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Unformatted text preview: h as SEC) cause reduced
performance on undetected errors, and vice versa. Therefore an acceptable balance must be
found between these two objectives. Reference  shows that the required undetected error
performance will be met by the prescribed system using either TED or SEC decoding in a
channel operating at a BER of 10-5 without extra precautions. However, if a greater margin of
safety against undetected errors is desired, the cyclic redundancy code specified in Reference
 may be added to each frame. For an overhead of 16 bits per frame and the same channel
BER of 10-5, this will provide an undetected frame error rate of 10-19 when using SEC
decoding; with TED decoding, the performance is better. Figure D-7 shows curves comparing
undetected error performance (with and without the added CRC) as a function of number of
codeblocks in a frame for channel BER of 10-5. These curves are from Reference . Issue 6 Page D-23 January 1987 CCSDS REPORT CONCERNING TELECOMMAND: SUMMARY OF CONCEPT AND SERVICE
(SEC DECODING) PROBABILITY OF UNDETECTED FRAME ERROR 10 -10 10 -11 BCH CODEBLOCKS
ALONE 10 -14 10 -15 (TED DECODING) 10 -16 10 -19 10 -20 BCH CODEBLOCKS
WITH FRAME CRC
(SEC DECODING) 10 -21 10 -22
0 10 20 30 40 50 60 NUMBER OF CODEBLOCKS PER FRAME Figure D-7: Undetected Error Performance, With and
Without Cyclic Redundancy Code
END OF DOCUMENT. o Issue 6 Page D-24 January 1987...
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