[Show abstract][Hide abstract] ABSTRACT: Connected Vehicles is a currently hot topic, which can be said to have emerged under the inspiration of the Internet of Things. Motivated by a myriad of traffic safety, decongestion, and respectively, driver comfort applications, the subject is gaining more and more popularity among both researchers and industry. Our interests in the topic are focused on both the communication links and the precise localization of the vehicles. These topics are catalyzed by applications such as high precision collaborative vehicular positioning and autonomous driving. The robustness of the radio links in this context is hence at the backbone of vehicular ad-hoc networks, and respectively, of initial cooperative positioning estimates. The subsequent communication protocol is based on the IEEE 802.11p standard of the WAVE (Wireless Access in Vehicular Environments) technology. As part of the post-transmission channel modeling, we introduce in this paper a new channel estimator structure based on a low complexity adaption of Kohonen's Self-Organizing Map complemented by a filtered decision feedback layer. Furthermore, we study the key factors that would lead to a further performance optimization of our estimator while also comparing it to the state of the art solutions existing already in the literature.
[Show abstract][Hide abstract] ABSTRACT: We study the power optimization policy to maximize the average transmission rate in an energy harvesting wireless network. The addressed scenario considers an energy harvesting transmitting node where the energy arrives in discrete packets following a Poisson process. The challenge is then to optimally model the transmission period T according only to the statistical knowledge of the energy arrival process. A higher power would quickly empty the battery causing outage, while, a lower rate would inefficiently accumulate energy not to be used. A math- ematical formulation of the optimal policy is derived, a
[Show abstract][Hide abstract] ABSTRACT: Cooperative intelligent transport system (C-ITS) applications rely on knowledge of the geographical positions of vehicles. Unfortunately, satellite-based positioning systems (e.g., GPS and Galileo) are unable to provide sufficiently accurate position information for many important applications and in certain challenging but common environments (e.g., urban canyons and tunnels).
This project addresses this problem by combining traditional satellite systems with an innovative use of on-board sensing and infrastructure-based wireless communication technologies (e.g., Wi-Fi, ITS-G5, UWB tracking, Zigbee, Bluetooth, LTE...) to produce advanced, highly-accurate positioning technologies for Cooperative intelligent transport system.
[Show abstract][Hide abstract] ABSTRACT: We consider using a secret key generation (SKG) scheme for vehicular ad hoc network (VANET) operating on the 802.11p (WAVE) standard. Due to the large number of very time-limiting vehicle-to-vehicle (V2V) and vehicle-to-infrastructure (V2I) communications, an on-the-fly dynamic key generation, as opposed to a hardcoded computational secrecy method, is required. The SKG schemes that rely on the entropy of the channel are not suitable for short-range communication (SRC) systems. This proposed phase-based dynamic SKG scheme relies only on the reciprocity of the channel between the two vehicles/infrastructure as a common source of randomness, which is not available to a third party/eavesdropper. In addition, the concept of geometrical secrecy is introduced to describe the area within which the proposed method is immune to eavesdropping.
[Show abstract][Hide abstract] ABSTRACT: We perform an analysis of the secrecy outage of random networks under Nakagami-m fading with multiple transmit antennas. Specifically, using a network model that accounts for uncertainties both in node locations (distances) and channel coefficients (fading), we derive the distribution of the best path gain of eavesdroppers using Probability Generating Functional property of Poisson Point Process (PPP). Using this result, the
secrecy outage probability and the conditional secrecy outage probability of random networks with multiple eavesdroppers are obtained, with basic factors such as the density of eavesdropping nodes, the number of transmit antennas and the fading figure all accounted for by explicit parameters. The impact of transmission factors, including number of transmit antennas, fading figure, legitimate node distance and node density are studied and analysed in numerical results.
[Show abstract][Hide abstract] ABSTRACT: The authors provide compact and exact expressions for the extreme eigenvalues of finite Wishart matrices with arbitrary dimensions. Using a combination of earlier results, which they refer to as the James–Edelman–Dighe framework, not only an original expression for the cumulative distribution function (CDF) of the ‘smallest’ eigenvalue is obtained, but also the CDF of the ‘largest’ eigenvalue and the probability density functions of both are expressed in a similar and convenient matrix form. These compact expressions involve only inner products of exponential vectors, vectors of monomials and certain coefficient matrices which therefore assume a key role of carrying all the required information to build the expressions. The computation of these all-important coefficient matrices involves the evaluation of a determinant of a Hankel matrix of incomplete gamma functions. They offer a theorem which proves that the latter matrix has ‘catalectic’ properties, such that the degree of its determinant is surprisingly small. The theorem also implies a closed-form and numerical procedure (no symbolic calculations required) to build the coefficient matrices.
No preview · Article · May 2015 · IET Communications
[Show abstract][Hide abstract] ABSTRACT: In this paper, we present an accurate ranging technique to obtain multiple distance estimates from a single realization of range measurements by proposing a new slope sampling and peak search ranging algorithm.
The slope sampling algorithm is then compared against the superresolution ranging techniques presented in  for distance estimation. The computed measured distances are utilized to estimate the target’s position using a localization algorithm requiring an initial guess obtained using trilateration techniques.
Finally, we present results for applications in wireless local- ization, where necessary performance measures under different localization scenarios are to be satisfied.
[Show abstract][Hide abstract] ABSTRACT: We revisit the problem of describing optimal anchor geometries that result in the minimum achievable MSE by employing the Cramer Rao Lower bound. Our main contribution is to show that this problem can be cast onto the whelm of modern Frame Theory, which not only provides new insights, but also allows the straightforward generalization of various classical results on the anchor placement problem. For example, by employing the frame potential for single-target localization we see that the directions of the anchors, as seen from the target, should optimally be as orthogonal as possible and that the existence of an optimal geometry for an arbitrary number of anchors is governed by a fundamental inequality. Furthermore, the frame-theoretic approach allows for simple derivation of some properties on optimal anchor placement that prove to be useful in a tractable approach for the more complex, multi-target anchor placement problem. In a more general sense, the paper builds a refreshing bridge between the classical problem of wireless localization and the powerful domain of Frame Theory, with far-reaching potential.
[Show abstract][Hide abstract] ABSTRACT: This position paper is an output of the Activity Chain 05 in the Internet of Things Cluster (IERC). The IERC has created a number of activity chains to support close cooperation between the projects addressing IoT topics and to form an arena for exchange of ideas and open dialog on important research challenges. The activity chains are defined as work streams that group together partners or specific participants from partners around well-defined technical activities that will result into at least one output or delivery that will be used in addressing the IERC objectives. IERC Activity Chain 05 is the crossproject activity, which has the objective to investigate how research can foster a trustworthy IoT at European level, identify solutions to protect the security and privacy of the citizens. These objectives can be quite challenging at the regulatory, ethical, market and technical levels.
Next to Trusted IoT, privacy, data protection and security, which is at the core of policy issues already addressed today by the IERC, there are also other policy issues of concern that will need to be addressed if IoT is to be accepted by society, and wanted to make a difference where it can. These issues in
particular include global governance (how are we going to make this all happen, in the full understanding that the way forward will need to involve multiple stakeholders around the globe), ethics (what would we expect those “global IoT solutions” to respect, and how will the way IoT is implemented potentially affect the understanding of ethical impact), and radio frequency spectrum. What can we do to make sure those issues are addressed, and how can we assure citizens and policy makers are well informed, thus to be able to
take conscious decisions when moving forward.
In this context, this position paper identifies relevant IoT challenges and describes solutions defined by the cluster projects, which can be used to address these challenges. FP7 projects have spent considerable effort in the definition of technical solutions and frameworks for the IoT domain. In some
case, these solutions may overlap or they may leave gaps, which might become a basis for proposals for future IERC research activities and research programs like H2020. These research opportunities are identified and described in this position paper. Future activities of AC05 must address the integration of the
identified solutions in this position paper with the results from the other Activity Chains in the IERC.
[Show abstract][Hide abstract] ABSTRACT: We demonstrate analytically that the contribution of cooperation in improving the accuracy of distributed network localization has a fundamentally structural nature, rather then statistical as widely believed. To this end we first introduce a new approach to build Fisher Information Matrices (FIMs), in which the individual contribution of each cooperative pair of nodes is captured explicitly by a corresponding information vector. The approach offers new insight onto the structure of FIMs, enabling us to easily account for both anchor and node location uncertainties in assessing lower bounds on localization errors. Using this construction it is surprisingly found that in the presence of node location uncertainty and regardless of ranging error variances or network size, the Fisher information matrix (FIM) terms corresponding to the information added by node-to-node cooperation nearly vanish. In other words, the analysis reveals that the key contribution of cooperation in network localization is not to add statistical node-to-node information (in the Fisher sense), but rather to provide a structure over which information is better exploited.
[Show abstract][Hide abstract] ABSTRACT: We examine the secrecy outage of unicast links in cognitive wireless sensor networks (CWSN) in the presence of
interference from sensor users and model the interference power with suitable approximation techniques. Precisely, we perform a thorough analysis of the secrecy outage under the impact of Nakagami-m fading and Shadowing. The conclusions attained from our analysis can be specified as - the secrecy capacity can be maintained at lower equivocation rates, the impact of shadowing is severe as it increases the secrecy outage quickly and eavesdropper’s density impacts secrecy outage the most which is closely followed by the equivocation ratio.
[Show abstract][Hide abstract] ABSTRACT: We consider the problem of performing ranging measurements between a source
and multiple receivers efficiently and accurately, as required by
distance-based wireless localization systems. To this end, a new multipoint
ranging algorithm is proposed, which is obtained by adapting superresolution
techniques to the ranging problem, using for the sake of illustration the
specific cases of ToA and PDoA, unified under the same mathematical framework.
The algorithm handles multipoint ranging in an efficient manner by employing an
orthogonalized non-uniform sampling scheme optimised via Golomb rulers. Since
the approach requires the design of mutually orthogonal sets of Golomb rulers
with equivalent properties -- a problem that founds no solution in current
literature -- a new genetic algorithm to accomplish this task is presented,
which is also found to outperform the best known alternative when used to
generate a single ruler. Finally, a CRLB analysis of the overall optimised
multipoint ranging solution is performed, which together with a comparison
against simulation results validates the proposed techniques.
Preview · Article · Aug 2014 · IEEE Transactions on Wireless Communications
[Show abstract][Hide abstract] ABSTRACT: This paper presents an experimentally-driven assessment of eigenvalue-based detection (EBD) for cognitive radio (CR), which puts such techniques to a realistic test beyond the assumptions of Gaussian target signals and the availability of large numbers of samples for detection purposes typically adopted in purely theoretical analysis. It is shown that these approximations lead to significantly optimistic results compared to those obtained in laboratory employing standard-compliant signals. Instead of relying on asymptotically large sample sizes, it is also found that better performance is obtained by splitting samples into smaller blocks (multiple covariance matrices), followed by an adequate combining of results based on corresponding test statistics. This approach, referred to as EBD with partial decision combining, is shown to outperform the standard (single-matrix) approach.
[Show abstract][Hide abstract] ABSTRACT: We survey the state-of-the-art on the Internet-of-Things (IoT) from a wireless communications point of view, as a result of the European FP7 project BUTLER which has its focus on pervasiveness, context-awareness and security for IoT. In particular, we describe the efforts to develop so-called (wireless) enabling technologies, aimed at circumventing the many challenges involved in extending the current set of domains (“verticals”) of IoT applications towards a “horizontal” (i.e. integrated) vision of the IoT. We start by illustrating current research effort in machine-to-machine (M2M), which is mainly focused on vertical domains, and we discuss some of them in details, depicting then the necessary horizontal vision for the future intelligent daily routine (“Smart Life”). We then describe the technical features of the most relevant heterogeneous communications technologies on which the IoT relies, under the light of the on-going M2M service layer standardization. Finally we identify and present the key aspects, within three major cross-vertical categories, under which M2M technologies can function as enablers for the horizontal vision of the IoT.
[Show abstract][Hide abstract] ABSTRACT: This paper reveals an impairment of well-known path-loss model generally assumed in conventional works with radio frequency (RF) energy harvesting. We will prove that, when RF energy harvesting is considered in a large-scale network, the summation of energy transferred to nodes in the network diverges while the radiated energy must be finite. Thus, we propose a new absorption function meeting this law and derive several expressions of average harvested energy based on the model. Furthermore, the effectiveness of RF energy harvesting with Poisson point process (PPP) network with a single transmitter is demonstrated.
[Show abstract][Hide abstract] ABSTRACT: We consider the secret key generation (SKG) problem for short-range communication (SRC) systems. Specifically, we focus on the problem that secret key generation schemes relying on the entropy of the channel are not suitable for SRC systems, which are characterized by the absence of fading. To mitigate this problem, we introduce the concept of geometric secrecy and propose a new phase-based SKG which relies only on the reciprocity of the channel in order to securely generate mutual secret keys in the presence of an eavesdropper. The method is validated via a theoretical analysis which shows that for the signal-to-noise ratio (SNR) ranges typical of SRC systems, an efficient secret key generation can be achieved.
[Show abstract][Hide abstract] ABSTRACT: Motivated by the recent advances on internet of things (IoT) and the importance that location information has on many application scenarios, this article offers references to theoretical and localization-algorithmic tools that can be utilised in connection with IoT. We develop this discussion from basic to sophisticated localization techniques covering also some less-intuitive notions of localization, e.g. semantic positioning, for which we provide a novel solution which overcome the problem of privacy. We analyze the localization problem from a mathematical perspective; reviewing the most common and best-performing class of localization methods based on optimization and algebraic approaches and we discuss benefits of location information in a wireless system. In this regard we discuss few concrete applications scenario currently under investigation in the largest EU project on IoT, namely the FP-7 Butler project, how location information is one of the key enabling technology in the IoT. In addition to the theoretical aspect, this article provides references to the pervasive localization system architecture using the smart sensors developed within the Butler project.
[Show abstract][Hide abstract] ABSTRACT: Although during the last decade considerable efforts have been invested in the integration of different wireless technologies, a new surge of interest is arising due to the upcoming internet of things (IoT) in which many relevant application scenarios rely on location information. However, due to the heterogeneity of the devices, ergo the heterogeneity of information available, novel indoor positioning algorithms capable to account for different types of information must be designed. Differently from the vast majority of localization solutions currently available which rely on one specific type of observation, e.g. range information only, in this article we consider the localization problem of multiple sources from range and angle measurements. To this end we first study the benefit of heterogeneous information via the rigidity theory and the Cramèr-Rao Lower Bound (CRLB) and then we show how to utilize an extension of the Euclidean-kernel, i.e. the Edge-kernel, to perform robust positioning under Non-Line-of-Sight (NLOS) conditions. In particular with reference to the latter contribution it is shown how to exploit the robust principal component analysis theory to improve the edge-kernel recovery and in turn the estimated target's locations.
[Show abstract][Hide abstract] ABSTRACT: This paper addresses the problem of vehicle position estimation in dense urban environments, where traditional global positioning system (GPS)-based localisation techniques are severely affected by non line-of-sight (NLOS) signal propagation and multipaths presence. Assuming that GPS signals are fairly received only by a very small fraction of vehicles at the border of the urban environment, we propose a solution based on vehicle to vehicle (V2V) communication to propagate this information to the whole network. As a consequence, this multihop scheme allows vehicles to estimate its own position collecting their cumulative distances to border vehicles. Finally we introduce a new analytical framework to verify the fundamental performance of the proposed solution in term of position estimate error bounds, jointly considering the uncertainty introduced by the multihop process and by the GPS localization.
[Show abstract][Hide abstract] ABSTRACT: Information-theoretic security at the physical layer has been proposed to increase the privacy of wireless communications due to its achievable characteristics: unbreakability, provability, and quantifiability. An accurate and powerful analytical framework aimed at deriving the achievable security level provided by Gaussian channels is presented and validated. Its accuracy is assessed by mean of a narrowband fading scenario simulator with multi-antenna transceivers. The impact on the security level of a number of aspects, such as the Eavesdropper's distance as well as the number and distance of antennas in MIMO systems is finally discussed.