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Transport aspects                                              2


            Indication shall be given in the DPU-MIB parameter "initialization success/failure cause" of a failure cause
            "configuration error".

            9.8.3.4    Definition of signal-to-noise ratio margin for RMC (SNRM_RMC)
            The SNRM_RMC is the maximum increase (scalar gain, in dB) of the reference noise PSD (at all relevant
            frequencies and assuming only stationary noise is applied at the U-reference point), for which the expected
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            bit error ratio (BER) of the RMC channel does not exceed 10 , without any change of PMD parameters (e.g.,
            RMC  tone  set,  bits  and  gains)  and  PMS-TC  parameters  (e.g.,  FEC  parameters).  The  expected  BER  is
            referenced to all bits of the RMC messages at the output of the RMC channel (see Figure 9-1), assuming
            that messages received in error are not discarded.


            10      Physical media dependent (PMD) function


            10.1    PMD functional reference model
            Figure 10-1 provides an overview of a functional reference model of the PMD at the FTU-O. The bits for
            transmission on the subscriber line are received across the  interface from the PMS-TC in the format of
            data frames; similarly, the data bits received from the data symbol decoder of the PMD are also transferred
            to the PMS-TC across the  interface in the same format. The content of a single data frame is loaded onto
            one symbol.
            Two types of data frames are exchanged via  interface: a normal data frame, carrying bits of DTU(s) only
            and  an  RMC  data  frame,  carrying  both  RMC  bits  and  bits  of  DTU(s).  The  bits  of  RMC  and  DTU(s)  are
            multiplexed in the RMC frame as defined in clause 9.5. For each logical frame, only one RMC data frame is
            allowed. All other data frames are normal data frames. The number of bits in an RMC data frame and in a
            normal data frame may be different.

            The data symbol encoder (see clause 10.2) divides the incoming data frame into groups of bits, where each
            group is assigned to modulate a specific subcarrier of the DMT signal. Each group is further encoded by the
            trellis encoder and mapped to a point in a signal constellation. Similarly, bits of the initialization symbols,
            sync  symbols  or  pilot  symbols,  whichever  need  to  be  transmitted,  are  encoded  and  mapped  onto  a
            corresponding  point  in  the  signal  constellation.  The  RMC  symbols  and  data  symbols  have  different  bit
            loading and trellis encoding rules, which are defined in clause 10.2. The data symbol encoder applies these
            rules accordingly.
            Constellation points of the transmitted symbol, Zi, are further precoded (per subcarrier) by combining with
            constellation points of symbols transmitted over other (n-1) lines of the vectored group (see clause 10.3)
            submitted  via  the  ε(k,n)  interface  (where  k  is  the  index  of  the  line  in  the  vectored  group).  Precoding
            coefficients are provided by the VCE via ε-c interface (see Figure 10-16).
            The set of precoded constellation points modulates the subcarriers of the symbol using an inverse discrete
            Fourier  transform  (IDFT)  as  defined  in  clause  10.4.  After  the  IDFT,  cyclic  extension  and  windowing,  the
            symbol  is  sent  to  the  transmission  medium  (line)  over  the  U-O  interface  at  the  time  in  the  TDD  frame
            assigned for downstream transmission (controlled by the TDD switch).






















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