1. SLS-CS_16-12 Terminology Used with Sliced Transfer Frames
Fall Technical Meeting, Rome 17 to 21 Oct 2016
SLS-CS_ Terminology Used with Sliced Transfer Frames
V. Sank - NASA/GSFC/ASRC
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2. Code and Synch Pink, Sliced SMTFs
CADU
For the chapter on LDPC coding with unaligned Transfer Frames we initially,
reluctantly, accepted the term CADU for a Transfer Frames preceded by
an ASM.
After the last meeting NASA started work on a new project and found a total mess
with this term because all of the other system documents referred to the CADU
rate as the rate at the channel level with all the coding. To avoid mistakes for
that project we were forced to use the term CADU for the codeword/block.
We are now suggesting use of an alternate term for the ASM with Transfer frame.
We are asking the working group to select a term or pick one of the following
suggestions.
DTF Delimited Transfer Frame
STF Synchronizable Transfer Frame
SMTF Synch Marker with Transfer Frame
other ?
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3. CADU CCSDS 131.0-B-2 TM Synch and Channel Coding Blue Book
Code and Synch Pink, Sliced SMTFs
CADU
CCSDS B-2 TM Synch and Channel Coding Blue Book
CHANNEL ACCESS DATA UNIT
The data unit that consists of the ASM and the Transfer Frame (if the Physical Channel is not
Reed-Solomon, Turbo, or LDPC coded) or the Reed-Solomon Codeblock or Turbo or LDPC
Codeword (if the Physical Channel is Reed-Solomon, Turbo, or LDPC coded) is called the
Channel Access Data Unit (CADU). The Transfer Frame, Codeword, or Codeblock in the CADU
may or may not be randomized.
The current AOS Blue Book makes only this one mention of CADU. On next slide, the pink sheets propose a change.
If the change is not accepted, the current statement needs to be corrected to say that the CADU is the various types
of codeblocks with a preceding synchronization marker.
… or the Reed-Solomon Codeblock or Turbo or LDPC
Codeword preceded by a synch marker (if the Physical Channel is …
Once corrected, no change is required for the case of sliced transfer frames.
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4. the physical channel unit. 9.1.2 CHANNEL ACCESS DATA UNIT
Code and Synch Pink, Sliced ASM + Transfer Frames
Addition of chapter 8 on slicing causes the old chapter 8 to now be chapter 9.
The following is the pink sheet proposal with last line not required if CADU used only for
the physical channel unit.
9.1.2 CHANNEL ACCESS DATA UNIT
The data unit that consists of the ASM and the Transfer Frame (if the Physical Channel is not
Reed-Solomon, Turbo, or LDPC coded) or the Reed-Solomon Codeblock or Turbo or LDPC
Codeword (if the Physical Channel is Reed-Solomon, Turbo, or LDPC coded) is called the
Channel Access Data Unit (CADU). The Transfer Frame, Codeword, or Codeblock in the
CADU may or may not be randomized.
This Recommended Standard defines data unit called the Channel Access Data Unit (CADU)
whose contents are as per attached table 9-1. The Transfer Frame, codeword, or codeblock in
the CADU may or may not be randomized.
NOTE – The term ‘CADU’ originated in reference [E3] and is now in established use,
even though it may not be applicable to a channel.
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5. Specific things to change if CADU is use for only for
Code and Synch Pink, Sliced ASM + Transfer Frames
Back Up
Specific things to change if CADU is use for only for
Physical Channel Data Unit
(Partial List)
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6. Code and Synch Pink, Sliced SMTFs
No change required
Code and Synch Pink, Sliced SMTFs
2.2.4 SYNCHRONIZATION
This Recommended Standard specifies a method for synchronizing Transfer Frames using an
Attached Sync Marker (ASM) (see section 9).
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.
This Recommended Standard also defines a Code Sync Marker (CSM) (see section 8) that,
when used, may also be used for resolution of data ambiguity. The CSM is not used for
synchronizing Transfer Frames.
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7. Code and Synch Pink, Sliced SMTFs
Small change required
Code and Synch Pink, Sliced SMTFs
2.3.1 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 sublayer1 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. When LDPC encoding of a stream of SM + TFs
Channel Access Data Units (CADUs), defined in 9.1.2, is performed, the sending end does codeword
randomization and attachment of Code Sync Marker as described in section 8 and shown
explicitly in figure 8-2.
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8. Figure 2-2 Code and Synch Pink, Sliced SMTFs Original Figure 2-2
New Figure 2-2 in pink sheets
Or stream of ASM with Transfer
Frames when slicing used
Remove word “Attached”
and this applies to all cases
Leave as in current blue
book
Figure 2-2
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9. Code and Synch Pink, Sliced SMTFs
CADU to SM+TF
Code and Synch Pink, Sliced SMTFs
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. When LDPC decoding of a stream of CADUs SM+TF is performed, the receiving end
does Code Sync Marker detection and codeword derandomization as described in section 8
and shown explicitly in figure 8-2.
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10. Figure 2-3 Small change to figure Code and Synch Pink, Sliced SMTFs
Original Figure 2-3
New Figure 2-3
Or stream of ASM with Transfer
Frames when slicing used
Leave as in current blue
book
Figure 2‑3: Internal Organization of the Sublayer at the Receiving End
Figure 2-3
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11. Code and Synch Pink, Sliced SMTFs
CADU to SMTF below
Code and Synch Pink, Sliced SMTFs
Input Transfer
Frames
Stream of SMTFs
(input to the Slicer)
Information Blocks
(Input to Encoder)
Encoded Blocks
i.e. LDPC codewords
(Encoder Output)
Encoded Symbols
with CSM to
Physical Layer
Transfer Frame Synchronization
Marker (ASM 32 bits)
M bits
k bits
n bits
Code Frame Synchronization Marker (CSM)
CSM length depends on code rate.
m*n bits
m*n bits
An LDPC codeblock may contain one
or more Codewords. m=2 shown here.
Figure Transfer Frames Sliced to form Codeblocks  
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12. Code and Synch Pink, Sliced SMTFs
CADU to SM+TF
Code and Synch Pink, Sliced SMTFs
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