2 Digital subscriber line VDSL2
2.9 Division of the frequency band

The situation is for VDSL2 connections a little bit complicated. VDSL2 connection must enable it to provide services that require both asymmetric and symmetric data transfers. For this reason, it is necessary to frequency sub bands further divided into smaller parts, and these parts rotate together sequentially so as to obtain the desired rate of data transfer in both directions, taking into account the increasing path loss. Rotation method and width of the individual frequency sub bands determined by the so-called as frequency plan. The sub bands for the downlink transmission direction (downstream) are identified and numbered as: D1, D2, D3, D4. The sub bands for uplink transmission (upstream) are marked and numbered as: US0, US1, US2, US3, US4.

There are two main frequency plans for VDSL2 connection, which are based on plans for the VDSL connection. Plan known as the 998 is suitable for data transmissions with asymmetric transmission speeds. Plan, known as the 997 is suitable for services that require symmetrical data transfers.

Figure illustrates how to use the frequency band at ADSL2+ over ISDN connections and VDSL2 operating with frequency plan 998ADE17.