Telecommunication test network - xDSL subnetwork

Reference model: The model of ADSL (Asymmetric Digital Subcriber Line)

Content:

• Introduction
• Build-up of the xDSL network
• Main parts of the subnetwork

Introduction

There are two DSL subnetworks built up in the test network.

First we will study the operation, examination methods and build-up of the classical digital subscriber system (ADSL, HDSL, SDSL, SHDSL) in the xDSL subnetwork of the test network. Second we will study the build-up, operation and examination methods of the improved ADSL2, ADSL2+ digital subscriber transmission system in the ADSL2 subnetwork of the test network.

The following figure shows the build-up of the xDSL subnetwork:

Main parts of the subnetwork:

• Broadband network - broadband packet switched network.
  Its elements:
  • BME router - It provides the access to the public Internet. The xDSL subnetwork connects to a 100 Mbit/s Ethernet port of this router.
  • Traffic generator - It generates IP traffic for testing purposes.
  • DSLGW - ISP router, gateway - It realizes the router of the provider in the xDSL test network. Besides sending IP packets towards users (routing, address translation) it encapsulates the Ethernet frames to be appropriate for DSLAMs (STM-1/ATM, VLAN tagged Ethernet).
  • ATM Switch - It is used to join the living and testing traffic.

• Narrowband network - the classic PSTN/ISDN network
  Its elements:
  • SPC exchange - Definity
  • ISDN traffic generator - It generates ISDN line signal for testing purposes.

• Classic xDSL DSLAM (Digital Subscriber Line Access Multiplexer)
  It is the network adapter device of the xDSL system.

• Improved ADSL2, ADSL2+ DSLAM

• Line simulator - Előfizetői vonalszimulátor
  Line simulator is suitable for a simultaneous simulation of one line (maximum two lines), the other lines are replaced with a short cut.

• CPN - Customer Premise Network - Network of the user
  It contains several terminal devices, which are used partially for test laboratory purposes, and partially for educational purposes.
  • Test section - A network built up for testing purposes. Its elements:
    • ATU-R - ADSL NT: ADSL modem (with 10Mb Ethernet or 25.6Mb ATM user interface)
      • ATU-R ISDN - ADSL modem, ISDN works under ADSL band
      • ATU-R POTS - ADSL modem, POTS works under ADSL band
    • STU-R - SDSL NT: the SDSL modem (with 10Mb Ethernet or 2 Mbit/s PCM user interface)
      • STU-R SHDSL - SHDSL modem (Trellis coded PAM)
      • STU-R SDSL - SDSL modem (encoding: 2B1Q)
    • S - splitter - an electronic filter to split (separate) signals of ADSL and PSTN/ISDN
    • BER tester - to measure bit error ratio

  • Educational section - A subscriber network built up for educational purposes. Its elements: :
    • ATU-R - ADSL NT: ADSL modem (with 10Mb Ethernet or 25.6Mb ATM user interface)
      • ATU-R ISDN - ADSL modem, ISDN works under ADSL band
      • ATU-R POTS - ADSL modem, POTS works under ADSL band
    • NT - Network Termination of the ISDN subscriber network
    • TA - Terminal adapter - It suits a non-ISDN equipment to the ISDN network in the ISDN subscriber network

  • Subscriber access points of the xDSL subnetwork are led out to the cable distribution box of the test network.

• NMS - Network Management System - Management terminal
  System managing the ADSL network is a terminal and an inner computer network. Managing system keeps the connection through SNMP (Simple Network Management Protocol) or WEB with the DSLAM. Management of the ADSL modem can be realized through the U interface on the service channel embedded to ADSL frames (EOC - Embedded Operational Channel). Modem vendors provide modems with a management port, too.