System and method for improving trellis decoding in communications systems with finite constellation boundaries. A preferred embodiment for a received point of a tone when the tone represents a number of bits greater than three comprises determining if a received point lies outside of a specified region, wherein the specified region is dependent upon the number of bits, and transforming the received point if the received point lies outside of the specified region. The transformation moves the received point onto a boundary of the specified region, which can help in the correct decoding of the received point.