One of ADSL's most important and essential features is the bit-swapping described in . Bit swapping accomplishes several features either crucial or desirable for DSL operation by:
Allowing continuous response to line changes caused by environmental effects.
Responding to changing crosstalk situations as other DSLs energize or deenergize.
Allowing the data rate to be changed when/if desirable in some applications without restart.
Allowing multiple DSL lines to be mutually compatible within power-spectral-density constraints.
Enabling features such as the SRA described earlier.
The first two features are essential to proper operation of the DSL modem. DMT modems use minimal equalization, which ...