Trellis shaping for modulation systems

A method of mapping a digital data sequence into a sequence of signal points for transmission, said sequence of signal points belonging to a set of possible sequences of signal points, comprising

• specifying a class of possible sequences based on said digital data,
• selecting said signal point sequence from said class, said selection being based on the respective average powers of said possible sequences of said class, said selection being based not only on a fixed-length block of said digital data, but also on other digital data.

A method of mapping a digital data sequence into a sequence of signal points to be sent, comprising

• determining a class of possible sequences from which to select said sequence to be sent, based at least on digital data appearing in said digital data sequence up to a time j, and
• for every time j, selecting said sequence to be sent from said class of possible sequences based on digital data appearing in said sequence after time j.

Apparatus for mapping a digital data sequence into a signal point sequence for transmission, comprising

• means for receiving said digital data sequence, and
• a sequence selector for selecting said signal point sequence from a subset of all possible signal point sequences based on said digital data sequence, all said possible signal point sequences in said subset lie in a fundamental region of a trellis code, said fundamental region being other than a simple Cartesian product of finite-dimensional regions.

Apparatus for mapping a digital data sequence into a signal point sequence for data transmission, comprising

• means for specifying a class of possible signal point sequences based on said digital data sequence, and
• means for selecting said signal point sequence from said class based on the respective average powers of said possible sequences of said class and based on not only a fixed-length block of the digital data.