Comtech EF Data SDM-9000 - Manual (Page 188)

Options SDM-9000 Satellite Modem
A–2 Rev. 4
A.1.1 Specifications
Reed-Solomon Codec word n = 208
k = 192
t = 8
Interleaver Modified block interleaving, depth = 4
Unique word insertion Per IESS-308 specification
Note: The Reed-Solomon implementation conforms to the INTELSAT IESS-308
specification.
A.1.2 Theory of Operation
The Reed-Solomon Codec card works in conjunction with the Viterbi decoder to provide
concatenated convolutional encoding and decoding. The Reed-Solomon Codec block
diagram is shown in Figure A-1. The two main sections of the Codec that will be
discussed in this section are the Reed-Solomon encoder (Section A.1.2.1) and the Reed-
Solomon decoder (Section A.1.2.2).
A.1.2.1 Reed-Solomon Encoder
A block diagram of the Reed-Solomon encoder section is shown in Figure A-2. The
Reed-Solomon encoder section includes the following circuits:
•
8-bit parallel scrambler
•
Input FIFO
•
Reed-Solomon Codec
•
Output First In/First Out (FIFO)
•
Interleaver
•
8-bit parallel to 3-bit serial channel reformatter
JP2 TXSATDAT JP2
JP2
MUXDAT
(SERIAL)
MUXCLK
U5
INPUT
FIFO
U6
RS CODEC
(ENCODER
SECTION)
U6
UNIQUE WORD
INSERTION
U5
RAM
INTERLEAVER
U4
8 BIT PARALLEL
TO 3 CHANNEL
SERIAL
REFORMATTER
JP2 TXSATCLK
U5
INTERLEAVER
ADDRESS
GENERATOR
U5
RS TIMING
U5
CONTROLLER
SYNCHRONOUS
SCRAMBLER
PARALLEL
Figure A-2. Reed-Solomon Encoder Section Block Diagram