| 摘要 |
An apparatus and method using the forward error correction setting to enable simultaneous use of multiple modulation systems on terrestrial distribution networks including cable television systems is described. The system includes a transcoder having a demultiplexer for demultiplexing a forward-error-correction decoded signal into a main data stream with a bit rate suitable for 64-QAM cable transmission and an auxiliary data stream with a bit rate approximately half that of the main data stream. Two of such auxiliary data streams can be combined to generate an output data stream with a bit rate suitable for 64-QAM cable transmission. The system also includes a satellite transmitter which can adjust its convolution coding rate to either +E,fra 1/2+EE or +E,fra 3/4+EE for 64-QAM and 256-QAM cable channels respectively. |
