When the reed solomon or ldpc codes are not used the

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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 [1] or [2] 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 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 Transfer Frames Reed-Solomon, Turbo, or LDPC Encoding (optional) Codeblocks, Codewords, or Transfer Frames Pseudo-Random Sequence Generation (optional) (Randomized) Codeblocks, Codewords, or Transfer Frames Attachment of Attached Sync Marker Channel Access Data Units Convolutional Encoding (optional) Channel Symbols Physical Layer...
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