Comtech EF Data DMDVR20 LBST Rev 1.1 - Manual (Page 35)

Theory of Operation DMDVR20 LBST Satellite Modem
3-14 TM136 – Rev. 1.1
Figure 3-7. Reed-Solomon Encoder Functional Block Diagram
Figure 3-8. Reed-Solomon Decoder Functional Block Diagram
Table 3-1. Reed-Solomon Codes
Type of
Service Data Rate
(Kbps)
R-S Code
(n, k, t) 1
Bandwidth
Expansion
[ (n/k) -1 ]
Interleaving
Depth
Maximum 2
R-S Codec
Delay (ms)
Small IDR
(With 16/15
O/H)
64
128
256
384
512
768
1024
1536
(126, 112, 7)
(126, 112, 7)
(126, 112, 7)
(126, 112, 7)
(126, 112, 7)
(126, 112, 7)
(126, 112, 7)
(126, 112, 7) 0.125
0.125
0.125
0.125
0.125
0.125
0.125
0.125 4
4
4
4
4
4
4
4 115
58
29
19
15
10
8
5
IDR
(With 96
Kbps O/H)
1544
2048
6312
8448 (225, 205,10)
(219, 201, 9)
(194, 178, 8)
(194, 178, 8)
0.0976
0.0896
0.0899
0.0899 4
4
4
4 9
7
2
<2
8PSK 1544
2048
6312
8448 (219, 201, 9)
(219, 201, 9)
(219, 201, 9)
(219, 201, 9) 0.0896
0.0896
0.0896
0.0896 8
8
8
8 18
13
4
3
1. n = code length, k = information symbols and t = symbol error correcting capability.
2. Design objective.
3.8 Locating the ID Code Operational Procedure
The modem has unique ID codes that allow the user to add feature upgrades to the modem
without the unit having to be returned to the factory. Users are required to identify these ID codes