1. DSL lines diagnostics - Parameters of analog part of xDSL transceiver Access Networks 2010/11 Ľ. Maceková, KEMT- FEI – TU - Košice

2. Describing of DMT in time domain (DMT is transport method in ADSL and VDSL systems): U k... amplitude of k-th carrier (it is modulated by QAM) φ k... phase of k-th carrier ω 0 = 2π. 4312,5 s -1... angle speed Fig. Typical time domain DMT signal look with limiting areas (signal mustn’t exceed their boundaries)... limiting areas

3. Actually, we evaluate nonlinear distortion, which is integrated in parameters : THD … Total Harmonic Distortion IMD … Inter-Modulation Distortion SINAD … SNR plus Distortion THD + N... THD plus Noise SFDR … Spurious Free Dynamic Range In addition, in DMT signal area: MTPR... Multi-Tone Power Ratio SNR... Signal-to-Noise Ratio… we know this already - all parameters are in units [dB] (logarithmic area) or clear number (ratio) or in [%]

4.  THD … Total Harmonic Distortion P 1 ; f P 1, P 2, P 3,... power of higher harmonics; result of devices nonlinearities (because of nonlinear transfer characteristics of amplifiers) power of basic frequency signal We measure all higher harmonics which can be distinguished from noise input output

5. 5  IMD … Inter-Modulation Distortion - it is product of nonlinearities of transfer characteristics when actuated by two frequencies signal - it is sum of intermodulation products of 2 input harmonics (sums, differencies and multiples) f 1,f 2, ; f 2 >f 1 f 2 ±f 1, f 2 ±2f 1,f 2 ±3f 1,... - the measurement: by modulation method or by differencial method [1] inputoutput

6. 6  SINAD – SNR plus Distortion - parameter which contains the noise and nonlinear distortion total output signal P sig in P sig, P 2, P 3,..., noise distortion power output signal after filtration of input signal

7. 7  SFDR – Spurious Free Dynamic Range - it is about nonlinear properties of devices again - they measure partial harmonic elements and another distortion elements; we are interested in distortion element with highest amplitude power of the distortion element with highest amplitude power of basic signal (1-st harmonic frequency) (measurement signal) [1] (hence SFDR < 0 dB)

8. 8  MTPR … Multi – Tone Power Ratio - this parameter is established for DMT average subchannel power (applied; transmitted) max. power of distortion signal in the position of unused subchannel (‘empty bin’) [1], [2]

9. … and another measurements: -measurement of impulse noise robustness -measurement of ADSL splitters -measurement of influensis of ADSL in voice (telephone) band - etc.

10. References: [1] J. Vodrážka, M. Havlan: Přístupové přenosové systémy, Cvičení – Měření na přípojkách xDSL, ČVUT Praha, 2003. [2] http://www.analog.com/static/imported-files/tutorials/MT-053.pdf