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Unformatted text preview: 1.60x10-5 7.10x10-4 1.60x10-7 7.10x10-5 1.60x10-9 48 40 1 TED SEC 6.28x10-3 1.20x10-5 6.30x10-4 1.20x10-7 6.30x10-5 1.20x10-9 TED 9.36x10-3 9.40x10-4 9.40x10-5 SEC 1.60x10-5 1.60x10-7 1.60x10-9 ___________________________________________________________________________ 40 32 2 At the other extreme, the maximum frame length permitted is 256 octets or 2048 bits. Such a frame could be organized into either 40-, 48-, 56- or 64-bit codeblocks as shown in Table D-5. Tables D-4 and D-5 show how frame rejection performance varies with different parameters. It can be seen that the rejection performance is affected little by length of codeblocks, moderately by number of codeblocks, and greatly by the decoding mode. Issue 6 Page D-13 January 1987 CCSDS REPORT CONCERNING TELECOMMAND: SUMMARY OF CONCEPT AND SERVICE Table D-5: Probability of Rejection of a MAXIMUM Length Frame as a Function of Codeblock Length Chosen ___________________________________________________________________________ MAXIMUM LENGTH FRAME CodeInforNo. of DeProbability of frame rejection block mation codecoding for channel BER of length, field, blocks mode 10-5 10-6 bits bits needed 10-4 ___________________________________________________________________________ 64 56 37 TED SEC 2.09x10-1 7.21x10-4 2.32x10-2 7.24x10-6 2.34x10-3 7.24x10-8 56 48 43 TED SEC 2.12x10-1 6.37x10-4 2.35x10-2 6.40x10-6 2.36x10-3 6.40x10-8 48 40 52 TED SEC 2.18x10-1 5.61x10-4 2.43x10-2 5.63x10-6 2.46x10-3 5.63x10-8 TED 2.22x10-1 2.48x10-2 2.51x10-3 SEC 4.74x10-4 4.75x10-6 4.75x10-8 ___________________________________________________________________________ 40 D-4.2 32 64 Multiple Frames, One CLTU Since the CCSDS Recommendation (Reference [4]) does not limit the size of a CLTU, it is possible to have more than one frame in a single CLTU. An example of such an organization is shown in Figure D-4. CLTU ACQ START FRAME 1 TAIL FRAME 2 FRAME 3 N1 CODEBLOCKS N2 CODEBLOCKS N3 CODEBLOCKS Figure D-4: Multiple Frame, Single CLTU Organization The performance of multiple frames contained in a single CLTU is complicated by the fact that acceptance of each frame in the CLTU requires acceptance of the frame before it. If at any time a particular frame is rejected, frames preceding it will have been accepted, and the rejected frame and all those following are rejected. Thus it would appear prudent to base performance comparisons on the probability of rejection of the LAST frame in the CLTU, since the last frame is dependent on the performance of each of the preceding frames. Issue 6 Page D-14 January 1987 CCSDS REPORT CONCERNING TELECOMMAND: SUMMARY OF CONCEPT AND SERVICE A simplification can be made if one realizes that the rejection of the LAST frame is simply dependent on the performance of the codeblock continuum through the last frame. Thus the same equations (Eqs. E and F) can be used as for a single frame if we consider the contiguous string of frames to be equivalent to one very long frame: the meaning of N then becomes the total number of codeblocks contained in the last frame plus all the preceding frames of the CLTU in question. As an example, Table D-6 shows the probability of rejectio...
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This document was uploaded on 03/06/2014.

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