Reed-Solomon Coder/Decoder; Figure A-17. Reed-Solomon Rs(204,188,8) Error-Protected Packet - Comtech EF Data SDM-9000 Installation And Operation Manual

SDM-9000 Satellite Modem
A.2.7 Reed-Solomon Coder/Decoder
The Reed-Solomon coder receives scrambled data packets in byte serial format.
RS(204,188,8) shortened code—from the original RS(255,239,8) code—is applied to
each scrambled transport packet (188 bytes) to generate an error-protected packet. Refer
to Figure A-17 for the packet arrangement.
Note: RS coding is also applied to the non-inverted or inverted packet sync byte.
The shortened Reed-Solomon code is implemented by adding 51 bytes, all set to zero, to
the information bytes at the input of a (255,239) encoder. These bytes are discarded after
the encoding procedure.
The code and field generator polynomials are shown below.
Code Generator Polynomial:
g(x) = (x + α
Field Generator Polynomial:
p(x) = x8 + x4 + x3 + x2 + 1
Rev. 4
SYNC
SCRAMBLED PAYLOAD (187 BYTES)
BYTE
Reed-
Figure A-17. Solomon RS(204,188,8) Error-Protected Packet
0 ) (x + α 1 ) (x + α 2 ) ... (x + α
204 BYTES
(1,632 BITS)
15
)
Options
RS(204,188,8)
16 BYTES
A–21