Safran CORTEX CRT Quantum, User Manual

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COMMAND RANGING & TELEMETRY UNIT CORTEX
CRT QUANTUM USER'S MANUAL
Ref. DTU 100042
Is.Rev. 5.17
Date: Dec.
03, 2021Sept. 30, 2021
© Safran Data Systems
This document is the property of
Safran Data Systems
.
It cannot be duplicated or distributed without expressed written consent.
Page 69
3.3.6.4.
Reed-Solomon Decoding
Reed-Solomon coding technique is well suited for burst error correction. It can be used in conjunction with Viterbi
coding to allow data reconstruction with the lowest error probability. Reed-Solomon decoding and error-
correction by the CORTEX CRT Quantum complies to the CCSDS recommendation CCSDS 131.0-B-3. The
following coding characteristics should be used:

J = 8 bits per R-S symbol

E = 16 R-S (E = 8 R-S available in SPS version E6R23 and higher) symbol error correction
capability within a R-S codeword (coded to decoded information ratio = 223/255 if E = 16
and ratio=239/255 if E = 8)

Symbol interleave factor: 1 to 8, auto-adjusted (frame-length dependent, see below),

Virtual Fill factor: auto-adjusted (frame-length dependent, see below),

Selection of the Beta base (default setup for all SPS versions) or the Alpha base (available
in SPS version E4R32 and higher)

Other characteristics: see CCSDS recommendation CCSDS 131.0-B-3.
Formula for the determination of the Interleave I depending upon the frame length FL (bytes, including ASM):
I = 1:
36 < FL ≤ 259
1 < I ≤ 8:
255 x (I-
1) + 4 < FL ≤ 255 x I + 4
Formula used for the determination of the Virtual Fill Q (bytes):
Q = 255 - (FL
– 4) / I
Decoder Error if Q is not integer
The TMU monitoring table indicates the number of corrected R-S symbols.
If the number of errors in the frame exceeds the maximum number of correctable errors, the Bad Transfer
Frame Counter is incremented.