Wireless Design Research Articles

Intelligent framework for radio access network design

The evolution of 5G networks over the last few years has introduced a variety of technologies for more efficient radio access networks (RANs), which end up in ultra-dense heterogeneous infrastructure with deployments of high complexity. In this paper, we propose a new framework for RAN design in ultra-dense urban scenario based on the machine learning. The key idea of the proposed framework is to bring intelligent capabilities to the coverage planning problem for complex multi-tier scenarios, in order to achieve better network performance. We design our framework for small cells coverage optimization with 3D urban environment, macro cell locations, and realistic traffic statistics. Simulation results show that our proposed intelligent RAN framework significantly outperforms the conventional coverage design solutions, even after only a short learning time.

Improving resolution of solid state NMR in dense molecular hydrogen

Recent advancements in radio frequency resonator designs have led to the implementation of nuclear magnetic resonance in diamond anvil cells (DACs) at pressures well above 100 GPa. However, a relatively low resolution and the absence of decoupling sequences complicate the analysis of the results of solid state NMR in DACs. Here, we present the first application of homonuclear Lee-Goldburg (LG) decoupling on high density molecular hydrogen up to 64 GPa. Lenz lens based two-dimensional resonator structures were found to generate a homogeneous B1 field across sample cavities as small as 12 pl, a prerequisite for optimal decoupling. At ideal LG conditions, the broad 1H resonance of molecular ortho-hydrogen was narrowed 1600-fold, resulting in linewidths of 3.1 ppm.

Kapton Based Antenna Simulation Analysis for Smart System

This paper describes the analysis of Kapton material in antenna design for telecommunication systems. Kapton is usually used in the design of radio and microwave frequency antenna. It is a flexible material and with different dielectric value. The antenna is made of a Kapton substrate, a patch and copper (FR4). The dielectric characteristics of Kapton substrate changes according to temperature. The simulation result shows that the bandwidth of the antenna increased up to 10 MHz with a second layer of Kapton substrate. While the antenna gain decreased 1.19 dB when the dielectric value is increased. Computer Simulation Technology (CST) software was used to analyse the antenna’s performance.

Cognitive Radio Principles and Spectrum Sensing

Cognitive Radio is an all intelligent radio network that is advancement over the conventional radio. The difference between the traditional radio and cognitive radio is that all the unused frequency spectrum is utilized to the best of available resources in the cognitive setusp unlike the traditional radio. The major advantage of the cognitive radio is that it can detect channels that are available from the spectrum and modify the parameters used for transmission so that the several unused frequencies can be used concurrently. The research conducted on the cognitive radio is in its primitive stages. However, the need of the hour is the detailed surveys and descriptions of the cognitive radio sensing mechanisms. The operating behavior of the radio will also be improved using the cognitive radio. This paper details the sensing and interference mechanisms of the cognitive radio and explains how and why the cognitive setup is far excellent compared to the conventional radios. There are numerous technologies used in the cognitive radio setup such as the Adaptive radio and Software Defined Radio (SDR). The applications of the findings of this paper can be extended to cognitive radio design and implementation.

First 20 Years of Green Radios

Green radios jointly consider the spectrum efficiency and the energy efficiency in wireless networks in order to provide sustainable development. In the past two decades, various green radio solutions for different types of terminals and radio access networks have been developed, some of which have been used in the designs of wireless products. In this paper, we provide a historical view on some fundamental works and practical issues. In addition to providing a comprehensive overview on theoretical achievements, we also discuss several important power saving solutions with notable engineering impacts, such as Doherty power amplifier and separated baseband unit - remote radio unit architecture, which might be overlooked in previous publications. Moreover, with the huge growth of wireless traffic in the near future, green radio design for future wireless networks shall involve an end-to-end energy efficiency investigation of mobile terminals, radio access and core networks, and different applications. By introducing green radio schemes for advanced terminals and future wireless networks, this article will not only be beneficial for readers with only preliminary background in communications and signal processing but also have reference and historical values for researchers and practical engineers in the area.

Collaborative Communication Based Modern Cellular Planning and Optimization of the Network Performance Parameters using Ga

Cellular planning and dimensioning plays a vital role for streamlining the wireless system design and its optimal roll-out. The state-of-art of radio network design depends on thorough initial planning, clear dimensioning and optimal deployment. Mathematical characterization of user coverage and proper modelling is the prime step to design, optimize and automate a wireless network. A novel dimensioning technique using collaborative communication, for cellular network design has been discussed in the paper and the corresponding radio network parameters like transmission power, receiver throughput and Base Station position has been optimized using modern technique of optimization. With proper cellular network planning, the base station parameters could be tuned to achieve the required QoS (Quality of Service) for meeting the requirements of NG (Next Generation) wireless mobile network. Proposed strategy has been analysed with adaptable radii cells establishing a cluster of users to be dimensioned in a given area. Based on minimum distance between the centroid of two cells in a cluster, the inner coverage for the BS deployment is obtained and outer radial coverage is taken double of the inner radius. The total transmission power requirement is calculated and minimized by adjusting the coordinates of the BS using Genetic Algorithm (GA). With the proposed method, 17.6% power saving and 65.68% improvement in throughput was found at the receiver side as compared to conventional constant radius method.

Advances and Opportunities in Passive Wake-Up Radios with Wireless Energy Harvesting for the Internet of Things Applications.

Wake-up radio is a promising approach to mitigate the problem of idle listening, which incurs additional power consumption for the Internet of Things (IoT) wireless transmission. Radio frequency (RF) energy harvesting technique allows the wake-up radio to remain in a deep sleep and only become active after receiving an external RF signal to ‘wake-up’ the radio, thus eliminating necessary hardware and signal processing to perform idle listening, resulting in higher energy efficiency. This review paper focuses on cross-layer; physical and media access control (PHY and MAC) approaches on passive wake-up radio based on the previous works from the literature. First, an explanation of the circuit design and system architecture of the passive wake-up radios is presented. Afterward, the previous works on RF energy harvesting techniques and the existing passive wake-up radio hardware architectures available in the literature are surveyed and classified. An evaluation of the various MAC protocols utilized for the novel passive wake-up radio technologies is presented. Finally, the paper highlights the potential research opportunities and practical challenges related to the practical implementation of wake-up technology for future IoT applications.

5G-U: Conceptualizing Integrated Utilization of Licensed and Unlicensed Spectrum for Future IoT

IoT applications constitute one of the fastest developing areas in today's technology and at the same time pose the most demanding challenges for the respective radio access network design. While the initial studies in IoT were focused primarily on scaling the existing radio solutions for higher numbers of small-data and low-cost sensors, the current developments aim at supporting wearable augmented/virtual reality platforms, moving industrial robots, driving (semi-)autonomous vehicles, and flying drones, which produce large amounts of data. To satisfy these rapidly growing performance demands, the 5G-grade IoT is envisioned to increasingly employ millimeter-wave (mmWave) spectrum, where wider bandwidths promise to enable higher data rates and low-latency communication. While the mainstream trend in mmWave-based IoT is to rely on licensed bands around 28 GHz or leverage unlicensed bands at 60 GHz, in this work we introduce a conceptual vision for the integrated use of these frequencies within a single radio access system named 5G over unlicensed spectrum or 5G-U. We study the performance of 5G-U in supporting stringent IoT use cases, discuss and compare the alternative strategies for spectrum management in 5G-U, and demonstrate that a harmonized utilization of licensed and unlicensed bands provides notable performance improvements in both device-centric and network-centric metrics. Finally, we offer useful guidelines for future implementations of 5G-U and detail its potential applications in the area of advanced IoT services.

MAKAN: A low‐cost low‐complexity local positioning system

The vulnerability of global navigation satellite systems (GNSSs) to jamming and unavailability in indoor and dense urban environments in combination with low accuracy for many applications leads to the emergence of various local positioning systems (LPSs). In this paper, we propose an LPS that provides positioning service in the designated area using a set of reference stations employing spread-spectrum technology. Radio ranging is the basis of radio navigation systems. Design, implementation, and field test of a spread-spectrum radio ranging system are described. By resolving the synchronization problem using an affordable and available clock source, the complex procedures of acquisition and tracking inside the spread-spectrum receiver are replaced by a simple acquisition-only algorithm. Experimental results of the proposed system in the field test are compared with the simultaneously logged GPS data. The experiments demonstrate proof of concept of the proposed system (MAKAN) for GPS-like performance for positioning in the allocated mission.

Design optimization of the graded AlGaN/GaN HEMT device performance based on material and physical dimensions

PurposeTo design and optimize the traditional aluminum gallium nitride/gallium nitride high electron mobility transistor (HEMT) device in achieving improved performance and current handling capability using the Synopsys’ Sentaurus TCAD tool.Design/methodology/approachVarying material and physical considerations, specifically investigating the effects of graded barriers, spacer interlayer, material selection for the channel, as well as study of the effects in the physical dimensions of the HEMT, have been extensively carried out.FindingsCritical figure-of-merits, specifically the DC characteristics, 2DEG concentrations and mobility of the heterostructure device, have been evaluated. Significant observations include enhancement of maximum current density by 63 per cent, whereas the electron concentration was found to propagate by 1,020 cm−3 in the channel.Practical implicationsThis work aims to provide tactical optimization to traditional heterostructure field effect transistors, rendering its application as power amplifiers, Monolithic Microwave Integrated Circuit (MMICs) and Radar, which requires low noise performance and very high radio frequency design operations.Originality/valueAnalysis in covering the breadth and complexity of heterostructure devices has been carefully executed through extensive TCAD modeling, and the end structure obtained has been optimized to provide best performance.

Terahertz band communication systems: Challenges, novelties and standardization efforts

Wireless data rates are expected to be around 10Gbps or even more within the upcoming decade. The realization of such high data rates is unlikely with the currently licensed bands in the spectrum. Therefore, it is clear that such high rates could only be achieved by employing more bandwidth with the state-of-the-art technology. Considering the fact that bands in the range of 275GHz–3000GHz, which are known as Terahertz (THz) bands, are not yet allocated for specific active services around the globe, there can be a true potential to achieve the desired data rates at THz bands. However, due to the characteristics of these bands, there are many open issues in terms of THz radio communication system design. In this study, open issues and the state-of-the-art solutions to these issues for THz communication system design are discussed. Moreover, standardization efforts up to date are elaborated. This study concludes that the actual implementation of fully operational THz communication systems obliges to carry out a multi-disciplinary effort including statistical propagation and channel characterizations, adaptive transceiver designs (including both baseband and radio frequency (RF) front-end portions), reconfigurable platforms, advanced signal processing algorithms and techniques along with upper layer protocols equipped with various security and privacy levels.

2018 SIGMOBILE Outstanding Contributions Award

Dr. Teresa H. Meng is the 2018 SIGMOBILE Outstanding Contributions Award recipient. She is a pioneer of radio hardware design and implementation for wireless localarea network (LAN). Her groundbreaking research, engineering and leadership at Atheros made Wi-Fi faster, lower power, and cheaper; as a result, Wi-Fi technology today is ubiquitous. When founding Atheros twenty years ago, Dr. Meng expounded three revolutionary ideas

Robust Baseband Compression Against Congestion in Packet-Based Fronthaul Networks Using Multiple Description Coding.

In modern implementations of Cloud Radio Access Network (C-RAN), the fronthaul transport network will often be packet-based and it will have a multi-hop architecture built with general-purpose switches using network function virtualization (NFV) and software-defined networking (SDN). This paper studies the joint design of uplink radio and fronthaul transmission strategies for a C-RAN with a packet-based fronthaul network. To make an efficient use of multiple routes that carry fronthaul packets from remote radio heads (RRHs) to cloud, as an alternative to more conventional packet-based multi-route reception or coding, a multiple description coding (MDC) strategy is introduced that operates directly at the level of baseband signals. MDC ensures an improved quality of the signal received at the cloud in conditions of low network congestion, i.e., when more fronthaul packets are received within a tolerated deadline. The advantages of the proposed MDC approach as compared to the traditional path diversity scheme are validated via extensive numerical results.

Adaptive Transmission in Cellular Networks: Fixed-Rate Codes With Power Control Versus Physical Layer Rateless Codes

Adaptive transmission schemes are a crucial aspect of radio design for future wireless networks. This paper studies the performance of two classes of adaptive transmission schemes in cellular downlink. One class is based on physical layer rateless codes with constant transmit power and the other uses fixed-rate codes in conjunction with power adaptation. Using a simple stochastic geometry model for the cellular downlink, the focus is to compare the adaptivity of fixed-rate codes with power adaptation to that of physical layer rateless codes only. The performance of both the rateless and fixed-rate coded adaptive transmission schemes are compared by evaluating the typical user success probability and rate achievable with the two schemes. Based on both the theoretical analysis and simulation results, it is clearly shown that the fixed-rate codes require power control to maintain good performance, whereas the physical layer rateless codes with constant power can still provide robust performance.

Design and Implementation of Adaptive Multi-Tap Analog Interference Canceller

Due to the severity of self-interferences, analog interference canceller is an essential part of a full duplex radio system. As the self-interference can potentially be even much stronger than the received signal, it must be meritoriously suppressed before analog-to-digital conversion. This paper is aimed to provide an optimal radio frequency domain multi-tap interference cancellation design. To this end, the following two key problems are addressed: the hardware design problem and the adaptive weight adjusting problem. For optimal hardware design, a trade-off between widening effective delay range and maximizing the minimum cancellation capability is formulated. The principles and guidelines for optimal solution and hardware parameter design are derived. We also formulate adaptive weight adjusting as a multi-dimensional optimization problem, which is proved to be non-convex while adjusting the attenuators and phase shifters independently. By using a coordinate transformation technique, it is then converted into a convex optimization problem, and a convergent iterative algorithm based on the gradient descent method is applied to obtain the global optimum. The hardware implementation and experimental results substantiated the effectiveness of the proposed principles and algorithms.

An radio frequency coil design for rat spinal magnetic resonance imaging at 9.4 T

For rat spinal magnetic resonance imaging (MRI) experiments, due to the lower main magnetic field strength, shallower detected depth and poor spatial compatibility of the traditional radio frequency (RF) coil, the image signal-to-noise ratio (SNR) of rat spinal was rather lower. In this paper, a RF coil for rat spinal MRI at 9.4 T was developed to improve the image quality and at the same time to avoid the space limitation while scanning in special conditions (cardiac catheterization, etc.). In this article, open birdcage structure was built and magnetic field distribution was calculated. The phantom and rat spine MRI imaging were experimented at 9.4 T to verify the advantage of the coil in rat spine MRI application.

Spectrum Sensing methods for Cognitive Radio

The electromagnetic spectrum is a characteristic asset. The present spectrum authorizing plan is not able to oblige quickly growing demand in wireless communication due to the static spectrum allocation strategies. This allocation prompts increment in spectrum scarcity issue. Cognitive radio (CR) technology is a propelled remote radio design which aims to expand spectrum utilization by distinguishing unused and under-used spectrum in rapidly evolving environments. Spectrum sensing is one of the key strategy for cognitive radio which detects the presence of primary client in authorized licensed frequency band utilizing dynamic spectrum assignment policies to utilize unused spectrum. In many areas cognitive radio frameworks coexist with other radio frameworks, utilizing the same spectrum yet without creating undue interference. The most simple and easy to implement sensing technique is energy detection. Since, it does not require any prior information of the signal present in the frequency band under observation. In this thesis, several spectrum sensing technique is introduced but the main work is carried for energy detection methods. Energy detection technique is implemented using VHDL for pseudo random sequence generator.

Performance, Power, and Area Design Trade-Offs in Millimeter-Wave Transmitter Beamforming Architectures

Millimeter wave (mmW) communications is the key enabler of 5G cellular networks due to vast spectrum availability that could boost peak rate and capacity. Due to increased propagation loss in mmW band, transceivers with massive antenna array are required to meet link budget, but their power consumption and cost become limiting factors for commercial systems. Radio designs based on hybrid digital and analog array architectures and the usage of radio frequency (RF) signal processing via phase shifters have emerged as potential solutions to improve energy efficiency and deliver performances close to digital arrays. In this paper, we provide an overview of the state-of-the-art mmW massive antenna array designs and comparison among three architectures, namely digital array, sub-array, and fully-connected hybrid array. The comparison of performance, power, and area for these three architectures is performed for three representative 5G use cases, which cover a range of pre-beamforming SNR and multiplexing regimes. This is the first study to comprehensively model and analyze all design aspects and criteria including: 1) optimal linear precoder, 2) impact of quantization error in DAC and phase shifters, 3) RF signal distribution network, 4) power and area estimation based on state-of-the-art mmW circuits including baseband precoding, digital signal distribution, DACs, oscillators and mixers, phase shifters, RF signal distribution, and power amplifiers. The results show that the digital array is the most power and area efficient compared against optimal design for each architecture. Our analysis shows digital array benefits greatly from multi-user multiplexing. The analysis also reveals that sub-array is limited by reduced beamforming gain due to array partitioning, and system bottleneck of the fully-connected hybrid architecture is the excessively power hungry RF signal distribution network.

SWORD: Towards a Soft and Open Radio Design for Rapid Development, Profiling, Validation and Testing

The vision, as we move to future wireless communication systems, embraces diverse qualities targeting significant enhancements from the spectrum, to user experience. Newly-defined air-interface features, such as large number of base station antennas and computationally complex physical layer approaches come with a non-trivial development effort, especially when scalability and flexibility need to be factored in. In addition, testing those features without commercial, off-the-shelf equipment has a high deployment, operational and maintenance cost. On one hand, industry-hardened solutions are inaccessible to the research community due to restrictive legal and financial licensing. On the other hand, research-grade real-time solutions are either lacking versatility, modularity and a complete protocol stack, or, for those that are full-stack and modular, only the most elementary transmission modes are on offer (e.g., very low number of base station antennas). Aiming to address these shortcomings towards an ideal research platform, this paper presents SWORD, a SoftWare Open Radio Design that is flexible, open for research, low-cost, scalable and software-driven, able to support advanced large and massive Multiple-Input Multiple-Output (MIMO) approaches. Starting with just a single-input single-output air-interface and commercial off-the-shelf equipment, we create a software-intensive baseband platform that, together with an acceleration/profiling framework, can serve as a research-grade base station for exploring advancements towards future wireless systems and beyond.

HYGIENIC ASSESSMENT OF WORKING CONDITIONS IN RADIO-ELECTRONIC COMPONENT PRODUCTION

Findings on the hygienic assessment of working conditions in radio-electronic component development and production at a modern enterprise producing capacitors, microcircuits, resistors and semiconductor devices are reported. Working conditions of employees engaged in radio-electronic component development (developers, designers) and production (photolithographers, wiremen, radio-electronic component and semiconductor device assemblers, adjusters and quality control inspectors) were studied. Hygienic studies of the working environment and working process factors were carried out to assess working conditions: workplace noise and magnetic field levels, microclimatic parameters, illuminance, the air pollution by chemicals. Time studies were performed to evaluate the heaviness and intensity of the work process. As a result of our studies, the main adverse factors were identified to assess worker health risks. Working conditions in job groups engaged in radio electronic component design were evaluated as harmful of 3 class, 1 degree. Working process intensity caused by sensory and mental load was found to be the major adverse factor. Working conditions in the job group engaged in experimental and small-scale production are characterized by exposure to “low-intensity factors”. Visual strain and fixed working posture are common for such jobs as radio electronic device wireman and quality control inspector using optical equipment in their work, which rates the heaviness of their working process as harmful working conditions. Our findings are intended to be used to define main harmful factors for the health risk assessment of radio component production workers, to carry out a comprehensive occupational health risk assessment, identifying job and long-term employment duration risk groups, to develop risk management measures. Our findings can provide a scientific rationale and contribute to the development of a complex of hygienic and preventive medical measures to be introduced into the practice of health protection service.