Dvb-S Transport Layer: Reed Solomon Code; Synchronized Randomization; Figure 30: Concatenation Principle - Safran CORTEX Series User Manual

3.3.7.3

DVB-S Transport Layer: Reed Solomon Code

As defined in § 4.7 of ECSS-E50-01 draft 0.5, the concatenation principle correspond to the following
processes but with some interaction between them as depicted in next figure:
Randomized Codeblocks
Transfer frames
Scrambler
(DVB-S type)
Synchronization for
frame/RS and scrambler
hronisation
Transfer frames Randomized Codeblocks
Descrambler
(DVB-S type)
3.3.7.3.1

Synchronized Randomization

Within the transmitter, the input digital data is randomized with a PRBS whose characteristics are:
 Generating polynomial: 1+x14+x15
 Initialization sequence: 100101010000000
This sequence is loaded at the beginning of each transport frame. Due to the chosen polynomial, it is
possible to output the data by bytes with the help of a shifted calculation , i.e. out bit1 or MSB of byte =
reg15 EX-OR reg14, out bit2 = reg14 EX-OR reg13, out bit3 = reg13 EX-OR reg12, out bit4 = reg12
EX-OR reg11, out bit5 = reg11 EX-OR reg10, out bit6 = reg10 EX-OR reg9, out bit7 = reg9 EX-OR
reg8 and out bit8 or LSB of byte = reg8 EX-OR reg7 and then shift by 8 bits the contents of the register
before calculating the PRBS sequence for the next byte.
It should be noticed that in order to avoid tedious rate changes, the data have to be captured at the
interface by group of 238 bytes with one blank byte in front and 16 blank bytes at the rear. During the
blank bytes, the randomization is shifting but the enable bit must be downed to zero.
The randomization processing is described on next figure.
© Safran Data Systems – IMP000074 e14r1
HIGH DATA RATE RECEIVER
HDR-4G+ USER'S MANUAL
Row/column
R-S encoder
interleaving with
(DVB-S type)
sync. Bytes
insertion
Transport frames
R-S decoder
(DVB-S type)

Figure 30: Concatenation Principle

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Ref. DTU 100782
Is.Rev 3.5
Date: June 1, 2021
Transport frames
Bytes to Symb.
transformation
MTCM symbols
Symb. to bytes
MTCM
transformation
decoding
/deinterleaving
Sync bytes
search/global sync.
Safran Data Systems
MTCM symbols
MTCM encoding
8PSK modulation
Channel_symbol
8PSK
demodulation
.
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