Viterbi IP Core User Guide

ID 683280
Date 11/06/2017
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3.4.3.1. Soft Symbol Input

The number of soft decision bits per symbol, softbits, represent 2 softbits – 1 soft 0s and 2 softbits – 1 soft 1s. The input values represent received signal amplitudes. If the input is in log-likelihood format, a transformation is required and you must use extra softbits to retain signal integrity. The decoder marks depunctured values separately. The decoder allows a hard-decision input when softbits = 1.

Table 9.  Soft Symbol Input Representation softbits = 3
Soft Symbol Meaning
011 Strongest '0'
010 Strong '0'
001 Weak '0'
000 Weakest '0'
111 Weakest '1'
110 Weak '1'
101 Strong '1'
100 Strongest '1'