Radio Terminals
Descrambling and FEC Decoding
For C-QPSK, error correction is accomplished using FEC parity bits in
combination with a data quality measurement from the Demodulator. A Reed
Solomon decoder is used for QAM modulation.
The descrambler transforms the signal to its original state enabling the
Demultiplexer to properly distribute the received information to its destinations.
Demultiplexing
Demultiplexing is performed according to the frame format used. The
Demultiplexer generates a frame fault alarm if frame synchronization is lost.
The number of errored bits in the traffic data stream is measured using parity
bits. These are used for BER detection and performance monitoring. Stuffing
control bits are processed for the traffic and service channels.
Traffic
On the receiving side the following is performed to the traffic data:
• AIS insertion (at signal loss or BER≤10
-3
)
• AIS detection
• Elastic buffering and clock recovery
• Data alignment compensation and measurement (to enable hitless
switching)
• Hitless switching (for 1+1 protection)
DCC
On the receiving side, elastic buffering and clock recovery is performed on
the DCC.
HCC
The Hop Communication Channel (HCC) is used for the exchange of control
and supervision information between near-end and far-end MMUs.
4.2.2.7 High Speed
This block provides a Point-to-Point connection to other PIUs via the High
speed Bus.
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