Page 738 - 5G Basics - Core Network Aspects

2 Transport aspects

Figure 9-3 – Multiplexing of RMC frame and DTUs into data frames

At every symbol position on which the PMD sets the Tx Data Req primitive, the data frame MUX shall
generate one data frame and transfer it over the δ interface. The PMD may decide to not set Tx Data Req at
symbol positions, as explained in clause 9.1.1. At these symbol positions, no data frame shall be generated.
The content of the data frame depends on the symbol position inside the logical frame. The first symbol
position of the logical frame shall be indicated by the Tx RMC primitive (RMC symbol position). Afterwards,
the symbol position index shall be incremented each time the Tx Clock primitive is received until the end of
the logical frame.
At the RMC symbol position (symbol index zero), the generated data frame shall be an RMC data frame.
The RMC data frame shall contain an RMC frame of BRMC bytes followed by BDR bytes extracted from the
DTU buffer. The total number of bytes in an RMC data frame is BR = (BDR + BRMC). Figure 9-3 shows
multiplexing of an RMC frame and bytes of DTUs into data frames. The first byte extracted from the DTU
buffer of the first RMC data frame after transition into showtime shall be the first byte of a DTU (i.e., the
first byte of the first DTU to be transmitted).
At data symbol positions with indices other than zero in a logical frame, the generated data frame shall be a
normal data frame. A normal data frame shall contain BD bytes, extracted from the DTU buffer. The value of
BD may be different for symbol positions of the normal operation interval (NOI) and symbol positions of the
discontinuous operation interval (DOI). The value of BD in the NOI is denoted BDN and the value of BD in the
DOI is denoted BDD.
The RMC bytes shall be loaded in the order determined by the RMC frame format, defined in clause 9.6.1.
The DTU bytes shall be loaded into the data frame in the order determined by the DTU format, defined in
clause 8.3.1.
If the current normal data frame and all subsequent normal data frames to be generated until the end of
the logical frame consist only of dummy DTUs or split dummy DTUs, the data frame disabled primitive may
be set upon transferring a normal data frame over the  interface. The data frame disabled primitive shall
be set at all symbol positions where quiet symbols or idle symbols have to be transmitted. Therefore, the
PMS-TC shall guarantee that all DTUs or split DTUs in the data frames mapped to quiet and idle symbols are
dummy DTUs or fractions thereof.
Figure 9-4 provides an example of downstream data frame generation during NOI, DOI and during sync
symbol and shows time alignment between DTUs, RMC frame and corresponding symbols for the case
where Mds=17, Mus=5, TTRds=6, TAds=3, TIQds=1, B'=6, B=5, and TBUDGETds=12 (see Table 10-1).

Shown in Figure 9-4 is a full downstream logical frame having frame count k with the mentioned
configuration parameters. Also shown in Figure 9-4 are the end portion of the previous logical frame with
count k-1 and the beginning portion of the subsequent logical frame with count k+1. In the computation of
the byte position NB(k+1), i.e., the count of the first byte of the first DTU in the logical frame k+1, bytes of

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