Giorgio Matteo VITETTA - personale UniMoRe

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Giorgio Matteo VITETTA

Professore Ordinario
Dipartimento di Ingegneria "Enzo Ferrari"

Pubblicazioni

2024 - Editorial: Advances in Shannon-based communications and computations approaches to understanding information processing in the brain [Articolo su rivista]
Tee, James; Vitetta, Giorgio Matteo
abstract

2023 - An Approximate Maximum Likelihood Method for the Joint Estimation of Range and Doppler of Multiple Targets in OFDM-Based Radar Systems [Articolo su rivista]
Mirabella, M.; Di Viesti, P.; Davoli, A.; Vitetta, G. M.
abstract

In this manuscript, an innovative method for the detection and the estimation of multiple targets in a radar system employing orthogonal frequency division multiplexing is illustrated. The core of this method is represented by a novel algorithm for detecting multiple superimposed two-dimensional complex tones in the presence of noise and estimating their parameters. This algorithm is based on a maximum likelihood approach and combines a single tone estimator with a serial cancellation procedure. Our numerical results lead to the conclusion that the developed method can achieve a substantially better accuracy-complexity trade-off than various related techniques in the presence of closely spaced targets.

2023 - Deep Learning for Parametric Channel Estimation in Massive MIMO Systems [Articolo su rivista]
Zia, Muhammad Umer; Xiang, Wei; Vitetta, Giorgio M.; Huang, Tao
abstract

Massive Multiple-Input Multiple-Output (MIMO) communication with a low bit error rate depends upon the availability of accurate Channel State Information (CSI) at the base station. The massive MIMO systems can be either deployed using time division duplexing with channel reciprocity assumption or by availing frequency division duplexing, which requires closed-loop feedback for CSI acquisition. The channel reciprocity simplifies transmission in time division duplexing; however, it suffers a bottleneck due to pilot contamination, whereas transmission in frequency division duplexing is challenged by channel estimation complexity, CSI feedback, and overall delay in CSI transfer. This paper proposes a simplified parametric channel model, its deep neural network aided estimation along with pilot decontamination for time division duplexing and a low rate parametric feedback and improved precoding for frequency division duplexing based massive MIMO systems. This novel framework integrates the massive MIMO parametric estimation and deep learning for improved estimation and precoding. Our proposed model also offers a unified approach for CSI acquisition with a performance bound on channel correlation in fast time-varying conditions. A theoretical model has been presented using Gaussian assumptions and validated by Monte-Carlo simulations. The results show total nullification of pilot contamination and high-performance gains when the proposed technique is employed for estimation.

2023 - Deterministic Algorithms for Four-Dimensional Imaging in Colocated MIMO OFDM-Based Radar Systems [Articolo su rivista]
Mirabella, M.; Di Viesti, P.; Vitetta, G. M.
abstract

In this manuscript, the problem of detecting multiple targets and jointly estimating their spatial coordinates (namely, the range, the Doppler and the direction of arrival of their electromagnetic echoes) in a colocated multiple-input multiple-output radar system employing orthogonal frequency division multiplexing is investigated. It is well known its optimal solution, namely the joint maximum likelihood estimator of an unknown number of targets, is unfeasible because of its huge computational complexity. Moreover, until now, sub-optimal solutions have not been proposed in the technical literature. In this manuscript a novel approach to the development of reduced complexity solutions is illustrated. It is based on the idea of separating angle estimation from range-Doppler estimation, and of exploiting known algorithms for solving these two sub-problems. A detailed analysis of the accuracy and complexity of various detection and estimation methods based on this approach is provided. Our numerical results evidence that one of these methods is able to approach optimal performance in the maximum likelihood sense with a limited computational effort in different scenarios.

2023 - Deterministic Signal Processing Techniques for OFDM-Based Radar Sensing: An Overview [Articolo su rivista]
Mirabella, M.; Di Viesti, P.; Davoli, A.; Vitetta, G. M.
abstract

In this manuscript, we analyze the most relevant classes of deterministic signal processing methods currently available for the detection and the estimation of multiple targets in a joint communication and sensing system employing orthogonal frequency division multiplexing. Our objective is offering a fair comparison of the available technical options in terms of required computational complexity and accuracy in both range and Doppler estimation. Our numerical results, obtained in various scenarios, evidence that distinct algorithms can achieve a substantially different accuracy-complexity trade-off.

2023 - Novel Movement-Based Methods for the Calibration of Colocated Multiple-Input Multiple-Output Radars [Articolo su rivista]
Guerzoni, G.; Faghand, E.; Vitetta, G. M.; Vincenzi, L.; Mehrshahi, E.
abstract

2023 - Radar-Based Monitoring of Vital Signs: A Tutorial Overview [Articolo su rivista]
Paterniani, G; Sgreccia, D; Davoli, A; Guerzoni, G; Di Viesti, P; Valenti, Ac; Vitolo, M; Vitetta, Gm; Boriani, G
abstract

In the last years, substantial attention has been paid to the use of radar systems in health monitoring, due to the availability of both low-cost radar devices and computationally efficient algorithms for processing their measurements. In this article, a tutorial overview of radar-based monitoring of vital signs is provided. More specifically, we first focus on the available radar technologies and the signal processing algorithms developed for the estimation of vital signs. Then, we provide some useful guidelines that should be followed in the selection of radar devices for vital sign monitoring and in their use. Finally, we illustrate various specific applications of radar systems to health monitoring and some relevant research trends in this field.

2023 - Recursive Algorithms for the Estimation of Multiple Superimposed Undamped Tones and Their Application to Radar Systems [Articolo su rivista]
Viesti, Pasquale Di; Davoli, Alessandro; Guerzoni, Giorgio; Vitetta, Giorgio M.
abstract

In this article, two recursive algorithms for the detection of multiple superimposed tones in noise and the estimation of their parameters are derived. They are based on a maximum likelihood approach and combine an innovative single-tone estimator with a serial cancellation procedure. Our numerical results lead to the conclusion that the developed methods can achieve a substantially better accuracy–complexity tradeoff than various related techniques in the presence of multiple closely spaced tones. Moreover, they can be exploited to detect multiple closely spaced targets and estimate their spatial coordinates in multiple-input multiple-output frequency-modulated continuous wave radar systems.

2022 - Novel Deterministic Detection and Estimation Algorithms for Colocated Multiple-Input Multiple-Output Radars [Articolo su rivista]
Di Viesti, Pasquale; Davoli, Alessandro; Guerzoni, Giorgio; Vitetta, Giorgio M.
abstract

In this manuscript, the problem of detecting multiple targets and estimating their spatial coordinates (namely, their range and the direction of arrival of their electromagnetic echoes) in a colocated multiple-input multiple-output radar system operating in a static or slowly changing two-dimensional or three-dimensional propagation scenario is investigated. Various solutions, collectively called range & angle serial cancellation algorithms , are developed for both frequency modulated continuous wave radars and stepped frequency continuous wave radars. Moreover, specific technical problems experienced in their implementation are discussed. Finally, the accuracy achieved by these algorithms in the presence of multiple targets is assessed on the basis of both synthetically generated data and of the measurements acquired through three different multiple-input multiple-output radars and is compared with that provided by other methods based on multidimensional Fourier analysis and multiple signal classification.

2021 - A Mathematical Description of Emotional Processes and Its Potential Applications to Affective Computing [Articolo su rivista]
Puviani, Luca; Rama, Sidita; Vitetta, Giorgio Matteo
abstract

In affective computing, machines should detect and recognize human emotions, and adapt their behavior to them. Nowadays these objectives are mainly achieved through the exploitation of machine learning techniques. These techniques are employed to process different emotional-related features and to produce classification labels or coordinates in a valence-arousal space. This approach, however, ignores the neurophysiological processes governing implicit emotional states and, consequently, suffers from substantial limitations. Moreover, machine learning methods employed today do not benefit from the knowledge of emotional dynamics for properly adapting themselves. In this manuscript, starting from recent neuroscience and computational theories, we show how a simple mathematical description of processes governing implicit emotional dynamics can be developed. Moreover, we discuss how our mathematical models can be exploited to improve tracking, estimation and active modulation of human emotions.

2021 - Machine Learning and Deep Learning Techniques for Colocated MIMO Radars: A Tutorial Overview [Articolo su rivista]
Davoli, A.; Guerzoni, G.; Vitetta, G. M.
abstract

Radars are expected to become the main sensors in various civilian applications, ranging from health-care monitoring to autonomous driving. Their success is mainly due to the availability of both low cost integrated devices, equipped with compact antenna arrays, and computationally efficient signal processing techniques. An increasingly important role in the field of radar signal processing is played by machine learning and deep learning techniques. Their use has been first taken into consideration in human gesture and motion recognition, and in various healthcare applications. More recently, their exploitation in object detection and localization has been also investigated. The research work accomplished in these areas has raised various technical problems that need to be carefully addressed before adopting the above mentioned techniques in real world radar systems. In this manuscript, a comprehensive overview of the machine learning and deep learning techniques currently being considered for their use in radar systems is provided. Moreover, some relevant open problems and current trends in this research area are analysed. Finally, various numerical results, based on both synthetically generated and experimental datasets, and referring to two different applications are illustrated. These allow readers to assess the efficacy of specific methods and to compare them in terms of accuracy and computational effort.

2021 - Rail Diagnostics Based on Ultrasonic Guided Waves: An Overview [Articolo su rivista]
Bombarda, D.; Vitetta, G. M.
abstract

Rail tracks undergo massive stresses that can affect their structural integrity and produce rail breakage. The last phenomenon represents a serious concern for railway management authorities, since it may cause derailments and, consequently, losses of rolling stock material and lives. Therefore, the activities of track maintenance and inspection are of paramount importance. In recent years, the use of various technologies for monitoring rails and the detection of their defects has been investigated; however, despite the important progresses in this field, substantial research efforts are still required to achieve higher scanning speeds and improve the reliability of diagnostic procedures. It is expected that, in the near future, an important role in track maintenance and inspection will be played by the ultrasonic guided wave technology. In this manuscript, its use in rail track monitoring is investigated in detail; moreover, both of the main strategies investigated in the technical literature are taken into consideration. The first strategy consists of the installation of the monitoring instrumentation on board a moving test vehicle that scans the track below while running. The second strategy, instead, is based on distributing the instrumentation throughout the entire rail network, so that continuous monitoring in quasi-real-time can be obtained. In our analysis of the proposed solutions, the prototypes and the employed methods are described.

2020 - Multiple Bayesian Filtering as Message Passing [Articolo su rivista]
Vitetta, Giorgio M.; DI VIESTI, Pasquale; Sirignano, Emilio; Montorsi, Francesco
abstract

In this manuscript, a general method for deriving filtering algorithms that involve a network of interconnected Bayesian filters is proposed. This method is based on the idea that the processing accomplished inside each of the Bayesian filters and the interactions between them can be represented as message passing algorithms over a proper graphical model. The usefulness of our method is exemplified by developing new filtering techniques, based on the interconnection of a particle filter and an extended Kalman filter, for conditionally linear Gaussian systems. Numerical results for two specific dynamic systems evidence that the devised algorithms can achieve a better complexity-accuracy tradeoff than marginalized particle filtering and multiple particle filtering.

2020 - Three-Dimensional Deterministic Detection and Estimation Algorithms for MIMO SFCW Radars [Relazione in Atti di Convegno]
Davoli, Alessandro; Sirignano, Emilio; Vitetta, Giorgio M.
abstract

In this paper, the problem of detection and joint estimation of range, azimuth and elevation of multiple targets in a multiple-input multiple-output stepped-frequency continuous wave radar system is investigated. Two iterative deterministic algorithms are illustrated and their accuracy is assessed on the basis of the raw data acquired from a commercial radar device. Our results evidence that these algorithms achieve similar accuracies, but at the price of substantially different computational efforts.

2019 - A Comparative Analysis of Deterministic Detection and Estimation Techniques for MIMO SFCW Radars [Articolo su rivista]
Sirignano, Emilio; Davoli, Alessandro; Vitetta, Giorgio M.; Viappiani, Federico
abstract

In this paper, the problem of the joint estimation of the range and azimuth of multiple targets in a multiple-input multiple-output stepped-frequency continuous wave radar system is investigated. Three deterministic algorithms solving it through an iterative beam cancellation procedure are described; moreover, an iterative technique, based on the expectation-maximization algorithm, is developed with the aim of refining their estimates. The accuracy achieved by all the considered algorithms is assessed on the basis of the raw data acquired from a low power wideband radar device. Our results evidence that these algorithms achieve similar accuracies, but at the price of different computational efforts.

2019 - AUTONOMOUS DRIVING SYSTEM THROUGH ROWS OF A PLANTATION [Brevetto]
Davoli, Alessandro; DI CECILIA, Luca; DI VIESTI, Pasquale; Ferrari, Luca; Guerzoni, Giorgio; Sirignano, Emilio; Vitetta, Giorgio Matteo
abstract

2019 - Double Bayesian Smoothing as Message Passing [Articolo su rivista]
Di Viesti, Pasquale; Vitetta, Giorgio Matteo; Sirignano, Emilio
abstract

Recently, a novel method for developing filtering algorithms, based on the interconnection of two Bayesian filters and called double Bayesian filtering, has been proposed. In this manuscript we show that the same conceptual approach can be exploited to devise a new smoothing method, called double Bayesian smoothing. A double Bayesian smoother combines a double Bayesian filter, employed in its forward pass, with the interconnection of two backward information filters used in its backward pass. As a specific application of our general method, a detailed derivation of double Bayesian smoothing algorithms for conditionally linear Gaussian systems is illustrated. Numerical results for two specific dynamic systems evidence that these algorithms can achieve a better complexity-accuracy tradeoff and tracking capability than other smoothing techniques recently appeared in the literature.

2019 - Gait-Based Diplegia Classification Using LSMT Networks [Articolo su rivista]
Ferrari, Alberto; Bergamini, Luca; Guerzoni, Giorgio; Calderara, Simone; Bicocchi, Nicola; Vitetta, Giorgio; Borghi, Corrado; Neviani, Rita; Ferrari, Adriano
abstract

Diplegia is a specific subcategory of the wide spectrum of motion disorders gathered under the name of cerebral palsy. Recent works proposed to use gait analysis for diplegia classification paving the way for automated analysis. A clinically established gait-based classification system divides diplegic patients into 4 main forms, each one associated with a peculiar walking pattern. In this work, we apply two different deep learning techniques, namely, multilayer perceptron and recurrent neural networks, to automatically classify children into the 4 clinical forms. For the analysis, we used a dataset comprising gait data of 174 patients collected by means of an optoelectronic system. The measurements describing walking patterns have been processed to extract 27 angular parameters and then used to train both kinds of neural networks. Classification results are comparable with those provided by experts in 3 out of 4 forms.

2019 - Marginalized Particle Filtering and Related Filtering Techniques as Message Passing [Articolo su rivista]
Vitetta, Giorgio M.; Sirignano, Emilio; DI VIESTI, Pasquale; Montorsi, Francesco; Sola, Matteo
abstract

In this paper, a factor graph approach is employed to investigate the recursive filtering problem for conditionally linear Gaussian state-space models. First, we derive a new factor graph for the considered filtering problem; then, we show that applying the sum-product rule to our graphical model results in both known and novel filtering techniques. In particular, we prove that: 1) marginalized particle filtering can be interpreted as a form of forward only message passing over the devised graph; 2) novel filtering methods can be easily developed by exploiting the graph structure and/or simplifying probabilistic messages.

2019 - SYSTEM AND METHOD FOR LOCATING A TRAILER WITH RESPECT TO AN AGRICULTURAL MACHINE [Brevetto]
POSSELIUS JOHN, H; Ferrari, Luca; Lenzini, Nicola; Bonfiglio, Andrea; Rovati, Luigi; Vitetta, Giorgio Matteo
abstract

2018 - Equalization of Narrowband Indoor Powerline Channels for High Data Rate OFDM Communications [Articolo su rivista]
Pancaldi, Fabrizio; Gianaroli, Fabio; Vitetta, Giorgio Matteo
abstract

In this paper the well known Zadeh’s series representation of a linear periodically time varying system is exploited to develop linear equalization techniques for narrowband powerline communications based on orthogonal frequency division multiplexing. Numerical and experimental results referring to the band 200-500 kHz evidence that a coherent receiver exploiting the proposed equalizers can significantly outperform both its counterpart based on conventional channel estimation/ equalization techniques and differential detection with a limited complexity. This leads to the conclusion that a coherent receiver incorporating the proposed equalization techniques represents a technically appealing solution for narrowband high data rate powerline communications in indoor scenarios.

2018 - On the application of support vector machines to the prediction of propagation losses at 169 MHz for smart metering applications [Articolo su rivista]
Martino Uccellari, Author(s):; Facchini, Francesca; Sola, Matteo; Sirignano, Emilio; Vitetta, Giorgio M.; Barbieri, Andrea; Tondelli, Stefano
abstract

Recently, the need of deploying new wireless networks for smart gas metering has raised the problem of radio planning in the 169 MHz band. Unluckily, software tools commonly adopted for radio planning in cellular communication systems cannot be employed to solve this problem because of the substantially lower transmission frequencies characterising this application. In this study, a novel data-centric solution, based on the use of support vector machine techniques for classification and regression, is illustrated. The proposed method requires the availability of a limited set of received signal strength measurements and the knowledge of a three-dimensional map of the propagation environment of interest and generates both an estimate of the coverage area and a prediction of the field strength within it. Various numerical results show that the proposed method is able to achieve good accuracy at the price of an acceptable computational cost and of a limited effort for the acquisition of measurements in the considered environments.

2018 - Particle Smoothing for Conditionally Linear Gaussian Models as Message Passing Over Factor Graphs [Articolo su rivista]
Vitetta, G. M.; Sirignano, E.; Montorsi, F.
abstract

In this paper, the fixed-lag smoothing problem for conditionally linear Gaussian state-space models is investigated from a factor graph perspective. More specifically, after formulating Bayesian smoothing for an arbitrary state-space model as a forward–backward message passing over a factor graph, we focus on the above-mentioned class ofmodels and derive two novel particle smoothers for it. Both the proposed techniques are based on the well-known two-filter smoothing approach and employ marginalized particle filtering in their forward pass. However, on the one hand, the first smoothing technique can only be employed to improve the accuracy of state estimates with respect to that achieved by forward filtering. On the other hand, the second method, that belongs to the class of Rao–Blackwellized particle smoothers, also provides a pointmass approximation of the so-called joint smoothing distribution. Finally, our smoothing algorithms are compared, in terms of estimation accuracy and computational requirements, with a Rao–Blackwellized particle smoother recently proposed by Lindsten et al. (“Rao–Blackwellized particle smoothers for conditionally linear Gaussian models,” IEEE J. Sel. Topics Signal Process., vol. 10, no. 2, pp. 353–365, 2016).

2017 - A novel message passing algorithm for online Bayesian filtering: Turbo filtering [Relazione in Atti di Convegno]
Vitetta, Giorgio M.; Sirignano, Emilio; Montorsi, Francesco
abstract

In this manuscript a novel online technique for Bayesian filtering, dubbed turbo filtering, is illustrated. In particular, it is shown that this filtering method, which can be interpreted as an extension of marginalized particle filtering, results from the application of the sum-product rule to a factor graph representing a mixed linear/nonlinear state-space model. Simulation results for a specific state-space model evidence that turbo filtering can outperform marginalized particle filtering in terms of both accuracy and complexity.

2017 - On the performance of 169 MHz WM-Bus and 868 MHz LoRa technologies in smart metering applications [Relazione in Atti di Convegno]
Facchini, Francesca; Vitetta, Giorgio M.; Losi, Alessandro; Ruscelli, Fabio
abstract

In this manuscript the use of 169 MHz Wireless Meter-Bus and 868 MHz Semtech Long Range technologies in smart metering is investigated. Our study is based on a set of experimental results, acquired in various measurement campaigns. A description of the employed measurement tools and of our measurement campaigns is provided first. Then, some preliminary indications about the packet error rate estimated within the coverage area in different scenarios are illustrated. These results show that, on the one hand, the considered technologies perform similarly at the same transmission power in urban scenarios; on the other hand, Long Range outperforms Wireless Meter-Bus in suburban scenarios.

2017 - Signal Processing and Machine Learning for Diplegia Classification [Relazione in Atti di Convegno]
Bergamini, Luca; Calderara, Simone; Bicocchi, Nicola; Ferrari, Alberto; Vitetta, Giorgio
abstract

Diplegia is one of the most common forms of a broad family of motion disorders named cerebral palsy (CP) affecting the voluntary muscular system. In recent years, various classification criteria have been proposed for CP, to assist in diagnosis, clinical decision-making and communication. In this manuscript, we divide the spastic forms of CP into 4 other categories according to a previous classification criterion and propose a machine learning approach for automatically classifying patients. Training and validation of our approach are based on data about 200 patients acquired using 19 markers and high frequency VICON cameras in an Italian hospital. Our approach makes use of the latest deep learning techniques. More specifically, it involves a multi-layer perceptron network (MLP), combined with Fourier analysis. An encouraging classification performance is obtained for two of the four classes.

2016 - A Bayesian Demand-Side Management Strategy for Smart Micro-Grid [Articolo su rivista]
Sola, Matteo; Vitetta, Giorgio Matteo
abstract

In this manuscript a novel strategy for distributed and autonomous demand-side energy management among users of a low-voltage micro-grid is developed. Its derivation is based on: a) modelling the energy consumption scheduling of the shiftable loads that belong to a given user as a noncooperative two-player game of incomplete information, in which the user itself plays against an opponent collecting all the other users of the same micro-grid; b) assuming that each user is endowed with statistical information about its behavior and that of its opponent, so that it can choose actions maximising its expected utility. Numerical results evidence the efficacy of the proposed strategy when employed to manage the charging of electric vehicles in a micro-grid.

2016 - Bit and Power Loading for Narrowband Indoor Powerline Communications [Articolo su rivista]
Pancaldi, Fabrizio; Gianaroli, Fabio; Vitetta, Giorgio Matteo
abstract

The problem of bit and power loading for bit rate maximization in orthogonal frequency division multiplexing data communications over indoor powerline channels is investigated, and a simple method for bit/power allocation in half a cycle of the mains is developed. The proposed solution is based on the so-called Zadeh's representation for modeling the linear periodically time-varying behavior of powerline channels. Numerical results show the superiority of the proposed method over other solutions available in the technical literature in a real-world scenario.

2016 - Computational Psychiatry and Psychometrics Based on Non-Conscious Stimuli Input and Pupil Response Output [Articolo su rivista]
Puviani, Luca; Rama, Sidita; Vitetta, Giorgio Matteo
abstract

It is well known from the technical literature that non-conscious perception of emotional stimuli affects behavior, perception, and even decision making [e.g., see Ref. (1) for a comprehensive review]. Non-conscious perception can be obtained by inducing sensory unawareness, e.g., through backward masking and binocular rivalry (1). Experiments adopting such paradigms have evidenced that non-consciously perceived emotional stimuli elicit activity in the amygdala, superior colliculus, basal ganglia, and pulvinar. More specifically, it has been shown that a subcortical fast route exists between the thalamus and the amygdala, which, in turn, project onto different cortical and subcortical structures [e.g., onto the nucleus accumbens, NAcc, when appetitive stimuli are perceived (2)]. These findings agree with the hypothesis about amygdala functionality proposed by LeDoux (3, 4). In fact, LeDoux has hypothized the existence of a thalamic pathway to the amygdala; such a pathway would allow to automatically detect evolutionary prepared visual stimuli (such as emotional faces, sexual-related stimuli, spiders, snakes, and injuries). Note that this model is also supported by other results acquired by different researchers that have employed masking in normal participants (5, 6) or have observed brain activity in patients affected by cortical blindness (7, 8). According to this model about amygdala functionality, the superior colliculus stimulates the pulvinar nucleus of the thalamus, which then arouses the amygdala (4, 9, 10). This suggests that salient features representing biologically prepared stimuli could be stored in the amygdala since birth. From an evolutionary perspective, this can be related to the fact that fast and implicit (or unconscious) reactions are needed in dangerous and highly dynamical environments. Moreover, even ontogenetic stimuli (e.g., weapons) are encoded within the amygdala through implicit learning during life (11, 12). These data evidence the importance of subcortical regions associated with implicit emotional processing. In fact, since the brain structure works like a hierarchical network (13) in which the limbic system represents a lower hierarchical level with respect to the higher cortical structure, it is likely that the overall perception and emotional appraisal are influenced by low-level evaluations. More specifically, the signals coming from lower and higher hierarchical levels determine prediction errors (or error signals) at intermediate levels; such error signals propagate through the entire hierarchical structure, determining cognitive perception, causes attributions, emotional evaluations, actions, and behaviors (14). Hence, if subcortical limbic-brainstem regions are defective, all the network hierarchy functioning will be compromised. As a matter of fact, a dysfunction in the limbic-brainstem regions is associated with various psychiatric disorders with higher cognitive deficits including autism, schizophrenia, posttraumatic stress disorders (PTSD), attention deficits/hyperactivity disorder (ADHD), neurosis, phobia, and others.

2016 - On the use of support vector machines for the prediction of propagation losses in smart metering systems [Relazione in Atti di Convegno]
Uccellari, Martino; Facchini, Francesca; Sola, Matteo; Sirignano, Emilio; Vitetta, Giorgio M.; Barbieri, Andrea; Tondelli, Simona
abstract

In this manuscript a novel data-centric solution, based on the use of support vector machine techniques, is proposed to solve the problem of radio planning in the 169 MHz band. Our method requires the availability of a limited set of received signal strength measurements and the knowledge of a three-dimensional map of the propagation environment of interest, and generates both an estimate of the coverage area and a prediction of the field strength within it. Our numerical results evidence that our method is able to achieve a good accuracy at the price of an acceptable computational cost and of a limited effort for the acquisition of measurements.

2015 - A novel bit and power loading algorithm for narrowband indoor powerline communications [Relazione in Atti di Convegno]
Gianaroli, Fabio; Pancaldi, Fabrizio; Vitetta, Giorgio Matteo
abstract

The problem of bit and power loading for bit rate maximization in OFDM data communications over indoor powerline channels is investigated and a simple method for bit/power allocation in a single cycle of the mains is developed. The proposed solution is based on the so called Zadeh's representation for modelling the linear periodically time-varying behavior of powerline channels. Numerical results show the superiority of the proposed method over other solutions available in the technical literature in a real world scenario.

2015 - Reduced-Complexity Algorithms for Indoor Map-Aware Localization Systems [Articolo su rivista]
Pancaldi, Fabrizio; Montorsi, Francesco; Vitetta, Giorgio Matteo
abstract

The knowledge of environmental maps (i.e., map-awareness) can appreciably improve the accuracy of optimal methods for position estimation in indoor scenarios. This improvement, however, is achieved at the price of a significant complexity increase with respect to the case of map-unawareness, specially for large maps. This is mainly due to the fact that optimal map-aware estimation algorithms require integrating highly nonlinear functions or solving nonlinear and nonconvex constrained optimization problems. In this paper, various techniques for reducing the complexity of such estimators are developed. In particular, two novel strategies for restricting the search domain of map-aware position estimators are developed and the exploitation of state-of-the-art numerical integration and optimization methods is investigated; this leads to the development of a new family of suboptimal map-aware localization algorithms. Our numerical and experimental results evidence that the accuracy of these algorithms is very close to that offered by their optimal counterparts, despite their significantly lower computational complexity.

2015 - Reduced-complexity techniques for indoor map-aware localization [Relazione in Atti di Convegno]
Montorsi, Francesco; Pancaldi, Fabrizio; Vitetta, Giorgio Matteo
abstract

In this manuscript new reduced complexity localization algorithms exploiting received signal strength measurements and based on the indoor map-aware statistical models illustrated in [1] are developed. Such algorithms exploit search domain reduction techniques and state of the art methods for numerical integration and optimization. Our numerical and experimental results evidence that theirs accuracy is very close to that offered by their optimal counterparts, in spite of their substantially lower computational complexity.

2014 - Demand-side management in a smart micro-grid: A distributed approach based on Bayesian game theory [Relazione in Atti di Convegno]
Sola, Matteo; Vitetta, Giorgio Matteo
abstract

In this manuscript a novel strategy for distributed and autonomous demand-side energy management among users of a low-voltage micro-grid is developed. Its derivation is based on: a) modelling the energy consumption scheduling of the shiftable loads that belong to a given user as a noncooperative two-player game of incomplete information, in which the user himself plays against an opponent collecting all the other users of the same micro-grid; b) assuming that each user is endowed with statistical information about his behavior and that of its opponent, so that he can choose actions maximising his expected utility. Numerical results evidence the efficacy of the proposed strategy when employed to manage the charging of electric vehicles in a micro-grid.

2014 - Design and Implementation of a Wideband Channel Sounder for Low-Voltage Powerlines [Articolo su rivista]
Gianaroli, Fabio; Pancaldi, Fabrizio; Vitetta, Giorgio Matteo
abstract

Estimating the input-output behavior of low voltage powerline channels for indoor high speed data communications requires the availability of proper wideband channel sounding tools. In fact, the properties of real world powerline channels are substantially different from those commonly exhibited by their wireless counterparts, so that standard methods for wireless channel sounding cannot be adapted to a powerline scenario. In this paper, after providing some general design guidelines for powerline channel sounding, a detailed description of a FPGA-based implementation of a wideband powerline channel sounder is provided. Such a tool is based on low cost hardware and is flexible, since it can be easily customized to user needs using a set of simple graphical user interfaces. Some of its specific applications, namely the estimation of the time-varying transfer function of an indoor powerline channel and the evaluation of the power spectral density of the noise affecting it, are illustrated to show the potentialities of the developed equipment.

2014 - Map-aware models for indoor wireless localization systems: an experimental study [Articolo su rivista]
Montorsi, Francesco; Pancaldi, Fabrizio; Vitetta, Giorgio Matteo
abstract

The accuracy of indoor wireless localization systems can be substantially enhanced by map-awareness, i.e., by the knowledge of the map of the environment in which localization signals are acquired. In fact, this knowledge can be exploited to cancel out, at least to some extent, the signal degradation due to propagation through physical obstructions, i.e., to the so called non-line-of-sight bias. This result can be achieved by developing novel localization techniques that rely on proper map-aware statistical modelling of the measurements they process. In this manuscript a unified statistical model for the measurements acquired in map-aware localization systems based on time-of-arrivaland received signal strength techniques is developed and its experimental validation is illustrated. Finally, the accuracy of the proposed map-aware model is assessed and compared with that offered by its map-unaware counterparts. Our numerical results show that, when the quality of acquired measurements is poor, map-aware modelling can enhance localization accuracy by up to 110% in certain scenarios.

2014 - On the Use of Zadeh's Series Expansion for Modeling and Estimation of Indoor Powerline Channels [Articolo su rivista]
Gianaroli, Fabio; Pancaldi, Fabrizio; Vitetta, Giorgio Matteo
abstract

Indoor powerline channels usually exhibit a cyclic input–output behavior due to the time-varying impedance of power loads. This makes typical time-invariant system models unsuitable to provide a faithful representation of such channels. In this paper, starting from the so-called Zadeh's series expansion, a discrete-time parametric representation of a linear periodically time-varying system is developed, and it is shown how a reduced-complexity version of it can be adopted to model indoor powerline channels. Then, various methods for estimating the parameters of the proposed representation are developed and compared in terms of performance and complexity. Numerical results evidence that our reduced complexity model is able to provide an accurate representation of indoor powerline channels and is of practical interest for both smart-grid applications and home area networks.

2014 - The Impact of Statistical Noise Modeling on the Error-Rate Performance of OFDM Power-Line Communications [Articolo su rivista]
Gianaroli, Fabio; Pancaldi, Fabrizio; Vitetta, Giorgio Matteo
abstract

In this paper, the impact of statistical noise modelling on the error performance achieved by orthogonal frequency-division multiplexing (OFDM) over indoor broadband power-line channels is investigated. Different classes of statistical models suitable to represent power-line noise are illustrated and their impact on the error performance of a specific OFDM system is assessed via computer simulations. Numerical results are compared with the error performance provided by the same system in the presence of measured power-line noise; this is evidence that a realistic indication of error performance can be achieved only if the power spectral density of the adopted noise model exhibits a good match with that of the measured noise. In practice, this result can be achieved by modeling the power-line noise as a moving average random process of proper order; however, a satisfying match can be achieved as well if other simple noise models available in the technical literature are adopted.

2013 - Broadband system models based on Zadeh's representation for indoor powerline channels: An experimental validation [Relazione in Atti di Convegno]
Gianaroli, Fabio; Pancaldi, Fabrizio; Vitetta, Giorgio Matteo
abstract

The discrete-time representation of a broadband powerline channel as a linear periodically time variant system poses serious problems in terms of computational complexity. In this paper we exploit the principles of the Zadeh's series expansion to devise a new discrete-time system model, characterized by a limited computational complexity and particularly suitable for an implementation on embedded programmable hardware. Then, we illustrate simple methods for estimating the parameters of the proposed model and apply them to the development of a broadband channel sounding tool for powerlines. Our experimental and numerical results show that the proposed model is able to provide a faithful representation of the periodically time varying behavior of indoor powerline channels.

2013 - Design and implementation of an inertial navigation system for pedestrians based on a low-cost MEMS IMU [Relazione in Atti di Convegno]
Montorsi, Francesco; Pancaldi, Fabrizio; Vitetta, Giorgio Matteo
abstract

Inertial navigation systems for pedestrians are infrastructure-less and can achieve sub-meter accuracy in the short/medium period. However, when low-cost inertial measurement units (IMU) are employed for their implementation, they suffer from a slowly growing drift between the true pedestrian position and the corresponding estimated position. In this paper we illustrate a novel solution to mitigate such a drift by: a) using only accelerometer and gyroscope measurements (no magnetometers required); b) including the sensor error model parameters in the state vector of an extended Kalman filter; c) adopting a novel soft heuristic for foot stance detection and for zero-velocity updates. Experimental results evidence that our inertial-only navigation system can achieve similar or better performance with respect to pedestrian dead-reckoning systems presented in related studies, although the adopted IMU is less accurate than more expensive counterparts.

2013 - Map-aware RSS localization models and algorithms based on experimental data [Relazione in Atti di Convegno]
Montorsi, F.; Pancaldi, F.; Vitetta, G. M.
abstract

The knowledge of the propagation environment can greatly improve the performance of indoor wireless localization systems, since it can be exploited to cancel out, at least to some extent, the effects of physical obstructions (e.g., walls) degrading the radio signals employed for localization. In indoor localization systems, the propagation environment can be described by maps (e.g., floor plans), which represent a valuable source of knowledge. In this paper a new map-aware statistical model for the measurements acquired in wireless localization systems based on received signal strength is proposed. Experimental results are processed to extract the parameters of the proposed model, which is then exploited to devise map-aware localization algorithms; these are capable of mitigating the non-line-of-sight bias introduced in the measurements by the obstructions modelled by the map. Our numerical results evidence that map-aware modelling can substantially improve localization accuracy in indoor scenarios with respect to map-unaware modelling. © 2013 IEEE.

2013 - On the impact of a priori information on localization accuracy and complexity [Relazione in Atti di Convegno]
Montorsi, Francesco; S., Mazuelas; Vitetta, Giorgio Matteo; M., Win
abstract

Accuracy and complexity represent fundamental aspects of localization and tracking systems. In this manuscript the impact of a priori knowledge about agent position on the accuracy and the complexity of localization algorithms is investigated. In particular, first Cramer-Rao bounds on localization accuracy are derived under the assumption that a priori information is described by a map restricting the agent position to a specific region. Then, the computational complexity of optimal map-aware and map-unaware localization techniques is assessed. Our results evidence that: a) map-aware localization accuracy can be related to some geometrical features of the map but usually exhibits a complicated dependence on them; b) in some scenarios map-aware localization algorithms provide better accuracy than their map-unaware counterparts at comparable computational complexity.

2013 - On the Performance Limits of Map-Aware Localization [Articolo su rivista]
Montorsi, Francesco; S., Mazuelas; Vitetta, Giorgio Matteo; M. Z., Win
abstract

Establishing bounds on the accuracy achievable by localization techniques represents a fundamental technical issue. Bounds on localization accuracy have been derived for cases in which the position of an agent is estimated on the basis of a set of observations and, possibly, of some a priori information related to them (e.g., information about anchor positions and properties of the communication channel). In this paper, new bounds are derived under the assumption that the localization system is map-aware, i.e., it can benefit not only from the availability of observations, but also from the a priori knowledge provided by the map of the environment where it operates. Our results show that: a) map-aware estimation accuracy can be related to some features of the map (e.g., its shape and area) even though, in general, the relation is complicated; b) maps are really useful in the presence of some combination of low SNRs and specific geometrical features of the map (e.g., the size of obstructions); c) in most cases, there is no need of refined maps since additional details do not improve estimation accuracy.

2013 - The Impact of Load Characterization on the Average Properties of Statistical Models for Powerline Channels [Articolo su rivista]
Gianaroli, Fabio; Pancaldi, Fabrizio; Vitetta, Giorgio Matteo
abstract

In this paper the impact of load characterization on the statistical modeling of indoor powerline channels is investigated in the bandwidth 100 kHz–50 MHz. Our analysis refers to the mean properties of such channels (so that their time-varying features are ignored) and is based on: a) the use of the statistical channel simulator, which has beenvalidated through experimental measurements, described in [23]; b) the availability of a set of experimental results about the impedance of various appliances. Our numerical and experimental results evidence that, on the one hand,for frequencies beyond 20 MHz the inﬂuence of load characterization on the accuracy of statistical channel modelling is marginal; however, on the other hand, for frequencies in the order of 0–20 MHz the properties of the loads connected to a power network can appreciably affect the properties of the channel model.

2013 - Wireless Communications: Algorithmic Techniques [Monografia/Trattato scientifico]
Vitetta, Giorgio Matteo; D. P., Taylor; Colavolpe, Giulio; Pancaldi, Fabrizio; P. A., Martin
abstract

Digital radios have undergone an astonishing evolution in the last century. Born as a set of simple and power-hungry electrical and electromechanical devices for low data rate transmission of telegraph data in the Marconi age, they have transformed, thanks to substantial advances in electronic technology, into a set of small, reliable and sophisticated integrated devices supporting broadband multimedia communications. This, however, would not have been possible unless significant progress had been made in recent decades in the field of signal processing algorithms for baseband and passband signals. In fact, the core of any modern digital radio consists of a set of algorithms running over programmable electronic hardware. This book stems from the research and teaching activities of its co-authors in the field of algorithmic techniques for wireless communications. A huge body of technical literature has accumulated in the last four decades in this area, and an extensive coverage of all its important aspects in a single textbook is impossible. For this reason, we have selected a few important topics and, for ease of reading, organized them into two parts. Part I concerns digital modulation techniques, characterization and modeling of wireless channels, channel estimation, and channel equalization metrics and algorithms. Part II focuses on channel coding, coded modulation, and combined equalization and decoding. For each of these topics, we have tried to provide an advanced introduction, blending basic principles with advanced concepts and techniques which play an important role at the forefront of research in wireless communications. In addition, for each topic we have provided some historical notes, so that the reader can analyze it in the right perspective, understanding both its roots and its possible evolutionary paths. From the outset our main goal has been to produce a textbook for beginning graduate and senior students, who are expected to have some basic knowledge in the fields of Fourier transform techniques, probability theory, random processes, sampling theory, linear filtering, vector spaces, matrix algebra and linear transformations. Some information about more advanced concepts in these fields is provided in the appendices of the book, which, for this reason, we believe to be self-contained. This book can serve as a text in either one-semester or two-semester courses in digital communications and coding. A natural division is to cover Part I in the first semester and Part II in the second. An alternative one-semester course can cover a portion of the material of Part I (Chapters 1–4 and 6) and some basic material from Part II (Chapters 7–9). The writing of this book has required a substantial commitment. We owe much to all those people who volunteered to read parts of it, correct mistakes and provide suggestions for enriching its technical content and improving its clarity of presentation. In particular, we are grateful Francesco Montorsi, Fabio Gianaroli, Tommaso Foggi, Amina Piemontese, Nicolò Mazzali, Andrea Modenini and Alessandro Ugolini for their contributions. Our sincere thanks go also to the editorial staff of Wiley and, in particular, to Mark Hammond, Sarah Hinton, Jennifer Beal, and Susan Barclay, who have always supported us in the writing process. We do hope that the uncountable hours devoted to this book will bear fruit in stimulating interest in the study of modern techniques for wireless communications.

2012 - Statistical Modeling of Periodic Impulsive Noise in Indoor Power-Line Channels [Articolo su rivista]
Gianaroli, Fabio; Pancaldi, Fabrizio; E., Sironi; Vigilante, Marco; Vitetta, Giorgio Matteo; Barbieri, Alessandro
abstract

In this paper, novel statistical models for the representation of the periodic impulsive noise generated by power loads connected to power grids in indoor scenarios are developed. Their derivation is based on a set of experimental results acquired in a measurement campaign and on deseasonalized autoregressive moving average modeling of cyclostationary random processes. Numerical results are evidence that the proposed models can provide an accurate stochastic representation of the periodic impulsive noise generated by specific appliances in the 1–30 MHz band, at the price of limited computational complexity.

2011 - A Novel Ultrawideband System for Multiuser Data Communications [Articolo su rivista]
Barbieri, A.; Pancaldi, Fabrizio; Vitetta, Giorgio Matteo
abstract

In this paper, a novel ultrawideband system for multiuser data communications is proposed. In this system multiple users are allowed to transmit on-off keying modulated signals in the same time intervals and exploiting the same frequency subband. Time/frequency overlapped data frames sent by distinct users include low data rate training sequences characterized by different repetition periods. This transmission strategy, known as rate division multiple access in the technical literature, allows to ease two fundamental tasks at the receive side, namely joint channel estimation and timing synchronization. Channel estimates are exploited by a multiuser detector based on a zero forcing equalizer. Numerical results evidence that the proposed solution yields good error performance at the price of a limited complexity.

2011 - Compressed channel estimation and data detection algorithms for IR-UWB [Relazione in Atti di Convegno]
A., Barbieri; Pancaldi, Fabrizio; Vitetta, Giorgio Matteo
abstract

In this paper compressed sensing (CS) techniques are employed to develop reduced sampling rate strategies for channel estimation and data detection in impulse radio ultrawideband (IR-UWB) systems. In particular, first channel estimation algorithms based on Matching Pursuit (MP) and Basis Pursuit Denoising (BPDN) techniques are proposed. Then, it is shown how the channel estimates generated by these algorithms can be used in correlation-based CS detectors. Finally, the performance loss originating from CS is assessed analytically in a transmitted reference (TR) system.

2011 - Cross-Layer Design for Double-String Cooperative Communications in Wireless Ad-hoc Networks [Articolo su rivista]
Sergi, Simone; Pancaldi, Fabrizio; Vitetta, Giorgio Matteo
abstract

This paper proposes a novel architecture for cooperative communication in wireless ad-hoc networks capable of offering reliable and low-latency services efficiently. The proposed solution is characterised by the following relevant features: (i) a wireless connection between each couple of network nodes is established via multiple relays; (ii) each source-to-destination link is characterised by a double-string topology, allowing the use of specific transmit diversity techniques for reliable communications; and (iii) a novel utility-based routing metric providing a fair exploitation of the available energy/bandwidth resources is employed. Simulation results evidence that our solution offers substantial energy savings with respect to traditional ad-hoc architectures employing multihop routing and operating in the absence of cooperativestrategies.

2011 - On the Performance Limits of Pilot-Based Estimation of Bandlimited Frequency-Selective Communication Channels [Articolo su rivista]
Montorsi, Francesco; Vitetta, Giorgio Matteo
abstract

In this paper the problem of assessing bounds on the accuracy of pilot-based estimation of a bandlimited frequency selective communication channel is tackled. Mean square error is taken as a figure of merit in channel estimation and a tapped-delay line model is adopted to represent a continuous time channel via a finite number of unknown parameters. This allows to derive some properties of optimal waveforms for channel sounding and closed form Cramer-Rao bounds.

2011 - Statistical characterization and mitigation of NLOS errors in UWB localization systems [Relazione in Atti di Convegno]
Montorsi, Francesco; Pancaldi, Fabrizio; Vitetta, Giorgio Matteo
abstract

Abstract-In this paper some new experimental results about the statistical characterization of the non-line-oJ-sight (NLOS) bias affecting time-oj-arrival (TOA) estimation in ultrawideband (UWB) wireless localization systems are illustrated. Then, these results are exploited to assess the performance of variousmaximum-likelihood (ML) based algorithms for joint TOA localization and NLOS bias mitigation. Our numerical results evidence that the accuracy of all the considered algorithms is appreciably influenced by the LOSINLOS conditions of the propagation environment.

2010 - A Game Theoretical Approach to Distributed Relay Selection in Randomized Cooperation [Articolo su rivista]
Sergi, Simone; Vitetta, Giorgio Matteo
abstract

In this paper, the problem of node management in the presence of randomized cooperation is tackled. First, game theory is exploited to model the problem of setting up a cluster of cooperative nodes in a wireless network as a multiplayer noncooperative game. In this game the set of players is made of all the nodes belonging to a potential relay cluster an d the set of actions for each player consists of two options only (characterized by different payoffs), namely transmitting a data packet or remaining silent. Then, a novel strategy for the management of node participation to a distributed cooperative link is derived. The proposed solution is fully distributed, is characterized by autonomous choices made by each potential relay and is of significant practical interest since it guarantees the participation of a proper number of nodes to a virtual antenna array (so avoiding an energy waste associated with an excessive number of cooperating nodes) without requiring any overhead for node management.

2010 - A game theoretical approach to node partitioning in multi source-destination relay networks [Relazione in Atti di Convegno]
Sergi, Simone; Vitetta, Giorgio Matteo
abstract

In this paper the node management strategies based on game theory and proposed in [8] are generalised to solve the problem of node participation to a distributed cooperative link in a multi source-destination scenario. In addition, a node transmission strategy for the selection of the most profitable link is developed. The resulting strategies are fully distributed and do not rely on any explicit information exchange among network nodes.

2010 - A game theoretical approach to the management of node clusters in DR-OSTC based MISO cooperative communications [Relazione in Atti di Convegno]
Sergi, S.; Vitetta, G. M.
abstract

In this paper, the problem of node management in cooperative transmissions exploiting Distributed Randomized - Orthogonal Space Time Coding (DROSTC) schemes is tackled. In particular, resorting to game theory, a novel strategy able to manage node participation in a distributed cooperative link using a simple randomized coding rule is derived. The proposed solution guarantees the participation of a proper number of nodes to a virtual antenna array (hence avoiding an energy waste) without requiring any overhead for node management. Copyright © The authors.

2010 - A Game Theoretical Approach to the Management of Transmission Selection Scheme in Wireless Ad-Hoc Networks [Articolo su rivista]
Sergi, Simone; Pancaldi, Fabrizio; Vitetta, Giorgio Matteo
abstract

In this paper, game theory is exploited to derive a novel solution to manage virtual antenna array based transmissions in an ad hoc wireless network consisting of selfish nodes. In the proposed strategy each node decides, in an autonomous fashion, whether and when transmitting data packets over a shared wireless channel. The resulting transmission scheme results to be functionally equivalent to a distributed transmission selection scheme, managed, however, in a fully distributed fashion. This approach offers an higher throughput level and an higher efficiency than other communication protocols implementing selection diversity in distributed multi-antenna systems.

2010 - A Novel Approach to Power-Line Channel Modeling [Articolo su rivista]
F., Gianaroli; Barbieri, Alessandro; Pancaldi, Fabrizio; Mazzanti, Andrea; Vitetta, Giorgio Matteo
abstract

In this paper, a novel approach to statistical modelingof power-line channels is illustrated and its application tolow-voltage indoor power networks is analyzed in the bandwidth1–30 MHz. The proposed approach is based on the well-knownbifilar model and on a generalization of the so-called -branchnetwork topology. It is shown that our model can be exploitedto devise an efficient channel simulator predicting the meanimpedance matrix and transfer function between an arbitrarycouple of plugs in a class of indoor networks sharing multipleparameters (e.g., number of branches, minimum and maximumcable lengths, power-loading conditions). Finally, it is shown thatMonte Carlo results generated by our simulator are in good agreementwith a set of experimental data acquired in a measurementcampaign.

2010 - Channel estimation and data detection algorithms for UWB multiuser communications [Relazione in Atti di Convegno]
Barbieri, Alessandro; Pancaldi, Fabrizio; Vitetta, Giorgio Matteo
abstract

In this paper, a novel ultrawideband system for multiuser data communications is proposed. At the transmit side multiple users are allowed to send pulse position modulated signals in a synchronized fashion exploiting a given frequency subband in the same time intervals. Overlapped data frames sent by distinct users include low data rate training sequences with different repetition periods. This transmission strategy, known as rate division multiple access in the technical literature, allows to ease the first two fundamental tasks at the receive side, namely joint channel estimation and timing synchronization. Channel estimates are exploited by a multiuser detector based on the Viterbi algorithm and separating the contribution generated by the user of interest from those produced by all the other co-channel users. Numerical results evidence that the proposed solution can offer an efficient usage of the available spectrum at the price of a limited complexity.

2010 - Cluster-Based Ranging for Accurate Localization in Wireless Sensor Networks [Articolo su rivista]
Sergi, Simone; Pancaldi, Fabrizio; Vitetta, Giorgio Matteo
abstract

A novel ranging technique based on received signal strength (RSS) and suitable to indoor scenarios is illustrated. In the proposedtechnique, multiple power measurements, associated with the signals radiated by a cluster of nodes surrounding a given target,are jointly processed to improve the quality of RSS-based estimation of the distance between the target and an anchor. Specificalgorithms for the generation of a cluster and for the acquisition of power measurements are described. Simulation results showthat, when used in indoor positioning systems, the proposed ranging technique is substantiallymore accurate than noncooperativestrategies. In addition, it allows to concentrate significant processing tasks in a limited number of fixed anchors, so reducingmaintenance costs and making it possible to adopt cheap and simple portable wireless nodes.

2010 - Low-Rate-Feedback-Assisted Beamforming and Power Control for MIMO-OFDM Systems [Articolo su rivista]
ZUCCARDI MERLI, Filippo; Xiaodong, Wang; Vitetta, Giorgio Matteo
abstract

This paper proposes a novel solution to the problem of beamforming and power control in the downlink of a multiple-input multiple-output (MIMO) orthogonal frequency-division multiplexing (OFDM) system. This solution is developed in two steps. First, we describe an adaptive beamforming technique that, using a stochastic gradient method, maximizes the power delivered to a mobile terminal. In the proposed solution, perturbed precoding matrices are time multiplexed in the information signal transmitted to a mobile terminal; then, the mobile terminal informs the transmitter, via a single feedback bit, about the perturbation delivering the larger power. This approach does not need pilot symbols and uses quasi-Monte Carlo methods to generate the required perturbations with the relevant advantages of improving the downlink spectral efficiency and reducing the system complexity with respect to other competing solutions. Then, we propose a novel power-control algorithm that, selecting a proper transmission energy level from a set of possible values, aims to minimize the average bit error rate. This set of levels is generated on the basis of the channel statistics and a long-term constraint on the average transmission power. Numerical results evidence the robustness of the proposed algorithms in a dynamic fading environment.

2010 - Space-time block codes for noncoherent CPFSK [Articolo su rivista]
Pancaldi, Fabrizio; Barbieri, Alessandro; Vitetta, Giorgio Matteo
abstract

In this paper the problem of space-time block coding for multiple-input multiple-output communication systems employing continuous phase frequency shift keying and one-shot noncoherent detection is investigated. First, the detection problemis analysed in a maximum likelihood perspective; then, designcriteria for optimal space-time codes are proposed and someerror bounds are derived. Finally, some numerical results areillustrated for a couple of novel space-time block codes designedon the basis of the above mentioned criteria. Such results evidence that the use of the proposed schemes can entail a limited energy loss respect to other solutions available in the technical literature for coherent systems, with the relevant advantage, however, of a simple detection algorithm.

2009 - A Game Theory Approach to Selection Diversity in Wireless Ad-Hoc Networks [Relazione in Atti di Convegno]
Sergi, Simone; Pancaldi, Fabrizio; Vitetta, Giorgio Matteo
abstract

In this paper game theory is exploited to derive an optimal solution to the problem of cooperative data transmission based on distributed selection diversity in an ad hoc wireless network consisting of selfish nodes. First, a credit-based micro-economical model is proposed to manage node interaction; then, a transmission strategy maximizing node utility is derived. In the proposed strategy each node decides, in an autonomous fashion, whether and when transmitting data packets over a shared wireless channel. Numerical results evidence that this approach can ensure both fairness in the access to a shared medium and excellent network efficiency. In particular, it offers an higher throughput level than other communication protocols implementing selection diversity in distributed multi-antenna systems.

2009 - Cluster-Based Ranging for Accurate Localization in Wireless Sensor Neworks [Relazione in Atti di Convegno]
Sergi, Simone; Pancaldi, Fabrizio; Vitetta, Giorgio Matteo
abstract

In this paper a novel ranging technique based on received signal strength (RSS) and suitable to indoor scenarios is illustrated. The proposed technique improves the quality of RSS- based estimation of an anchor-target distance processing multiple power measurements associated with the signals radiated by a cluster of nodes surrounding the target. Specific algorithms for the generation of a cluster and for the acquisition of power measurements are described. Simulation results show that, when used in indoor positioning systems, the proposed ranging technique is substantially more accurate than non cooperative strategies. In addition it allows to concentrate significant processing tasks in a limited number of fixed anchors, so reducing maintenance costs and making possible to adopt cheap and simple portable wireless nodes.

2009 - Cooperative Communication Techniques for Wireless OFDMA-Based Ad-Hoc Networks [Relazione in Atti di Convegno]
Sergi, Simone; Pancaldi, Fabrizio; Vitetta, Giorgio Matteo
abstract

This paper proposes a new architecture for cooperative communication in wireless ad-hoc networks particularly suitable to emergency and safety applications. The proposed solution is characterized by the following relevant features: (a) a wireless connection between each couple of network nodes is established via multiple relays; (b) each source-to-destination link is characterized by a double string topology allowing the use of specific transmit diversity techniques for reliable communications; (c) a novel utility-based and distributed routing algorithm providing a fair exploitation of the available resources is employed. Simulation results evidence that our solution offers substantial energy savings with respect to traditional ad-hoc architectures.

2008 - A Bayesian Multiuser Detection Algorithm for MIMO-OFDM Systems Affected by Multipath Fading, Carrier Frequency Offset, and Phase Noise [Articolo su rivista]
F., ZUCCARDI MERLI; Xiaodong, Wang; Vitetta, Giorgio Matteo
abstract

We derive a novel Bayesian algorithm for multiuser detection in the uplink of a multiple-input multiple-output (MIMO) orthogonal frequency division multiplexing (OFDM) system employing stacked space-time block codes, such as the stacked Alamouti code with two transmit antennas, and a stacked quasi-orthogonal code with four transmit antennas. The proposed technique accomplishes joint estimation of the carrier frequency offset, phase noise, channel impulse response and data of each active user. Its derivation relies on the specific structure of the transmitted signal and on efficient Markov chain Monte Carlo (MCMC) methods. Simulation results evidence the robustness of the proposed algorithm in both uncoded and coded systems.

2008 - A Factor Graph Approach to the Iterative Detection of OFDM Signals in the Presence of Carrier Frequency Offset and Phase Noise [Articolo su rivista]
F. Z., Merli; Vitetta, Giorgio Matteo
abstract

This paper provides an approximate closed form solution to the problem of data-aided joint maximum likelihood estimation of the carrier frequency offset and of the channel impulse response in an Orthogonal Frequency Division Multiplexing transmission over a multipath fading channel. This results in a novel pilot-aided feedforward estimator, that can be employed for pilot-based receiver training. It is also shown how the novel joint estimation strategy can be exploited in an iterative (turbo) receiver structure to track the fast channel and frequency offset changes occurring during the transmission of information symbols. The performance of this structure is assessed by computer simulations and is compared with that provided by other estimation/detection strategies.

2008 - Iterative ML-based estimation of carrier frequency offset, channel impulse response and data in OFDM transmissions [Articolo su rivista]
F. Z., Merli; Vitetta, Giorgio Matteo
abstract

This paper provides an approximate closed formsolution to the problem of data-aided joint maximum likelihood estimation of the carrier frequency offset and of the channel impulse response in an Orthogonal Frequency Division Multiplexingtransmission over a multipath fading channel. Thisresults in a novel pilot-aided feedforward estimator, that can be employed for pilot-based receiver training. It is also shown how the novel joint estimation strategy can be exploited in an iterative (turbo) receiver structure to track the fast channel andfrequency offset changes occurring during the transmission of infomation symbols. The performance of this structure is assessed by computer simulations and is compared with that provided by other estimation/detection strategies.

2008 - Single-Carrier Frequency Domain Equalization [Articolo su rivista]
Pancaldi, Fabrizio; Vitetta, Giorgio Matteo; R., Kalbasi; N., Al Dhahir; M., Uysal; H., Mheidat
abstract

Orthogonal frequency division multiplexing (OFDM) has been recently adopted by major manufacturers and by standardization bodies for a wide range of wireless and wireline applications ranging from digital video/audio broadcasting to power-line communications. The major virtues of OFDM are 1) its resilience to multipath propagation providing a viable low-complexity and optimal (in the maximum likelihood sense) solution for intersymbol interference (ISI) mitigation, 2) the possibility of achieving channel capacity if the transmitted signal is adapted to the state of the communication channel (i.e., if energy and it-loading procedures are adopted), and 3) the availability of strategies for frequency diversity scheduling in multiuser communication systems. Although OFDM has become the physical layer of choice for broadband communications standards, it suffers from several drawbacks including a large peak-to-averagepower ratio (PAPR), intolerance to amplifier nonlinearities, and high sensitivity to carrier frequency offsets (CFOs) [6]. An alternative promising approach to ISI mitigation is the use ofsingle-carrier (SC) modulation combined with frequencydomainequalization (FDE). On the one hand, the complexityand performance of SC-FDE systems is comparable to that of OFDM while avoiding the above mentioned drawbacks associatedwith multicarrier (MC) implementation. On the other hand,FDE does not represent an optimal solution to signal detectionover ISI channels and SC systems cannot certainly offer thesame flexibility as OFDM in the management of bandwidth andenergy resources, both in single user and in multiuser communications.All these considerations have made the choicebetween SC-FDE and OFDM a strongly debated issue in academicand industrial circles. For this reason, we believe that SC-FDEtechniques deserve a deeper analysis in view of the significantattention given to MC techniques. The first MC scheme was proposed in 1966 [1], whereas the first approach to SC-FDE in digital communication systems dates back to 1973 [2]. Despite thesmall time separation between their introductions, many effortshave been devoted by the scientific community to the study ofMC solutions, but little attention has been paid to SC-FDE formany years. In the last decade, there has been a renewed interest in this area. The theoretical and practical gap between thetwo solutions is tightening, but the technical literature on MCcommunication is by far larger than that on SC-FDE. In thisarticle, we intend to provide an overview of the principles of SCFDE with a particular focus on wireless applications and to present an up-to-date review including the latest and most relevant research results in the SC-FDE area. Our article is tutorial in nature and, therefore, our emphasis is not on detailed mathematical derivations but rather on describing the salient features of SC-FDE techniques and comparing it to its MC counterpart.

2007 - A Bayesian Multiuser Detector for MIMO-OFDM Systems Affected by Multipath Fading, Carrier Frequency Offset and Phase Noise [Relazione in Atti di Convegno]
ZUCCARDI MERLI, Filippo; Vitetta, Giorgio Matteo; Xiaodong, Wang
abstract

2007 - A Factor Graph Approach to the Iterative Detection of OFDM Signals in the Presence of Carrier Frequency Offset and Phase Noise [Relazione in Atti di Convegno]
ZUCCARDI MERLI, Filippo; Vitetta, Giorgio Matteo
abstract

This paper provides a new iterative solution to the problem of the joint estimation of phase noise and residual carrier frequency offset in an orthogonal frequency division multiplexing transmission over a multipath fading channel, in the presence of known data and channel impulse response. The proposed technique results from the application of the sum- product algorithm to a factor graph representing the joint a posteriori probability density function of the carrier frequency offset and the phase noise vector affecting a given symbol. It is also shown that this estimation algorithm can be exploited in a coherent receiver for both data-aided training and decision-directed tracking. Its performance is assessed by computer simulations and is compared with that provided by other strategies.

2007 - Blind Feedforward Frequency Estimation for OFDM Signals Transmitted over Multipath Fading Channels [Articolo su rivista]
F., ZUCCARDI MERLI; Vitetta, Giorgio Matteo
abstract

This paper provides an approximate closed form solution to the problem of maximum likelihood (ML) estimation of the carrier frequency offset (CFO) in an orthogonal frequency division multiplexing (OFDM) signal transmitted over a multipath fading channel. This results in a novel feedforward frequency synchronizer, requiring only an approximate statistical knowledge of the communication channel. The performance of the proposed algorithm is assessed by computer simulations and is compared with that provided by other synchronizers and with Cramer-Rao bounds.

2007 - MIMO Precoding and Power Control based on 1-bit Feedback [Relazione in Atti di Convegno]
ZUCCARDI MERLI, Filippo; Vitetta, Giorgio Matteo; Xiaodong, Wang
abstract

This paper proposes a novel solution to the problem of beamforming and power control in the downlink of a multiple-input multiple-output (MIMO) orthogonal frequency division multiplexing (OFDM) system. This solution is developed in two steps. First, we describe an adaptive beamforming technique that, using a stochastic gradient method, maximizes the power delivered to a mobile terminal In the proposed solution, perturbed precoding matrices are time multiplexed in the information signal transmitted to a mobile terminal; then, the mobile terminal informs the transmitter, via a single feedback bit, about the perturbation delivering the larger power. This approach does not need pilot symbols and uses quasi-Monte Carlo methods to generate the required perturbations. Then, we propose a novel power control algorithm that, selecting a proper transmission energy level from a set of possible values, aims at minimizing the average bit error rate. This set of levels is generated on the basis of the channel statistics and of a long term constraint on the average transmission power. Numerical results evidence the robustness of the proposed algorithms in a dynamic fading environment.

2006 - An Iterative ML-Based Algorithm for the Joint Estimation of Carrier Frequency Offset, Channel Impulse Response and Data in OFDM Transmissions [Relazione in Atti di Convegno]
ZUCCARDI MERLI, Filippo; Vitetta, Giorgio Matteo
abstract

This paper provides an approximate closed form solution to the problem of data-aided joint maximum likelihood estimation of the carrier frequency offset and of the channel impulse response in an orthogonal frequency division multiplexing transmission over a multipath fading channel. This results in a novel data-aided feedforward estimator, that can be employed for pilot-based receiver training. It is also shown how the novel joint estimation strategy can be exploited in an iterative (turbo) receiver structure to track the fast channel and frequency offset changes occurring during the transmission of information symbols. The performance of this structure is assessed by computer simulations and is compared with that provided by other estimation/detection strategies.

2006 - Blind Feedforward Frequency Estimation for OFDM Signals Transmitted over Multipath Fading Channels [Relazione in Atti di Convegno]
ZUCCARDI MERLI, Filippo; Vitetta, Giorgio Matteo
abstract

In this paper a novel feedforward frequency synchronizer for orthogonal frequency division multiplexing (OFDM) signals transmitted over multipath fading channels is described. Its derivation is based on maximum likelihood (ML) estimation techniques and assumes an approximate statistical knowledge of the communication channel. The performance of the proposed algorithm is assessed by computer simulations and is compared with that provided by other synchronizers and with Cramer-Rao bounds.

2006 - Equalization algorithms in the frequency domain for continuous phase modulations [Articolo su rivista]
Pancaldi, Fabrizio; Vitetta, Giorgio Matteo
abstract

In this paper, novel equalization algorithms for continuous phase modulations (CPMs) are illustrated. Both conventional (linear and decision-feedback) and turbo equalization techniques are derived using the Laurent decomposition of CPM signals. All of them operate in the frequency domain and process two samples of the received signal per channel symbol. Numerical results show that on one hand, conventional equalization strategies offer good performance for binary partial response signaling over severely frequency-selective wireless channels at a moderate complexity. On the other hand, there is evidence that turbo techniques provide a small energy saving at the price of a substantial computational burden.

2006 - GQR-based models for directional wireless channels [Articolo su rivista]
Pancaldi, Fabrizio; P., Greco; Vitetta, Giorgio Matteo
abstract

In this paper novel reduced complexity statistical models for the representation of directional wireless channels affected by Rayleigh fading are developed. Their derivation is based on the evaluation of Fourier integrals by means of Gaussian quadrature rules (GQRs). The proposed models represent a communication channel as a tapped-angle and -delay line with non uniform spacing between successive taps. The application of the GQR approach to three different scenarios is also illustrated. Numerical results evidence that these models can provide a simple and accurate stochastic representation of directional fading channels.

2006 - Space-time block coding for noncoherently detected CPFSK [Relazione in Atti di Convegno]
Pancaldi, F.; Vitetta, G. M.
abstract

In this paper the problem of unitary rate space-time block coding for multiple-input multiple-output communication systems employing continuous phase frequency shift keying is investigated. First, the problem of optimal codeword by codeword noncoherent detection is analysed; then, design criteria for optimal space-time block codes are proposed and some novel coding schemes are devised. Simulation results evidence that the proposed schemes can efficiently exploit spatial diversity and that their use can entail a limited energy loss with respect to other solutions available in the technical literature for coherent systems, with the substantial advantage, however, of a simple detection algorithm.

2005 - Block channel equalization in the frequency domain [Articolo su rivista]
Pancaldi, Fabrizio; Vitetta, Giorgio Matteo
abstract

In this paper, channel equalization algorithms processing two samples of the received signal per channel symbol and operating in the frequency domain are described in a unifying framework. First, minimum mean-square error linear and decision-feedback equalizers are derived, and a synthesis technique based on the well-known Levinson-Durbin algorithm is proposed for the latter. Then, iterative linear and decision-feedback equalization algorithms for turbo processing are devised. Performance results for both uncoded and coded phase-shift keying transmissions show the efficacy of the proposed equalization techniques and their superiority over other existing frequency-domain equalization strategies.

2005 - Equalization Algorithms in the Frequency Domain for Continuous Phase Modulations [Relazione in Atti di Convegno]
Pancaldi, Fabrizio; Vitetta, Giorgio Matteo
abstract

In this paper novel linear and decision feedback equalization algorithms for continuous phase modulations (CPMs) are illustrated. These algorithms operate in the frequency domain and process two samples of the received signal per channel symbol. Their derivation is based on the Laurent decomposition of CPM signals. Numerical results evidence that the proposed techniques enable the use of CPMs over severely frequency selective wireless channels.

2005 - Frequency-domain equalization for space-time block-coded systems [Articolo su rivista]
Pancaldi, Fabrizio; Vitetta, Giorgio Matteo
abstract

In this paper, conventional and turbo-channel-equalization algorithms processing two samples of the received signal per channel symbol and operating in the frequency domain are proposed for space-time block-coded systems. In the class of conventional equalization techniques, minimum-mean-square-error (MAISE) linear and decision-feedback equalizers (DFE) are derived and a synthesis technique based on the well-known Levinson-Durbin algorithm is proposed for the latter. Similarly, iterative linear and decision-feedback-equalization algorithms for turbo receivers are devised. Performance results show the efficacy of the proposed equalization techniques and their superiority over other frequency-domain-equalization strategies.

2005 - Soft-in soft-output detection in the presence of parametric uncertainty via the bayesian em algorithm [Articolo su rivista]
Gallo, A. S.; Vitetta, G. M.
abstract

We investigate the application of the Bayesian expectation-maximization (BEM) technique to the design of soft-in soft-out (SISO) detection algorithms for wireless communication systems operating over channels affected by parametric uncertainty. First, the BEM algorithm is described in detail and its relationship with the well-known expectation-maximization (EM) technique is explained. Then, some of its applications are illustrated. In particular, the problems of SISO detection of spread spectrum, single-carrier and multicarrier space-time block coded signals are analyzed. Numerical results show that BEM-based detectors perform closely to the maximum likelihood (ML) receivers endowed with perfect channel state information as long as channel variations are not too fast. © 2005 Hindawi Publishing Corporation.

2005 - Space-Time Block Codes for Noncoherent CPFSK [Relazione in Atti di Convegno]
Pancaldi, Fabrizio; Vitetta, Giorgio Matteo
abstract

In this paper the problem of unitary rate space-time block coding for multiple-input multiple-output communication systems employing continuous phase frequency shift keying is investigated. First, one-shot noncoherent detection is analysed in a maximum likelihood perspective; then, design criteria for optimal space-time codes are proposed and some error bounds for the devised coding schemes are derived. Numerical results evidence that the use of the proposed coding schemes can entail a limited energy loss with respect to other solutions available in the technical literature for coherent systems, with the relevant advantage, however, of a simple detection algorithm

2004 - A BEM-based algorithm for soft-in soft-output detection of co-channel signals [Articolo su rivista]
A. S., Gallo; E., Chiavaccini; F., Muratori; Vitetta, Giorgio Matteo
abstract

In this paper, a soft-in soft-out multiuser detector for synchronous co-channel signals transmitted over frequency-flat Rayleigh-fading channels is described. The derivation of the proposed algorithm is based on a generalization of the expectation-maximization (EM) algorithm, called Bayesian EM. Performance results for both uncoded and coded phase shift keying transmissions show the efficacy of the proposed multiuser detection technique over slowly time-varying fading channels in a two-user system.

2004 - A novel soft-in soft-out detection algorithm for space-time coded OFDM over multipath fading channels [Relazione in Atti di Convegno]
Gallo, Antonio Stanislao; Vitetta, Giorgio Matteo
abstract

A novel soft-in soft-out detector for space-time block coded OFDM systems operating over multipath fading channels is derived using the Bayesian expectation-maximization (BEM) technique. It exploits statistical information about the communication channel and can he easily incorporated in iterative receivers when outer coding is adopted at the transmitter. Numerical results evidence the efficacy of the proposed algorithm, even in the presence of significant channel variations.

2004 - Adaptive space-time-frequency coding schemes for MIMO OFDM [Relazione in Atti di Convegno]
Bizzarri, Emanuele; Gallo, Antonio Stanislao; Vitetta, Giorgio Matteo
abstract

In this paper, some novel results on adaptive space-time-frequency (STF) coding schemes for multiple-input multiple-output (MIMO) OFDM systems are illustrated. Such schemes result from the concatenation of conventional channel codes with orthogonal space-time block codes (STBCs). In the proposed channel codes, adaptivity can be implemented by adjusting the constellation/energy of the inner STBC code on a subcarrier by subcarrier basis via a space-frequency water-filling procedure and/or modifying some parameters, like the code rate and codeword size, of the outer code. Numerical results show that, in a MIMO OFDM systems with one or two receive antennas, using Alamouti's STBC, and without outer coding, STBC adaptivity can yield an appreciable energy gain over an unloaded system operating at the some data rate. The use of an additional outer code can provide a further substantial gain, at least for high signal-to-noise ratios.

2004 - BEM-based SISO detection of orthogonal space-time block codes over frequency flat-fading channels [Articolo su rivista]
A. S., Gallo; E., Chiavaccini; F., Muratori; Vitetta, Giorgio Matteo
abstract

The expectation-maximization algorithm for maximum a posteriori (MAP) estimation of a random vector is applied to the problem of detection of orthogonal space-time block codes over time-selective Rayleigh fading channels. This results in a soft-in soft-out detection algorithm suitable for iterative detection/decoding schemes. Simulation results show that the error performance of the proposed detection algorithm is very close to that of a MAP detector endowed with an ideal knowledge of the channel state if the fading rate is not too fast.

2004 - Block equalization techniques in the frequency domain [Relazione in Atti di Convegno]
Pancaldi, Fabrizio; Vitetta, Giorgio Matteo
abstract

In this work various channel equalization algorithms operating in the frequency domain are described in a unifying framework. First, minimum mean square error linear and decision-feedback equalizers are derived and a synthesis technique based on the well-known Levinson-Durbin algorithm is proposed for the latter. Then, iterative linear and decision feedback equalization algorithms for turbo processing are devised. Performance results for both uncoded and coded PSK transmissions show the efficacy of the proposed equalization techniques and their superiority over other existing frequency domain equalization strategies.

2004 - GQR models for directional wireless channels [Relazione in Atti di Convegno]
L., Fregni; F., Muratori; P., Greco; Vitetta, Giorgio Matteo; Pancaldi, Fabrizio
abstract

In this paper novel reduced complexity statisticalmodels for the representation of wide sense stationary–uncorrelated scattering directional wireless channels affected byRayleigh fading are developed. Their derivation is based on theso-called Gaussian quadrature rule approach illustrated in [1] fornon directional channels. Numerical results evidence that theproposed models can provide a simple and accurate stochasticrepresentation of directional fading channels.

2004 - Maximum-likelihood frequency recovery for OFDM signals transmitted over multipath fading channels [Articolo su rivista]
Chiavaccini, E.; Vitetta, Giorgio Matteo
abstract

In this paper, a novel feedback frequency synchronizer for orthogonal frequency-division multiplexing signals transmitted over multipath fading channels is described. Its derivation is based on maximum-likelihood estimation techniques and assumes an approximate statistical knowledge of the communication channel. The performance of the proposed algorithm is assessed by computer simulation, and is compared with that provided by other synchronization algorithms and with Cramer-Rao bounds.

2003 - A comparison of inner coding options for adaptive MIMO OFDM systems [Relazione in Atti di Convegno]
Gallo, Antonio Stanislao; Bizzarri, Emanuele; Vitetta, Giorgio Matteo; Marciniak, M.
abstract

Some novel results concerning adaptive space-time-frequency coding schemes for MIMO OFDM systems are illustrated. In the proposed concatenated schemes, a conventional convolutional encoder is followed by a bit-wise interleaver and an inner orthogonal space-time encoder in order to exploit the space/frequency diversity provided by the frequency selective MIMO channel. Adaptivity can be implemented by adjusting the constellation size on a subcarrier by subcarrier basis by means of standard bit/energy-loading algorithms for SISO channels. An extension of the transmit selection diversity (TSD) technique for the two transmit/receive antenna scenario is also considered as an alternative to the inner ST code.

2003 - A novel BEM-based multiuser detector for co-channel signals transmitted over frequency-flat fading channels [Relazione in Atti di Convegno]
Gallo, Antonio Stanislao; Chiavaccini, Eugenio; Vitetta, Giorgio Matteo
abstract

In this paper a novel soft-in soft-out (SISO) multiuser detector for co-channel signals transmitted over frequency-flat Rayleigh fading channels is described. The derivation of the proposed algorithm is based on a generalization of the expectation-maximization (EM) algorithm, called Bayesian EM (BEM). Performance results for both uncoded and coded PSK transmissions show the efficacy of the proposed multiuser detection technique over slowly time-varying fading channels in a two user system.

2003 - BEM-based detector for CPM signals transmitted over frequency-flat fading channels [Articolo su rivista]
Chiavaccini, Eugenio; Vitetta, Giorgio Matteo
abstract

In this paper, the expectation-maximization (EM) algorithm for maximum a posteriori (MAP) estimation of a random vector is applied to the problem of symbol detection, for continuous phase modulation signals transmitted over time-selective Rayleigh-fading channels. This results in a soft-in-soft-out detection algorithm suitable for iterative detection/decoding schemes. Simulation results show that the error performance provided by the proposed solution is very close to that of a MAP detector endowed with an ideal knowledge of the channel state both in uncoded and coded transmissions.

2003 - Further results on differential space-time modulations [Articolo su rivista]
Chiavaccini, Eugenio; Vitetta, Giorgio Matteo
abstract

In this paper, some novel results on the space-time differential modulation schemes described by Hochwald and Sweldens, and Tarokh and Jafarkhani, are derived under the assumption of a quasi-static multiple-antenna channel. First, the optimality (in the maximum-likelihood sense) of the one-shot detection algorithms of Hochwald and Sweldens, and Throkh and Jafarkhani, is proved. Then the expression of the pairwise error probability for these detectors is derived, and, as a particular case, the bit-error rate is computed for the binary phase-shift keyed scheme of Throkh and Jafarkhani. Finally, a per-survivor processing (PSP) detection algorithm for this class of modulations is illustrated. Numerical results evidence both the superiority of the PSP strategy over the one-shot space-time differential detectors and the accuracy of the above-mentioned bit-error rate formula.

2003 - GQR models for directional wireless channels [Relazione in Atti di Convegno]
Fregni, Lodovico; Muratori, Fabrizio; Greco, Paola; Vitetta, Giorgio Matteo; Pancaldi, Fabrizio
abstract

In this paper, a novel reduced complexity statistical models for the representation of wide sense stationary-uncorrelated scattering directional wireless channels affected by Rayleigh fading are developed. Their derivation is based on the so-called Gaussian quadrature rule approach illustrated by E. Chiavaccini and G. M. Vitetta (June 2001) for non directional channels. Numerical results evidence, that the proposed models provide a simple and accurate stochastic representation of directional fading channels.

2002 - BEM-based multiuser detection for synchronous DS-CDMA systems over frequency flat fading channels [Relazione in Atti di Convegno]
Gallo, Antonio Stanislao; Chiavaccini, Eugenio; Vitetta, Giorgio Matteo
abstract

A soft-input soft-output (SISO) multiuser detection algorithm for synchronous direct sequence-code division multiple access (DS-CDMA) systems operating over a slow Rayleigh fading channel is illustrated. Its derivation is based on the Bayesian expectation maximization (BEM) technique. The proposed detector estimates the fading channel in an iterative fashion and produces the a posteriori probabilities (APPs) of the transmitted symbols. Its error performance is assessed by computer simulation and is compared with that provided by other multiuser detectors.

2002 - BEM-based SISO detection of space-time block coded signals transmitted over frequency-flat fading channels [Relazione in Atti di Convegno]
Chiavaccini, Eugenio; Gallo, Antonio Stanislao; Muratori, Fabrizio; Vitetta, Giorgio Matteo
abstract

In this paper the expectation-maximization (EM) algorithm for maximum a posteriori (MAP) estimation of a random vector is applied to the problem of detection of space-time block coded (STBC) signals over time-selective Rayleigh fading channels. This results in a soft-in soft-out (SISO) detection algorithm suitable for iterative detection/decoding schemes. Simulation results show that the error performance of the proposed detection algorithm is very close to that of a MAP detector endowed with an ideal knowledge of the channel state if the fading rate is not too fast.

2002 - Equalization Techniques for mitigating transmission impairments [Capitolo/Saggio]
M. Z., Win; J. H., Winters; Vitetta, Giorgio Matteo
abstract

Most current multi-gigabit per second digital fiber optic systems use simple modulation and detection techniques such as on-off keying with matched-filter receiver techniques. However, more complex techniques such as equalization, error control coding, and/or multilevel signaling, can be used in lightwave systems to significantly increase the data rate and/or reduce the effect of transmission impairments and improve performance, and, in many cases can be easily implemented. There are numerous sources of transmission impairments in lightwave systems. These include chromatic dispersion and polarization mode dispersion (PMD) in the fiber, laser and fiber nonlinearities, nonideal receiver response, echo, and distortion caused by semiconductor optical amplifiers. Fortunately, there are also numerous techniques to reduce these impairments, including error control coding, equalization, and modulation techniques with multilevel signaling. These techniques can be used for upgrading existing systems (e.g., reducing chromatic dispersion and PMD in systems with previously installed fiber) or as an alternative to the use of more costly transmitters and receivers (e.g., using coding to permit less stringent laser specifications). The purpose of this chapter is to provide an overview of equalization techniques, which become increasingly important as device technology matures, in which case substantial increases in performance (especially for already installed systems) may only be achieved through these techniques. We will examine the prospects for the application of digital equalization techniques to overcome the above impairments, where the improvement is large and the implementation is relatively simple.

2002 - Further results on Tarokh's space-time differential technique [Relazione in Atti di Convegno]
Chiavaccini, Eugenio; Vitetta, Giorgio Matteo
abstract

Novel results on the space-time differential detection technique described by V. Tarokh and H. Jafarkhani (see IEEE J. Select. Areas Commun., vol.18, no.7, p.1169-74, 2000) are derived. First, the optimality of the one-shot detection algorithm proposed by Tarokh and Jafarkhani is proved under some assumptions about the channel model and an accurate bit error rate formula for this detector is derived in a particular case. Finally, a per-survivor processing (PSP) receiver, substantially outperforming Tarokh's detector, is derived. Numerical results show both the superiority of the PSP receiver over the one-shot detector and the accuracy of the above mentioned error rate formula.

2001 - A per-survivor phase-estimation algorithm for detection of PSK signals [Articolo su rivista]
Chiavaccini, Eugenio; Vitetta, Giorgio Matteo
abstract

In this letter, an expectation-maximization (EM) technique for maximum a posteriori (MAP) estimation of a random parameter is employed to devise a per-survivor phase-tracking algorithm for phase-shift-keyed signals transmitted over channels with phase jitter. Simulation results show that the proposed algorithm can provide substantial performance gains over recursive and non-recursive phase estimators in the presence of a strong phase jitter.

2001 - An EM-based MAP detector for CPM signals transmitted over frequency-flat fading channels [Relazione in Atti di Convegno]
Chiavaccini, Eugenio; Vitetta, Giorgio Matteo
abstract

In this paper the expectation-maximization (EM) algorithm for maximum a posteriori (MAP) estimation of a random vector is applied to the problem of symbol detection for CPM signals transmitted over time-selective Rayleigh fading channels. This results in a soft-in soft-out (SISO) detection algorithm suitable for iterative detection/decoding schemes. Simulation results show that the error performance provided by the proposed solution is very close to that of a MAP detector endowed with an ideal knowledge of the channel state.

2001 - Equalization Techniques for Single Carrier, Unspread Digital Modulations [Capitolo/Saggio]
Vitetta, Giorgio Matteo; B., Hart; A., Mammela; D. P., Taylor
abstract

Like the other Parts of this book we are concerned with the design, interpretation, implementation and performance assessment of communication systems for wireless channels. Unlike Part II, we consider the case where the channel's delay spread and/or time variation are sufficiently large that equalization can significantly improve performance. Unlike Parts IV and V, we restrict our attention to classical single carrier, unspread digital modulation schemes even though many principles can be directly applied in other schemes. In addition we mainly focus on linear digital modulations transmitted over linear time-varying channels.

2001 - Error performance of matched and partially matched one-shot detectors for doubly selective Rayleigh fading channels [Articolo su rivista]
Chiavaccini, Eugenio; Vitetta, Giorgio Matteo
abstract

In this paper, optimum one-shot detection over known and partially known doubly selective Rayleigh fading channels is investigated. Reduced complexity channel models based on Gauss quadrature rules and Taylor power series are derived and are employed to develop novel analytical tools for the performance analysis of one-shot detectors. Numerical results allow to assess the implicit diversity gain provided by both channel multipath and signal fading and the energy loss due to the mismatch of the receiver filter.

2001 - Feedforward Joint Phase and Timing Estimation for MSK-Type Signals [Articolo su rivista]
M., Morelli; Vitetta, Giorgio Matteo
abstract

Novel non data - aided (NDA) algorithms are proposed for joint estimation of timing and carrier phase in MSK - type modulations. They are based on maximum likelihood methods and have a feedforward structure which is suitable to fully digital implementation. Performance with MSK and Gaussian MSK. (GMSK) is assessed by computer simulations and compared with that of other existing estimation schemes.

2001 - GQR models for multipath Rayleigh fading channels [Articolo su rivista]
Chiavaccini, Eugenio; Vitetta, Giorgio Matteo
abstract

In this paper, reduced complexity statistical models for the representation of wide sense stationary-uncorrelated scattering doubly selective fading channels are developed. Their derivation is based on the evaluation of Fourier integrals by means of Gaussian quadrature rules. The accuracy and the complexity of the proposed models is assessed, and is then compared to that provided by other modeling techniques available in the literature.

2001 - MAP symbol estimation on frequency-flat Rayleigh fading channels via a Bayesian EM algorithm [Articolo su rivista]
Chiavaccini, Eugenio; Vitetta, Giorgio Matteo
abstract

In this paper, an expectation-maximization technique for maximum a posteriori estimation is employed to devise novel soft-in soft-out algorithms for symbol detection over frequency-flat Rayleigh fading channels. An application of these algorithms to iterative decoding of coded PSK signals is proposed and some performance results are illustrated.

2001 - MAP symbol estimation on frequency-flat Rayleigh fading channels via a Bayesian EM algorithm [Relazione in Atti di Convegno]
Chiavaccini, Eugenio; Vitetta, Giorgio Matteo
abstract

In this paper an expectation-maximization (EM) technique for maximum a posteriori (MAP) estimation is employed to devise novel soft-in soft-out (SISO) algorithms for symbol detection over frequency-flat Rayleigh fading channels. An application of these algorithms to iterative decoding of coded PSK signals is proposed and some performance results are illustrated.

2001 - Maximum likelihood frequency recovery for OFDM signals transmitted over multipath fading channels [Relazione in Atti di Convegno]
Chiavaccini, Eugenio; Vitetta, Giorgio Matteo
abstract

In this paper a novel feedback frequency synchronizer for OFDM signals transmitted over multipath fading channels is described. Its derivation is based on maximum likelihood (ML) estimation techniques and assumes an approximate statistical knowledge of the communication channel. The performance of the proposed algorithm is assessed by computer simulation and is compared with that provided by other synchronization algorithms and with Cramer-Rao bounds.

2001 - Performance Analysis of Matched and Partially Matched One-Shot Detectors for Doubly-Selective Rayleigh Fading Channels [Articolo su rivista]
Chiavaccini, Eugenio; Vitetta, Giorgio Matteo
abstract

In this paper optimum one-shot detection over known and partially known doubly-selective Rayleigh fading channels is investigated. Reduced complexity channel models based on Gauss Quadrature Rules (GQRs) and Taylor power series are derived and are employed to develop novel analytical tools for the performance analysis of one-shot detectors. Numerical results allow to assess the implicit diversity gain provided by both channel multipath and signal fading and the energy loss due to the mismatch of the receiver filter.

2000 - A noncoherent receiver for interleaved trellis-coded CPFSK signals transmitted over frequency-flat fading channels [Articolo su rivista]
Vitetta, Giorgio Matteo; U., Mengali
abstract

We propose a novel two-stage noncoherent receiver for interleaved trellis-coded CPFSK signals transmitted over time-selective channels, The first stage of the receiver computes reliability information about the transmitted symbols and delivers it to the second stage which operates as a trellis decoder. Simulation results show that the proposed detection strategy outperforms previous noncoherent receivers,vith a moderate increase in complexity.

2000 - Error performance of OFDM signaling over doubly-selective Rayleigh fading channels [Articolo su rivista]
Chiavaccini, Eugenio; Vitetta, Giorgio Matteo
abstract

In this letter a simple method for the evaluation of the error rate performance of OFDM signals transmitted over doubly-selective fading channels is described. The accuracy of the proposed technique is exemplified by simulation results.

2000 - GQR-based reduced models for multipath Rayleigh fading channels [Relazione in Atti di Convegno]
Chiavaccini, Eugenio; Vitetta, Giorgio Matteo
abstract

In this paper reduced complexity statistical models for the representation of wide sense stationary-uncorrelated scattering (WSS-US) doubly-selective fading channels are developed. Their derivation is based on the evaluation of Fourier integrals by means of Gaussian quadrature rules (GQRs). The accuracy and the complexity of the proposed models are assessed and are compared with that provided by other modelling techniques available in the literature.

2000 - Joint phase and timing recovery for MSK-type signals [Articolo su rivista]
M., Morelli; Vitetta, Giorgio Matteo
abstract

Novel nondata-aided algorithms are proposed for joint estimation of timing and carrier phase in minimum-shift keying (MSK)-type modulations. Performance with MSK and Gaussian MSK is assessed by computer simulations and compared with that of other existing estimation schemes.

2000 - Performance analysis of matched and partially matched one-shot detectors over doubly-selective Rayleigh fading channels [Relazione in Atti di Convegno]
Chiavaccini, Eugenio; Vitetta, Giorgio Matteo
abstract

In this paper optimum one-shot detection over known and partially known doubly-selective Rayleigh fading channels is investigated. The performance analysis of the detection algorithms is based on GQR (Gauss quadrature rules) and power series channel models. The proposed methods allow to assess the implicit diversity gain provided by both channel multipath and signal fading and the energy loss due to the mismatch of the receiver filter.

2000 - Performance analysis of OFDM signalling over doubly-selective fading channels [Relazione in Atti di Convegno]
Chiavaccini, Eugenio; Vitetta, Giorgio Matteo
abstract

A simple method for the evaluation of the error rate performance of OFDM signals transmitted over doubly-selective fading channels is described. The accuracy of the proposed technique is exemplified by simulation results. Power series models for multipath channels are employed to derive simple expressions for the average signal-to-interference ratio (SIR) and the average error probability.

1999 - An error probability formula for noncoherent orthogonal binary FSK with dual diversity on correlated Rician channels [Articolo su rivista]
Vitetta, Giorgio Matteo; U., Mengali; D. P., Taylor
abstract

We derive a novel error probability formula for noncoherent detection of orthogonal binary frequency-shift keying with dual diversity and equal gain combining in the presence of slow, correlated, Rician time-selective fading. Numerical results indicate that: 1) fading correlation may produce a substantial performance loss and 2) the error performance of the noncoherent detector improves uniformly as the intensity of the line-of-sight signal component increases.

1999 - Block channel equalization in the presence of a cochannel interferent signal [Articolo su rivista]
A., Ginesi; Vitetta, Giorgio Matteo; D. D., Falconer
abstract

Novel algorithms for block equalization of M-ary phase shift keying (PSK) signals transmitted over multipath fading channels in the presence of an interferent cochannel signal are introduced and analyzed. The algorithms exploit the intrinsic statistical properties of cochannel interference (CCI) in order to mitigate its effects. Both linear and decision feedback equalizers (DFE's) are derived under the assumption that the overall channel impulse responses of both the useful and the inteferent signal are known, Simulation results show that: a) whereas zero-forcing block equalizers yield a large noise enhancement effect, a minimum mean-square block DFE (MMSE-BDFE) can efficiently compensate for the distortion in the useful channel and reduce the effect of CCI at the same time and b) MMSE-BDFE's outperform conventional DFE's, at least in the idealized conditions of our analysis.

1999 - Differential detection algorithms for MSK signals over AWGN and frequency-flat Rayleigh fading channels [Articolo su rivista]
Vitetta, Giorgio Matteo; U., Mengali; M., Morelli
abstract

Novel symbol-by-symbol differential detection algorithms are proposed for minimum-shift keying signals transmitted over additive white Gaussian noise and frequency-hat Rayleigh fading channels, They are derived as approximations to the maximum likelihood noncoherent detection strategy, Their error performance is assessed by computer simulation and is compared with that of other noncoherent detectors. It is shown that, with fading channels, the new algorithms outperform the traditional methods.

1999 - Differential detection algorithms for MSK signals over AWGN and frequency-flat rayleigh fading channels [Articolo su rivista]
Vitetta, G. M.; Mengali, U.; Morelli, M.
abstract

Novel symbol-by-symbol differential detection algorithms are proposed for MSK signals transmitted over additive white Gaussian noise and frequency-flat Rayleigh fading channels. They are derived as approximations to the maximum-likelihood noncoherent detection strategy. Their error performance is assessed by computer simulation and is compared with that of other noncoherent detectors. It is shown that, with fading channels, the new algorithms outperform the traditional methods. © 1999 IEEE.

1999 - Double-filter differential detection of PSK signals transmitted over linearly time-selective Rayleigh fading channels [Articolo su rivista]
Vitetta, Giorgio Matteo; U., Mengali; D. P., Taylor
abstract

Linearly time-varying fading models are used to investigate differential detection of PSK signals transmitted over frequency-flat fading channels. The structure of the optimal differential PSK detector is derived and an analytical technique is developed to compute its error performance, Results obtained by computer simulation are in excellent agreement with the analytical predictions.

1999 - Error Probability of FSK Incoherent Diversity Reception with Fast Rice Fading [Articolo su rivista]
Vitetta, Giorgio Matteo; U., Mengali; D. P., Taylor
abstract

In this paper we compute the error performanceof noncoherent detection receivers for FSK signalstransmitted over fast frequency-flat Rician fadingchannels. Linearly time-varying fading models are used to derive closed-form expressions for the errorprobability of binary FSK signaling. Error bounds areestablished for the performance of M-ary orthogonal FSK.Simulation results are in excellent agreement with analytical predictions.

1999 - Joint phase and timing synchronization algorithms for MSK-type signals [Relazione in Atti di Convegno]
M., Morelli; Vitetta, Giorgio Matteo
abstract

Novel non data-aided (NDA) algorithms are proposed for joint estimation of timing and carrier phase in MSK-type modulations. They are based on maximum likelihood methods and have a feedforward structure which is suitable for fully digital implementation. Performance with MSK and Gaussian MSK (GMSK) is assessed by computer simulations and compared with that of other existing estimation schemes

1999 - Noncoherent double-filter detection of FSK and DPSK signals with diversity [Relazione in Atti di Convegno]
D. P., Taylor; Vitetta, Giorgio Matteo
abstract

Linearly time-varying fading models are used to investigate both noncoherent detection of FSK signals and differential detection of PSK signals over frequency-flat fading channels. The structure of the optimal FSK and DPSK detectors is derived and an analytical technique is proposed to compute their error performance in fast fading

1998 - Blind channel equalization and data detection for OFDM transmissions on frequency-selective channels [Relazione in Atti di Convegno]
M., Luise; R., Reggiannini; Vitetta, Giorgio Matteo
abstract

A novel detection algorithm for orthogonal frequency division multiplexing (OFDM) signals transmitted over frequency-selective channels is introduced and analyzed. Simulation results show that the proposed detection strategy, implemented via a standard Viterbi algorithm, provides improved performance over differential detection with a moderate increase in receiver complexity, and without requiring the periodic transmission of a training block

1998 - Blind detection of CPM signals transmitted over frequency-flat fading channels [Articolo su rivista]
Vitetta, Giorgio Matteo; U., Mengali; D. P., Taylor
abstract

We propose a novel detection scheme for continuous-phase modulation (CPM) signals transmitted over frequency-flat fading channels. Its most significant feature is that it operates without statistical information on the fading channel, and for this reason it is nicknamed “blind detector.” Its error-rate performance is assessed with minimum shift keying (MSK) and Gaussian MSK (GMSK) schemes and compared with the performance of other decoders

1998 - Blind equalization/detection for OFDM signals over frequency-selective channels [Articolo su rivista]
M., Luise; R., Reggiannini; Vitetta, Giorgio Matteo
abstract

A novel equalization/detection algorithm for orthogonal frequency division multiplexing (OFDM) signals transmitted over frequency-selective channels is introduced and investigated. The algorithm stems from the recognition that the Fourier transform processing inherent in OFDM turns a single wideband frequency-selective channel into a set of correlated narrowband frequency-flat fading channels. This suggests that sequence detection techniques, such as those discussed by Vitetta et al. (see IEEE Trans. Commun., vol.43, p.2750-8, 1995, IEEE Trans. Commun., vol.43, pt.II, p.1256-9, 1995, and Proc. IEEE Commun. Theory Mini-Conf (Globecom '96), London, UK, p.153-7, 1996), for time-selective flat-fading channels, can be also profitably utilized for joint equalization and decoding of OFDM signals in the frequency domain. Simulation results show that the proposed detection strategy, implemented via a standard Viterbi algorithm, provides improved performance over differential detection, with a moderate increase in receiver complexity and without requiring the periodic transmission of training blocks.

1998 - Differential detection of PSK signals transmitted over linearly time-selective Rayleigh fading channels [Relazione in Atti di Convegno]
Vitetta, Giorgio Matteo; U., Mengali; D. P., Taylor
abstract

Linearly time-varying fading models are used to investigate the differential detection of PSK signals transmitted over frequency-flat fading channels. The structure of an optimal differential PSK detector is derived and an analytical technique is proposed to compute its error performance. The results obtained by computer simulation are in excellent agreement with the analytical predictions.

1998 - Error probability with incoherent diversity reception of FSK signals transmitted over fast Rician fading channels [Articolo su rivista]
Vitetta, Giorgio Matteo; U., Mengali; D. P., Taylor
abstract

In this paper we compute the error performance of noncoherent detection receivers for FSK signals transmitted over fast frequency-flat Rician fading channels. Linearly time-varying fading models are used to derive closed-form expressions for the error probability of binary FSK signaling. Error bounds are established for the performance of M-ary orthogonal FSK. Simulation results are in excellent agreement with analytical predictions.

1998 - EXCESS BANDWIDTH IS NECESSARY FOR ISI-FREE DOUBLE-FILTER RECEIVERS [Articolo su rivista]
U., Mengali; Vitetta, Giorgio Matteo; D. P., Taylor
abstract

Previous work has indicated that highly effective double-filter receivers can be implemented for phase-shift keying (PSK) transmissions over linearly time-selective fading channels provided that the transmitter and receiver filters have root-raised-cosine transfer functions with unity rolloff factor. Revisiting the detection problem within the frame of maximum-likelihood (ML) sequence estimation we prove that this filter design is unique within the class of signaling pulses which are band limited to the symbol rate. It is concluded that some waste of bandwidth is inevitable for achieving ISI-free operation with double-filter receivers

1998 - Further results in carrier frequency estimation for transmissions over flat fading channels [Articolo su rivista]
M., Morelli; U., Mengali; Vitetta, Giorgio Matteo
abstract

data-aided feedforward algorithm has been proposed by Kuo and Fitz (see IEEE Trans. Commun., vol.45, p.1412-26, 1997) for carrier frequency estimation in M-ary phase-shift keying (PSK) transmissions over frequency-flat Rayleigh fading channels. Its accuracy is very good but the estimation range may be limited under certain operating conditions. Also, its application requires a knowledge of the Doppler bandwidth. We show that the estimation range can be greatly extended without sacrificing the estimation accuracy and a simple technique is indicated to measure the Doppler bandwidth. This allows the algorithm to operate in an adaptive manner in a time-varying environment.

1998 - Noncoherent detector for interleaved trellis-coded CPFSK signals transmitted over frequency-flat fading channels [Relazione in Atti di Convegno]
Vitetta, G. M.; Mengali, U.
abstract

We propose a novel two-stage noncoherent receiver for interleaved trellis-coded CPFSK signals transmitted over time-selective channels. The first stage of the receiver computes reliability information about the transmitted symbols and delivers it to the second stage which operates as a trellis decoder. Simulation results show that the proposed detection strategy outperforms previous noncoherent receivers with a moderate increase in complexity.

1998 - Wireless Channel Equalisation [Articolo su rivista]
Taylor, D. P.; Vitetta, Giorgio Matteo; Hart, B. D.; Mammela, A.
abstract

Equalisation techniques for wireless channels, in particular for those encountered in mobile wireless communications, are examined. Equalisation is broadly defined to include reception techniques which estimate the state or response of the channel and then attempt to compensate for its effects. The paper considers equalisation techniques for fading dispersive channels which include both time and frequency selectivity. In addition, brief consideration is given to the problems of blind equalisation, techniques for dealing with fast fading channels and to the problem of joint equalisation and decoding. The paper does not attempt to provide in-depth analysis or performance results. Rather, the interested reader is referred to the extensive list of references.

1997 - Joint phase and timing recovery with CPM signals [Relazione in Atti di Convegno]
M., Morelli; U., Mengali; Vitetta, Giorgio Matteo
abstract

We describe an algorithm for joint timing and carrier phase recovery with CPM signaling. The proposed method may be employed with any CPM format and with either full or reduced state detectors. It can be implemented in digital form with a limited computational complexity. Simulation results show that its tracking performance is excellent. However, when operated in its simplest form, it may exhibit false locks during acquisition. In particular, this happens with multilevel partial response formats. A simple solution to false locks is proposed.

1997 - Joint phase and timing recovery with CPM signals [Articolo su rivista]
M., Morelli; U., Mengali; Vitetta, Giorgio Matteo
abstract

We describe joint carrier phase and timing recovery algorithms for CPM signaling. They may be employed with any CPM format, and with either full or reduced state detectors. Their implementation is fully digital, and involves a limited computational complexity. Simulation results show that these algorithms have excellent tracking performance. When operated in their simplest form, however, they may exhibit false locks. In particular, this occurs with multilevel and partial response formats. A simple solution to the false lock problem is proposed.

1997 - Noncoherent detection of FSK signals transmitted over linearly time-selective Rayleigh fading channels [Relazione in Atti di Convegno]
Vitetta Giorgio, M.; Mengali, Umberto; Taylor Desmond, P.
abstract

Linearly time-varying fading models are used to investigate noncoherent detection of FSK signals transmitted over frequency-flat fading channels. The structure of the optimal noncoherent FSK detector is derived and a novel analytical technique is proposed to compute the error performance of noncoherent FSK detectors in fast fading. Error performance results obtained by computer simulation are in excellent agreement with the analytical predictions.

1997 - Optimal noncoherent detection of FSK signals transmitted over linearly time-selective Rayleigh fading channels [Articolo su rivista]
Vitetta, Giorgio Matteo; U., Mengali; D. P., Taylor
abstract

Linearly time-varying fading models are used to investigate noncoherent detection of frequency shift keying (FSK) signals transmitted over frequency-flat fading channels. The structure of the optimal noncoherent FSK detector is derived and a novel analytical technique is proposed to compute the error performance of noncoherent FSK detectors in fast fading. Error performance results obtained by computer simulation are in excellent agreement with the analytical predictions.

1996 - A blind detection technique for CPM signals transmitted over frequency-flat fading channels [Relazione in Atti di Convegno]
Vitetta, Giorgio Matteo; Mengali, U.; Taylor, D. P.
abstract

We propose a novel detection technique for CPM signals transmitted over frequency-flat fading channels. Its most significant feature is that it operates without statistical information on the fading channel and, for this reason, it is nicknamed “blind detector”. Its error rate performance is assessed with CPFSK schemes and is compared with the performance of other decoders

1996 - Double-filtering receivers for PSK signals transmitted over Rayleigh frequency-flat fading channels [Articolo su rivista]
Vitetta, Giorgio Matteo; U., Mengali; D. P., Taylor
abstract

This paper describes novel detection algorithms for coded and uncoded M-ary phase shift keying (M-PSK) signals transmitted over frequency-flat fading channels. Fading distortion is estimated with per-survivor methods using the sampled outputs of two receive filters. Some of the proposed algorithms do not require information on the fading statistics and are dubbed blind algorithms. The error rate performance of blind and nonblind algorithms is assessed by simulation for uncoded and trellis-coded phase shift keying (PSK) and is compared to the performance of other detection schemes proposed in the literature.

1996 - MULTISAMPLING RECEIVERS FOR UNCODED AND CODED PSK SIGNAL SEQUENCES TRANSMITTED OVER RAYLEIGH FREQUENCY-FLAT FADING CHANNELS [Articolo su rivista]
Vitetta, Giorgio Matteo; D. P., Taylor
abstract

An algorithm, based on previous work [Vitetta and Taylor 1994, 1995], for the detection of coded and uncoded PSK sequences transmitted on a frequency-flat fading channel is investigated. It is based on the Viterbi algorithm and processes more than one signal sample per signaling interval. Its performance is evaluated by means of computer simulations for both uncoded and coded systems.

1995 - Blind receivers for PSK signals transmitted over Rayleigh frequency-flat fading channels [Relazione in Atti di Convegno]
Vitetta, Giorgio Matteo; D. P., Taylor; U., Mengali
abstract

This paper describes detection algorithms for coded and uncoded M-PSK signals transmitted over frequency-flat fading channels. Fading distortion is estimated with per-survivor methods using the outputs of two receive filters. The proposed algorithms do not require information on the fading statistics and are dubbed blind algorithms. The error-rate performance is assessed by simulation for uncoded and trellis-coded PSK and is compared with the performance of previously proposed detection schemes

1995 - Maximum likelihood decoding of uncoded and coded PSK signal sequences transmitted over Rayleigh flat-fading channels [Articolo su rivista]
Vitetta, Giorgio Matteo; D. P., Taylor
abstract

The problem of maximum likelihood (ML) detection for uncoded and coded M-PSK signals on Rayleigh fading channels is investigated. It is shown that, if the received signal is sampled at baud-rate, a ML receiver employing per-survivor processing can be implemented. The error rate performance of this receiver is evaluated by means of computer simulations and its limitations are discussed. In addition, it is shown that, on a fast fading channel, the error floor in the BER curve can be appreciably lowered if more than one received signal sample per symbol interval is processed by the receiver algorithm, Finally, a sub-optimum two-stage receiver structure for interleaved coded PSK systems is proposed. Its error rate performance is assessed for simple trellis-coded modulation schemes and compared to that provided by other receiver structures.

1995 - Maximum Likelihood Sequence Estimation of Differentially Encoded PSK Signals Transmitted over Rayleigh Frequency-Flat Fading Channels [Articolo su rivista]
Vitetta, Giorgio Matteo; Taylor, D. P.
abstract

The problem of maximum likelihood (ML) detection of differentially encoded M-PSK signals on Rayleigh fading channels is investigated. It is shown that the solution to this problem can be easily related to previous results [1] and leads to the implementation of a receiver structure based on the Viterbi algorithm and employing per-survivor processing. The error rate performance of this receiver is evaluated by computer simulations for both coded and uncoded systems.

1995 - Viterbi decoding of differentially encoded PSK signals transmitted over Rayleigh frequency-flat fading channels [Articolo su rivista]
Vitetta, Giorgio Matteo; D. P., Taylor
abstract

Maximum Likelihood (bit) detection of differentially encoded M-PSK signals on Rayleigh fading channels is investigated. It is shown that the solution to this problem can be related to previous results [Vitetta and Taylor, 1994] and leads to the implementation of a receiver structure based on the Viterbi algorithm and employing per-survivor processing. The error rate performance of this receiver is evaluated by means of computer simulations for both trellis-coded and uncoded systems.

1994 - Approximate ML decoding of coded PSK with no explicit carrier phase reference [Articolo su rivista]
A. N., D'Andrea; U., Mengali; Vitetta, Giorgio Matteo
abstract

An approximate method is discussed for maximum likelihood estimation of coded PSK sequences in the presence of an unknown carrier phase. This method makes use of the Viterbi algorithm to find an optimum path in the encoder trellis diagram. Phase estimation is embedded into the structure of the detection algorithm and the branch metrics in the trellis are modified with respect to those employed with known carrier phase. Comparisons with traditional decoding schemes show that the proposed solution has better performance in terms of acquisition time and cycle slips

1994 - Maximum likelihood detection of differentially encoded PSK signals transmitted over Rayleigh frequency-flat fading channels [Relazione in Atti di Convegno]
Vitetta, Giorgio Matteo; D. P., Taylor
abstract

The problem of maximum likelihood (ML) detection of differentially encoded M-PSK signals on Rayleigh fading channels is investigated. It is shown that the solution to this problem can be easily related to previous results [Vitetta and Taylor, 1994] and leads to the implementation of a receiver structure based on a Viterbi Algorithm. The error rate performance of this receiver is evaluated by means of computer simulations for both coded and uncoded systems.

1994 - Maximum likelihood sequence estimation of uncoded and coded PSK signals transmitted over Rayleigh flat-fading channels [Relazione in Atti di Convegno]
Vitetta, Giorgio Matteo; D. P., Taylor
abstract

The problem of maximum likelihood (ME) detection for uncoded and coded M-PSK signals on Rayleigh fading channels is investigated. It is shown that, if the received signal is sampled at baud rate, a ML receiver can be implemented. The error rate performance of this receiver is evaluated by means of computer simulations and its limitations are discussed. Moreover, it is shown that, on a fast fading channel, the error floor in the BER curve can be appreciably lowered if more than one received signal sample per symbol interval is processed by the receiver decoder. Finally, it is proved that, on fast fading channels, the use of PSK trellis-codes without the interleaving-deinterleaving subsystems can provide substantial gains over uncoded PSK systems with the same information rate

1994 - Some new rotationally invariant TCM schemes for multidimensional M-PSK [Articolo su rivista]
Vitetta, Giorgio Matteo
abstract

Trellis codes for multidimensional constellations offer a number of advantages which cannot be obtained with bidimensional constellations. Some new trellis codes for multidimensional M-PSK constellations are presented. They are all completely rotationally invariant. The performance of these codes is discussed and compared with that exhibited by Ungerboeck codes for bidimensional phase modulation with the same effective rate.

1993 - Multiple Phase Synchronization in Continuous Phase Modulation [Articolo su rivista]
A. N., D'Andrea; U., Mengali; Vitetta, Giorgio Matteo
abstract

This paper illustrates decoding algorithms wherein carrier phase recovery is accomplished by means of an array of synchronizers, instead of a single synchronizer as happens in conventional schemes. Algorithms with multiple synchronization are compared with others (traditional and untraditional) in terms of implementation complexity and error probability. It turns out that, in the presence of phase jitter, multiple phase tracking provides better performance than single phase tracking, with a limited increase in the overall processing load of the decoder.

1993 - Multiple phase synchronization in CPM signals [Relazione in Atti di Convegno]
A. N., D'Andrea; U., Mengali; Vitetta, Giorgio Matteo
abstract

1992 - Efficient Modulation Techniques for Satellite Telemetry - Receiver Design and Performance Evaluation [Articolo su rivista]
M., Luise; R., Reggiannini; Vitetta, Giorgio Matteo
abstract

In this paper we address the design of the data demodulator for high-efficiency satellite communications suited for telemetry applications. We choose Gaussian minimum shift keying as the modulation format and analyse its relative merits with respect to the more traditional filtered offset quadrature phase-shift keying scheme, when applied to medium-to-high data rate telemetry. Our study encompasses both geostationary orbits and the more challenging low earth orbit scenarios, and investigates the acquisition and tracking performance of the receiver with the aid of computer simulations. In particular, we present design criteria leading to the development of efficient, low-complexity schemes for symbol timing and carrier phase/frequency recovery and we analyse the impact of these synchronization algorithms on the system performance. Next, we discuss the demodulator performance degradation when the transmitted signal is passed through on-board solid-state or travelling-wave-tube power amplifiers. The paper is concluded by a comparative analysis of the above modulation schemes, with special emphasis on their power and spectral efficiency.

Università degli studi di Modena e Reggio Emilia

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