Sixteen-State Forward Convolutional Encoder
Original Publication Date: 1985-Nov-01
Included in the Prior Art Database: 2005-Feb-19
A preference has been established for trellis-coded modulation for use in data modems which transmit data at a rate of 9,600 bits/s. over the Public Switched Networks, and those which transmit data at a rate higher than 9,600 bits/s. over leased voice-grade telephone lines. This article describes a 16-state forward convolutional encoder which is insensitive to 90Œ phase jumps of the carrier, thus allowing carrier phase to relock in any one of four phase positions after a temporary loss of carrier phase synchronization. Fig. 1 illustrates a forward encoder for trellis-coded modulation that transforms six parallel information bits (In,1-In,6) into sequences of seven parallel bits (Yn,0-Yn,6) which are then mapped into complex channel signals of the 128-state signal constellation shown in Fig. 2.