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Unformatted text preview: herefore, the Reed-Solomon and LDPC codes are
also used for Frame Validation. When the Reed-Solomon or LDPC codes are not used, the
Frame Error Control Field defined in references  or  is used for Frame Validation. CCSDS 131.0-B-2 Page 2-2 August 2011 CCSDS RECOMMENDED STANDARD FOR TM SYNCHRONIZATION AND CHANNEL CODING 2.2.4 SYNCHRONIZATION This Recommended Standard specifies a method for synchronizing Transfer Frames using an
Attached Sync Marker (ASM) (see section 8).
The ASM may also be used for resolution of data ambiguity (sense of ‘1’ and ‘0’) if data
ambiguity is not resolved by the modulation method used in the Physical Layer.
2.2.5 PSEUDO-RANDOMIZING This Recommended Standard specifies a pseudo-randomizer to improve several aspects of
the telemetry link that aid receiver acquisition, bit synchronization (see section 9),
convolutional code synchronization, and proper Frame Validation (see 2.2.3).
2.3.1 INTERNAL ORGANIZATION OF SUBLAYER
SENDING END Figure 2-2 shows the internal organization of the Synchronization and Channel Coding
Sublayer of the sending end. This figure identifies functions performed by the sublayer and
shows logical relationships among these functions. The figure is not intended to imply any
hardware or software configuration in a real system. Depending on the options actually used
for a mission, not all of the functions may be present in the sublayer.
At the sending end, the Synchronization and Channel Coding Sublayer accepts Transfer
Frames of fixed length from the Data Link Protocol Sublayer (see figure 2-1), performs
functions selected for the mission, and delivers a continuous and contiguous stream of
channel symbols to the Physical Layer. CCSDS 131.0-B-2 Page 2-3 August 2011 CCSDS RECOMMENDED STANDARD FOR TM SYNCHRONIZATION AND CHANNEL CODING Data Link Protocol Sublayer
Reed-Solomon, Turbo, or LDPC Encoding (optional)
or Transfer Frames
Pseudo-Random Sequence Generation (optional)
Codewords, or Transfer Frames
Attachment of Attached Sync Marker
Channel Access Data Units
Convolutional Encoding (optional)
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- Spring '14