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

Gabin Bourlon, Etienne Berthier, Jesús Revuelto et al.

La résolution de 30 cm offerte par les satellites Pléiades Neo représente un gain d’un facteur deux par rapport à leurs prédécesseurs, les Pléiades HR. Combinée avec des capacités stéréoscopiques, elle permet de construire des modèles numériques de terrain (MNTs) métriques pour caractériser finement les reliefs, en particulier pour les petits glaciers, comme ceux des Pyrénées. Dans cette étude, nous évaluons la précision des MNTs déduits d’images Pléiades Neo sur les glaciers de l’Aneto, d’Ossoue et du Monte Perdido en les comparant à des MNTs acquis par drone et aux couvertures Lidar nationales. Nous montrons que les MNTs déduits avec le corrélateur More Global Matching (MGM) sont plus précis que d’autres corrélateurs. Nous soulignons également la capacité des MNTs Pléiades Neo à restituer des détails fins de la morphologie glaciaire comme les moulins sur le glacier d’Ossoue, beaucoup plus difficiles à caractériser avec Pléiades HR.

Mohamed Elhefnawy, Kyoung-Hun Kim, Wang-Sang Lee

In this paper, the proposed wideband compact planar antenna is realized by incorporating multiple curved transmission lines along with the interdigital capacitor (IDC) and the electric inductor–capacitor (ELC) resonator. Furthermore, this antenna implements an asymmetric coplanar waveguide (ACPW) via-less structure. A prototype of the proposed antenna has been fabricated with a compact size of 0.33λ0×0.26λ0 at the lower operating frequency of 2.3 GHz. The obtained measured results indicate a wide bandwidth that can cover the frequency band from 2.3 GHz to 4.11 GHz, corresponding to a −10 dB fractional bandwidth of 56.47%.

Shiqi Zong, Chaoqun Jiao, Jiangong Zhang et al.

Electromagnetic scattering from UHV transmission towers is a major factor affecting the safety and stability of the surrounding antenna signal system. In this paper, the electromagnetic scattering effect of ±800 kV UHV DC transmission tower on the medium-wave antenna is investigated based on the characteristic mode theory (CMT). The simulation model of the tower and antenna is established, and the mode selection is carried out according to the percentage of the contribution of the characteristic mode to the total electromagnetic scattering. The effects of electromagnetic scattering under three conditions, namely, the number of towers, the distance between towers and antennas, and different frequencies, are investigated separately. The simulation results show that as the number of towers increases from 1 to 3, it leads to an increase in the electromagnetic scattering impact by about 49.5%. The shape distortion of the antenna’s directional map becomes more pronounced and is accompanied by the extension with the direction of the power line. The distance between the tower and the antenna is shortened from 500 m to 125 m, resulting in the growth of the influence of electromagnetic scattering by about 36.4%, and the directional gain of the antenna increases along the direction of the transmission line. As the frequency increases from 600 kHz to 1400 kHz, it leads to the rise of electromagnetic scattering effect of about 32.7% and the antenna directional map becomes more complicated. The research results will provide technical support for developing protective measures against electromagnetic scattering from UHV DC transmission towers to medium-wave antennas.

Deepa Thangarasu, Sandeep Kumar Palaniswamy, Rama Rao Thipparaju

Recent reconfigurable technological advancements for wireless communication systems provide various global solutions. This research work presents a quad port multipolarized switchable multiple input multiple output (MIMO) antenna for sub 6 GHz applications. It covers the frequency range from 3.1 to 5.1 GHz, including the 5G NR band n78 (3.3 to 3.8 GHz) and 5G NR band n79 (4.4 to 5 GHz). The proposed antenna comprises four offset-fed monopole antenna elements with an overall dimension of 60 mm × 65 mm. To achieve circular polarization (CP), a parasitic meandering resonator is integrated with antenna elements using four PIN diodes. The polarization diversity is obtained by controlling the bias states of four PIN diodes. The radiating element −1/−3 offers left hand circular polarization (LHCP), while element −2/−4 procures right hand circular polarization (RHCP) when all diodes are ON. Consequently, the proposed antenna provides linear polarization (LP) under reverse bias conditions. Moreover, the designed antenna acquires a wide axial ratio bandwidth (ARBW) of 36.1%. In addition, the developed MIMO antenna exhibits isolation greater than 15 dB using the common ground plane, and the obtained ECC is less than 0.13. The prototype is fabricated, and the simulated responses are in good correlation with the measured results.

Xiaoping Wu, Zihao Li, Zhixi Liang et al.

The alternating direction implicit parabolic equation (ADI-PE) method and the Crank–Nicolson parabolic equation (CN-PE) method have been widely used for solving the 3D parabolic equation (3D-PE) in radio wave propagation. The ADI-PE method is more computationally efficient than the CN-PE method. The accuracy of the ADI-PE method is improved by the higher-order Mitchell–Fairweather (MF)-ADI method. This paper presents an iterative high-accuracy (IHA)-ADI method for the 3D parabolic equation. A derivation of the proposed method is presented. The convergence and stability of the proposed method are estimated. Several numerical examples are considered to illustrate the advantages of the proposed method. The results of error analysis and a comparative study show that the proposed method is unconditionally stable and computationally efficient. The proposed method is more numerically accurate than the MF-ADI method.

Qi Guo, Yubin Lan, Xiaoling Deng et al.

In this article, the finite difference parabolic equation (FDPE) method is presented to calculate the propagation loss (PL) for electromagnetic waves (EWs) in the forest environment. The FDPE method is more efficient and convenient than the empirical models and has more advantages on compatibility and accuracy for long-range EWs prediction. The Debye–Cole dual dispersion model is used to simulate the effective permittivity of vegetation. The results of the FDPE model are compared with those of the advanced refractive effects prediction system and measurement results, and a good agreement is observed. Research found that PL for EWs varies with the effective permittivity. Also, the effective permittivity is a function of radio frequency, weight moisture content, and volume content of vegetation. Thus, it is necessary to establish a statistical model to determine some relations between the PL and plant biophysical parameters. The polynomial fitting method is adopted to process a large amount of PL data for obtaining a linear function. Then, the volume content and moisture content of vegetation can be determined according to the polynomial fitting function. It provides a novel and efficient method for forestry remote telemetry, which is specifically suitable for large-scale inaccessible region with serious environment.

Jeremiah O Abolade, Dominic B. O. Konditi

A meanderingly slitted bio-inspired (MSB)-shaped antenna is presented in this work. The footprint of the proposed MSB antenna is 12 × 10 mm20.12×0.10λg2  at  2.1GHz. The MSB antenna proposed in this operates at 2.1 GHz and 5.2 GHz frequencies with a bandwidth of 70 MHz and 570 MHz and a radiation efficiency of 52.5% and 96%, respectively, which is suitable for UMTS, radio navigation, Long Term Evolution (LTE), and 5 GHz Wireless Local Area Network (WLAN) applications. The proposed MSB antenna demonstrates a peak gain of 2.9 dBi at 5.2 GHz and an omnidirectional radiation pattern at both E-plane and H-plane in both operating bands. The fabrication and measurement of the proposed antenna prototype are presented. The parametric study of the proposed structure is performed and presented. Therefore, the proposed antenna is a promising candidate for modern portable devices.

Wei Xu, Jingchang Nan, Jing Liu

In this paper, a general design procedure of simple four steps for wideband circularly polarized (CP) antenna based on characteristic mode analysis (CMA) is proposed. CMA is performed to investigate the CP generation principle of the proposed radiator. Modal currents and their corresponding radiation patterns are studied for mode selection and feeding placement to achieve CP operation. Then, two feeding mechanisms are introduced to constitute two CP antenna prototypes, which are further analyzed and optimized by CMA. With the physical insight into radiation characteristics of the prototypes, two antennas employing coplanar waveguide (CPW) as feed are designed and optimized by full-wave simulation. To validate the design procedure, both antennas with the same dimension (35 × 40 × 1.6 mm3) are fabricated and measured. The experimental results show that both of the antennas have good CP radiation performance with a peak gain of 4.0 dBic and 2.5 dBic and axial ratio bandwidth (ARBW) of 48.3% and 44%, respectively. In addition, the experimental results are in good agreement with the radiation information provided by CMA.

Mohammad Monirujjaman Khan, Kaisarul Islam, Md. Nakib Alam Shovon et al.

The 60 GHz band is a great prospect to meet the future demand for short-range indoor communication requiring wide bandwidth and high data rates. This paper presents the design of a 60 GHz printed Q-slot patch antenna for body-centric communication. The Q-slot has a slot gap of 0.2 mm and is etched on a 6.5 mm × 11 mm rectangular patch. The slotted patch is mounted on an FR-4 (Flame Retardant) substrate that is 1.6 mm thick and has a relative permittivity of 4.3. With a partial ground plane of length of 2.2 mm, the antenna’s overall dimension is 12.9 mm × 14 mm × 1.6 mm. Computer Simulation Technology (CST) microwave studio was used to design and simulate the antenna. In free space, the antenna is resonant at 60.06 GHz with an impedance bandwidth of 12.11 GHz. At 60 GHz, the antenna’s radiation efficiency is 82.15%, with a maximum gain of 8.62 dBi. For further analysis, parametric changes were made to observe the effect on return loss, radiation efficiency, and gain. The antenna was simulated on a three-layer human torso phantom for the on-body scenario. The antenna’s resonant frequency shifted slightly to the right at 2 mm distant from the phantom while maintaining a very wide impedance bandwidth. At this point, the antenna’s radiation efficiency dropped to 56.68% and gradually increased to 74.04% at 10 mm. The maximum gain remained largely unaffected, but some grated radiation patterns were observed.

Stanislav Stefanov Zhekov, Jan Hvolgaard Mikkelsen, Gert Frølund Pedersen

Wireless earbuds have become the preferred electronic device for listening to music and for hands-free talking. The combined radio performance of the earbud and the handset determines the quality of the established communication link and hence the quality of the user experience. This paper presents an extensive comparative study of five common Bluetooth earbuds, where the transmit performance, in terms of total radiated power (TRP), is investigated. The measurements are conducted for the right-side earbud and for the low and high ends of the Bluetooth frequency spectrum. Moreover, two scenarios are considered: (1) the earbud is placed in free space and (2) the earbud is placed in a person’s ear. For the latter case, a total of 12 volunteers are involved in the measurement campaign. Measurements show that the mean performance deterioration, due to the placement of the earbud in the person’s ear, ranges from 3 to 6 dB across the tested earbuds.

Dan Schiller

Honglin Zhang, Dong Chen, Ying Yu et al.

In this paper, a novel design of compact microstrip antenna (MA) using an embedded λ/4 resonator is presented. By utilizing the strong coupling between the λ/4 resonator and the radiation patch of MA, the resonant frequency of MA can be decreased. Besides, the λ/4 resonator is embedded in the patch, which does not enlarge the whole size of MA. Therefore, a compact antenna can be realized. In this paper, after the principle is stated, a sample antenna has been manufactured and measured to prove the predicted characteristics of our proposed antenna. The measurement agrees well with the simulation. Hence, the proposed method in this paper is quite suitable for the design of a compact antenna.

Yao Nie, Chunyan Feng, Huan Wu et al.

In massive multiple-input multiple-output (MIMO) systems, phase noise introduced by oscillators can cause severe performance loss. It leads to common phase error and intercarrier interference in massive MIMO-OFDM uplink. To solve the issue, a novel phase noise cancelation scheme based on polarization modulation for the massive MIMO-OFDM system is proposed. We first introduce the polarization modulation (PM) exploited in massive MIMO-OFDM uplink. Then, by exploiting the zero-forcing detection, we analyze the asymptotically ICI and the distribution of the transformed noise under different XPD values. Furthermore, we demonstrate that phase noise can be asymptotically canceled and only the transformed additive white Gaussian noise exists as the number of antennas at the base station is very large. Moreover, we derive the instantaneous signal-to-noise ratio (SNR) on each subcarrier and analyze the ergodic capacity. To increase the ergodic capacity performance further, a joint modulation scheme combining the PM and 2PSK is proposed and the ergodic capacity performance of the joint modulation is discussed. The simulation results show that the proposed scheme can effectively mitigate phase noise and achieve a higher ergodic capacity.

2018, N. Mac, V. Venugopal et al.

BPOs (Business Process Outsourcing) are typically categorized into back office outsourcing or non-voice sector and front office outsourcing or voice based sector. While the non-voice process includes data encoding, database development, market research, handling of credit billing problems, loan processing, account management etc, the voice sector is often interchangeably referred to as the ‘Call Centre industry’ because the service entails interactive communication with the client or customers over the telephone.1 The call centre industry has emerged as one of the largest private sector employers in India, providing direct/indirect employment to more than 4.5 million people, with about 50% of employees around 25 years of age. The industry has grown by about 17% during the recent years providing more job opportunities.1 The nature of job in call centres leads to ‘Burnout Stress Syndrome’ (BOSS) characterized by chronic fatigue, insomnia and alteration of the 24-hour biological rhythm, which affects not only sleep but also proper functioning of the other body functions. Apart from the sedentary and unhealthy lifestyle which can lead to physical health problems, work pressure may also affect one’s mental, physical and psychosocial health.1 Studies with telecommunication employees using questionnaire have shown impacts on musculoskeletal issues and mental stress associated with seven psychosocial variables.2 Evidence from a study with female computer

Jonathan Lisein, Nathalie Pineux, Marc Pierrot-Deseilligny et al.

L'émergence des drones comme outils de cartographie rapide, de par leur capacité à répondre à des besoins très spécifiques, offre de nombreuses opportunités aux scientifiques. Par ailleurs, les récentes évolutions des techniques de photogrammétrie et de vision par ordinateur permettent, à partir de prises de vues aériennes stéréoscopiques, de fournir aux géomorphologues et aux hydrologues des données topographiques à haute résolution (Tarolli, 2014). En effet, les algorithmes d'orientation externe (structure from motion en anglais, Snavely et al. (2008)) permettent la détermination automatique de la position et de l'orientation des prises de vue d'une collection d'images se recouvrant. La corrélation dense automatique permet ensuite, depuis un bloc d'images orientées, de modéliser finement le relief. L'utilisation en géomorphologie de drones pour la modélisation du relief en est encore à ses premiers souffles, mais montre un potentiel très intéressant. La précision des mesures photogrammétriques rivalise en effet avec les relevés LiDAR, pour un coût d'acquisition significativement moins élevé. Cette recherche se focalise sur deux objectifs. Le premier est de déterminer si la précision des mesures photogrammétriques issues d'images acquises avec un mini-drone permet la détection de changement de relief très fin via la comparaison d'acquisitions multi-dates. Le deuxième objectif, plus spécifique, est de déterminer la manière la plus optimale de paramétrer la compensation par faisceaux avec points d'appui au sein de la suite photogrammétrique open-source MICMAC.

F. J. Corbató, V. A. Vyssotsky

A. O. Ologunde

Jianming Zhou

A new broadband planar dual-polarization base station antenna is proposed, the antenna consists of two broadband plane coplanar base station antenna units, and so it has features of plane antenna. Two broadband plane station antenna units can, respectively, form double polarization in the direction. We analyzed the relative positions between the two antenna units and their effects on the performances of the antenna, especially for the influence of isolation. Broadband antenna has the characteristics of the broadband station antenna, and bandwidth is also guaranteed. The measured results show that the antenna can obtain 45% relative bandwidth, and 30 dB isolation degree also can be got, and the radiation performance is also good. Measurement results confirmed that the antenna gain can be guaranteed among 48% relative bandwidth, 15 dB of gain is got among bandwidth of 1.69–2.78 GHz, the isolation degree of different polarization method can reach 30 dB, and the measurement gain of two polarization methods of antenna both can reach 8.5 dBi.

Wenqian Xue, Hengzhi Zhang, Yong Li et al.

Heterogeneous networks (HetNets) can increase network capacity through complementing the macro-base-station with low-power nodes, in response to the ongoing exponential growth in data traffic demand. While, unprecedented challenges exist in the planning, optimization, and maintenance in HetNets, especially activities such as cell outage detection and mitigation are labor-intensive and costly. One potential solution to address these issues is to introduce the extensively attracted self-organizing network (SON). This paper is mainly devoted to cell outage detection and compensation methods in two-tier HetNets where macrocell and picocells are coexisted. A K-nearest neighbor (KNN) classification algorithm is employed to detect the cell outage automatically. Consider the breakdown picocell can reload its degraded service to the overlapped macrocell via vertical handover; only the breakdown macrocell executes the performance compensation. Power adjustment on each resource block is carried out via Lagrange optimizing algorithm to compensate the breakdown cell. Through intensive numerical experiments, with the help of our proposal, the outage cells can be successfully detected and performance gain for the outage macrocell can reach 91.4% with α=1/3.

Idnin Pasya, Naohiko Iwakiri, Takehiko Kobayashi

This paper presents a joint direction-of-departure (DOD) and direction-of-arrival (DOA) estimation in a multiple-input multiple-output (MIMO) radar utilizing ultra wideband (UWB) signals in detecting targets with fluctuating radar cross sections (RCS). The UWB MIMO radar utilized a combination of two-way MUSIC and majority decision based on angle histograms of estimated DODs and DOAs at each frequency of the UWB signal. The proposed angle estimation scheme was demonstrated to be effective in detecting targets with fluctuating RCS, compared to conventional spectra averaging method used in subband angle estimations. It was found that a wider bandwidth resulted in improved estimation performance. Numerical simulations along with experimental evaluations in a radio anechoic chamber are presented.