Gianfranco Miele

Power Measurements in DVB-T Systems: New Proposal for Enhancing Reliability and Repeatability

The rapid growth of digital video broadcasting by terrestrial transmission (DVB-T) has created the need for new measurement methods, as well as new test equipment that is capable of providing reliable and repeatable results. Some problems are, in fact, being experienced with power measurements, particularly with those involving the integration of the input signal power spectrum over a certain frequency interval. Trying to give a proper answer to the cited need, a digital signal processing method, which has already been proposed in the literature and specialized for power measurements in spread spectrum systems, is optimized here to be operative in the presence of DVB-T signals as well. Suitable stages, in simulation and emulation environments, are designed and applied to optimally regulate key parameters of the method, thus making it assure negligible bias and high repeatability in most operative conditions. The results of a number of experiments on actual DVB-T signals also give evidence of the methods efficacy with respect to competitive measurement solutions.

A Methodological Approach for Estimating Protocol Analyzer Instrumental Measurement Uncertainty in Packet Jitter Evaluation

Packet jitter is a critical parameter to be accurately measured and monitored in communication and computer networks for quality-of-service assessment, particularly in Voice over Internet Protocol (VoIP) and real-time video applications. To this aim, suitable measurement systems, also known as “protocol analyzers,” are used. In particular, special-purpose-architecture-based protocol analyzer (SPAPA) and general-purpose-architecture-based protocol analyzer (GPAPA) are the most widespread measurement solutions. In both cases, the measurement chain involves a reference data traffic generator and one or more nodes, suitably displaced at the measurement points of interest in the network. With special regard to the instrumental measurement uncertainty of both SPAPAs and GPAPAs already present on the market, poor information is given by manufacturers. Moreover, the analysis in the literature concerning communication and computer network test and measurement clearly evidences the lack of important details on this key matter and, consequently, the need of further scientific investigation. This paper proposes a methodological approach to evaluate SPAPA and GPAPA instrumental uncertainty in packet jitter measurements. A general model accounting for the effect of the main quantities of influence is proposed, which allows quantifying the associated uncertainty components through a statistical analysis. A number of experiments on an actual GPAPA show the suitability and effectiveness of the proposal.

Experimental Investigation of the Electromagnetic Interference of ZigBee Transmitters on Measurement Instruments

This paper deals with the electromagnetic susceptibility of measurement systems when subjected to interference generated by short-range, low-power wireless transmitters. A ZigBee transmitter was used as an interfering source operating close to the instrumentation under test. The results of numerous tests prove that different kinds of measurement instrumentation can be affected by the wireless module interference. Significant metro- logical performance decay was observed for both frequency- and time-domain measurements carried out by instrumentation whose bandwidth includes the ZigBee frequency operating range.

An Internet Protocol Packet Delay Variation Estimator for Reliable Quality Assessment of Video-Streaming Services

Measurement of Internet Protocol Packet Delay Variation (IPDV) is a relevant issue in real-time video-streaming services. To assess the Quality of Service (QoS) to the end user, IPDV measures are commonly compared to conventional thresholds, whose values depend on the application requirements. However, exceeding these thresholds only for short time intervals and with relatively low repetition rates does not generally imply a significant decrease of the quality perceived by the users. Vice versa, IPDV values not exceeding the admitted threshold but very close to this value for long time intervals and characterized by relatively high repetition rates can significantly affect the quality perceived by the users. Consequently, studying the correlation between IPDV measures and some performance metrics directly related to the quality perceived by the end user is a very useful and challenging issue. Literature concerning with IPDV evaluation does not provide relevant information about the measurement procedure, such as measurement rate, way of collecting the obtained results in a single estimator, time interval during which the estimator is evaluated, and so on. The absence of these important aspects makes the comparison between IPDV measures and the aforementioned thresholds very critical, thus making even more ambiguous the evaluation of the QoS to the end user. In this framework, the aim of this paper is twofold. From one side, it aims at experimentally assessing and correlating the values that some performance metrics assume at different layers of a wide area network (WAN) supporting video-streaming applications for several values of IPDV; from the other side, it aims at deducing helpful and practical hints for designers and technicians, in order to efficiently assess and enhance the performance of a WAN supporting video streaming, in some suitable setup conditions affected by IPDV. The final goal of the research activity is to identify and fine tune an IPDV estimator able to reliably estimate and detect the objective service degradation from the user perspective. The obtained estimator should be sensitive to service degradation that disregards the users expectations, and at the same time, it should be insensitive to disturbs that do not cause a perceptible service degradation.

An efficient experimental approach for the uncertainty estimation of QoS parameters in communication networks

In communication networks setup and tuning activities, a key issue is to assess the impact of a new service running on the network on the overall Quality of Service. To this aim suitable figures of merit and test beds have to be adopted and time-consuming measurement campaigns generally should be carried out. A preliminary issue to be accomplished for is the metrological characterization of the test set-up aimed to provide a confidence level and a variability interval to the measurement results. This allows identifying and evaluating the intrinsic uncertainty to be considered in the experimental measurement of Quality of Service parameters. This paper proposes an original experimental approach suitable for the purpose. The uncertainty components involved in the measurement process are identified and experimentally quantified by means of effective statistical analyses. The proposed approach takes into account the general characteristics of the network topology, the number and type of devices involved, the characteristics of the current services operating on the network, and of the new services to be implemented, as well as the intrinsic uncertainties related to the set-up and to the measurement method. As an application example, the proposed approach has been adopted to the measurement of the packet jitter on a test bed involving a real computer network displaced on several kilometers. The obtained results show the effectiveness of the proposal.

Type a uncertainty in jitter measurements in communication networks

Reliable quality of service measurements are crucial issues to monitor and evaluate the performance of computer and communication networks. To these aims, depending on the applications, several figures of merit have to be measured. They mainly concern with: throughput, available bandwidth, packet jitter, one way delay, round trip delay, and packet loss. To estimate these quantities two general classes of measurement systems (also known as “protocol analyzers”) can be considered: Special Purpose Architecture based Protocol Analyzer (SPAPA) and General Purpose Architecture based Protocol Analyzer (GPAPA). Both measurement solutions can be thought as composed by a reference data traffic generator and one or more measurement nodes. All these components are constituted by hardware and software sections which cooperate to achieve the measurement results. Focusing the attention on the uncertainty involved in the QoS indexes measurement, no information is provided by the manufactures for both SPAPA and GPAPA. In addition, the analysis of the literature in the field of computer networks testing, has highlighted that this important aspect is not adequately dealt with or that methodological studies are not yet available. This paper proposes a suitable approach to evaluate the type A measurement uncertainty of SPAPA and GPAPA systems. A general model to study the effect of the involved quantities of influence is presented and a method to quantify their effects is provided. The experimental results show the suitability and the effectiveness of the proposal.

Packet jitter measurement in communication networks: A sensitivity analysis

Communication networks are widespread today. New services are now starting to run on these networks to meet the requests of modern users. To offer good service typically hard constraints have to be satisfied, especially when real-time services are involved. To this aim the reliable estimation of Quality of Service (QoS) parameters as bandwidth, packet jitter, latency, one way delay, to cite a few, is a key issue for communication networks setup, monitoring and tuning.

On the suitability of compressive sampling for the measurement of electrical power quality

The deeper interconnection and the increasing presence of active devices on the electrical networks is raising many issues concerning with the monitoring of Power Quality phenomena. Voltage parameters related to the supply of electricity and current parameters related to the working of electrical apparatuses have to be monitored as accurately as possible. To this aim specific international standards impose strict measurement methods and complex measurement instrument architectures, usually based on the computation of real time Fast Fourier Transforms, to be adopted for the purpose. In particular, considering poly-phase systems, four currents and four voltages have to be detected, synchronized, measured and analyzed with good accuracy and spectral resolution. This imposes to the measurement the calculation of eight FFTs in a very short time. These requirements conflicts with the need of cost-effective measurement instruments required by spread and distributed monitoring systems in many points of the electrical plant. To face this issues this paper proposes the study and the tuning of compressive sampling (CS) techniques capable of assuring reliable reconstruction of the signal of interest from very low acquired samples. In particular, to make the CS use more feasible, the authors have also exploited some peculiarities of the CS approach in order to reduce the computational burden usually associated with the mere application of its acquisition and reconstruction protocol. Preliminary results confirm the applicability of the proposed solution.

Influence of Wi-Fi Computer Interfaces on Measurement Apparatuses

Nowadays, low-power wireless technologies like Wi-Fi, ZigBee, Bluetooth, to cite a few, are often present in measurement environment. Sometimes, they can be considered as unwanted disturbances. Many times, they are used as communication medium to realize smart data transmission. Among them, Wi-Fi is the most widespread in the development of wireless local area networks (WLANs), and because of its good data transmission rates and plug-and-play capabilities, it is the main candidate for integrating measurement instruments in wireless networks. Although designed and developed to reduce at minimum its radiated emissions, Wi-Fi has to be considered as a potential interfering source for modern instrumentation that often has bandwidth and operating frequencies including the Wi-Fi band. For these reasons, a careful investigation on the electromagnetic susceptibility of measurement systems, when subjected to Wi-Fi, is carried out in this paper. Disturbance effects due to the Wi-Fi technology on typical measurement stations, including spectrum analyzers, digital oscilloscopes, universal counters, and digital multimeters, are analyzed. The achieved results prove that the effects of interferences due to the wireless module on modern instrumentation are often not negligible, thus potentially compromising its metrological performance and the measurement result reliability.

Proposal and analysis of new algorithms for wideband spectrum sensing in cognitive radio

The growing demand for available frequency bands in contrast to the scarcity of allocated spectrum slots, is promoting the development of smart wireless transmission terminals generally called cognitive radios. These devices are able to select the most suitable operating frequency and modulation scheme in order to minimize the probability of interference with other users operating in the same area. A key operation to reach this goal, is an accurate and reliable spectrum sensing, especially in environment characterized by the contemporaneous presence of many users, which could even transmit with a very low power. In order to implement this operation in cost-effective hardware, efforts for containing the computational burden should be also pursued. Several techniques for spectrum sensing are today present in literature, many of them require some knowledge about the context in which the system works, while further ones do not require any hypothesis on the signal to be detected. In this framework the authors propose and compare three algorithms based on a wideband analysis, possibly suited for the purpose. They all are thought for working in blind scenarios.