Rx Baseband Processing; Monitor & Control (M&C) Subsystem - Radyne DMD20 Installation And Operation Manual

DMD20/DMD20 LBST Universal Satellite Modem Theory of Operation
unaltered. In IDR, IBS, and D&I Modes, the framer adds the appropriate framing and ESC as
defined in IESS-308 and 309. In D&I Mode, the framer acquires the terrestrial framing structure,
E1 or T1, and synchronizes the Drop Processor. The Drop Processor extracts the desired time
slots from the terrestrial data stream and feeds these channels back to the framer. The framer
then places the 'dropped' terrestrial time slots into the desired satellite channel slots. The data is
then sent to the Reed-Solomon Encoder.
The Reed-Solomon Encoder, encodes the data into Reed-Solomon Blocks. The blocks are then
interleaved and synchronized to the frame pattern as defined by the selected specification
(IESS-308, IESS-309, DVB, etc.). After Reed-Solomon Encoding, the composite data and clock
are applied to the BB Loopback Circuit.

3.1.4 Rx Baseband Processing

The Receive Processor performs the inverse function of the Tx Processor. Data received from
the satellite passes through the BB Loopback Circuit to the Reed-Solomon Decoder to the
Deframer. The Deframer acquires the IBS/IDR/DVB frame, synchronizes the Reed-Solomon
Decoder and extracts the received data and overhead from the frame structure, placing the data
into the PD Buffer, sending the overhead data to the UIM. In Closed-Net Mode, the data is
extracted from the buffer and is sent to the UIM. Backward Alarm indications are sent to the M&C
Subsystem. In Drop and Insert Mode, the Insert Processor synchronizes to the incoming
terrestrial T1/E1 Data Stream, extracts satellite channels from the PD Buffer, and then inserts
them into the desired terrestrial time slots in the T1/E1 Data Stream.
3.1.5 Monitor & Control (M&C) Subsystem
Also contained on the BB Card is the M&C Subsystem. The M&C contains a high-performance
microprocessor and is responsible for overall command and control of modem functions. The
M&C is constantly monitoring all subsystems of the modem by performing a periodic poll routine
and configures the modem by responding to commands input to the system. During each poll
cycle, the status of each of the subsystems is collected and reported to each of the external ports
and Front Panel. Performance statistics such as Eb/No, buffer fill %, etc. are compiled. If faults
are detected, the M&C will take appropriate actions to minimize the effect of such faults on the
system (refer to the Fault Matrices in Section 6).
The M&C subsystem contains the following features:
TM103 – Rev. 2.5 3-5