areas of wireless sensor net-works, embedded systems technology, modeling, and simulation.
