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Transport aspects 2

10.6 Superframe structure

The ITU-T G.9701 superframe structure is shown in Figure 10-28. The parameter MSF identifies the number
of TDD frames that comprise one superframe; the value of MSF depends on the number of symbols in a TDD
frame MF as defined in Table 10-14.

Additional sets of {MF, MSF} are for further study.

Table 10-14 – Mandatory sets of {MF, MSF}

MF MSF
36 8
23 12

All TDD frames of the superframe shall have the same format as defined in clause 10.5. Superframes shall
be transmitted one after another, with no gaps. The TDD frames of each superframe shall be indexed from
0 to MSF − 1.

The first TDD frame of the superframe (index 0) is called a TDD sync frame, which is followed by MSF − 1
regular TDD frames (indexed from 1 to MSF − 1). Each TDD sync frame contains a downstream sync symbol
(labelled as DS sync symbol) and an upstream sync symbol (labelled as US Sync Symbol). The first symbol of
a superframe is DRMCds – 1 symbol positions before the sync symbol. Other functions and transmission
format of upstream and downstream sync symbols are defined in clause 10.2.2.1.

Figure 10-28 – Superframe structure

The downstream sync symbol shall be transmitted immediately before the downstream RMC symbol
position, with the offset of (DRMCds -1) symbols from the start of a TDD sync frame (see Figure 10-27). The
downstream sync symbol, accordingly, has index Mds-1 in the last downstream logical frame of the previous
superframe.

The upstream sync symbol shall be transmitted on the first symbol position in the upstream part of the TDD
sync frame. The upstream sync symbol, accordingly, has index (Mus – DRMCus) in the last upstream logical
frame of the previous superframe.
The same superframe structure shall be used during both the initialization and the showtime.
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Superframes shall be counted using a modulo 2 superframe counter. The transmitter shall increment the
superframe count (CNTSF) every time it starts a new superframe. The CNTSF for upstream and downstream
shall always be the same for any particular superframe and this value shall be synchronized over all the
lines of the vectored group.

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