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Perform Fixed-Point Soft Decision Viterbi Decoding

Use the Viterbi Decoder block for fixed-point soft-decision convolutional decoding.

The model uses the PreLoadFcn Callback to specify an ${E_b}/{N_0}$ setting of 4 dB for the AWGN Channel block, and to limit the run duration to 100 errors or 1e6 bits for the Error Rate Calculation block.

A Quantizer subsystem (containing Gain (Simulink), Scalar Quantizer Encoder, and Data Type Conversion (Simulink) blocks) quantizes the signal and casts the output data type to fixdt(0,3,0). The signal input to the Viterbi Decoder block is ufix3.

The Viterbi Decoder block has the Decision type parameter set to Soft decision and Number of soft decision bits set to 3, and on the Data Types tab, the State metric word length is set to 6 and the Output data type is set to boolean. The bit error rate is displayed and captured to the BER workspace variable.

The computed bit error rate is 0.00002.
The total number of errors is 18.
The total number of bits processed is 1000044.