| 摘要 |
PURPOSE: A QAM constellation of a cable modem and a method for mapping a QAM symbol are provided to reduce a size of a hardware by performing a symbol mapping using one 256 QAM constellation. CONSTITUTION: A QAM constellation of a cable modem composes 256 QAM constellation by adding data of 2 bits having values of 00, 01, 11, 10 to lower 2 bits of symbols of 6 bits corresponding to 64 QAM constellation coordinate by using a gray coding method. A method for mapping a QAM symbol comprises the steps of: generating a 256 QAM constellation by adding data of 2 bits having values of 00, 01, 11, 10 to lower 2 bits of symbols of 6 bits corresponding to 64 QAM constellation coordinate; performing a symbol mapping by the 256 QAM constellation if data of 8 bits are inputted; and performing the symbol mapping by ignoring 2 bits added to predetermined locations of each symbol of a 256 QAM constellation coordinate if data of 6 bits are inputted.
|
