The Course”Principles of Communications Engineering”

at the Virtual University of BavariaBernd Matschkal, Bernd Westrich, Johannes B. Huber

Institute for Information Transmission, University of Erlangen–NurembergCauerstrasse 7/LIT, 91058 Erlangen, Germany, www.LNT.de

Phone: +49 9131 85-27112, Fax: +49 9131 85-28919E-mail: �matschkal,westrich,huber�@LNT.de

ABSTRACT

Within the scope of a project in cooperation with the”Virtual University of Bavaria” the course ”Principlesof Communications Engineering” of the EE-Curriculum 1

at the University of Erlangen–Nuremberg has been con-verted into a virtual learning environment that can becompletely attended via internet. It mainly consists of twoparts, the course itself and a virtual laboratory.

The course part of the virtual learning environment isbased on the recording of the ”real” course. By addinganimations to the static slides of the lecture notes usingthe Macromedia Shockwave Director Studio as well asstreaming the course’s remastered audio signal, a virtualcourse has been created.

In the laboratory part, the student has the possibilityto perform experiments (e.g. the simulation of a radiotransmission) online via web-interface in order to learnthe course’s main purposes in a much more practicalway. The virtual laboratory is implemented by means of aMATLAB web server which allows to perform excellentscientific calculations and to make the results accessiblevia internet by using only one single MATLAB license.

The paper presents the virtual learning environmentfor both, the course and the laboratory part. Furthermorewe explain the MATLAB web server concept and itsadvantages for scientific education.

Keywords: Virtual University, Communications Engi-neering, Course, Laboratory, MATLAB Webserver

1. INTRODUCTION

The ”Virtual University of Bavaria” (abbr.: ”vhb”,http://www.vhb.org) is a network of 35 bavarian univer-sities whose aim is to improve and coordinate the useand development of multimedia in academic educationand training. This network provides virtual learning en-vironments for students and in the near future for other

1Electrical Engineering-Curriculum

parties interested in advanced training. The students ofthe vhb have access to high quality multimedial coursesand laboratories, independent of time and location. Thevhb itself is not a standalone university, moreover it isa common institution of universities and universities ofapplied sciences in the federal state of Bavaria, Germany.

As one of the main universities within the vhb, the Uni-versity of Erlangen-Nuremberg with its institutes providesseveral courses and virtual laboratories for EE-educationsuch as the ”Principles of Communications Engineering”at the Institute of Information Transmission.

This course – or to be more exact, the non-virtual”real” course – is a main subject for students in the fieldof Electrical Engineering (5th semester) studying at theUniversity of Erlangen-Nuremberg and comprises about600 slides and several exercises [2]. Beginning with somebasics concerning signals and channel models, this coursecovers a wide range of information transmission methodsthe traditional analog modulation processes as well as thestate-of-the-art digital communications schemes.

Recently, within the scope of two projects in cooper-ation with the vhb this course is about being convertedinto a virtual learning environment that can be completelyattended via the internet. Whereas the first project (the”analog part”) of the course is finished, the developmentof the second part (the ”digital part”) is currently inprogress.

Each of these two projects mainly consists of twofurther parts, the course itself and the virtual laboratorywhich will both be presented in this paper. Concerningthe laboratory, we will take a closer look to its imple-mentation by means of a MATLAB web server.

2. THE VIRTUAL COURSE

The course part of our virtual learning environmentis based on the recording of the ”real” course whichhad been done during last year’s winter term. Usingthe Macromedia Shockwave Director Studio, lots of an-

imations have been added to the static slides of thelecture notes in order to provide background information,illustrate basic concepts and to emphasize facts as well asformulas in the same way, as professor Huber does it inthe ”live” course. In addition to that, the course’s audiosignal (voice of Prof. Huber) has been remastered andconnected with the slides. By streaming this audio signalvia the web a virtual course has been created. Of course,the presentation is in German language.

Fig. 1. ”Course-part” of the virtual learning environment(includes audio-stream)

Fig. 1 shows the user interface. The menu tree on theleft side gives an overview of all chapters of the course,the exercises, the laboratory etc. and can be used fornavigation. On the right side, the slides of the course scriptthat correspond to the actual time-position of the audio-stream are automatically displayed. Figures, formulas etc.are highlighted or generated synchronously to the voice.Thus, an intensive animation of the slides is achieved.While listening to the course, the preceding slides arecontinuously loaded in the background so that they areavailable as soon as they are needed. The student cannavigate within the course via web-browser using thenavigational buttons at the bottom of the slides – he isable to decide his appropriate speed of learning and thushas the possibility of repeating difficult topics.

One aim of our project was to make everything fullaccessible by the use of an analog modem with a dataspeed of only 56 kbps – this means the student doesnot need to have a high speed internet-connection toattend our virtual learning environment. This includes thecontinuous audio stream as well as the slides with coloredanimations.

Moreover, the student can view and download theexercises dealing with the course’s facts in order to bewell prepared for the exam at the end of the semester.

3. THE VIRTUAL LABORATORY

The second main part of our virtual learning environ-ment is the so called ”virtual laboratory” in communi-

cations engineering whose aim is to teach the course’smain purposes in a much more practical way. This partis modelled on our ”real” laboratory which uses digitalsignal processor boards (DSPs), oscilloscopes and spec-trum analyzers and – of course – can be attended only byour local students. This laboratory comprises about 130practical tasks and experiments (measurements, signaland data transmissions etc.) that have to be done by thestudents, usually within 6 afternoons.

We succeeded in converting this real laboratory intoa virtual laboratory in a way that gives the studentthe opportunity to do the same practical exercises viaweb browser that he could have done locally at ourinstitute. He is able to perform experiments concerningsignals and systems including filtering as well as signaldistortion. Moreover we developed the simulation of aradio transmission system via web-interface which willbe introduced in the following.

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Fig. 2. Radio transmission system (model)

The model shown in Fig. 2 forms the basis of ourconsidered radio transmission system. On the left side,an audio signal (e.g. speech, music) is fed into a ra-dio transmitter. The transmitter (e.g. a radio station)processes this audio signal (”modulation”) according togiven parameters (modulation scheme, carrier frequency,etc.) and generates a high frequent radio signal which istransmitted via the antenna. This radio signal is carried(and often distorted) via the so-called radio channel tothe antenna of the receiver (e.g. a car radio). There thereceived high frequent signal is demodulated in a certainway (modulation scheme, carrier frequency – often withdeviations, etc.). If everything went fine, the receiveroutput-signal represents the initial audio-signal in moreor less good quality.

Fig. 3. Radio transmission system (implementation)

Our implementation of this model – meaning to makeit capable for the world wide web – is shown in Fig. 3.

Both the transmitter and the receiver are replaced bya computer terminal operated by the user (student) witha web browser. Regarding the transmitter side, there is a”Transmitter Input-Webpage” (dedicated URL, see Fig. 4)where the student has to enter all relevant parameters:he can for example choose between several input audio-signals (different kinds of music, speech, etc.) and hasto specify all relevant transmitter-parameters such as themodulation scheme and the carrier frequency. By pressing

Fig. 4. Transmitter Input-Webpage

the ”send”-button, this data is sent via internet to a server(MATLAB Webserver, see Chapter 4) which is locatedat our institute in Erlangen. There, according to theindividual adjustments of the student, the high frequenttransmitter output-signal is calculated but – instead ofbroadcasting it via an antenna – it is saved on the harddisk of the server. In addition to that, a ”TransmitterOutput-Webpage” is calculated where all concerned sig-nals are visualized by diagrams. The audio-signals canbe listened to via mouseclick (realmedia audio-stream)and the diagrams can be zoomed for a more detailedinvestigation.

The receiver side is quite similar: there is another dedi-cated URL, namely the ”Receiver Input-Webpage”, whereall relevant receiver parameters have to be specified bythe student. Moreover, additional parameters that describean information transmission system in real life such assignal-distortion by noise, carrier frequency deviation orphase-offset can be fed into the system via webpage.By pressing the ”receive”-button, the radio signal thathas been ”broadcasted” by this user is loaded from harddisk and is processed (demodulated) in the way that hasbeen specified by the student’s receiver-parameters. AnOutput-Webpage (Fig. 5) provides information about theresults (concerned signals, diagrams, calculated signal-to-noise-ratios (SNR) etc.). Moreover, the student has thepossibility of listening to the demodulated receiver output-signal via audio-streaming and thus can verify whether the

Fig. 5. Receiver Output-Webpage:received signal and demodulated signal(amplitude modulation with carrier)

transmission was successful.It has to be emphasized that every virtual radio trans-

mission is individually calculated depending on the pa-rameters given by the student, no ”pre-calculated” ortabulated results are used. Therefore this kind of virtuallaboratory is very close to reality.

Moreover, the exercises concerning the virtual labora-tory are available for download as PDF-Documents.

4. THE MATLAB WEBSERVER CONCEPT

Our virtual laboratory is implemented by means ofa MATLAB web server. We have chosen this solutionbecause of the following reasons: MATLAB is a verypowerful language of technical computing supplied by”The MathWorks, Inc.” [1] which enables to performexcellent scientific calculations (including charts, pictures,sound, animations, etc.). A major problem of developingweb-based scientific applications using well-known pro-gramming languages like JAVA etc. is that they provideonly poor features concerning specialized scientific cal-culations and presentations. For example, if you want toillustrate data by means of a multi-colored 3-dimensionalplot with interactive zoom and rotate capabilities, youeither have to write a sophisticated function for thiskind of plotting or you have to spend a lot of time inlooking for existing libraries and their application. UsingMATLAB, 3-dimensional plotting is a ”standard feature”.This might be one of the reasons why MATLAB hasbeen established in science as programming language for

numerical scientific developments. Therefore the main-tenance of projects based on MATLAB source code isoften much more easier considering the know-how at mostinstitutes.

Generally, the main problem of powerful scientificsoftware – especially if it is considered to be used for edu-cational purposes – is the licensing problem. This means,that for each student who intends to use this software –e.g. at a virtual laboratory – one particular license has tobe purchased. The MATLAB web server concept allowsto perform individual MATLAB calculations (triggeredvia web-interface) and to make the results accessible viainternet by using only one MATLAB license.

Fig. 6. The MATLAB Webserver (overview)

Fig. 6 shows the basic concept of the MATLABWebserver. The user (student) only needs a conventionalweb browser and access to the world wide web – hedoes not need to have a local installation of MATLABon his system. His browser communicates via internetwith a common http-server (webserver) which interactswith the MATLAB Webserver. Calculations, such as thepreparation of images, sound and animations, are centrallyprocessed on the MATLAB Webserver which is locatedat the university. Data exchange is performed via http(HyperText Transfer Protocol) respectively HTML-pages.

Fig. 7 gives a more detailed explanation of the dataprocessing that is done by the MATLAB Webserverarchitecture. As we explained (see chapter 3), the inputdata – in our case the parameters for the transmitter andthe receiver – is acquired from the user by means of awebpage (”Input-Webpage”). This webpage mainly con-sists of a HTML-Form whose variables are subsequentlysubmitted (”send”/”receive”-buttons) via the internet andpassed to the http-daemon (common webserver, usuallyat the same location as the MATLAB Webserver).

There, a server-side cgi-script analyzes these parame-ters and forwards them to the central unit, the so-called”Matlabserver”. ”Matlabserver” itself is a program thatcoordinates the client (user) side as well as the MATLABserver side, meaning that for every request of a client,a MATLAB process is startet which performs the re-

Fig. 7. Inside the MATLAB Webserver

quired calculations (M-files), generates images, sound andanimations. The calculation results (MATLAB supportsseveral multimedia formats, e.g. jpg, png, tif, wav.) aredirectly passed to the http-daemon and stored there onthe webserver for that they can be accessed via web-linksafterwards. Moreover the Output-Webpage is generatedwhere images and diagrams are embedded as HTML-elements, further multimedia elements such as streamingsound are accessible via HTML-Links.

5. STUDENT SUPERVISION

Fig. 8. Chat-Environment with whiteboard

Concerning the supervision of the students attendingour virtual course – besides e-mail and phone – a smallchat-environment is provided. Here, the student can dis-cuss online with the supervisors and his fellow studentsin order to ask questions, solve problems etc. Within thescope of this chat-environment, it is also possible to createsmall drawings on the graphical user interface which canbe amended by all others who are online (Fig. 8).

6. CONCLUDING REMARKS

By introducing our virtual learning environment wepresented a multimedia course from the field of academiceducation. Moreover we explained how to transform areal laboratory into a virtual laboratory, especially ifinteractive scientific calculations and data presentation isemphasized. Finally we showed our solution of supervis-ing virtual students via the world wide web.

REFERENCES

[1] Mathworks [online]. www.mathworks.com.[2] J. Huber. Skriptum zur Vorlesung Nachrichtenubertragung.

Lehrstuhl fur Nachrichtentechnik II, Universitat Erlangen–Nurnberg, 2001.