| 摘要 |
PURPOSE:To simply encipher the transmission data and to secure its confidentiality by enciphering bit number information of every carrier and informing it to a training signal transmitting side, and also, decoding the enciphered bit number information which is demodulated and setting it to a modulating means. CONSTITUTION:Multi-carrier MODEMs 10-1, 10-2 are connected to a public telephone circuit 12. In a modulating part 14, plural carriers are provided in a transmission band, and transmitting data SD are modulated simultaneously and sent out to a transmission circuit 12. A demodulating part 16 demodulates bit data of every carrier and outputs it as receiving data RD. An assignment deciding part 18 determines the number of transmission bits of every carrier, based on a demodulation output from a demodulating part 16 at the time when a training signal sent first from a transmitting side is received. An output of the deciding part 18 is supplied to an enciphering part 20 and enciphered, and informed to a training signal transmitting side from the modulating part 14. Simultaneously, the information enciphered and sent from the opposite party side is decoded. |
