GR712RC-UM, Jun 2017, Version 2.9 209 www.cobham.com/gaisler
GR712RC
for which the highest power of x is transmitted first;
• interleaving is supported for depth I = {1 to 8}, where information symbols are encoded as I
codewords with symbol numbers i + j*I belonging to codeword i {where 0
i < I and 0 j <
255};
• shortened codeword lengths are supported;
• the input and output data from the encoder are in the representation specified by the following
transformation matrix T
esa
, where i
0
is transferred first
• the following matrix T
-1
esa
specifying the reverse transformation
• the Reed-Solomon output is non-return-to-zero level encoded.
The Reed-Solomon Encoder encodes a bit stream from preceding encoders and the resulting symbol
stream is output to subsequent encoder and modulators. The encoder generates codeblocks by receiv-
ing information symbols from the preceding encoders which are transmitted unmodified while calcu-
lating the corresponding check symbols which in turn are transmitted after the information symbols.
The check symbol calculation is disabled during reception and transmission of unmodified data not
related to the encoding. The calculation is independent of any previous codeblock and is perform cor-
rectly on the reception of the first information symbol after a reset.
Each information symbol corresponds to an 8 bit symbol. The symbol is fed to a binary network in
which parallel multiplication with the coefficients of a generator polynomial is performed. The prod-
ucts are added to the values contained in the check symbol memory and the sum is then fed back to
the check symbol memory while shifted one step. This addition is performed octet wise per symbol.
This cycle is repeated until all information symbols have been received. The contents of the check
symbol memory are then output from the encoder. The encoder is based on a parallel architecture,
including parallel multiplier and adder.
g
esa
x x
i
+
i 120=
135
g
j
x
j
j 0=
16
==
g
esa
x x
i
+
i 112=
143
g
j
x
j
j 0=
32
==
0
1
2
3
4
5
6
7
7
6
5
4
3
2
1
0
00110111
01011111
10000111
00001001
00111111
00101011
01111001
01111011
=
7
6
5
4
3
2
1
0
0
1
2
3
4
5
6
7
=
11101101
01011111
00010111
01011010
10001000
01010110
00000011
10011000
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