Unformatted text preview: cal layer must have been
randomized as described in 3.3.1 or the Physical Layer must invoke a technique (modulation
type, phase-coherent data and subcarrier, or other) to guarantee sufficiently frequent
transitions for adequate symbol synchronization.
4.2.3 IDLE SEQUENCE The Idle Sequence is the data structure which provides for maintenance of symbol
synchronization in the absence of CLTUs. The bit pattern is a sequence of alternating “ones”
and “zeros”.2 The length of the Idle Sequence is an unconstrained number of bits. 2 Previously, the idle sequence was constrained to begin with a “zero” to be continuous with
the tail sequence. Because of the improved performance of the tail sequence in this issue,
the constraint is no longer necessary. CCSDS 201.0-B-3 Page 4-1 June 2000 CCSDS RECOMMENDATION FOR TELECOMMAND: CHANNEL SERVICE 4.3 STANDARD PROCEDURES WITHIN THE LAYER Operations within the Physical layer begin with the activation of the physical telecommand
channel by invoking the radio frequency carrier and modulation techniques. These techniques
include provision of any required command link subcarrier(s) and data modulation in order to
establish the physical connection fro...
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