INTERVAL SYNCHRONIZATION OF TIME-VARIANT TRELLIS-CODED 8 4-PSK BY CALCULATING 2 DIFFERENT 4TH-ORDER COMPLEX MOMENTS OF THE RECEIVE SIGNAL/

In this contribution a method for block synchronisation of time varian t trellis coded 8/4-PSK signal sequences without using additional info rmation is presented. The block structure of the coded signal is the r esult of using the 4- and the 8-PSK modulation alphabets in an alterna ting way. The different modulation alphabets correspond to different t rellis segments which are compounded to the resulting block-trellis di agram. The Viterbi detector needs the correct information to which tre llis segment the current receive signal belongs. It is shown that the block synchronisation can be performed by calculating two complex four th order moments of the receive signal. Simulations of a simple synchr onisation circuit show that a word length of ten bit of the A/D-conver ter at the receive side is sufficient to reach a synchronisation error rate which is more than ten times lower than the symbol error rate of the best known C-8/4-PSK code.