Safran CORTEX CRT Quantum - Convolutional Decoding

COMMAND RANGING & TELEMETRY UNIT CORTEX
CRT QUANTUM USER'S MANUAL
Ref. DTU 100042
Is.Rev. 5.17
Date: Dec.
03, 2021Sept. 30, 2021
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Page 62
3.3.6.2. Convolutional Decoding
Convolutional coding technique is well suited for telemetry channels with predominant Gaussian noise.
Convolutional 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:
 Convolutional code with maximum likelihood (Viterbi) decoding
 Code rate : 1/2, 1/3, 2/3, 3/4, 5/6, 7/8 bit per symbol
 Constraint length : 7 bits
 Connection vectors : G1 = 1111001; G2 = 1011011; for 1/3 rate G3 = 1100101
 Phase relationship : G1 is associated with first or second symbol. Not programmable for 1/3 rate.
 Symbol inversion : Programmable on output path of G2 (inverted or not inverted). Not
programmable for 1/3 rate.
The TMU monitoring table indicates if the Viterbi decoder is locked or unlocked and gives the symbol error rate.
Figure 30: Probability of Bit Error versus Eb/No.
Ref : CCSDS130.1-G-2 (§ 4.6), November 2012