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Data Rate Nomenclature
• We should agree upon a common scheme for
describing the various data rates in a system that
works for optical communication
– In some proposals, data rate values refer to bit
streams prior to FEC encoding; others cite data
rate values for bit streams post FEC encoding
– In addition, there can be some confusion
regarding channel symbol rates (especially for
PPM where M slots comprise a single symbol)
– We may leverage previous CCSDS agreements
From CCSDS Green Book “Bandwidth Efficient Modulations”
Interleaver Nomenclature
• In each of the discussed coding proposals, there
are interleaver(s) proposed
• In discussion, we’ve resolved confusion as to the
interleaver’s purpose
• Interleavers in the ESA/DLR proposal (CCSDS standard for
Reed-Solomon) and in the NASA SCPPM code definition are
to avoid the bursty errors common to FEC decoding schemes
• Interleavers in the NASA proposals have extensive memory
depths to mitigate fading on atmospheric optical links
• Recommendation: to avoid confusion, we should
label each as a “code interleaver” or a “channel
interleaver”