Hasil untuk "Cellular telephone services industry. Wireless telephone industry"

Lalit Chettri, R. Bera

Recently, wireless technologies have been growing actively all around the world. In the context of wireless technology, fifth-generation (5G) technology has become a most challenging and interesting topic in wireless research. This article provides an overview of the Internet of Things (IoT) in 5G wireless systems. IoT in the 5G system will be a game changer in the future generation. It will open a door for new wireless architecture and smart services. Recent cellular network LTE (4G) will not be sufficient and efficient to meet the demands of multiple device connectivity and high data rate, more bandwidth, low-latency quality of service (QoS), and low interference. To address these challenges, we consider 5G as the most promising technology. We provide a detailed overview of challenges and vision of various communication industries in 5G IoT systems. The different layers in 5G IoT systems are discussed in detail. This article provides a comprehensive review on emerging and enabling technologies related to the 5G system that enables IoT. We consider the technology drivers for 5G wireless technology, such as 5G new radio (NR), multiple-input–multiple-output antenna with the beamformation technology, mm-wave commutation technology, heterogeneous networks (HetNets), the role of augmented reality (AR) in IoT, which are discussed in detail. We also provide a review on low-power wide-area networks (LPWANs), security challenges, and its control measure in the 5G IoT scenario. This article introduces the role of AR in the 5G IoT scenario. This article also discusses the research gaps and future directions. The focus is also on application areas of IoT in 5G systems. We, therefore, outline some of the important research directions in 5G IoT.

K. Letaief, Wei Chen, Yuanming Shi et al.

The recent upsurge of diversified mobile applications, especially those supported by AI, is spurring heated discussions on the future evolution of wireless communications. While 5G is being deployed around the world, efforts from industry and academia have started to look beyond 5G and conceptualize 6G. We envision 6G to undergo an unprecedented transformation that will make it substantially different from the previous generations of wireless cellular systems. In particular, 6G will go beyond mobile Internet and will be required to support ubiquitous AI services from the core to the end devices of the network. Meanwhile, AI will play a critical role in designing and optimizing 6G architectures, protocols, and operations. In this article, we discuss potential technologies for 6G to enable mobile AI applications, as well as AI-enabled methodologies for 6G network design and optimization. Key trends in the evolution to 6G will also be discussed.

Kaibai Chen, Min Gao

The millimeter wave detector has been widely applied in short-range detection systems. However, it can be easily disturbed by the ultra-wideband electromagnetic pulse (UWB EMP). In this paper, we proposed a simplified model to investigate the coupling laws of UWB EMP to the millimeter wave detector. With the help of finite integration technology (FIT), the coupling process can be visualized, and the most sensitive pose and the coupling path are analyzed. The irradiation tests are carried out to verify the simulation results. The results show that the shielding effectiveness (SE) of the detector in the vertical state is the worst, and the UWB EMP enters the detector mainly through the circular opening. Under the irradiation of UWB EMP, the detector shows three phenomena: interruptions, constant false alarms, and damage. The interruptions can be recovered by power reset, while the constant false alarms and damage are irreversible effects. The results can be employed to reinforce the electromagnetic compatibility (EMC) of the millimeter wave detector. With the increasing use of short-range detection systems, the EMC of existing products must be improved.

Liping Hu, Canming Yao, Jian Huang et al.

Sufficient synthetic aperture radar (SAR) data is the key element in achieving excellent target recognition performance for most deep learning algorithms. It is unrealistic to obtain sufficient SAR data from the actual measurements, so SAR simulation based on electromagnetic scattering modeling has become an effective way to obtain sufficient samples. Simulated and measured SAR images are nonhomologous data. Due to the fact that the target geometric model of SAR simulation is not inevitably consistent with the real object, the SAR sensor model in SAR simulation may be different from the actual sensor, the background environment of the object is also inevitably different from that of SAR simulation, the error of electromagnetic modeling method itself, and so on. There are inevitable differences between the simulated and measured SAR images, which will affect the recognition performance. To address this problem, an SAR simulation method based on a high-frequency asymptotic technique and a discrete ray tracing technique is proposed in this paper to obtain SAR simulation images of ground vehicle targets. Next, various convolutional neural networks (CNNs) and AugMix data augmentation methods are proposed to train only on simulated data, and then target recognition on MSTAR measured data is performed. The experiments show that all the CNNs can achieve incredible recognition performance on the nonhomologous SAR data, and the RegNetX-3.2GF achieves state-of-the-art performance, up to 84.81%.

Genling Huang, Yanlong Zhu

This paper considers target localization using time delay (TD) and angle of arrival (AOA) measurements in distributed multiple-input multiple-output (MIMO) radar. Aiming at the problem that the localization performance of existing algorithms degrades sharply in the presence of impulsive noise, we propose a novel localization algorithm based on ℓp-norm minimization and iteratively reweighted least squares (IRLS). Firstly, the TD and AOA measurement equations are established in the presence of zero-mean symmetric α-stable noise; then, the localization problem is transformed to a ℓp-norm minimization problem by linearizing the measurement equations; and finally, the ℓp-norm minimization problem is solved using IRLS by which the target position estimate is obtained, and the optimal choice of norm order p is deduced. Moreover, the Cramér–Rao bound (CRB) for target position estimation in impulsive noise is also derived, generalizing the Gaussian CRB. Simulation results demonstrate that the proposed algorithm outperforms existing algorithms in terms of localization accuracy and robustness in impulsive noise.

Yuan Ren, Xuewei Zhang, G. Lu

With the tremendous increase of heterogeneous Internet of Things (IoT) devices and the different service requirements of these IoT applications, machine-type communication (MTC) has attracted considerable attention from both industry and academia. Owing to the prominent advantages of supporting pervasive connectivity and wide area coverage, the cellular network is advocated as the potential wireless solution to realize IoT deployment for MTC, and this creative network paradigm is called the cellular IoT (C-IoT). In this paper, we propose the three-layer structured C-IoT architecture for MTC and review the challenges for deploying green C-IoT. Then, effective strategies for realizing green C-IoT are presented, including the energy efficient and energy harvesting schemes. We put forward several strategies to make the C-IoT run in an energy-saving manner, such as efficient random access and barring mechanisms, self-adapting machine learning predictions, scheduling optimization, resource allocation, fog computing, and group-oriented transmission. As for the energy harvesting schemes, the ambient and dedicated energy harvesting strategies are investigated. Afterwards, we give a detailed case study, which shows the effectiveness of reducing power consumption for the proposed layered C-IoT architecture. Additionally, for real-time and non-real-time applications, the power consumption of different on-off states for MTC devices is discussed.

Brahim Fady, Abdelwahed Tribak, Jaouad Terhzaz et al.

This paper presents a novel low-cost integrated multiband antenna design customized for smartwatch applications and wearable devices. The design consists in using a broadband planar patch antenna with circular microstrip lines and a miniaturized feeding-point with a structure of 30 × 30 × 1.6 mm3, and it is easy to deploy inside the smartwatch and cost-effective for the wearable device industry. The parametric study and final dimensions of the design and the measured results of the reflection and radiation pattern are discussed. The antenna with maximum gain up to 6.6 dBi and S11 up to −22 dB exhibits excellent performance for all the frequencies required in wearable systems such as 1.9 GHz, 2.3 GHz, 2.4 GHz, 2.6 GHz, 5.2 GHz, and 5.8 GHz. We drew a comparison between similar research and this work in terms of antenna performance. Furthermore, we investigate the specific absorption rate (SAR) performance of the antenna for the smartwatch application, using both human hand wrist multilayer and SAM head mouth models. The SAR results in different positions for all the frequencies are compared to the Federal Communication Commission (FCC) standards.

César Deschamps-Berger, Simon Gascoin, Etienne Berthier et al.

Yuchen Xie, Zhengrong Li, Feiqiang Chen et al.

The antenna array technology, especially the spaced-time array processing (STAP), is one of the effective methods used in Global Navigation Satellite System (GNSS) receivers to refrain the power of jamming and enhance the performance of receivers in the circumstance of interference. However, biases induced to the receiver because of many reasons, including characteristic of antennas, front-end channel electronics, and space-time filtering, are extremely harmful to the high precise positioning of receivers. Although plenty of works have been done to calibrate the antenna and to mitigate these biases, achieving a good performance of antijamming, high accuracy, and low complexity at the same time still remains challenging. Different from existing works, this paper leverages the characteristic of GNSS signal’s Doppler frequency in STAP, which is proven to remain unbiased to solve the problem, even when the nonideal antennas are used and the interference circumstance changes. Since the integration of frequency is carrier phase, the unbiased Doppler frequency leads to an accurate estimation of carrier phase which can be used to calibrate the antenna array without extra apparatus or complicating algorithms. Therefore, a simple Doppler-aid strategy may be developed in the future to solve the difficulty of STAP bias mitigation.

Zihao Fu, Tianliang Zhang, You Lan et al.

A novel quarter-mode substrate integrated waveguide miniaturized cavity-backed antenna loading Minkowski fractal gap is presented in this paper. Firstly, the resonant frequency of the rectangular substrate integrated waveguide resonator is reduced by etching the fractal gap in the resonator to achieve miniaturization. In addition, because of the symmetry of electric field distribution in second and third order resonant modes, the cavity can be segmented into a quarter-mode and the other order resonance modes with asymmetric electric field distribution can be suppressed according to the cavity model theory. Hence, the cavity size is further reduced. The dimension of designed antenna is 0.26λ0×0.26λ0 (λ0 is the wavelength in free space; in this paper, the corresponding wavelength is 3.6 GHz). Moreover, the orthogonal polarization of the proposed antenna in two frequency bands is achieved because the electric field is orthogonal in second and third order resonant modes. This dual-frequency orthogonal polarization characteristic enables antenna to communicate in two working bands and has good channel isolation. The simulated and measured results are consistent. The antenna gain is 4.67dBi and 3.4dBi, respectively, at 3.7GHz and 4.6GHz.

Michael Karrenbauer, A. Weinand, Lianghai Ji et al.

Tzu-Ling Chiu, Laure Huitema, Olivier Pajona et al.

A compact and multiband dielectric resonator antenna (DRA) designed for LTE automotive solutions is presented in this paper. The proposed MIMO system is located on the vehicle rooftop within a limited space of 120 mm × 70 mm × 65 mm. To cover all the LTE standard frequency bands used around the world, the antenna is matched around 790 MHz–860 MHz, 1700 MHz–2200 MHz, and 2500 MHz–2700 MHz frequency bands with a ∣S11∣ lower than −6 dB while presenting a minimum total efficiency of 50% with a maximum realized gain better than 1 dB on all these frequency bands. The DRA is then mounted and measured on a real vehicle rooftop in order to see its performances in real operation conditions. Finally, to improve both the quality and reliability of the wireless link, two DRAs are placed within a small area to reconfigure their radiation patterns on each frequency band. Measured performances, which are in good agreement with the simulated results, are used to validate if the antenna design is suitable for LTE MIMO systems to be integrated on an automotive. The MIMO system is evaluated using the envelope correlation coefficient (ECC), and the obtained value for the proposed antenna is lower than 0.25.

Sungwoo Lee, Jong Min Lee, Keum Cheol Hwang et al.

Hybrid robust optimization that combines a genetical swarm optimization (GSO) scheme with an orthogonal array (OA) is proposed to design an antenna robust to the tolerances arising during the fabrication process of the antenna in this paper. An inverted-F antenna with a metal frame serves as an example to explain the procedure of the proposed method. GSO is adapted to determine the design variables of the antenna, which operates on the GSM850 band (824–894 MHz). The robustness of the antenna is evaluated through a noise test using the OA. The robustness of the optimized antenna is improved by approximately 61.3% relative to that of a conventional antenna. Conventional and optimized antennas are fabricated and measured to validate the experimental results.

Hayeon Kim, Haengseon Lee, Jeonghoon Cho et al.

A beam expanding radome for 76.5 GHz automotive radar antennas is presented whose inner surface is engraved with corrugations. The radar used for blind spot detection (BSD) requires a very wide beam width to ensure longer time for tracking out-of-sight objects. It is found that the corrugations modulate the phase velocities of the waves along the surface, which increases beam width in the far field. In addition, defects in the corrugation increase beam width even further. The presented structure satisfies the beam width requirement while keeping a low profile.

Xavier Lucie, Sylvie Durrieu, Anne Jolly et al.

Le renouveau de la photogrammétrie et le développement de moyens aéroportés légers tels que les drones permettent de nouvelles applications dans le domaine de l'aménagement et la gestion forestière. L'estimation de variables forestières se fait dans le cadre de processus longs et fastidieux sur le terrain. Dans l'idée d'automatiser l'extraction de variables dendrométriques, nous mettons en place une méthodologie pour générer les modèles numériques de surfaces (MNS) par photogrammétrie multi-vues les plus précis possibles compte-tenu des limites imposées par les algorithmes de calcul. Nous utilisons pour ce faire la suite photogrammétrique libre de l'IGN MicMac. Notre zone d'étude se situe dans la forêt domaniale du Ventouret (région PACA) qui est une forêt mixte de moyenne montagne. Pour qualifier la précision de ces MNS, nous disposons de relevés dendrométriques sur des placettes d'analyse de 700 m² représentatives des peuplements les plus fréquents à l'échelle de la forêt. Ces zones ont été survolées par un drone multi-rotors équipé d'un appareil photo numérique à focale fixe. Les clichés ont une résolution spatiale de 2,5 cm contre 25 cm pour les prises de vues standardisées de l'IGN. Afin d'étudier l'impact de la résolution sur la qualité des MNS générés, nous dégradons la résolution des prises de vues du drone jusqu'à obtenir un pixel terrain d'une quarantaine de centimètres. Nous comparons ensuite les altitudes de chaque MNS avec des pointés stéréoscopiques de référence réalisés manuellement sur les prises de vues originales. En soustrayant à chaque MNS un modèle numérique de terrain (MNT) LiDAR, nous calculons ensuite un modèle de hauteur de couvert (MHC). L'étude de la distribution des hauteurs sur chaque placette et d'un modèle statistique de hauteur dominante (H0) nous permettent de conclure sur l'intérêt de l'approche photogrammétrique et de déterminer des résolutions spatiales optimales pour appuyer le travail des gestionnaires et aménagistes forestiers.

Longzhu Cai, Huan Xu, Daping Chu

A wave interference filtering section that consists of three stubs of different lengths, each with an individual stopband of its own central frequency, is reported here for the design of band-stop filters (BSFs) with ultra-wide and sharp stopbands as well as large attenuation characteristics. The superposition of the individual stopbands provides the coverage over an ultra-wide frequency range. Equations and guidelines are presented for the application of a new wave interference technique to adjust the rejection level and width of its stopband. Based on that, an electrically tunable ultra-wide stopband BSF using a liquid crystal (LC) material for ultra-wideband (UWB) applications is designed. Careful treatment of the bent stubs, including impedance matching of the main microstrip line and bent stubs together with that of the SMA connectors and impedance adaptors, was carried out for the compactness and minimum insertion and reflection losses. The experimental results of the fabricated device agree very well with that of the simulation. The centre rejection frequency as measured can be tuned between 4.434 and 4.814 GHz when a biased voltage of 0–20 Vrms is used. The 3 dB and 25 dB stopband bandwidths were 4.86 GHz and 2.51 GHz, respectively, which are larger than that of other recently reported LC based tunable BSFs.

Madeleine Solenhill, A. Grotta, E. Pasquali et al.

Background Lifestyle-related health problems are an important health concern in the transport service industry. Web- and telephone-based interventions could be suitable for this target group requiring tailored approaches. Objective To evaluate the effect of tailored Web-based health feedback and optional telephone coaching to improve lifestyle factors (body mass index—BMI, dietary intake, physical activity, stress, sleep, tobacco and alcohol consumption, disease history, self-perceived health, and motivation to change health habits), in comparison to no health feedback or telephone coaching. Methods Overall, 3,876 employees in the Swedish transport services were emailed a Web-based questionnaire. They were randomized into: control group (group A, 498 of 1238 answered, 40.23%), or intervention Web (group B, 482 of 1305 answered, 36.93%), or intervention Web + telephone (group C, 493 of 1333 answered, 36.98%). All groups received an identical questionnaire, only the interventions differed. Group B received tailored Web-based health feedback, and group C received tailored Web-based health feedback + optional telephone coaching if the participants’ reported health habits did not meet the national guidelines, or if they expressed motivation to change health habits. The Web-based feedback was fully automated. Telephone coaching was performed by trained health counselors. Nine months later, all participants received a follow-up questionnaire and intervention Web + telephone. Descriptive statistics, the chi-square test, analysis of variance, and generalized estimating equation (GEE) models were used. Results Overall, 981 of 1473 (66.60%) employees participated at baseline (men: 66.7%, mean age: 44 years, mean BMI: 26.4 kg/m2) and follow-up. No significant differences were found in reported health habits between the 3 groups over time. However, significant changes were found in motivation to change. The intervention groups reported higher motivation to improve dietary habits (144 of 301 participants, 47.8%, and 165 of 324 participants, 50.9%, for groups B and C, respectively) and physical activity habits (181 of 301 participants, 60.1%, and 207 of 324 participants, 63.9%, for B and C, respectively) compared with the control group A (122 of 356 participants, 34.3%, for diet and 177 of 356 participants, 49.7%, for physical activity). At follow-up, the intervention groups had significantly decreased motivation (group B: P<.001 for change in diet; P<.001 for change in physical activity; group C: P=.007 for change in diet; P<.001 for change in physical activity), whereas the control group reported significantly increased motivation to change diet and physical activity (P<.001 for change in diet; P<.001 for change in physical activity). Conclusion Tailored Web-based health feedback and the offering of optional telephone coaching did not have a positive health effect on employees in the transport services. However, our findings suggest an increased short-term motivation to change health behaviors related to diet and physical activity among those receiving tailored Web-based health feedback.

Nesrine Chehata, Karim Ghariani, Arnaud Le Bris et al.

Les pratiques et les arrangements spatiaux des parcelles agricoles ont un fort impact sur les flux d'eau dans les paysages cultivés . Afin de surveiller les paysages à grande échelle, il ya un fort besoin de délimitation automatique ou semi-automatique des parcelles agricoles. Cet article montre la contribution des images satellitaires à très haute résolution spatiales, telles que Pléiades, pour délimiter le parcellaire agricole de manière automatique . On propose une approche originale utilisant une classification binaire supervisée des limites. Une approche d'apprentissage actif est proposée afin d'adapter le modèle de classifieur au contexte local permettant ainsi la délimitation parcellaire à grande échelle. Le classifieur des Forêts Aléatoires est utilisé pour la classification et la sélection des attributs . Le concept de marge non supervisée est utilisé comme mesure d'incertitude dans l'algorithme d'apprentissage actif. En outre, un étiquetage automatique des pixels incertains est proposé en utilisant une approche hybride qui combinant une approche région et le concept de marge. Des résultats satisfaisants sont obtenus sur une image Pléiades. Différentes stratégies d'apprentissage sont comparées et discutées . Pour un cas d'étude opérationnel, un modèle global ou bien un modèle simple enrichi peuvent être utilisés en fonction des données de terrain disponibles.

Taghrid Mazloum, Alain Sibille

A few years ago, physical layer based techniques have started to be considered as a way to improve security in wireless communications. A well known problem is the management of ciphering keys, both regarding the generation and distribution of these keys. A way to alleviate such difficulties is to use a common source of randomness for the legitimate terminals, not accessible to an eavesdropper. This is the case of the fading propagation channel, when exact or approximate reciprocity applies. Although this principle has been known for long, not so many works have evaluated the effect of radio channel properties in practical environments on the degree of randomness of the generated keys. To this end, we here investigate indoor radio channel measurements in different environments and settings at either 2.4625 GHz or 5.4 GHz band, of particular interest for WIFI related standards. Key bits are extracted by quantizing the complex channel coefficients and their randomness is evaluated using the NIST test suite. We then look at the impact of the carrier frequency, the channel variability in the space, time, and frequency degrees of freedom used to construct a long secret key, in relation to the nature of the radio environment such as the LOS/NLOS character.

Yann Kerr, Philippe Waldteufel, Jean-Pierre Wigneron et al.

La mission SMOS (Soil moisture and Ocean Salinity) a été lancée avec succès le 2 novembre 2009. Cette mission menée par l'ESA (Agence Spatiale Europénne) est dédiée à la mesure de l'humidité superficielle des sols sur les continents (avec une précision recherchée de 0,04m3/m3) et la salinité des océans (objectif 0.1psu). Ces deux quantités géophysiques sont très importantes car elle contrôle le budget énergétique à l'interface sol-atmosphère. Leur connaissance à l'échelle globale est utile pour les recherches sur le climat et la météorologie, en particulier pour les modèles de prévision numérique. Elles ont aussi un très grand potentiel un très grand nombre d'application, comme par exemple pour le suivi des ouragans ou la gestion des ressources en eau. Les six premiers mois ont été dédiés à la recette en vol qui a permis de vérifier le satellite le segment sol et l'étalonnage. Cette phase s'est achevée avec succès en mai 2010 et SMOS fonctionne de façon opérationnelle depuis, fournissant de données à la communauté internationale. Les performances de l'instrument sont globalement conformes aux spécifications. Cependant, les interférences radio sont présentes au-dessus de l'Europe, du Moyen-Orient et de l'Asie. Ces émissions parasites dans la bande protégée perturbent la mesure de façon significative. La génération des produits de niveau 2 et 3 est une activité en cours avec des améliorations régulières de sorties.