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Unformatted text preview: e identifier. CCSDS 132.0-B-1 Page 2-12 September 2003 CCSDS RECOMMENDATION FOR TM SPACE DATA LINK PROTOCOL Packet
Service VC Access
Service Packet VCA_SDU VC_FSH VC_OCF
VC_OCF VC Frame
Service VC Frame
VCID MC_FSH MC_OCF MC Frame
Service MC Frame
MCID All Frames
Demultiplexer Figure 2-7: TM Space Data Link Protocol Channel Tree
2.4 SERVICES ASSUMED FROM LOWER LAYERS 2.4.1 SERVICES ASSUMED FROM THE SYNCHRONIZATION AND CHANNEL
As described in 2.1.1, the TM Synchronization and Channel Coding Recommendation
(reference ) must be used with the TM Space Data Link Protocol as the Synchronization
and Channel Coding Sublayer specification.
The functions provided by the TM
Synchronization and Channel Coding Recommendation are as follows:
a) error control encoding and decoding functions (optional);
b) bit transition generation and removal functions (optional);
c) delimiting and synchronizing functions.
The Synchronization and Channel Coding Sublayer, then, transfers contiguous, fixed-length,
delimited protocol data units as a contiguous stream of bits over a space link using the
services of the underlying Physical Layer. CCSDS 132.0-B-1 Page 2-13 September 2003 CCSDS RECOMMENDATION FOR TM SPACE DATA LINK PROTOCOL 2.4.2 PERFORMANCE REQUIREMENTS TO LOWER LAYERS
The coding options of the TM Channel Coding and Synchronization Recommendation and
the performance of the RF link provided by the Physical Layer shall be chosen according to
the following criteria:
a) the probability of misidentifying the MCID and VCID shall be less than a missionspecified value;
b) the probability of not correctly extracting Packets from Transfer Frames using the
First Header Pointer and the Packet Length Field shall be less than a missionspecified value.
In order to assure correct decoding at the receiving end, the same coding options must be
applied to all Transfer Frames of a Physical Channel. CCSDS 132.0-B-...
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