Next-generation Mobile Communication Research Articles

Energy Harvesting Modulation for Integrated Control State and Energy Transfer in Industrial IoT

With the development of wireless communications, the technology of industrial Internet of Things (IIoT) has been considered as a candidate for the next generation of mobile communications, which could provide automatic services for the smart factory. Massive low-power devices are swarming into the scenario for providing network intelligence. These energy-thirsty devices all require efficient control state delivery. In this letter, an energy harvesting modulation (EHM) scheme is proposed for integrated control state and energy transfer (ICSET) towards these low-power devices. The performance of wireless energy transfer (WET) and wireless control state transfer (WCST) are also analysed theoretically. The ICSET performance is optimized by ensuring the control reliability. Simulation results validate the theoretical analysis. They also demonstrate that an appropriate time slot number within a period should be selected to increase the effective control rate, while ensuring the energy harvesting performance and the control reliability of IIoT.

Evaluating RF Hardware Characteristics for Automotive JCRS Systems Based on PMCW-CDMA at 77GHz

Joint communications and radar sensing (JCRS) applications are currently being hailed as the innovation of the next generation of mobile communications. The combination of communications and sensor technology on one hardware platform offers various advantages, such as significant savings in space and costs. The two technologies are no longer being optimized and developed side by side, as has been the case in the past, but jointly. The physical channel is used by both simultaneously, including the transmitter and receiver structures, which must be optimized for the combined application. This inevitably leads to an influence on the performance of both systems. In this work, this influence is considered and analyzed with respect to the effects of the radio frequency components. For this purpose, our previously published code-division multiple access (CDMA)-based and vehicle-to-vehicle-focused model is extended to a JCRS model and evaluated according to the achieved bit error rate as well as the mean deviation of the detected distance and velocity in Simulink. The influence of the non-ideal hardware components (mixers, power amplifier, low noise amplifier, filter, antenna) and characteristics (S-parameters, non-linearity of the amplifiers and the noise) on the sensing and communications are analyzed and compared in this automotive context. The results reveal that the noise of the low noise amplifier at the receiver side has the most decisive influence. In contrast, the noise generated by the power amplifier at the transmitter has no effect due to the relatively high signal power. The non-linearity of amplifiers at the transmitter also significantly impacts the available sensing range by limiting and compressing signal power. Besides, the phase noise with a frequency offset higher than 10MHz can increase the communications and sensing error rate. In contrast, the influence of S-parameters is negligible, as the performance of communications and sensing is almost unchanged with different S-parameters. In the future, the proposed single-target scene will be further extended to a multi-target one.

Joint multi-domain channel estimation based on sparse Bayesian learning for OTFS system

Since orthogonal time-frequency space (OTFS) can effectively handle the problems caused by Doppler effect in high-mobility environment, it has gradually become a promising candidate for modulation scheme in the next generation of mobile communication. However, the inter-Doppler interference (IDI) problem caused by fractional Doppler poses great challenges to channel estimation. To avoid this problem, this paper proposes a joint time and delay-Doppler (DD) domain based on sparse Bayesian learning (SBL) channel estimation algorithm. Firstly, we derive the original channel response (OCR) from the time domain channel impulse response (CIR), which can reflect the channel variation during one OTFS symbol. Compare with the traditional channel model, the OCR can avoid the IDI problem. After that, the dimension of OCR is reduced by using the basis expansion model (BEM) and the relationship between the time and DD domain channel model, so that we have turned the underdetermined problem into an overdeter-mined problem. Finally, in terms of sparsity of channel in delay domain, SBL algorithm is used to estimate the basis coefficients in the BEM without any priori information of channel. The simulation results show the effectiveness and superiority of the proposed channel estimation algorithm.

Machine Learning Modeling for Radiofrequency Electromagnetic Fields (RF-EMF) Signals From mmWave 5G Signals

5G is the next-generation mobile communication technology expected to deliver more excellent data rates than Long Term Evolution (LTE). It offers ultra-low latency and ultra-high dependability, allowing revolutionary services across sectors. 5G mm-Wave base stations may emit harmful radiofrequency electromagnetic fields (RF-EMF). However, RF-EMF concern raises health and safety. From our research, the RF-EMF prediction model lacks papers or publications. This study uses IEEE and ICNIRP standards for assessment and exposure limits. The measuring campaign analyses one sector of a 5G base station (5G-BS) operation on 29.5 GHz in Cyberjaya, Malaysia. This study proposes two prediction models. The first model predicts signal beam RF-EMF, and the second predicts base station RF-EMF. Each model contains three neural network techniques to forecast RF-EMF values: Approximate-RBFNN, Exact-RBFNN, and GRNN. The results are analysed and compared with the measured data, observing which algorithm is more accurate by calculating the RMSE of each algorithm. As a result, it can observe that the Exact-RBFNN algorithm is the best algorithm to predict the RF-EMF because it shows a good agreement with the measured value. Besides that, in 1-min duration, the difference between predicted and measured values reached 0.2 less channels. However, in 6-min and 30-min, it can observe more accurate results since the differences between values reached 0.1in the situations. In addition, the ICNIRP standard was used and compared with the result and validation value of the algorithms.

Surface Dispersion Suppression in High-Frequency GaN Devices

GaN-based high electron mobility transistors (HEMTs) are shown to have excellent properties, showing themselves to perform well among the throng of solid-state power amplifiers. They are particularly promising candidates for next-generation mobile communication applications due to their high power density, frequency, and efficiency. However, the radio-frequency (RF) dispersion aroused by a high surface-state density inherent in nitrides causes the degradation of GaN devices’ performance and reliability. Although various dispersion suppression strategies have been proposed successively—including surface treatment, passivation, field plate, cap layer, and Si surface doping—outcomes were not satisfactory for devices with higher frequencies until the emergence of a novel N-polar deep recess (NPDR) structure broke this deadlock. This paper summarizes the generation of dispersion, several widespread dispersion containment approaches, and their bottlenecks under high frequencies. Subsequently, we highlight the NPDR structure as a potential substitute, evaluate its technical benefits, and review the continuous exertions in recent years.

An improved and provably secure symmetric-key based 5G-AKA Protocol

One of the primary authentication mechanisms defined for the 5G system is the 5G-Authentication and Key Agreement (5G-AKA) protocol. It is set to be used in the next generation of mobile communications but has several serious flaws such as privacy issues, vulnerability to traceability attacks, and has de-synchronization problem. To deal with these issues, An Braeken presented a lightweight authentication mechanism that provides security features not present in 5G-AKA, but the scheme fails to provide perfect forward secrecy. Later Munilla et al. introduced an improved version of the Braeken authentication scheme that claims to provide perfect forward secrecy but is computationally expensive and prone to DoS attacks if the size of the server database is large. Taking this in view, we propose a cost-effective scheme that provides all the security features, including perfect forward secrecy. We do the informal (non-mathematical) and formal analysis (using the ROR, GNY, and Scyther tool) of the security properties of the proposed protocol and show that the proposed protocol provides all the security features. Furthermore, we measure the performance of the proposed protocol in terms of energy consumption and computational, communication and storage costs. The evaluation results show that the proposed protocol takes significantly less cost than most of its competitors. In addition to this, we also compute the performance of the proposed protocol under unknown attacks in terms of computational, communication, and energy consumption costs. The outcome of analysis shows that the proposed protocol takes very less overhead under unknown attacks compared to its competitors.

Massive Wireless Access Enhancement Based on Self-Similarity of Fractal Channels in Multiscale Space

Massive Internet of Things (IoT) is an important application scenario for the next-generation mobile communication systems. The channel estimation is crucial for the performance of massive wireless access in IoT. However, when the number of terminals is large, the huge pilot overhead may seriously increase the burden of the wireless access system. Therefore, reducing the pilot overhead while ensuring the accuracy of channel estimation is an important challenge for massive wireless access systems. In this article, we propose a massive wireless access mechanism, which greatly reduces the pilot overhead and improve the energy efficiency (EE) of terminals. Based on the self-similarity of fractal channels, the channel-state information (CSI) of a subset of terminals is sampled to estimate the CSI of all terminals, thereby reducing the pilot overhead and solving the shortage of pilot resources in massive wireless access systems. Meanwhile, the optimal transmission power of terminals based on CSI can save the energy consumption of terminals in IoT. Compared with the traditional algorithm, simulation results indicate that the proposed massive wireless access mechanism improves the EE of terminal by 340% and reduces 70% of the pilot overhead.

Analysis and design of ultra-wideband PRGW hybrid coupler using PEC/PMC waveguide model

In this paper, a new method to facilitate the design of Printed Ridge Gap Waveguide (PRGW) structures is introduced. One of the main difficulties in designing such structures is related to their simulation process which is really time and energy-consuming. Therefore, a suitable boundary condition is considered to bring about the primary structure without involving the bed of nails or mushroom unit cells. Using this technique, a wideband PRGW 3 dB hybrid double-box coupler is designed to serve in mm-wave frequencies at a center frequency of 30 GHz, which can be deployed for the next generation of mobile communication. The designed coupler provides a wide matching and isolation bandwidth with low output amplitude imbalance, which is unique in comparison with current couplers. The prototype of the proposed coupler is fabricated and measured where the simulation and measurement results show a good agreement indicating the strength of the proposed method in PRGW structure design as well. The measured results show the couplers achieve better than 10-dB return loss and isolation over the frequency range from 25 to 40 GHz (46% BW) with the power-split unbalance and phase error within ± 1 dB and ± 5°, respectively. In addition, square mushrooms are chosen here to satisfy the high impedance surface. Not only do they bring about larger stop bandwidth, but also their configuration facilitates the arrangement of them around the coupler. The proposed design has superb characteristics such as low profile, low loss, and easy integration with microwave circuits and systems that can be suitable for designing mm-wave beamforming networks.

Ultra-wide-band millimeter-wave generator using spin torque oscillator with strong interlayer exchange couplings

Recent increased development interest in millimeter-wave oscillator devices has necessitated realization of small oscillators with high frequency, wide frequency tunability, and room-temperature operation. Spin-torque oscillators (STOs) are fascinating candidates for such applications because of their nanometer size and suitability for room-temperature operation. However, their oscillation frequency and tunable range are limited to the order of 100 MHz–10 GHz. Here, we propose use of bilinear (J1) and biquadratic (J2) interlayer exchange couplings between ferromagnets in STOs to overcome these problems. The bilinear coupling contributes to oscillation frequency enhancement, whereas the biquadratic coupling facilitates frequency tunability via a current. Using micromagnetic simulation with parameters estimated from a material with small saturation magnetization, for J1 = 0 and J2 = − 1.0 mJ/m2, respectively, we find that the STO exhibits high frequency from 23 to 576 GHz and that its tunability reaches 61 GHz/(1011 A/m2) for current densities of − 0.5 to − 9.5 × 1011 A/m2. An analytical theory based on the macrospin model is also developed, which exhibits good quantitative agreement with the micromagnetic simulations. These results introduce new possibilities for spintronics applications in high-frequency devices such as next-generation mobile communications.

Enhancing the performance of downlink NOMA relaying networks by RF energy harvesting and data buffering at relay

Recently, non-orthogonal multiple access (NOMA) and energy harvesting (EH) from radio frequency (RF) have been considered as promising candidates for next-generation mobile communications. In this paper, we investigate a novel solution to enhance the reliability and the supply stability of a downlink NOMA relaying networks, in which we integrate two techniques: (i) simultaneous wireless information and power transfer, i.e. the relay node can harvest the energy from source signals and use this energy to help forward information from source node to two user nodes; and (ii) data buffer aid at relay node, i.e. the data packets received from the source can be stored in a buffer and then be re-transmitted to the destination nodes only when the channel condition is good. The performance of the proposed system is analyzed rigorously to derive the system outage probability (OP), throughput and the average packet delay. Furthermore, a power allocation optimization problem to minimize the OP is formulated and solution to this problem is also provided. In addition, the optimal transmission rates to maximize the throughput of each user are presented in numerical results. Monte Carlo simulations are conducted to verify the analytical results, which confirms that with data buffer at relay, the overall outage probability (OOP) can be reduced significantly.

Bruce Lee-Inspired Fluid Antenna System: Six Research Topics and the Potentials for 6G

While 5G is tasked to transform our lives for the better over the next 10 years, next-generation mobile communications, a.k.a. 6G, will undoubtedly demand even higher energy and spectral efficiencies capable of providing myriads of new services and experience to users everywhere they go. Although our technologies do evolve from one generation to the next, the root of the ambition in mobile communications has always been to ensure reliable performance from an uncertain, fluctuating medium. The previous generations have already seen numerous technologies such as advanced coding and signal processing, resource allocation, and most famously, multiple-input multiple-output to redeem some stability from the wireless medium. Inevitably, 6G will be built upon further disruptive technologies that enable another cycle of revolution. In this article, we examine one emerging technology, referred to as fluid antenna system that represents any software-controllable fluidic, conductive, or dielectric structure that can alter its shape and position to reconfigure the gain, radiation pattern, operating frequency, and other characteristics. Fluid antenna takes inspiration from Bruce Lee's Jeet Kune Do to innovate mobile communication systems design. In Bruce Lee's philosophy, one can imitate water to adapt combat style, whereas fluid antenna exploits the dynamic nature of fluids or switchable pixels to achieve ultimate flexibility for diversity and multiplexing benefits that have been unseen before in mobile devices, and the implication can be transformative. This article discusses the potential of fluid antenna systems for 6G, and in particular, we introduce six research topics in fluid antenna systems that if solved successfully could revolutionize mobile communications network design and optimization. This article intends to stimulate discussion that will help shape the development of 6G technologies.

Excess Loss by Urban Building Shadowing and Empirical Slant Path Model

Excess loss due to building shadowing is regarded as an obstacle effect by buildings existing on the radio propagation path in relation to the service coverage performance of the next-generation mobile communication. In order to overcome the limitations of a geometric or deterministic modeling of existing obstacle loss models (ITU-R, W-I, and W-B model) and increase the accuracy of prediction of excess loss below 10 GHz in real urban environments, the improved empirical model is proposed by adding new variable and optimized fitting parameter values to the existing ITU-R model's formula. New variable and optimized parameter values reflect complex building structure and building height and their propagation impact through measurement. For validation of the proposed model, the self-verification and cross-verification were performed using the measured data from Korea and Japan. The measured data as well as the proposed model were presented as root-mean-square error that can be compared with other existing models in accuracy. The new proposed empirical model showed good agreement with the measured data compared to the existing geometric and deterministic models. In conclusion, the proposed model can be applied to the slant path link below 10 GHz frequency.

Dynamic Analysis of Alternative Elements in an Automated Packaging System Based on 5G Internet of Things

The arrival of 5G will usher in an era of “Internet of Everything.” Massive Internet of Things data contains great value in the dynamic analysis of alternative elements of automated packaging systems. From the perspective of the realization of personalized customization functions, this article solves the problem of dynamic analysis of alternative elements in the automated packaging system. We analyze the connection mechanism and interaction method between the cloud service system layer and the mobile terminal service layer, and carry out the corresponding software design. From the perspective of the realization of the intelligent production of the system in this paper, this topic mainly studies the information interaction mechanism and production control mechanism of the cloud service system and the manufacturing system. Based on the hardware of the manufacturing system layer, a flexible production implementation mechanism is formulated to make it the basis for the implementation of intelligent production of the system. Based on the massive data processing capabilities of the cloud service system, the information processing mechanism and the production planning decision-making mechanism are formulated for it, so as to realize the intelligent adjustment of the manufacturing system layer in the production process. For the connection scenario of IoT group paging, based on the application of NB-IoT technology in the next-generation mobile communication network, the focus of network optimization is to ensure the random access performance of IoT devices as much as possible. To this end, this paper proposes a random access optimization strategy for IoT group paging based on time slot scattering. We establish a mathematical model based on queuing theory for the connection scenario of the Io T group paging, then use the mathematical formula to derive the number of IoT devices scattered to each time slot in the initial state, thereby deriving the specific time slot scattering algorithm. This paper establishes a list of credit nodes, changes the participation mode of consensus nodes from static to dynamic, and supports voting to select trusted nodes. We designed a credit evaluation mechanism as a basis for consensus node elections to improve system’s fault tolerance rate. The algorithm process was simplified, and the PBFT algorithm process was simplified from a 3-phase protocol to a 2-phase protocol to further reduce communication bandwidth overhead and algorithm time. Simulation analysis shows that, compared with the PBFT algorithm, the proposed algorithm improves node flexibility and fault tolerance while reducing communication bandwidth overhead by about 45%, packaging throughput by about 4%, and latency by about 3%.

Flat Optical Frequency Comb Generator Based on Integrated Lithium Niobate Modulators

Chip-scale electro-optic (EO) frequency combs are expected to play an essential role in future high-capacity optical communications systems and next-generation mobile communications. The application requires integrated EO frequency comb generators featuring good spectral flatness, high modulation bandwidth, low driving voltage and low insertion loss simultaneously. Here, we demonstrate a flat-top optical flat comb (OFC) generator based on high-performance lithium niobate on insulator modulators. The OFC generator shows a low on-chip loss (2.1 dB), a low driving voltage over a broad frequency range, and a large 3-dB EO bandwidth. Moreover, with consuming power of less than 2W, the presented device produces 13 lines with a power variation of less than 1.2 dB and a line spacing of 31 GHz which can further be extended to 67 GHz.

Human Activity Recognition With Commercial WiFi Signals

The next generation of mobile communication aims to extend the capabilities of traditional communication by reshaping the environment with wireless signals. The channel state information can describe the propagation characteristics in wireless communications, which is beneficial in developing wireless communication networks towards intelligent communication and wireless sensing networks. Raspberry PI with Nexmon firmware patched can extract the channel state information from WiFi signals and realize human activity recognition. However, the phase values on some carriers are susceptible to noise, resulting in phase errors after singular value decomposition. To solve this problem, a method is proposed in this paper to find the optimal phase value by dynamic time warping algorithm utilizing the property of orthogonality between amplitude and phase. In contrast to the conventional recognition strategies, the proposed optimal phase extraction method with commercial WiFi signals can further improve the accuracy of the recognition strategy under different complicated scenarios.

Non-Mechanical Beam Steering and Adaptive Beam Control Using Variable Focus Lenses for Free-Space Optical Communications

Free-space optical communications (FSOCs) are gaining popularity as a promising solution to the capacity crunch of aerial and satellite backhaul networks for next-generation mobile communication systems. A major technical challenge associated with such FSOC systems in motion is the pointing, acquisition, and tracking (PAT). To facilitate PAT, it is absolutely necessary to steer the optical beam over a wide angle and also adjust the beam divergence angle adaptively to the link condition and the amount of pointing error. The conventional methods to steer the optical beam and/or to adjust the beam divergence angle rely on mechanical mechanisms. Recently, the optical beam steering technique using variable focus lenses has been proposed and demonstrated. By using an on-axis variable focus lens followed by two decentered variable focus lenses, we can steer the optical beam over a wide range in a non-mechanical fashion. In this paper, we explore the possibility of using variable focus lenses for the realization of beam steering and adaptive beam control for FSOCs. For this purpose, we employ three variable focus lenses, one on-axis lens for adaptive beam divergence control and two decentered lenses for two-dimensional beam steering. We demonstrate the simultaneous beam steering and adaptive beam control capability of this variable focus lens-based system over a 104-m long free-space optical link. We evaluate the maximum beam steering angle and beam quality as we vary the offset distance of decentered variable focus lenses. Also evaluated experimentally is the impact of gravity on the beam quality. Finally, we show that the beam steering and adaptive beam control techniques implemented by variable focus lenses improve the performance of 10-Gb/s FSOC system considerably in the presence of pointing errors.

Value Configurations for Data and Connectivity Solutions in Digitalized Future Factories

The ongoing Industry 4.0 transformation places significant pressures on how businesses create and capture value. Technological advancements such as next-generation mobile communications are reshaping the business ecosystem of Industry 4.0, resulting in emerging business opportunities for new players, such as local operators, to collaborate and compete with mobile communications companies that are implementing I4.0. These changes raise the need to explore emerging business opportunities concerning the digitalization of future factories. New data and connectivity services are introduced to serve the needs of rapidly increasing machine-type communications that rely on connectivity, primarily through the fifth generation (5G) mobile solutions provided by local operators. Thus, this paper outlines the potential value configurations for data and connectivity solutions by identifying, matching, and bridging the utilizable resources and addressable needs within the factory processes. The research applies an exploratory approach and uses the Gioia method to analyze qualitative data of a single case. The study follows the connectivity-content-context-commerce typology (4C) of Internet business models to structure, analyze, and classify the identified needs and resources in future factories from the perspective of the local operator. The findings show that the content layer of 4C business model typology is the most dominant among data and connectivity-based needs and resources of future factories. The paper contributes by presenting four alternative value configurations for digitalization for local operators in the future factory context: the product, component, platform, and complementary businesses. The results suggest content- and context-specific businesses carries foremost business potential for local operators, however quantitative validation will bring fruitful research avenues. Multiple case studies and different data collection methods may also be considered in future studies.

Proportional fair buffer scheduling algorithm for 5G enhanced mobile broadband

The impending next generation of mobile communications denoted 5G intends to interconnect user equipment, things, vehicles, and cities. It will provide an order of magnitude improvement in performance and network efficiency, and different combinations of use cases enhanced mobile broadband (eMBB), ultra reliable low latency communications (URLLC), massive internet of things (mIoT) with new capabilities and diverse requirements. Adoption of advanced radio resource management procedures such as packet scheduling algorithms is necessary to distribute radio resources among different users efficiently. The proportional fair (PF) scheduling algorithm and its modified versions have proved to be the commonly used scheduling algorithms for their ability to provide a tradeoff between throughput and fairness. In this article, the buffer status is combined with the PF metric to suggest a new scheduling algorithm for efficient support for eMBB. The effectiveness of the proposed scheduling strategy is proved through à comprehensive experimental analysis based on the evaluation of different quality of service key performance indicators (QoS KPIs) such as throughput, fairness, and buffer status.

6G and the UN SDGs: Where is the Connection?

Sustainability has entered all aspects of life, calling for an active approach from the wireless and mobile communications community to help in solving fundamental challenges facing societies. Societal, economic, and environmental aspects of sustainability have become increasingly important design criteria in developing future technologies, along with the United Nations Sustainable Development Goals (UN SDGs) framework that sets specific goals and targets to be achieved by 2030. The role of mobile communications is important in supporting nations and organizations in meeting the UN SDGs in a timely manner, but the whole ICT sector itself, with its critical role as the backbone of society, can create a significant sustainability burden. Research on the next-generation mobile communication networks (6G) has started, aiming at first deployments in 2030, in a new era where sustainability defines its development. Therefore, sustainability, especially through the UN SDGs, and the future 6G wireless networks, cannot be treated in isolation, but a clear connection between them is urgently needed. This paper extends from traditional green communications and energy efficiency considerations in wireless communications to establishing a close connection between 6G and the triple bottom line of economic sustainability, societal sustainability, and environmental sustainability. The paper outlines open research challenges for sustainable 6G development and provides a set of research questions encouraging especially the researchers and engineers in the wireless and mobile communications community to address to realize a sustainable future.

A low-sintering temperature microwave dielectric ceramic for 5G LTCC applications with ultralow loss

In next-generation mobile and wireless communication systems, low sintering temperature and excellent dielectric properties are synergistic objectives in the application of dielectric resonators/filters. In this work, Li2Ti0·98Mg0·02O2·96F0.04–1 wt% Nb2O5 (LTMN) ceramics were fabricated, and their sintering temperature was successfully lowered from 1120 °C to 750 °C by adjusting the mass ratio of B2O3–CuO (BC) additive. The optimum dielectric properties (ԑr ~ 24.44, Q × f ~ 60,574 GHz and τf ~ 22.8 ppm/°C) were obtained in BC-modified LTMN ceramics sintered at 790 °C. Even if their sintering temperature was lowered to 750 °C, the lowest temperature among the Li2TiO3-based dielectric ceramics currently used for LTCC technology, excellent dielectric properties (ԑr ~ 23.77, Q × f ~ 51,636 GHz) were still maintained. Additionally, no extra impurity phase was detected in BC-modified LTMN ceramics co-fired with Ag at 790 °C, indicating that BC-modified LTMN ceramics have a bright prospect in high-performance LTCC devices for 5G applications.