Abstract: A portion of signal points that appear at predetermined positions in a signal point stream and that benefit less from a particular form of error immunity—e.g., conversion gain—are transmitted in such a way that their robustness against errors is at least as great as that of the signal points that benefit more therefrom. In preferred packet transmission embodiments of the invention, the ending signal points of a packet are transmitted using a signal point constellation that has fewer signal points than the constellation that is used for the other signal points in the packet.