The probability of rejection of the first pf1 and

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Unformatted text preview: (assuming 64-bit codeblocks, and BER of 10-5) as shown in Table D-8. Table D-8: Example of Performance of Frames in First and Second Contiguous CLTUs __________________________________________________________ Mode PF1 PF2 __________________________________________________________ 2.32x10-2 TED 2.32x10-2 SEC 7.24x10-6 6.37x10-4 __________________________________________________________ D - 4 . 3 . 1 Performance Augmentation Using Double Tail Sequences . The performance of subsequent CLTUs can be improved by doubling all tail sequences. That is, the normal tail sequence of the CLTU is followed by an added second tail of the same length (or, equivalently, with an idle sequence having the same bit alignment as the tail sequence, which produces the same effect). It is less likely the combination of TWO tails will be missed, thus improving the reliability of the decoder reaching SEARCH state. Such an organization is shown in Figure D-6. CLTU 1 ACQ START CLTU 2 TAIL INFO P INFO P 2nd TAIL OR IDLE FRAME 1 START TAIL INFO P INFO P FRAME 2 Figure D-6: Multiple CLTU Organization (With Added Tail/Idle) Issue 6 Page D-18 January 1987 CCSDS REPORT CONCERNING TELECOMMAND: SUMMARY OF CONCEPT AND SERVICE With this organization, the probability of missing both tails is the probability of missing the first one AND the probability of missing the second; that is, <Prob. of missing a double tail sequence, using TED decoding> = PTAD = (PTA)2 [EQ. K] and <Prob. of missing a double tail sequence, using SEC decoding> = PTBD = (PTB)2 [EQ. L] With double tails, the probabilities of missing a tail shown in Table D-7 take on the new values shown in Table D-9. Table D-9: Probability of Missing DOUBLE Tail Sequence, P TAD (TED) and PTBD (SEC) ___________________________________________________________________________ Probability of missing a double tail, for a Channel BER of Tail Sequence Decoding 10-5 10-6 length, bits Mode 10-4 ___________________________________________________________________________ 64 TED (PTAD ) SEC (PTBD ) 3.78x10-10 3.94x10-5 3.81x10-14 3.97x10-7 3.81x10-18 3.97x10-9 56 TED (PTAD ) SEC (PTBD ) 2.19x10-10 3.01x10-5 2.20x10-14 3.02x10-7 2.21x10-18 3.02x10-9 48 TED (PTAD ) SEC (PTBD ) 1.16x10-10 2.20x10-5 1.17x10-14 2.21x10-7 1.17x10-18 2.21x10-9 TED (PTAD ) 5.46x10-11 5.49x10-15 5.49x10-19 -5 -7 SEC (PTBD ) 1.52x10 1.52x10 1.52x10-9 ___________________________________________________________________________ 40 Issue 6 Page D-19 January 1987 CCSDS REPORT CONCERNING TELECOMMAND: SUMMARY OF CONCEPT AND SERVICE Example. If we take the example above of two maximum-length frames in separate but contiguous CLTUs (Table D-8) and use double tail sequences between the CLTUs (assuming 64-bit codeblocks and channel BER of 10-5), the probability of rejection of the first and second frames is shown in Table D-10. Table D-10: Example of Performance of Frames in First and Second Contiguous CLTUs Using DOUBLE Tail Sequences Between CLTUs ____________________________________________________________ PF2 Mode PF1 ____________________________________________________________ TED 2.32x10-2 2.32x10-2 SEC 7.24x10-6 7.63x10-6 ____________________________________________________________ D - 4 . 3 . 2 Performance Augmentati...
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This document was uploaded on 03/06/2014.

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