| 摘要 |
<p>A hierarchical QAM system allows the transmission of different sources by embedding the relative constellation points. A QAM transmitting system, includes a source of a level (1) and a level (2) data stream, each data stream carrying successive symbols. A hierarchical QAM transmitter, coupled to the level (1) and level (2) data stream source, generates a hierarchical QAM signal in which a level (1) symbol is represented by a data point in one of four quadrants in the I Q plane, and a level (2) symbol is represented by the data point in one of four sub quadrants surrounding a center point of the quadrant containing the level (1) data point. The level (2) data point is spaced away from the center point by a grouping factor set to more closely match the bit error rate performance of the level (1) and level (2) data streams.</p> |
