| 摘要 |
PURPOSE: To more efficiently use the available frequency band of a channel by determining the best transmission band and the highest bit transmission speed for a modem based on characteristics measured off-line of the channel to which the modem is connected. CONSTITUTION: The modem includes a receiver which receives a modulated signal and a line check signal sent from a remote device through the channel and can receive the modulated signal with one of plural frequency bands, a line check processor which measures characteristics of the channel based on the received line check signal, and a selector which selects one of plural frequency bands based on measured channel characteristics to use it for reception of the modulated signal from the remote device. Frequency responses and/or S/N of the channel which are measured with two or more frequencies are included in these measured characteristics. This receiver includes an adaptive filter to obtain a desired synthesized impulse response on the channel, and at least some of measured characteristics are dependent upon this adaptive filter. |
