Keeping the previous definitions for state transitions (i.e., solid line corresponds to an input bit
0 and a dashed line corresponds to an input 1) we can outline the path corresponding to the input
sequence of 11011 and this is shown in Fig. 5.30.
a 50,06, b 51,06, c 50,16, d 51,16.
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FIGURE 5.27 State diagram representation
of the convolutional encoder.
Note each state has a valid transition to certain states, this behavior is controlled by the polynomials
used in the encoder. For this particular example, after K input bit durations each state can be
entered from only two other states transitions.
Viterbi Algorithm (VA). We now turn our attention to the decoding operations for convolutional
codes. Specifically we will discuss an implementation of an ML decoder, commonly referred to as
the Viterbi Algorithm [12, 13]. We chose the ML decoder in order to achieve the minimum probability
PERFORMANCE IMPROVEMENT TECHNIQUES 245
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FIGURE 5.
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