Unformatted text preview: leared at the start of a block) receives kI–Q symbols
representing information (where Q, representing fill, is a multiple of I, and is less than kI),
2EI check symbols shall be computed over kI symbols, of which the leading Q symbols shall
be treated as all-zero symbols.
NOTE – A (nI–Q, kI–Q) shortened codeblock results.
220.127.116.11 The leading Q symbols (all zeros) of the resulting shortened codeblock shall be
neither entered into the encoder nor transmitted. CCSDS 131.0-B-2 Page 4-3 August 2011 CCSDS RECOMMENDED STANDARD FOR TM SYNCHRONIZATION AND CHANNEL CODING NOTE – Shortening the transmitted codeblock length in this way changes the overall
performance to a degree dependent on the amount of virtual fill used. Since
it incorporates no virtual fill, the maximum codeblock length allows full
performance. In addition, as virtual fill in a codeblock is increased (at a
specific bit rate), the number of codeblocks per unit time that the decoder
must handle increases. Therefore, care should be taken so that the maximum
operating speed of the decoder (codeblocks per unit time) is not exceeded.
4.3.8 REED-SOLOMON CODEBLOCK PARTITIONING AND VIRTUAL FILL 18.104.22.168 Parts of the partitioned Reed-Solomon codeblock (see figure 4-1) are defined as
a) The Reed-Solomon Check Symbols shall consist of the trailing 2EI symbols (2EIJ
bits) of the codeblock.
1 As an example, when E = 16 and k = 223, for I=5 this is always 1280 bits. 2 The Transfer Frame is defined by the TM Space Data Link Protocol (reference )
or the AOS Space Data Link Protocol (reference ). For constraints on the
length of the Transfer Frame, see section 10. b) The Attached Sync Marker used with R-S code
1) shall be the 32-bit pattern specified in section 8;
2) shall precede the Transmitted Codeblock.
NOTE – Frame synchronizers should therefore be set to expect a marker at every
Transmitted Codeblock + 32 bits.
c) The Transmitted Codeblock shall consist of the Transfer Frame (without the 32-bit
sync marker) and R-S check symbols.
1 The Transmitted Codebl...
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