High speed modem systems incorporating distribution preserving tomlinson

Abstract

Apparatus and methods in both modem transmitters and receivers are provided for accommodating secondary channel data without disturbing the trellis encoding, mapping, and Viterbi decoding of primary channel data, and without disturbing distribution preserving Tomlinson precoding and decoding of the primary channel data. In order to accommodate the secondary channel data, the secondary channel data are used to make quadrant decisions in a mapper, and concurrently therewith, dummy data or tertiary channel data corresponding in time with the secondary channel data are provided to the trellis encoder so that the continuous working of the trellis encoder can be maintained. In order to guarantee proper working of the trellis encoder, and to guarantee reliability of the secondary channel data, the secondary channel constellation points within a quadrant are clustered together and far from the quadrant boundaries, the selected points in each quadrant are the rotations of selected points in the other quadrants, and the points include a single point from each two-dimensional partition element of the 2 D grid in each quadrant. With primary, secondary, and tertiary data encoded in this manner, the encoded data are precoded according to Tomlinson precoding or according to any of several disclosed distribution preserving Tomlinson techniques. Decoding is dictated by the manner in which the primary and secondary data were encoded and precoded.