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Transport aspects                                              2


                       Table 9-17.1 – L2 transition indicator (L2-TRNS) command (sent by the FTU-O only)

                     Field name                 Format                            Description

            Command header              One byte: [00 aaaaaa]    aaaaaa = 1116
            L2 transition instant       One byte: [0000 aaaa]    aaaa = SFDC (see clause 13.2.1.1.5) to the transition
                                                                 into or out of the given L2 link state (Note 1)
            L2 SCCC counts              One byte [aaaa bbbb]     aaaa = new upstream SCCC count as received in an
                                                                 L2.1-Entry-Request eoc command or L2.2 Entry-
                                                                 Request eoc command
                                                                 bbbb = new downstream SCCC count as received in
                                                                 an L2.1-Entry-Request eoc command or L2.2 Entry-
                                                                 Confirm eoc response.
            NOTE 1 – For all L2 link state transitions except L2.2 exit, the L2-TRNS shall be repeated in subsequent superframes with a
            decrementing value of SFDC, until SFDC reaches the value 0. For L2.2 exit, the L2-TRNS shall be repeated in subsequent active
            superframes (see clause 13.4.2.1) with a decrementing value of SFDC, until SFDC reaches the value 0.


                         Table 9-17.2 – Reply to L2TSA request (L2TSA-R) command (sent by the FTU-O)

                     Field name                 Format                            Description

            Command header              One byte: [00 aaaaaa]    aaaaaa = 1216
            L2TSA response data         One byte: [bbbb aaaa]    aaaa = SFDC (see clause 13.2.1.4.3) to the
                                                                 implementation of a new RMC transmission
                                                                 schedule. (Note 1)
                                                                 bbbb = new L2CCC as received by the L2TSA
                                                                 request (see clause 11.2.2.5).
            NOTE 1 – The transmitter reply shall be repeated in subsequent superframes with a decrementing count until the count reaches
            the value 0.

            9.7     Acknowledgement
            The acknowledgement (ACK) shall be specified per ACK window. The ACK windows shall follow one another
            with no gaps and their duration shall be equal to the duration of one TDD-frame.
            The  time  position  of the ACK  window  shall  be  shifted  by  "ACK  window  shift"  symbol  periods  (counting
            including the quiet symbol periods falling outside of the Mds and Mus symbol periods), relative to the end of
            the last symbol position in the TDD frame in the same direction as the transmission to be acknowledged, as
            shown in Figure 9-8 for downstream acknowledgment and Figure 9-9 for upstream acknowledgment. This
            means that the ACK window shift for the downstream direction is specified relative to the end of the last
            valid  symbol  position  in  the  downstream  direction  just  before  the  upstream  RMC  symbol  carrying  the
            acknowledgements of this downstream ACK window. For the upstream direction, the ACK window shift is
            specified relative to the end of the last valid symbol position in the upstream direction just before the
            downstream RMC symbol carrying the acknowledgements of this upstream ACK window.
            Figure 9-8 shows an example for acknowledging downstream transmissions where the downstream ACK
            window shift equals two symbol periods (Figure 9-8a) and seven symbol periods (Figure 9-8b).
            Figure 9-9 shows an example for acknowledging upstream transmissions where the upstream ACK window
            shift equals one symbol period (Figure 9-9a) and ten symbol periods (Figure 9-9b).
            The valid range for ACK window shift is any integer number of symbols from 0 to 20, independent of the
            TDD frame length, subject to additional constraints (e.g., see clause 10.5.1).
            NOTE – The allowed ACK window shift value for a particular direction is limited by the maximum value for Tack (see
            clause 9.8.1). For the selected RMC symbol offsets DRMCus, DRMCds the ACK window shift values within the valid range
            also comply with the following conditions:




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