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Unformatted text preview: Figure 2-2: Internal Organization of the Sublayer at the Sending End
2.3.2 RECEIVING END Figure 2-3 shows the internal organization of the Synchronization and Channel Coding
Sublayer of the receiving 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 (e.g., some implementations perform
frame synchronization before convolutional decoding when convolutional code rate 1/2 is
used) . Depending on the options actually used for a mission, not all of the functions may be
present in the sublayer.
At the receiving end, the Synchronization and Channel Coding Sublayer accepts a
continuous and contiguous stream of channel symbols from the Physical Layer, performs
functions selected for the mission, and delivers Transfer Frames to the Data Link Protocol
Sublayer. CCSDS 131.0-B-2 Page 2-4 August 2011 CCSDS RECOMMENDED STANDARD FOR TM SYNCHRONIZATION AND CHANNEL CODING Data Link Protocol Sublayer
Reed-Solomon, Turbo, or LDPC Decoding (optional)
Codeblocks, Codewords, or
Pseudo-Random Sequence Removal (optional)
Codewords, or Transfer Frames
Channel Access Data Units
Convolutional Decoding (optional)
Physical Layer Figure 2-3: Internal Organization of the Sublayer at the Receiving End CCSDS 131.0-B-2 Page 2-5 August 2011 CCSDS RECOMMENDED STANDARD FOR TM SYNCHRONIZATION AND CHANNEL CODING 3 CONVOLUTIONAL CODING 3.1 OVERVIEW The basic convolutional code is a rate (r) 1/2, constraint-length (K) 7 transparent code which
is well suited for channels with predominantly Gaussian noise. This code is defined in 3.3.
When this code is punctured according to 3.4, higher code rates may be achieved although
with lower error correcting performance.
Puncturing allows a single code rate of either 2/3, 3/4, 5/6 or 7/8 to be selected. The four
different puncturing schemes allow selection of the most appropriate level of error corre...
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This document was uploaded on 03/06/2014.
- Spring '14