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SLM-3650 Satellite Modem
Installation
2.4
Turbo Product Code FEC
The SLM-3650 modem supports the optional Turbo Product Code Forward Error
Correction (FEC) feature. A Turbo Product Codec can be installed at the factory or
added as a field-installed upgrade to modems currently deployed. Seven new Turbo code
rates/modulations are supported:
•
BPSK 5/16
•
BPSK 21/44
•
QPSK 3/4
•
OQPSK 3/4 (requires OQPSK optioned modem)
•
8PSK 3/4 (requires 8PSK optioned modem)
•
QPSK 1/2
•
OQPSK 1/2 (requires OQPSK optioned modem)
These Turbo code rates and modulations are also compatible with the equivalent
functions in the similar modems. Interoperability between these modems and the
SLM-3650 is guaranteed.
Benefits of Turbo Product Code FEC include:
Enhanced BER Performance
Reduced Delay
Soft Knee Characteristic
Bandwidth Efficiency
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QPSK 3/4 rate Turbo provides nearly a 2 dB improvement over Viterbi 3/4 rate
concatenated Reed-Solomon.
Significantly less processing delay (latency) than concatenated Reed-
Solomon modes.
Traditional concatenated Reed-Solomon schemes exhibit a pronounced
threshold effect where a small reduction in Eb/No results in a total loss of
data. Turbo does not suffer from this problem; the decoder stays locked down
to the point of unusable error rate.
No additional bandwidth expansion requirement (such as that associated with
Reed-Solomon coding), resulting in bandwidth savings of 9% to 13%.
2-21
Revision 3
MN/SLM3650.IOM
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