it the number 0 (for zero total errors with this selection). We repeat this for node 1 (time 2), node 2 (time 2) and node 3 (time 2); the results are shown in Figure 7.10 (b). Channel Coding and Decoding: Part 2-Convolutional Coding and Decoding node 1 V = ( 00 difference: O Total O + O = O time 0 time 1 time 2 Best parent: node O node O node O O lowest total node 1 difference: 2 Total 1 + 2 = 3 time 2 lowest total 1 Best parent lowest total node 2 Best parent lowest total node 3 Best parent Figure 7.10 (a) best parent for node 0 (time 2) (b) best parent for nodes 1, 2, 3 (time 2) We continue this process until we have run through the trellis for the length of time corresponding to the length of V. In our case, since V consists only of two sets of 2 bits (v = (00 00)), we are done after two times. At the end, we have four end nodes with four numbers. For example, end node 0 (time 2) comes with value 0, while end node 2 (time 2) comes with the value 1. We choose the end node with the smallest value. In our example, looking at Figure 7.10, we choose the end node 0. Chapter Seven From here, we know the history of parent nodes, SO we can "backtrack" through the trellis, and determine the u' and the m'. And we're done. In our case, we choose node 0 (time 2) with a final value of 0, and we "backtrack" as shown in Figure 7.11. This leads us to the output m' = (00). Now you know just how the channel decoder works to undo the effects of channel coding, and along the way correct bit errors. 4th item start your to read reading here time O time 1 time 2 Follow line Best parent = back to node O node O Best parent Follow path back is node O to node O= best parent node 1 to 4, you have path through trellis. This path tells you u' =(0000) and m' =(00) Figure 7.11 Explaining "backtracking" through trellis to get output Example 7.3 Use the Viterbi Algorithm to determine the output of a convolutional decoder, given the input bits to the decoder are V = (11 11) and the convolutional coder is described by the trellis diagram in Figur