Digital transmission apparatus using differential coding and forward error correction

摘要

A digital transmission apparatus is provided, by which the amount of transmission delay and circuit miniaturization can be realized in the case of using an FEC method together with a differential coding method. In the digital transmission apparatus, a digital signal to be transmitted is serial-to-parallel-converted into parallel n-channel signals; each signal is FEC-encoded and encoded signals are then differentially encoded; and a carrier is modulated by the parallel n-channel differentially-encoded signals to be transmitted as a 2<n> multi-level modulated signal. The signal is detected at the receiving side and parallel n-channel demodulated and decoded signals are output; FEC decoding is performed; and the parallel n-channel digital signals after FEC decoding is parallel-to-serial-converted. When block coding is used as an FEC method, parallel n-channel digital signals to be transmitted are respectively processed by block-encoding of the same logic; the parallel n-channel signals after encoding are differentially encoded; and a carrier is modulated by the parallel n-channel differentially-encoded signals to be transmitted as a 2<n> multi-level modulated signal. At the receiving side, parallel n-channel signals after detection are stored; syndrome data for detecting an error bit position for each signal is calculated; and based on the syndrome data, time-series detection of each error bit position is performed so as to correct the errors included in the stored signals. <IMAGE>