Viterbi IP Core User Guide

ID 683280
Date 11/06/2017
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3.3.2. Trellis Decoder

The decoder processes an arriving symbol to obtain four branch metric values and a sector number. The branch metrics enter the Viterbi decoder in trellis mode and it obtains the encoded bit.
The encoder re-encodes this bit stream and the decoder uses the output of this encoder with the sector number information to retrieve the uncoded bit. The testbench implements all the logic. The wizard generates the branch metric values and sector number values, so you need no logic to create these values. The testbench reads the sector number when it needs it. It has no delay functionality nor rotation. The wizard-created data introduces has no phase error so the phase is aligned. In a real system, you must calculate the phase. For a TCM code the BER block does not produce a meaningful output (numerr), because the BER block does not compute errors at the input for TCM codes.
Figure 11. Implementation of the Viterbi Decoder as a Trellis Decoder