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Spatial correlation has been recognized by 3GPP as one of the key elements in millimeter-wave (mmWave) channel modeling. Correlated channel behavior is induced by macro objects, such as buildings, as well as by micro objects, including humans around the mmWave receivers. The 3GPP's three-dimensional (3D) spatially consistent channel model designed to capture these phenomena assumes a-priori knowledge of the correlation distance between the receivers. In this paper, we propose a novel spatially-consistent human body blockage state generation procedure, which extends the standardized 3D channel model by 3GPP to capture the correlation between the line-of-sight (LoS) links and the reflected cluster states affected by human body blockage. The proposed model is based on analytical expressions for the conditional link state probability, thus permitting the parametrization of the spatial field of receivers. It also does not require any a-priori information on the correlation distance as the latter is identified explicitly based on the environmental parameters. We compare the results for the proposed model with those obtained with the uncorrelated blockage model and conclude that in many special cases correlation manifests itself in quantitatively different propagation conditions experienced at the nearby receivers. acceptedVersion

The use of highly directional antenna radiation patterns for both the access point (AP) and the user equipment (UE) in the emerging millimeter-wave (mmWave)-based New Radio (NR) systems is inherently beneficial for unicast transmissions by providing an extension of the coverage range and eventually resulting in lower required NR AP densities. On the other hand, efficient resource utilization for serving multicast sessions demands narrower antenna directivities, which yields a trade-off between these two types of traffic that eventually affects the system deployment choices. In this work, with the tools from queuing theory and stochastic geometry, we develop an analytical framework capturing both the distance- and traffic-related aspects of the NR AP serving a mixture of multicast and unicast traffic. Our numerical results indicate that the service process of unicast sessions is severely compromised when (i) the fraction of unicast sessions is significant, (ii) the spatial session arrival intensity is high, or (iii) the service time of the multicast sessions is longer than that of the unicast sessions. To balance the multicast and unicast session drop probabilities, an explicit prioritization is required. Furthermore, for a given fraction of multicast sessions, lower antenna directivity at the NR AP characterized by a smaller NR AP inter-site distance (ISD) leads to a better performance in terms of multicast and unicast session drop probabilities. Aiming to increase the ISD, while also maintaining the drop probability at the target level, the serving of multicast sessions is possible over the unicast mechanisms, but it results in worse performance for the practical NR AP antenna configurations. However, this approach may become feasible as arrays with higher numbers of antenna elements begin to be available. Our developed mathematical framework can be employed to estimate the parameters of the NR AP when handling a mixture of multicast and unicast sessions as well as drive a lower bound on the density of the NR APs, which is needed to serve a certain mixture of multicast and unicast traffic types with their target performance requirements. acceptedVersion

This article aims to put forward the utilization of onshore narrowband IoT (NB-IoT) infrastructure for tracking of containers transported by marine cargo vessels while operating near the coastline. We introduce and evaluate three connectivity strategies, including direct sensor-to-onshore base station (BS) transmission as well as two relay-aided schemes using dedicated vessel-BS or unmanned-aerial-vehicle (UAV)-mounted BS as intermediate nodes. To assess and compare the proposed schemes in terms of the message loss and delay metrics as well as sensor lifetimes, we first employ stochastic geometry to characterize the connectivity process with the onshore deployment and then resort to system-level simulations. Our results indicate that the direct access option suffers from the poorest performance. The relay-based alternatives allow to dramatically improve the system operation by effectively distributing the transmission requests over time at the relay side and thus mitigating contention. Furthermore, gains enabled with UAV relaying are due to extended coverage that increases the available BS density. The considered relaying operation may help tolerate intermittent connectivity across a broad range of system parameters. acceptedVersion

The blockchain technology is currently penetrating different areas of the modern Information and Communications Technology community. Most of the devices involved in blockchain-related processes are specially designed targeting only the mining aspect, i.e., solving the computational puzzle task. At the same time, the use of wearable and mobile devices may also become a part of eCommerce blockchain operation, especially during the on-charge time. The paper considers the possibility of using a large number of constrained devices to support the operation of the blockchain with a low impact on battery consumption. The utilization of such devices is expected to improve the system efficiency as well as to attract a more substantial number of users. This paper contributes to the body of knowledge with a survey of the main applications of blockchain for smartphones along with existing mobile blockchain projects. It also proposes a novel consensus protocol based on a combination of Proof-of-Work (PoW), Proof-of-Activity (PoA), and Proof-of-Stake (PoS) algorithms for efficient and on-the-fly utilization on resource-constrained devices. The system was deployed in a worldwide testnet with more than two thousand smartphones and compared with other projects from the user-experienced metrics perspective. The results prove that the utilization of PoA systems on a smartphone does not significantly affect the lifetime of the smartphone battery while existing methods based on PoW have a tremendous negative impact. Finally, the main open challenges and future investigation directions are outlined. publishedVersion

Due to the need for larger bandwidth, future mobile networks may primarily operate over millimeter-wave (mmWave) bands. In this regard, one of the central research topics today is mmWave channel modeling. However, highly mobile vehicle-to-vehicle (V2V) mmWave channels pose an open question because conducting measurements may be challenging in this environment. The existing publications on mmWave V2V channel modeling consider line-of-sight (LoS) or single-blocker scenarios. Accordingly, the impact of interference from adjacent vehicles is not taken into account. Conventional analytical models suggest that path loss (PL) strikes equally in all directions whereas measurements are inherently directional, especially in the case of mmWave propagation. Recently, it was proposed to synthesize the omnidirectional PL from directional measurements. However, with this method, the resulting PL is underestimated. Moreover, theoretical models assume that vehicular transceivers follow a certain predetermined distribution, which may not be accurate in real-world scenarios. Several works take into account the directionality of an antenna pattern when the antenna orientation is known. However, the effects of reflection, diffraction, and transmission through obstacles are not considered. One way to avoid these limitations is to use ray-based simulations. However, the ray-launching (RL) approach does not specify any criteria for the directionality of the antenna patterns. Assuming omnidirectional PL appears impractical for mmWave transmission where directional communication is crucial to combat high PL. In this paper, we propose an approach for synthesizing directional PL based on extensive RL modeling. For the obtained directional and omnidirectional PL, we parametrize the close-in (CI) and float-intercept (FI) channel models. As a result of our modeling, from 0.1 to 2.7 for the LoS and from 0.1 to 2.6 for the non-LoS (NLoS) higher PL exponent is observed as compared to the omnidirectional case. publishedVersion

Dynamic blockage of millimeter-wave (mmWave) radio propagation paths by dense moving crowds calls for advanced techniques to preserve session continuity in the emerging New Radio (NR) systems. To further improve user performance by balancing the new and ongoing session drop probabilities, we investigate the concept of guard capacity – reserving a fraction of radio resources at the NR base stations exclusively for the sessions already accepted for service. To this aim, we develop a detailed mathematical framework that takes into account the key effects in mmWave systems, including the heights of communicating entities, blocker geometry and mobility, modulation and coding schemes and antenna array geometry, as well as radio propagation and queuing specifics. Using our framework, which enables sessions to change their resource requirements during service, we demonstrate that reserving even a small fraction of bandwidth (less than 10%) exclusively for the sessions already accepted by the system allows to enhance session continuity at the expense of a slight growth in the new session drop probability as well as a small decrease in the resource utilization (approximately 5–7%). Furthermore, guard capacity is shown to perform better in overloaded conditions and with sessions having high data rate requirements, thus making it particularly useful for the NR systems. Our results indicate that guard capacity is a viable option for improving session continuity that can be used by the network operators in combination with other techniques, such as multi-connectivity, to maintain user experience. acceptedVersion

One of the recent major steps towards 5G cellular systems is standardization of 5G New Radio (NR) operating in the millimeter wave (mmWave) frequency band. This radio access technology (RAT) will potentially provide extraordinary rates at the access interface enabling the set of new bandwidth-greedy applications. However, the blockage of the line-of-sight (LoS) path between 3GPP NR access point (AP) and the user equipment (UE) is known to drastically degrade the performance of the NR communication links thus leading to potential outage conditions. Although the problem of characterizing LoS blockage process has been addressed in the recent literature, the proposed models are mostly limited to stationary locations of APs and UE. In our study, we characterize properties of the LoS blockage process under simultaneous mobility of both blockers and UE. The model is then extended to the cases of Poisson AP deployment, multi-connectivity, and mobility of AP representing ‘trilateral’ (three-sided) mobility model. We also specify a Markov-based model of the blockage process that can be efficiently used in both system level simulations and analytical analysis of 3GPP NR systems. Using this model we demonstrate how to derive various metrics of interest including (i) ,fraction of time in blockage, (ii) SNR and capacity process dynamics, (iii) probability that at time t UE is at the blockage or non-blockage state, (iv) mean and distribution of time to an outage. acceptedVersion

Software-defined networking (SDN) is a novel network paradigm that enables flexible management for networks. However, with the increase in network capacity, a single controller of SDN has many limitations on both performance and scalability. Distributed multi-controller deployment is a promising method to satisfy fault tolerant and scalability. There are still open research issues related to controllers placement, and the optimal number of deployed controllers. In this paper, a dynamic optimization algorithm that is based on the Salp Swarm Optimization Algorithm (SSOA) is developed with the introduction of chaotic maps for enhancing the optimizer’s performance. The algorithm dynamically evaluates the optimum number of controllers and the optimal connections between switches and controllers in large scale SDN networks. In order to evaluate the proposed algorithm, several experiments were conducted and implemented in various scenarios. Moreover, the algorithm was compared to the linear and meta-heuristic algorithms. Simulation results show that the proposed algorithm outperforms meta-heuristic algorithms and a game theory based algorithm in terms of execution time and reliability. Keywords: Controller placement, Latency, Optimization algorithm, SDN, Swarm, Utilization

IoT applications constitute one of the fastest developing areas in today's technology and at the same time pose the most demanding challenges for the respective radio access network design. While the initial studies in IoT were focused primarily on scaling the existing radio solutions for higher numbers of small-data and low-cost sensors, the current developments aim at supporting wearable augmented/virtual reality platforms, moving industrial robots, driving (semi-)autonomous vehicles, and flying drones, which produce large amounts of data. To satisfy these rapidly growing performance demands, the 5G-grade IoT is envisioned to increasingly employ millimeter-wave (mmWave) spectrum, where wider bandwidths promise to enable higher data rates and low-latency communication. While the mainstream trend in mmWave-based IoT is to rely on licensed bands around 28 GHz or leverage unlicensed bands at 60 GHz, in this work we introduce a conceptual vision for the integrated use of these frequencies within a single radio access system named 5G over unlicensed spectrum or 5G-U. We study the performance of 5G-U in supporting stringent IoT use cases, discuss and compare the alternative strategies for spectrum management in 5G-U, and demonstrate that a harmonized utilization of licensed and unlicensed bands provides notable performance improvements in both device-centric and network-centric metrics. Finally, we offer useful guidelines for future implementations of 5G-U and detail its potential applications in the area of advanced IoT services. acceptedVersion

As the ratification of 5G New Radio technology is being completed, enabling network architectures are expected to undertake a matching effort. Conventional cloud and edge computing paradigms may thus become insufficient in supporting the increasingly stringent operating requirements of \emph{intelligent~Internet-of-Things (IoT) devices} that can move unpredictably and at high speeds. Complementing these, the concept of fog emerges to deploy cooperative cloud-like functions in the immediate vicinity of various moving devices, such as connected and autonomous vehicles, on the road and in the air. Envisioning gradual evolution of these infrastructures toward the increasingly denser geographical distribution of fog functionality, we in this work put forward the vision of dense moving fog for intelligent IoT applications. To this aim, we review the recent powerful enablers, outline the main challenges and opportunities, and corroborate the performance benefits of collaborative dense fog operation in a characteristic use case featuring a connected fleet of autonomous vehicles., Comment: 7 pages, 5 figures, 1 table. The work has been accepted for publication in IEEE Communications Magazine, 2019. Copyright may be transferred without notice, after which this version may no longer be accessible

The use of advanced AR/VR applications may benefit the efficiency of collaborative public protection and disaster relief (PPDR) missions by providing better situational awareness and deeper real-time immersion. The resultant bandwidth-hungry traffic calls for the use of capable millimeter-wave (mmWave) radio technologies, which are however susceptible to link blockage phenomena. The latter may significantly reduce the network reliability and thus degrade the performance of PPDR applications. Efficient mmWave-based mesh topologies need to, therefore, be constructed that employ advanced multi-connectivity mechanisms to improve the levels of connectivity. This work conceptualizes predictive blockage avoidance by leveraging emerging artificial intelligence (AI) capabilities. In particular, AI-aided blockage prediction permits the mesh network to reconfigure itself by establishing alternative connections proactively, thus reducing the chances of a harmful link interruption. An illustrative scenario related to a fire suppression mission is then addressed by demonstrating that the proposed approach dramatically improves the connection reliability in dynamic mmWave-based deployments. publishedVersion

Fifth-generation (5G) cellular systems are expected to orchestrate a variety of air interfaces. In this heterogeneous setting 4G, LTE systems will remain of special importance providing service over a relatively large area not covered with the 3GPP new radio technology. However, the scarcity of radio resources below 6 GHz as well as constantly increasing user traffic demands call for efficient offloading strategy from the LTE network. In this paper, we consider and compare two LTE session offloading strategies, including LAA and WiFi offloading. Although by design, the LAA system supports quality-of-service (QoS) guarantees in terms of minimum throughput, the assured performance might still be violated by resource reallocations when satisfying the compulsory fairness criteria. To assess and compare the performance of these schemes, we develop an analytical framework that takes into account specifics of duty-cycle schedule-based Licensed Assisted LTE Access (LAA) system with connection admission control (CAC), resource reallocation mechanism, and realistic elastic traffic nature. As a special case of the developed framework, we also address the offloading of QoS-aware LTE sessions into conventional WiFi. Our numerical results indicate that WiFi offloading is characterized by a significantly greater number of offloaded sessions. However, this advantage comes at the expense of severe performance degradation in terms of minimum throughput guarantees. Implementing CAC procedures, LAA efficiently addresses this problem. We conclude that WiFi offloading of QoS-aware LTE sessions can be used in light traffic conditions only. On the other hand, offloading to the schedule-based LAA system allows preserving QoS over a wide range of arrival traffic statistics. publishedVersion

The future of industrial applications is shaped by intelligent moving IoT devices, such as flying drones, advanced factory robots, and connected vehicles, which may operate (semi-)autonomously. In these challenging scenarios, dynamic radio connectivity at high frequencies, augmented with timely positioning-related information, becomes instrumental to improve communication performance and facilitate efficient computation offloading. Our work reviews the main research challenges and reveals open implementation gaps in IIoT applications that rely on location awareness and multi-connectivity in super high and extremely high frequency bands. It further conducts a rigorous numerical investigation to confirm the potential of precise device localization in the emerging IIoT systems. We focus on positioning- aided benefits made available to multi-connectivity IIoT device operation at 28 GHz, which notably improve data transfer rates, communication latency, and the extent of control overhead. acceptedVersion

With the proliferation of machine-to-machine (M2M) communication in the course of the last decade, the importance of low-power wide-area network (LPWAN) technologies intensifies. However, the abundance of accurate propagation models proposed for these systems by standardization bodies, vendors, and research community hampers the deployment planning. In this paper, we question the selection of accurate propagation models for Narrowband IoT (NB-IoT), LoRaWAN, and Sigfox LPWAN technologies, based on extensive measurement campaign in two mid-size European cities. Our results demonstrate that none of the state-of-the-art models can accurately describe the propagation of LPWAN radio signals in an urban environment. For this reason, we propose enhancements to the selected models based on our experimental measurements. Performing the fine-tuning of the propagation models for one of the cities, we select Ericsson Urban (NB-IoT, LoRaWAN) and 3GPP (Sigfox) models as the ones providing the closest match. Finally, we proceed to perform cross-validation of the propagation models using the data set for another city. The tuned models demonstrate an excellent match with the real data in the cross-validation phase. They outperform their competitors by at least 20-80% in terms of relative deviation from the measured signal levels presenting the accurate option for NB-IoT, LoRaWAN, and Sigfox deployments planning in mid-size cities. publishedVersion

Dynamic blockage of radio propagation paths between the user equipment (UE) and the 5G New Radio (NR) Base Station (BS) induces abrupt rate fluctuations that may lead to sub-optimal performance of the Transmission Control Protocol (TCP) protocol. In this work, we characterize the effects of dynamic human blockage on TCP throughput at the 5G NR air interface. To this aim, we develop an analytical model that expresses the TCP throughput as a function of the round-trip time (RTT), environmental, and radio system parameters. Our results indicate that the blockage affects TCP throughput only when the RTT is comparable to the blocked and non-blocked state durations when the frequency of state changes is high. However, such conditions are not typical for dynamic body blockage environments allowing TCP to benefit from the high bandwidth of 5G NR systems fully.

Interest in applications based on distributed ledger technology (DLT) is on the rise, with corporations worldwide shifting from simply exploring DLT's potential to creating productive business cases. However, despite the existence of numerous DLT applications, developers are still lacking proper tools and instruments for evaluating system behavior (e.g., performance) of their applications on different distributed ledgers before deployment. Since the behavior of such applications is highly dependent on the characteristics of the distributed ledger they are built upon and changing the distributed ledger after deployment of an application is difficult, selecting the wrong ledger can have severe negative consequences. To address the issue, we conducted an extensive literature review to identify and synthesize published modeling and simulation approaches for distributed ledgers. Based on the results, this paper also presents a research agenda to improve modeling of the system behavior of distributed ledgers and to support the development of distributed ledgers and viable DLT applications. In doing so, we facilitate informed decision-making for suitable modeling or simulation approach, which helps application developers to identify a suitable distributed ledger before implementing an application. In addition, our work contributes to science, as we provide a comprehensive overview and analysis of extant simulation and modeling approaches in DLT that accumulates the current state-of-the-art in the rapidly growing DLT field. acceptedVersion

The present increase of attention toward blockchain-based systems is currently reaching a tipping point with the corporate focus shifting from exploring the technology potential to creating Distributed Ledger Technology (DLT)-based systems. In light of a significant number of already existing blockchain applications driven by the Internet of Things (IoT) evolution, the developers are still facing a lack of tools and instruments for appropriate and efficient performance evaluation and behavior observation of different blockchain architectures. This paper aims at providing a systematic review of current blockchain evaluation approaches and at identifying the corresponding utilization challenges and limitations. First, we outline the main metrics related to the blockchain evaluation. Second, we propose the blockchain modeling and analysis classification based on the critical literature review. Third, we extend the review with publicly accessible industrial tools. Next, we analyze the selected results for each of the proposed classes and outline the corresponding limitations. Finally, we identify current challenges of the blockchain analysis from the system evaluation perspective, as well as provide future perspectives. publishedVersion

One of the primary functions of millimeter-waveautomotive radar is collision avoidance. This application istypically realized in line-of-sight conditions. However, it does notperform well in situations, when another car suddenly come intoview around the corner of a building. Hence, this paper proposesa radar scheme with a reflector, enabling the detection of anoncoming car in blind corner conditions. First, our ray tracingmodelling results demonstrate the difficulties of straightforwardnon-line-of-sight radar application in such a scenario. Then thepaper considers the installation of a planar reflector, which shouldsolve the issue. This is verified with real-world measurements.The results also indicate that the detection performance issensitive to the around-the-corner car position and orientationof the reflector. Specifically, +/-10 degree deviation varies thesignal-to-noise ratio of more than 20 dB. Thus, the location anddirection of the reflector should be adopted individually for theparticular deployment. acceptedVersion

There is a strong interest in utilizing commercial cellular networks to support unmanned aerial vehicles (UAVs) to send control commands and communicate heavy traffic. Cellular networks are well suited for offering reliable and secure connections to the UAVs as well as facilitating traffic management systems to enhance safe operation. However, for the full-scale integration of UAVs that perform critical and high-risk tasks, more advanced solutions are required to improve wireless connectivity in mobile networks. In this context, integrated access and backhaul (IAB) is an attractive approach for the UAVs to enhance connectivity and traffic forwarding. In this paper, we study a novel approach to dynamic associations based on reinforcement learning at the edge of the network and compare it to alternative association algorithms. Considering the average data rate, our results indicate that the reinforcement learning methods improve the achievable data rate. The optimal parameters of the introduced algorithm are highly sensitive to the donor next generation node base (DgNB) and UAV IAB node densities, and need to be identified beforehand or estimated via a stateful search. However, its performance nearly converges to that of the ideal scheme with a full knowledge of the data rates in dense deployments of DgNBs. acceptedVersion

Industrial automation has created a high demand for private 5G networks, the deployment of which calls for an efficient and reliable solution to ensure strict compliance with the regulatory emission limits. While traditional methods for measuring outdoor interference include collecting real-world data by walking or driving, the use of unmanned aerial vehicles (UAVs) offers an attractive alternative due to their flexible mobility and adaptive altitude. As UAVs perform measurements quickly and semiautomatically, they can potentially assist in near realtime adjustments of the network configuration and fine-tuning its parameters, such as antenna settings and transmit power, as well as help improve indoor connectivity while respecting outdoor emission constraints. This article offers a firsthand tutorial on using aerial 5G emission assessment for interference management in nonpublic networks (NPNs) by reviewing the key challenges of UAV-mounted radio-scanner measurements. Particularly, we (i) outline the challenges of practical assessment of the outdoor interference originating from a local indoor 5G network while discussing regulatory and other related constraints and (ii) address practical methods and tools while summarizing the recent results of our measurement campaign. The reported proof of concept confirms that UAV-based systems represent a promising tool for capturing outdoor interference from private 5G systems., Comment: 7 pages, 4 figures

The prospective millimeter-wave (mmWave) networks are envisioned to heavily utilize relay nodes to improve their performance in certain scenarios. In addition to the stationary mmWave relays already considered by 3GPP as one of the main focuses, the community recently started to explore the use of unmanned aerial vehicle (UAV)-based mmWave relays. These aerial nodes provide greater flexibility in terms of the relay placement in different environments as well as the ability to optimize the deployment height thus maximizing the cell performance. At the same time, the use of UAV-based relays leads to additional deployment complexity and expenditures for the network operators. In this paper, taking into account 3GPP-standardized mmWave-specific propagation, blockage, and resource allocation we compare the capacity gains brought by the static and the UAV-based mmWave relays in different scenarios. For each of the relay types, we investigate both uniform and clustered distribution of human users. The developed mathematical framework and a numerical study reveal that the highest capacity gains when utilizing the UAV-based relays instead of the static ones are observed in clustered deployments (up to 31%), while the performance difference between the UAV-based and the static mmWave relays under a uniform distribution of users is just 3%. acceptedVersion

Wireless traffic produced by modern mobile devices displays high temporal and spatial dynamics as users spontaneously engage in collective applications where a significant portion of generated data remains localized. As a result, conventional service provisioning approaches may no longer be sufficient in beyond fifth generation (B5G) systems. The challenge of increased dynamics on the access networks can be mitigated with moving cells. However, the deployment time of these temporary serving entities may lag behind the service demand lifetime. Another viable solution to offload excessive cellular traffic is to rely upon locally available radio resources offered by user devices via direct mmWave-based mesh interworking. An important challenge in such systems is related to the incentivization of users to partake in collaborative resource sharing. To leverage multi-hop mesh capabilities, we propose the use of emerging blockchain technology that offers cryptographically-strong accounting while maintaining the anonymity of the participants. With system-level evaluations, we demonstrate that the utilization of mobile blockchain methods allows for a non-incremental improvement in the offloading gains. This demonstrates the potential of the outlined proposal for becoming a successful mechanism in the emerging B5G systems. publishedVersion

User equipment mobility is one of the primary challenges for the design of reliable and efficient wireless links over millimeter-wave and terahertz bands. These high-rate communication systems use directional antennas and therefore have to constantly maintain alignment between transmitter and receiver beams. For terahertz links, envisioned to employ radiation patterns of no more than few degrees wide, not only the macro-scale user mobility (human walking, car driving, etc.) but also the micro-scale mobility - spontaneous shakes and rotations of the device - becomes a severe issue. In this paper, we propose a mathematical framework for the first-order analysis of the effects caused by micro-mobility on the capacity and outage in terahertz communications. The performance of terahertz communications is compared with and without micro-mobility illustrating the difference of up to 1 Tbit/s or 75%. In response to this gap, it is finally shown how the negative effects of the micro-mobility can be partially addressed by a proper adjustment of the terahertz antenna arrays and the period of beam realignment procedure., Comment: Accepted to IEEE Transactions on Vehicular Technology on April 9, 2020. Copyright may be transferred without further notice after which this version may become non-available

Almost inevitable climate change and increasing pollution levels around the world are the most significant drivers for the environmental monitoring evolution. Recent activities in the field of wireless sensor networks have made tremendous progress concerning conventional centralized sensor networks known for decades. However, most systems developed today still face challenges while estimating the trade-off between their flexibility and security. In this work, we provide an overview of the environmental monitoring strategies and applications. We conclude that wireless sensor networks of tomorrow would mostly have a distributed nature. Furthermore, we present the results of the developed secure distributed monitoring framework from both hardware and software perspectives. The developed mechanisms provide an ability for sensors to communicate in both infrastructure and mesh modes. The system allows each sensor node to act as a relay, which increases the system failure resistance and improves the scalability. Moreover, we employ an authentication mechanism to ensure the transparent migration of the nodes between different network segments while maintaining a high level of system security. Finally, we report on the real-life deployment results. publishedVersion

To meet the prospective demands of intelligent transportation systems (ITS), the Release 14 (Rel-14) and Rel-15 of the Long Term Evolution (LTE) specifications include solutions for enhanced vehicle-to-everything (V2X) communications. While the technical enablers of Rel-14 are suitable for delivering basic safety messages, Rel-15 supports more demanding ITS services with stringent latency and reliability. Starting in Rel-15 and continuing in Rel-16, the 3GPP was developing a novel radio interface for 5G systems, termed the New Radio (NR), which will enable ultra reliable and low latency communications suitable even for the most demanding ITS applications. In this paper, we overview the new V2X-specific features in Rel-15 and Rel-16. Further, we argue that future V2X and automotive radar systems may reuse common equipment, such as millimeter-wave antenna arrays. We finally discuss the vision of joint vehicular communications and radar sensing as well as characterize unified channel access for millimeter-wave vehicular communications and radar sensing. acceptedVersion

The Internet undergoes a fundamental transformation as billions of connected ”things” surround us and embed themselves into the fabric of our everyday lives. However, this is only the beginning of true convergence between the realm of humans and that of machines, which materializes with the advent of connected machines worn by humans, or wearables. The resulting shift from the Internet of Things to the Internet of Wearable Things (IoWT) brings along a truly personalized user experience by capitalizing on the rich contextual information, which wearables produce more than any other today’s technology. The abundance of personally identifiable information handled by wearables creates an unprecedented risk of its unauthorized exposure by the IoWT devices, which fuels novel privacy challenges. In this paper1, after reviewing the relevant contemporary background, we propose efficient means for the delegation of use applicable to a wide variety of constrained wearable devices, so that to guarantee privacy and integrity of their data. Our efficient solutions facilitate contexts when one would like to offer their personal device for temporary use (delegate it) to another person in a secure and reliable manner. In connection to the proposed protocol suite for the delegation of use, we also review the possible attack surfaces related to advanced wearables. acceptedVersion

As the cellular networks continue to progress between generations, the expectations of 5G systems are planned toward high-capacity communication links that can provide users access to numerous types of applications (e.g., augmented reality and holographic multimedia streaming). The demand for higher bandwidth has led the research community to investigate unexplored frequency spectrums, such as the terahertz band for 5G. However, this particular spectrum is strived with numerous challenges, which includes the need for line-of-sight (LoS) links as reflections will deflect the waves as well as molecular absorption that can affect the signal strength. This is further amplified when a high quality of service has to be maintained over infrastructure that supports mobility, as users (or groups of users) migrate between locations, requiring frequent handover for roaming. In this paper, the concept of mirror-assisted wireless coverage is introduced, where smart antennas are utilized with dielectric mirrors that act as reflectors for the terahertz waves. The objective is to utilize information such as the user's location and to direct the reflective beam toward the highest concentration of users. A multiray model is presented in order to develop the propagation models for both indoor and outdoor scenarios in order to validate the proposed use of the reflectors. An office and a pedestrian-walking scenarios are used for indoor and outdoor scenarios, respectively. The results from the simulation work show an improvement with the usage of mirror-assisted wireless coverage, improving the overall capacity, the received power, the path loss, and the probability of LoS. acceptedVersion

mcMTC is starting to play a central role in the industrial Internet of Things ecosystem and have the potential to create high-revenue businesses, including intelligent transportation systems, energy/ smart grid control, public safety services, and high-end wearable applications. Consequently, in the 5G of wireless networks, mcMTC have imposed a wide range of requirements on the enabling technology, such as low power, high reliability, and low latency connectivity. Recognizing these challenges, the recent and ongoing releases of LTE systems incorporate support for lowcost and enhanced coverage, reduced latency, and high reliability for devices at varying levels of mobility. In this article, we examine the effects of heterogeneous user and device mobility-produced by a mixture of various mobility patterns-on the performance of mcMTC across three representative scenarios within a multi-connectivity 5G network. We establish that the availability of alternative connectivity options, such as D2D links and drone-Assisted access, helps meet the requirements of mcMTC applications in a wide range of scenarios, including industrial automation, vehicular connectivity, and urban communications. In particular, we confirm improvements of up to 40 percent in link availability and reliability with the use of proximate connections on top of the cellular-only baseline. acceptedVersion

The new generation of communication technologies, named 5G, brings along a variety of emerging applications and services from both human and machine perspectives. The growing demand for bandwidth in 5G may therefore lead to massive deficiency in wireless spectrum availability despite its under-utilization in urban areas. The Smart City paradigm assumes a multitude of communicating machines at high density, which requires improved spectrum management flexibility. The novel Licensed Shared Access (LSA) framework that has attracted recent industrial and academic attention may become a feasible solution to leverage such underutilized spectrum more efficiently. This work analyzes the effects of applying LSA in the Smart City context by proposing an appropriate mathematical model. Particularly, we focus on the Vehicle-to-Everything 5G use case where connected devices attempt to distribute their sensed data including occasional video information. The proposed analytical framework allows to capture the probabilities of rare events during such operation by providing with a high level of precision in the resulting performance estimates. publishedVersion

Public protection and disaster relief (PPDR) situations are becoming increasingly common due to the rapid urbanization of our society. Among these, harsh weather conditions and harmful human activity create challenges for reliable operation of mobile communication infrastructures, which calls for immediate action. The wireless networks of today may not be ready to accommodate emergency scenarios as they have not been optimized for PPDR contexts historically. In this work, we first review the important use cases, challenges, and requirements in the context of next-generation mobile networking for PPDR applications. We argue that many emerging services may be supported by the novel communication technology operating in millimeter-wave (mmWave) spectrum. Against this background, we contribute a new analytical model to characterize session continuity and other service-level performance indicators in cases when the communication system is susceptible to sudden intermissions caused by emergency situations. publishedVersion

Machine-Type Communications (MTC) is one of the important use cases of fifth-generation (5G) wireless networks. The ability of networked devices to communicate with each other in a fully automated manner without human interaction is an emerging area wherein both academia and industry are putting significant efforts. One of the aspects of MTC that has been studied in this paper is focused on enabling high-speed long-range communication specifically used in autonomous robotic off-shore operations. For this purpose, a system comprising 3GPP LTE and directional IEEE 802.11 (Wi-Fi) radio links was designed, installed, and tested on an unmanned surface vehicle to enable high-speed bi-directional connectivity. acceptedVersion

Multicasting is widely used in conventional wired and wireless networks as it allows to significantly improve resource utilization in presence of users interested in the same content. However, the support of this type of service in prospective 5G New Radio (NR) systems has received only little attention so far. In this paper, merging the tools of queuing theory and stochastic geometry we develop a model of 5G NR base station (BS) serving a mixture of unicast and multicast traffic. We validate our model against computer simulations using multicast/unicast session drop probabilities and system resource utilization as metrics of interest. Our numerical results illustrate that the presence of multicast type of traffic severely compromises performance of unicast sessions. Furthermore, this effect is amplified when the inter-site distance (ISD) between BSs increases. Thus, in order to satisfy prescribed performance guarantees in terms of unicast and multicast session drop probabilities, explicit resource reservation mechanism at NR BS might be required. acceptedVersion

The capability of smarter networked devices to dynamically select appropriate radio connectivity options is especially important in the emerging millimeter-wave (mmWave) systems to mitigate abrupt link blockage in complex environments. To enrich the levels of diversity, mobile mmWave relays can be employed for improved connection reliability. These are considered by 3GPP for on-demand densification on top of the static mmWave infrastructure. However, performance dynamics of mobile mmWave relaying is not nearly well explored, especially in realistic conditions, such as urban vehicular scenarios. In this paper, we develop a mathematical framework for the performance evaluation of mmWave vehicular relaying in a typical street deployment. We analyze and compare alternative connectivity strategies by quantifying the performance gains made available to smart devices in the presence of mmWave relays. We identify situations where the use of mmWave vehicular relaying is particularly beneficial. Our methodology and results can support further standardization and deployment of mmWave relaying in more intelligent 5G+ "all-mmWave" cellular networks., 6 pages, 8 figures. The paper has been accepted for IEEE GLOBECOM 2019. Copyright may be transferred without notice, after which this version may no longer be accessible

We present the work towards strengthening the security of DNA-sequencing functionality of future bioinformatics systems against bio-computing attacks. Recent research has shown how using common tools, a perpetrator can synthesize biological material, which upon DNA-analysis opens a cyber-backdoor for the perpetrator to hijack control of a computational resource from the DNA-sequencing pipeline. As DNA analysis finds its way into practical everyday applications, the threat of bio-hacking increases. Our wetlab experiments establish that malicious DNA can be synthesized and inserted into E. coli, a common contaminant. Based on that, we propose a new attack, where a hacker to reach the target hides the DNA with malicious code on common surfaces (e.g., lab coat, bench, rubber glove). We demonstrated that the threat of bio-hacking can be mitigated using dedicated input control techniques similar to those used to counter conventional injection attacks. This article proposes to use genetic similarity of biological samples to identify material that has been generated for bio-hacking. We considered freely available genetic data from 506 mammary, lymphocyte and erythrocyte samples that have a bio-hacking code inserted. During the evaluation we were able to detect up to 95% of malicious DNAs confirming suitability of our method.

Miniaturization of implantable devices is an important challenge for future brain-computer interface applications, and in particular for achieving precise neuron stimulation. For stimulation that utilizes light, i.e., optogenetics, the light propagation behavior and interaction at the nanoscale with elements within the neuron is an important factor that needs to be considered when designing the device. This paper analyzes the effect of light behavior for a single neuron stimulation and focuses on the impact from different cell shapes. Based on the Mie scattering theory, the paper analyzes how the shape of the soma and the nucleus contributes to the focusing effect resulting in an intensity increase, which ensures that neurons can assist in transferring light through the tissue toward the target cells. At the same time, this intensity increase can in turn also stimulate neighboring cells leading to interference within the neural circuits. This paper also analyzes the ideal placements of the device with respect to the angle and position within the cortex that can enable axonal biophoton communications, which can contain light within the cell to avoid the interference. acceptedVersion

Since the birth of computer and networks, fuelled by pervasive computing and ubiquitous connectivity, the amount of data stored and transmitted has exponentially grown through the years. Due to this demand, new solutions for storing data are needed, and one promising media is the DNA. This storage solution provides numerous advantages, which includes the ability to store dense information while achieving long-term stability. However, the question as how the data can be retrieved from a DNA-based archive, still remains. In this paper, we aim to address this question by proposing a new storage solution that relies upon molecular communication, and in particular bacterial nanonetworks. Our solution allows digitally encoded information to be stored into non-motile bacteria, which compose an archival architecture of clusters, and to be later retrieved by engineered motile bacteria, whenever reading operations are needed. We conducted extensive simulations, in order to determine the reliability of data retrieval from non-motile storage clusters, placed at different locations. Aiming to assess the feasibility of our solution, we have also conducted wet lab experiments that show how bacteria nanonetworks can effectively retrieve a simple message, such as "Hello World", by conjugation with non-motile bacteria, and finally mobilize towards a final point., 22 pages, 13 figures; removed wrong venue references, reordered bibliography accordingly to ACM guidelines

The papers in this special issue aims at capturing the most relevant theoretical foundations of molecular communications and networking (MCN) established so far, while giving a timely perspective on some emerging technological directions for engineering practical MCN applications. We believe these special issue papers can serve as an essential but complete handbook to approach MC as a research topic, as well as to start contributing to its timely and much needed technological evolution from theoretical exploration to practical implementation.

While the Internet of Things (IoT) has made significant progress along the lines of supporting individual machine-type applications, it is only recently that the importance of people as an integral component of the overall IoT infrastructure has started to be fully recognized. Several powerful concepts have emerged to facilitate this vision, whether involving the human context whenever required or directly impacting user behavior and decisions. As these become the stepping stones to develop the IoT into a novel people-centric utility, this paper outlines a path to materialize this decisive transformation. We begin by reviewing the latest progress in human-aware wireless networking, then classify the attractive human-machine applications and summarize the enabling IoT radio technologies. We continue with a unique system-level performance characterization of a representative urban IoT scenario and quantify the benefits of keeping people in the loop on various levels. Our comprehensive numerical results confirm the significant gains that have been made available with tighter user involvement, and also corroborate the development of efficient incentivization mechanisms, thereby opening the door to future commoditization of the global people-centric IoT utility., Comment: 8 pages, 5 figures. This work has been accepted to IEEE Communications Magazine, 2019

In this paper, we address a problem of 3D directional deafness, which may arise for millimeter-wave (mmWave) devices, e.g., in the contention-based access period of the IEEE 802.11ad/ay protocols. To evaluate the probability of 3D deafness, we develop an analytical framework based on stochastic geometry methods. In particular, we study a minimal feasible set of devices equipped with highly directional antennas with an arbitrary antenna pattern and provide an analytical expression for the distance-dependent 3D directional deafness probability.To abstract away from particular antenna patterns, we propose an analytically tractable model of an antenna pattern that is given by a piece-wise linear function of the beamwidth. Using this tractable equation, we derive a corresponding closed-form lower bound for the deafness probability that serves as an approximation for an arbitrary antenna with the same half-power beamwidth. Finally, we study the effects of antenna settings on the deafness probability and derive a scaling law for its lower values. acceptedVersion

To satisfy the stringent capacity and scalability requirements in the fifth generation (5G) mobile networks, both wireless access and backhaul links are envisioned to exploit millimeter wave (mmWave) spectrum. Here, similar to the design of access links, mmWave backhaul connections must also address many challenges such as multipath propagation and dynamic link blockage, which calls for advanced solutions to improve their reliability. To address these challenges, 3GPP New Radio (NR) technology is considering a flexible and reconfigurable backhaul architecture, which includes dynamic link rerouting to alternative paths. In this paper, we investigate the use of aerial relay nodes carried by e.g., unmanned aerial vehicles (UAVs) to allow for such dynamic routing, while mitigating the impact of occlusions on the terrestrial links. This novel concept requires an understanding of mmWave backhaul dynamics that accounts for: (i) realistic 3D multipath mmWave propagation; (ii) dynamic blockage of mmWave backhaul links; and (iii) heterogeneous mobility of blockers and UAV-based assisting relays. We contribute the required mathematical framework that captures these phenomena to analyze the mmWave backhaul operation in characteristic urban environments. We also utilize this framework for a new assessment of mmWave backhaul performance by studying its spatial and temporal characteristics. We finally quantify the benefits of utilizing UAV assistance for more reliable mmWave backhaul. The numerical results are confirmed with 3GPP-calibrated simulations, while the framework itself can aid in the design of robust UAV-assisted backhaul infrastructures in future 5G mmWave cellular. acceptedVersion

Today, the rapid adoption of mobile social networking is changing how and where humans communicate. As a result, in recent years we have been increasingly moving from physical (e.g., face-to-face) to virtual interaction. However, there is also a new emerging category of social applications that take advantage of both worlds, that is, using virtual interaction to enhance physical interaction. This novel form of networking is enabled by D2D communication between/among the laptops, smartphones, and wearables of persons in proximity of each other. Unfortunately, it has remained limited by the fact that most people are simply not aware of the many potential virtual opportunities in their proximity at any given time. This is a result of the very real digital privacy and security concerns surrounding direct communication between stranger devices. Fortunately, these concerns can be mitigated with the help of a centralized trusted entity, such as a cellular service provider, which can not only authenticate and protect the privacy of devices involved into D2D communication, but also facilitate the discovery of device capabilities and their available content. This article offers an extensive research summary behind this type of cellular-assisted D2D communication, detailing the enabling technology and its implementation, relevant usage scenarios, security challenges, and user experience observations from large-scale deployments. acceptedVersion

In this paper, we provide a shooting and bouncing ray (SBR) based simulation study of mmWave radio propagation at 60 GHz in a typical conference room. The room geometry, material types, and other simulation settings are verified against the results of the measurement campaign at 83 GHz in [15]. Here, we extend the evaluation scenario by randomly scattering several human-sized blockers as well as study the effects of human body blockage models. We demonstrate that multiple knife-edge diffraction (KED) models are capable of providing meaningful results while keeping the simulation duration relatively short. Moreover, we address another important scenario, where transmitters and receivers are located at the same heights and are moving according to a predefined trajectory that corresponds, for example, to device-to-device interactions or inter-user interference. acceptedVersion

One of the most well-known standards for radio frequency identification (RFID), the standard ISO 18000-6C, collects the requirements for RFID readers and tags and regulates respective communication protocols. In particular, the standard introduces the so-called Q-algorithm resolving conflicts in the channel (which occur when several RFID tags respond simultaneously). As of today, a vast amount of existing literature addresses various modifications of the Q-algorithm; however, none of them is known to significantly reduce the average identification time (i.e., the time to identify all proximate tags). In this work, we derive a lower bound for the average identification time in an RFID system. Furthermore, we demonstrate that in case of an error-free channel, the performance of the legacy Q-algorithm is reasonably close to the proposed lower bound; however, for the error-prone environment, this gap may substantially increase, thereby indicating the need for new identification algorithms. acceptedVersion

Utilization of Unmanned Aerial Vehicles (UAVs), also known as “drones”, has a great potential for many emerging applications, such as delivering the connectivity on-demand, providing services for public safety, or recovering after damage to the communication infrastructure. Notably, nearly any application of drones requires a stable link to the ground control center, yet this functionality is commonly added at the last moment in the design, necessitating compact antenna designs. In this work, we propose a novel electrically small antenna element based on the 3D folded loop topology, which could be easily located inside the UAV airframe, yet still delivering good isolation from the drones own noise sources. The complete manufacturing technique along with corresponding simulations/measurements are presented. Measurements and evaluations show that the proposed antenna design is an option to achieve genuinely isotropic radiation in a small size without sacrificing efficiency. acceptedVersion

Part 3: Network Deployment; International audience; Today, one of the emerging trends for the next generation (5G) networks is utilizing higher frequencies in closer premises. As one of the enablers, small cells appear as a cost-effective way to reliably expand network coverage and provide significantly increased capacity for end users. The ultra-high bandwidth available at millimeter (mmWave, 30–300 GHz) and Terahertz (THz, 0.3–3 THz) frequencies can effectively realize short-range wireless access links in small cells. Those technologies could also be utilized for direct communications for users in proximity. At the same time, the performance of mobile wireless systems operating in those frequency bands depends on the availability of line-of-sight (LoS) between communicating entities. In this paper, we estimate the fraction of LoS time for randomly chosen node moving according to different mobility models in a field of N moving blocking nodes for both base station and device-to-device (D2D) connectivity scenarios. We also provide an extension to the case of a random number of moving blockers. The reported results can be further used to assess the amount of traffic offloaded to other technologies having greater coverage, e.g., LTE.

Today, the number of interconnected Internet of Things (IoT) devices is growing tremendously followed by an increase in the density of cellular base stations. This trend has an adverse effect on the power efficiency of communication, since each new infrastructure node requires a significant amount of energy. Numerous enablers are already in place to offload the scarce cellular spectrum, thus allowing utilization of more energy-efficient short-range radio technologies for user content dissemination, such as moving relay stations and network-assisted direct connectivity. In this work, we contribute a new mathematical framework aimed at analyzing the impact of network offloading on the probabilistic characteristics related to the quality of service and thus helping relieve the energy burden on infrastructure network deployments. publishedVersion

Owing to a steadily increasing demand for efficient spectrum utilization as part of the fifth-generation (5G) cellular concept, it becomes crucial to revise the existing radio spectrum management techniques and provide more flexible solutions for the corresponding challenges. A new wave of spectrum policy reforms can thus be envisaged by producing a paradigm shift from static to dynamic orchestration of shared resources. The emerging Licensed Shared Access (LSA) regulatory framework enables flexible spectrum sharing between a limited number of users that access the same frequency bands, while guaranteeing better interference mitigation. In this work, an advanced user satisfaction-aware spectrum management strategy for dynamic LSA management in 5G networks is proposed to balance both the connected user satisfaction and the Mobile Network Operator (MNO) resource utilization. The approach is based on the MNO decision policy that combines both pricing and rejection rules in the implemented processes. Our study offers a classification built over several types of users, different corresponding attributes, and a number of operator's decision scenarios. Our investigations are built on Criteria Based Resource Management (CBRM) framework, which has been specifically designed to provide results for dynamic LSA management in 5G mobile networks. To verify the proposed model, the results (spectrum utilization, estimated secondary user price for the future connection, and user selection methodology in case of user rejection process) are validated numerically as we yield important conclusions on the applicability of our approach, which may offer valuable guidelines for efficient radio spectrum management in highly-dynamic and heterogeneous 5G environments. Owing to a steadily increasing demand for efficient spectrum utilization as part of the fifth-generation (5G) cellular concept, it becomes crucial to revise the existing radio spectrum management techniques and provide more flexible solutions for the corresponding challenges. A new wave of spectrum policy reforms can thus be envisaged by producing a paradigm shift from static to dynamic orchestration of shared resources. The emerging Licensed Shared Access (LSA) regulatory framework enables flexible spectrum sharing between a limited number of users that access the same frequency bands, while guaranteeing better interference mitigation. In this work, an advanced user satisfaction-aware spectrum management strategy for dynamic LSA management in 5G networks is proposed to balance both the connected user satisfaction and the Mobile Network Operator (MNO) resource utilization. The approach is based on the MNO decision policy that combines both pricing and rejection rules in the implemented processes. Our study offers a classification built over several types of users, different corresponding attributes, and a number of operator's decision scenarios. Our investigations are built on Criteria Based Resource Management (CBRM) framework, which has been specifically designed to provide results for dynamic LSA management in 5G mobile networks. To verify the proposed model, the results (spectrum utilization, estimated secondary user price for the future connection, and user selection methodology in case of user rejection process) are validated numerically as we yield important conclusions on the applicability of our approach, which may offer valuable guidelines for efficient radio spectrum management in highly-dynamic and heterogeneous 5G environments.

In today’s landscape of utility management, the contribution of Internet of Things (IoT) to smart grids has acquired extensive potential. IoT paves a way to virtually control every smart device in almost every domain of society. Contrariwise, the smart grid networks attracted the attention of the universal research community. The idea of merging IoT with smart grid together demonstrates enormous potential. In this work, we investigate the suitability of Wireless M-BUS communication protocol for possible adoption in remote metering by evaluating possible communication range and system stability in future housing estate represented by university campus made of steel and concrete – this living area acts well when it comes to wireless transmissions. Measurements were executed by means of constructed prototype sensor devices utilizing the frequency 868 MHz which is the frequency by far the most used by WM-BUS devices in Europe. acceptedVersion

Due to explosive growth in the mobile data demand, millimeter-wave (mmWave) spectrum is to become one of the key enablers for the next-generation 5G wireless. Accurate characterization of mmWave channels has crucial implications on 5G network planning — as compared to more conventional frequency bands — due to a higher impact that surrounding objects have on the radio propagation. In this work, we contribute mmWave channel measurements and compare our obtained results across several metrics of interests, mindful of previously standardized models. The proposed analysis is conducted for a typical mmWave system deployment operating at 15 and 60 GHz. The evaluation studies a difference between the obtained results for the two frequency bands considered, as well as verifies their predictability when utilizing modern modeling considerations. acceptedVersion

Despite several decades of intense developments, the consumer IoT market still falls short of delivering its original economic promise. Its current condition - featuring fragmentation among the key players and their siloed business models - is comprehensively reviewed in this article. We specifically address the stagnant home automation sector, which suffers from a lack of interoperability between the existing IoT products. Aiming to unblock its sustainable growth, we systematically report on the development of a next-generation SyMPHOnY platform that becomes the key asset for telecom operators willing to understand the true needs of their customers. Supported by a recent user experience study, our SyMPHOnY platform pragmatically integrates a residential gateway module with a multitude of smart home solutions to provide valuable information and services based on consumers' household automation data. It thus offers significant promise to bridge the existing divide between IoT technology availability and its slow market adoption. acceptedVersion