Abstract: It is an object of the present invention to provide a multicarrier transmission system for enabling degradation of a transmission speed in an adjacent line adjacent to a communication line, to be avoided. For this purpose, a multicarrier transmission system in the present invention is a multicarrier transmission system configured so that a first communication device and a second communication device are connected via a communication line, wherein the first communication device controls a transmission output of a signal to be outputted to the above described communication line, based on a difference between a transmission distance of the above described communication line and a transmission distance of an adjacent line adjacent to the above described communication line.

Abstract: The present invention provides a communication system that can suppress the crosstalk of a communication device installed in a remote terminal. The communication system according to the invention is the communication system configured so that a first communication device (401) and a second communication device (202) are connected via a communication line (500), wherein the first communication device (401) is installed in a remote terminal (400) that exists between a center office (100) and a subscriber house (200). And the first communication device (401) controls a transmission output of an xDSL which is used on a communication line (500) based on the frequency characteristic of attenuation amount in a center office line (600) between the center office (100) and the remote terminal (400).

Abstract: It is an object of the present invention to provide a multicarrier transmission system for enabling degradation of a transmission speed in an adjacent line adjacent to a communication line, to be avoided. For this purpose, a multicarrier transmission system in the present invention is a multicarrier transmission system configured so that a first communication device and a second communication device are connected via a communication line, wherein the first communication device controls a transmission output of a signal to be outputted to the above described communication line, based on a difference between a transmission distance of the above described communication line and a transmission distance of an adjacent line adjacent to the above described communication line.

Abstract: In a condition where periodically varying noise is generated, multi-carrier transmission is efficiently performed. On a central office (XTU-C), a tone of tone generating portion is transmitted with controlling level by a clock synchronized with a noise. On a terminal (XTU-R), a clock period is detected by a clock detector. A pseudo random signal (including all carriers) is transmitted from a pseudo random signal generating portion on the side of central office. On the side of terminal, an SNR of carriers per previously detected clock period (noise period) is measured by an SNR measuring portion. According to a result of measurement, power/bit distribution of each carrier is derived by a power/bit distribution calculating portion to store as a demapping information upon down carrier transmission. Also, the power/bit distribution is also transmitted to central office to be stored in a mapping portion of the central office. By this, down transmission is performed.