Table 3-2. Available Tpc And Ldpc Modes; Figure 3-19. Tpc & Ldpc Modes Performance (Relative To Shannon Limit) - Comtech EF Data DMD-2050E Installation And Operation Manual

DMD2050E Universal Satellite Modem
It can be seen from this graph that, for Code Rates above 3/4, Comtech's TPCs are very close
(1-1.5 dB) to the Shannon Limit. However, at 3/4 and below, LDPCs are performing 0.7-1.2 dB
better than TPCs.
Figure 3-19. TPC & LDPC Modes Performance (Relative to Shannon Limit)
It is clear that, in order to provide the best possible performance over the range of code rates
from 1/2 to 0.95, both an LDPC and a TPC codec need to be offered.
In order to meet this requirement, Comtech EF Data has developed a combination LDPC/TPC
Codec module that can be added to the DMD2050E Modem. Table 3-2 outlines the operating
modes provided by this module.
Mode
TPC Rate 21/44 BPSK (aka 1/2)
Rate 5/16 BPSK
Rate 21/44 QPSK, OQPSK (aka 1/2)
Rate 3/4 QPSK, OQPSK
Rate 3/4 8-PSK , 8-QAM
Rate 3/4 16-QAM
Rate 7/8 QPSK, OQPSK
Rate 7/8 8-PSK , 8-QAM
MN-DMD2050E Revision 2

Table 3-2. Available TPC and LDPC Modes

Code Rate/Modulation
Lower Data Rate Limit Upper Data Rate Limit
(kbps)
18.0
18.0
18.0
27.0
40.0
54.0
31.5
48.0
Theory of Operation
(kbps)
5965.9
3906.2
11931.8
18750.0
25000.0
25000.0
21875.0
25000.0
3–53