The open, virtualized, and disaggregated nature of Open Radio Access Network (O-RAN) designs has brought new security issues to mobile networks. Strong and flexible security measures are required in response to these issues, and the integration with existing IT security tools such as Security Information and Event Management (SIEM) systems may represent a viable solution. The method for combining SIEM with O-RAN is presented in this study in order to improve security threat detection and mitigation in mobile and IT settings. In order to improve real-time anomaly detection and reaction, the proposed system will design a specific xApp that acts as an agent to pass events from mobile networks to the SIEM. This would address threats like jamming and Distributed Denial of Service (DDoS) assaults. In addition to improving Intrusion Detection Systems' (IDS) capabilities, SIEM integration with O-RAN offers a dynamic and intelligent security architecture that can react quickly to threats that are always changing in both IT and mobile infrastructures. This study shows how O-RAN and SIEM technology can be combined to protect next-generation mobile networks against advanced cyberattacks.

This work introduces a standardized and lightweight abstraction framework for Deep Audio Embedding Neural Networks. Designed with edge and embedded scenarios in mind, the framework enables seamless integration, inference, and performance profiling of a large set of pre-trained Audio NNs, across diverse downstream domains and platforms, by introducing a unified API and an open-contributing configuration schema. This interface allows each model to be instantiated and executed through an easy interpretable descriptor, without altering the original developers source code. The proposed framework supports fully automated benchmarking orchestration in a cloud-based environment, with the aim of a modular infrastructure built on Amazon Web Services, which processes community-contributed model configurations and evaluates them on server-grade hardware. Benchmark profiling includes inference (CPU/GPU) timing, energy efficiency, and memory usage monitoring, minimizing runtime overhead and enabling fair comparison across implementations: results are aggregated into a real-time leaderboard and within technical model cards, accessible through a dedicated web interface. This initiative lays the groundwork for a community-driven benchmarking challenge, encouraging experimental reproducibility, scalability, and models cross-compatibility for real-world audio intelligence applications.

Urban Air Mobility (UAM) represents an innovative mobility solution designed to alleviate the traffic congestion associated with conventional two-dimensional transportation, which has already saturated both urban and underground spaces. The development of unmanned aerial vehicles (UAVs) and electric vertical takeoff and landing (eVTOL) aircraft is a key enabler for this new, sustainable mode of transporting goods and passengers. To ensure safe operation—especially as these vehicles advance toward autonomous capabilities—and to maintain connectivity for passengers, UAM requires high data-rate, reliable, and low-latency communications. Within the 6G framework, several architectural solutions have been proposed, incorporating components such as terrestrial stations, satellites, and UAVs. In this paper, we propose a two-tier architecture: an aerial tier that leverages multi-hop THz communications among UAM vehicles as backhaul links, and a terrestrial tier comprising conventional cellular base stations (BSs) along with a number of enhanced base stations (eBSs) equipped with high-elevation antenna systems to provide aerial coverage for UAM vehicles (UVs). We will show that our approach ensures reliable UAM connectivity even in high-density urban airspaces, striking an optimal balance between the required number of eBSs and the airborne THz backhauling.

Ensuring seamless connectivity for first responders represents a critical issue in emergency scenarios, where disrupted infrastructures and network congestion can significantly hinder the communication. Open Radio Access Network (O-RAN) promises a level of openness in Radio Access Networks (RANs) that could be advantageous under such critical conditions, allowing for enhanced integration across different operators’ networks to mitigate resource scarcity. This paper introduces an architectural solution based on O-RAN that leverages neutral hosting to provide a unified gateway to RAN infrastructures. Our approach facilitates seamless access for emergency responders and optimizes the allocation of resources at both the RAN and Core levels within a specified area by exploiting the deployment of near-real-time Applications (xApps) and non-real-time Applications (rApps) managed by the neutral host. The results demonstrate the effectiveness of O-RAN neutral hosting in enhancing first responders’ connectivity, showcasing significant improvements in throughput and latency, especially under disaster scenarios. • O-RAN Neutral Hosting is a feasible solution for emergency operator connectivity. • First responders seamlessly communicate through efficient radio resource allocation. • O-RAN Neutral Hosting outperforms traditional RAN before and after the disaster. • Slice isolation strategy further amplifies the advantages of O-RAN Neutral Hosting.

The adoption of Time Division Duplexing (TDD) in 5G not only facilitates efficient spectrum utilization but also paves the way for the implementation of innovative schemes that leverage the unique characteristics of the TDD patterns. For example, Cooperative Dynamic Bandwidth Allocation (CO DBA) exploits information about the TDD pattern to reduce latency in Time Division Multiplexing Passive Optical Networks (TDM-PON)-based fronthaul. In this paper, we harness the information about 5G TDD patterns alongside the programmability offered by Open Radio Access Network (O-RAN) and Software Defined Optical Access Networks (SDOANs) for a different purpose: enhancing x-haul energy efficiency. The scheme we propose seeks to minimize the energy consumption of PON-based x-haul networks by dynamically adjusting the operational states of selected subsystems within the Optical Network Terminal (ONT) in coordination with the TDD patterns. Preliminary simulation results show that up to 80% energy savings can be achieved with the proposed cooperative technique.

Today mobile communications have evolved from merely connecting devices to enabling a wide range of heterogeneous services, particularly with 5G networks. The rise of multimedia services and digital content consumption is driving the proliferation of wireless devices, which in turn is increasing the complexity of resource management. In this scenario, a distributed system could be the most effective way to manage this complex environment for monitoring and support purposes, especially through Software Defined Radio (SDR) technology. This paper introduces a distributed SDR-based system designed to perform various services to monitor and support any mobile communication systems. After presenting the overall design of the proposed system, this work will describe and test a prototype that can execute a monitoring service for spectral analysis, interference detection, and localization.

With the advent of advanced communication technologies like 5G and the emergence of the Internet of Everything, there is a growing potential to leverage public communication networks for mission-critical applications. Traditionally, these applications have depended on private, narrowband networks such as TETRA and P25. The latest communication protocols and architectures promise specific levels of latency and reliability even during the negotiation phase. Concurrently, the increasing deployment of sensors for Structural Health Monitoring (SHM) offers access to vast data volumes at low costs and near real-time capabilities when required. This paper highlights the significant benefits of integrating these two paradigms in the context of Earthquake Early Warning (EEW) systems. Utilizing existing earthquake propagation models and recorded seismic data, we have developed a new simulator tailored to mimic a densely packed sensor network environment. We introduce a consensus algorithm that processes the initial milliseconds of data collected by sensors nearest to the earthquake’s hypocenter. An alert is then promptly issued. Our results indicate substantial improvements in reducing the time to relay warnings, thereby significantly diminishing the extent of the blind zone, where warnings arrive too late, in EEW systems.

Network and computing infrastructures are nowadays challenged to meet the increasingly stringent requirements of novel applications. One of the most critical aspect is optimizing the latency perceived by the end-user accessing the services. New network architectures offer a natural framework for the efficient orchestration of microservices. However, how to incorporate accurate latency metrics into orchestration decisions still represents an open challenge.In this work we propose a novel architectural approach to perform scheduling operations in Kubernetes environment. Existing approaches proposed the collection of network metrics, e.g. latency between nodes in the cluster, via purposely-built external measurement services deployed in the cluster. Compared to other approaches the proposed one: (i) collects performance metrics at the application layer instead of network layer; (ii) relies on latency measurements performed inside the service of interest instead of utilizing external measurement services; (iii) takes scheduling decisions based on effective end-user perceived latency instead of considering the latency between cluster nodes.We show the effectiveness of our approach by adopting an iterative discovery strategy able to dynamically determine which node operates with the lowest latency for the Kubernetes pod placement.

Contemporary technologies as implemented in the field of healthcare have provided the everyday clinical practice with a plethora of tools to be used in various settings. In this field, distributed and networked embedded systems, such as Wireless Sensor Networks (WSNs), are the most promising technology to achieve continuous monitoring of aged people for their own safety, without affecting their daily activities. WSN4QoL is a Marie Curie project involving academic and industrial partners from three EU countries, which aims to show how new WSNs-based technologies suit the specific requirements of pervasive healthcare applications. In particular, in this paper, the WSN4QoL's system architecture is presented as designed to exploit the Network Coding (NC) mechanisms to achieve energy efficiency in the wireless communications and distributed positioning solutions to locate patients in indoor home environments. The system has been validated through experimental activities using commercial off the shelf (COTS) WSN testbeds and medical devices prototypes offered by a commercial partner. Results demonstrate that NC helps in achieving substantial gains in terms of energy efficiency as compared to traditional relay mechanisms, while the proposed positioning solution is able to locate people in indoor environments at a sub-room accuracy level, without requiring any extra dedicated hardware.

Cultural Heritage represents a resource of inestimable value in Italy. This work presents a project to allow people affected by specific mental disabilities to enjoy the experience of an exhibition, by exploiting experienced AAL technological solutions. Basing on the results obtained by Casa+, a project to support daily life of people affected by the Down syndrome, we designed and developed a system based on a flexible architecture providing a set of context-aware applications for assisting people with cognitive disabilities to experiment an autonomous cultural experience. This is achieved allowing a safe location reaching through outdoor navigation and an assisted personal experience inside the exhibition building. In particular, we propose a location-aware mobile navigation system that integrates a consecutive point navigation system for outdoor navigation and an indoor navigation system that integrates recommendation mechanisms based on the localization information. A case study for a real single smart space and some preliminary experimental results are presented and discussed.

This paper presents a novel algebraic framework of collaborative network channel coding scheme in a network with multiple-access relay channel. The proposed scheme helps reduce the computational complexity while enhancing energy efficiency of the wireless network. The devised scheme is intended

Spatial Modulation (SM) is a recently proposed single-RF multiple-input-multiple-output (MIMO) technique, which is capable of outperforming many conventional MIMO transmission schemes with low implementation and computational complexity. Recently, there have been some attempts in understanding the performance of SM in multi-user environments. However, most of the work has been oriented towards uplink multi-access scenarios. Also, conventional downlink/broadcast MIMO precoding techniques such as Zero Forcing (ZF) or Minimum Mean Square Error (MMSE) cannot be used in Multi-User SM (MU-SM), as part of the data in SM is also encoded into the Channel Impulse Responses (CIRs). In this paper, a novel precoding scheme for single-cell downlink MU-SM systems is proposed with a two-fold objective: i) the precoder needs to be able to completely eliminate the Multi-User Interference (MUI) by taking advantage of the Channel State Information (CSI) at the transmitter and ii) it needs to allow the users to use a single-user Maximum Likelihood (ML) optimum detector while achieving the same performance as interference-free point-to-point SM transmission. Finally, we also develop an interference-aware multi-user detection scheme, which does not require any CSI at the transmitter, and compare its performance with that of single-user detection schemes based on precoding.

Life expectancy is projected to increase significantly in the coming years. This fact has pushed the need for designing new and more pervasive healthcare systems. In this field, distributed and networked embedded systems, such as Wireless Sensor Networks (WSNs), are the most suitable technology to achieve continuous monitoring of aged people for their own safety, without affecting their daily activities. This paper proposes recent advancements in this field by introducing WSN4QoL, a Marie Curie project which involves academic and industrial partners from three EU countries. The project aims to propose new WSN-based technologies to meet the specific requirements of pervasive healthcare applications. In particular, in this paper, a Network Coding (NC) mechanism and a distributed localization solution are presented. They have been implemented on WSN testbeds to achieve efficiency in the communications and to enable indoor people tracking. Preliminary results in a real environment show good system performance that meet our expectations.

Wireless Sensor Networks (WSNs) are fostering pervasive healthcare applications, where people are remotely monitored, without the full time assistance of professional care-givers. A key enabling element is the possibility to locate people in indoor environments, especially in emergency situations. Framed within the WSN4QoL project, this paper proposes the use of a ray tracing model for network planning, to support efficient people localization and performance analysis. Preliminary results show accurate radio coverage estimations, with a minimal calibration effort.

A cooperative diversity protocol for multi-relay wireless networks is proposed. Its distinguishable feature is to protect the transmission of the source through distributed diversity while simultaneously serving the data traffic of the relays. Therefore, the performance of the source is improved without reducing the aggregate throughput. The protocol exploits a recently introduced concept for multiple- antennas wireless systems, which is known as Spatial Modulation (SM). The contribution of this paper is threefold: i) the optimal receiver that takes into account demodulation errors at the relays is developed; ii) its achievable diversity is studied analytically; and iii) it is shown, with the help of Monte Carlo simulations, that it outperforms state- of-the-art cooperative diversity protocols.

In this paper, we contribute to the theoretical understanding, the design, and the performance evaluation of multi—source multi—relay network—coded cooperative diversity protocols. These protocols are useful to counteract the spectral inefficiency of repetition—based cooperation. We provide a general analytical framework for analysis and design of wireless networks using the Demodulate—and—Forward (DemF) protocol with binary Network Coding (NC) at the relays and Cooperative Maximal Ratio Combining (C—MRC) at the destination. Our system model encompasses an arbitrary number of relays which offer two cooperation levels: i) full—cooperative relays, which postpone the transmission of their own data frames to help the transmission of the sources via DemF relaying and binary NC; and ii) partial—cooperative relays, which exploit NC to transmit their own data frames along with the packets received from the sources. The relays can apply NC on different subsets of sources, which is shown to provide the sources with unequal diversity orders. Guidelines to choose the packets to be combined, i.e., the network code, to achieve the desired diversity order are given. Our study shows that partial—cooperative relays provide no contribution to the diversity order of the sources. Theoretical findings and design guidelines are validated through extensive Monte Carlo simulations.

In this paper, we study the performance of network-coded cooperative diversity systems with practical communication constraints. More specifically, we investigate the interplay between diversity, coding, and multiplexing gain when the relay nodes do not act as dedicated repeaters, which only forward data packets transmitted by the sources, but they attempt to pursue their own interest by forwarding packets which contain a network-coded version of received and their own data. We provide a very accurate analysis of the Average Bit Error Probability (ABEP) for two network topologies with three and four nodes, when practical communication constraints, i.e., erroneous decoding at the relays and fading over all the wireless links, are taken into account. Furthermore, diversity and coding gain are studied, and advantages and disadvantages of cooperation and binary Network Coding (NC) are highlighted. Our results show that the throughput increase introduced by NC is offset by a loss of diversity and coding gain. It is shown that there is neither a coding nor a diversity gain for the source node when the relays forward a network-coded version of received and their own data. Compared to other results available in the literature, the conclusion is that binary NC seems to be more useful when the relay nodes act only on behalf of the source nodes, and do not mix their own packets to the received ones. Analytical derivation and findings are substantiated through extensive Monte Carlo simulations.

In this paper, we study the performance of space modulation for Multiple-Input-Multiple-Output (MIMO) wireless systems with imperfect channel knowledge at the receiver. We focus our attention on two transmission technologies, which are the building blocks of space modulation: i) Space Shift Keying (SSK) modulation; and ii) Time-Orthogonal-Signal-Design (TOSD-) SSK modulation, which is an improved version of SSK modulation providing transmit-diversity. We develop a single-integral closed-form analytical framework to compute the Average Bit Error Probability (ABEP) of a mismatched detector for both SSK and TOSD-SSK modulations. The framework exploits the theory of quadratic-forms in conditional complex Gaussian Random Variables (RVs) along with the Gil-Pelaez inversion theorem. The analytical model is very general and can be used for arbitrary transmit- and receive-antennas, fading distributions, fading spatial correlations, and training pilots. The analytical derivation is substantiated through Monte Carlo simulations, and it is shown, over independent and identically distributed (i.i.d.) Rayleigh fading channels, that SSK modulation is as robust as single-antenna systems to imperfect channel knowledge, and that TOSD-SSK modulation is more robust to channel estimation errors than the Alamouti scheme. Furthermore, it is pointed out that only few training pilots are needed to get reliable enough channel estimates for data detection, and that transmit- and receive-diversity of SSK and TOSD-SSK modulations are preserved even with imperfect channel knowledge.

In this paper, we propose a simple analytical methodology to study the performance of multi-source multi-relay cooperative wireless networks with network coding at the relay nodes and Maximum-Likelihood (ML-) optimum channel-aware detectors at the destination. Channel-aware detectors are a broad class of receivers that account for possible decoding errors at the relays, and, thus, are inherently designed to mitigate the effect of erroneous forwarded and network-coded data. In spite of the analytical complexity of the problem at hand, the proposed framework turns out to be simple enough yet accurate and insightful to understand the behavior of the system, and, in particular, to capture advantages and disadvantages of various network codes and the impact of error propagation on their performance. It is shown that, with the help of cooperation, some network codes are inherently more robust to decoding errors at the relays, while others better exploit the inherent spatial diversity and redundancy provided by cooperative networking. Finally, theory and simulation highlight that the relative advantage of a network code with respect to the others might be different with and without decoding errors at the relays.

In this paper, we study the sensitivity and robustness of Space Shift Keying (SSK) modulation to imperfect channel knowledge at the receiver. Unlike the common widespread belief, we show that SSK modulation is more robust to imperfect channel knowledge than other state-of-the-art transmission technologies, and only few training pilots are needed to get reliable enough channel estimates for data detection. More precisely, we focus our attention on the so-called Time-Orthogonal-Signal-Design (TOSD-) SSK modulation scheme, which is an improved version of SSK modulation offering transmit-diversity gains, and provide the following contributions: i) we develop a closed-form analytical framework to compute the Average Bit Error Probability (ABEP) of a mismatched detector for TOSD-SSK modulation, which can be used for arbitrary transmit-antenna, receive-antenna, channel fading, and training pilots; ii) we perform a comparative study of the performance of TOSD-SSK modulation and the Alamouti code under the same imperfect channel knowledge, and show that TOSD-SSK modulation is more robust to channel estimation errors; iii) we point out that only few pilot pulses are required to get performance very close to the perfect channel knowledge lower-bound; and iv) we verify that transmit- and receive-diversity gains of TOSD-SSK modulation are preserved even for a mismatched receiver.

Knowing exactly where a mobile entity is and monitoring its trajectory in real-time has recently attracted a lot of interests from both academia and industrial communities, due to the large number of applications it enables, nevertheless, it is nowadays one of the most challenging problems from scientific and technological standpoints. In this work we propose a tracking system based on the fusion of position estimations provided by different sources, that are combined together to get a final estimation that aims at providing improved accuracy with respect to those generated by each system individually. In particular, exploiting the availability of a Wireless Sensor Network as an infrastructure, a mobile entity equipped with an inertial system first gets the position estimation using both a Kalman Filter and a fully distributed positioning algorithm (the Enhanced Steepest Descent, we recently proposed), then combines the results using the Simple Convex Combination algorithm. Simulation results clearly show good performance in terms of the final accuracy achieved. Finally, the proposed technique is validated against real data taken from an inertial sensor provided by THALES ITALIA.

In this paper, we propose Unequal Error Protection (UEP) coding theory as a viable and flexible method for the design of network codes for multi-source multi-relay cooperative networks. As opposite to state-of-the-art solutions available for improving the diversity gain of cooperative networks, it is shown that the proposed method allows us to assign each source node the desired diversity gain, according to, e.g., the requested Quality of Service (QoS) or power constraints. The diversity advantage of the UEP-based network code design over conventional relay-only and XOR-only solutions is shown for the canonical two-source two-relay network. Furthermore, Maximum-Likelihood (ML-) optimum channel-aware receivers for multi-source multi-relay cooperative networks are developed, and their Average Bit Error Probability (ABEP) and achievable diversity over fading channels analytically studied. It is shown that only a cross-layer (joint) implementation of demodulation and network-decoding allows the destination to fully exploit the diversity inherently provided by the distributed network code. Finally, analytical derivations and findings are substantiated via Monte Carlo simulations.

The demonstration proposal moves from the capabilities of a wireless biometric badge [4], which integrates a localization and tracking service along with an automatic personal identification mechanism, to show how a full system architecture is devised to enable the control of physical accesses to restricted areas. The system leverages on the availability of a novel IEEE 802.15.4/Zigbee Cluster Tree network model, on enhanced security levels and on the respect of all the users' privacy issues.

In this paper, we describe GREENET (an early stage training network in enabling technologies for green radio), which is a new project recently funded by the European Commission under the auspices of the 2010 Marie Curie People Programme. Through the recruitment and personalized training of 17 Early Stage Researchers (ESRs), in GREENET we are committed to the development of new disruptive technologies to address all aspects of energy efficiency in wireless networks, from the user devices to the core network infrastructure, along with the ways the devices and equipment interact with one another. Novel techniques at the physical, link, and network layers to reduce the energy consumption and carbon footprint of 4G devices will be investigated, such as Spatial Modulation (SM) for Multiple-Input-Multiple-Output (MIMO) systems, Cooperative Automatic Repeat reQuest (C-ARQ) protocols, and Network Coding (NC) for lossy networks. Furthermore, cooperation and cognition paradigms will be exploited as additional assets to improve the energy efficiency of wireless networks with the challenging but indispensable constraint of optimizing the system capacity without degrading the user's Quality-of-Service (QoS).

Since the pioneering research work of Ahlswede et al. in 2000, Network Coding (NC) has rapidly emerged as a major research area in electrical engineering and computer science due to its wide applicability to communication through real networks. The many contributions available in the literature to date, ranging from pure theoretical studies on fundamental limits to practical experimentations in real-world environments, offer a clear evidence that the shift in paradigm envisaged by NC might revolutionize the way we manage, operate, and understand the organization of networks. NC allows intermediate nodes of communication networks to combine the information received from multiple links for subsequent transmissions, and offer a powerful and efficient generalization to network information delivery via routing, where network nodes simply store and forward data, and processing is only accomplished at the end nodes. In this paper, we have a twofold objective: i) first, we summarize fundamental information-theoretic results, which, since their publication, have been representing the foundation for all subsequent research in this field, and ii) then, we introduce and summarize the latest results related to the analysis, design, and optimization of the so-called network error correction coding problem, which is instrumental for the effective use of NC over lossy, e.g., wireless networks.

The demo we propose represents a first step toward RF Sounding [1]. Such a project is an open space installation which comprises both artistic and technological innovations; its aim is to provide the user, while entering a specifically defined area, with awareness of radio frequency signals characterizing the cellular networks band. Indeed, radio signals are shifted, with proper elaboration, to the audible band and the result is spread all over the specific area through a certain number of loudspeakers. For this procedure we have been inspired by the eternal metaphor of the impossible human dream to fly, thus the limitations of our senses which are capable of feeling audio waves (sounds) but (maybe luckily) are not capable of directly feeling radio frequency (RF) waves are highlighted. The translation is the starting point for a more complex and exciting musical composition. It has to be underlined that some features of RF sensed signals are kept unchanged in order to give to the listener the clear feeling of the amount (power) of RF signals present in the monitored area. The aim of this project is twofold. Indeed, from one side we want to increase end users knowledge of the strength of the power emitted by their cellular phones with respect to the electromagnetic fields produced in the environment, on the other hand we want to provide for an artistic and interactive installation that can also be remotely joined through a web interface.

In this paper, we propose a comprehensive framework for performance analysis of multi-hop multi-branch wireless communication systems over log-normal fading channels. The framework allows to estimate the performance of amplify and forward (AF) relay methods for both channel state information (CSI-) assisted relays, and fixed-gain relays. In particular, the contribution of this paper is twofold: i) first of all, by relying on the Gauss quadrature rule (GQR) representation of the moment generation function (MGF) for a log-normal distribution, we develop accurate formulas for important performance indexes whose accuracy can be estimated a priori and just depends on GQR numerical integration errors; ii) then, in order to simplify the computational burden of the former framework for some system setups, we propose various approximations, which are based on the Improved Schwartz-Yeh (I-SY) method. We show with numerical and simulation results that the proposed approximations provide a good trade-off between accuracy and complexity for both Selection Combining (SC) and Maximal Ratio Combining (MRC) cooperative diversity methods.

In this paper, we investigate the performance of a general multi-layer decentralized system setup for cooperative spectrum sensing, which includes realistic sensing/reporting channels and correlated log-normal shadow-fading in all wireless links of the cooperative network. Our investigations will show that, even though often overlooked in typical cooperative spectrum sensing analysis, shadowing correlation on the reporting channel can yield similar performance degradations as shadowing correlation on the sensing channel. All findings will be substantiated via theoretical arguments and Monte Carlo simulations, and, in particular, novel approximation methods to account for correlated Log-Normal shadowing in cooperative spectrum sensing problems will be introduced.

We propose a comprehensive theoretical framework to evaluate reliability and energy consumption of distributed source coding (DSC) in wireless sensor networks (WSNs) applications. Energy efficiency and the amount of measurements that can be successfully decoded in tree-based WSNs employing DSC in the presence of different coding topologies and packet aggregation schemes (PA) are accurately characterized. The system model includes a realistic network architecture with multi-hop communication, automatic repeat request protocol (ARQ), packet losses due to channel impairments and collisions, and correlation properties of the sensed phenomena. Four DSC topologies and three alternatives of PA are considered. The analysis is carried out by evaluating the expressions of reliability of DSC in terms of probability of measurements that cannot be decoded (loss factor), and the efficiency in terms of average energy consumption of the network. Numerical results show that the best choice of DSC topology and packet aggregation depends highly on the network parameters and source characteristics. Therefore, the analysis developed in this paper can be used as an effective mean to optimize network operations.

In this paper, a general framework for performance evaluation of cooperative spectrum sensing methods over realistic propagation environments is proposed. In particular, the framework accounts for correlated Log-Normal shadowing in both sensing and reporting channels, and yields simple and easy-to-use formulas for computing the Detection Probability of a distributed network of secondary users using Amplify and Forward (AF) relying for data reporting to the fusion center. Numerical results are also shown to substantiate the accuracy of the proposed framework.

The demonstration proposal focuses on presenting the capabilities of a wireless biometric badge, which integrates a localization and tracking service along with an automatic personal identification mechanism, to control the access to restricted areas with a high level of security. The wireless biometric badge is the result of R&D activities conducted by several professors, researchers, and students in the Center of Excellence in Research DEWS at the University of L' Aquila in Italy, as well as its R&D Spin-Off WEST Aquila S.r.l.

Wireless sensor networks (WSNs) play an important role in several application fields. They are composed by a dense deployment of small and low-power devices (called sensors) that cooperate together in order to perform some special tasks. These networks are often characterized by the spatial and temporal correlation of the sensor observations. Several works are investigating these correlations in order to design efficient communication protocols able to improve the performance of the networks. On these basis, it is necessary to: 1) extract the correlation function and 2) ensure that it is always valid, even if data are impaired by noise. The proposed approach is inspired to [1], where the authors have developed a new technique to robustly extract the statistical characteristics of process variations from experimental measurements in order to analyze and optimize the design of integrated systems. Our aim here is to investigate the correlation issue in the WSNs context where the data sensed by the nodes are usually correlated in the space and temporal domains. Motivated by this consideration, we propose a robust method to extract temporal correlation function parameters from noisy data gathered by a WSN and use some simulation results to validate our technique. Moreover, we analyze the reliability of our method with respect to the amount of collected measurement data and show that, on the basis of the obtained results, the temporal extraction process is efficient and robust in real cases.

A fundamental component to enable Dynamic Spectrum Access (DSA) capabilities in the future generation of wireless communication systems is the design of robust and efficient spectrum sensing methods to detect licensee users transmitting in a given frequency band. In this context, collaborative methods have been proposed to improve spectrum sensing capabilities over wireless channels, by counteracting shadow-fading phenomena via distributed diversity. However, recent results have shown that the expected benefits of cooperation, which are obtained at the expenses of increased traffic overhead and the need for a control channel, may be significantly hampered when the signals sensed by the cooperative users experience correlated shadow- fading. Moreover, it has been argued that spatial correlation of shadow-fading yields fundamental limits to the performance of cooperative spectrum sensing methods, and practical implications in terms of protocol design and network deployment. Motivated by the above considerations, in this paper we propose an analytical framework for the analysis and design of cooperative spectrum sensing methods over correlated shadow- fading environments, when each cooperative user is equipped with a simple energy-based detector. We will show that the framework requires efficient and accurate methods for modeling the power-sum of correlated Log-Normal Random Variables (RVs), which well describe shadowing phenomena. In particular, three main technical contributions can be found in the present paper: i) we generalize some recently proposed methods to approximate the power-sum of independent Log-Normal RVs to correlated scenarios, ii) we analyze the accuracy of several approximation techniques to compute detection probability over correlated Log-Normal shadowing, which is an unexplored field so far, and iii) we rely on the proposed framework to study the detrimental effect of correlation on the performance of cooperative spectrum sensing methods. Furthermore, numerical results will be shown to validate the proposed framework.

In this manuscript, we propose an accurate framework for the analysis of cooperative dual-hop wireless systems over fading channels, which use an Amplify and Forward (AF) relaying mechanism with fixed-gain relays. In particular, the proposed framework provides either exact results or very accurate bounds for computing the Moment Generating Function (MGF) of the end-to-end Signal-to-Noise Ratio (SNR) over Nakagami- m and Weibull fading. Furthermore, with the help of the MGF-based approach for performance analysis of wireless systems over fading channels, we will show that important performance indexes can be easily derived from the MGF. Numerical results will be shown to substantiate the proposed analytical framework.

Approximating the sum of log-normal random variables (RVs) is a long-standing open issue and many studies in the old and recent literature resort to assume that the "power sum" can be well modeled via another log-normal RV. Such a log-normal approximation can be effectively used for accurate outage probability (Pout) analysis and modeling of signal-to-(noise+interference) ratio (SNIR) behaviors in the context of radio resource management in wireless systems; nevertheless, it is recognized that i) an adequate accuracy can only be obtained for a sub-range of values taken by the distribution; ii) the achievable accuracy depends on the parameters of the set of RVs; iii) log-normal approximation may not provide a satisfactory accuracy for estimating bit error probabilities. Moreover, all contributions in the open technical literature are referred to model the "power sum" distribution, i.e., the weighted linear combination of log-normal RVs with weights that may take only positive values. While this setup is consistent with typical scenarios where summands add incoherently, it has recently been shown that in some high frequency-selective multipath channels with log-normal distributed shadow- and fast-fading, e.g., in impulse radio ultra wide band (IR-UWB) systems, the signal- to-noise ratio (SNR) is more accurately modeled by the weighted linear combination of log-normal RVs with weights that may assume both positive and negative values. Motivated by the above considerations, and moving from recent results, which show that approximating the "power sum" of log-normal RVs can boil down to a model selection problem within the pearson system of distributions, the specific contribution of this paper can be summarized as follows, i) We show that the pearson type IV distribution can not only be used to accurately approximate the probability density function (PDF) of the "power sum" of log-normal RVs with positive weights, but it can also accurately model the scenario with both positive and negative weights, as well as the scenario with generically correlated RVs. ii) For the scenario with independent RVs, we propose a numerical technique, which is based on the moment generating function (MGF) matching principle and uses a least- squares criterion, to accurately estimate the four parameters of the pearson type IV distribution, iii) A byproduct of this analysis.

In, we have recently proposed a general approach for approximating the power sum of Log-Normal Random Variables (RVs) by using the Pearson system of distributions. Therein, we have also highlighted the main advantages of using Pearson approximation instead of the usual Log-Normal one, and compared the proposed method with other approaches available in the open technical literature. However, despite being very accurate, the proposed method may be, in some circumstances, computational demanding since a non-linear least-squares problem needs to be solved numerically to get an accurate approximation. Motivated by the above consideration, the aim of this Letter is to provide an alternative approach for computing the parameters of the approximating Pearson distribution. The proposed solution is based on the Method of Moments (MoMs) in the logarithmic domain. In particular, by using some known properties of the Laplace transform, we will show that the MGF of the Log-Normal power sum in the logarithmic domain (denoted as log-MGF) can be obtained from the Mellin transform of the MGF of the Log-Normal power sum in the linear domain. From the estimated log-MGF, we will then compute the desired log-moments required for Pearson approximation. Numerical results will be also shown in order to substantiate the accuracy of the proposed method.

In this paper, we develop a general and unified framework for estimating the Cumulative Distribution Function (CDF) of "quadratic-form" receivers. The expression of the CDF that we finally achieve takes on the form of a single integral with finite limits and integrand composed of elementary functions, which can be readily integrated using standard techniques. In particular, the specific contribution of this manuscript is twofold: i) we present a comprehensive framework for the analysis of multi-channel reception systems using either non-coherent or differentially-coherent detectors, diversity systems with practical (i.e., noisy) channel estimators, and Transmitted-Reference (TR) receiver architectures working in frequency-selective fading channels, and ii) we show that the framework can be efficiently used for performance assessment of wireless systems over generalized fading channels and, under mild assumptions, over generalized fading channels further impaired by in-band multi-tone interference.

In this Letter, we propose a comprehensive framework for performance analysis of cooperative wireless systems using Amplify and Forward (AF) relay methods. The framework relies on the Moment Generating Function (MGF-) based approach for performance analysis of communication systems over fading channels, and on some properties of the Laplace Transform, which allow to develop a single-integral relation between the MGF of a random variable and the MGF of its inverse. Moreover, a simple lower bound for Outage Probability (Pout) and Outage Capacity (OC) computation is also introduced. Numerical and simulation results are provided to substantiate the accuracy of the proposed framework.

In the present contribution, we propose a comprehensive framework for the analysis of cooperative dual-hop wireless systems over generalized fading channels, which use an amplify and forward (AF) relaying mechanism with blind and semi-blind relays. In particular, the proposed framework provides either exact results or very accurate bounds for computing the moment generating function (MGF) of the end-to-end signal-to-noise ratio (SNR) for various fading channel models typically encountered in real propagation environments. Furthermore, with the help of the MGF-based approach for performance analysis of wireless systems over fading channels, we will show that important performance indexes can be easily derived from the MGF. With respect to previous published articles on the matter, the main contribution of the paper is twofold: i) by relying on the properties of the Meijer-G function, either exact expressions or accurate bounds for the MGF of the end-to-end SNR are provided, and ii) the analysis encompasses the vast majority of fading channel models. Numerical and simulation results will be compared to substantiate the analytical derivation.

In this Letter, we propose an advanced framework for performance analysis and design of decentralized data fusion problems. In particular, the performance of a multilayer system setup for data detection, which includes realistic sensing/reporting channels and correlated log-normal shadow-fading in all wireless links of the cooperative network, will be studied. The system setup will be used to analyze the performance of cooperative spectrum sensing problems adopting an amplify-and-forward (AF) relay protocol.We will show that, even though often overlooked in typical cooperative spectrum sensing analysis, shadowing correlation on the reporting channel can yield similar performance degradations as shadowing correlation on the sensing channel. All findings will be substantiated via theoretical arguments and Monte Carlo simulations, and, in particular, novel approximation methods to account for correlated log-normal shadowing in cooperative spectrum sensing problems will be introduced in this paper.

This paper focuses on the analysis of fundamental issues which has to be considered in order to gain voice from a wireless sensor network (WSN) that is assumed to be constituted by MicaZ wireless sensor nodes. Problems related to the transport of an audio signal through a wireless channel and sensor nodes are thus analyzed and a project for an audio surveillance system is presented.

In two recent contributions, we have provided a comparative analysis of various optimization algorithms, which can be used for atomic location estimation, and suggested an enhanced version of the Steepest Descent (ESD) algorithm, which we have shown to be competitive with other distributed localization algorithms in terms of estimation accuracy and numerical complexity. Moreover, therein we have conducted a preliminary statistical characterization of the positioning error distribution, by showing that it can be well approximated by the family of Pearson distributions, as well as pointed out that its knowledge may be efficiently used to speed-up the analysis of iterative-based positioning algorithms by avoiding the need of simulating the whole location discovery algorithm, and allowing simulation at the atomic level only. In this contribution, based on the preliminary results shown in, we propose a comprehensive statistical analysis of the positioning error distribution for the ESD algorithm, by providing the parameters of the Pearson fitting distribution with respect to two important design factors for wireless sensor networks (WSNs): i) the ranging error standard deviation, which represents the input parameter for every localization algorithm, and ii) the geometric dilution of precision factor, which provides a simple parameter to account for different network topologies. In particular, we report an extensive number of simulation results that may provide important insights to the system designer: i) allow a parametric analysis to figure out the joint effect of ranging errors and network topology on the performance of the localization algorithms, and ii) give a general framework for modeling the statistics of the positioning error, which may be used for network planning, as well as for the analysis and design of the upper layers of the protocol stack.

In recent years, there has been a growing interest in antenna sharing systems, and many analytical frameworks have been developed to analyze the performance of various relying protocols in a variety of propagation environments. However, among the different propagation scenarios, the less investigated are those characterized by log-normal fading. Motivated by this consideration, we propose a comprehensive framework for performance analysis of multi-hop multi-branch wireless systems over log-normal fading channels. More specifically, the developed framework allows to estimate the performance of amplify and forward (AF) relay methods for both channel state information (CSI-) assisted analog relays, and semi-blind and blind analog relays. In particular, the contribution of the paper is twofold: i) first of all, by relying on the Gauss quadrature rule (GQR) representation of the moment generation function (MGF) for a log-normal distribution, we develop very accurate formulas for important performance indexes; ii) then, in order to simplify the computational burden of the former framework for some system setups, we also propose an approximation, which is based on the improved Schwartz-Yeh (I-SY) method. We show with numerical and simulation results that the proposed approximation provides a good trade-off between accuracy and complexity.

Virtual antenna array (VAA) systems (also known as cooperative communications, cooperative diversity, cooperative relaying or antenna sharing systems) are a new and recently proposed kind of (cooperative) spatial diversity, which have been receiving a significant interest in various communities as a means for improving the performance of both infrastructure-based and ad-hoc-based transmission systems operating over multipath fading channels. In particular, in antenna sharing systems the mobile radios share their single-antennas to create a distributed virtual antenna array through distributed transmissions and distributed signal processing operations. Although cooperative wireless communications exhibit various design challenges and research opportunities at different protocol layers, in this contribution we mainly focus on physical layer issues. In particular, we propose a comprehensive and unified framework for performance analysis of multi-hop multi-branch wireless systems with channel state information (CSI-) assisted analog relays over generalized fading channels. The framework relies on the moment generating function (MGF-) approach for performance analysis of digital communication systems over fading channels and on some properties of the Laplace transform, which allow to develop a simple single-integral relation between the MGF of a random variable and the MGF of its inverse. Numerical and simulation results are also provided to substantiate the accuracy of the proposed framework.

We have recently proposed a general approach for approximating the power sum of log-normal random variables (RVs) by using the Pearson system of distributions, and then used it for performance analysis of Ultra Wide Band (UWB) wireless systems. Therein, we have also highlighted the main advantages of using the Pearson approximation instead of the usual Log-Normal one, and compared the proposed method with other approaches available in the open technical literature. However, despite being very accurate, the proposed method may be, in some circumstances, computational demanding since a non-linear least-squares problem needs to be solved numerically. Motivated by the above considerations, the aim of this paper is to provide an alternative approach for computing the parameters of the approximating Pearson Type IV distribution. The proposed solution is based on the method of moments (MoMs) in the logarithmic domain. In particular, the specific contribution of this paper is to provide closed-form expressions for the log- moments of the log-normal power sum. By using some known properties of the Laplace transform, we will show that the MGF of the log-normal power sum in the logarithmic domain (i.e., the log-MGF) can be obtained from the Mellin transform of the MGF of the Log-Normal power sum in the linear domain. From the estimated log-MGF, we will then compute the desired log-moments required for Pearson Type IV approximation. Numerical results will be also shown in order to substantiate the accuracy of the proposed method.

Recent advances in the technology of wireless electronic devices have made possible to build ad-hoc wireless sensor networks (WSNs) using inexpensive nodes consisting of low power processors, a modest amount of memory, and simple wireless transceivers. Over the last years, many novel applications have been envisaged for distributed WSNs in the area of monitoring, communication, and control. One of the key enabling and indispensable services in WSNs is localization (i.e., positioning), given that the availability of nodes' location may represent the fundamental support for various protocols (e.g., routing) and applications (e.g., habitat monitoring). In the depicted context, the present contribution reports our recent research advances along two main directions: i) first of all, we provide a comparative analysis of various optimization algorithms that can be used for atomic location estimation, which include: triangulation, steepest descent, non-linear least squares, conjugate gradient, and an enhanced version of the Steepest Descent (ESD) that is introduced in this paper, and ii) then, we provide a statistical characterization of location errors, by showing that the distribution of error positions can be well approximated by the family of Pearson distributions. In particular, we will show that i) the ESD algorithm may be competitive with the other algorithms in terms of estimation accuracy and numerical complexity, and ii) the knowledge of location error distribution may be efficiently used to speed-up the analysis of iterative-based positioning algorithms by avoiding the need of simulating the whole location discovery algorithm and allowing simulation at the atomic level only.

In this letter, we propose a framework for analyzing the performance of ultra wide band (UWB) receiver architectures in sparse multipath channels with overlapped multipath components (MPCs). The proposed methodology is based on approximating the moment generating function (MGF) of the received signal-to-noise ratio (SNR) via Pade expansion. The method can be applied to any fading scenarios and to any UWB receiver architectures, provided that the MGF of the SNR can be characterized in terms of a convergent Pade expansion. By comparing the results obtained from the analysis with those obtained from simulations in selected reference scenarios, it can be observed that the proposed approximation is very accurate.

This paper deals with the analysis of the timing acquisition (synchronization) process in Impulse Radio (IR-) Ultra Wide Band (UWB) systems based on Differential Transmitted Reference (DTR) receiver architectures. The fundamental contribution includes a theoretical framework for timing acquisition analysis, which is not only able to describe the first moment (Mean Acquisition Time, MAT), and the second moment (standard deviation of the acquisition time) of the acquisition process, but which also provides a consistent and comprehensive analysis of the probability mass function of the acquisition time, i.e., Acquisition Time Mass Probability. In particular, the specific novelty insights of this paper are as follows: (i) the proposal of a new synchronization algorithm, which is based on a two-step approach and relies on the specific characteristics and peculiarities of DTR receivers, as well as the analysis of its performance via a framework based on the theory of Markov processes; (ii) the exploitation of the LATTICE- POISSON algorithm to accurately estimate the Acquisition Time Mass Probability and Overall Acquisition Probability PD(ov), i.e., the probability to get synchronized before a given time; (iii) the performance analysis and comparison of one-step and two-step solutions with respect to the acquisition threshold; and (iv) the analysis of two approaches to estimate MAT and PD(ov)in multipath fading channels, i.e., "Tacq Average" and "Pd Average', which are shown to lead to different results in different scenarios. We observe that restricting the analysis to the MAT may lead to hasty conclusions about the effect of the acquisition threshold on the design of DTR receivers, thus substantiating the need for a more general analysis using PD(ov), as well as the necessity of specifying the characteristics of the wireless channel (e.g., quasi-static, slowly- or fast-fading) for an accurate performance analysis.

Approximating the sum of Log-Normal random variables (RVs) is a long-standing open issue, in the old and recent literature, and many approaches have been proposed to deal with that problem. However, all previous contributions are referred to model the "power sum" distribution, i.e. the weighted linear combination of Log-Normal RVs with weights that may take only positive values. In this paper, we extend that analysis by assuming that the weights may also take negative values. We also point out the importance that this scenario may have for the accurate analysis of ultra wide band (UWB) systems when intra-pulse interference due to multipath propagation cannot be neglected. In this perspective, (i) we show that the weighted linear combination of Log-Normal RVs can be well approximated by the Pearson Type IV distribution in the logarithmic domain, (ii) we use the obtained results for the accurate estimation of the average bit error probability (ABEP) of UWB receiver architectures.

In this paper, we propose an analytical framework for the accurate analysis of Rake and transmitted reference (TR) ultra wide band (UWB) receivers in multipath channels with log-normal fading. The framework relies on approximating the logarithm of the signal-to-noise ratio (SNR) at the detector input by the Pearson type IV distribution, which turns out to provide a simple but surprisingly effective and accurate approximation for the whole SNR probability density function (pdf). The framework includes the analytical derivation of i) the average bit error probability (ABEP) via Gauss-Legendre Gaussian quadrature rules (GQR), ii) the SNR cumulative distribution function (CDF) via the hypergeometric function2F1(middot, middot; middot; middot), which is useful for outage probability (Pout) analysis and iii) the SNR moment generating function (MGF) via Gauss-Legendre GQR. The validity and accuracy of the theoretical approach are also substantiated via Monte Carlo simulations.

Presents abstracts of forthcoming articles.

In this paper, a lognormal approximation is proposed for the sum of lognormal processes weighted by binary processes. The analytical approach moves from the method early proposed by Wilkinson for approximating first-order statistics of a sum of lognormal components, and extends to incorporate second-order statistics and the presence of both time-correlated random binary weights and cross-correlated lognormal components in moments' matching. Since the sum of weighted lognormal processes models the signal-to-interference-plus-noise ratio (SINR) of wireless systems, the method can be applied to evaluate in an effective and accurate way the outage occurrence rate and outage duration for different wireless systems of practical interest. In a frequency-reuse-based cellular system, the method is applied for various propagation scenarios, characterized by different shadowing correlation decay distances and correlations among shadowing components. A further case of relevant interest is related to power-controlled wideband wireless systems, where the random weights are binary random variables denoting the activity status of each interfering source. Finally, simulation results are used to confirm the validity of the analysis.

This paper deals with timing acquisition (synchronization) for ultra wide band (UWB) systems based on differential transmitted reference (DTR) receiver architectures. In particular, the paper represents an extension to multipath scenarios of our previous work [1] and aims at comparing the performance of two different search schemes (i.e. one- and two- step), by considering two verification mechanisms (i) returning false alarm and (ii) absorbing false alarm. The analysis of mean acquisition time (MAT) and overall detection (acquisition) probability (PDov) shows that the proposed two-step scheme allows to improve synchronization capabilities (i.e. faster acquisition) while guaranteeing the same bit error probability (BEP).

In this paper we propose a framework for analyzing synchronization performance of UWB systems based on differential receiver architectures. We introduce an extended signal flow graph representation based on the Markov chain theory, which is able to easily and efficiently include realistic Verification/False Alarm Recovery Systems and whose analysis has been typically simplified so far. The proposed model, which turns out to fall within the Markov chain theory with multiple terminating hypotheses and multiple absorbing states, is used to investigate the performance of one- and two-step search schemes with absorbing false alarm occurrences. The analysis of the Overall Detection (Acquisition) Probability shows that the two-step scheme can provide better acquisition probabilities with comparable synchronization accuracy.

An overview of some recent advances in distributed information processing for control over wireless sensor networks is presented in this paper. Firstly, a taxonomy of fundamental control and communication schemes for these systems is introduced. Next, specific research issues are proposed and discussed with three prominent examples on distributed source coding with packet aggregation, distributed cooperative diversity and distributed cooperative localization. In regard to these examples, it is argued about some open research problems and suggestions for further investigations on joint control and communication design for distributed processing and control over wireless sensor networks.

Moving from the need for a simple and versatile method for outage computation in various contexts of interest in wireless communications, in this paper we propose a lognormal approximation for the linear combination of a set of lognormal random variables (RV) with one-sided random weights. The approximation is based on a generalization of the well known moment matching approximation (MMA) for the sum of lognormal RVs, and it allows quite simple handling of the power sum of interfering signals even in rather complicated scenarios. Specifically, composite multiplicative channel models with unequal parameters can be handled, and generic (unequal) correlation patterns for some channel components can be handled with reference to any pair of signals. At this stage of the computation, only moments of the random weights are required. The probability density function of the random weight for the useful signal component may be required in computing outage probability, and numerical methods may be only required to solve a single integral at this second stage. The suitability of the approximation is examined by evaluating outage performance for various values of system parameters in the context of interest of composite Nakagami-lognormal channels in reuse-based systems

In this paper we propose a polyphase processing solution for relaxing the strict timing constraints of all-digital ultra wide band (UWB) receiver architectures. The work is motivated by the fact that, while interleaved data acquisition systems have been investigated in the literature with the aim of mitigating the strict timing requirements imposed by the sampling theorem, less attention has been paid in analyzing efficient processing architectures aiming at reducing the overall computational complexity of UWB receiver architectures. Specifically, we evidence how to exploit the polyphase approach for designing efficient detection, synchronization and channel estimation structures

This paper proposes a general framework for analyzing the performance of ultra wide band (UWB) communication systems in a synchronous reference scenario. In this context the information flows, produced by various sources, are synchronously multiplexed to share the common radio resource. The analysis in mainly devoted to investigate the performance of differential UWB receiver architectures, with the signal plus (multiplexing) interference to noise ratio (SINR) and bit error rate (BER) being the parameters of interest. While the obtained results point out that typical channelization codes (i.e. Hadamard) do not seem to be adequate to mitigate multiplexing interference (MI), we identified exact expressions to completely remove MI. In this perspective, the developed framework turns out to be a fundamental setup to identify efficient code families that aims at optimizing the overall system performance

A decentralized communication and control system is presented for driving assistance and automation along designated highway segments. This paper is based on a hybrid dynamical model describing vehicular motion, and the structure of a safe controller is presented. A ranging and communication system provides information for a vehicle and its nearest neighbors. The system is capable of handling sudden changes of regime, overtakes, reentries, as well as a number of maneuvers dictated by safety requirements under partially unpredicted events. A user-friendly interface, based on a palmtop computer, is developed to assist drivers visually and acoustically.

Moving from the need for a simple and versatile method for outage computation in various contexts of interest in wireless communications, in this paper we propose a lognormal approximation for the linear combination of a set of lognormal random variables (RV) with one-sided random weights. The approximation is based on a generalization of the well known moment matching approximation (MMA) for the sum of lognormal RVs, and it allows quite simple handling of the power sum of interfering signals even in rather complicated scenarios. Specifically, composite multiplicative channel models with unequal parameters can be handled, and generic (unequal) correlation patterns for some channel components can be handled with reference to any pair of signals. At this stage of the computation, only moments of the random weights are required. The probability density function of the random weight for the useful signal component may be required in computing outage probability, and numerical methods may be only required to solve a single integral at this second stage. The suitability of the approximation is examined by evaluating outage performance for various values of system parameters in some contexts of interest, namely spread spectrum systems and typical reuse-based systems with composite Rayleigh-lognormal and Nakagami-lognormal channels.

This paper proposes an investigation of binary and quaternary modulation schemes for ultra wide band systems using differential receiver architectures. The expressions for the signal to noise ratio (SNR) and bit error rate (BER) are derived taking into account the code effect, the trade-off between time correlation window width and front-end filter bandwidth. The analysis points out that the quaternary modulation scheme outperforms binary modulations in terms of BER.

SERAN is a two-layer (routing and MAC) protocol for wireless sensor networks in manufacturing plants. At both layers, SERAN combines a randomized and a deterministic approach. While the randomized component provides robustness over unreliable channels, the deterministic component avoids an explosion of packet collisions and allows our protocol to scale with network size. Our solution is based on a mathematical model that characterizes performance accurately without extensive simulations. SERAN is robust against node failures and clock drifts, supports data aggregation algorithms and is easily implementable in any of the existing hardware platforms. Although SERAN was designed for manufacturing plants applications, it can be used in any type of clustered topology. We consider a representative case study and we present simulation results to show SERAN efficiency

This paper proposes a log-normal approximation for the sum of on-off log-normal processes. An analytical approach is developed, that moves from the method early proposed by Wilkinson for approximating first order statistics of a sum of log-normal components, and extends to incorporate second order statistics and the presence of random weights in moments' matching. As a relevant application, the method is used to calculate in an effective and accurate way the parameters of the signal-to-(noise+interference) ratio (S I N R) in a power-controlled wideband wireless system, where the random weights are binary RVs and denote the activity status of each interfering source. A collection of numerical results is presented, where performance predicted by the analysis is compared to that obtained from simulation.

An analytical approach to derive the level crossing rate (LCR) and the average fade duration (AFD) for the signal-to-interference ratio (SIR) in a mobile radio system is proposed. The channel model is characterized by a log-normal shadowing component and a Rayleigh fast fading component on the useful link and on interfering links. Shadowing components are assumed to be cross-correlated. The approach can be divided in two steps. The first one mainly consists in extending Wilkinson's approximation method for the sum of log-normal random variables to the matching of second order statistics of randomly weighted log-normal processes. In particular, the latter approach is used in order to obtain a log-normal approximation for the ratio between total interference and the log-normal component of the useful signal strength. In the second step the SIR is expressed as the product of a Rayleigh process and a log-normal process, and the LCR and AFD are then obtained through the Rice's (1944) approach. Numerical results are presented in terms of LCR and AFD for various values of cross correlation parameters among shadowing components.

A novel methodology is proposed for computing the outage probability in mobile radio systems in the presence of log-normal shadowing. A relevant feature is that the proposed analysis assumes a general correlation for any pair of links. Various approaches are considered to compute the statistics of user signal-to-interference ratio (SIR), namely Schwartz and Yeh's method, Wilkinson's method, and Fenton's method. By a simple reformulation of the problem, these methods can be used to calculate in a straightforward way the parameters of the SIR. The accuracy of the methods is checked in a number of situations of interest. Moreover, when the same correlation is assigned to any pair of links, the novel analysis is more accurate than previously proposed approaches.

In this paper, the problem of computing cochannel interference statistics in signal strength measurements in mobile radio systems is presented. In a cellular environment with cross-correlated log-normal shadowings, extensions of Wilkinson's method and Schwartz and Yeh's (1982) method are proposed for evaluating the statistics of differences between signal strengths that a mobile terminal measures on the links to any pair of base stations in the presence of cochannel interferers. The derived statistics are then used in the performance analysis of relative signal strength handover algorithms. Results provided by the two methods are compared with simulation results, in order to assess their accuracy, and computational issues are addressed. From numerical results, it is also seen that handover algorithm performance has a noticeable dependence on both cross correlation among shadow fadings and the interference level. Finally, it is seen that previous approaches to derive cochannel interference statistics in the presence of log-normal shadowing can be obtained as particular cases.

The problem of allocating efficiently the power to the various classes of users in a multimedia CDMA wireless system is considered in the presence of imperfect power control. The quality of service requirement for each class of users is expressed in terms of the outage probability. It is seen that the reverse link capacity is maximized by a proper power sharing policy, which results to be a generalization of the one previously found in the presence of perfect power control.

In a multimedia CDMA wireless system, where various classes of users are characterized by different quality of service requirements and source rates, the capacity bound is derived. In a multi-cell environment, an approach is proposed to exploit the optimal policy of jointly assigning the power level and the base station to each user terminal. Non-uniform distributions of users can thus be accounted for in a straightforward way.

A general model for the analysis of outage intervals in mobile radio systems with macrodiversity is proposed. In a log-normal shadowing environment, reception diversity from two base stations is considered in the general case of different fading margins. Through a level-crossing analysis, the probability density function (PDF) of the outage interval is derived. It is seen that exact expressions can be obtained for the average outage occurrence rate and the average outage duration. The exact expressions are used to also improve the accuracy of the PDF at small values of the fading margins, by forcing the PDF to meet the exact average through a proper choice of its parameters. As a particular case, explicit solutions are derived for minimum duration outages.

The traffic performance of integrated cellular mobile and satellite networks is analyzed. Using a previously proposed traffic model for a hierarchical architecture, a parametric analysis is carried out in the ranges of interest for application scenarios of satellite systems under development (e.g. Iridium and Globalstar). In particular, the effect of the following parameters is considered for some constellations: (a) the ratio between the highest and the lowest value of the spatial traffic density in the area covered by a satellite spot; and (b) the percentage of the satellite spot area covered also by the underlying terrestrial cellular networks. A traffic capacity estimation is carried out for the generic satellite spot, using channel reservation (guard channels) for those users who directly access the satellite. Moreover, an improved traffic model is presented, which accounts for frequent inter-spot handovers in low Earth orbit satellite systems.

A performance analysis of packet cellular networks in the presence of shadowing is presented. Starting from the theories of level crossing and large excursions of Gaussian processes, a statistical characterization of occurrence and duration of fading intervals is first obtained. Then, by considering also the statistics of activity-inactivity intervals of the mobile terminal, the probability function of the sequences of dropped packets is derived. Results are presented in terms of fading intervals statistics and probability function of dropped packet sequences for voice sources, in the presence and in the absence of a terminal buffer. A radio link design approach is also proposed and a design example is discussed.