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ADSL is designed to carry a digital signal, over a copper pair, above the voice frequency band (20 KHz–1.1 MHz) to enable high speed internet service over a standard POTS line. This allows “always on” internet access while simultaneously providing voice service. Typical POTS line quality will normally support ADSL, but the DSL service must be tested when trouble strikes. To troubleshoot DSL service, a modem emulation test set, such as the HST-3000, is needed. The DSLAM and network configuration is verified by connecting at the main distribution frame (MDF) where known interference and attenuation are minimal, as shown in Figure 1. The physical (ADSL) layer data rates and noise margins are reviewed to confirm that they match the service contract. Validate correct DSLAM and BRAS provisioning by connecting to the customer line and authenticating with the network through the DSLAM.
The HST-3000 ADSL testing features use modem emulation (ATU-R Annex A or Annex B) to turn up and troubleshoot ADSL and ADSL2 services as well as provide ATM statistics and analysis. The internet protocol (IP) suite software allows IP/PPP troubleshooting. The on-board web browser option validates an internet connection. The capabilities of the ADSL features include the following:
- Variety of ADSL testing modes for service verification, local loop testing, and network connectivity:
| Mode |
Function |
| ADSL Modem emulate mode |
Used to test basic ADSL physical layer rates, quality and line statistics.
Also used for testing the following types of lines: IP over Ethernet, IP over ATM, PPP over Ethernet, and PPP over ATM. |
| ADSL Through mode |
Used for testing the following types of lines: Bridged Ethernet, IP over ATM, PPP over Ethernet, and PPP over ATM. |
| ATM Loopback |
Used to loopback ATM cells. |
| Ethernet TE mode |
Used for testing IP over Ethernet and PPP over Ethernet. |
- Variety of line modulations:
- ANSI T1.413 DMT Full Rate
- ITU-T G.992.2 (G.lite)
- ITU-T G.992.1 (G.DMT) Full Rate Annex A
- Multimode (Annex A)
- ITU-T 992.3 (ADSL2)
- Wide range of compatibility with industry standards
- On-board web browser for validating the customer’s internet connection
- Trace route and FTP throughput capability
- Customer premise equipment emulation to turn up and troubleshoot ADSL service, including Ethernet terminal equipment (TE)
- ATM F5 loopback capability
- ATM BERT capability
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