Viterbi IP Core User Guide

ID 683280
Date 11/06/2017
Document Table of Contents Node Synchronization

If you are not using external synchronization, you may not know the order of your N bits. The node synchronization option allows you to rotate the rr inputs until the decoder is in synchronization. To use node synchronization, you observe the BER and keep changing state_node_sync to rotate the rr inputs until you get the correct value for the BER.
Figure 15. Node Synchronization Block Diagram

The following equation represents node synchronization:

RR[i] = rr[((state_node_sync + i – 1) mod N) + 1]

where i is 1 to N.

RR and rr are treated as an array of width N of busses softbits wide. The range of valid values for state_node_sync is 0 to (N – 1).