In the context of 6G next generation networks, the Internet of vehicles (IoV) paradigm will be supported by overlapping network layers, like the aerial and space ones, to guarantee enhanced performance and 3D connectivity. Specifically, the integration of aerial devices, such as unmanned aerial vehicles (UAVs), into IoV is expected to enhance network performance, especially for vehicular safety applications, where packet delivery requires low latency and reduced connectivity loss, as compared to existing communication modes. In this paper, the technique ALI, an aggregate LiDAR images-based approach for road safety applications in a 6G context is introduced. It considers multiple LiDAR images that are shared and collected among vehicles to improve the accuracy in vulnerable road users detection. As compared to a single LiDAR image, ALI approach shows an enhanced detection accuracy, as well as allows alert message forwarding to other approaching vehicles in case of obstacle detection, via multiple interface cards and transmission modes. Results show that the adoption of UAVs as communication nodes allows to extend the coverage between 80 m and 130 m for an outage probability of 1%, overcoming vehicle-to-vehicle and vehicle-to-network communication modes and to provide a communication latency lower than 30 ms achieved up to 150 m.

Recently, pushed by the COVID-19 pandemic, the need of respecting social distancing has motivated several researchers to define novel technological solutions to monitor and track user movements. Information and Communications Technologies (ICT) world has addressed this challenge by means of the use of different technologies, such as Bluetooth, in order to track user interdistance and encounter time. Technology solutions should be able to not only track contacts, but also alert users to restore social distancing. In this article, we present IMPERSONAL framework, with the twofold aim of both: 1) tracking and monitoring social distancing and 2) alerting users in case of gatherings. The framework is based on a subnetwork of computer vision-based devices that are adopted to monitor and track users’ movements to estimate their interdistance and compute the encounter time. Such information is then the input to an Internet of Things subnetwork, aiming to retrieve the anonymous IDs of people belonging to a gathering, as well as to send alert messages to them. We assess IMPERSONAL framework by means of extensive Monte Carlo simulations and experimental results, showing its effectiveness in terms of accuracy in correctly identifying users and gatherings in videos taken from live cameras, both in case of indoor and outdoor real scenarios. The benefits of the IMPERSONAL framework are expressed in terms of the ability to track people, solve gatherings, and send warning messages.

Reconfigurable Intelligent Meta-surfaces (RIMs) are particular devices able to control and manipulate radio frequency wireless signals. This promising technology allows to improve the reliability of wireless networks, thanks to the capacity of reflecting the desired signals through appropriate phase shifts. The joint use of RIMs and Computer Vision (CV) technology is the main objective of this paper. This synergistic approach is used to correctly identify the specific configuration of a radiation pattern, to be used as input for computing optimal coding sequences of the RIM. Indeed, by the means of a CV algorithm it is possible to infer a connectivity graph related to a real scenario, where people is moving. The information about network nodes such as their distance, the relative position, etc. is used for feeding an intelligent logic, able to compute the optimal configuration for re-directing the signals towards a given receiver target node.Numerical results show the huge potentiality of this combined approach in terms of interference reduction. It has been observed that for high traffic load, it is possible to reduce the average interference in the network of 40%. Furthermore, an analysis including the positioning estimation error of the CV algorithm has been addressed, in order to consider how it affects the interference reduction. Results show that, even though there is an increasing effect of interference, when the error is accounted, the interference reduction impact is still important.

The European Train Control System (ETCS) relies today on the 2nd generation cellular system GSM-R. GSM-R obsolescence has triggered the evolution of the current European Railway Traffic Management System (ERTMS) to the Future Railway Mobile Communication System (FRMCS), under development. FRMCS considers the use of several radio access technologies in parallel such as Wi-Fi, LTE, Satellite and 5G. Testing new communication systems along railway tracks is time and money consuming. Consequently, it is important to develop a zero-on-site-testing approach thanks to the development of emulation platforms. These platforms, combining hardware and software, are able to reproduce in laboratory real railway infrastructure behavior and scenarios. This paper presents the EMULRADIO4RAIL platforms, developed in the framework of Shift2Rail program and gives examples of results obtained.

Typical mountain Search and Rescue (SaR) operations require the localization of the persons involved in accidents in harsh environments. ARVA and RECCO are the current standards for the localization in snowy environments although their radio range is limited to some tens of meters. In this article, we prove by experimental results that the long-range (LoRa) low-power wide-area network (LPWAN) technology is very promising for SaR applications due to its extended radio range. A LoRa-based system for SaR operations is presented and analyzed. The localization of the persons is obtained through an algorithm based on path-loss (PL) measurements. Radio PL models of body-worn LoRa devices in harsh mountain environments are derived by measurements. We observed that although the communication range of LoRa decreases from kilometers to hundreds of meters in the tested environments, at least 50% of the transmitted packets can be received at distances about five times greater than those achievable with golden standard technologies such as ARVA. The performances of the considered localization algorithm are analyzed on the basis of the collected data. The achievable accuracy is in the order of meters around the true position for a relatively large number of available PL measurements. Finally, we propose and detail a LoRa-based system for SaR operations.

A Normal approximation for the downstream bit rate per user in modern Fiber-to-the-Cabinet DSL-based access systems such as Very high-speed Digital Subscriber Line type 2 (VDSL2) and Long Reach VDSL (LR-VDSL) is presented in this paper. It accounts for the positions of subscribers along the main cable from the Cabinet, for the Far-end cross-talk (FEXT) fluctuations, for the transmitter power spectra of subscribers and for zero forcing vectoring. A stochastic model relating the FEXT to residual FEXT after zero forcing vectoring pre-coding is also presented. The proposed Normal model is derived by assuming Log-normal statistics of the signal-to-interference plus noise ratio per sub-carrier. Its validity is assessed by computer calculation by superimposing the cumulative distribution functions obtained from exact bit rate calculation with those obtained with the Normal model. Differences of few Mbit/s have been observed for high percentiles thus proving the effectiveness of the proposed model. We applied the model to assess coexistence among different DSL technologies such as VDSL2 and LR-VDSL sharing the same copper cable from the Cabinet and even to evaluate the downstream bit rate for G.fast with zero forcing vectoring.

Smart city services are enabled by a massive use of Internet of Things (IoT) technologies. The huge amount of sensors, and terminals with a great variety of typologies and applications, requires a secure way to manage them. Capillary networks can be seen as a short range extension of conventional access network in order to efficiently capture the IoT traffic, and are enablers for smart city services. They can include both IP and non-IP devices, and security can become an issue, especially when simple unidirectional communication devices are considered. The main goal of this paper is to analyze security aspects in IoT capillary networks including unidirectional and bidirectional IP or non-IP devices. We propose an algorithm for secure access for uni- and bi-directional devices. The security procedure is based on a secure key renewal (without any exchange in air), considering a local clock time and a time interval of key validity. Following previous work in 2014 by Giuliano et al., in this paper we assess the duration of the validity of the time window, and present extended simulation results in terms of (average) transmission time in a realistic scenario, i.e., including the presence of disturber(s), then providing indications for the setting of the duration of the key validity time window. Finally, we present the benchmark analysis in order to assess the effectiveness of our approach with respect to other existing standards, as well as the security analysis in terms of typical attacks.

A performance analysis of VDSL2 technologies in FttC or FttC/FttDp hybrid scenarios requires knowledge of the access network geometry, propagation, and crosstalk interference models. A simulation-based approach is commonly adopted for performance assessment. In this paper, we introduce a performance evaluation framework based on the log-normal approximation for the probabilistic description of the signal-to-interference plus noise ratio (SINR), which is then used to obtain the statistics of the achievable bit rate per user. A very good agreement has been observed between the exact and the approximated calculations of the bit rate up to 600 m from the Cabinet. In addition, the log-normal approximation has allowed to define a simple procedure, based on the equivalent number of co-located interferers, to evaluate the bit rate per user for generic access network geometry. Furthermore, two approximated formulas for bit rate have been obtained under high SINR and dominant far-end crosstalk (FEXT) conditions. They evidence the logarithmic decrease of the bit rate with the distance from the Cabinet and provide the accurate results for distances up to 400 m. Finally, when FEXT fluctuations are modeled in accordance with Beta distribution, we have observed the log-normal approximation still provides valid probabilistic description of the SINR.

To provide advanced services to citizens, Smart City services are enabled by a massive use of Internet of Things (IoT) technologies. The envisaged huge amount of sensors, and terminals with a great variety of typologies and applications, do not allow having a unique way to manage them, requiring for example minimal packaging and presentation overhead for many of them. In general in a network providing Smart City services, both IP and non-IP devices are present. In this paper, we tackle the security issue for non-IP devices able to connect by a short-range with a mediator gateway, forming a capillary access network, which can be seen as a short range extension of conventional access network in order to efficiently capture the IoT traffic. In particular, we propose security algorithms both for uni- and bi-directional terminals, depending on the terminal capabilities. The security algorithms are based on a local key renewal (without any exchange in air), performed just considering the local clock time. Performance are obtained respect to the maximum number of terminals that can be managed by one mediator gateway and the maximum packet delay as a function of the number of terminals in the area.

Adjacent channel interference (ACI) between OFDM signals severely impacts system performance and spectrum efficiency. To eliminate ACI, Active Interference Cancelation (AIC) techniques using additional modulated OFDM sub-carriers can be adopted. This paper describes an AIC technique based on multi-step calculation of clipped canceling symbols. The algorithm has simple implementation and allows to easily control the extra power required for canceling symbols. To avoid bandwidth expansion, non-orthogonal canceling sub-carriers (E-AIC) can be easily incorporated in the procedure. The achievable reduction of the OFDM spectrum tail power has been evaluated analytically and by simulation.

Telecommunications are strategic for train control system operations. The European ERTMS/ETCS system for high speed trains control utilizes dedicated GSM-R mobile network(s). The costs for deployment and maintenance of GSM-R network are not sustainable for the extension of train control to low/medium traffic lines. This paper investigates on the possibility of replacing dedicated mobile radio infrastructures with the radio network integrating one (or more) existing PLMNs and satellite as backup. A methodology for performance assessment is presented and applied to the study of network availability and operational costs. Availability can be improved by allowing train to intelligently select the public network(s) time by time. Operational costs are dictated by the satellite component which may become essential in rural areas. Looking at the European scenario, a discussion on the extension of the Euroradio protocol to operate over multi-bearer mobile network is also presented.

Cellular mobile radio networks are expected to increase the energy requirements due to their massive deployment. Then, it is required to improve their energy efficiency in order to favor the eco-sustainability and not to obstacle their economic impact. In this paper we study the impact of the power consumption in the design of mobile networks. The evaluation has been performed for GSM and LTE systems. The main aim is the analytical evaluation of the optimal cell radius accounting for the network sustainability and for both coverage and traffic constraints. Overall power consumption is expressed as the sum of static and dynamic terms. The former is due to BSs switch on and signaling, the latter is function of the traffic in the cell. The beneficial effects of power control on energy consumption are evaluated and compared with the non-power controlled case. Finally, reduction in power consumption for LTE respect to GSM is analyzed.

ICT technologies provides non-invasive and low cost solutions to improve safety and security in public transport vehicles for persons and freights. In this paper we consider an intelligent heterogeneous sensor network installed on the vehicle to monitor its status. The network can be remotely interrogated by operators in the command and control centre (C&C) that, in turn, can be automatically notified by the same network when a critical condition is assessed. To reduce the signaling overload on the mobile network connecting vehicles to the C&C, an intelligent on-board controller analyzes data from sensors, infers on the vehicle status and reacts properly. In accordance to the severity of the event, it decides whether the situation can be resolved at local level or if it is necessary to alert the C&C. This strategy permits to significantly reduce the amount of information sent over the public radio network. We express the performance of the considered solution in terms of the blocking probability due to (unavoidable) false alarms generated by vehicles as a function of the false alarm rate characterizing the on-board network. Results are used to assess the maximum tolerated false alarm rate guaranteeing a desired level of blocking probability for a given number of mobile radio channels.

Recently, wireless indoor location systems have been successfully used in many applications, such as asset tracking, indoor navigation, and inventory management. Such systems become essential in Public Safety and Disaster Relief (PSDR) scenarios, where a robust and reliable first responder positioning system can significantly increase safety in emergency operations. In this paper, we characterize the performance of a RFID-based indoor localization system. We present various tests aimed at assessing the capability of the ILS to identify first responders in different conditions. Results show that, by means of a correct dimensioning of the ILS, high efficiency can be achieved in localization.

The increasing demand of indoor broadband access encourages the diffusion of the "home base stations", known as femtocells. Their self installation nature envisages interference problems due to a possible overload of local femtocell installations in the same area. To reduce the interference among femtocells we propose and analyze the performance of a dynamic frequency selection strategy, according to which each femtocell is able to select one of the possible frequencies available from all the operators in order to experience the best Signal-to-Interference Ratio (SIR). We assume that mobile operators share their requency bands allowing femtocells subscribed to a certain operator to exploit the frequency resources of other operators. In this paper we evaluate the performance in terms of allowed number of active femtocells per operator when the channels available from operators increase. It is observed that the application of the proposed Dynamic Frequency Selection (DFS) algorithm with band sharing allows single operator to significantly improve the number of active femtocells deployed in the area with respect to the non band sharing case, i.e. a Spectrum Sharing Gain is achieved.

The self-installation nature of femtocells sharing the same frequency band can lead to harmful femto-to-femto interference levels. The possibility for operators to share its licensed spectrum allows femtocells of one operator to exploit the frequency resources of other operators. In this paper we propose and analyze the performance of two dynamic frequency selection algorithms that permit to the generic femtocell the smart selection of its operating band, among those available from every operator, starting from the measurements of local interference. The performance of the proposed techniques are analyzed by simulation in terms of outage probability and the achievable Signal-to-Interference Ratio (SIR). It is observed that, in a multi-operator scenario this approach offers significant improvement in terms of achievable network capacity and quality of service to customers.

By Ibrahim Habib and Franco Mazzenga, Guest Editors Wireless communications for public safety, emergency communications, and delivery of wideband services to rural communities are topics of crucial importance to the welfare of the society. Broadband wireless digital subscriber loop (WDSL) technologies offer complementary and possibly low cost solutions to providing broadband connectivity services even to low densely populated areas that otherwise would be outside the loop. At the same time the availability of broadband wireless technologies can be useful for effective information dissemination in times of natural and man-made disasters thus providing a fundamental tool helping public safety agencies in providing quick response and support to communities needing urgent assistance and relief. The topic has been largely investigated (e.g. see references 1-6 and references therein) during the last two decades. The quality of communications services offered by the actual public safety systems is in general well behind of that offered by commercial systems. At the same time, due to costs of radio coverage and trunking, the quality of services provided by existing commercial mobile systems in low densely populated areas, e.g. rural areas, is well below that offered by operators in urban and sub-urban areas. Current solutions for rural areas for example provide basic telephone services and only are rarely suitable for effective data access. Some rural areas that are close to natural woods with dry climates are prone to fires that could be disastrous. Reliable emergency communications systems should be adequately available with access to the residents in order for emergency authorities to be able to respond to such natural disasters, as quickly as possible, if they occur. The society obvious need for new and advanced communications services for supporting public safety operations has led to the evolution of current systems towards a new generation of professional mobile radio (PMR) and standard communication systems. Terrestrial Trunked Radio (TETRA) technology has gained wide acceptance (especially in Europe) and is considered one of the mature technologies for PMR and even for PAMR (Public Access Mobile Radio) markets. TETRA has been conceived in accordance to the requirements issued by public safety agencies such as ambulance services, law enforcement, civil emergency management/disaster recovery, fire services, coast guard services, search, and rescue services, government administrations and so forth. In recent years it has been observed that integration between mobile broadband technologies and TETRA can be helpful for the achievement of the advanced services envisioned for the next generation of Public Safety and Disaster Recovery (PSDR) communication systems. In fact, data rates required for advanced emergency services provisioning plus the demand for enhanced mobility improved ad hoc functionality, and international interoperability reach far beyond the scope of the current PSDR narrowband telecommunication systems and call for mobile broadband enhancements. A significant challenge faced by professionals conducting public protection and disaster relief operations is the problem of incompatible communications systems. The goal of the MESA project established between the ETSI and the TIA (www.projectmesa.org) 7 was to develop advanced mobile broadband technical specifications that could solve interoperability issues among different communication technologies and to define enhanced functionalities of the public safety communication (PSC) systems. One task of this special issue is to address the integration of current PMR systems with 3G and 4G technologies for providing enhanced communication services including real time access to (local) sensor networks (if any) as well as to databases for retrieving and distributing audio, video, and geographical information. This could be important during an emergency operation where a large amount of contextual information is generated and need to be distributed wirelessly to personnel from different emergency agencies 8, 9. In parallel, on the commercial side for civilian applications, access to broadband communication services has become an established, global commodity required by a large percentage of the population. It is widely recognized in developed countries that the setting up broadband wireless access networks is helpful to solve the “digital divide” gap. Efforts to bringing mass-market broadband services even to low densely populated areas such as the rural ones follow the initiative of the European Commission called Bridging the broadband gap which is intended to carry high-speed broadband internet to all Europeans and in particular to EU's less-developed areas. WDSL systems, even supporting mobile and nomadic users, that are based on the Worldwide Interoperability for Microwave Access (WIMAX) and other technologies such as the Rural WCDMA (which is an effective solution to rapidly extend UMTS to rural areas) can play a significant role in the broadband wireless access market. Furthermore it should be observed that rural broadband access is not limited to Europe but it represents a common global challenge. The R-WCDMA and WiMAX technologies seem to be promising solutions for the provisioning of broadband services to rural areas. They can easily incorporate all the technical solutions to improve the link budgets and, very importantly, allow the re-use of already existing wireless terminals (at least for R-WCDMA). In general, it is well known that networks for rural coverage could be constructed from the integration of more than one communication technologies such as satellite, terrestrial and high altitude platforms (HAPs) (if any). In this case, techniques for the intelligent use of the available radio technologies could help reducing deployment costs and improving spectrum usage. Alternatives for broadband access could be based on structured terrestrial networks adopting (possibly cheap) techniques for enlarging the cell coverage area of a single base station deployed for offering point-to-multipoint (PMP) services. These solutions include relay stations and/or distributed (sub)-networks organized in a mesh or ad-hoc that are connected to the base station which, in turn, provides access to the core network. This special issue includes a number of interesting papers covering different aspects of emergency and rural communications systems. Some of the topics discussed in this special issue include: hybrid network architectures comprising satellite and HAPS for covering rural areas as well as for supporting emergency situations; integration of heterogeneous communication networks; protocols for ad-hoc, mesh, and VANET networks. The problems of information dissemination during emergency and localization are also analyzed. Finally, we would like to thank the authors who presented their work, the reviewers for their meticulous reviews, and the editor-in-chief and the editorial staff of the Journal for their excellent efforts and support producing this special issue. Ibrahim Habib received the Ph.D. degree from the City University of New York, the M.Sc. degree from Polytechnic University of New York, USA, and the B.Sc. degree from Ain Shams University, Cairo, Egypt all in Electrical Engineering. In 1991 he joined the Faculty of the City University of New York where is now a Full Professor. His research interests span different areas of traffic engineering in IP, wireless, and optical networking. He has published more than 100 papers and reports in those areas. From 1998 till 2000 he was with AT&T Labs, and from 2000 till 2001 with Telcordia Technologies, Applied Research Department working on the architecture design of IP over optical networks, optical control plane and Operations Support Systems (OSS). He was a Guest Editor of the IEEE Journal on Selected Areas in Communications (JSAC), the IEEE Communications Magazine and was an Editor of the same Magazine. He was chair of many technical sessions, symposia and conferences. He is listed in many Marquis's who is who in the World and who is who in America editions. Franco Mazzenga received the Dr. Ing. degree in electronics engineering cum laude from the University of Rome Tor Vergata, Italy in 1993. From 1993 to 1994 he was with Fondazione Ugo Bordoni making research on the propagation at millimeter waves. In 1997 he obtained the Ph.D. degree in telecommunications from the University of Rome Tor Vergata. From 1998 to 2000 he was a researcher in Consorzio di Ricerca in Telecomunicazioni (CoRiTel). From 2000 to 2006 he was a researcher in the Electronic Engineering Department of the University of Rome Tor Vergata. Currently he is an associate professor of communications in the same department. Since 2001 he is the technical director of the Consorzio Università Industria Laboratori di Radiocomunicazioni (Radiolabs - http://www.radiolabs.it). He is the author and co-author of more than 90 scientific papers that have been presented on congresses or published on national and international journals. He is co-author of a book on Radar systems (in Italian) and co-author of four patents on communication technologies and applications. His research interests are on wireless access systems and networks and related technologies, GNSS systems and complex network theory applied to communication systems.

Femto-cell can be considered as a home base station (BS) that can be installed to improve bandwidth availability and coverage for enabling new applications in the home. Actual 3G-based femto BSs are seen as an alternative to Wi-Fi hotspots and/or as a complementary technology. In the very near future 3G and 4G cellular networks will converge on OFDM/OFDMA wireless access interface. Thus the planning and the performance evaluation of OFDM/OFDMA cellular system including femto cells is of interest.

Detect and avoid (DAA) procedures aim at improving ultra-wideband (UWB) coexistence with existing narrowband/wideband licenced/unlicenced victim terminals operating in the same band at the same time and area. The authors propose a DAA procedure that can be used to reduce the percentage of time the UWB interferes with victims operating in a time division duplexing (TDD) mode. The authors consider a system scenario where a TDD terminal has a primary role and UWB devices create a secondary network on a local area basis. A DAA procedure is implemented only in the UWB devices that adapt their transmissions in order to avoid or reduce interference on primary device(s) in the same area. The performance of the proposed DAA procedure is presented and discussed and its dependence on some key UWB transmission parameters, bit rate and the emitted power is evidenced. It is shown that the DAA timeout parameters can be tuned so as to arbitrarily reduce the average percentage of time the UWB interferes with the considered victim systems even well below the limits imposed by regulatory bodies. It is shown that interference reduction is obtained at the expense of reduced performance of the UWB transmission. The proper selection of DAA timeouts for a desired percentage of UWB interference and UWB link efficiency is discussed.

Classical single carrier cell planning is extended to multi-carrier systems operating over frequency selective channels. Extension is achieved by expressing the link outage probability in terms of the statistics of the effective SINR. Two approximations for the link outage probability are obtained by considering log-normal and Gaussian assumptions for the derivation of the statistics of the exponential effective SINR. A simplified planning procedure is presented and applied to the calculation of the network parameters for the typical two cells interference scenario. Results having accuracy within one dB are obtained for a number of sub-carriers greater than six and for an outage target of 5%.

Planning procedures for multi-carrier wireless systems based on the SINR evaluated over one sub-carrier do not allow to account for multi-carrier transmissions features where coded bits in the same block are spread over different sub-carriers. Due to channel frequency selectivity, sub-carriers can be subjected to different propagation conditions. The decoder in the receiver can compensate for errors even when some sub-carriers are received below the SINR target level. This fact should be accounted for during cell planning so to avoid wrong dimensioning of network parameters. In order to extend the classical planning approach to the multi-carrier systems we adopt the effective exponential SINR parameter for planning. The proposed procedure is general and it is based on the simulated statistics of the effective SINR. For evaluation purposes the two cell interference scenario is considered and the variability of the reuse distance with respect to the number of transmitted sub-carriers per block is investigated.

Wireless metropolitan area networks (WMANs) based on IEEE 802.16 standard are widely deployed to provide users with wireless network connectivity, anytime, anyplace. In particular IEEE 802.16 standard has been developed to provide fixed and mobile broadband applications at lower costs for installation as compared with traditional wired infrastructures. In this paper we present the main results of a measurement campaign on propagation at 3.5 GHz conducted by BT Italy and Ericsson with the University of Rome Tor Vergata. Path loss channel model obtained from experimental data are also presented.

Detect and avoid procedures (DAA) improve Ultra-wideband (UWB) coexistence with existing narrowband/wideband victim systems operating in the same band, at the same time and area. In this paper we propose a DAA procedure that can be used to reduce the percentage of time the UWB interferes the victim devices which operate in accordance to a frequency division duplex (FDD) mode. A cooperative scenario is considered. Some UWB devices are integrated with the victim devices and can broadcast information on the status of the victim to other UWBs in the area. This information is used in the DAA to improve performance. The performance of the proposed DAA procedure are presented and discussed and their dependence on some key UWB transmission parameters, such as the bit rate and emitted power, are evidenced. It is shown that the DAA parameters can be selected so to arbitrarily reduce the average percentage of time the UWB interferes with the considered victim systems.

In this paper we evaluate the impact of UWB transmissions on the performances of a WiMAX receiver, which employs orthogonal frequency-division multiplexing (OFDM) modulation and operates in a time division duplex (TDD) mode. To this aim, we compute the interference contribution caused by DS-UWB signals at the WiMAX receiver output, as well as the interference statistics, adopting a theoretical approach and simulations. We present a non-cooperative detect and avoid (DAA) procedure to mitigate the UWB interference to WiMAX. The results of the interference analysis are exploited to opportunely set the UWB transmission parameters in the DAA procedure, so that the targeted QoS is achieved for the WiMAX communications1.

Ultra-wideband (UWB) wireless technology is envisaged to play a key role in B3G wireless systems, guaranteeing very high bit rates, low power consumption, low costs and location capabilities. The availability of low cost and efficient devices makes UWB technology very competitive on the communications market. However, its worldwide acceptance mainly relies on coexistence issues because of the necessity of sharing the spectrum with other radio systems. The reduction, due to coexistence constraints, in the capacity of an UWB system in a realistic multipath channel is investigated. Link performance of an UWB system that exploits either partial or selective Rake combining at the receiver is evaluated over experimental impulse responses of an UWB indoor channel in an office building. Using these results, system performances are evaluated through a semi-analytical procedure in terms of outage probability and system capacity. Results on system capacity account for the limitations imposed by the current regulation, leading us to introduce the concept of ‘UWB systems limited by coexistence’.

The capacity of UWB enabled wireless personal area networks is analyzed in a dense multipath environment. The performances of UWB systems employing a direct-sequence multiple access scheme are evaluated in terms of link outage probability and average aggregate network throughput, considering a network topology based on a clustered structure, formed by a multitude of uncoordinated coexisting piconets. We study the dependence of the system performances on some critical design choices, such as the Rake receiver scheme, the mono-pulse characteristics of the transmitted UWB signals, the structure of the piconet frame, the traffic characteristics. Results are obtained by applying a semi-analytical estimate procedure, which accounts of the large and small scale fading phenomena for the UWB indoor propagation channel

OFDMA/OFDM multiple access/multiplexing techniques represent the radio interface technologies for the 4-th generation broadband cellular access networks such as the WiMAX operating the point-to-multipoint configuration. In this paper we consider the problem of the frequency reuse in cellular OFDMA/OFDM systems and in particular we calculate the reuse distance which is required to obtain a given link outage probability level. Analysis is carried out using a semi-analytical approach based on a general expression of the SINR accounting for multipath, frequency and time offsets between the reference terminal and the interfering devices. The proposed approach can be easily applied to evaluate performance under different operating modes of the OFDMA/OFDM cellular network e.g. synchronous BSs or not

Ultra-wideband (UWB) wireless technology will play a key role in the future beyond third generation wireless systems guaranteeing very high bit rates availability, low power consumption, low costs and location capabilities. The worldwide acceptance of UWB technology is mainly related to coexistence issues with other existing narrowband and wideband systems sharing the spectrum with UWB. To this aim regulatory bodies imposed restrictions on UWB transmissions so implicitly limiting its system capacity intended as the number of users that can be served for a specified link outage probability. In this work the problem of calculation. of UWB system capacity subject to power and coexistence constraints is analyzed. The problem is first formulated and a semi-analytical method for solving it is presented. The proposed procedure is then applied to a study case considering the coexistence between an UWB network located inside a building and outdoor fixed wireless systems. It is observed that power and coexistence constraints can lead to a significant under-utilization of the available UWB system capacity. The capacity-coexistence tradeoff is also discussed. In general, it can be observed that depending on the relative position between the UWB devices and the victim receiver, coexistence requirements may result to be more restrictive than power limitations and the UWB system can be limited by coexistence rather than by self-interference.

The performance of an Aloha multi-hop sensor network based on Ultrawideband (UWB) devices is evaluated in terms of the average link outage probability and the aggregate network throughput for different coverage radius of the UWB sensor. The sensor network architecture is based on the creation of multi-hop routes using intermediate nodes for each source-destination pair. Packets transmission at each node follows a Poisson distribution and traffic with mixed packet rates is considered. Worst case performances are obtained using a semianalytical procedure that allows to account for multiple access interference and realistic propagation conditions. The proposed calculation procedure can be used for sensor network design based on multi-hop Aloha as well as for the analysis of an existing installation. The importance of the coverage radius on the performance of the UWB sensor network is discussed.

Wireless local area networks (WLANs) based on IEEE 802.11b standard are widely deployed to provide network connectivity without being tethered off of a wired network. An accurate planning of indoor radio networks and/or the setup of localization procedures based on IEEE 802.11 requires the characterization of the propagation channel. Starting from experimental data obtained in the campus area of the University of Rome Tor Vergata we evaluated the parameters for different multiwall (MVV) like path loss models. Differently from the standard MW model indicated in the literature, we included losses due to doors and fire proof doors that according to their status, open or closed, may lead to significant contributions to the overall attenuation. The developed channel model was used in a computer simulator for the optimal positioning of the access points inside the campus' buildings.

Ultra wide bandwidth (UWB) spread-spectrum techniques will play a key role in short range wireless connectivity providing high bit rates, low power consumption and location capabilities. UWB can be used in the design of advanced wireless local and personal area networks providing integrated multimedia services to nomadic users within hot-spot areas. Due to the very large UWB signal bandwidth, the assessment of the possible interference caused by UWB devices on already existing narrowband systems is important to ensure not conflicting coexistence and, therefore, to guarantee acceptance of UWB technology worldwide. This paper investigates on the coexistence between an UWB-based system and WCDMA-UMTS terminals. UWB interference on the UMTS terminal is evaluated accounting for the UWB signals characteristics and the UWB network architecture. The dependence of the interference from the UWB signal parameters is analyzed through computer simulation and demonstrates that, in all practical cases, UWB system can coexist with UMTS terminals without causing any dangerous interference.

Ultra wideband (UWB) is a potential key technology for the development of future short-range indoor radio communication systems providing very high bit rates services, low power consumption and location capabilities. In this paper we provide a semi-analytic approach to evaluate the system outage probability for a master-slave network based on UWB direct sequence code division multiple access scheme. The proposed approach for system analysis is quite flexible and allows us to easily include realistic path loss models, power control and multiple access interference. The technique has been validated by comparing the semi-analytic data with those from classical Monte Carlo simulation and obtaining results in very good agreement. The UWB coverage-capacity tradeoff is also investigated.

With the new release of the Federal Communication Commission on matters of regulation of marketing and operation of ultra-wideband (UWB) devices, an analytical framework to enable tractable analysis of the spectrum shape of these signals is needed. We extend the framework introduced by W. A. Gardner to the case of UWB signals. We introduce a generalized UWB signal model that can be specialized to represent the traditional time-hopping (TH) technique as well as the alternative multiple access technique that we indicate as delay coded sequence (DCS). The DCS technique resembles the traditional direct sequence spread spectrum techniques, but it is not based on pulse polarity inversion. The considered matrix signal formulation allows us to easily evaluate the spectral characteristics of UWB signals under many different operating conditions: continuous or discontinuous transmissions, random or periodic scrambling operations, with or without jitter. We evaluate the spectrum of the general UWB signal under the random scrambling assumption, then we specialize it to the TH and DCS cases and discuss the variability of the spectra to some critical design parameters. We obtain an asymptotic expression of the general UWB spectrum that we use to evaluate the UWB interference power at the output of a generic receiver.

Bluetooth is a low-cost, short-range wireless technology capable of providing many communication functionalities, ranging from wire replacement to simple personal area networking. In Bluetooth local networking applications, a critical issue still under study is the evaluation of the network performance when multiple piconets are simultaneously active in the same area, thus, causing mutual interference. We provide a closed-form expression for the packet loss probability in Bluetooth dense piconet area accounting for capture effects due to propagation losses. The effectiveness of the proposed approach is assessed by comparing the analytical results with those obtained from Monte Carlo simulations. By considering different scenarios, we show the dependence of results on the geometry and on the characteristics of the environment. It is observed that packet loss probability can significantly change with the position of the reference receiver in the area, as well as with the extension of the piconets area as compared with the coverage area of the receiver. We use the packet loss probability to evaluate the upper and the lower bounds of the network aggregate throughput and the average packet transmission time. Due to propagation effects, large variations of these parameters with the position of the reference receiver in the area are evidenced.

Abstract Ultra Wide Bandwidth (UWB) techniques are getting an increased importance due to their many features such as high bit rates availability, low power consumption and location capabilities. UWB technology enables the development of advanced wireless local area networks providing integrated multimedia services to nomadic users over hot‐spot areas. The assessment of the possible interference caused by UWB devices on already existing narrowband and wideband systems is fundamental to ensure not‐conflicting coexistence and, therefore, the acceptance of UWB technology worldwide. In this paper we analyze coexistence between an indoor UWB system and an outdoor fixed wireless access (FWA) system operating in the 3.5–5.0 GHz band. We consider a realistic UWB master/slave system architecture using pulse amplitude modulated spread spectrum signals for multiple access and we evaluate the UWB system interfering power in the FWA band accounting for the UWB power spectrum shape. Both upstream and downstream communication directions are analyzed. We show through computer simulation, that in many practical cases UWB system can coexist with FWA without causing any dangerous interference. Copyright © 2004 John Wiley & Sons, Ltd.

We provide a closed-form expression for the packet loss probability in Bluetooth networks accounting for capture effects due to propagation losses. The effectiveness of the proposed approach is assessed comparing the analytical results with those obtained from Monte Carlo simulations. By considering different scenarios, we show the dependence of results on the geometry and on the characteristics of the environment. It is observed that packet loss probability can significantly change with the position of the reference receiver in the area, as well as with the extension of the served area as compared with the coverage area of the receiver.

For code-division multiple-access (CDMA) cellular communications synchronous operation offers significant advantages over asynchronous operation. This feature has been already included in second-generation systems, such as the CdmaOne based on the IS-95 standard. Nonetheless, synchronous operation does not seem to be assessed as a basic system option for third-generation systems. This is mainly due to the contrasted choice of having global positioning system (GPS) receivers located at any of the base transceiver stations (BTSs) to perform station synchronization. However, the existing CdmaOne interface permits time transfer between the various BTSs and a simple time difference measurement technique can provide an internal, network-based means for time synchronization of base stations clocks. This paper considers a previously proposed approach based on the pilot strength measurements message delivered by every mobile station (MS), combined with round trip delay measurements that BTSs perform on the MS transmissions. We consider some possible algorithms to reduce time misalignments, and continuously phase-lock the clocks at different BTSs. Having developed an appropriate analytical/simulation approach, in the environment of a CDMA network, the paper evaluates and compares the performance of two suitable centralized architecture configurations, i.e., master-slave synchronization (MSS) and mutual synchronization (MUS). Both network architectures turn out to be applicable and provide suitable timing performance. Finally, the paper provides a preliminary discussion on some related issues, such as GPS avoidance, synchronization of BTSs inside buildings, tunnels, and subways and hybrid MSS/MUS synchronization network architectures.

Abstract Smart antennas are a powerful means to provide the increased bandwidth efficiency needed to deliver advanced third generation (3G) interactive multimedia services anywhere and anytime. In this paper we focus on the development of smart antennas located at the base stations of a code division multiple access (CDMA) cellular system. First, we review the main characteristics of antenna array systems and highlight some issues related to the inclusion of smart antennas in a 3G CDMA system. A classification of the proposed beamforming techniques and a discussion on the advantages and drawbacks of smart antennas are provided. Then, we introduce an original smart antenna technique based on rotation and resizing of the available sectors much simpler than common smart antennas based on beamforming techniques addressing a specific user. We discuss on the impact of the proposed technique in the base station architecture. Finally, we provide simulation results in order to show the effectiveness of the proposed approach and to relate transmission performance to system parameters. It turns out that the smart sectorization technique provides significant capacity improvements under statistically uniform user distribution (up to about 80 per cent for data traffic). Copyright © 2002 John Wiley & Sons, Ltd.