| 摘要 |
A mapping technique for an 8D, sixty-four state convolutionally coded 19.2 Kbit/second modem utilizes twenty-nine bits for defining all points of an 8D constellation. The 8D constellation which is mapped is comprised of a desired subset of a concatenation of four 2D constellations, where each 2D constellation has one hundred sixty points. The mapping technique generally comprises: dividing each 2D constellation into five different energy groups of thirty-two points each, the concatenation of four groups, one from each 2D constellation, comprising an 8D grouping; choosing five hundred twelve 8D groupings from the possible six hundred twenty-five (54) 8D groupings available; partitioning each group of thirty-two points into four subgroups, three of the subgroups of any particular group being ninety, one hundred eighty, and two hundred seventy degree roations of a first subgroup of the particular group; and defining each 8D point in the 8D constellation by using nine bits to choose the 8D grouping, eight bits to choose four subgroups in the 8D grouping, one for each 2D constellation, and twelve bits to choose four 2D points, one in each chosen subgroup, the four 2D points comprising the 8D point. The chosen five hundred twelve 8D groups are preferably the lowest energy 8D groupings of the six hundred twenty-five possible 8D groupings.
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