Broadband Access: Wireline and Wireless - Alternatives for Internet Services

10DSL Standards

10.1 Spectrum Management – ANSIT1.417

ANSI standard T1.417 (now known as ATIS-0600417.2003) was originally published in 2001, specifying spectrum management guidelines for DSL transmission on telephone lines. This standard was developed by standards working group T1E1.4. Since that time, several national bodies have also established limits for the spectrum and power of transmitted DSL signals.

The signals transmitted by a DSL modem on one pair of wires can interfere with the transmission of another DSL using a different pair of wires in the same cable due to the crosstalk between the wire pairs. For the discussion of spectrum management, the signals from the disturber DSL modem are coupled from the disturber wire pair to the victim wire pair and then interfere with the reception at the victim DSL modem. As discussed in Section 7.4.7.1, the degree of crosstalk increases as the transmitted power and frequency of the disturbing transmitted increases. As is also described in that section, crosstalk is a two-way process, so each DSL modem is simultaneously a disturber and a victim with respect to the other line.

The purpose of the T1.417 DSL spectrum management standard is to set a limit on the interference produced by DSL modem crosstalk. T1.417 accomplishes this by limiting the allowable transmitted signal amplitude (in dBm/Hz) and maximum frequency as a function of the length of the line. T1.417 permits transmission at higher frequencies on shorter lines because ...