Analysis and design of rotationally invariant trellis codes
Chien-Cheng Tung, J.N. Livingston · 2002
Describes a method for transforming a given trellis code into a rotationally invariant code with little of no loss in performance. The method uses the state transition matrix and the rotational symmetries of the constellation to accomplish this. We demonstrate it by transforming the 8-state Ungerboeck code to a 90/spl deg/ rotationally invariant code with the same free Euclidean distance. >