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Unformatted text preview: 1.60x10-5 7.10x10-4
1.60x10-9 48 40 1 TED
9.36x10-3 9.40x10-4 9.40x10-5
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
DeProbability of frame rejection
for channel BER of
64 56 37 TED
7.24x10-8 56 48 43 TED
6.40x10-8 48 40 52 TED
2.22x10-1 2.48x10-2 2.51x10-3
4.74x10-4 4.75x10-6 4.75x10-8
40 D-4.2 32 64 Multiple Frames, One CLTU Since the CCSDS Recommendation (Reference ) 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
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.
- Spring '14