The integration of fifth-generation (5G) and unmanned aerial vehicle (UAV) technologies has become a promising solution for providing seamless communication in applications, such as disaster management, because of its bandwidth availability, cost-efficacy, and mobile nature. The state-of-the-art research in UAV communication concentrates on effective positioning and path planning. Despite this, these systems performed poorly due to a lack of dynamic control and external factors, such as weather. The solution presented in this paper addresses the problems listed above by using dynamic positioning and energy-efficient path planning for disaster scenarios in the 5G-assisted multi-UAV environments (Dynamic-UAV) to maximize the performance metrics. The lightweight gated recurrent unit (LGRU) is used for weather and event prediction to determine the disaster and non-disaster area and the context of the disaster. The density-based optics clustering (DBOC) algorithm is used to achieve reliability during communication with cluster IoT devices in disaster and non-disaster regions. The satellite determines the number of UAVs required and positions the UAVs using the dynamic positioning-based soft actor–critic (DPSAC) algorithm to achieve maximum throughput. Moreover, the UAVs’ path planning is performed using the shuffled shepherd optimization with dynamic-window method (SSO-DWM) to reduce energy consumption. The proposed approach is simulated using the NS 3.26 simulator and validated by comparing the results with existing techniques regarding the quality of service (QoS), reliability, and energy efficiency. Experimental results indicate that the proposed method achieved maximum throughput (1.59 bit/s), packet delivery ratio (0.88), coverage probability (0.82), number of collected packets (7109–5875), energy efficiency (1.544), minimum delay (16.4 ms–18.5 ms), and energy consumption (7.48 KJ).

In this paper, we present an ultrawideband reflective metasurface with the properties of an LTC-PC, which is an orthotropic composition with two mutually orthogonal symmetric axes, v and u, and 45° rotation about the vertical y-axis. Based on the metasurface unit cell, it seems like a circular pie embedded with a rectangular patch. The converter can convert LP electromagnetic (EM) waves to CP waves over the bands from 20.18 GHz to 33.93 GHz, with a 3-dB AR bandwidth of up to 50.8% and a circular polarization wave that is RHCP (right hand CP). Moreover, the linear-to-circular PCR exceeds 98% in the frequency bands of 20–34 GHz. A comprehensive theoretical investigation was conducted to determine the fundamental cause of the LTC polarization conversion. The $∆{\phi }_{uv}$ between two reflection coefficients at v- and u-polarized incidences is ±90°, which fully anticipates the axial ratio of the reflected wave. Any reflective metasurface can be used as an efficient LTC-PC if the $∆{\phi }_{uv}$ is close to ±90°.

This article describes a high-efficiency harmonic suppression metasurface (HSMS) energy collector, which is insensitive to frequency, input power, and load. A method of integrating harmonic suppression function into energy collection metasurface (MS) to improve system conversion efficiency is proposed. Integrated RF synthesis channels in HSMS improve diode power availability and turn-on time. An $8\times 8$ finite element MS array was designed and fabricated, achieving a conversion efficiency $_{\mathrm {RF}-\mathrm {ac}}$ of 96%. The measurement results show that the integrated harmonic suppression can improve the efficiency of ac–dc conversion by 2%–4%. In addition, we propose an impedance compression rectifier to reduce the input power and load requirements of the system. Since HSMS eliminates harmonic suppression networks, the rectifier structure is simple and compact. Finally, the system achieved an efficiency of 74.5% at 5.8 GHz with an input power of 18 dBm. Importantly, it shows that HSMS energy collectors can remain efficient over a wide range of power 6–25 dBm and loads of 500– $2000~\Omega $ . The proposed concept is suitable for high-efficiency microwave power transmission (MPT) systems with different input power and load conditions.

A multi-band compact flexible energy harvester which consists of a novel slotted broadband antenna and a miniaturized broadband rectifying circuit is proposed for the primary communication (GSM-900, GSM-1800) and industrial/scientific/medical (ISM-2450, ISM-5800) band applications. It is found that the newly designed antenna which combines a coplanar waveguide-based feed structure with a symmetrical sickle groove (SSG) to obtain the best matching performance and radiation performance. A broadband matching network based on a cross-shaped bent short-cut wire is proposed to maximize the transmission of power and minimize the size of rectifier. At an input power of 5dBm, the proposed multi-band energy harvester obtains 34%-50% efficiency _RF-DC at 0.9GHz, 1.8GHz, 2.45GHz and 5.8GHz. The measurement results proved that for different bent states, the proposed flexible harvester does not display large variations in harvesting efficiency. Therefore, this energy harvester with flexibility, compactness and stability is ideal for wireless power supply to wearable and portable IoT devices.

Providing robust communication services to mobile users (MUs) is a challenging task due to the dynamicity of MUs. Unmanned aerial vehicles (UAVs) and mobile edge computing (MEC) are used to improve connectivity by allocating resources to MUs more efficiently in a dynamic environment. However, energy consumption and lifetime issues in UAVs severely limit the resources and communication services. In this paper, we propose a dynamic cooperative resource allocation scheme for MEC–UAV-enabled wireless networks called joint optimization of trajectory, altitude, delay, and power (JO-TADP) using anarchic federated learning (AFL) and other learning algorithms to enhance data rate, use rate, and resource allocation efficiency. Initially, the MEC–UAVs are optimally positioned based on the MU density using the beluga whale optimization (BLWO) algorithm. Optimal clustering is performed in terms of splitting and merging using the triple-mode density peak clustering (TM-DPC) algorithm based on user mobility. Moreover, the trajectory, altitude, and hovering time of MEC–UAVs are predicted and optimized using the self-simulated inner attention long short-term memory (SSIA-LSTM) algorithm. Finally, the MUs and MEC–UAVs play auction games based on the classified requests, using an AFL-based cross-scale attention feature pyramid network (CSAFPN) and enhanced deep Q-learning (EDQN) algorithms for dynamic resource allocation. To validate the proposed approach, our system model has been simulated in Network Simulator 3.26 (NS-3.26). The results demonstrate that the proposed work outperforms the existing works in terms of connectivity, energy efficiency, resource allocation, and data rate.

In this article, a novel and high-efficiency dual-wideband linear-to-circular polarization conversion based on a rectangular-slot reflective metasurface is anticipated, one that can convert linearly polarized (LP) electromagnetic waves into right- and left-hand circularly polarized waves in two non-adjacent frequency bands. The converter is an orthotropic design, with a pair of mutually orthogonal symmetric axes (u and v) along orientations tilted at 45° to the y-axis. The simulated results indicate that the dual-wideband circularly polarized wave is achieved under a y-polarized an electromagnetic (EM) incidence wave over the bands of 16.49–23.54 GHz and 26.44–34.56 GHz with 3 dB axial ratio relative bandwidths of 35.23% and 26.62%, respectively, and a polarization conversion ratio (PCR) in excess of 99%. A detailed mathematical investigation is proposed to determine the fundamental factor causing the dual-wideband linear-to-circular polarization conversion. The phase difference ($∆{\phi }_{uv})$ between r_uu and r_vv under u- and v- polarized incident waves is $\pm 90°$, and it entirely determines the 3 dB reflected wave axial ratio. Any reflective converter can work efficiently as a linear-to-circular polarization conversion if the phase difference ($∆{\phi }_{uv})$ is close to $\pm 90°$.