Research and development on the next generation wireless systems, namely 5G, has experienced explosive growth in recent years. In the physical layer, the massive multiple-input-multiple output (MIMO) technique and the use of high GHz frequency bands are two promising trends for adoption. Millimeter-wave (mmWave) bands, such as 28, 38, 64, and 71 GHz, which were previously considered not suitable for commercial cellular networks, will play an important role in 5G. Currently, most 5G research deals with the algorithms and implementations of modulation and coding schemes, new spatial signal processing technologies, new spectrum opportunities, channel modeling, 5G proof of concept systems, and other system-level enabling technologies. In this paper, we first investigate the contemporary wireless user equipment (UE) hardware design, and unveil the critical 5G UE hardware design constraints on circuits and systems. On top of the said investigation and design tradeoff analysis, a new, highly reconfigurable system architecture for 5G cellular user equipment, namely distributed phased arrays based MIMO (DPA-MIMO) is proposed. Finally, the link budget calculation and data throughput numerical results are presented for the evaluation of the proposed architecture.

The rapid advancement of Internet of Things (IoT) and 5G and beyond technologies are transforming the marine industry and research. Our understanding of the vast sea that covers 71% of the Earth’s surface is being enhanced by the various ocean sensor networks equipped with effective communications technologies. In this paper, we begin with a review of the research and development status-quo of maritime IoT (MIoT) enabled by multiple wireless communication technologies. Then we study the impact of sea waves to radio propagation and the communications link quality. Due to the severe attenuation of sea water to radio frequency electromagnetic waves propagation, large ocean waves can easily block the communications link between a buoy sensor and a cell tower near shore. This paper for the first time uses the ocean wave modeling of coastal and oceanic waters to examine the line of sight communications condition. Real wave measurement data parameters are applied in the numerical evaluation of the developed model. Finally, the critical antenna design taking into account the wave impact is numerically studied with implementation solutions proposed, and the system hardware and protocol aspects are discussed.

Unmanned aerial vehicles (UAVs) for wireless communications have rapidly grown into a research hotspot as the mass production of high-performance, low-cost, intelligent UAVs become practical. In the meantime, the fifth generation (5G) wireless communication and internet of things (IoT) technologies are being standardized and planned for global deployment. During this process, UAVs are becoming an important part of 5G and IoT, and expected to play a crucial role in enabling more functional diversity for wireless communications. In this paper, we first present a summary of mainstream UAVs and their use in wireless communications. Then, we propose a hierarchical architecture of UAVs with multi-layer and distributed features to facilitate the integration of different UAVs into the next-generation wireless communication networks. Finally, we unveil the design trade-offs with the consideration of power transfer, wireless communication and aerodynamic principles. In particular, empirical models and published measurement data are used to analyze power transfer efficiency, and meteorological impacts on UAVs enabled next-generation wireless communications.

The fifth generation (5G) research and development has been fueled by many new breakthroughs in various areas. The recent progress in carrier aggregation (CA), licensed assisted access (LAA), massive MIMO (MaMi), beamforming techniques, cooperative spectrum sensing (CSS), compressive sensing (CS), machine learning, etc., has provided inspiring and promising approaches to address 5G and beyond challenges. However, at the user equipment (UE) end, limited design budget and hardware resources bring along a series of challenging implementation issues when delivering multi-standard and multi-functional wireless communications. In this paper, we first review recent advances in technical standards and critical enabling techniques, accompanied with several case studies of product developments. After the classification of typical 5G application and deployment scenarios, we propose and analyze a novel hardware reuse and multiplexing solution to facilitate cost-effective and energy-efficient UE design, followed by an investigation of state-of-the-art hardware development from the systems and circuits standpoint. Moreover, wireless UE hardware solutions, UE proof-of-concept (PoC) implementation and field test are proposed and discussed. Finally, the new trends of UE design and terahertz technologies for 5G and beyond applications are investigated and envisioned.

At the dawn of the next-generation wireless systems and networks, massive multiple-input multiple-output (MIMO) in combination with leading-edge technologies, methodologies, and architectures are poised to be a cornerstone technology. Capitalizing on its successful integration and scalability within 5G and beyond, massive MIMO has proven its merits and adaptability. Notably, a series of evolutionary advancements and revolutionary trends have begun to materialize in recent years, envisioned to redefine the landscape of future 6G wireless systems and networks. In particular, the capabilities and performance of future massive MIMO systems will be amplified through the incorporation of cutting-edge technologies, structures, and strategies. These include intelligent omni-surfaces (IOSs)/intelligent reflecting surfaces (IRSs), artificial intelligence (AI), Terahertz (THz) communications, and cell-free architectures. In addition, an array of diverse applications built on the foundation of massive MIMO will continue to proliferate and thrive. These encompass wireless localization and sensing, vehicular communications, non-terrestrial communications, remote sensing, and inter-planetary communications, among others.

Unmanned aerial vehicle (UAV) is being integrated as an active element in 5G and beyond networks. Because of its flexibility and mobility, UAV base stations (UAV-BSs) can be deployed according to the ground user distributions and their quality of service (QoS) requirement. Although there has been quite some prior research on the UAV deployment, no work has studied this problem in a 3-D setting and taken into account the UAV-BS capacity limit and the QoS requirements of ground users. Therefore, in this article, we focus on the problem of deploying UAV-BSs to provide satisfactory wireless communication services, with the aim to maximize the total number of covered user equipment subject to user data-rate requirements and UAV-BSs’ capacity limit. First, we model the relationship between the air-to-ground path loss (PL) and the location of UAV-BSs in both horizontal and vertical dimensions which has not been considered in previous works. Unlike the conventional UAV deployment problem formulation, the 3-D deployment problem is decoupled into a 2-D horizontal placement and altitude determination connected by PL requirement and minimization. Then, we propose a novel genetic algorithm-based 2-D placement approach in which UAV-BSs are placed to have maximum coverage of the users with consideration of data rate distribution. Finally, numerical and simulation results show that the proposed approach has enabled a better coverage percentage comparing with other schemes.