Ericsson MINI-LINK TN R3 ETSI, Technical Description

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Radio Terminals
4.2.2.2 Radio Frame Multiplexer
The Radio Frame Multiplexer handles multiplexing of different data types into
one data stream, scrambling and FEC encoding.
In a protected system, the block interfaces the BPI bus, see Section 4.6.2
on page 81.
The following data types are multiplexed into the composite data stream to
be transmitted over the radio path:
• Traffic
• Data Communication Channel (DCC)
• Hop Communication Channel (HCC)
Traffic
The transmit traffic data is first sent to the multiplexer to assure data rate
adaptation (stuffing). If no valid data is present at the input, an AIS signal is
inserted at nominal data rate. This means that the data traffic across the hop
(only for PDH) is replaced with ones (1).
DCC
DCC comprises nx64 kbit/s channels used for DCN communication over the
hop, where 2
≤
n
≤
9 depending on traffic capacity and modulation.
HCC
The Hop Communication Channel (HCC) is used for the exchange of control
and supervision information between near-end and far-end MMUs.
Multiplexing
The three different data types together with check bits and frame lock bits are
sent in a composite data format defined by the frame format that is loaded into
a Frame Format RAM. The 12 frame alignment signal bits are placed at the
beginning of the frame. Stuffing bits are inserted into the composite frame.
Scrambling and FEC Encoding
The synchronous scrambler has a length of 2
17
–1 and is synchronized each
eighth frame (super frame). For C-QPSK, the FEC bits are inserted according
to the frame format and calculated using an interleaving scheme. Reed
Solomon coding is used for 16 QAM.
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