MULTIMODE MODULATION AND CODING OF QAM

A general-purpose modulation and coding implementation is described ba sed on the QAM family of modulation. The technique utilizes the ''supe rposed'' property of certain rectangular QAM constellations, along wit h the fact that optimal four-state trellis codes for such constellatio ns are essentially identical, to provide a single modem architecture c apable of performing over a wide range of power and bandwidth efficien t transmission using either uncoded or coded modulation scheme. While the specific modulation and coding techniques are not new, we believe that their intrinsic compatibility is not well known and provides attr active system flexibility.