EWSD

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EWSD is a product name for electronic telephone switching systems from Siemens AG (now Nokia Solutions and Networks ). The name is the abbreviation of the term e lektronisches W ähl s ystem D igital due.

operation area

Exchanges of the EWSD type for public telephone networks can, like exchanges from other manufacturers, be supplied either as a local exchange , as a long-distance exchange (nationwide) or as a combination of both. But also called DIVA (foreign exchange).

There are different variants for fixed network and mobile network : C-Netz , D-Netz (as GSM-900 ). Customers of EWSD switching systems are z. B. Telecommunications companies such as Deutsche Telekom , M-net , Versatel , Colt Technology Services , QSC , Telekom Austria , Vodafone or dtms . Other companies use systems from other manufacturers. Siemens claims to have sold EWSD systems in over 120 countries.

history

The system was developed by Siemens AG . It was the second generation of electronic dialing systems from Siemens for the system Committee ( E lektronisches W ähl S ystem A nalog). Companies like DeTeWe and Bosch built the system under license. The first EWSD system from Siemens was put into operation in 1980 in Hamburg as a long-distance exchange, where it replaced the analog switching method used up to that point. Shortly afterwards the first EWSD local exchange followed in Hamburg-Wandsbek . An adapted version (OES-E) was used in Austria from 1981. DeTeWe put the first EWSD for long-distance switching into operation in 1985 , and one year later the first digital local exchange built by DeTeWe. DeTeWe PCN implemented switching network nodes at over 180 locations. Deutsche Telekom uses EWSD from Siemens and System 12 or S12 from SEL or Alcatel . The proportion of EWSD systems is greater than the proportion of system 12, since all long-distance and international exchanges were set up in EWSD, only EWSD was used in the C network and the D network as the first GSM network from both network providers only was built in EWSD technology. Siemens stopped its own hardware production in 2003 and dissolved the EWSD division on December 31, 2005. The "EWSD" system was the world's best-selling fixed line switching system at the time. Siemens has not made the leap into the Internet age with its switching systems. They were too big, too expensive and had a much higher power consumption compared to the devices of the growing competition such as network technology providers Cisco , Juniper or other Asian competitors Huawei , which used IP technology.
The product range, which has been part of Nokia since 2007 , was no longer actively marketed and discontinued in 2017. As early as 2007, there was no more active marketing.

In 2018, EWSD systems were only in operation as OVST .

construction

The modules are inserted vertically in module frames , the back wall of which establishes the electrical connections between them. Several assembly frames are placed one on top of the other in a rack, which is locked like a cabinet with doors on the front and back. The assemblies are accessible from the front, cables are connected at the rear. The safety rail is located on the top level of a rack row. On the lowest level there are fans that ensure air circulation in the cabinet. This dissipates the waste heat from the assemblies. An EWSD system can consist of several cabinets, which is referred to as a rack row. The cables can be fed through a surface grate under the ceiling or through a false floor.

hardware

The main components of an EWSD system are

  • CP ( Central Processor or Coordination Processor )
  • MB ( Message Buffer )
  • CCNC ( Common Channel Network Control ), replaced in newer switches by SSNC ( Signaling System Network Control )
  • LTG ( Line Trunk Group )
  • DLU ( Digital Line Unit )
  • SN ( Switching Network , coupling network )

All central system units have a redundant structure. In the event of an error, the non-mediating side can take over the operation immediately.

The connection part DLU takes the analog and ISDN - subscriber lines and converts among other things, the analog signals into digital signals (one of BORSCHTs functions of a subscriber circuit). The digital signals are assigned to a channel of a PCM system. Digital connection lines, for example an ISDN basic connection , are assigned directly to a PCM channel. The traffic is concentrated in the DLU and forwarded to LTG type B. There is also the inclusion of PCM30 systems, for example primary rate connections or V5.2 controlled access networks. They are also connected to the coupling network via LTG type B. Other functions for controlling the connection, such as generating the ringing voltage and recording dialing information ( pulse dialing , multi-frequency dialing ) are integrated in the DLU. The connector is controlled by the group processor. DLU can be operated in remote peripheral units (APE) . The LTG type C is used for the connection via PCM30 to other exchanges. The signaling for these connections is also terminated there. Different signaling systems can be used, for example SS7 , MFC R2, IKZ , E&M.

The switching matrix consists of room switching stages with 4 room switching multiples, 16/16 (16 inputs and 16 outputs) and a time switching stage with 16 time switching multiples with 4 outputs and inputs (4/4). The spatial and temporal conversion of the channels takes place in the time coupling stage. The coordination processor CP takes over control .

There are the following types of coordination processors:

  • CP 103 with max. 22,000 connection attempts during the rush hour
  • CP 112 with max. 60,000 connection attempts during the rush hour
  • CP 113D with up to one million connection attempts during the rush hour
  • CP 113C with up to six million connection attempts during rush hour (C for Compact)
  • CP 113E with up to ten million connection attempts during rush hour

software

The EWSD software is called APS ( Application Program System ). The APS is located on a hard disk and is a proprietary operating system developed by Siemens with the participation of Bosch especially for EWSD systems . It is mainly programmed in the CHILL programming language. The user software is switch-specific and is used, among other things, to control traffic , search for routes and record charges. The support software is used to generate data, translate programs, link modules and manage the libraries. The operating and data communication software is used for cooperation between the maintenance centers and the switching centers.

Technical specifications

  • Number of subscriber lines up to 250,000
  • Number of connecting lines 240,000
  • Switchable traffic 25,200 Erlang
  • Connection attempts during rush hour 10 million
  • Operating voltages 48 V -, 60 V -, 90 V -
  • Zoning (fee zones) 127 zones, 6 tariffs per zone
  • Tariff switching in the 15-minute rhythm
  • Space requirement for 10,000 subscriber lines 35 m²

literature

  • Otfried Georg: Telecommunication technology . Springer Verlag, Berlin / Heidelberg 1996, ISBN 3-540-61381-1 .
  • P. Gnanasivam: Telecommunication Switching and Networks . New Age International Limited Publishers, New Delhi 2005, ISBN 81-224-1583-0 .
  • Axel Pink, Heinz Koßmann: Software development for communication networks . Springer Verlag, Berlin / Heidelberg 2002, ISBN 3-642-62792-7 .
  • Wolf-Dieter Haaß: Handbook of the communication networks . Springer Verlag, Berlin / Heidelberg 1997, ISBN 3-642-63825-2 .

Web links

Individual evidence

  1. ^ The digital electronic dialing system EWSD ( Memento from April 7, 2005 in the Internet Archive ) Description EWSD on DeTeWe PCN
  2. ↑ Siemens® EWSD Digital Electronic Switching System ( Memento from October 20, 2017 in the Internet Archive ) (English)