Improvements in, or relating to, multi-carrier transmission systems

(57) The newest multiplex carrier transmission system that transmits several bits per one subcarrier and sign has the strong request to synchronization of a receiver and a transmitter using a rectangular subcarrier with summary high rank QAM arrangement. The maximum permissible deviation from exact synchronization is several / of sampling interval / 1/ usually. The reserved subcarrier to which the fixed phase is given, i. E. , a pilot subcarrier, is used as a standard for usually attaining highly precise synchronization. The phase lock of the receiver sampling-clocks oscillator is carried out to the pilot subcarrier. Therefore, it is required to presume 依相 of a pilot subcarrier. In order to reproduce a pilot subcarrier regardless of the frame structure of a DMT signal, even if it uses a band pass filter, influence on the pilot subcarrier by the next subcarrier is not blot out.