| 摘要 |
PURPOSE: A symbol demapping device of a cable modem termination system is provided to apply all three methods of I-Q demappings such as a QPSK(quadrature phase shift keying) method, a 16QAM(quadrature amplitude modulation) gray-coded method, a 16QAM differential-coded method by equipping one 16QAM symbol demapper. CONSTITUTION: A 16QAM gray-coded symbol demapper or a 16QAM differential-coded symbol demapper is outputs data of four bit by I-Q demapping with a 16QAM gray-coded method or a 16QAM differential-coded method. A distinguishing unit of symbol distinguishes if an input symbol is a symbol to be demapped to data that differs each other in the 16QAM gray-coded method and the 16QAM differential-coded method by using data of four bits. The converting unit of data outputs the data of four bits or outputs a position of the data of lower two bits according to a control signal to direct one of the 16QAM gray-coded method, the 16QAM differential-coded method and the distinguished result of the symbol distinguishing unit. Because three methods of symbol demapping are applied all by equipping one 16QAM gray-coded demapper or the 16QAM differential-coded demapper, it is very effective in a hardware.
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