Millimeter-wave Technology Research Articles

An Effective Kalman Based Hybrid Beamforming for Millimeter Wave Massive MIMO System by Using 2D Overlapped Partially Connected Sub-Array Structure

In 5G mobile communication networks, millimeter-wave (mmWave) technology plays a key role. To deal with the problem of path loss that happens in the mmWave band, competent beamforming employing a large antenna array is required. Fully digital beamforming approaches currently require separate radio frequency chains (RF chains) for each antenna, which adds to the computational complexity and hardware expense. In a multi-user environment, fully digital beamforming suffers from a larger antenna array layout, whereas analog beamforming solutions are prone to numerous performance concerns. Hybrid beamforming, on the other hand, offers a promising solution for multi-user mmWave communication. This work proposes a two-dimensional overlapping partially connected (2D-OPC) sub-array structure to reduce the antenna structure's hardware complexity and cost. The suggested technique comprises several sub-arrays that are overlapped in 2D space in the form of a Uniform Planar Array (UPA). The suggested scheme's performance is assessed using Kalman-based hybrid beamforming, which exhibits a considerable increase in spectral efficiency when compared to existing hybrid beamforming techniques. The suggested technique, which uses Kalman based hybrid beamforming and 2D-OPC provides 3.14% and 4.96% improvement over the MMSE hybrid beamforming and ZF pre-coding technique respectively.

Hybrid Precoder Using Stiefel Manifold Optimization for Mm-Wave Massive MIMO System

Due to the increasing demand for fast data rates and large spectra, millimeter-wave technology plays a vital role in the advancement of 5G communication. The idea behind Mm-Wave communications is to take advantage of the huge and unexploited bandwidth to cope with future multigigabit-per-second mobile data rates, imaging, and multimedia applications. In Mm-Wave systems, digital precoding provides optimal performance at the cost of complexity and power consumption. Therefore, hybrid precoding, i.e., analog–digital precoding, has received significant consideration as a favorable alternative to digital precoding. The conventional methods related to hybrid precoding suffer from low spectral efficiency and large processing time due to nested loops and the number of iterations. A manifold optimization-based algorithm using the gradient method is proposed to increase the spectral efficiency to be near optimal and to speed up the processing speed. A comparison of performances is shown using the simulation outcomes of the proposed work and those of the existing techniques.

Vehicle Behavior-Cognition-Based Particle-Filter-Enabled mmWave Beam Tracking for Connected Automated Vehicles

Considering the low-latency and high data rate requirements for automated vehicles (AVs), the millimeter-wave (mmWave) technology can support tens of Gb/s raw sensor information sharing for connected AVs (CAVs). However, the challenging problem is how to achieve fast and robust mmWave beam tracking for CAVs. To solve this problem, we propose a novel vehicle behavior cognition-based particle-filter (VBC-PF)-enabled beam tracking algorithm. The beam-space subset is predicted based on the beam change rate and the position-yaw information from the vehicle behavior cognition in CAVs, which effectively reduces the beam search overhead. In the proposed VBC-PF algorithm, the particle weight updating schemes are designed based on the optimal vehicle behavior cognition to avoid the particle divergence and the error accumulation. Simulation and hardware testbed results verify that the accuracy and efficiency of the proposed VBC-PF algorithm outperform the conventional particle filter (PF) and the extended Kalman filter (EKF) algorithms.

Camera-Sensing-Assisted Fast mmWave Beam Tracking for Connected Automated Vehicles

The millimeter-wave (mmWave) technology can support the wide-band communication requirements for the environment raw perception information sharing to guarantee the safety of connected automated vehicles (CAVs). But, how to achieve the fast and robust mmWave beam tracking is a challenging problem in a high mobility CAVs scenario. Therefore, this article proposes a camera-sensing-assisted joint offline and online beam tracking (CS-JBT) algorithm in the mmWave frequency band. First, the mobility model is designed to predict the next moment of CAV and reduce the beam searching space overhead. In the offline learning phase of the proposed CS-JBT algorithm, the optimal beam pair under the current mobility state is obtained to guarantee the timeliness of the beam tracking process. Furthermore, to solve the mobility state deviation problem caused by the camera sensing error, the online learning phase is designed to achieve the optimal beam tracking performance efficiently for the practical scenario. Simulation and hardware testbed results verify that the proposed CS-JBT algorithm can minimize the beam tracking latency from 500 to 20 ms in contrast to the existing VBC-PF algorithm, while achieving a stable throughput over 2.5 Gb/s in the 28-GHz mmWave frequency band.

Optimal Design of Interleaved Subconnected Hybrid Structure for mmWave Massive MIMO Systems

Massive multiple-input multiple-output (MIMO) systems based on millimeter-wave (mmWave) technology commonly utilize a combination of hybrid analog and digital signal processing to reduce the number of radiofrequency (RF) chains, cutting down the hardware costs and power consumption. The subconnected structure is one of the architectures that realize hybrid analog and digital processing, in which each RF chain is connected to a subset of antennas through phase shifters so as to reduce the implementation complexity. In this paper, we investigate the best subconnected structure design for mmWave massive MIMO systems. First, we formulate the optimization problem based on a simplified connection model. Next, we derive a suboptimal solution in closed form by leveraging the mmWave channel characteristics and discuss the impact of different connection parameters on the spectral efficiency. The spectral efficiency is closely related to the structure of the analog processing and the interantenna spacing. When the interantenna spacing is an even a multiple of half wavelength, the localized structure, i.e., i = 1 achieves the maximum spectral efficiency. When the interantenna spacing is an odd multiple of half wavelength and the analog processing is accomplished by i = 2 interleaved structure, the best performance is obtained. Numerical results demonstrate the correctness of the theoretical analysis.

Transmission of 1024-QAM OFDM at 28 GHz Radio Frequency Using 5G Millimeter Wave Phased Array Antenna

We experimentally demonstrate the transmission of multiorder quadrature amplitude modulation (QAM) millimeter wave (MMW) orthogonal frequency division (OFDM) signal at 28 GHz radio frequency (RF). To overcome these unfavorable channel properties such as high path loss, propagation loss, rain fading, etc., 5G MMW phased array antenna has been used. Meanwhile, probabilistic shaping (PS) technology is applied to extend transmission distance, and Volterra nonlinearity compensation (VNC) technology is used to alleviate the system nonlinearity. Using 5G MMW phased array antennas and technologies of PS and VNC, 6.72 Gbit/s 1024-QAM OFDM signal at 28 GHz can be transmitted over 55-m wireless distance in our experiment, satisfying the normalized general mutual information (NGMI) threshold of 0.83 with 25% soft-decision forward-error-correction (SD-FEC) overhead. To the best of our knowledge, this is the first time to demonstrate the transmission of multiorder QAM OFDM signal at 28 GHz RF using 5G MMW phased array antenna.

Integrated Access and Backhaul in Millimeter-Wave Cellular: Benefits and Challenges

The recently proposed NR-ready integrated access and backhaul (IAB) architecture promises to bring a cost-efficient deployment solution for both coverage extension and capacity boosting in the emerging 5G/5G+ systems. While its impact on the coverage extension was thoroughly addressed in the literature, the effect of advanced functionalities such as multihop, multi-connectivity, and multi-beam operations on the throughput remained unclear. We review and characterize the system-level impact of these capabilities on the performance of self-backhauled IAB systems operating in half-duplex mode and utilizing millimeter-wave (mmWave) technology across both access and backhaul. Our results indicate that the throughput gain of multihopping and multi-beaming is significant even without multi-connectivity operation. Another important lesson is that in all-mmWave systems with link blockage, multi-connectivity with link switching allows achieving self-load balancing. Finally, we outline future research directions.

Millimeter-Wave Applications of MIMO Antenna

For millimetre wave technology (25GHz–30GHz), a rectangular MIMO antenna is created. The design of this antenna radiates at a frequency of 27GHz and comprises of nine numbers of cells arranged in a 3x3 array. Each unit cell has an SRR and a hexagonal patch with a Meta material substrate (MTM). The developed antenna has a gain of 3db and operates between 25 and 30 GHz. The proposed configuration has a small overall antenna size of 52 mm by 23 mm, making it simple to build.

Crystallization behavior and properties of a novel rare-earth rich BaO–SiO2–La2O3 glass-ceramic for millimeter-wave technology

In this work, a novel low permittivity and high expansion coefficient rare-earth rich BaO–SiO2–La2O3 (BSL) glass-ceramic for millimeter-wave technology was systematically investigated by the network structure, crystallization the phase transformation, microstructure and microwave dielectric properties. With the decrease of the SiO2/BaO mol ratio from 3.75 to 0.9, the crystallization activation energy (Ec) of BSL glass calculated by the Kissiger equation continued to fall from 400.65 to 316.85 kJ/mol, and the crystal growth mode of all samples judging by Avrami parameter (n) was 1-D volume crystallization, implying that the crystallization ability of the BSL glass was enhanced. The main crystal phase of BSL glass-ceramic transformed from BaSi2O5 to BaSiO3 phase, coincided with a second phase Ba4La6O(SiO4)6. And then, the relative permittivity εr of BSL glass-ceramic had increased from 7.8 to 11, while quality factor (Q × f), temperature coefficient of frequency τf, and coefficient of thermal expansion (CTE) had decreased with the decrease of SiO2/BaO ratio. By adjusting the mol ratio of SiO2/BaO, the best comprehensive properties of 20BaO–75SiO2–5La2O3 glass-ceramic could be obtained with εr = 7.8, Q × f = 21000 GHz, CTE = 12.39 × 10−6/°C (30–800 °C), which was favorable properties for microwave dielectric applications.

Semi-Deterministic Dynamic Millimeter-Wave Channel Modeling Based on an Optimal Neural Network Approach

Billions of mobile terminals will be deployed in various Internet of Things (IoT), in which millimeter-wave (mmWave) technology will be gradually applied. Accurate modeling and simulation of wireless channel is the base for efficient design and performance evaluation. This becomes more important for industrial scenarios, which might be highly dynamic and potentially different from well-investigated cellular deployment scenarios. In this work, a novel semi-deterministic mmWave dynamic channel modeling approach based on optimal neural network (ONN) principle is proposed. The ONNs are radial basis function (RBF) neural networks (NNs) trained with optimal variance parameters and are applied to predict large-scale channel parameters (LSCPs) [e.g., path loss (PL), delay spread (DS), and angle spread (AS)]. Based on the ONNs’ predicted large-scale parameters and simplified propagation environment including the layout of transmitter (TX), receiver (RX), and major scatterers, the proposed channel modeling approach can generate accurate dynamic channel parameters. The proposed approach is validated by the channel data measured at a high-voltage substation. Large-scale parameters, multipath component (MPC) distributions, and power delay profiles (PDPs) are validated. The proposed approach is demonstrated to be an accurate, fast, and robust channel modeling method, which can be used for both link-level and system-level channel simulation for future design and optimization of industrial IoT.

MAC Protocols for mmWave Communication: A Comparative Survey.

With the increase in the number of connected devices, to facilitate more users with high-speed transfer rate and enormous bandwidth, millimeter-wave (mmWave) technology has become one of the promising research sectors in both industry and academia. Owing to the advancements in 5G communication, traditional physical (PHY) layer-based solutions are becoming obsolete. Resource allocation, interference management, anti-blockage, and deafness are crucial problems needing resolution for designing modern mmWave communication network architectures. Consequently, comparatively new approaches such as medium access control (MAC) protocol-based utilization can help meet the advancement requirements. A MAC layer accesses channels and prepares the data frames for transmission to all connected devices, which is even more significant in very high frequency bands, i.e., in the mmWave spectrum. Moreover, different MAC protocols have their unique limitations and characteristics. In this survey, to deal with the above challenges and address the limitations revolving around the MAC layers of mmWave communication systems, we investigated the existing state-of-the-art MAC protocols, related surveys, and solutions available for mmWave frequency. Moreover, we performed a categorized qualitative comparison of the state-of-the-art protocols and finally examined the probable approaches to alleviate the critical challenges in future research.

Millimeter-Wave Phased Arrays and Over-the-Air Characterization for 5G and Beyond: Overview on 5G mm-Wave Phased Arrays and OTA Characterization

Millimeter-wave (mm-wave) technology is a viable candidate to address the growing data traffic in 5G wireless communication and beyond. However, challenges related to free-space propagation loss, atmospheric absorption, scattering, and nonline-of-sight propagation must be addressed to benefit from the promised bandwidth available in the mm-wave regime. In this context, phased-array technology is considered vital to provide high-speed and seamless wireless solutions to the industry. A phased array can be defined as a multiple-antenna system that electronically controls the radiated electromagnetic (EM) beam. The official origin of the antenna array concept is attributed to Guglielmo Marconi. A repeated Morse code signal letter “S” from Poldhu, United Kingdom to St. John’s in Canada was successfully demonstrated in December 1901, using a two-element antenna array. In the early 1940s, Luis Walter Alvarez designed the first electronically scanning phased-array radar. Both scientists were awarded the Nobel Prize for their discovery.

Effects of cerium doping on the microstructure, mechanical properties, thermal conductivity, and dielectric properties of ZrP2O7 ceramics

A two-step method, combined with cold isostatic pressing, was used to prepare CeO2-doped ZrP2O7 ceramics, and their microstructure, mechanical properties, thermal conductivities, and dielectric properties were determined. It was found that CeO2 doping could increase the Zr–P and P–O bond lengths, which in turn decreased the thermal conductivity of the ZrP2O7 matrix. Doping with 12 wt% CeO2 simultaneously reduced the sintering temperature and improved the mechanical properties of the ZrP2O7 ceramics, while retaining its low thermal conductivity and good dielectric properties. The maximum cold modulus of rupture of a sample at 1250 °C was 75.91 MPa, which met most conditions for use at room temperature. A COMSOL model was used to predict the thermal conductivity, based on the microstructure, with a relatively high degree of accuracy. The thermal conductivity of the CeO2-doped samples was lower than 1.083 W/(m·K). The dielectric constant was in the range of 5.93–6.52 at 20–40 GHz, and the dielectric loss was less than 4 × 10−3. The ZrP2O7-doped ceramics have potential for application in millimetre wave technology, satellite communication, and vehicle radar fields, because they can meet the high thermal insulation requirements for these applications.

Imaging Diagnostics of Inside of a Building Wall Using Millimeter-Wave Reflectometer

Progress in microwave and millimeter-wave technologies has enabled advanced diagnostics for industrial applications. The transmission, reflection, scattering and radiation processes of electromagnetic waves are utilized as diagnostic principles. Specifically, the reflectometric method has gained importance in various applications due to the possibility of the high localization and accessibility of measurements, as well as the non-destructive nature of the systems. In this paper, radar reflectometers were applied to the measurement of the inside of a building wall, that is, the inspection of tile materials attached to a concrete wall. The measurement principle utilizes the phase interference effect of the reflected wave due to the multiple reflections between the two layers (Fabry–Perot effect). The results show the imaging inside the surface related to the peering condition between the tile and concrete wall, and the quantitative evaluation of the condition with non-destructive inspection.

Gradient Ascent Algorithm for Enhancing Secrecy Rate in Wireless Communications for Smart Grid

The emerging Internet of Things (IoT) and bidirectional communications in smart grid are expected to improve smart grid capabilities and electricity management. Because of massive number of IoT devices in smart grid, size of the data to be transmitted increases, that demands a high data rate to meet the real-time smart grid communication requirement. Sub-6 GHz, millimeter-wave (mmWave) technologies, and massive multiple-input multiple-output (MIMO) technologies can meet high data rate demands. However, IoT enabled smart grid is still subject to various security challenges such as eavesdropping, where attackers attempt to overhear the transmitted signals and the jamming attack, where the attacker perturbs the received signals at the receiver. In this paper, our goal is to investigate jamming and eavesdropping attacks while improving secrecy capacity for smart grid communications. Specifically, we propose to employ a hybrid beamforming design for wireless communications in smart energy grid. In previous works, the secrecy capacity is increased by randomly augmenting the source power or setting the system combiners. Unlike state-of-the-art, we design and evaluate the Gradient Ascent algorithm to search for the best combiners/waveform that maximizes the secrecy capacity in smart grid communications. We also study two different optimization scenarios by considering both fixed and variable transmit power. Numerical results are used for performance evaluation and supporting our formal analysis.

Toward Advanced UAV Communications: Properties, Research Challenges, and Future Potential

In recent times, communication and connectivity requirements have been evolving rapidly, and it is evident with the recent deployment of fifth-generation (5G) cellular networks worldwide. Similarly, unmanned aerial vehicles (UAVs) have gained interest in several applications, including surveillance, monitoring, geographic mapping, and logistics, among others. Therein, 5G cellular network support for UAVs is gaining both attention and momentum within various regulatory bodies and consortiums. While 5G is gaining momentum to establish necessary communication technologies for UAV operations, we provide a state-of-the-art overview emphasizing the technical challenges of applying millimeter-wave technology to support UAV communication. This article provides a closer look at the key enabling technologies and their potential issues impacting UAV operation under a unifying 5G network and beyond. In addition, this article also discusses the security issues impacting network privacy and safety vulnerabilities of UAVs. To conclude, we identify several open research issues that drive UAV deployment and operations and demand further study.

A Novel Fairness Allocation Strategy With Minimum Mainlobe Interference for mmWave Networks

In the fifth-generation (5G) communication system, millimeter-wave (mmWave) technology brings superior capabilities, such as higher capacity, lower latency, and a flexible beamforming structure. The interference management strategies play an important role in mmWave beamforming networks to support the multibeam operation and maximize the overall data rates for user equipments (UEs). Currently, most of the existing research do not jointly consider designs, including the mainlobe interference (MI) avoidance and resource blocks (RBs) fairness allocation. In this article, a novel fairness allocation strategy is proposed to achieve the minimum MI and a fair RB assignment for mmWave networks. To achieve the minimum MI, an MI mitigation (MIM) algorithm is designed to maximize the data rate for each UE. With the adaptive mini-timeslot design, the MIM algorithm can achieve MI cancelation for all UEs at each identical timeslot and beam. To combine MIM and fairness for RB allocation among all UEs, the MIM-fairness allocation (MIM-FA) algorithm is also presented. Based on a novel mini-timeslot with designed multiple frames, the MIM-FA algorithm can simultaneously guarantee the fairness among all UEs and mitigate MI at each mini-timeslot for each beam. Additionally, the MIM-FA algorithm can be verified that it achieves the maximum user data rate with the identical number of RBs under the lowest number of frames. Simulation results validate that the proposed MIM and MIM-FA algorithms can provide a higher data rate and better fairness for different scenarios compared to current state-of-the-art competitive approaches.

A Novel Mining Approach for Data Analysis and Processing Using Unmanned Aerial Vehicles

In the mining industry, smart surveying and exploration operations for the minerals are essential during mining missions. Usually, these missions are performed in remote areas that do not have a wireless communications infrastructure. This paper proposes to use the unmanned aerial vehicle (UAV) as a relay communication node between the exploration team and the ground control station (GCs). UAV can act as a relay node to provide mobile, flexible, and reliable communication links in remote environments and complex topologies. In this work, the pathloss models in millimeter‐wave technology are considered because they provide massive data rates for line of sight scenarios. The optimization problem of identifying a 3D location and trajectory of the UAV relay node is formulated to maximize the total team members’ data rate. Because the problem is non‐convex, the particle swarm optimization algorithm is used to solve it and determine an efficient location and trajectory of the UAV.

An investigation on fronthaul and millimeter wave technologies for 5G

.The growing demand for communications and the emergence of new applications have put the capacity, transmission rate and latency of communications systems to a more severe test. In this context, 5G communication technology has emerged. 5G applications are divided into three typical application scenarios: eMBB, URLLC and mMTC. In order to support these applications, the key technologies of 5G need to be studied in depth. This paper firstly investigates the networking architecture of 5G bearer networks, and carries out a detailed analysis and comparison of 5G fronthaul technology, including the optical fibre direct connection solution, passive WDM solution, active WDM/OTN solution and WDM-PON solution. Secondly, this paper introduces 5G millimetre wave technology to achieve large capacity and high spectral efficiency transmission, including direct intensity modulation method, external modulation method, optical heterodyne method, optical injection locking method and optical phase-locked loop method. Finally, this paper provides an outlook on 5G fronthaul technology and millimetre wave technology.

A Dual-Array Antenna System for 5G Millimeter-Wave Applications

Millimeter-wave (mm-Wave) technology has opened a new era of wireless communication systems in various fields like automotive, mobile devices, Internet of Things (IoT), military, medical, and others. The benefit of adopting the unconventional frequency spectrum of large bandwidth under an mm-Wave spectrum is the availability of large bandwidth and lesser chances of interferences from various technologies. In the recent 5G communication systems either cellular or other wireless applications, many researchers have focused on mm-Wave antennas and arrays. In this paper, a dual-array antenna system is designed for various 5G mm-Wave wireless applications. It has two arrays on the same substrate edges with a series feed line compact technique. The profile antenna system has two 1×16 arrays on the same substrate edges. Each array gives 17.3 dB and 16.4 dB simulated and measured gains and impedance bandwidth 31.30 GHz to 39 GHz at 38 GHz center frequency. The feature to use both arrays at the same time for two different applications within the operational band for same or different center frequencies makes this proposed dual-array antenna system a good candidate for 5G mm-Wave wireless IoT and broadcast applications.