NEC PASOLINK, Учебный курс

Страница: 32 / 110

FUNCTIONAL OPERATION
ROI-S04488
2-22
2.5 Receive Digital Processing
This section describes the frame synchronization, descrambling and
demultiplexing.
2.5.1 Frame Synchronization
FS bits which are multiplexed at the transmitting end are detected and
comparing to establish the frame synchronizer.
2.5.2 Descrambling
To recover original data streams from received data streams, descrambling
is performed by using the same frame pattern as the transmitting end.
2.5.3 Demultiplexing
The two descrambled data streams enter the demultiplexer (DEMUX).
The DEMUX circuit extracts the frame pattern, multiframe pattern, ASC
and DSC signal bits, etc. from overhead bits with a clock produced at the
TIM GEN.
2.6 Receive Line Equalization
This section describes the demultiplexing and unipolar-to-bipolar code
conversion.
2.6.1 Demultiplexing
From received data streams, the alarm information, AIS RCVD, loopback
control/answer and stuff information bits, etc. are extracted by the
Demultiplexer (DEMUX) circuit. Then, 2.048 Mbps
x N unipolar data/
CLK signals are fed to the next U/B CONV circuit.
2.6.2 Unipolar-to-Bipolar Code Conversion
To provide the associated DTE with the original data stream in bipolar
pulse format, the unipolar-coded 2.048 Mbps data streams are converted
into 2.048 Mbps data streams in the specified bipolar pulse format (HDB3)
by the U-B CONV circuit on the INTFC section.