Transceiver training for DSL modems under TCM-ISDN interference

摘要

Transceiver training is optimized for xDSL modems operating in TCM-ISDN environments under NEXT and FEXT interference. Current ITU-T draft recommendations provide for dual bitmaps that are switched synchronized with the burst cycle of TCM-ISDN to provide a data stream having dual bit rates. These recommendations also provide for a single bitmap mode where the NEXT bit map is off. Prior to transceiver training, a modem does not know which mode has been selected. Transceiver training is optimized if the mode selection is known prior to transceiver training and the training signals are designed properly for the selected mode. To accomplish this, the mode selection is exchanged early in the modem initialization process, for example, during initial handshaking. By exchanging the mode selection earlier in the modem initialization process, the modem is able to improve transceiver training and configure properly for the type of data communication (e.g., full-duplex, half-duplex).