SIGNAL TRANSMITTER, SIGNAL RECEIVER, AND SIGNAL TRANSMITTING-RECEIVING METHOD

摘要

A signal transmitter, a signal receiver, and a signal transmitting-receiving method which are used for, for example, digital television broadcasting and by which television pictures and sounds of high quality can be transmitted when the signal level is high on the receiving side and those of somewhat high quality even when the signal level is low. The signal transmitter (10) divides the information sequence into a plurality of input signals in accordance with the respective importances of the data contained in the information, encodes the input signals at different encoding rates, multiplexes the signals together to time slots for transmission, modulates the signals by a different multilevel modulating method for every time slot corresponding to the encoded signals and transmits the modulated signals to a signal receiver (30) through a communication transmission line (20) such as a satellite communication channel. The receiver (30) demodulates, separates, and decodes the encoded signals from the modulated signals received through the line (20) by a different demodulating method for every time slot corresponding to the encoded signals contained in the received signals.