Claudio Sacchi

A distributed surveillance system for detection of abandoned objects in unmanned railway environments

In this paper, a distributed video-surveillance system for the detection of dangerous situations related to the presence of abandoned objects in the waiting rooms of unattended railway stations is presented. The image sequences, acquired with a monochromatic camera placed in each guarded room, are processed by a local PC-based image-processing system, devoted to detecting the presence of abandoned objects. When an abandoned object is recognized, an alarm issue is transmitted to a remote control center located a few miles from the guarded stations. A multimedia communication system based on direct sequence code-division multiple-access (DS/CDMA) techniques aims at ensuring secure and noise-robust wireless transmission links between the guarded stations and the remote control center where the processing results are displayed to the human operator. Results concern: 1) the performances of each local image processing system in terms of false-alarm and misdetection probabilities, and 2) the performances of the CDMA multimedia transmission system in terms of bit error rates (BERs) and quality of service (QoS).

EHF for Satellite Communications: The New Broadband Frontier

The exploitation of extremely high-frequency (EHF) bands (30-300 GHz) for broadband transmission over satellite links is currently a hot research topic. In particular, the Q-V band (30-50 GHz) and W-band (75-110 GHz) seem to offer very promising perspectives. This paper aims at presenting an overview of the current status of research and technology in EHF satellite communications and taking a look at future perspectives in terms of applications and services. Challenges and open issues are adequately considered together with some viable solutions and future developments. The proposed analysis highlighted the need for a reliable propagation model based on experimental data acquired in orbit. Other critical aspects should be faced at the PHY-layer level in order to manage the tradeoff between power efficiency, spectral efficiency, and robustness against link distortions. As far as networking aspects are concerned, the large bandwidth availability should be converted into increased throughput by means of suitable radio resource management and transport protocols, able to support very high data rates in long-range aerospace scenarios.

Advanced image-processing tools for counting people in tourist site-monitoring applications

This work aims at demonstrating the usefulness of exploiting novel image-processing tools for moving-object detection and classification in the context of an actual application involving the remote monitoring of a tourist site. The application concerns outdoor people counting for tourist-flow estimation in a constrained environment. The technical problems to be solved are concerned with: (a) the design and implementation of low-complexity background updating and change detection algorithms able to adapt themselves to the time-varying illumination scene conditions, and (b) the integration of real-time pattern-recognition tools in order to distinguish group of persons to be counted from other objects present in the scene. The achieved results have proven that the proposed system makes it possible to obtain reliable people counting in different environmental situations, with an absolute mean error at most equal to 10%.

A QoE-Oriented Strategy for OFDMA Radio Resource Allocation Based on Min-MOS Maximization

A balanced strategy for OFDMA radio resource allocation based on game theory concepts is presented. Its main novelty with respect to state-of-the-art methods is that resource allocation is based on application-oriented Mean Opinion Score (MOS), rather than the aggregate system data rate. Thus, users data flows cooperate in a proactive way in order to jointly maximize the Quality of Experience (QoE). Experimental results show that the MOS achievable by the proposed resource allocation strategy is higher than the one provided by uncoordinated strategies based on water-filling and cooperative strategies based on pure data rate maximization.

Experimental Missions in W -Band: A Small LEO Satellite Approach

W-band (75-110 GHz) is proposed nowadays as a valuable alternative to intensively-exploited Ku- and Ka-bands for high-speed transmission over satellite networks. In such a framework, some experiments are being carried out, which are targeted to verify the feasibility of exploitation of W-band for broadband service deployment. From a theoretical viewpoint, the large bandwidth availability and the scarce amount of interference typical of W-band should guarantee high capacities. Nevertheless, many crucial aspects are still to be carefully investigated, e.g., signal propagation issues, RF impairments, choice of modulation and coding, efficient antenna design, etc. In this paper, an overview is made on the low Earth orbit (LEO) nano-satellite mission in-orbit key-test and validation of W-band (IKNOW). IKNOW mission is an ongoing advanced feasibility study part of an Italian Space Agency Project, named W-band analysis and verification (WAVE), coordinated by the Department of Electronic Engineering, University of Rome ldquoTor Vergatardquo. The main objective of the IKNOW mission is to tackle some of the unexplored critical aspects concerning W-band satellite transmission. In such a perspective, IKNOW should be regarded as a ldquopilot mission,rdquo whose results will be used for a first uplink-downlink satellite channel characterization, in-orbit validation of W-band technology, and space qualification processes. This paper is focused on the research work carried out in a preliminary phase of the IKNOW study and will also consider a number of elements related to the mission configuration, payload architecture, link analysis, potential RF impairment factors, and atmospheric effects. Proposed analysis and preliminary results shown can provide to interested readers the basic guidelines that will drive the practical implementation of IKNOW mission, as well as the most relevant issues to be faced by future developers of W-band missions using small LEO satellites.

SALICE project: Satellite-Assisted Localization and Communication Systems for Emergency Services

Restoring the connectivity in the emergency areas and providing NAV/COM services able to support and coordinate the rescue teams represent two of the main telecommunication needs for efficient emergency situation management. The SALICE (Satellite-Assisted LocalIzation and Communication system for Emergency services) Project aimed at identifying the system architecture and the most suitable solutions to be adopted in the future integrated reconfigurable NAV/COM systems and to analyze their feasibility in realistic emergency scenarios. The article analyzes the proposed strategies and the most significant project results in pursuing both the global coverage of the emergency areas and the development of a reconfigurable and cooperative NAV/COM system.

Efficient Waveform Design for High-Bit-Rate W-band Satellite Transmissions

In the EHF (extremely high frequency) domain, W-band (75-110 GHz) offers promising perspectives for future satellite communications, mainly in terms of large bandwidth availability for high-bit-rate transmission. In this work an innovative physical (PHY) layer design for broadband satellite connections operating in W-band is proposed, which is based on the prolate spheroidal wave functions (PSWFs). PSWF waveforms (originally proposed in short-range indoor ultra-wideband communications) are aimed at optimizing the tradeoff between the concentration of pulse energy in a finite time interval and in a limited bandwidth. In our paper, PSWF-based 4-ary pulse shape modulation (PSM), characterized by a nearly optimal compromise between spectral and envelope compactness, has been tested for the radio interface of a W-band geostationary (GEO) downlink connection. The effect of nonlinear distortions, introduced by power-efficient saturating amplifiers, can be drastically reduced without any power back-off and will maintain a very good spectral efficiency. Experimental results obtained by means of realistic simulations fully demonstrate the potential advantages taken by PSWF in terms of increased spectral efficiency, link availability, and net payload rate with respect to state-of-the-art pulse-shaped modulations, raised-cosine filtered quadrature amplitude modulation (QAM), and Gaussian minimum shift keying (GMSK) commonly employed in satellite communications.

W‐band physical layer design issues in the context of the DAVID–DCE experiment

This paper aims at focusing on the aspects concerning the physical layer design for an innovative satellite communication experiment. Such an experiment, denoted by the acronym DAVID–DCE (Data and Video Interactive Distribution—Data Collection Experiment) is based on the exploitation of the W-band (75–110 GHz) for high-bit-rate satellite transmission. The potential advantages of using of the W-band are mainly related to the great bandwidth availability, and to the absence of interference. Moreover, an expected result of the experiment is a substantive improvement in the communication systems performances in the presence of meteorological phenomena (e.g. rain) as compared with the more conventional Ka-band satellite transmission. On the other hand, problems to be faced concern the non-ideal behaviours of hardware devices employed for high-frequency digital transmission. In particular, carrier recovery and timing recovery are the most crucial signal-processing tasks to be carefully considered in the design of the physical level of the system, because they considerably suffer from hardware impairments. The purpose of this work is to illustrate the proposed solutions in terms of the most critical modulation, demodulation and synchronization design issues, together with the effects of non-ideal behaviours of hardware components on BER performances. Copyright

Waveform design solutions for EHF broadband satellite communications

The problematic RF environment experienced by broadband satellite communications at EHF frequency bands, in particular Q/W bands, call for the use of novel waveforms. This paper presents a detailed comparison of several waveforms in presence of nonlinear distortions and typical values of phase noise introduced at Q/W band. Two main types of waveforms have been compared: Constant Envelope multicarrier waveforms (CE-OFDM and CE-SCFDMA) and single carrier impulse-based waveforms (TH-UWB, DS-UWB and PSWF-based PSM). This comparison will allow to draw some practical guidelines for the waveforms design of EHF broadband satellite communications.

Adaptive antenna array control in the presence of interfering signals with stochastic arrivals: assessment of a GA-based procedure

In this letter, a real-world working case of interfering signals coming to an antenna array with random arrivals modeled as a Poisson process is considered. A procedure based on a suitable genetic algorithm for adaptive array control is assessed by means of numerical simulations. Selected results clearly demonstrate the effectiveness and flexibility of the proposed procedure.