Matteo Bertocco

A Web-based distributed virtual educational laboratory

Evolution and cost of measurement equipment, continuous training, and distance learning make it difficult to provide a complete set of updated workbenches to every student. For a preliminary familiarization and experimentation with instrumentation and measurement procedures, the use of virtual equipment is often considered more than sufficient from the didactic point of view, while the hands-on approach with real instrumentation and measurement systems still remains necessary to complete and refine the students practical expertise. Creation and distribution of workbenches in networked computer laboratories therefore becomes attractive and convenient. This paper describes specification and design of a geographically distributed system based on commercially standard components.

Experimental Study of Coexistence Issues Between IEEE 802.11b and IEEE 802.15.4 Wireless Networks

Coexistence issues between IEEE 802.11b wireless communication networks and IEEE 802.15.4 wireless sensor networks, operating over the 2.4-GHz industrial, scientific, and medical band, are assessed. In particular, meaningful experiments that are performed through a suitable testbed are presented. Such experiments involve both the physical layer, through measurements of channel power and the SIR, and the network/transport layer, by means of packet loss ratio estimations. Different configurations of the testbed are considered; major characteristics, such as the packet rate, the packet size, the SIR, and the network topology, are varied. The purpose of this paper is to gain helpful information and hints to efficiently face coexistence problems between such networks and optimize their setup in some real-life conditions. Details concerning the testbed, the measurement procedure, and the performed experiments are provided.

A client-server architecture for distributed measurement systems

This paper describes a client-server architecture for the remote control of instrumentation over the Internet network. The proposed solution allows multi-user, multi-instruments sessions to be obtained by means of a queueing process and provides instrument locking capability. Client applications can be easily developed by using conventional high-level programming languages or well-assessed virtual instrumentation frameworks. Performance tests are reported, which show the low overhead due to network operations with respect to the direct control of the instruments.

Experimental Characterization of Wireless Sensor Networks for Industrial Applications

The effects of interference in the setup of wireless sensor networks (WSNs) represent a critical issue, and as such, it needs to be carefully addressed. To this aim, helpful information can be achieved through measurements to be carried out in advance on suitable prototypes and testbeds. In this paper, the measurement of industrial WSN performance is dealt with. In particular, a suitable testbed enlisting IEEE 802.15.4 wireless sensor nodes is presented along with the results of some experiments carried out even in the presence of interference. The purpose is to show how to evaluate some specific parameters of a WSN employed for industrial applications to obtain useful information for its setup optimization in the presence of interference. The analysis will show that from the measurement of these parameters (number of failed pollings, polling round-trip time, experimental cycle time, and alarm latency), interference effects can effectively be recognized, and the network setup can be optimized.

Evaluating energy efficiency of site-specific tillage in maize in NE Italy

This paper examine the efficiency of energy use of three conservation tillage practices (SST - sub-soil tillage; MT - minimum tillage; and NT - no tillage) performed within two management zones, previously identified in a field according to the stability of yield variability. Experiments were carried out in 2003 in NE Italy, on a farm near Rovigo, on a 8-ha field with clay soil, in maize (Zea mays, L.). The purpose of the paper is (i) to investigate the energy variability due to these tillage practices performed spatially within two management zones and (ii) to analyze the long-term energetic efficiency for each tillage practice. The energy balance was highest for SST with respect to MT and NT, due to labor and fuel consumption rates. The energy balance was influenced by the spatial pattern of yield, with appreciable differences between practices in terms of both the conversion index of energy for tillage (9.0, 12.6 and 22.8GJha(-1) for SST, MT and NT, respectively) and the energy use efficiency for tillage (8.0, 11.6, 21.8GJha(-1) for SST, MT and NT, respectively). Based on the simulated data and the calibration results, SALUS model proved to be a good tool for analyzing long-term effects of tillage practices on yield. The NT treatment showed the best efficiency over years, due to the low inputs in comparison with the output level.

On the Rate Adaptation Techniques of IEEE 802.11 Networks for Industrial Applications

The performance of the IEEE 802.11 WLAN are influenced by the wireless channel characteristics that reflect on the signal-to-noise ratio (SNR), particularly in industrial communication systems, that often operate in harsh environments. In order to cope with SNR reductions, the IEEE 802.11 WLAN specification suggests to adapt (reduce) the transmission rate, since the modulation techniques employed at the lower rates are more robust. However, the standard does not define any rate adaptation (RA) technique, leaving the actual implementation to the device manufacturers choice. In this paper we focus on RA techniques for industrial communication systems that are typically subjected to tight reliability and timing requirements. In detail, we compare the performance figures of a general purpose widespread technique, namely the automatic rate fallback (ARF), with those of the RA techniques actually implemented on two commercially available IEEE 802.11 devices via a set of practical experiments. The obtained results show that these techniques are characterized by a relevant number of packet retransmissions that may introduce a considerable randomness on the service time, possibly leading to performance degradation. Consequently, we propose two new techniques and evaluate their behavior by means of numerical simulations carried out for typical industrial traffic profiles. The outcomes are encouraging since the proposed RA techniques show in most cases better performance than ARF.

Virtual environment for fast development of distributed measurement applications

This paper deals with a virtual environment that allows automatic measurement systems to be easily developed by accessing programmable instrumentation, which can be located either in a local or in a remote laboratory. The environment, which is based on a client-server application that runs on a single personal computer or over the Internet, is designed to hide most of the details connected to the setup of a complex measurement system to the users. Client and server applications have been developed in Java/spl trade/ language so that they can be used on different platforms and are easily extensible to accommodate new processing tasks, interfaces, and instruments.

Analysis of dampled sinusoidal signals via a frequency domain interpolation algorithm

An algorithm for the estimation of the parameters that characterize a linear combination of damped sinusoids is presented. The procedure is based on an interpolation scheme applied to the discrete Fourier transform samples. At first, a single damped exponential signal is analyzed; then the results are extended to multiple damped sinewaves. Numerical simulations show the good accuracy obtained under various measurement conditions; both the effects of spectral interference and wideband noise are considered, proving the reliability of the proposed method in a number of engineering applications. >

Is CSMA/CA really efficient against interference in a wireless control system? An experimental answer

The deployment of a wireless control system must cope with a number of effects usually negligible in a wired scenario. To this aim, an experimental analysis on suitable prototypes and testbeds can readably offer a valid and rapid method to forecast the behavior of a real network. In this paper, performance measurement of industrial wireless sensor network in the presence of various type of interference is provided. In particular a Bluetooth, WiFi and Zigbee disturbing network impairs a suitable testbed employing IEEE 802.15.4 wireless sensor nodes. The purpose is to optimize the effectiveness of the medium access control mechanism through the choice of a proper mode of use. The analysis will show that from the measurement of certain parameters (number of failed pollings, experimental cycle-time, and alarm latency) interference effects can be effectively recognized and the network setup optimized.

Investigating WirelessHART coexistence issues through a specifically designed simulator

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, highlight improvements of WirelessHART with respect to IEEE 802.15.4 standard, concerning the Packet Error Ratio (PER) degradation of interfering networks.