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Streaming media applications generate a sizable part of network traffic and represent a significant proportion of network providers' income. The commitment to user satisfaction can be summarized by different concepts, content providers emphasizing quality of experience (QoE), whereas network providers are more focused on quality of service (QoS). Measuring QoS parameters, and understanding the relationship...
Photoplethysmography (PPG) is a widely used technology, routinely employed for heart rate measurement in low-cost medical devices. Monitoring is notoriously more difficult during physical exercise, since motion artifacts may considerably degrade PPG signals. The approach discussed in this paper estimates human heart rate and reliably tracks its charges by a robust algorithm, whose main steps include...
The paper presents an experimental analysis of some link layer characteristics of GPRS (General Packet Radio Service) mobile networks and discusses their relationship to TCP/IP performances. Mobile networks implement sophisticated mechanisms in order to provide mobility and capacity in a wide area. Unfortunately, large delays along the radio path may be introduced, thus reducing throughput in data...
This paper deals with the estimation of the temporal evolution of heart rate (HR), in subjects undertaking physical exercise, using wrist-type photoplethysmographic (PPG) signals. The proposed algorithm employs a zero-padded DFT to provide a raw HR estimate with small frequency granularity and feeds it into a Kalman filter to accurately track HR evolution over time. Furthermore, heuristics are applied...
The accuracy of time distribution over packet networks relies on propagation delay stability and two-way symmetry in the path between the master clock and a slave clock. Multipath time synchronization provides a possibility to safeguard accuracy by exploiting path diversity, while improving security and fault-tolerance through inherent redundancy. In this paper we focus on the problem of combining...
The problem of device synchronization in a distributed measuring system can present a designer with a range of choices and solutions, depending on technical specifications, cost, feasibility, robustness and other requirements. In wireless sensor networks (WSNs), synchronization mechanisms often have to be run on lean resources and, in particular, the active and “sleep” time schedules of low-power...
In a wireless network, synchronization accuracy can be significantly affected by impairments affecting the physical layer. It is well known that path delay asymmetry adversely affects timing protocols based on two-way message exchanges but, unfortunately, bounds to link asymmetry are hard to ensure when timing messages are exchanged through wireless links. It would then be desirable to be able to...
The accuracy level achievable with a given synchronization system is straightforwardly related to timestamp accuracy. Therefore, different methods have been proposed in the literature for reducing measurement uncertainty in synchronization systems. However, another important problem is deciding whether a received time information is trustworthy, particularly when timing messages generated by a supposedly...
Measurement in power systems and, particularly, in smart grids and smart microgrids is often concerned with harmonic analysis of voltage and current waveforms, which can be obtained by Fourier-based algorithms (e.g., phasor measurements, power quality analysis). Any such measurement algorithm is characterized by a fundamental time-frequency resolution tradeoff that relates the sampling frequency and...
Sensor networks need a common timescale to be shared among their constituent elements. Accuracy and reliability are key issues in time dissemination, the latter aspect being specifically addressed in several synchronization schemes. In the paper, we present an approach to reliability assessment based on monitoring the innovation of the Kalman filter employed as the local clock servo in a sensor node...
Instrumentation supporting the development of cognitive radio systems is faced with challenging requirements. The ability to determine the mutual coordination and timing of primary and secondary sources and generally support troubleshooting requires significant enhancements to the capabilities of a vector signal analyzer. In this context, we introduce and discuss the performances of a modulation detector...
Smart microgrids exploit information and communication technologies to efficiently manage local renewable energy sources and energy storage devices, collectively known as distributed energy resources (DERs). This requires the inclusion of rather sophisticated sensing and/or actuating units within the DER interfaces.
Several factors may impact on the achievable performances of a synchronization system: among them, the accuracy of drift and offset estimates, the short and long term stability of the unregulated clock, the rate at which timing information are exchanged, the probability of losing protocol messages for a given period of time and so on. Therefore, when a synchronization scheme is considered, it is very...
In this paper we propose a method based on multimodal histograms for analyzing digitally modulated signals. This method does not require any a-priori knowledge on modulation parameters. This makes it particularly interesting in applications where information about the modulated signal are missing or known only approximately, and the capability to analyze a digitally modulated signal with partial knowledge...
This paper analyzes the effects on synchronization performances of the accuracy of skew and offset estimates, the short and long-term stability of the unregulated clock, the rate at which timing information is exchanged within the network. The work makes use of a simulated clock based on the state-variable model, for which realistic parameters are obtained from experimental measurements of Allan variance...
This paper proposes a tool for on-line analysis of network traffic traces. This tools is based on the extraction of measurement information from both detail and approximation coefficients of a wavelet transform. In particular, it merges concepts drawn from the rate-interval curve analysis, with the better known wavelet multi-resolution analysis approach.
In this paper, the WirelessHART communication scheme is investigated. The protocol is at first described, in order to underline the key aspects of its design; then, a simulation tool is presented: it enables analysis that accounts for both protocol and physical layers issues. In particular, interference effects on protocol choices can be easily analyzed. The experimental results, obtained from simulations,...
Scaling phenomena can be found in a variety of physical situations, ranging from applications in hydrology to communication traffic measurements. This paper focuses on quantiles estimation for a self-similar time series and in particular on the uncertainty that affects their estimates. Quantiles provide in fact additional information about the distribution of the measurements and in certain cases...
In this paper we propose a method, related to the theory of Network Calculus, for the analysis of aggregate network traffic by means of empirical rate-interval curves obtained from experimental data. The algorithm on which it is based differs from the commonly employed wavelet-based approach, although it retains some of its multiresolution features. We briefly introduce the theoretical aspects, analyze...
The paper presents a test bed designed to evaluate synchronization performances for a generic network environment in a variety of different conditions. The emphasis is on the effects of cross-traffic on the one-way delay of packets containing timing information, as well as the study of timestamping inaccuracies. The work discusses and motivates the choices made in the design of the test bed and analyze...
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