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3.3 STANDARD PROCEDURES WITHIN THE CODING LAYER The following subsections define the procedures for randomization of Input Data and coding
of TC Codeblocks.
3.3.1 RANDOMIZATION PROCEDURE In order to maintain bit (or symbol) synchronization with the received telecommand signal,
the incoming signal must have a minimum bit transition density (see Recommendation 2.2.3
in Reference ).
If a sufficient bit transition density is not ensured for the channel by other methods (e.g., by
use of certain modulation techniques or data that is phase-coherent with the subcarrier) then
the randomizer defined in this subsection is required. Its use is optional otherwise.
The presence or absence of randomization is fixed for a physical channel and is managed
(i.e., its presence or absence is not signaled but must be known a priori by the spacecraft and
ground system). A random sequence is exclusively ORed with the Input Data to increase
the frequency of bit transitions. On the receiving end, the same random sequence is
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This document was uploaded on 03/06/2014.
- Spring '14