Premier Mounts CDM-600 사용자 설명서

7–1 

As standard, the CDM-600 Modem is equipped with four Forward Error Correction 
encoders/decoders – Viterbi, Sequential, concatenated Reed-Solomon and Trellis (which is 
available with the 8-PSK FAST option). The constraint lengths and encoding polynomials are 
not only Open Network compatible, but are also Closed Network compatible with the vast 
majority of existing modems from other manufacturers. Comtech EF Data has performed 
compatibility testing to ensure inter-operability. 
 
Turbo Coding represents a very significant development in the area of FEC, and optionally, 
the CDM-600 may be fitted with one of two Turbo Product Codecs They are plug-in daughter 
cards (SIMM modules), both field upgradeable. The Low Rate option provides data rate 
capability up to 5 Mbps, and code rates limited to Rate 5/16 (BPSK, Rate 21/44 (BPSK) and 
Rate 3/4 (QPSK, OQPSK, 8-PSK and 16-QAM). The High Rate option provides data rate 
capability up to 20 Mbps, in addition to Rate 7/8 and Rate 0.95 capability.  
 
Now, Low-Density Parity Check (LDPC) coding is being offered in addition to the TPC 
options. In some instances this provides even better performance than TPC. A third option 
card, again field upgradeable, combines LDPC and TPC together on one module. This povides 
the best Forward Error Correction technology currently available, and is offered with a 
sufficient range of code rates and modulation types that link performance can be optimized 
under any conditions.  

The combination of convolutional coding and Viterbi decoding has become an almost 
universal standard for satellite communications. The CDM-600 complies with the Intelsat