bluuebunny/crossref_metadata_2025 huggingface dataset:
Prevalence Mapping
Authors: Wakefield Jon
Published: May 2020

As data availability escalates, there has been a corresponding increase in the production of maps displaying the prevalence of a large range of health and demographic outcomes – an endeavor that has been labeled
prevalence mapping
. In this article, we distinguish between modeling at the areal level, that is
small area estimation
(SAE), and at the point level, which is referred to as
model‐based geostatistics
(MBG). Often, maps are produced for low‐ and middle‐income countries based on household surveys which have complex designs. Bayesian smoothing models are convenient for both SAE and MBG, and computation is no longer a major problem for most prevalence mapping endeavors. To illustrate the two approaches, we form estimates of measles vaccination rates for Nigeria, using data from the 2013 Demographic Health Survey (DHS). While prevalence maps are clearly of use in many contexts, we encourage care in their production and advocate respecting the survey design in analysis, and summarization at a granularity which is both meaningful and sufficiently precise so as to avoid being misleading. Prevalence mapping remains in its infancy, and research is required in a number of key areas, in particular to appropriately characterize uncertainty and validate models.
Statistics and Terrorism: Insights into Lethality of Terrorism Through Bayesian Modeling
Authors: Python Andre , Brandsch Jürgen , Illian Janine B. , Jones‐Todd Charlotte M. , Blangiardo Marta
Published: May 2020

The increasingly growing availability of large disaggregated datasets on terrorism along with advances made in the fields of statistics and data science has allowed scholars to better understand the patterns of non‐state terrorism at fine spatial and temporal scales. While acknowledging important limitations that stem from the analysis of data on terrorism, we present a Bayesian hierarchical modeling approach that contributes to explaining fine‐scale patterns of the lethality of worldwide non‐state terrorism.
C
haloner,
K
athryn
M
.
Authors: Cavanaugh Joseph E.
Published: May 2020

Kathryn Mary Chaloner was an accomplished British statistician and professor. This article summarizes her life, career, contributions, and achievements.
Variograms for Functional Data
Authors: Elayouty Amira
Published: May 2020

In several applications, data are collected as functions observed at a set of locations of a region, inducing spatially correlated functional data. The analysis of such data is performed by adapting and extending the spatial statistical tools for functional data. The variogram is a very popular measure for describing the spatial covariance structure of a spatial process. This article focuses on the extension of variograms for functional data and provides a review for the computation and estimation of different types of functional variograms.
Pilot‐Assisted Channel Estimation
Authors: Jiménez Juan C. Estrada , García M. Julia Fernández‐Getino , Méndez‐Romero Diego
Published: May 2020

Channel estimation is a challenging task in coherent wireless communications systems since it highly impacts data detection performance. To acquire channel state information, known pilot symbols are commonly inserted in the signal to be transmitted. Then, at the receiver, the channel is estimated comparing the received signal with the pilot symbols. Pilot symbol assisted modulation (PSAM) is a channel estimation technique commonly used, where known symbols are transmitted over dedicated resources and they are used as reference signals. PSAM spends valuable bandwidth to transmit the pilot signal in order to obtain low channel estimation error. Currently, 5G technologies have been using different versions of PSAM to estimate the channel and different patterns have been tested to improve the communication performance.
Modulations with Low Peak‐to‐Average Power Ratio
Authors: Banelli Paolo , Baruffa Giuseppe , Buzzi Stefano , Colavolpe Giulio , Foggi Tommaso , Rugini Luca , Ugolini Alessandro
Published: May 2020

We compare the main multicarrier modulation formats when employed over channels with nonlinear amplification. Using a general and unified discrete‐time model that encompasses orthogonal frequency division multiplexing (OFDM) and its most popular alternatives, we perform a comparison using the achievable spectral efficiency, computed in the presence of specific channel and amplifier models, as performance indicator. This provides a more precise quantitative measure of the effect that the different peak‐to‐average power ratio (PAPR) of these modulations has on the ultimate performance. In the numerical results, different LTE channel models are considered. We show that, depending on the considered channel, the winning modulation format is not always the same. In any case, modulation formats other than OFDM exhibit the best performance.
Polar Codes
Authors: Bioglio Valerio
Published: May 2020

Polar codes have been recently adopted as control channel coding scheme for upcoming 5G NR framework. Their mathematical foundations lay on the polarization effect, whose discovery in late 2000s represented a real breakthrough for the information theory community. In order to be included in an industrial standard, polar codes went through a refinement process that permitted 3GPP to improve their error correcting performance while keeping a limited decoding latency. The results of these efforts is a synthesis of all known advancements in the field and truly represents the state‐of‐the‐art of polar coding knowledge today.
Random Access for Cellular Systems
Authors: Mahmood Nurul H. , López Onel A. , Clazzer Federico , Munari Andrea
Published: May 2020

Wireless connectivity has become a ubiquitous part of our everyday life. Owing to its very nature, the wireless channel is a shared medium, where simultaneous transmissions from neighboring transceivers operating in the same frequency can interfere with each other. Access to the shared wireless medium needs then to be strictly regulated to ensure efficient utilization of the scarce spectral resources. The admission control process to handle the access of multiple coexisting transmitters over the same wireless channel is typically initiated relying on random access‐related policies, having users send information (control or data packets) in an uncoordinated fashion. The design goal for random access techniques differs in different systems, mainly depending on the catered service. The current fourth‐generation long‐term evolution system is primarily designed to serve cellular broadband users, and hence its random access procedures have been designed to support contention from a limited number of users, with the aim to negotiate and exclusively allocate channel resources to them. Conversely, emerging fifth‐generation new radio is designed to allow the coexistence of multiservice communication. Similarly, systems that are exclusively designed to support machine‐type communication targeting Internet of Things applications, such as SigFox, LoRA, and NB‐IoT, have designed their random access mechanism to serve a large number of low power, low‐cost devices with small payload and intermittent transmissions. On the other hand, indoor wireless local area networks like Wi‐Fi are designed for a decentralized access of several users. Finally, random access techniques like nonorthogonal multiple access and grant‐free transmissions have emerged to support machine‐type communication encompassing both its massive and critical aspects, in line with the increasing importance of such critical services in emerging systems.
Multiuser Scheduling
Authors: de la Fuente Alejandro
Published: May 2020

Scheduling and resource allocation (SRA) strategies play a crucial role in the emerging fifth‐generation (5G) systems based on massive multiple‐input multiple‐output (MaMIMO) transmissions. The set of resources to allocate is increased, adding to the time, frequency, modulation, and coding resources, the spatial dimension introduced by MaMIMO. These spatial resources are provided by precoding schemes based on the channel state information knowledge at the transmitter side (CSIT). The joint optimization of all the input variables together with the quality of service (QoS) requirements established by the upper layers results in a complex cross‐layer optimization problem. Different metric criteria for SRA algorithms are studied in the literature. MaMIMO SRA is based on CSIT knowledge to select a feasible set of users to allocate the resources of a scheduling interval. This article provides a detailed view of the required mechanisms to understand the SRA process in the emerging 5G systems. To conclude this article, some challenging solutions regarding the utilization of heterogeneous scenarios, MaMIMO transmissions, millimeter wave (mmWave) frequencies, and artificial intelligence are presented.
High‐Density Channels
Authors: Cai Xuesong , Zhang Chao , Fan Wei
Published: May 2020

In the future, fifth‐generation communications system (5G) is expected to provide reasonable mobile broadband experience to high‐density users in stadium, gym, shopping mall, etc. As the fundamental limitation is attributed to the propagation environments, it is essential to understand profoundly the high‐density channels, say, the propagation channel in the environments where the user density could be very high. In this article, seven different environments are considered. The targeted environments include stadium (or gymnasium), shopping mall, airport, hall, street canyon, indoor (or indoor office), and crowded area. The propagation investigations in the literature for the seven environments are reviewed in terms of channel sounding, parameter estimation, channel characterization and modeling, etc. The review of the high‐density channel facilitates the “great service in a crowd” defined in 5G.
Indoor Office Channels
Authors: Kürner Thomas
Published: May 2020

Indoor Ultra‐high Broadband Access with high traffic densities inside office buildings brings the indoor office channel into the focus. Whereas in the past decade the indoor office channel in the UHF range was subject to intense channel modeling and channel characterization approaches, with the advent of 5G mmWave channels are raising attention. After introducing the key characteristics and main differences of propagation in the UHF and mmWave frequency range, respectively, the first part of the article indoor office channels describes empirical, semiempirical, and deterministic path loss models for both the UHF and the mmWave frequency range. A detailed description is provided for the semiempirical Motley–Keenan model and its various extensions. These models allow a narrowband channel characterization and provide the large‐scale characteristics. These models are relevant for the planning and optimization of radio access points as well as an enabler for system‐level simulations. The second part introduces channel models capable of providing temporal and spatial channel characteristics. This includes approaches to derive models for double‐directional channels, which are required to simulate and investigate multi‐antenna systems and beam‐forming algorithms especially in the mmWave range. Furthermore, an approach to describe the impact of human blockage is provided. As exemplary approaches, the extended Saleh–Valenzuela model and the TGad channel model are described.
MassiveMIMOChannels
Authors: Gunnarsson Sara , Van der Perre Liesbet , Tufvesson Fredrik
Published: May 2020

Massive MIMO (multiple‐input multiple‐output) is a fundamental technology in 5G systems. The characteristics of the radio channel experienced when operating with large antenna arrays differ from those of conventional multiple antenna systems. Hence, it is important to specifically characterize and model the underlying propagation channels with large antenna systems in mind. The channel models need to be realistic and accurate, but of low complexity, in order to be used to develop and assess the performance of future systems in a good way. This article gives an overview of state‐of‐the‐art of massive MIMO channels and related models. First, some fundamentals of massive MIMO propagation, including a comparison between micro‐wave and mm‐wave massive MIMO as well as the influence of user terminals, are provided. Then, channel characteristics that have been shown in measurements to be important in massive MIMO channels are presented. These include spherical wavefronts, nonstationarity, 3D propagation, and polarization effects. Further on, some channel‐dependent characteristics, which are experienced in massive MIMO systems, are in focus. In this article, we outline user separability and channel hardening, as an effect of favorable propagation conditions. Different channel modeling approaches are discussed, including the independent and identically distributed (i.i.d.) complex Gaussian channel model, correlation‐based channel models like the Kronecker and Weichselberger channel models, geometry‐based reference models, geometry‐based stochastic channel models (GSCMs), ray‐tracing and map‐based approaches. A brief overview of recently developed channel models, targeting massive MIMO channels, is also provided. Lastly, we discuss opportunities and challenges related to massive MIMO channels and modeling.
3D MIMOChannels
Authors: Zhang Ruonan , Jiang Yi , Zhai Daosen
Published: May 2020

The fifth‐generation (5G) mobile communication systems require high spectrum efficiency due to the explosive increase of data traffic and green networking requirement. The demand for higher spectrum and energy efficiency has driven system designers to exploit more spatial degrees of both the elevation and azimuth domains through the use of large‐scale antenna systems with two or three‐dimensional (3D) array structures. The performance of full‐dimensional multiple‐input‐multiple‐output (FD‐MIMO) depends critically on both the space–time transmission schemes and 3D channel propagation characteristics. Therefore, it is important to understand and describe the 3D spatial propagation of signals in multipath radio channels. This article aims to provide a comprehensive introduction to the fundamental concept and approaches characterizing and modeling the 3D spatial channels. We first present the bi‐directional space‐time scattering models of multipath channels and the polarized multipath components (MPCs). We then briefly introduce the development of 3D channel modeling and the main projects and standards in the industrial community. Finally, we summarize and discuss the current 3D channel models based on extensive field measurement for various cellular network scenarios, such as outdoor, indoor, outdoor‐to‐indoor (O2I), and vehicular communication scenarios.
MassiveMIMOAntenna Designs
Authors: Gao Yue , Su Wei , Zhang Xiuyin , Cao Yunfei
Published: May 2020

Massive multiple‐input multiple‐output (MIMO) has attracted significant interests in both academia and industry with recent development of signal processing and information theory. It has been considered as one of the most promising technologies for 5G communication systems. The large‐scale antenna array for base stations naturally becomes the key to deploy the Massive MIMO technologies in addition to baseband signal processing. In this article, we shall start from the characteristics of conventional MIMO antennas to the areas of Massive arrays. Several notable previous works have been presented in this article as examples to show the idea.
5GWireless Testbeds
Authors: Zhang Peize , Yi Cheng , Wang Haiming
Published: May 2020

Fifth‐generation (5G) mobile communication systems are being rolled out in the real world, bringing higher frequencies, more complicated transmission schemes, and denser networks. To ensure the successful operation of 5G, the evaluation of the performance of several promising technologies requires rigorous field trialing and validation. To that end, the 5G wireless testbed design based on reconfigurable hardware and open‐source software is discussed in detail from the perspectives of the physical layer and higher levels. Meanwhile, there are some new considerations regarding the actual system placement, such as the mechanical design and network architectures. Based on these observations, the state‐of‐the‐art 5G testbeds operating at sub‐6 GHz and the millimeter‐wave band are reviewed, with a focus on multiuser massive MIMO systems.
Small Cell Network Modeling and Analysis
Authors: Yang Howard H. , Quek Tony Q.S.
Published: May 2020

Small cell networks are deemed one of the key solutions for next‐generation (5G) wireless networks. In such networks, along with the spatial densification of access points, temporal traffic can also vary largely from cell to cell. To this end, a complete understanding of the impact from spatial and temporal aspects is thus essential for network operators to adequately advance the deployment of small cell networks. In this article, based on stochastic geometry and queuing theory, we develop a mathematical framework that captures the interplay between the spatial location of small access points (SAPs), which determines the magnitude of mutual interference, and their temporal traffic dynamic. We derive a tractable expression for the signal‐to‐interference‐plus‐noise ratio (SINR) distribution, as well as the mean delay distributions under two different scheduling policies, i.e. the random scheduling and round robin. We also verify the accuracy of our mathematical analysis via simulations. Based on our analysis, we find a number of useful guidelines for the deployment of small cell networks.
Radio Resource Management in Small Cell Networks
Authors: Wang Li‐Chun , Chao Yung‐Sheng
Published: May 2020

Ultra‐dense small cell (UDSC) network will play a key role to cope with the capacity issue for 5G cellular mobile systems and beyond because future broadband mobile applications require high‐speed transmission and low latency. Nevertheless, deploying small cell deployment will need to face the challenges of severe interference and excessive energy consumption in very dynamic environments. To address these issues, in this article we introduce a data‐driven resource management (DDRM) framework combined with power control, channel rearrangement, and dynamic antenna clustering (DAC). In particular, an unsupervised learning affinity propagation clustering is applied to UDSC to identify cluster heads, i.e. the cell causing most serious interference to its neighboring cochannel cells. Then, these cluster heads will lower its transmission power. We call this learning‐based interference management approach as affinity propagation power control (APPC). We show that DDRM with APPC can improve energy efficiency and reduce interference for UDSC, while taking account of cell switching on/off, transmission power adjustment, and traffic loads simultaneously.
Energy‐AwareD2DCommunications
Authors: Feng Daquan , Huang Xiaoli , Long Litai , Qian Gongbin , Tang Jianhua , Cao Yue
Published: May 2020

Device‐to‐device (D2D) communications, which enable proximity users to communicate directly without passing through BS, have been considered as one of the key techniques in the future 5G networks. By taking advantage of the physical proximity, D2D communications can significantly enhance the quality of experience (QoE) of users and increase resource utilization. Meanwhile, due to the ever‐increasing power consumption of information and communication technology (ICT) industry and the slow progress in battery technology of the smart devices, energy efficiency has been considered as a key performance indicator for the 5G networks. Thus, energy‐efficient D2D communications design has attracted considerable attention from both the industrial and academic communities. There have been plenty of discussions on this issue, for instance, (i) energy‐efficient D2D transmission technologies including efficient power control, mode selection, cross‐layer optimization, and energy harvesting; (ii) novel D2D‐based energy‐saving network deployment including D2D relay cooperative communications and D2D‐aided heterogeneous networks; and (iii) D2D multiple‐input and multiple‐output (MIMO) transmission. In this article, we provide an extensive overview of these technologies and present the state of the art of each aspect. In addition, we summarize the main findings of the discussed techniques and also identify some open research problems.
Edge/Fog Computing Networks
Authors: Chen Zhi , Li Lingxiang , Siew Marie , Quek Tony Q.S.
Published: May 2020

As a main driver of 5G, the future mobile network is going to create a hyper‐connected Internet of Everything (IoE) world which requires the network to be scalable, versatile, and energy smart. The convergence of communication and computing is a promising solution of IoE while the introduction of fog/edge computing makes this possible in the future mobile networks. This article provides a comprehensive survey of the fog/edge‐computing‐enabled mobile network. Specifically, the motivation of introducing fog/edge computing, the standardization of fog/edge computing in 5G, and the mobile communication network architecture with fog/edge computing are reviewed. The challenges such as the scalability and extreme heterogeneity of resource management in IoE, and the advantages of using fog/edge‐based architecture, are also discussed. Under the fog/edge‐computing‐driven mobile communication network architecture, a distributed resource allocation mechanism based on economics is presented. The economics models and analysis study the underlying, and possibly conflicting objectives and incentives of various stakeholders, with pricing solutions providing a way for the optimization of objectives like social welfare, profit, or fairness. As such, it can be a potential powerful tool in solving the aforementioned challenges. While pricing for resource allocation has a vast existing literature, the analysis and schemes cannot be implemented directly due to the unique characteristics of 5G cloud‐fog/edge networks, hence providing a vast scope for potential research. In light of this, we finally outline some unique characteristics to consider when applying economics to aid resource allocation in 5G cloud‐fog/edge networks.
Business Models of Network Slicing
Authors: Kukliński Sławomir , Tomaszewski Lechosław
Published: May 2020

The development of network softwarization technologies, which leads to network slicing concept, will cause the significant disruption of the current telecommunications sector. Its significance is still underestimated. New roles are expected to appear in the ecosystem, and the mutual relations will be established dynamically. In this article, we have made an attempt to show how network slicing can impact business models of telecommunication network operators. The traditional models of fixed/mobile operators have been described. For reference, the cloud delivery models have been shown. Then the approaches of telecom industry alliances and standard developing organizations are presented, which are conservative and simple evolution of the existing business models. Finally, the comprehensive future business model of network slicing is presented, which is based on widely accepted network slicing concepts. In the concept, the software dimension of network slicing has been emphasized, especially the significant role of brokers that can provide infrastructure brokering, service brokering, or even slice template brokering. The implementation of the proposed approach requires some changes in the Management and Orchestration (MANO) framework to unleash the full technoeconomical potential of network slicing.
Radio Access Network Slicing System
Authors: Schmidt Robert , Nikaein Navid
Published: May 2020

Network slicing is one of the key enablers to provide the required flexibility for the envisioned service‐oriented 5G. We introduce a descriptor, a triple consisting of resources, processing, and state, as a means to describe base stations (BSs) and the embedded slices alike through a unifying description. Second, we propose a RAN slicing system, composed of the RAN runtime execution environment and accompanying controller based on this descriptor. This includes design and performance details of the employed system. Finally, we elaborate on the aspects of RAN slicing such as the radio resources, the processing chain of a slice, and its state.
On Common Spectrum and Active Infrastructure Sharing in Cloud Radio Access Networks
Authors: Boulos Karen , Khawam Kinda , Helou Melhem El , Ibrahim Marc , Martin Steven , Sawaya Hadi
Published: May 2020

Common spectrum and active infrastructure sharing is promising to improve Quality of Service (QoS), without significant increase in Capital Expenditures (CAPEX) and Operational Expenditures (OPEX). Through sharing their spectral resources and active network components (e.g. antenna elements, switches, and backhaul equipment), Mobile Network Operators (MNOs) improve network coverage, capacity, and power savings. In this article, we propose two different approaches for multi‐MNO resource sharing in Cloud‐Radio Access Network (C‐RAN) architecture. As multisite resources are centrally managed, multi‐MNO resource sharing and statistical multiplexing further improve network coverage, capacity, and power savings in C‐RAN. In the first approach, spectrum sharing aims to enhance spectral efficiency through interference mitigation. In the second approach, spectrum sharing aims to increase capacity through multi‐MNO Carrier Aggregation (CA). Moreover, we evaluate these two approaches for different network load conditions over a real case topology, and highlight the benefits of sharing spectrum and active infrastructure in C‐RAN.
Security in Network Slicing
Authors: Porambage Pawani , Liyanage Madhusanka
Published: May 2020

Security is a paramount property in network slicing (NS) as the concept itself is a source of numerous security issues. Among these, slice isolation is the most prominent security requirement in NS. However, since NS supports heterogeneous platforms, exploits more shared functions, and the slicing components can be implemented in firmware, ensuring a common level of security for all applications will be tricky. Although many works have been recently published on implementing NS technology in the fifth generation wireless networks, security in NS still not a thoroughly discovered area. In this article, we intend to investigate the security implications on NS technology and the potential research areas in the related fields.
Mode Selection in Cellular UnderlayD2D
Authors: Zhong Chen , Gursoy Mustafa C. , Velipasalar Senem
Published: May 2020

Device‐to‐device (D2D) communication underlaid with cellular networks is a paradigm proposed to enhance the performance of cellular networks. The underlay D2D mode is especially helpful in improving the utilization of the scarce cellular spectrum and has been extensively studied in the literature. While effectively providing higher spectral efficiency, underlaid D2D communication with spectrum reuse can also cause nonnegligible interference that can lead to degradation in cellular performance. Hence, interference mitigation is a critical consideration in cellular underlay D2D communications. In this article, we provide a survey on mode selection in cellular underlay D2D communications and detail the performance improvements along with interference management strategies.
D2D Physical‐Layer Design
Authors: Wei Chun‐Yi
Published: May 2020

The device‐to‐device (D2D) communication technology is one of the most significant evolutionary development of the LTE system. It introduces the new defined physical‐layer sidelink channel for the direct transmission between terminal devices, apart from the traditional base station‐assisted data transmission. The service and business opportunities motivated by the D2D communication technique are rapidly growing.

In Rel‐12 of LTE system, the development of D2D is initiated by supporting the public‐safety application and proximity‐based service for commercial use. In Rel‐14, LTE has the ambition of supporting vehicular communication through the sidelink channel. It becomes one of the essential services and applications of sidelink communication technology. The sidelink technology has also been rapidly evolved with the new radio (NR) framework of 5G defined in Rel‐15. Atop of 5G NR technology, the standard of NR vehicle‐to‐everything (V2X) is under the normative work of the Rel‐16 LTE standardization.

In this article, we introduce the fundamental physical‐layer design of D2D communication standardized for the LTE system. Additionally, we provide our views on the challenges and opportunities of NR sidelink in the physical layer. The low‐altitude unmanned aircraft vehicle (UAV) is another potential application that will benefit from the sidelink communication technology. Along with the evolution of the next‐generation mobile technology, the sidelink will play a more vital role and introduce more business and research opportunities than before.
Multicast Protocols forD2D
Authors: Bhardwaj Ajay , Agnihotri Samar
Published: May 2020

Supporting ever‐increasing number of mobile users with data‐hungry applications, running on battery‐limited devices, is a daunting challenge for the telecommunication community. Device‐to‐device (D2D) communication, which allows physically proximate mobile users to directly communicate with each other by reusing the spectrum, without going through the base station, holds promise to help us tackle this challenge. In a cellular network, D2D communication offers opportunities for spectrum reuse and spatial diversity that may lead to enhanced coverage, higher throughput, and robust communication in the network. Further, for applications such as weather forecasting and live streaming, which may require the same chunks of data distributed to geographically proximate users, D2D multicasting may provide better utilization of network resources compared to D2D unicast or the base station‐based multicast, such as LTE eMBMS. However, extensive deployment of D2D multicast in a network may introduce various issues, such as severe co‐channel interference due to spectrum reuse, underutilization of spectrum, and rapid battery depletion of the multicasting D2D nodes due to higher transmit power to mitigate co‐channel interference and facilitating data‐relaying. Therefore, this article discusses some of the challenges in supporting D2D multicast communication in cellular networks. It then surveys various existing approaches to address these challenges, which along with some future research directions may help us develop practical D2D multicast protocols for cellular networks.
Network Coding forD2D
Authors: Li Yue , Cai Lin
Published: May 2020

For cellular downlink transmissions, we propose an approach leveraging cooperative device‐to‐device (D2D) communications and network coding (NC), which can substantially reduce the cellular resource consumption and the total energy consumption. In the proposed approach, the base station generates and broadcasts linear combinations based on the packets requested by different user equipments (UEs) until at least one UE can recover all the original packets, called mature UE. Then, a selected mature UE broadcasts new linear combinations based on the recovered original packets to neighbors via D2D until all UEs can decode their packets. A semi‐centralized cooperative control method is proposed for cellular uplink transmissions, where UE relays are randomly selected according to a certain density decided by the base station. Two specific cooperative approaches, i.e. the random UE relay approach and the NC approach, are proposed for D2D communications.
D2Dwith Energy Harvesting Capabilities
Authors: Chang Ronald Y.
Published: May 2020

Device‐to‐device (D2D) communication is envisioned as a key enabling technology for fifth‐generation (5G) wireless systems and the Internet of Things (IoT). D2D promises increased resource utilization, throughput, and coverage, and decreased delays and power consumption, by offloading traffic from the centralized infrastructure to autonomous direct device‐to‐device transmissions. With the rise of D2D and IoT, which comprise typically small, battery‐powered devices, it is essential to consider the energy efficiency and sustainability of future D2D networks. Energy harvesting (EH) has emerged as a promising green and sustainable energy solution for D2D and IoT. EH technologies represent harnessing energy from ambient renewable energy sources and converting the harvested environmental energy into usable electrical energy via wireless power transfer (WPT) technologies. Among various renewable sources, radio frequency (RF) signals are more reliable and allow for simultaneous wireless information and power transfer (SWIPT), and therefore are of particular interest. EH‐aided D2D communication raises new resource allocation and interference management considerations nonexistent in conventional D2D communication, since cochannel interference, a main performance‐limiting factor in underlaid D2D networks, could be converted into useful energy. Issues such as power allocation/control, beamforming design, time allocation, and spectrum allocation, with the consideration of EH‐empowered D2D devices, have been investigated for EH‐aided D2D networks.
D2DinUAVNetworks
Authors: Trivedi Aditya , Pawar Praveen
Published: May 2020

The integration of device‐to‐device (D2D) communications technology plays an important role in improving system performance for unmanned aerial vehicle (UAV)‐supported networks. In this article, we present benefits and possible future challenges in the utilization of D2D communication with UAVs in wireless networks. The current status is drawn for the D2D communications underlaying cellular networks with UAVs as aerial base stations. Moreover, various fundamental problems are uncovered, and significant issues in the development of UAV networks are also highlighted.

It concludes that the UAV with D2D communication plays a vital role for system capacity and coverage extension with reliable communication in the wireless networks.
5GS Network Slicing
Authors: Casati Alessio
Published: May 2020

Network Slicing is one of the main innovations cited as a benefit of the 5G system (5GS). While conceptually intuitive, implementing Network Slicing in a way that is economical to run and providing incremental revenue generation opportunities requires an in‐depth understanding of its workings. Further, an overall ecosystem effort must ensure the industry adopts best practices to simplify peering between operators and translation of customer use cases into compelling communication services offerings. This paper provides exposure to both 5GS Network Slicing technical details and exposes the main ecosystem challenges that need to be overcome for successful adoption.
SDN‐Based Session and Mobility Management in5GNetworks
Authors: Kaloxylos Alexandros , Spapis Panagiotis , Moscholios Ioannis
Published: May 2020

The analysis performed in this article is a concise proposal on how SDN solutions can be integrated into 5G mobile networks in order to address key cellular network challenges related to session and mobility management. Initially, we present the key characteristics of SDN and how session and mobility management are performed in this type of networks. Then we present how session and mobility management are performed in 5G mobile networks and what are the potential drawbacks of the conventional designs that could lead to excessive signaling and/or delays. Then, we analyze how the mobility management can be enhanced using SDN in ultra‐dense 5G networks, where current solutions will lead to an explosion of the signaling cost. Furthermore, we analyze how handling of local traffic in 5G mobile networks using SDN will reduce the delays and the core network signaling in specific 5G use cases, that of fog computing and V2X communications.
Seamless Indoor/Outdoor Coverage in5G
Authors: Imran Muhammad A. , Turkmen Aysenur , Ozturk Metin , Nadas João , Abbasi Qammer H.
Published: May 2020

Densely deployment of the small cells in 5G networks will bring high‐quality service to the end users as well as will solve the small footprint coverage problem of millimeter‐waves. The increase in the number of small cells will require self‐organized systems to enable the seamless transaction between heterogeneous network environment. Therefore, a survey‐style study on self‐organized seamless coverage in 5G, covering millimeter‐wave features and its indoor and outdoor coverage along with some machine learning techniques are presented in this article.
An Overview of Machine Learning Applied in WirelessUAVNetworks
Authors: Klaine Paulo V. , Souza Richard D. , Zhang Lei , Imran Muhammad
Published: May 2020

Unmanned aerial vehicles (UAVs) are expected to be deployed in future cellular networks in a wide range of scenarios, such as to rapidly restore network service after natural disasters, to provide extra coverage to wireless networks, or to deliver content to remote locations. However, despite their benefits, several issues are still present in UAV networks, such as how to determine their optimal positioning or trajectory, how to perform resource management or manage interference to name a few. One way of solving these issues is by analyzing data coming from the network to learn patterns and react accordingly. These solutions, rely on machine learning algorithms, and by integrating them in UAV networks, more autonomous and flexible systems can be achieved. Based on that, several recent works have explored this concept of integrating UAVs and machine learning algorithms in wireless networks. As such, this article presents an overview machine learning applications in aerial wireless networks. Before reviewing these works, an introduction to key machine learning concepts and categories is performed. After that, a literature review of current state‐of‐the‐art research is presented, followed by a discussion on future research directions and paradigms in UAV‐aided wireless networks. Lastly, conclusions are drawn.
Security for Handover andD2DCommunication in5G HetNets
Authors: Ozhelvaci Alican , Ma Maode
Published: May 2020

The Third Generation Partnership Project (3GPP) leads the standards for the next‐generation mobile communication technology which is under the development. This is called 5G wireless mobile networks that has become the paradigm to bring not only solutions for the rising demand for huge data traffic but also massively connected devices, such as internet of things (IoT) and new services. Also, 5G is expected to supply the fastest, most reliable network access to support huge data traffic and massively connected nodes with low latency and high throughput. There are different new technologies that are emerging to tackle requirements of the 5G networks, such as Network Function Virtualization (NFV), Software‐Defined Networking (SDN), and Heterogeneous Network (HetNet). However, the new case scenarios and new system architecture of 5G HetNets are vulnerable against various attacks; therefore, we now have the unique opportunity to identify research directions for the next generation based on existing security and privacy issues as well as already proposed security mechanisms or solutions. Hence, this article presents a comprehensive survey on security issues that are happening in handover authentication and device‐to‐device (D2D) communication on 5G HetNets. The article begins with the explanation of the requirements of 5G mobile networks and gives the overall architecture of the 5G and the security architecture of the 5G systems. Subsequently, we focus security features and techniques for handover authentication and D2D group communication which incur a big security challenge in 5G HetNets. Finally, the future directions of handover and D2D security are discussed for 5G HetNets.
Safety of the Zoster Vaccine Recombinant Adjuvanted in Rheumatoid Arthritis and Other Systemic Rheumatic Disease Patients: A Single Center's Experience With 400 Patients
Authors: Stevens Emma , Weinblatt Michael E. , Massarotti Elena , Griffin Frances , Emani Srinivas , Desai Sonali
Published: May 2020

Objective

Patients with rheumatoid arthritis (RA) and other systemic rheumatic diseases (SRDs) are at increased risk of developing herpes zoster (HZ). Zoster recombinant adjuvanted (ZRA) is a recombinant vaccine approved by the Food and Drug Administration in 2018. Concern has been raised that the ZRA may trigger disease flares in rheumatology patients who are immunocompromised. We investigated the impact of the ZRA vaccine in patients with RA and SRD and measured the incidence of flares and side effects.

Methods

A flare was defined as occurring within 12 weeks of vaccine administration by either 1) documentation of RA flare in office notes, telephone encounter, or patient portal communication or 2) new or increased dose of corticosteroids.

Results

We identified 403 patients (239 patients with RA and 164 patients with SRD) who received the ZRA vaccine from February 1, 2018, to February 1, 2019. We measured a 6.7% (n = 27) incidence of flare. Side effects occurred in 12.7% (n = 51) of patients. All flares and side effects were regarded as mild. Three cases of HZ were reported as occurring 2, 10, and 11 months after the vaccination.

Conclusion

In 403 patients who received the ZRA vaccine, the incidence of disease flares was 7% or less and that of side effects was 13% or less, both of which are less than the incidence rates observed in the pivotal trials.
Heaviest drinkers still drinking during lockdown: UK research
Authors: Knopf Alison
Published: May 2020

Lockdown due to the COVID‐19 pandemic doesn't necessarily result in an across‐the‐board increase in alcohol consumption, according to research commissioned by Alcohol Change UK and released last month. The study found that 21% of adults who drink alcohol are drinking more often since the March 23 lockdown began in England, but that 35% reduced their frequency of consumption or stopped drinking altogether. Of those surveyed, 6% of previous drinkers chose to stop drinking altogether during lockdown. The study, a representative survey of more than 2,000 people, extrapolates to 8.6 million adults in the United Kingdom drinking more frequently since lockdown, while 14 million are drinking less often or have stopped drinking entirely. In addition, many people are seeking help based on visits to the “Get help now” section of Alcohol Change UK's website increasing 355% between March 23 and April 13, compared to the same period last year.
Synthesis of Nanostructured TiFe Hydrogen Storage Material by Mechanical Alloying via High‐Pressure Torsion
Authors: Gómez Edgar Ignacio López , Edalati Kaveh , Antiqueira Flávio José , Coimbrão Diego Davi , Zepon Guilherme , Leiva Daniel Rodrigo , Ishikawa Tomaz Toshimi , Cubero-Sesin Jorge M. , Botta Walter José
Published: May 2020

TiFe as a room‐temperature hydrogen storage material is usually synthesized by ingot casting in the coarse‐grained form, but the ingot needs a thermal activation treatment for hydrogen absorption. Herein, nanograined TiFe is synthesized from the titanium and iron powders by severe plastic deformation (SPD) via the high‐pressure torsion (HPT). The phase transformation to the TiFe intermetallic is confirmed by X‐ray diffraction, hardness measurement, scanning/transmission electron microscopy, and automatic crystal orientation and phase mappings (ASTAR device). It is shown that the HPT‐synthesized TiFe can store hydrogen at room temperature with a reasonable kinetics, but it still needs an activation treatment. A comparison between the current results and those achieved on high activity of HPT‐processed TiFe ingot suggests that a combination of ingot casting and SPD processing is more effective than synthesis by SPD to overcome the activation problem of TiFe.
Binder Jetting 3D Printing of Titanium Aluminides Based Materials: A Feasibility Study
Authors: Yadav Pinku , Fu Zongwen , Knorr Moritz , Travitzky Nahum
Published: May 2020

This study offers the ability to fabricate nearly dense titanium aluminides‐based structures using a hybrid method that encompasses binder jetting 3D printing (3DP) of Ti–6Al–4V followed by pressureless ex situ infiltration with Al. Microstructure characterization and phase analysis are performed by scanning electron microscopy equipped with energy dispersive spectroscopy and X‐ray diffraction, respectively. The microstructure of the samples fabricated by means of pressureless ex situ infiltration at different temperatures and with various durations is studied and discussed. The nearly dense titanium aluminides‐based composites shows a Young's modulus of ≈145 GPa, a compressive strength of ≈1.4 GPa and a bending strength of ≈483 MPa. To demonstrate technological capability of this hybrid approach, complex near‐net‐shaped objects are fabricated.
Pore Chemistry of Metal–Organic Frameworks
Authors: Ji Zhe , Wang Haoze , Canossa Stefano , Wuttke Stefan , Yaghi Omar M.
Published: May 2020

The pores in metal–organic frameworks (MOFs) can be functionalized by placing chemical entities along the backbone and within the backbone. This chemistry is enabled by the architectural, thermal, and chemical robustness of the frameworks and the ability to characterize them by many diffraction and spectroscopic techniques. The pore chemistry of MOFs is articulated in terms of site isolation, coupling, and cooperation and relate that to their functions in guest recognition, catalysis, ion and electron transport, energy transfer, pore‐dynamic modulation, and interface construction. It is envisioned that the ultimate control of pore chemistry requires arranging functionalities into defined sequences and developing techniques for reading and writing such sequences within the pores.
Li‐CO2 Batteries Efficiently Working at Ultra‐Low Temperatures
Authors: Li Jiaxin , Wang Lie , Zhao Yang , Li Shangyu , Fu Xuemei , Wang Bingjie , Peng Huisheng
Published: May 2020

Lithium‐carbon dioxide (Li‐CO2) batteries are considered promising energy‐storage systems in extreme environments with ultra‐high CO2 concentrations, such as Mars with 96% CO2 in the atmosphere, due to their potentially high specific energy densities. However, besides having ultra‐high CO2 concentration, another vital but seemingly overlooked fact lies in that Mars is an extremely cold planet with an average temperature of approximately −60 °C. The existing Li‐CO2 batteries could work at room temperature or higher, but they will face severe performance degradation or even a complete failure once the ambient temperature falls below 0 °C. Herein, ultra‐low‐temperature Li‐CO2 batteries are demonstrated by designing 1,3‐dioxolane‐based electrolyte and iridium‐based cathode, which show both a high deep discharge capacity of 8976 mAh g−1 and a long lifespan of 150 cycles (1500 h) with a fixed 500 mAh g−1 capacity per cycle at −60 °C. The easy‐to‐decompose discharge products in small size on the cathode and the suppressed parasitic reactions both in the electrolyte and on the Li anode at low temperatures together contribute to the above high electrochemical performances.