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2                                                 Transport aspects




                                  Table 9-8 – Upstream RMC command (sent by FTU-R only)

                   Field name               Format                             Description
             Retransmission ACK bit-  Six bytes             ACK bitmap [b47 ...b0], the bit b0 relates to the last
             map                    byte 0: [b7 ... b0]     transmitted DTU(s) in the ACK window (see clause 9.7).
                                    byte 1: [b15... b8]     Any given bit of the ACK bitmap shall be set to 1 for ACK
                                    byte 2: [b23 ... b16]   and 0 for NACK.
                                    byte 3: [b31 ... b24]
                                    byte 4: [b39 ... b32]
                                    byte 5: [b47 ... b40]
             Retransmission ACK     One byte:               aa = ACK group size (Gack) represented as an unsigned
             group size, RMC ACK,   [dddd aabc]             integer with valid values 1, 2, 3.
             TIGA ACK and indicator                         b = acknowledgement of the RMC message; shall be set to
             bits                                           1 for ACK and 0 for NACK.
                                                            c = positive acknowledgement of reception of an OLR
                                                            request type 3 (TIGA) eoc command (TIGA-ACK).
                                                            c=1 indicates that a transmitter-initiated gain adjustment
                                                            (TIGA) command was received and positively
                                                            acknowledged.
                                                            c=0 indicates that no TIGA command was received and
                                                            positively acknowledged.
                                                            The generation and use of this bit is specified in
                                                            clause 13.2.2.1.
                                                            dddd = indicator bits according to the following order:
                                                            [lpr los lom lor].
                                                            An indicator bit shall be set to 0 if the corresponding
                                                            primitive/defect occurs and set to 1 otherwise (active
                                                            low).
             Upstream logical frame   Three bytes           Configuration parameters to be used for the current
             configuration                                  logical frame or for the following frame, depending on the
                                                            value of MB upstream (see clause 10.7 and Table 12-41)
                                                            The format of logical frame configuration parameters is
                                                            specified in Table 9-9.
             Expected transmission   One byte: [000 aaaaa]   aaaaa = expected transmission time expressed in symbols
             time (ETT)                                     for the current logical frame, specified as the symbol
                                                            position index of the last data symbol expected to be
                                                            transmitted in the logical frame. The actual transmission
                                                            time shall be less than or equal to the value
                                                            communicated (Note 1).
             DTU sync value (NB)    Two bytes:              The value of NB, for the current logical frame (see
                                    byte  0 [s7 ... s0]     definition of NB in clause 9.5) expressed in bytes:
                                    byte  1 [0000 s11... s8]   The value is coded as a 12 bit unsigned integer [s11 ... s0]
                                                            with s0 the LSB.
                                                            The valid range for the DTU sync value is 00016 to FFF16.

















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