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Research Done
Implementation of the KS statistic algorithm for CoMo v0.2
Wavelet decomposition and reconstruction written in C
Compression of Network Performance Measurements using Wavelets and DCT
MRTG monitoring of test network
3
Compression of Network Performance Measurements
DCT and WT with 75% (L2) and 93% (L4) reduction
Bursty and non bursty signals
200220240260280300320
125497397121145169193217241265289313337361385409433457481505529553577601625649Time (hours)
Delay (ms)150170190210230250270290310330350
124477093116139162185208231254277300323346369392415438461484507530553576599622645Time (hours)
Delay (ms)
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Constant 75% and 93% compression for Bursty signal
Signal Bursty
Transform DCT DCT WT WT
Reduction 75% 93% 75% 93%
Input (bytes) 2592 2592 2592 2592
Output (bytes) 648 164 648 164
Compression ratio 1:4 1:15.8 1:4 1:15.8
Mean abs error 5.39 8.05 4.35 7.44
Mean % error 2.99 4.25 2.23 3.86
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Constant 75% and 93% compression for Non-Bursty signal
Signal Non-Bursty with abrupt change
Transform DCT DCT WT WT
Reduction 75% 93% 75% 93%
Input (bytes) 2688 2688 2688 2688
Output (bytes) 672 168 672 168
Compression ratio 1:4 1:16 1:4 1:16
Mean abs error 0.80 2.13 0.44 1.55
Mean % error 0.35 0.91 0.19 0.65
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Variable compression triggered by KS statistic
KS statistic identifies general differences between 2 distributions
Level of compression depends on the KS critical value:
If KS value > Da then apply low compression else high
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Da = c(a)n1+ n2
n1* n2
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Variable compression for Bursty signal
Signal Bursty
Transform Wavelet
Reduction Variable reduction L2 and L4
Input file (bytes) 2592
Output file (bytes) 322
Compression ratio 1:7.8 (similar to constant L3)
Mean abs error 6.46
Average % error 3.34
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Variable compression for Non-bursty signal
Signal Non-bursty
Transform Wavelet
Reduction Variable reduction L2 and L4
Input file (bytes) 2688
Output file (bytes) 236
Compression ratio 1:11.4
Mean abs error 0.55
Average % error 0.24
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Conclusions
Wavelets adapt to sudden changes better than DCT
For bursty signal, V.C. gives same results as a L3 WT
For the non bursty signal V.C. gives a compression ratio close to that of a L4 WT while keeping the error close to an error of a L2 WT