| 摘要 |
PROBLEM TO BE SOLVED: To provide a stable transmission system of a large margin to noises by using a telephone line as a transmission line, transmitting data through a modulate signal, for which quadrature amplitude modulation is respectively performed to plural frequency modulated carrier waves, and providing a means for minimizing the delay of data transmission by optimizing the capacity of line transmission. SOLUTION: A received signal is demodulated by a demodulator 210 of DMT modulation, a reference signal generated by a reference generating circuit 220 is subtracted, and the received signal becomes the ERROR signal of a noise component for each carrier. An S/N measuring instrument 230 calculates the S/N of each carrier from the ERROR signal and a transmission bit number converter 240 converts this S/N to the number of bits to be allocated by the S/N value of each carrier. At such a time, the converter 240 prepares a bit map so as to minimize a prescribed expression in order to minimize the number of dummy bits. Thus, conversion delay time caused by dummy bits is minimized and the amount of transmission delay can be suppressed.
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