Deployment rule was identified for each given system type

Written on 3:16 AM by ooe

By design, POTS can be deployed everywhere. ISDN and ADSL have such long reaches that for the ANFP they were taken to be deployable everywhere. HDSL is very much range limited, however, and acknowledging that improves the reach of ADSL. So the deployment rules used here are: POTS, ISDN, and ADSL: deployed everywhere.

For ADSL the ‘ATU-C’ end is always in an exchange, and the ‘ATU-R’ end is always at the customer premises. This is just a statement that the wideband ADSL channel goes from exchange to customer and never the other way round; BT does not deploy reverse ADSL. As it happens a reverse ADSL system would not work in a network with normal ADSL, through catastrophic mutual interference. However, for viable normal ADSL it is important that the ANFP also forbids any other signal like a reverse ADSL system. (The other technologies discussed here are spectrally symmetrical, except for low frequency details like power feeding.)

For 2B1Q-HDSL BT's historical deployment rules are couched in terms of the ‘electrical length’ of a line, the measured insertion loss of the line at a specified frequency. This is a satisfactory measure in BT's network, which does not use bridged taps.

• 2-pair 2B1Q-HDSL: measure insertion loss at 100 kHz, deploy if IL <>

• 3-pair 2B1Q-HDSL: measure insertion loss at 100 kHz, deploy if IL <>

For SDSL, no deployment rule given beforehand. Instead SDSL was admitted into the various zones at those rates where it causes negligible extra impact.

Similarly for CAP-HDSL systems the PSD requirement was also admitted into the various zones at those rates where it causes negligible extra impact and as determined by the regulator.