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Communications Networks
This is the descriptive layer

Technological evolution of the telecommunications world are introducing to the Virtual Campus a whole range of new connection possibilities. The aim of the following sections is to throw light on the new concepts in order to help you to choose the configuration that will best suit your needs.

Connection from home to the Virtual Campus can be effected by means of the following networks: BTN, ISDN, ADSL and CABLE. Tests have also been conducted to search for new ways linked to mobile telephony such as the GPRS (General Packet Radio Service) system. Even though from a technological standpoint this is a valid option, it is not an effective one for the UOC's educational system, owing to the costs involved. In the near future, new ways will appear, which will be linked to satellite. The following possibilities are currently available.

Integrated Services Digital Network (ISDN)

What is

This is the digital technology solution. The technology of digital transmission allows for the use of the same network for the transmission of voice, data, images, etc., instead of using, as has been done up to now, a specific network for each type of information. The connection of the PC to the network is effected by means of an ISDN adapter* (ISDN card). Unlike the conventional telephone line, an ISDN line needs a small device at the user's home end, which in telephone jargon is known as network adapter*.

A basic ISDN access is made up of three channels, of which you will use only two. This will allow you to have your PC connected on one of the channels while receiving or making telephone calls on the other. This implies greater availability and will stop your phone from being engaged while you are using the computer.


Advantages

It provides the sort of quality and the services which are impossible to obtain through BTN. On the other hand, each of these channels works at more speed (64,000 bits per second), almost twice as fast as a BTN line in most cases. This implies that the same amount of information will be obtained in less time, and therefore phone costs will be lower.

In addition, the quality of digital lines is higher than that of analogue lines. Thus, the chance of error in transmissions is reduced.

Finally, it should be noted that in ISDN, the time involved in connecting the call is less. When calling the UOC, for instance, you may connect in barely two seconds, as opposed to the ten seconds involved in BTN.

The sum of all these factors (speed, reliability, and time of connection of call) supposes important savings in the phone bill, and a more comfortable way of working.


Drawbacks

The main drawback of ISDN is that you have to subscribe at home, which means that staff from Telefónica will have to come to your home, as when one requests a new telephone set.

It should be taken into account that Telefónica cannot yet provide this technology for the whole of the Spanish territory, so it is possible that you may still not be able to have an ISDN access at home. Despite Telefónica's calculations, experience during these years shows that around 30% of installations have problems which can delay the proper working of the line for a number of months.

On an ISDN line you may make and receive phone calls in the normal way, as with BTN. The difference is that ISDN incorporates at an identical cost many of the facilities that BTN bills separately, like the re-routing of a call, call wait, etc. The cost of calls is identical for both networks. What is different are the monthly rates and the initial subscription rate.

Subsequent migration to ADSL with ISDN is more difficult than with BTN. For example, some operators do not offer ADSL on ISDN lines.

Possible Configurations at Home

  ISDN Network for data, with a/b adapter (makes use of the former installation for voice)
ISDN Network for data, with a/b adapter (makes use of the former installation for voice)
 Advantages
Possibility of working at the Virtual Campus without the phone being engaged.
Speed of transmission, reliability and connection.
Single line for telephony and connection to the Campus.
Chance of using analogue devices already installed at home.
Configuration is cheaper.
 Drawbacks
You have to subscribe to an ISDN line.
You have to change your telephone number.
Cannot take advantage of ISDN telephony facilities, such as, call wait, re-routing...
It is not always available, as it depends on Telefónica's public central switchboard.
Subsequent migration to ADSL with ISDN is more difficult.


  An ISDN for data and a BTN for voice
An ISDN for data and a BTN for voice
 Advantages
Those proper to ISDN for connection to the Campus: speed of transmission, reliability, and time of connection of call.
Your telephone is not engaged while you are connected to the Campus.
You can keep the same telephone number.
 Drawbacks
You have to go to all the bother of subscribing to an ISDN line.
You have to pay for a second line.
It does not take advantage of ISDN telephony facilities such as call wait, re-routing...
It is not always available, as it depends on Telefónica's public central switchboard.


  An ISDN line with a passive bus, for both voice and data
An ISDN line with a passive bus, for both voice and data
 Advantages
Your telephone is not engaged while you are working at the Campus.
Those proper to ISDN for connection to the Campus (speed of transmission, reliability, and time of connection of call), and for telephony (call wait, re-routing...).
Single line for telephony and connection to the Campus.
 Drawbacks
You have to go to all the bother of subscribing to an ISDN line.
You have to change your telephone number.
ISDN has no fax or cordless telephone facilities.
It is not always available, as it depends on Telefónica's public central switchboard.
Subsequent migration to ADSL with ISDN is more difficult.

 

 

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mirador@uoc.edu       © FUOC 2001       Last updated data: 20.10.03