No Arabic abstract
In this work, the designs of a single-stage and 2-stage 2.4 GHz power amplifier (PA) are presented. The proposed PAs have been designed to provide high gain and improved efficiency using harmonic suppression and optimized impedance matching techniques. There are two harmonic suppression circuits, each stage of the PA consists of 2 capacitors and 2 inductors, which will help to suppress the harmonic frequency for 2.4 GHz. These suppression circuits will help to enhance the overall efficiency of the PAs. Both the PAs are provided with a VCC supply of 4.2V. Input and output impedances are matched to 50 ohms. Simulation and experimental results are presented, where the simulated gain and power added efficiency (PAE) for single stage PA are 17:58dB and 53%, respectively. While the experimental gain and PAE are 16:7dB and 49.5%, respectively. On the other hand, for 2-stages PA, simulated gain comes out to be 34.6dB and PAE is 55%, while the experimental gain and PAE are 30.5dB and 53.1%, respectively. The final design is being fabricated on the Taconic printed circuit board (PCB) with a thickness of 0.79mm and the dielectric constant value of 3.2 and its dimensions are 4.6cm x 3.4cm for single stage and 5.9cm x 3.6cm for 2-stages PA.
A secure downlink transmission system which is exposed to multiple eavesdroppers and is appropriate for Internet of Things (IoT) applications is considered. A worst case scenario is assumed, in the sense that, in order to enhance their interception ability all eavesdroppers are located close to each other, near the controller and collude to form joint receive beamforming. For such a system, a novel cooperative non-orthogonal multiple access (NOMA) secure transmission scheme for which an IoT device with a stronger channel condition acts as an energy harvesting relay in order to assist a second IoT device operating under weaker channel conditions, is proposed and its performance is analyzed and evaluated. A secrecy sum rate (SSR) maximization problem is formulated and solved under three constraints: i) Transmit power; ii) Successive interference cancellation; iii) Quality of Service. By considering both passive and active eavesdroppers scenarios, two optimization schemes are proposed to improve the overall system SSR. On the one hand, for the passive eavesdropper scenario, an artificial noise-aided secure beamforming scheme is proposed. Since this optimization problem is nonconvex, instead of using traditional but highly complex, bruteforce two-dimensional search, it is conveniently transformed into a convex one by using an epigraph reformulation. On the other hand, for the active multi-antennas eavesdroppers scenario, the orthogonal-projection-based beamforming scheme is considered, and by employing the successive convex approximation method, a suboptimal solution is proposed. Furthermore, since for single antenna transmission the orthogonal-projection-based scheme may not be applicable a simple power control scheme is proposed.
The Doherty power amplifier (DPA) has been extensively explored in the past and has become one of the most widely used power amplifier (PA) architectures in cellular base stations. The classical DPA suffers intrinsic bandwidth constrains which limit its application in future 5G wireless transmitters. In this paper, we present a comprehensive review of the DPA bandwidth enhancement techniques proposed in literature in order to provide a thorough understanding of the DPAs broadband design for high-efficiency 5G wireless transmitters. We elaborate on the main bandwidth limitation sources and provide circuit design insights. We then follow with an overview of bandwidth enhancement techniques developed for the DPA, including modified load-modulation networks, frequency response optimization, parasitic compensation, post-matching, as well as distributed DPA, dual-input digital DPA, transformer-based power-combining PA, and transformer-less load modulated PA architectures. Furthermore, challenges and design techniques for integrated circuit (IC) implementation of broadband DPAs are discussed, including a review of circuits developed in CMOS, SiGe, and GaN processes, and operating in RF and mm-Wave frequencies.
The Internet of Things (IoT) is penetrating many facets of our daily life with the proliferation of intelligent services and applications empowered by artificial intelligence (AI). Traditionally, AI techniques require centralized data collection and processing that may not be feasible in realistic application scenarios due to the high scalability of modern IoT networks and growing data privacy concerns. Federated Learning (FL) has emerged as a distributed collaborative AI approach that can enable many intelligent IoT applications, by allowing for AI training at distributed IoT devices without the need for data sharing. In this article, we provide a comprehensive survey of the emerging applications of FL in IoT networks, beginning from an introduction to the recent advances in FL and IoT to a discussion of their integration. Particularly, we explore and analyze the potential of FL for enabling a wide range of IoT services, including IoT data sharing, data offloading and caching, attack detection, localization, mobile crowdsensing, and IoT privacy and security. We then provide an extensive survey of the use of FL in various key IoT applications such as smart healthcare, smart transportation, Unmanned Aerial Vehicles (UAVs), smart cities, and smart industry. The important lessons learned from this review of the FL-IoT services and applications are also highlighted. We complete this survey by highlighting the current challenges and possible directions for future research in this booming area.
In this paper, we propose a Meta-IoT system to achieve ubiquitous deployment and pervasive sensing for future Internet of Things (IoT). In such a system, sensors are composed of dedicated meta-materials whose frequency response of wireless signal is sensitive to environmental conditions. Therefore, we can obtain sensing results from reflected signals through Meta-IoT devices and the energy supplies for IoT devices can be removed. Nevertheless, in the Meta-IoT system, because the positions of the Meta-IoT devices decide the interference among the reflected signals, which may make the sensing results of different positions hard to be distinguished and the estimation function should integrate the results to reconstruct 3D distribution. It is a challenge to optimize the positions of the Meta-IoT devices to ensure sensing accuracy of 3D environmental conditions. To handle this challenge, we establish a mathematical model of Meta-IoT devices sensing and transmission to calculate the interference between Meta-IoT devices. Then, an algorithm is proposed to jointly minimize the interference and reconstruction error by optimizing the Meta-IoT devices position and the estimation function. The simulation results verify that the proposed system can obtain a 3D environmental conditions distribution with high accuracy.
The sixth generation (6G) wireless communication networks are envisioned to revolutionize customer services and applications via the Internet of Things (IoT) towards a future of fully intelligent and autonomous systems. In this article, we explore the emerging opportunities brought by 6G technologies in IoT networks and applications, by conducting a holistic survey on the convergence of 6G and IoT. We first shed light on some of the most fundamental 6G technologies that are expected to empower future IoT networks, including edge intelligence, reconfigurable intelligent surfaces, space-air-ground-underwater communications, Terahertz communications, massive ultra-reliable and low-latency communications, and blockchain. Particularly, compared to the other related survey papers, we provide an in-depth discussion of the roles of 6G in a wide range of prospective IoT applications via five key domains, namely Healthcare Internet of Things, Vehicular Internet of Things and Autonomous Driving, Unmanned Aerial Vehicles, Satellite Internet of Things, and Industrial Internet of Things. Finally, we highlight interesting research challenges and point out potential directions to spur further research in this promising area.