Block coding capacity of high bit rate digital subscriber lines by the structured channel signaling technique

Self near-end crosstalk (NEXT) is assumed to be the dominant source of impairment, and the subscriber loop configuration is governed by carrier serving area (CSA) design rules. The structured channel signaling (SCS) technique decomposes the physical channel into multiple parallel independent signaling subchannels by exploiting the combined eigenstructure of the channel and the correlation of the (NEXT) interference. Computer performance evaluation studies reveal two distinct patterns. For a given loop configuration, as the block length increases, the coding gain usually increases, and for a fixed block code length, the coding gain degrades as the loop length (including bridged taps) increases. For loops at the extreme range of a CSA, block codes of at least 20 symbols are required to achieve a performance commensurate with that of a decision feedback equalizer (DFE) composed of an optimal nine-tap minimum mean-square error (MMSE) feedforward filter and an ideal feedback canceler