Broadband Communication Research Articles

OFDM and MIMO wireless communication performance measurement using enhanced selective mapping based partial transmit sequences

The great spectral efficiency to mitigate multipath fading of OFDM (orthogonal frequency division multiplexing) made more accepted for broadband communication systems with some drawbacks such as high PAPR (Peak-to-Average Power Ratio), ISI (Inter-Symbol Interference) and ICI (Interiv Carrier Interference). High PAPR forces the operations of the HPA amplifier to work beyond its linear region causing in-band distortion as well as out-band noise and are overcome by using an amplifier with a large dynamic range. In this method, OFDM symbols are partitioned into multiple disjoint sub-blocks which are independently rotated in phase by optimum phase weighting factors. The resultant OFDM signal has less PAPR when compared to that of original OFDM signal in wireless communication. To minimize computational complexity, a modified PTS technique is proposed to enhance PAPR reduction and power amplifier efficiency in OFDM and MIMO (multiple inputs, multiple outputs)-OFDM methods through Selective Mapping based PTS (SMPTS) method combined with PAPR reduction methods.

An Overview of Free Space Optics Communication System

Free space optics is a kind of broadband communication technique that transmits the signals, in the atmosphere through laser beams. In some cases, the laser beams are replaced with infrared and modified beams. Free Space Optics (FSO) is also referred as Free Space Photonics that works same as the principle of fiber optic communication where the source beams are transferred through air medium. In the traditional fiber optic communication, the optical fibers were used for transferring the beam signals. The FSO methodology is widely employed in various ubiquitous applications for their cost and deployment effectiveness. The motive of the work is to explore the concepts and theories behind the operation of different FSO models with their recent progress.

Circular tooth based low profile 1x2 superlative MIMO antenna with high gain and isolation for fixed satellite service, and land mobile navigation applications

The 1 × 2 superlative MIMO antenna structure is proposed for multiband and broadband communication applications. The presented antenna is composed of two symmetrical circular-shaped patch elements. The circular-shaped Tooth is inserted in the outer periphery of the patch area. The Radius of the patch and Tooth varies to identify the behaviour of reflectance response, directivity, and total gain. The tooth-loaded circular patch attained a better gain of 8.44 dB, broader directivity of 163°, reflectance coefficients of −29.16 dB, and good isolation among transmittance and reflectance response. The comparison between simulated and measured results is included in the analysis. Performance of the presented design structure with previously published articles to identify performance improvement. Standard performance measurement parameters like TARC, ECC, and DG are also carried out. The low-profile material FR4 is used in the proposed design as a substrate. The presented structure is suitable for fixed satellite service and Land mobile navigation applications.

Resource Slicing for eMBB and URLLC Services in Radio Access Network Using Hierarchical Deep Learning

Network slicing is a promising technique for wireless service providers to support enhanced mobile broadband (eMBB) and ultra-reliable low-latency communication (URLLC) services in a shared radio access network (RAN) infrastructure. In this paper, we apply numerology, mini-slot based transmission, and punctured scheduling techniques to support eMBB and URLLC network slices. For efficient allocation of radio resources (e.g., physical resource blocks, transmit power) to the users, we formulate RAN slicing problem as a multi-timescale problem. To solve this problem and address the dynamics of the traffic, we propose a hierarchical deep learning framework. Specifically, in each long time slot, the service provider employs a deep reinforcement learning (DRL) algorithm to determine the slice configuration parameters. The eMBB and URLLC schedulers use their own attention-based deep neural network (DNN) algorithm to allocate radio resources to their corresponding users in each short and mini time slot, respectively. Simulation results show that the proposed framework can achieve a higher aggregate throughput and a higher service level agreement (SLA) satisfaction ratio compared to some other RAN slicing approaches, including the resource proportional placement algorithm, decomposition and relaxation based resource allocation algorithm, and distributed bandwidth optimization algorithm.

Energy-Efficient Optimization via Joint Power and Subcarrier Allocation for eMBB and URLLC Services

This letter considers joint subcarrier and power allocation in the distributed MIMO system for enhanced mobile broadband (eMBB) and ultra-reliable low-latency communication (URLLC) services. Orthogonal and non-orthogonal scheduling scheme can be selected by subcarrier assignment to improve spectral efficiency and meet the reliability requirement of URLLC. Short packet transmission is adopted for URLLC to meet the low latency requirements. We formulate a mixed-integer optimization problem by maximizing the energy efficiency (EE) of the system subject to quality of service (QoS) constraints. The problem is intractable to solve and then we propose a low computational complexity algorithm to find the suboptimal solution of the problem. Simulation results show that the proposed algorithm can converge fast and significantly improve the EE for eMBB and URLLC services.

A Manifold Regularization Approach for Low Sampling Rate Digital Predistortion With Band-Limited Feedback

Digital predistortion (DPD) is an effective linearization technique for RF power amplifiers (PAs), but conventional full sampling (FS) DPD systems use ADCs with three to five times signal bandwidth, and high-speed ADCs are expensive and power-hungry. In this article, we develop a novel band-limited DPD for reducing feedback sampling rate and acquisition bandwidth based on a general framework for semisupervised learning called manifold regularization (MR), which utilizes the geometry of unlabeled data to construct regularization terms for mitigating the overfitting problem. Considering the properties of DPD, we design a basis MR term and introduce it into the classical MR to obtain the extended MR (ExMR) method. To validate the proposed ExMR DPD method, experiments were conducted on two different RF PAs operating at 2.4 and 39 GHz, respectively. The test results demonstrate that the proposed ExMR DPD can linearize the RF PA with a 40-MHz acquisition bandwidth at 100-MHz input. The proposed method significantly reduces the cost and power consumption of the DPD system in comparison with the conventional FS DPD method, which provides a promising solution for broadband communication systems.

Adaptive Threshold Energy Detection Spectrum Sensing Method for L-Band Digital Aeronautical Communication System

Air travel is growing at an alarming rate. However, according to the latest research report by Eurocontrol on European aviation, the growth of air traffic will be limited by the available spectrum resources. As one of the means to provide air/ground (A/G) broadband communication, the L-band digital aeronautical communication system (LDACS) is becoming the preferred model for final deployment and has received continuous attention. Based on various spectrum measurement studies, the international civil aviation organization (ICAO) has identified multiple 1 MHz vacant bands between adjacent distance measuring equipment (DME) signals for LDACS. In order to improve spectrum efficiency, the concept of dynamic spectrum access (DSA) can be applied to the LDACS, which requires the use of spectrum sensing methods to detect the spectrum holes of DME users. In this paper, an adaptive threshold energy detection spectrum sensing method is proposed based on the characteristics of DME pulse signals. Firstly, the energy of the received signal is estimated to construct the detection statistics, and the equations of detection probability and false alarm probability are established. Secondly, the adaptive threshold is calculated using the maximum likelihood decision criterion under the assumption of a constant probability of false alarm. Thirdly, the detection statistic is compared to the adaptive threshold to determine the spectrum occupancy state in the decision-making stage. Finally, the result is transmitted back to the transmitter for the best spectrum resource allocation. According to the simulation analysis, the adaptive threshold energy detection-based sensing method outperforms the energy-difference detection method under low signal-to-noise ratio (SNR) conditions. Meanwhile, it has superior adaptability since the adaptive threshold can be adaptively changed according to the channel.

Guest Editorial: AI for Open Programmable Virtualized Networks in 6G

Programmable virtualized networks decouple data and control planes and have the power of supporting the demands of diverse and varied use cases, allowing the services to scale and adapt dynamically. The diverse demands of Enhanced Mobile Broadband (eMBB), Ultra-Reliable and Low-latency Communications (uRLLC), and massive Machine Type Communications (mMTC) users inevitably increase the network complexity, making programmability alone not sufficient. To fulfill these demands, next generation mobile networks need to respond with the capacity of supporting a greater number of heterogeneous devices, the availability of more spectrum and the introduction of complex protocol stacks, making automated and intelligent tools for management, reconfiguration, adaptation, and coordination of network resources an impelling necessity.

Modal Analysis, Inverse-Design, and Experimental Validation of Bandwidth-Controllable Suspended Patch Antennas Loaded With Cylindrical Anisotropic Impedance Surfaces

In this article, bandwidth-controllable suspended patch antennas (SPAs) loaded by anisotropic impedance surfaces (AISs) are proposed. A highly efficient yet accurate semianalytical modal expansion method (MEM) is developed for calculating the input impedance and radiation properties of the proposed antenna, which greatly reduces the simulation time and consumed memory compared to a commercial full-wave solver. The MEM is further utilized by coupling it with a genetic algorithm for effectively performing inverse-design, i.e., optimizing AIS-loaded SPAs with different predefined frequency responses. Three proof-of-concept antenna examples are designed, fabricated, and characterized, including an ultrawideband (UWB) antenna, a dual-wideband antenna, and a band-notched UWB antenna. The operating principle is illustrated by investigating the resonant modes of the AIS-loaded SPAs. The measured results of the three antennas exhibit good agreement with theoretical predictions, demonstrating that all three antennas have vertically polarized conical patterns in the E-plane and omnidirectional patterns in the H-plane with a cross polarization of smaller than −15 dB in their respective operational frequency band(s). The good performance demonstrates that the proposed AIS-loaded SPAs are promising candidates for broadband and multiband communications.

Statistical Modeling of Evaporation Duct Channel for Maritime Broadband Communications

The sixth-generation communication networks aim to integrate space, air, and ground communications into a robust network. However, maritime communications are confronted with the challenge of the atmospheric duct, which could capture wireless signals and propagate beyond the line of sight. In this paper, a parabolic equation-based modeling approach is proposed to characterize the maritime evaporation duct channel. The constant coefficients of each variable in the modeling are calculated by the least square method, and the specific distribution of shadow fading in channel modeling is determined by the Kullback-Leibler divergence method. Furthermore, the partitioning around medoids method is utilized to reduce the average deviation and improve the accuracy of the model. Numerical results illustrate that the statistical channel model possesses satisfactory calculation ability at the distance of signal interference caused by the evaporation duct. In addition, the paper analyzed the influence of the antenna height and downtilt angle on signal propagation.

C-Band Septum Polarizers With Polynomial Profile and Accurate Axial Ratio Characterization in Back-to-Back Configuration

Septum polarizers have been used in waveguide systems for over 50 years and are very popular in communication satellites operating in circular polarization. With the progress of computational electromagnetics and computer hardware, combined with advances in manufacturing techniques, there has been a growing interest in septum polarizers with smooth profiles. In particular, a design using Legendre polynomials was recently introduced by the authors. This paper reports on the first experimental validation of this component and introduces also alternative profiles based on cubic splines. The new designs account for considerations on the overhang angle, which is an important parameter in additive layer manufacturing. The axial ratio of these designs is evaluated using a simple and accurate technique based on a back-to-back configuration, which can be implemented outside an anechoic chamber. The proposed characterization technique relies on the custom flanges implemented on the circular common port of septum polarizers to interface with horn antennas. These flanges typically have an 8-fold rotational symmetry, which enables to perform multiple measurements of a back-to-back configuration without requiring further equipment. The measured data is then processed to obtain the axial ratio of the two septum polarizers. This characterization technique is particularly advantageous when a large number of feeds needs to be tested, which is relevant in current and future broadband communication satellites. The technique is validated by comparing with measured data acquired in an anechoic chamber using a standard technique. Various prototypes, designed for operation in C-band communication satellite downlink, are characterized and promising results are obtained, showing very good agreement between simulated and measured data.

Full-space terahertz metasurface based on thermally tunable InSb

Terahertz (THz) metasurfaces have potential research value in high-quality molecular imaging, high-speed broadband communication, biology, etc. In this paper, thermally tunable full space metasurface was proposed and analyzed by using Finite Difference Time Domain method based on Pancharatnam–Berry phase modulation and InSb temperature characteristic. At 220 K, a metasurface composed of InSb elements can simultaneously achieve efficient transmission and reflection of the incident circularly polarized light at 0.8 THz and 1.15 THz, respectively. On the contrary, at 360 K, the metasurface absorbs all of the incident terahertz waves, essentially turning off the incident beam. In addition, dynamically tunable metalenses were proposed and used to generate focused vortex light. The proposed metasurface provides a potential direction for developing an efficiency-tunable PB terahertz device in the future.

Phototunable chip-scale topological photonics: 160 Gbps waveguide and demultiplexer for THz 6G communication

The revolutionary 5G cellular systems represent a breakthrough in the communication network design to provide a single platform for enabling enhanced broadband communications, virtual reality, autonomous driving, and the internet of everything. However, the ongoing massive deployment of 5G networks has unveiled inherent limitations that have stimulated the demand for innovative technologies with a vision toward 6G communications. Terahertz (0.1-10 THz) technology has been identified as a critical enabler for 6G communications with the prospect of massive capacity and connectivity. Nonetheless, existing terahertz on-chip communication devices suffer from crosstalk, scattering losses, limited data speed, and insufficient tunability. Here, we demonstrate a new class of phototunable, on-chip topological terahertz devices consisting of a broadband single-channel 160 Gbit/s communication link and a silicon Valley Photonic Crystal based demultiplexer. The optically controllable demultiplexing of two different carriers modulated signals without crosstalk is enabled by the topological protection and a critically coupled high-quality (Q) cavity. As a proof of concept, we demultiplexed high spectral efficiency 40 Gbit/s signals and demonstrated real-time streaming of uncompressed high-definition (HD) video (1.5 Gbit/s) using the topological photonic chip. Phototunable silicon topological photonics will augment complementary metal oxide semiconductor (CMOS) compatible terahertz technologies, vital for accelerating the development of futuristic 6G and 7G communication era driving the real-time terabits per second wireless connectivity for network sensing, holographic communication, and cognitive internet of everything.

Toward Smaller and Lower-Cost 5G Devices with Longer Battery Life: An Overview of 3GPP Release 17 RedCap

The fifth generation (5G) wireless technology is primarily developed to support three classes of use cases, namely, enhanced mobile broadband (eMBB), ultra-reliable and low-latency communication (URLLC), and massive machine-type communication (mMTC), with significantly different requirements in terms of data rate, latency, connection density, and power consumption. Meanwhile, there are several key use cases, such as industrial wireless sensor networks, video surveillance, and wearables, whose requirements fall in-between those of eMBB, URLLC, and mMTC. In this regard, 5G can be further optimized to efficiently support such mid-range use cases. Therefore, in Release 17, the 3rd generation partnership project (3GPP) developed the essential features to support a new device type enabling reduced capability (RedCap) new radio (NR) devices aiming at lower cost/complexity, smaller physical size, and longer battery life compared to regular 5G NR devices. In this article, we provide a comprehensive overview of 3GPP Release 17 Red-Cap while describing newly introduced features, cost reduction and power saving gains, and performance and coexistence impacts. Moreover, we present key design guidelines, fundamental tradeoffs, and future outlook for RedCap evolution.

Superposition-Based URLLC Traffic Scheduling in 5G and Beyond Wireless Networks

Ultra-Reliable and Low Latency Communications (URLLC) is one of the essential services in 5G networks and beyond. The coexistence of URLLC alongside other services, namely, enhanced Mobile BroadBand (eMBB) and massive Machine-Type Communications (mMTC), calls for developing spectrally efficient multiplexing techniques. In this work, we study the problem of scheduling URLLC traffic in a downlink system in the presence of eMBB traffic. Based on the proposed superposition/puncturing scheme, a resource allocation problem is formulated with the objective to minimize the rate loss of the eMBB service and URLLC packet segmentation loss while satisfying the eMBB and URLLC quality of service (QoS) constraints. The resulting problem is formulated as a mixed-integer non-linear program (MINLP) which is generally very hard to solve in polynomial time. Hence, we reformulate the problem as a one-to-one pairing problem and we derive its feasibility region as well as the optimal solutions for the power and spectral resource allocation. Subsequently, we propose a low complexity algorithm to support the many-to-many pairing. Simulation results show that the proposed algorithm achieves higher URLLC packet admission rate and lower rate loss for eMBB. For instance, the URLLC packet admission rate, unlike baseline methods, is shown to be preserved under the proposed method even at higher URLLC load. It is shown that at least 30% more URLLC users can be served without degrading their QoS, while keeping the impact on eMBB rate minimal. Detailed numerical evaluation is presented to quantify the benefits of the proposed method.

EXPERIMANTAL RESEARCHES OF OPERATOR-PILOT PERFORMANCE AND DEVELOPMENT OF HIS ACTIONS SUPPORT

Efficiency is an external manifestation of a person’s ability to perform purposeful activities of any kind, including professional activities. The main performance indicator is its level recorded by the on-board monitoring system in terms of heart rate variability (HRV) of the operator-pilot. A feature of the implemented approach in assessing the PL (performance level) indicator (in addition to obtaining a generalized integral indicator at the time of completion of the flight task) is that current indicators are used at different phases of the flight task, due to which the history of PL is tracked in the dynamics of changes in the working state with the identification of situations in which the support is required. Ensuring and maintaining the health (capacity) of the operator-pilot in the remote telepsychophysiological interactive interface mode “Pilot in the cockpit of the aircraft – flight director at the command point” showed the high efficiency of the proposed technology, tested at KPM-V. Such an interface was implemented on the basis of a broadband communication channel – information exchange as part of the KPM-V, and the flight director at the command point (CP) has the opportunity to prototype the situation and its development in order to develop more reliable expert recommendations to the operator-pilot. The interface, including the developed on-board biofeedback system, presents on its monitor of information signs of the external manifestation of the operator’s states in terms of the frequency and nature of respiratory movements. Changes in the structure of the wave respiratory packet spoke about the state of the operator and his performance. Comparison of these data in a single time with the HRV indicators made it possible to qualify the situation as the transition of the operator into a state of working stress, developing fatigue and overwork. The results of a semi-natural experiment with specific expert support (recommendations) of the operator-pilot performing low-altitude flight in difficult weather conditions with the search for objects of interest showed that suggesting a more advantageous maneuver for entering the zone of possible active actions from the CP made it possible to reduce the current level of performance at the time of support, not allow its predicted decrease by 20…30 % and increase the time for making a decision and its implementation by 10…13 s. At the same time, the reliability of the expert forecast of the operator’s PL according to the data of the analysis of the respiratory wave packet on the thermograms of the face was 70…90 %. The conducted cycle of research on the problem of the operator-pilot’s performance, its provision and support is not only of research interest, but can be used in the ergonomic examination of aviation equipment and the design of the crew’s work activities.

Evolution Toward 6G Multi-Band Wireless Networks: A Resource Management Perspective

In this article, we first present the vision, key performance indicators, key enabling techniques (KETs), and services of 6G wireless networks. Then, we highlight a series of general resource management (RM) challenges as well as unique RM challenges corresponding to each KET. The unique RM challenges in 6G necessitate the transformation of existing optimization-based solutions to artificial intelligence/machine learning-empowered solutions. In the sequel, we formulate a joint network selection and subchannel allocation problem for 6G multi-band network that provides both further enhanced mobile broadband (FeMBB) and extreme ultra reliable low latency communication (eURLLC) services to the terrestrial and aerial users. Our solution highlights the efficacy of multi-band network and demonstrates the robustness of dueling deep Q-network in obtaining efficient RM solution with faster convergence rate compared to deep Q-network and double deep Q-network algorithms.

Comprehensive Overview on Millimeter Wave Communications for 5G Networks Concentrating on Propagation Models for Different Urban Environments

The global shortage of bandwidth prompted wireless carriers to move towards millimeter wave frequencies (mm-wave), a frequency spectrum that is underutilized by broadband communications networks. Despite the large number of studies and researches on the issue of millimeter wave propagation in outdoor and indoor environments, specifically environments with high population density, the issue of millimeter wave propagation in those environments remains somewhat ambiguous. For the exact purpose of the design and operation of the fifth-generation networks operating within the millimeter frequency spectrum, it has become necessary to obtain information about the wave propagation within those different environments. This paper presents a description of the wave propagation parameters and channel modeling prepared by several international groups, such as line and non-line of-sight (LOS & NLOS) probabilities and different propagation models to understand the mechanism of wave propagation within the millimeter range (0.5–70 GHz). This paper deals with simulating radio wave propagation in favour of different outdoor scenarios, calculating the path loss in several models and determining which models are most appropriate and best for certain environments.

IEEE 802.15.4g/4x-Based Orthogonal Frequency-Division Multiplexing Transmission Scheme for Wide-Area and Mobile IoT Communication Systems

Radio communication systems using the frequency-shift keying (FSK) scheme standardized by the IEEE 802.15.4g standard can realize low-power consumption and highly reliable communications and are mainly adopted for smart metering as part of the Internet of Things (IoT). However, smart metering has recently broadened its application expectations, with broadband and long-distance communications now required. To fulfill these requirements, orthogonal frequency-division multiplexing (OFDM) has been incorporated into the IEEE 802.15.4g and 802.15.4x standards. However, comprehensive transmission performance analysis of OFDM under static and multipath fading environments has not been conducted. In this article, we first evaluated the packet error rate (PER) of OFDM assuming fixed communications using computer simulations. We then evaluated the transmission distance of OFDM and showed that OFDM can communicate at transmission distances up to 3.0 times longer than those specified in IEEE 802.15.4g FSK. Next, the PER in a mobile communication environment was evaluated using computer simulations. When only the long training field (LTF) was used to estimate multipath radio channels, the required PER of 10% was not achieved, even in a mobile communication environment at a speed of several km/h. To solve this problem, we proposed a receiving scheme which included a new channel estimation scheme. This scheme successively utilized not only the LTF but also pilot signals inserted into the transmitter to estimate radio propagation characteristics. Computer simulation results showed that the required PER was achieved even in a mobile communication environment at 30–40 km/h by using the proposed scheme.

Reinforcement learning based dynamic distributed routing scheme for mega LEO satellite networks

Recently, mega Low Earth Orbit (LEO) Satellite Network (LSN) systems have gained more and more attention due to low latency, broadband communications and global coverage for ground users. One of the primary challenges for LSN systems with inter-satellite links is the routing strategy calculation and maintenance, due to LSN constellation scale and dynamic network topology feature. In order to seek an efficient routing strategy, a Q-learning-based dynamic distributed Routing scheme for LSNs (QRLSN) is proposed in this paper. To achieve low end-to-end delay and low network traffic overhead load in LSNs, QRLSN adopts a multi-objective optimization method to find the optimal next hop for forwarding data packets. Experimental results demonstrate that the proposed scheme can effectively discover the initial routing strategy and provide long-term Quality of Service (QoS) optimization during the routing maintenance process. In addition, comparison results demonstrate that QRLSN is superior to the virtual-topology-based shortest path routing algorithm.