Wireless Communication Industry Research Articles

Investigating enhanced electrical conductivity for antenna applications through dual metallization on 3D printed SLA substrates

The advancement of 3D printing (additive manufacturing) has gained interest in variety of applications, especially for antenna fabrication. The demand for cheap, reliable, and high-performance antenna fabrication methods is essential in order to cope with the demand of wireless communications industry. In this work, the focus was emphasized on enhancing the electrical conductivity of the 3D printed substrates fabricated by stereolithography (SLA) 3D printer. The 3D printed substrate went through a dual metallization approach, involving sputtering and electrodeposition techniques for the fabrication of conductive metal layers. The parameters for the sputtering were fixed for all the substrate while current density during electrodeposition process was varied at 25 %, 50 %, 75 % and 100 % from recommended value of current. The results showed that the current density during the electrodeposition determined the conductivity performance of the metal layers and established a significant correlation with the surface morphological. Three different frequencies comprised of 2.4 GHz, 3.5 GHz and 5.0 GHz were selected to simulate and fabricate a microstrip patch antenna using the optimized current density which was valued optimal at 75 % (52.5 mA). The percentage of accuracy between simulated and measured frequencies of antenna, portrayed that the measured values were slightly higher than the simulated approximately about 5.14 to 6.67 %. Therefore, the integration of additive manufacturing or 3D printing techniques for antenna could address the critical necessity for fast and economical solution in wireless systems.

Engineering designed functional covalent organic frameworks via pore surface modifications for effectively reducing the dielectric constant of polyimide-based electronic packaging materials

Polyimide (PI) is considered one of the most promising candidate materials for the microelectronics and wireless communication industries. Nevertheless, the relatively high dielectric constant of PI has become a significant obstacle, constraining its utilization in the realm of microelectronics. Herein, novel PI nanocomposite films were fabricated by incorporating covalent organic frameworks (COFs) and their functionalized counterparts (COF@POSS and COF@DTF) through post-synthetic modification. Among all PI nanocomposites films, PI/COF@POSS nanocomposite film including 2 wt% COF@POSS achieved the lowest dielectric constant (2.41) and dielectric loss (0.0076). These values represented a reduction of 22.5 % and 24 % compared to pure PI, respectively. The decrease in dielectric constant is ascribed to the combined influence of the porous structure of COF and the augmentation in free volume fraction caused by the steric hindrance of POSS. Additionally, the tensile strength of the PI/COF@POSS and PI/COF@DTF nanocomposite films increased up to 121.1 MPa and 112.0 MPa, representing a 95 % and 80 % improvement over pure PI, respectively. Furthermore, the introduction of COFs functionalized with POSS and DTF significantly enhanced the hydrophobicity of PI nanocomposite films. The combination of porous organic nanofillers with surface functionalization offers a feasible route to create low-k PI nanocomposite films with improved mechanical properties and hydrophobicity.

Deployment of efficient MANET testbed using aggregation based archive population optimization

In today’s 6G era, Mobile ad hoc networks (MANETs) have been enhanced by rapid technological advancement in the wireless communication industry to better support a wide range of domains, including military operations, emergency operations, urban settings, and natural crisesmanagement. In MANET, self-organizing mobile nodes collaborate to build a flexible network architecture. With a MANET, data must transit through numerous intermediate nodes even before reaches its destination node. Local link connectivity is essential for the establishment and preservation of routes. To decrease energy usage, these findings suggest the Aggregation-based Archive Population Optimization(AAPO) along with Ad-hoc On-demand Distance Vector (AODV) Routing Protocol. For both local and global optimal routes, the proposed optimized modelgives top priority. There existtwo different types of rules used by AAPO to evaluate the quality of a route before using it for data transmission. Instead of relying on just one path for transmitting data, AAPO leverages many paths. Also, it minimizes the issue of the network nodes being suddenly inaccessible, which eliminates interruptions in transmissions. However, the suggested optimal routing system considers mobility and energy availability when responding to queries, resulting in significant performance improvements, utilizing 42.69 % of the scenario’s power and functioning at 208.6 kbps with an average PDR of 87.1 %. Also, detailed simulations are conducted using the Matlab (R2021b)software to assess the suggested approach. Furthermore, the suggested protocol outperforms the current methods in terms of effectiveness.

Enhanced Wireless Network Usage and Loading on Network Delay using Cognitive Radio Network

Wireless communication is one of the fastest-growing fields of communication. Because the user can access and share information anywhere at any time. The communication process will suffer from an overload of traffic. If the node gets overloaded because of heavy traffic, then the performance of the whole network is degraded. So, the usage of the network will be delayed. The proposed work uses the intellectual load balancing approach for Cognitive Radio Network to focus on automatic monitoring of network activity, and the node will continuously balance among numerous nodes. In Cognitive Radio Network the Dynamic Spectrum Access techniques are used to avoid spectrum scarcity and underutilization. The CR base station collect the surrounding about the active primary user and waiting secondary user. To determine the principal user's on/off status of availability, the Markov chain model is employed. The waiting secondary user utilize the spectrum when the primary user is not using it. The secondary user leaves the spectrum and uses the spectrum of another primary user if the primary user is on status. It will assist with dynamic spectrum access method and it will help increase the overall performance of the network. The suggested Load balancing Cognitive Radio Network (LBCRN) sorts the nodes and uses spectrum identification before allocating the node to the secondary user. So that minimise transaction delays, prevent overcrowding of a specific node, automatically lower the level of packet drops, and enhance packet delivery radio levels. As a result, this strategy has helped to lessen the issue of spectrum shortages in the wireless communication industry.

Fifth Generation Non-Standalone to Standalone Wireless Architecture Reconstruction Solution and Implementation: South Africa Context

The wireless mobile communication industry has evolved immensely over the past five decades, starting from the voice-centric 1G technology to the current data-centric 5G technology because of the increasing data traffic and the need for higher data speed rates. To provide the initial experience of 5G technology, many network operators worldwide started their deployment with the Non-Standalone (NSA) solution to mainly reduce the cost and time. 5G NSA solution already provides lower latency, higher network capacity, and bandwidth compared to the legacy network, however, there is growing oncern about its reliance on the 4G core network, capability, and the long-term migration plan to 5G Standalone (SA) network solution. This paper discusses a brief review of 5G evolution, standardization formulation, deployment strategies, security enhancement, challenges, and presents the reconstruction of 5G NSA to SA solution implementation. Furthermore, a 5G field test will be performed to analyze the user experience under the NSA NR in South Africa, and key practical challenges facing the South African MNOs from the perspective of business and technical challenges will be discussed with recommendations.

Review on filtering antenna technology for 5G mobile system

In recent years, people’s increased demand for wireless communication technology fuels the development of 5G communication technology growth. Electronic equipment in the current wireless communication system is developing in the direction of low power consumption, multi-function, miniaturization, and integration, which also puts higher technical standards for RF front-end. In recent years, the wireless communication industry is building lighter, thinner, and smaller products with multifunction. The integration of filter and antenna is one of the important ways for the miniaturization of electronic systems. The antenna and filter are integrated to form a filtering antenna, which can effectively reduce the size and weight of the RF front end while realizing the function of radiation and filtering. This paper first introduces the research background and significance of this topic according to the background of mobile communication technology, and the main challenges faced by 5G communication. Then, the working principle of filtering antenna and multiple-input multiple-output technology (MIMO) are introduced, and finally the development and research status of 5G filtering antenna are summarized, and some relevant personal views are put forward.

Transfer Learning in Natural Language Processing (NLP)

Purpose: The purpose of this study is to address the limited use of transfer learning techniques in radio frequency machine learning and to propose a customized taxonomy for radio frequency applications. The aim is to enable performance gains, improved generalization, and cost-effective training data solutions in this specific domain.
 Methodology: The research design employed in this study involves a comprehensive review of existing literature on transfer learning in radio frequency machine learning. The researchers collected relevant papers from reputable sources and analyzed them to identify patterns, trends, and insights. The method of data collection primarily relied on examining and synthesizing existing literature. Data analysis involved identifying key findings and developing a customized taxonomy for radio frequency applications.
 Findings: The study's findings highlight the limited utilization of transfer learning techniques in radio frequency machine learning. While transfer learning has shown significant performance improvements in computer vision and natural language processing, its potential in the wireless communications domain has yet to be fully explored. The customized taxonomy proposed in this study provides a consistent framework for analyzing and comparing existing and future efforts in this field.
 Recommendations: Based on the findings, the study recommends further research and experimentation to explore the potential of transfer learning techniques in radio frequency machine learning. This includes investigating performance gains, improving generalization capabilities, and addressing concerns related to training data costs. Additionally, collaborations between researchers and practitioners in the field are encouraged to facilitate knowledge exchange and foster innovation. Practice: To practitioners in the field of radio frequency machine learning, this study emphasizes the potential benefits of incorporating transfer learning techniques. It encourages practitioners to explore the application of transfer learning in their specific domain, leveraging prior knowledge to enhance performance and address training data challenges. It also highlights the importance of staying informed about the latest developments and collaborating with experts in the field. Policy: To policy makers, the study underscores the need for supportive policies that promote research and development in radio frequency machine learning. It recommends creating an environment that fosters innovation, encourages collaborations between academia and industry, and provides resources and incentives for further exploration of transfer learning techniques. Policy makers should consider the potential impact of transfer learning on the wireless communications industry and support initiatives that enhance its adoption and implementation.

On the secure performance of Internet of Vehicles in Nakagami-m fading scenarios

With the vigorous development of today’s wireless communication industry, the Internet of Vehicles (IoV), as one of its application scenarios, has received extensive attention from researchers. Ensuring the security of information transmission is one of the many problems to be solved in the IoV system. To fit the actual scene, this paper considers the impacts of both the channel characteristics of Nakagami-m fading and the distribution of the vehicles’ positions in the real road scenario of the IoV. According to the random distribution characteristics of vehicle terminal position, a system model with a transmitter base station, a legitimate vehicle terminal, and an eavesdropper is established. The approximate and asymptotic analytical expressions of the secrecy outage probability over the Nakagami-m fading channels are derived. Finally, the correctness of the proposed analysis models established in this paper is verified by Monte Carlo simulation and numerical analysis. The secrecy outage performance and the influencing factors of the considered model in the Nakagami-m fading environment are discussed and analyzed.

CPW Fractal Antenna with Third Iteration of Pentagonal Sierpinski Gasket Island for 3.5 GHz WiMAX and 5.2 GHz WLAN Applications

Nowadays, the compact and multiband antennas are typically required for personal communication devices in the continuously developing wireless communication industry. The fractal antenna with the third iteration of the pentagonal Sierpinski gasket island for WiMAX and WLAN applications is presented in this work. It starts with the fundamental design of the square patch (Antenna A1) and pentagonal patch (Antenna A2). This simulation work is done using CST Microwave Studio simulation studio by applying the concept of the zero, first, second and third fractal iteration. Then, it goes on to use the fractal geometry concept of the Sierpinski gasket island structure with three designs step. The designs consist of the first iteration (Antenna B1), second iteration (Antenna B2) and third iteration (Antenna B3) of fractal geometry. The simulation work of Antenna B3 is compared with the fabrication work of the same design. After that, the measurement of the Antenna B3 is done in laboratory with - 29.55 dB at 3.41 GHz and - 20.40 dB at 5.28 GHz for its operating frequencies with bandwidth of 3.52 GHz and 5.48 GHz, respectively. At targeting 3.5 GHz WiMAX, 5.2 GHz WLAN application and 7.24 GHz of Antenna B3, the antenna shows the – 17.78 dB, - 29.63 dB and – 22.73 dB, respectively, and this value is feasible for WiMAX and WLAN operation.

A low profile dual band dual C - shaped monopole antenna for Wi-Fi, WiMAX and WLAN applications

This article presents a low-profile dual-band, dual C-shaped monopole antenna designed for Wi-Fi, WiMAX, and WLAN applications. The simulated results demonstrate that the proposed antenna achieves a 10 dB return loss and an impedance bandwidth ranging from 2.3–3.0/2.5 GHz and 4.1–6.0/5.1 GHz. The antenna configuration consists of two Cshaped branches, one inverted to the other, along with a ground plane. This design enables the antenna to generate two resonant frequencies while maintaining good radiation patterns and gain characteristics. Simulations were conducted on an FR-4 Epoxy substrate, resulting in a compact, low-profile size of 38×26×0.8 mm3. The obtained impedance bandwidth is 28% for the 2.5 GHz frequency range and 37.25% for the 5.1 GHz frequency range. Additionally, the simulated gain is reported as 3.5 dBi for 2.5 GHz and 3.0 dBi for 5.1 GHz. The proposed antenna offers a compact size, dual-band operation, wide impedance bandwidths, and reasonable gain levels, making it well-suited for Wi-Fi, WiMAX, and WLAN applications. Its design ensures efficient performance, allowing reliable wireless communication in the desired frequency bands. With its small form factor, the antenna can be easily integrated into various devices while maintaining excellent radiation patterns and achieving the desired impedance matching. Overall, the proposed antenna presents a promising solution for dual-band applications in the wireless communication industry.

Cross-Tier Interference Mitigation in 3D HetNets for LTE and Wi-Fi Access

Due to the unprecedented rate of transformation in the field of wireless communication industry, there is a need to prioritise the coverage, network power and throughput as preconditions. In Heterogeneous Networks (HetNets) the low power node inclusion like Femto and Pico cells creates a network of Multi-Tier (M-Tier) which is regarded as the most significant strategy for enhancing the coverage, throughput, 4G Long Term Evolution (LTE) ability. This work mainly focuses on M-Tier 3D Heterogeneous Networks Energy Efficiency (EE) based Carrier Aggregation (CA) scheme for streaming real-time huge data like images. At first, M-Tier 3D HetNets scheme was made for investigating Signal to Noise Interference Ratio (SNIR) on assessing the collective Pico-tier and Femto-tier interference. Next, the scheme of channel allocation is scrutinised so as to estimate throughput from the multiple tiers. Additionally, with the use of CA technique, the problem of energy efficiency for M-Tier 3D Heterogeneous Network (HetNet) in relation to energy metrics and throughput was evaluated with the use of LTE and Wireless Fidelity (Wi-Fi) coexistence. The simulation is carried out in a MATLAB setting, and the outcomes reveal a huge impact on EE. The simulation is carried in terms of EE, transmission time, throughput, packet success rate, convergence probability, and coverage region. The analysis from simulation shows that on improving the output of the device, interference among small cell base stations is reduced on increasing EE. The outcomes attained aid in the effective creation of M-Tier 3D HetNets for enhancing EE by employing Multi-Stream Carrier Aggregation (MSCA) in HetNets.

A survey on the integration of visible light communication with power line communication: Conception, applications and research challenges

The extensive enhancement of wireless communication industry over the last decade revolutionized the change of our daily life. In this scenario, it becomes utmost difficult for the network providers to cater the needs of the end users. Consequently, this mandates the necessity to rely on alternative communication-based technologies. Therefore, one such communication is visible light communication (VLC) which is regarded as a promising complement to radio frequency (RF) based wireless communication. The renowned nature of VLC is that it renders simultaneous illumination and communication by utilizing light emitting diodes (LEDs). However, VLC by itself cannot be employed directly as an information source. Therefore, this necessitates for VLC to be connected to a backhaul network to furnish communication. Based upon these grounds, power line communication (PLC) turns out to be the most feasible communication technology which reinforces as an excellent communication backbone for VLC systems. Predominantly, the inherent benefit offered by the integrated PLC–VLC systems is that the existing power line infrastructure can be leveraged to supply power to the LED, while the energy-efficient LED-based illumination systems render wireless support. Accordingly, this paper presents a comprehensive review of the integrated PLC–VLC systems, physical layer aspects which includes detailed study on PLC–VLC channel modeling and modulation techniques. In addition, this survey focuses in detail on the multiple access techniques and clearly discusses several technical aspects that are associated with the cascaded PLC–VLC systems as well as highlights the current state-of-the-art research aspects in the directions of hybrid PLC-VLC-RF systems. Additionally, this survey outlines the societal applications of PLC–VLC systems which includes the applications of PLC–VLC in hospitals, aircrafts, military, Internet of Things (IoT) devices, etc., as well as summarizes the challenges that are of paramount important while designing high speed integrated PLC–VLC systems.

Dual-Band Design Techniques for Microwave Passive Circuits: A Review and Applications

The introduction of new technology in the wireless communication industry increases the number of frequency bands in the communication environment. Therefore, a communication system capable of functioning over several frequency bands, known as a <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">multiband communication system</i> , is required. In addition, multiband communication systems support technology upgrades by smoothly bridging the migration from the existing technology to a newer technology. A multiband communication system can be developed with the help of two approaches. The first approach is a multiband communication system that contains multiple microwave circuits, with each circuit optimized for a single band; for example, a dual-band communication system has two low-pass filters and two power amplifiers. But this approach increases not only the size but also the cost of the system. In the second approach, rather than using a separate power amplifier and filter for each frequency band, a single power amplifier, filter, and other components are used that can support more than one frequency band. These circuits are known as <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">multiband microwave circuits</i> . Multiband circuits not only minimize size but also reduce the cost of designing the multiband communication system.

Ultra-Low Loss Mg2TiO4 Based Dielectric Ceramics for Microwave Applications: An Overview

For several decades, temperature stable, medium permittivity, and low loss dielectric ceramics have been used as resonators, oscillators, filters, and GPS patch antennas for microwave communication systems. Various microwave dielectric ceramics have been proposed and widely used in telecommunication industries. Among the most interesting materials of that kind, magnesium orthotitanate (Mg&lt;sub&gt;2&lt;/sub&gt;TiO&lt;sub&gt;4&lt;/sub&gt;) is recognized as one of the most promising low loss microwave materials, which played an important role in the field of microwave and millimeter wireless communication industry. It was found that by modifying the Mg&lt;sub&gt;2&lt;/sub&gt;TiO&lt;sub&gt;4&lt;/sub&gt; compound with other materials, their microwave dielectric properties have changed tremendously. The main purpose of this review is to gather information about Mg&lt;sub&gt;2&lt;/sub&gt;TiO&lt;sub&gt;4&lt;/sub&gt; - based low loss dielectrics used for microwave applications. The study also helps the researchers and technologists to get compact information for Mg&lt;sub&gt;2&lt;/sub&gt;TiO&lt;sub&gt;4&lt;/sub&gt; -based compounds all over the world.

Preparation of Low-k Poly(dicyclopentadiene) nanocomposites with excellent comprehensive properties by adding larger POSS

Low dielectric constant (low-k) polymer nanocomposites with good comprehensive properties are essential for microelectronics and wireless communication industry. Although extensive studies show that incorporation of polyhedral oligomeric silsesquioxane (POSS) is an effective strategy to realize this purpose, nearly all of them are based on T8 POSS and the influence of larger POSSs (i.e., T10 and T12 POSS) on polymer’s properties remains unclear. Herein three vinyl POSSs (T8V8, T10V10, and T12V12) with increased sizes were introduced into poly(dicyclopentadiene) (PDCPD) for preparation of high-performance low-k nanocomposites. Because these three POSSs are soluble in dicyclopentadiene monomer, a series of nanocomposites with molecular scale POSS dispersion were achieved after thermo-crosslinking. The results show that the k value of PDCPD can be decreased not only by increasing the content of these three POSSs but also by altering the POSS size. Consequently, the k value of PDCPD at 1 kHz was found to be reduced from 2.54 to 2.10 by adding high content of larger POSS (i.e., 7 wt% of T12V12) without damaging its inherent low dielectric loss. This result highlights the rule of POSS size and POSS content on the dielectric properties and could be used to predicate ultralow-k polymer nanocomposites by extrapolating to larger POSS and higher POSS content. Meanwhile, the comprehensive properties of PDCPD such as glass transition temperature, dimensional stability, mechanical properties, and hydrophobicity, are able to be enhanced by altering the POSS size and increasing the POSS content, making these resulting nanocomposites become useful materials for future microelectronic industry.

Composition tunable manganese-doped magnetite microwave absorber composites for radio frequency identification communication

The performance of radio frequency identification (RFID) tags deteriorates in transmitting/receiving characteristics when the tags are mounted on conductive substances such as metals due to the interference from the metal reflected electromagnetic waves. In this work, the manganese-doped magnetite (MnXFe3−XO4 (0 ≤ X ≤ 1)) nanoparticles with different manganese contents are synthesized by the one-pot sol-gel method for the application of microwave absorber. The effects of Mn doping on the morphology, microstructure, dielectric and magnetic properties, and microwave absorption ability of MnXFe3−XO4 nanoparticles are investigated. The saturation magnetization and dielectric and magnetic losses of MnXFe3−XO4 nanoparticles enhance as the Mn doping increases, and achieve the maximum when X = 0.50, and decrease as the Mn doping further continues to augment. At the optimized value of X = 0.50, the reflection and transmission losses are measured to be 17.51 and 3.88 dB, respectively. Furthermore, the nanoparticles are mixed with polytetrafluoroethylene powder and hot-pressed into a composite mat to demonstrate its application as microwave absorber. When the composite mat is inserted between the RFID tag and metal surface, the RFID tag recovers the read count by 86%, which is due to the high absorption ability (80.77%) of the composite mat. Therefore, the composition tunable MnXFe3−XO4 nanoparticles can be a potential candidate for the application of microwave absorber in wireless communication and electronic industries.

Sensing and analysis of spectrum holes in ISM band using USRP testbed

The spectrum frequency in the wireless communication industry is getting great attention due to the internet of things (IoT) technology's growth. However, the radio spectrum's frequency band use is limited because the primary user for specific services can cause spectrum interference as multiple users use the same spectrum frequency. Meanwhile, at each spectrum frequency, the number of users and utilization time are distinct. These will create vacancies for spectrum frequency assigned to the primary user. A new alternative in using the cognitive radio (CR) spectrum is accessible to these vacancies. This paper analyzed the frequency spectrum in the industrial, scientific and medical (ISM) band and identified spectrum holes for transmission by the secondary users. This work employed a realistic approach by measuring the spectrum using Universal Software Radio Peripheral (USRP) devices. Thus, the spectrum holes in the frequency spectrum had distinguished by using an energy detection technique. In the energy detection technique, the threshold energy level is set and then compared with the energy detector output to identify the primary user's existence (PU). The result indicates that 0.61% of spectrum holes have been detected in the 2.43-2.44 GHz range. This range is sufficient for home appliances, radio frequency peripherals (RF), and bluetooth devices.

Physical Layer Security Analysis of Hybrid MIMO Technology

MIMO is a key enabling technology in the currently emerging 5G systems and future 6G-plus paradigms, such as heterogeneous networks, millimeter-wave networks, vehicular sensor networks, among others. The highly desired properties of MIMO such as its ability to supporting high data rates, improving energy and spectral efficiency, as well as overcoming the effects of shadowing and fading have made it increasingly attractive to the wireless communications industry. Nevertheless, a practical secure MIMO model with the required security levels to guarantee user information protection has still not been realized by the industry. In this work, we analyze and quantify the security performance of hybrid MIMO, which was originally proposed by the preceding work titled “Hybrid MIMO: A New Transmission Method For Simultaneously Achieving Spatial Multiplexing and Diversity Gains in MIMO Systems”. In the proposed method, special signal interference-canceling matrices, which are calculated based on the channel’s variations and randomness between the user and receiver, are superimposed with user data at the physical layer level before being transmitted to the receiver. The conducted performance analysis in this study indicates that the signal interference-canceling matrices provide absolute security (zero information leakage) against both internal and external eavesdroppers. Moreover, the new MIMO technique eliminates the need for any processing at the receiver, where users directly receive their intended signals, consequently lowering complexity and power consumption at the receiver. These are highly desirable properties for the future internet of things (IoT) devices as well as 6G and beyond technologies.

The Protective Effects of EMF-LTE against DNA Double-Strand Break Damage In Vitro and In Vivo.

With the rapid growth of the wireless communication industry, humans are extensively exposed to electromagnetic fields (EMF) comprised of radiofrequency (RF). The skin is considered the primary target of EMFs given its outermost location. Recent evidence suggests that extremely low frequency (ELF)-EMF can improve the efficacy of DNA repair in human cell-lines. However, the effects of EMF-RF on DNA damage remain unknown. Here, we investigated the impact of EMF-long term evolution (LTE, 1.762 GHz, 8 W/kg) irradiation on DNA double-strand break (DSB) using the murine melanoma cell line B16 and the human keratinocyte cell line HaCaT. EMF-LTE exposure alone did not affect cell viability or induce apoptosis or necrosis. In addition, DNA DSB damage, as determined by the neutral comet assay, was not induced by EMF-LTE irradiation. Of note, EMF-LTE exposure can attenuate the DNA DSB damage induced by physical and chemical DNA damaging agents (such as ionizing radiation (IR, 10 Gy) in HaCaT and B16 cells and bleomycin (BLM, 3 μM) in HaCaT cells and a human melanoma cell line MNT-1), suggesting that EMF-LTE promotes the repair of DNA DSB damage. The protective effect of EMF-LTE against DNA damage was further confirmed by attenuation of the DNA damage marker γ-H2AX after exposure to EMF-LTE in HaCaT and B16 cells. Most importantly, irradiation of EMF-LTE (1.76 GHz, 6 W/kg, 8 h/day) on mice in vivo for 4 weeks reduced the γ-H2AX level in the skin tissue, further supporting the protective effects of EMF-LTE against DNA DSB damage. Furthermore, p53, the master tumor-suppressor gene, was commonly upregulated by EMF-LTE irradiation in B16 and HaCaT cells. This finding suggests that p53 plays a role in the protective effect of EMF-LTE against DNA DSBs. Collectively, these results demonstrated that EMF-LTE might have a protective effect against DNA DSB damage in the skin, although further studies are necessary to understand its impact on human health.

Greener Physical Layer Technologies for 6G Mobile Communications

Energy efficiency (EE) has been regarded as an essential design metric in 5G mobile communications. However, the massive antenna numbers, larger bandwidths, and higher density of base stations have been severely deteriorating the power consumption of 5G networks. In this article, the fundamental EE-spectrum efficiency (SE) joint design issues are thoughtfully considered. The relationships between EE and SE in single-input single-output (SISO), multiple-input multiple-output, and hybrid beamforming structures are first reviewed, where the increase of SE (EE) will unfortunately bring a reduction of EE (SE). To resolve this contradiction, a non-orthogonal multiple access (NOMA) scheme with energy-efficient user scheduling and resource allocation is investigated, which promises a simultaneous increase of EE and SE. Furthermore, a precoded waveform overlapping multiplexing scheme is presented, with significant improvements in EE and SE over the traditional Nyquist-criterion-based SISO systems. The waveform overlapping multiple access scheme is further proposed, which promises large performance improvements over the NOMA schemes discussed in 5G New Radio. The application of the waveform overlapping scheme in multiple-antenna systems is also investigated. Finally, the challenges of the waveform overlapping scheme and several other research topics are discussed. For sustainable development of the wireless communications industry, greener design in physical layer technologies should be second to none in the future 6G networks and beyond.