COMMAND RANGING & TELEMETRY UNIT CORTEX
CRT QUANTUM USER'S MANUAL
Ref. DTU 100042
Is.Rev. 5.17
Date: Dec.
03, 2021Sept. 30, 2021
This document is the property of Safran Data Systems.
It cannot be duplicated or distributed without expressed written consent.
3.3.6.5. Turbo Decoding
Licensing:
Implementers should be aware that a wide class of turbo codes is covered by a patent by France Télécom and
Télédiffusion de France under US Patent 5,446,747 and its counterparts in other countries.
Potential user agencies should direct their requests for licenses to:
Mr. Christian Hamon
CCETT GIE/CVP
4 rue du Clos Courtel
BP59, 35512 CESSON SEVIGNE Cedex, France
Tel: +33 2 99 12 48 05, Fax: +33 2 99 12 40 98
E-mail: christian.hamon@cnet.francetelecom.fr
Turbo decoding and error-correction by the CORTEX CRT Quantum complies to CCSDS recommendation
CCSDS 131.0-B-3. The Turbo decoder implements the Log-MAP algorithm and with 4 bits input quantized soft
values.
The following coding characteristics should be used:
Payload block size (bits): 1784, 3568, 7136, 8920
Code rate: 1/2
Up to 16 iterations depending on the bit rate, the number of parallel turbo decoders and the
FPGA IP clock.
On-the-fly configuration
CCSDS recommended synchronization words (default) or user set synchronization words
(if defined registry key, any length between 4 and 192 bits and multiple of 4 bits)
Other characteristics: see CCSDS recommendation CCSDS 131.0-B-3.
Note 1: decoded frames are available on TCP/IP port without synchronization word systematically.
Where: is the number of turbo iterations performed (rounded by ½)
is the payload (or decoded) bit rate (bps)
is the payload size in bits
is the clock frequency of the decoding engine: 66 MHz or 50 MHz depending on the
license.
The Payload block size is set through the Frame/block size parameter. If turbo decoding is turned on (i.e.
TURBO RATE = 1/2), this parameter is read as a number of bits. If the Payload block size does not correspond
to CCSDS standard (i.e. different from 1784, 3568, 7136, 8920) it will cause an alarm.
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