ISDN and Mezzanines


Without any doubt telecommunication is one of the fastest growing markets. A committee of the European Union expects that there will be about 60 million employees in the telecom branch at the end of the century compared with less than 20 million nowadays. Experts estimate that the telecom branch will replace the automobile industry as driving force for the economic growth in 2000.

ISDN (Integrated Services Digital Network) makes an essantial contribution to the growth of the telecom branch especially in Europe. The increase of ISDN interfaces was nearly 70% in Germany in 1995. The German Telekom has installed more than 3.6 million ISDN channels up to now.

What are the advantages of ISDN ?

ISDN offers higher transmission rates than modems over analog lines. Commonly available modems have a maximum speed of 33.6 kbps and they routinely go no faster than 28.8 kbps depending on the quality of the connection.

With an ISDN Basic Rate Interface (BRI or S0) it is possible to have 2 independent B channels with 64 kbps (in USA partly 56 kbps) each on the same physical line. It is possible to bundle the B channels to increase the bandwidth for data transmission. The Primary Rate Interface (PRI or S2M) offers a 2 mbps E1 interface with 30 B channels with 64 kbps each (in USA 23 B channels on a T1 interface) on a four wire line.

Based on the digital transmission and on the D channel used for signalling ("Out-of-band signalling") call establishment is very fast (in Germany less than 1.5 seconds). Therefore it is efficient to disconnect router connections when there is no traffic on the network and to reconnect when needed. The signalling on the D channel also transfers the caller number (important for access control for data connections), the dialed number (for Direct Dial In), the type of call (data, telefax, voice etc.) and the billing information without disturbing established connections.

Besides telephony the ISDN BRI is used frequently for fast data transfer, for instance Internet access, in our offices for several years now. ISDN solutions for PCs are already cheaper than high quality modems.

What solutions can we think of using Mezzanines with ISDN ?

Regarding the Basic Rate Interface we can think of applications like remote control or maintenance of automation systems or remote update of software. For special telecom applications IP or PMC modules may be interesting because of their industrial quality.

The use of modules for the Primary Rate Interface or solutions with different interfaces seems to be very advantageous because of the possible scalability. For professional systems it is efficient to use IP or PMC modules together with VME carrier boards. Because of the standardization of the pinout of P2 for the SCbus it is also possible to build PABX or other speech applications, where the channels can be routed between the different boards without delay or need of CPU performance over a proprietary backplane.

Ikon is specialized on building COTS products for telecom solutions and therefore already uses Mezzanine modules, e.g. from TEWS Datentechnik. The modules and the ikon ISDN software are certified for Germany and all countries using Euro-ISDN.

Figure 1: Flex Access Server based on VMEbus System

Examples of existing solutions:

The examples show applications for an efficient use of Mezzanine modules for telecom solutions. Certainly there will be a lot of interesting solutions in the future based on the variety of available VME boards, operating systems, IP and PMC modules.

Karl Judex, General Manager ikon GmbH
Uwe Tews, General Manager TEWS Datentechnik

last update: 15.08.2008

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