# Antennas and Propagation Aspects for Emerging Wireless Communication Technologies
###### Abstract
To this end, radio propagation measurements have been conducted in a high-building environment by using the developed UAV-based measurement system. According to the presented results, the penetration loss of direct and reflection rays was significantly underestimated in the ray-tracing simulation and the proposed method could correct the problem. [PERSON] et al. [9] focused their work on leveraging the capabilities provided by low-complexity single-antenna cooperative relays with buffers and NOMA. More specifically, an opportunistic relay selection algorithm was developed, allowing a cluster of single-antenna relays to operate in full-duplex mode through the successive relaying principle. In addition, buffering facilitated the seamless combination of half-duplex relaying with successive source broadcasting and relay transmissions, enhancing the reliability of the two-hop NOMA relay network, and lowering the delay of the transmission, while increasing the number of transmitted packets to both destinations. [PERSON] and [PERSON] [10] present a compact patch antenna backed by a conductor plane which functions as reflector, and is placed below the antenna to suppress EM radiation to the human body. The proposed antenna with an L-shape proximity feeding scheme generates a dual-resonance mode for a wide impedance bandwidth. A prototype was designed, fabricated, and compared with the conventional direct-fed patch antenna. Measured reflection coefficient and radiation characteristics of the proposed antenna agree well with the simulation results, which shows wide impedance bandwidth at 2.45 GHz ISM band for antenna working in the free space and on the human body. [PERSON] et al. [11] present a four-port MIMO antenna for 5G mmWave applications. Each MIMO antenna of the proposed design is composed of a wideband and a high gain antenna array of two elements. The operating frequency band covers 25.5-29.6 GHz, having a bandwidth of 4.1 GHz. The good radiation characteristics of the reported antenna system certify it for future devices operating in the 5G mmWave bands. [PERSON] et al. [12] focus their work on providing a generic analysis for radio network planning in the 5G era, emphasizing the need for dense standalone small-cell networks in the mmWave band of 28 GHz. According to the presented results, the area throughput is increased for dense microcell deployment. Moreover, sectored microcells double the throughput for ultra-dense networks compared to dense networks, because better interference control is achieved through the operation of one, instead of two or three, sector antennas. [PERSON] et al. [13] demonstrate a quad-element MIMO antenna for 5G mmWave applications. The operation band of the proposed antenna covers from 23 GHz to 40 GHz. The prototype of the MIMO wideband antenna was fabricated and tested. A good coherence between the experimental and simulated results is achieved. The proposed MIMO antenna operates efficiently with a significant return loss, wide bandwidth, high gain, and high element isolation, which make it a potential candidate for 5G mmWave applications. [PERSON] et al. [14] present a wideband filtering-radiating Yagi dipole antenna. An antenna prototype has been fabricated and tested. Measured results demonstrate a wide bandwidth covering from 3.64 GHz to 4.38 GHz (18.5%) and three desired radiation nulls. In addition, this antenna has the features of low profile, compact size, and easy fabrication, which will make it a good candidate for modern 5G wireless communication systems. [PERSON] et al. [15] have developed three different true-time-delay analog beamforming networks: a multi-layer Blass matrix, a Rotman lens, and a multi-layer tree topology. For each beamforming network, the design methodology as well as the analysis of electromagnetic performance have been developed separately, thereby showing their suitability for future communication systems. [PERSON] et al. [16] propose a novel antenna array architecture based on high-gain linear sub-arrays.