A frame-level measurement apparatus for performance testing of ATM equipment

Performance testing of asynchronous transfer mode (ATM) equipment is dealt with here. The attention is principally paid to frame-level metrics, recently proposed by the ATM Forum because of their suitability to reflect user-perceived performance better than traditional cell-level metrics. Following the suggestions of the ATM Forum, more and more network engineers and production managers are interested today in these metrics, thus increasing the need of instruments and measurement solutions appropriate to their estimation. Trying to satisfy this exigency, a new VME extension for instrumentation (VXI) based measurement apparatus is proposed in the paper. The apparatus features a suitable software, developed by the authors, which allows the evaluation of the aforementioned metrics by simply making use of common ATM analyzers; only two VXI line interfaces, capable of managing the physical and ATM layers, are, in fact, adopted. Some details concerning ATM technology and its hierarchical structure, as well as the main differences between frames, specific to the ATM adaptation layer, and cells, characterizing the underlying ATM layer, are first given. Both the hardware and software solutions of the measurement apparatus are then described in detail, paying particular attention to the measurement procedures implemented. In the end, the performance of a new ATM device is assessed through the proposed apparatus.     

A new measurement method for through-the-wall detection and tracking of moving targets

The paper deals with a new measurement method for through-the-wall detection and tracking of hidden targets (e.g. human bodies in rescue missions) in two-dimensional scenes, by using radiofrequency signals. In particular, the method is based on a multisensor system and exploits an advanced imaging technique, which takes advantages from a regularized linear inversion scheme.     

GRID-Based Power Measurement in Digital Wireless Communication Systems

The combined use of multitaper estimation and wavelet thresholding has proved to be a very powerful digital- signal-processing algorithm in achieving the true power spectrum of signals that are peculiar to digital wireless communication systems and in ultimately carrying out accurate and repeatable power measurements. Nevertheless, the induced computational burden is too heavy. This paper mainly shows that GRID, which is currently one of the key technologies in deploying global-scale computing infrastructures, can make the aforementioned algorithm enforceable in a real-time context. A GRID computing-based approach for power measurement in digital wireless communication systems is proposed, which allows high levels of accuracy and repeatability in a significantly reduced measurement time. After a concise outline of the measurement algorithm, all of the adopted hardware and software strategies are described in detail. Major results concerning performance assessment and actual measurements are also given and discussed.     

Distributed microtrigeneration systems

In recent years, great attention, both in research and application fields, has been focused on the transition from centralized to decentralized (or Distributed Generation, DG) energy “production” systems. This process is currently being carried out partially. The benefits and drawbacks that DG will provide to the end-user and to the community have also been analyzed in both technical and scientific literature. All over the world researchers are strongly involved in the so-called “hydrogen economy” scenario that expects a geographically widespread system of production, storage, transportation and use of hydrogen.     

Measuring $I/Q$ Impairments in WiMAX Transmitters

This paper presents a new method for measuring the I /Q impairments affecting the worldwide interoperability for microwave access (WiMax) transmitters through the analysis of the signal acquired through a general-purpose I /Q receiver. Based on a model of the effects of the I /Q impairments on the output signal that is suitable for orthogonal frequency-division multiplexing (OFDM) systems like WiMax, the method is designed to correctly take into account the peculiarities of systems compliant with the IEEE 802.16-2004 standard, such as the potentially noxious effects of the impairments on signal normalization and threshold decisions. The results of the experiments carried out on the standard-compliant signals are given.     

Research on the Biocompatibility of the New Magnesium Alloy LANd442—An In Vivo Study in the Rabbit Tibia over 26 Weeks

Research on magnesium based degradable implant materials has finally obtained success in orthopaedics. Based on the previous good results with LAE442 magnesium alloy, the new LANd442 alloy was developed. In doing this, the single element neodymium replaces the rare earth compound. The primary objective of this study is to assess the biocompatibility of the new alloy in the rabbit model. During a 26 week period, the animals were investigated using clinical, radiological and in vivo µ‐CT techniques. Following euthanasia, histological, fluorescent microscopy and ex vivo µ‐CT investigations were done. Clinically, additional bone formed at the implant's location and accumulation of small amounts of subcutaneous gas can be observed. Radiological investigations show brightening of the medullary cavity and thickening in the region of the diaphysis. The µ‐computed tomographies reveal a reduction in the bone density from 1226.31 to 1192.95 mg HA/ccm together with increases in bone porosity from 4.55 to 6.6% and bone volume from 1.51 to 2.06 mm³ · slice^?1. By means of fluorochrome sequential marking, the determined MARs lie between day 93 and 120 at 3.58 µm · d^?1 and between day 120 and 179 at 2.25 µm · d^?1. Elevated remodelling processes in the bone are histologically confirmed due to the periosteal and endosteal growths and an increased appearance of osteoclasts. Owing to the established considerable bone remodelling processes following intramedullary implantation, LANd442 appears to be a less suitable degradable implant material for cortical bone applications.     

Evaluation of the biocompatibility of two magnesium alloys as degradable implant materials in comparison to titanium as non‐resorbable material in the rabbit

The aim of this study is to compare the biocompatibility of the two magnesium based alloys LAE442 and LANd442 with that of titanium. For this purpose, cylindrical implants were introduced into the medullary cavity of rabbit's tibiae for 4 and 8 weeks. Animals without any implant served as a control. In the follow-up, clinical, X-ray and μCT-investigations were performed to evaluate the reactions of the bone towards the implanted materials. After euthanasia, ex vivo μCT- and histological investigations were performed to verify the results of the in vivo tests. It could be shown that all materials induce changes in the bone. Whereas LANd442 caused the most pronounced reactions, such as increasing bone volume and bone porosity and decreasing bone density, titanium showed the most bone–implant contact by forming trabeculae. The tibiae of rabbits without implants also reacted by forming cavities, it is therefore assumed that the surgery method itself influences the bone.     

Advanced processing techniques of high-voltage impulse test signals

Automated analysis and processing of the digital records obtained in high-voltage (HV) impulse tests requires special techniques that are able to detect and characterize all sorts of disturbances (of short and long duration) in all waveform types (full, chopped, and sliced). Especially for the cases where a short-duration disturbance has to be removed before the evaluation of the impulse parameters, it is important to characterize the disturbance both in time and frequency. This paper describes a new technique based on the wavelet transform used for this purpose. Experimental results show the technique's reliability when applied to actual HV impulses     

Cross-Layer Measurements for a Comprehensive Characterization of Wireless Networks in the Presence of Interference

Assessing the overall performance of wireless communication networks is of key importance for optimal management and planning. With special regard to wireless networks operating in an unlicensed band, evaluating overall performance mainly implies facing the coexistence issues, which are associated with the contemporaneous presence of true and interfering signals at the physical layer. This task is difficult to fulfill only on the basis of single-layer measurements, if not prohibitive; a partial perspective of network behavior would, in fact, be gained. With this concern, a cross-layer approach is presented hereinafter. It provides for several measurements to be concurrently carried out at different layers through a proper automatic station. It aims to correlate the values of the major physical-layer quantities (e.g., channel power and signal-to-interference ratio) exhibited by those characterizing the key higher layers' parameters (e.g., packet-loss ratio and one-way delay) in the presence of interference. A first step toward a full characterization of how the effects of a problem, which is experienced at the physical layer, propagates along the whole protocol stack, can thus be taken.