Asymmetric trellis coded modulation (ATCM)

Presents a method for designing trellis coded modulation with asymmetric trellis wherein the transitions have non-uniform number of parallel paths. In the design the encoding data is firstly mapped to an asymmetric trellis by using a prefix code; then the trellis is mapped to a 2N-dimensional constellation. In the paper a gradient based search is developed to design the mapping from the asymmetric trellis to the constellation by maximizing free distance to average power ratio subject to a given discrimination rate. Such search technique can reduce the nonlinear design to a simple optimization problem. A number of good asymmetric trellis coded modulation codes using APK and PSK are obtained and tabulated