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

Yushi Shen, Yale Li, Ling Wu et al.

T. Greenhalgh, Emma Ladds, G. Hughes et al.

Background Fewer than 1% of UK general practice consultations occur by video. Aim To explain why video consultations are not more widely used in general practice. Design and setting Analysis of a sub-sample of data from three mixed-method case studies of remote consultation services in various UK settings from 2019–2021. Method The dataset included interviews and focus groups with 121 participants from primary care (33 patients, 55 GPs, 11 other clinicians, nine managers, four support staff, four national policymakers, five technology industry). Data were transcribed, coded thematically, and then analysed using the Planning and Evaluating Remote Consultation Services (PERCS) framework. Results With few exceptions, video consultations were either never adopted or soon abandoned in general practice despite a strong policy push, short-term removal of regulatory and financial barriers, and advances in functionality, dependability, and usability of video technologies (though some products remained ‘fiddly’ and unreliable). The relative advantage of video was perceived as minimal for most of the caseload of general practice, since many presenting problems could be sorted adequately and safely by telephone and in-person assessment was considered necessary for the remainder. Some patients found video appointments convenient, appropriate, and reassuring but others found a therapeutic presence was only achieved in person. Video sometimes added value for out-of-hours and nursing home consultations and statutory functions (for example, death certification). Conclusion Efforts to introduce video consultations in general practice should focus on situations where this modality has a clear relative advantage (for example, strong patient or clinician preference, remote localities, out-of-hours services, nursing homes).

Ndanga Adamou Eric, Eke Samuel, Matanga Jacques et al.

The main challenge in manufacturing antennas in the sub-THz band is their small size, which requires adapted manufacturing tools. This paper proposes a uniform linear 3 × 1 traveling-wave antenna array (ULTWAA) for millimetre applications in the sub-THz band. The designed array allows a continuous beam orientation of ±46.1° in the E-plane. A small quarter-wave line added to the ends of the antenna allows the beam to be oriented towards the inside of the antenna, cancelling out surface waves and adapting the impedance to the scanning angle. Thanks to this device, the waves produced are progressive. The antenna manufactured at 100 GHz measures 13 × 9.7 × 0.125 mm. The measured peak gain is 14.2 dBi with 70% bandwidth. For in-phase radiation, the distances between the antenna units have been adjusted, but the adjustment process is tedious due to the interdependence between the antenna units.

A. Singh

A revolution in wireless communication began in the first decade of the 20th century with the pioneering developments in radio communications by Guglielmo Marconi, who won the Nobel Prize in Physics in 1909. Other highly notable pioneering inventors and developers in the field of electrical and electronic telecommunications include Charles Wheatstone and Samuel Morse (telegraph), Alexander Graham Bell (telephone), Edwin Armstrong, and Lee de Forest(radio), as well as Vladimir K. Zworykin, John Logie Baird and Philo Farnsworth (television). In this paper we have discuss about the services and the quality with basic comparison between the different telecom companies. Numbers of telecom companies providing telecom services in Saudi Arabia which includes fixed and cellular phones as well as internet and issues relating to the provision of other services. Main telecom companies in Saudi Arabia are: STC, Mobily, Zain, ITC, GO Telecom (Etihad Atheeb Telecom), Bayanat and Arab Satellite Communications Organization. Saudi Telecom Company (STC) is the first company in Saudi Arabia, and then allowed Communications Commission to compete with other companies in Saudi Arabia and then it becomes a number one of telecom companies. In Saudi Arabia five companies are in competition: STC Mobile: STC includes landlines, mobile, mobile (phone) and Sawa; ITC (Integrated Telecom Company): second operator after STC and offers internet, broadband, connectivity and satellite services for businesses, consumers and wholesale; Mobily: It provide mobile and internet Fabraupetk (Fiber Optic)

David Ginthör, J. V. Hoyningen-Huene, René Guillaume et al.

New use cases and vertical integration in the area of industrial automation are making flexible and large-scale communication systems with real-time capabilities more essential than ever before. Time-sensitive networking (TSN) is addressing a unification of many existing industrial Ethernet technologies to leverage cross-domain flexibility while guaranteeing end-to-end service requirements. Extending TSN capabilities over the wireless domain using 5G cellular network technologies is currently seen as a promising approach to meet the requirements of a highly flexible cyber-physical system as envisioned in the context of Industry 4.0. In this paper, we provide a detailed overview on the integration of 5G and TSN. We present a system-level simulator to investigate the impact and derive requirements on the end-to-end system when supporting time-sensitive deterministic traffic. Based on the results, we analyze implications on the scheduling of multiple end-to-end streams with cross traffic over an integrated 5G and TSN network.

Ali H. Alqahtani, Khaled Humadi, Ahmed Iyanda Sulyman et al.

Multiple-input multiple-output (MIMO) wireless technology in combination with orthogonal frequency-division multiplexing (MIMO-OFDM) is an attractive technique for next-generation wireless systems. However, the performance of wireless links is severely degraded due to various channel impairments which cause a decoding failure and lead to packet loss at the receiver. One technique to cope with this problem is the rateless space-time block code (RSTBC). This paper presents experimental results on the performance of a 2×2 MIMO-OFDM system with RSTBC as measured in a testbed implemented with field-programmable gate array (FPGA). The average bit error rate (BER) performance of the proposed scheme is evaluated experimentally, and the results agree closely with simulation and analytical upper bound. It has been shown that RSTBC can be implemented in real-world scenarios and guarantee the reliability of loss-prone wireless channels.

Raghad Ghalib Saadallah Alsultan, Gölge Ögücü Yetkin

E-shaped multiple-input-multiple-output (MIMO) microstrip antenna systems operating in WLAN and WiMAX bands (between 5 and 7.5 GHz) are proposed with enhanced isolation features. The systems are comprised of two antennas that are placed parallel and orthogonal to each other, respectively. According to the simulation results, the operating frequency of the MIMO antenna system is 6.3 GHz, and mutual coupling is below −18 dB in a parallel arrangement, whereas they are 6.4 GHz and −25 dB, respectively, in the orthogonal arrangement. The 2 × 3 matrix of C-shaped resonator (CSR) is proposed and placed between the antenna elements over the substrate, to reduce the mutual coupling and enhance the isolation between the antennas. More than 30 dB isolation between the array elements is achieved at the resonant frequency for both of the configurations. The essential parameters of the MIMO array such as mutual coupling, surface current distribution, envelop correlation coefficient (ECC), diversity gain (DG), and the total efficiency have been simulated to verify the reliability and the validity of the MIMO system in both parallel and orthogonal configurations. The experimental results are also provided and compared for the mutual coupling with simulated results. An adequate match between the measured and simulated results is achieved.

Sorana Niyamanon, Rewat Senathong, Chuwong Phongcharoenpanich

This research proposes a dual-frequency circularly polarized truncated square aperture patch antenna with slant stripline and L-shaped slot for WLAN applications. In the antenna design, the parameters were optimized and the WLAN-enabled dual-frequency (2.4 and 5.8 GHz) antenna was realized. Simulations were subsequently carried out for the impedance bandwidth (S11) < −10 dB, axial ratio (AR) ≤ 3 dB, optimal gain, and bidirectional radiation pattern. To validate, an antenna prototype was fabricated and the experiments were undertaken. The simulated and experimental results are in good agreement. In essence, the proposed WLAN-enabled dual-frequency circularly polarized antenna is most suited for applications in the vertically and horizontally elongated areas, including in the tunnel, train carriage, and buildings.

Laura Corchia, Giuseppina Monti, Luciano Tarricone

Adhesive nonwoven conductive fabrics are appealing materials for fabricating fully textile antennas for wearable wireless systems. Wearable antennas should be flexible, lightweight, and mechanically resistant. Additionally, the antenna performance should be robust to activities related to daily use of garments, such as washing and ironing. Accordingly, in this work, the results of several washing tests performed on fully textile antennas fabricated by exploiting three different adhesive nonwoven conductive fabrics are reported.

Xiao Xiao, Xiaoming Tao, Jianhua Lu

Hana Šuster Erjavec, T. Dmitrović, P. P. Bržan

The relationship between customer satisfaction, customer loyalty and their antecedents, service output quality, quality of staff, corporate image, and price perception, is examined in the context of three service industries: use of the highway infrastructure, mobile telephone services, and hairdressing services. The research model was empirically evaluated for a large sample of respondents from a Central European country, using structural equation modelling. The results indicate that the four antecedents affect customer loyalty, and customer satisfaction acts as a mediator in all three service industries. However, the strength of the relationship between the constructs varies markedly across the industries, implying that competitive environment importantly determines the elements of service offering that lead to satisfaction and loyalty in a particular industry. The research findings contribute to a better understanding of which behavioural mechanisms and factors are a viable basis for increasing customer retention in a specific market structure. Managerial implications are discussed, and policy recommendations are offered.

Amanda Fallin, A. Goodin, Brian A. King

Niamat Hussain, Truong Khang Nguyen, Haewook Han et al.

We designed a slit dipole antenna backed by an extended hemispherical silicon lens and investigated the minimum lens size in which the slit dipole antenna works as a leaky-wave antenna. The slit dipole antenna consists of a planar feeding structure, which is a center-fed and open-ended slot line. A slit dipole antenna backed by an extended hemispherical silicon lens is investigated over a frequency range from 0.2 to 0.4 THz with the center frequency at 0.3 THz. The numerical results show that the antenna gain responses exhibited an increased level of sensitivity to the lens size and increased linearly with increasing lens radius. The lens with the radius of 1.2λo is found to be the best possible minimum lens size for a slit dipole antenna on an extended hemispherical silicon lens.

Abdurrahim Toktas

A novel and compact scalable antenna system is designed for multiport applications. The basic design is built on a square patch with an electrical size of 0.82λ0×0.82λ0 (at 2.4 GHz) on a dielectric substrate. The design consists of four symmetrical and orthogonal triangular notches with circular feeding slots at the corners of the common patch. The 4-port antenna can be simply rearranged to 8-port and 12-port systems. The operating band of the system can be tuned by scaling (S) the size of the system while fixing the thickness of the substrate. The antenna system with S: 1/1 in size of 103.5×103.5 mm2 operates at the frequency band of 2.3–3.0 GHz. By scaling the antenna with S: 1/2.3, a system of 45×45 mm2 is achieved, and thus the operating band is tuned to 4.7–6.1 GHz with the same scattering characteristic. A parametric study is also conducted to investigate the effects of changing the notch dimensions. The performance of the antenna is verified in terms of the antenna characteristics as well as diversity and multiplexing parameters. The antenna system can be tuned by scaling so that it is applicable to the multiport WLAN, WIMAX, and LTE devices with port upgradability.

Hu Jian-rong, Li Jiu-sheng, Wu Di

The analysis and design of a small planar multiband antenna operating in the 4G frequency bands are presented. The numerical and experimental results demonstrated that the proposed antenna satisfies the requirement of 6 dB return loss for the impedance bandwidth of the LTE700/LTE2300/LTE2500 and WiMAX3500 bands. The gains at 750 MHz/2.3 GHz/2.6 GHz/3.5 GHz are 2.1 dBi/4.9 dBi/4.7 dBi/4.3 dBi, respectively. The measured radiation patterns verify the suitability of the antenna to be employed in mobile phones. The dimensions of the radiant patch are 49 × 10 mm2. The proposed antenna can be easily fabricated and customized to various 4G mobile phones as a compact internal antenna.

Chen Pang, Peter Hoogeboom, François Le Chevalier et al.

This paper presents a theoretical analysis for the accuracy requirements of the planar polarimetric phased array radar (PPPAR) in meteorological applications. Among many factors that contribute to the polarimetric biases, four factors are considered and analyzed in this study, namely, the polarization distortion due to the intrinsic limitation of a dual-polarized antenna element, the antenna pattern measurement error, the entire array patterns, and the imperfect horizontal and vertical channels. Two operation modes, the alternately transmitting and simultaneously receiving (ATSR) mode and the simultaneously transmitting and simultaneously receiving (STSR) mode, are discussed. For each mode, the polarimetric biases are formulated. As the STSR mode with orthogonal waveforms is similar to the ATSR mode, the analysis is mainly focused on the ATSR mode and the impacts of the bias sources on the measurement of polarimetric variables are investigated through Monte Carlo simulations. Some insights of the accuracy requirements are obtained and summarized.

Yen-Sheng Chen, Ting-Yu Ku

This paper presents an extremely efficient method for antenna design and optimization. Traditionally, antenna optimization relies on nature-inspired heuristic algorithms, which are time-consuming due to their blind-search nature. In contrast, design of experiments (DOE) uses a completely different framework from heuristic algorithms, reducing the design cycle by formulating the surrogates of a design problem. However, the number of required simulations grows exponentially if a full factorial design is used. In this paper, a much more efficient technique is presented to achieve substantial time savings. By using orthogonal fractional experiments, only a small subset of the full factorial design is required, yet the resultant response surface models are still effective. The capability of orthogonal fractional experiments is demonstrated through three examples, including two tag antennas for radio-frequency identification (RFID) applications and one internal antenna for long-term-evolution (LTE) handheld devices. In these examples, orthogonal fractional experiments greatly improve the efficiency of DOE, thereby facilitating the antenna design with less simulation runs.

Jianwei Huang, Lin Gao

Today's wireless communications and networking practices are tightly coupled with economic considerations, to the extent that it is almost impossible to make a sound technology choice without understanding the corresponding economic implications. This book aims at providing a foundational introduction on how microeconomics, and pricing theory in particular, can help us to understand and build better wireless networks. The book can be used as lecture notes for a course in the field of network economics, or a reference book for wireless engineers and applied economists to understand how pricing mechanisms influence the fast growing modern wireless industry. This book first covers the basics of wireless communication technologies and microeconomics, before going in-depth about several pricing models and their wireless applications. The pricing models include social optimal pricing, monopoly pricing, price differentiation, oligopoly pricing, and network externalities, supported by introductory discussions of convex optimization and game theory. The wireless applications include wireless video streaming, service provider competitions, cellular usage-based pricing, network partial price differentiation, wireless spectrum leasing, distributed power control, and cellular technology upgrade. More information related to the book (including references, slides, and videos) can be found at ncel.ie.cuhk.edu.hk/content/wireless-network-pricing. Table of Contents: Introduction / Wireless Communications Basics / Economics Basics / Social Optimal Pricing / Monopoly and Price Discriminations / Oligopoly Pricing / Network Externalities / Outlook

Baharak Mohajer-Iravani, Omar M. Ramahi

Electromagnetic bandgap structures are considered a viable solution for the problem of switching noise in printed circuit boards and packages. Less attention, however, has been given to whether or not the introduction of EBGs affects the EMI potential of the circuit to couple unwanted energy to neighboring layers or interconnects. In this paper, we show that the bandgap of EBG structures, as generated using the Brillouin diagram, does not necessarily correspond to the suppression bandwidth typically generated using S-parameters. We show that the reactive near fields radiating from openings within the EBG layers can be substantial and are present in the entire frequency band including propagating and nonpropagating mode regions. These fields decay fast with distance; however, they can couple significant energy to adjacent layers and to signal lines. The findings are validated using full-wave three-dimensional numerical simulation. Based on this work, design guidelines for EBG structures can be drawn to insure not only suppression of switching noise but also minimization of EMI and insuring signal integrity.

Lorenzo Poli, Toshifumi Moriyama, Paolo Rocca

A novel strategy for harmonic beamforming in time-modulated linear arrays is proposed. The pulse splitting technique is exploited to simultaneously generate two harmonic patterns, one at the central frequency and another at a preselected harmonic of arbitrary order, while controlling the maximum level of the remaining sideband radiations. An optimization strategy based on the particle swarm optimizer is developed in order to determine the optimal parameters describing the pulse sequence used to modulate the excitation weights of the array elements. Representative numerical results are reported and discussed to point out potentialities and limitations of the proposed approach.