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Transport aspects                                              2


            In order to force the final state of the convolutional encoder to the zero state (0, 0, 0, 0), the two LSBs u1
            and u2 of the final two 4-dimensional elements in the symbol are constrained to u1  S1   S3, and u2  S2.

            For data symbols, the convolutional encoder state shall be terminated to (0, 0, 0, 0) only once at the end of
            the data frame (i.e., symbol). For RMC symbols, the convolutional encoder state shall be terminated to (0,
            0, 0, 0) twice: first at the end of the RMC frame, and second at the end of the user data part, i.e., at the end
            of the symbol.




































                                          Figure 10-6 – Conversion of u to v and w



















                           Figure 10-7 – Convolutional encoder: Finite state machine representation

            10.2.1.3.3   Coset partitioning and trellis diagram (informative)
            In  a  trellis  coded  modulation  system,  the  expanded  constellation  may  be  labelled  and  partitioned  into
            subsets ("cosets") using a technique called mapping by set-partitioning. The 4-dimensional cosets in Wei's
            code can each be written as the union of two Cartesian products of two 2-dimensional cosets.
            For example,  C 0     C 0    C 0      C 3    C 3  . The four constituent 2-dimensional cosets, denoted by 0,
                           4      2    2       2     2
                                      3
            1, 2 and 3 for  C 0 , C 1 , C 2 , C , respectively, are shown in Figure 10-8.
                           2  2   2   2





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