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Satellite Virtual Classroom Environments
Abstract
In a Tele-Education environment, the concept of virtual classroom is commonly used. Within this concept, we can find two kind of tools or services:
The implementation of a virtual classroom can be done by using different tools or services included in any of the two types above mentioned, and different communications networks for each kind of tools.
In the case of the TEN project, as it covers 6 European countries, the most cost-effective solution has been to use satellite transmission.
What kind of solution we choose to implement our Virtual Classroom Network will depend much on how many remote classrooms we intend to have, how geographically disperse they are, which technological facilities we have available, and of course, how much money we want to spend. It shouldn't be forgotten that there is not a universal solution to meet all our needs of distance education.
Satellite Virtual Classroom Environments
What is a virtual-classroom? What is really included within this concept so often used in tele- education environments? We all know quite well the traditional class concept, as the ones we used to attend in schools, universities, etc. There we have in one single room one teacher and a group of learners, one blackboard, maybe a slides projector, and, if we are lucky, some video facilities. In that place, and using those facilities, the teacher gives a lecture to the learners physically present there.
What changes if we add "virtual" to that classroom? In this case, we have the same actors, a teacher and some learners (and as we will see later, we might need a tutor), and the same facilities. What really changes is that teacher and learners may not be in the same place (and even at the same time). Thus with the virtual matter we intend to have classes which are independent from the "space" and "time" variables.
When we talk about "space" independence we usually refer to real-time tools or services; if we consider the "time" independence then we are in the case of deferred-time tools or services.
Basically, in the case of real-time tools, there will be on-line contact between teacher/tutor and learners or among the learners themselves (they will be interacting simultaneously). In the deferred-time tools, the contacts will be off-line, and the interaction between the actors in the virtual classroom will not happen at the same time. The usual situation is that a global virtual classroom environment includes both types of tools or services. -
So, if we are in the case of space independence, this means that teacher and learners can be located in different places (rooms, buildings, cities, countries ...) but at the same time, thus the learners can interact with the teacher during the class. We will designate this case as Real-time Virtual Classroom.
And if we are independent also from the time variable, then, the interaction between teacher and learner, and among learners, does not need all the actors to be present simultaneously (maybe only during some short lectures of the teacher), then we will be talking about Deferred-time Virtual Classroom.
The table below shows some tools which might be used in a virtual classroom environment
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Deferred Time Tools |
Real Time Tools |
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· Audioconference |
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· Computer Conferencing |
· Videoconference |
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· File Transfer |
· Applications Sharing |
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· World Wide Web |
· Collaborative Working |
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· Management Tools |
· Real-Video |
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· Specific developed tools |
· MBONE |
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· Specific developed tools (TEN system) |
Therefore once you have decided which are the tools you need in order to cover your training requirements, you will have to choose then which communications network you will use. Some possibilities are shown in the following table:
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PHONE |
ISDN |
LAN |
ATM |
DBS |
VSAT |
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Bandwidth |
9,6-33,6Kbps |
64Kbps-2Mbps |
10 Mbps |
1,544 -622 Mbps |
7 Mhz |
2 - 4 Mbps |
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Symmetry |
Symmetric |
Symmetric |
Symmetric |
Symmetric |
Asymmetric |
On demand |
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Bidirectional |
Yes |
Yes
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Yes |
Yes |
NO |
Yes |
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Multicast |
Reduced |
Reduced |
High |
High |
NO |
Yes* |
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Broadcast |
NO |
NO |
Yes |
NO |
Yes |
Yes |
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Deferred Time Tools |
Yes |
Yes |
Yes |
Yes |
Yes |
Yes |
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Real Time Tools |
NO |
Some |
Yes |
Yes |
Yes |
Yes |
* if implemented
where you can see that the bandwidth limit for using real-time tools effectively might be around 2 Mbps.
So now, by matching both tables, and depending on which infrastructures are available in the area you want to implement the virtual classroom, you might have different possibilities. Or maybe you discover you have just one, which might be the case in a geographically disperse area with no terrestrial links available, where the only choice will be to use satellite. Anyway, this is the time to start to consider the economical aspects of the possible solutions with the purpose of finding out which suits best to the specific situation, we will come back to these
aspects afterwards. In the case of the TEN Project (Trans-European Tele-Education Network), there was a need of a 2Mbps link between 6 different countries in Europe, and any solution using terrestrial links was much more expensive than the satellite solution.
In a the Real-time Virtual Classroom process, the essential part is the communication from the teacher to the learners. For this reason high speed channels (about 2 Mbps) are needed for the teacher and slower ones (about 64 Kbps) for the learners. It is clearly an asymmetric communication, with a big information flow in one direction and a small one in the return direction. Some possibilities to solve this kind of communication might be satellite, ISDN (Primary Access) or a cable network.
Concerning the Deferred-Time Virtual Classroom, apart from several lectures of the teacher which might be realised as in the Real-time Virtual Classroom, the communication between the teacher and the learners is more symmetric, and, talking properly, the teacher becomes a tutor in this case. The functionalities needed are e-mail, computer conferencing, maybe tools sharing and videoconference. This can be achieved using Internet and an ISDN Basic Access.
TEN PROJECT
The TEN Project (Trans-European Tele-Education Network) is a European project approved in the calls of 15th March, 1995 and it is part-funded by the Telematics Applications Programme co-ordinated by the DG XIII of the European Commission.
There are eight countries involved: Belgium, Greece, Ireland, The Netherlands, France, Portugal, United Kingdom and Spain.
TEN is a Tele-Education experience which uses the concept of "virtual distributed classroom in real time" and is based on an integrated satellite (HISPASAT and EUTELSAT) and terrestrial (ISDN and LAN) network. This network will be the basis of an interactive multimedia Tele- Education system that interconnects six European countries by using the CODE/VSAT satellite data communication network plus ISDN.
The system will fully integrate VSAT/ISDN and LAN and will be compatible with the Internet data network. The TEN system allows a training strategy which follows a multimedia virtual distributed classroom model, integrating voice, video and data. Its interactive application runs on a standard PC Windows environment. It uses Indeo and H261 video coding. Standard PC tools can be utilised for preparing the necessary training materials.
The network will be composed by a HUB station located in Madrid and seven VSAT stations: tx/rx_VSAT+ISDN in Madrid, Leuven, Thessaloniki, Stafford and Dublin, and rx_VSAT+ISDN in Lisbon and Malaga. The return channel of these last two stations is only by ISDN.
Some of the TEN pilot courses are:
At the end of the foreseen period the TEN Project will have provided at least 190 training hours with 700 users approximately.
The TEN Project intends that the users of the application test and experiment with the system at a transnational level so that it becomes the seed for a European tale-education network.
OTHER PROJECTS
Some other projects outside Europe using satellite, mainly to broadcast the lectures, and some other facilities as phone, fax, e-mail or videoconference for the interaction between learners and teachers are:>
IMPLEMENTATION OF A SATELLITE VIRTUAL CLASSROOM
The requirements in the TEN project to achive a Real-Time Virtual Classroom were
The next step then is how to implement each one. A thorough cost study is necessary and, depending on how many remote classrooms are foreseen and how disperse those remote classrooms are, you can find out quite easily which is the best solution for a particular Virtual Classroom.
If you consider the example of the TEN project, you will find the central station in Madrid and remote stations in Belgium, United Kingdom, Ireland, Portugal, Greece and Spain. If we would have chosen ISDN as a solution, we would have needed 6 Primary Accesses in the Central Station and one in each remote station. In that case one hour of transmission from the Central Station to the 6 remote stations would cost 2882 Ecus, whereas using Eutelsat it will cost around 473 Ecus.
So we can deduce that, if we have a broad geographical distribution, the more cost effective solution may be to use satellite, specially if we have an asymmetric flow of information. We should notice that this cost will not increase if we include more remote classrooms in our network.
The case of the return channel for the learner interaction is quite different, since only about 64Kbps are needed. It can be solved by making use of an ISDN Basic Access without having high costs (e.g. in the TEN project we might have opened all the ISDN return channels with a cost of 96 Ecus/hour, however we do not need to do that). Of course, if an equipment which allow you to have a satellite return channel is available, then the cost will not increase at all.
Finally, we need an application to manage all the satellite communications and to interface with the users. There we might not find standard solutions, and have to develop our own software, having in mind how important the interface is, as the users do not see all the communications components below, but just the final interface. It will definitely play a significant part in the final success of the courses.
which might help to compare with the present cost of the courses using traditional methods
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To conclude. I will enumerate some advantages of a Virtual Classroom:
