Pietro Paglierani

Accuracy of effective bits estimation methods

The basic assumptions of analog-to-digital converter (ADC) effective bit estimation procedures are analyzed and closed-form expressions that link accuracy to the parameters that describe the measurement conditions are derived. It is shown that the achievable accuracy mainly depends on the ratio between the number of acquired samples and the number of ADC quantization levels. Furthermore, the effect of broad-band noise superimposed to the sinewave employed as test input is analyzed. Results useful for the design of the estimation procedure itself are also provided.

A noise model for digitized data

The paper analyzes the overall conversion error of a noisy digitizer affected by Gaussian noise at its input or generated within the digitizer itself. It is shown that, under mild conditions concerning the ratio between the input noise standard deviation and the quantization step, the overall conversion error can be modeled by a Gaussian random variable uncorrelated with the input sequence. The power of the global conversion error is evaluated in closed formulae together with its degree of variability. Numerical simulations support the proposed analysis.

Uncertainty Evaluation of Objective Speech Quality Measurement in VoIP Systems

This paper deals with the measurement uncertainty of the speech quality (SQ) achievable by an actual voice-over-Internet-protocol (VoIP) telephony network. The accuracy of end-to-end speech data provided by the perceptual estimation of SQ (PESQ) algorithm suggested in the International Telecommunication Union (ITU) recommendation P.862 is discussed. Then, the uncertainty of the PESQ results under different measurement conditions and real-life VoIP equipment (media gateway) is analyzed. This problem, in fact, has received very little attention in the literature, although many results related to other kinds of PESQ applications are available. Meaningful experimental data are reported and discussed mainly by means of statistical tools.

A noise model for quantized data

The paper analyzes the overall conversion error of a noisy analog-to-digital (A/D) converter affected by Gaussian noise at its input or generated within the A/D itself. It is shown that under mild conditions concerning the ratio between the input noise standard deviation and the quantization step, the overall conversion error can be modeled by a Gaussian random variable uncorrelated with the input sequence. The power of the global conversion error is evaluated in closed formulae together with its degree of variability. Numerical simulations support the proposed analysis.

Non-intrusive measurement of impulsive noise in telephone-type networks

An in-service, non-intrusive technique for the characterization of stationary and impulsive noise in a telecommunication system is presented. It is based on the segmentation of the signal observed during a telephone call in speech and noise periods by means of a Bayesian classifier. The signal observed during noise periods is further processed by means of a hypothesis testing procedure in order to detect noise-impulses. Experimental results that show the effectiveness of the proposed technique are discussed.

Accuracy performances of ADC parameter estimators

A lower bound to the accuracy of commonly adopted estimation methods for the overall conversion error power of a sinusoidal input signal is provided in the paper. It is shown that such bound depends only on the conversion error power and is inversely proportional to the number of samples of the quantized sequence. Simulation results are reported that validate the obtained theoretical results. The provided analysis is useful for the design of estimation procedures that satisfy the accuracy requirements of the test.

In-service non-intrusive measurement of echo parameters in telephone-type networks

The paper presents an in-service non-intrusive technique for the measurement of the echo path delay and echo attenuation in telephone-type networks. The proposed method is based on a cross-correlation technique in conjunction with adaptive filtering of the observed transmitted signal. Experimental results show the high accuracy and robustness of the proposed measurement procedure.

In-service nonintrusive measurement of noise and active speech level in telephone-type networks

The paper presents an in-service, nonintrusive technique for the measurement of noise level and active speech level in telecommunication systems. It is based on the segmentation of the signal observed during a telephone call into active speech and noise intervals and on an improved method for level estimation via the determination of the noise-level probability density function. Experimental results show the high accuracy of the method also under poor signal-to-noise ratio conditions and its robustness with respect to other real-life impairments found in telecommunication lines.

Uncertainty evaluation of speech quality measurement in VoIP systems

The paper analyses the problem of testing the speech quality performance provided by a real VoIP telephony network. To this aim, the objective measurement of end-to-end speech quality by means of the PESQ algorithm is discussed, and its accuracy as an estimator of the subjective Mean Opinion Score is summarised Then, the application of the PESQ algorithm in the analysis of the performance of real life VoIP systems is presented A characterization of the PESQ algorithm uncertainty under different measurement conditions and network scenarios is provided This particular problem, in fact, has received little attention in the literature, even though many results on the use of the PESQ algorithm in other types of applications have been presented by researchers. Experimental data obtained in the speech quality characterization of a real-life VoIP equipment (Media Gateway) are reported and discussed.

On the use of in-service, nonintrusive measurement devices in the performance analysis of telephone-type networks

In the paper the problem of assessing the speech quality provided by a real-life telephone-type network is considered. Two different approaches to the quoted problem are presented: subjective approach, based on customer surveys or trained operators, and objective approach, based on instrumental measurements of key transmission parameters. Advantages and drawbacks associated with the quoted approaches are summarised and briefly discussed. An objective approach based on an In-Service Nonintrusive Measurement Device (INMD) is also presented. Finally, real life experiments, which show the effectiveness of the INMD approach are reported and discussed.