Metrology for 5G and Emerging Wireless Technologies
Metrology has a pivotal role to ensure the vision of fifth generation (5G) and emerging wireless technologies to be realised. It is essential to develop the underpinning metrology in response to the high demand for universal, dynamic, and data-rich wireless applications. As new technologies for 5G and beyond increasingly emerge in the arena of modern wireless devices/systems, the standards bodies, industries, and research communities are facing the challenge of diverse technological requirements, and on verifying products that meet desired performance parameters. This edited book is the first to focus on metrology for current and future wireless communication technologies. It presents a comprehensive overview of the state-of-the-art measurement capabilities, testbeds and relevant R&D activities for 5G and emerging wireless technologies at a wide range of frequencies up to THz frequency bands. Several real-world field trials and use cases are also presented. The book focuses on R&D of measurement techniques and metrology for 5G and beyond that underpin all aspects, from signals, devices, antennas, systems and propagation environments to RF exposure. The presented materials describe advances in the triad of measurement system design, measurement techniques, and underpinning metrology required to cover many wireless communications aspects. This book, Metrology for 5G and Emerging Wireless Technologies provides timely support to industry, academia, standard bodies and NMIs during the development of 5G and emerging wireless technologies and will support readers to enable further metrological R&D activities.
Inspec keywords: wireless channels; mobile antennas; millimetre wave communication; array signal processing; antenna arrays; 5G mobile communication; millimetre wave propagation; MIMO communication
Other keywords: research and development; wireless channels; array signal processing; testing; millimetre wave communication; millimetre wave propagation; antenna arrays; MIMO communication; 5G mobile communication; mobile antennas
Subjects: Signal processing and detection; Antenna arrays; Mobile radio systems; General electrical engineering topics
- Book DOI: 10.1049/PBTE099E
- Chapter DOI: 10.1049/PBTE099E
- ISBN: 9781839532788
- e-ISBN: 9781839532795
- Page count: 766
- Format: PDF
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Front Matter
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1 Introduction to metrology for 5G and emerging wireless technologies
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This chapter introduces (1) the scope of the book, including the definition of metrology and its relationship to measurement traceability, standardisation and national measurement system (NMS); (2) the global initiatives, standardisation activities and technology trends in fifth generation (5G) and emerging wireless technologies, as well as an overview of global metrological research and development (R&D) activities; and (3) the structure of the book, including brief highlights of each chapter.
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Part I. Waveform metrology
2 Metrology for 5G link adaptation and signal-to-interference-plus-noise ratio
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This chapter first provides background information about the digital modulations used in fourth generation (4G) and 5G. It then defines the SINR and its relation to error vector magnitude (EVM) used as the means for a mobile terminal to predict its SINR where the sources of interference are unknown. Finally, it will discuss how mobile terminals are tested in an over-the-air (OTA) testing environment for purposes of conformance testing the estimation of SINR, which is an important aspect of standardisation within mobile terminals.
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Part II. Device metrology
3 Non-linear measurements for 5G devices and the associated uncertainties
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This chapter describes a selection of measurement techniques and considerations which address the above challenges presented by 5G RF requirements. The subject matter is divided into the following four sections: RF instrumentation used for common device measurements and the calibration process used to remove their main sources of error; the use of 'load-pull' measurements to characterise the response of power transistors across a range of source and load impedances; X-parameters, a popular nonlinear behavioural model used to capture the response of nonlinear devices for use in design simulations; and practical limitations of RF measurements and techniques for evaluating their associated uncertainties.
4 Multiphysics measurements of RF/microwave power amplifiers
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The focus of this chapter is to motivate the need to treat high-power RF, microwave, and mm-wave transistors as distributed multiphysical systems and this in turn motivates the need to develop new measurement methodologies.
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Part III. Antenna metrology
5 A metrological millimeter wave hybrid beamforming testbed with a large antenna array
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This chapter has presented the insight methodologies on how to design, implement, and evaluate a width-bandwidth mm-wave fully connected hybrid beamforming metrological testbed with a large antenna array. The focus has been given on discussions include testbed design, calibration procedures, experimental evaluations, as well as the critical factors to consider for their practical implementation. If RF harmonics and spurious signal issues are avoided, one envisages that the testbed could be setup to work between 25 and 30 GHz with 2-GHz instantaneous bandwidth. Each of the phase shifters and attenuators in the mm-wave fully connected hybrid beamformer has six separate DIO control bits. Apart from describing the calibration procedures for the phase and amplitudes of the established fully connected hybrid beamformer system, the linearity, phase, and attenuation performance of the beamformer system between 25.5 and 26.5 GHz have been evaluated as well as the beamforming and link performance of a 128-element planar phased array at 26 GHz where the measured radiation patterns with and without amplitude tapering are compared.
6 Assessment of broadband sources and defocusing effects of compact antenna test range for 5G antenna testing
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In this chapter, some broadband feeds like dual ridge horns and Vivaldi-type printed antennas are analysed numerically to understand the phase centre variation as well as the 1-dB beamwidth. Another topic, covered at the end of the chapter, to bear in mind when using compact ranges, is the potential for high fields to be present at the feed with the potential to damage the electronics of the receive system used in the measurement. The same metrics used in compact ranges can be used for other plane wave generation devices.
7 International intercomparison campaigns for mobile communication antenna characterizations towards 5G and beyond
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This chapter provides an overview of the international intercomparison campaigns, mainly in EurAAPs, detailing those involving mobile telecommunication antenna characterizations where the gained experience are exploited towards characterization of emerging antenna systems for 5G and beyond. In particular, Section 7.1 gives a brief overview of the interlaboratory evaluations and on the background, history and management of EurAAP intercomparison campaigns. Section 7.2 describes the past and present EurAAP campaigns and also future campaigns with millimetre-wave (mm-wave) chip reference antennas for 5G applications. The procedure, reported in Section 7.3, to correlate the measurements from different laboratories has been reviewed in the last years. Terminal and infrastructure mobile telecommunication antennas, like base transceiver station (BTS) and multiple-input-multiple-output (MIMO) antennas, have been the reference antennas of EurAAP intercomparison campaigns concluded in recent years as detailed in Section 7.4. The data collected in the frame of these campaigns will be used in the next future constituting a benchmark for new facility self-evaluation EurAAP activities. Finally, in Section 7.5, the future trends for intercomparison campaigns for the characterization of emerging antennas for 5G and beyond are outlined. Conclusions are drawn in Section 7.6.
8 Numerical and experimental analyses of wearable antennas, including novel fabrication and metrology techniques
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Most fifth-generation (5G) mobile network applications require wearable antennas to be unobtrusive, low-profile, low-power and electrically small. Such antennas are a crucial element in wearable body-centric wireless system designs for delivering 5G user's experience. Wearable antennas can be employed in a wide range of applications from communicating, harvesting energy to sensing capabilities. For this purpose, fabrics and novel materials such as graphene have been explored in order to cope with the wearable device demands in terms of flexibility, conformability and lightweight. Similarly, novel fabrication techniques for wearable antenna prototyping such as screen printing, inkjet printing, embroidery and cutters have been investigated to exploit the unique characteristics of various materials. These innovative fabrication methods allow a high degree of fabrication precision enabling their uptake for 5G applications. Due to power absorption by lossy human body tissues, a distorted radiation pattern and lower radiation efficiency are envisaged when they are worn on and at proximity to the body. Furthermore, when designing the antenna, the body proximity effects must be considered to prevent significant antenna detuning and the consequent mismatch. Numerical and experimental human body phantoms are used with a view to simulate its impact. This chapter presents an analysis of novel fabrication methods for wearable antennas, methodologies and measurement techniques to characterise their performance in a dynamic body-worn communication environment. This chapter delivers a review of different novel fabrication techniques for wearable antennas such as various printing processes, machine embroidery and laser methods. Follow by a metrology section, where numerical and experimental human phantoms are explained and durability tests described. Three examples of 5G wearable antennas for different frequencies and their on-body performance characterisation are provided. Finally, it is closed with a summary of the outcomes achieved in this chapter and future prospects of the research.
9 5G mm-wave mobile handset antenna system, measurements and evaluations
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Nowadays, the large number of services provided by mobile phones drives the usage of the millimetre-wave (mm-wave) frequency range for the upcoming fifth-generation (5G) mobile communication system, in order to provide wider bandwidths that support high-throughput data transfer. However, the propagation environment becomes hostile at higher frequencies, due to larger path loss, so higher gain antenna arrays, that are able to achieve wide beam steering range, are proposed to be embedded in 5G mobile terminals. In order to assess the radio frequency (RF) performance of the mm-wave mobile handset antenna systems, new figures of merit are specified by the Third-Generation Partnership Project (3GPP). The RF requirements take into account multiple factors that affect the performance of the mm-wave antenna, such as the challenging electromagnetic environment inside the phone-housing and the high mobility. In addition, the blockage from the user limits the antenna coverage range. Since it is difficult for mm-wave signal to propagate through the human body, an accurate model of the user shadowing is required to be included in the mm-wave cellular network planning. In this chapter, the new metrics to evaluate the performance of mm-wave antenna systems are presented, and both traditional and novel approaches are used for the measurements of mm-wave mobile handsets mock-ups. The user blockage is investigated in different scenarios and a new model is drawn.
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Part IV. System OTA metrology
10 Over-the-air testing metrology of 5G radios
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In this chapter, the focus is given on OTA testing methodologies of 5G radios. The first part focuses on the wireless system performance testing, where the objective is to evaluate 5G radio performance, e.g., throughput, under realistic spatial channel conditions. Two standard OTA testing methods, namely, the multiprobe anechoic chamber (MPAC) and radiated two-stage (RTS) method, are detailed. The second part focuses on the RF testing, where the goal is to test 5G RF parameters under ideal plane wave conditions. The focus is given on a novel midfield testing method. Other mature RF testing methods, e.g., direct far-field(DFF), compact antenna testing range (CATR), plane wave generator (PWG), and near- to far-field (NF-FF) transformation method, can be found in many references in the literature and therefore are not detailed in this chapter. The third part introduces the current status of OTA testing of 5G radios in standardization, where both wireless system performance testing and RF testing are discussed.
11 Over-the-air testing with synthetic-aperture techniques
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This chapter provides an overview of synthetic-aperture systems for applications related to wireless communications. By sampling the fields propagating through a spatial volume at many locations, synthetic-aperture-system measurements allow the reconstruction of the temporal and spatial characteristics of the channel in post-processing. While often used to characterize spatially diverse multipath environments, synthetic-aperture systems can also provide reference measurements for assessing the over-the-air (OTA) performance of a wireless device under test (DUT).
12 Using reverberation chambers for mm-wave over-the-air and electromagnetic compatibility measurements
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As the fifth-generation (5G) wireless communication system is deployed widely, over-the-air (OTA) testing becomes the main method to estimate the radiated frequency (RF) performance of 5G devices. In 5G, there are roughly two wide frequency ranges specified in 3GPP (Third Generation Partnership Project). One is what we usually call sub-6 GHz (FR1) and the other is millimetre-wave (FR2) band. In FR1, we can still adopt the traditional way to test devices, which utilises cables and connectors to connect devices. However, when the frequency comes to FR2, it may not be suitable for conducting a method to measure the multi-antenna devices. If the conducting measurement is adopted, cables and connectors will be needed to connect antennas, which are costly and have not enough space. Besides the previous disadvantages of the traditional method for millimetre-wave (mm-wave) measurements, we need to use the OTA method to characterise the system, e.g., beamforming test. With the development of 5G technology, the OTA test will be used widely to estimate the performance of the wireless devices. Over the past decade, there have been significant industry efforts to move reverberation chambers (RCs) into the mainstream of OTA wireless device testing. This chapter gives an overview of OTA and electromagnetic compatibility (EMC) measurements in RCs. The measurement procedure is introduced in detail. This chapter is organised as follows: the RC background is introduced in Section 12.1, OTA measurements are introduced in Sections 12.2 and 12.3, and EMC measurements are detailed in Sections 12.4-12.6.
13 Over-the-air testing for autonomous vehicle communications
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The future of transportation lies with the development of connected and automated mobility (CAM) solutions, which include intelligent and self-driving vehicles, with a large research and engineering community investigating and overcoming the technical challenges in their development. Although safest CAM solutions are expected to be autonomous and fully self-supporting, the ability to receive and share information with other vehicles or infrastructure holds promise to lead to advanced environment and traffic awareness as well as cooperative behaviour functions. Fast and reliable wireless communication between vehicles and infrastructure will likely rely on 5G NR and beyond technology, with access to already existing cellular communication infrastructure as well as to newly deployed infrastructure for the higher frequency bands that provide access to larger bandwidths. The work presented here evaluates the quality of such over-the-air, vehicle-to-infrastructure signals in a mini-urban campus environment for both low and high carrier frequencies, by comparing the results from detailed channel sounding measurements with signal quality parameters such as the error vector magnitude and the established data throughput. This provides insights into the relationships between fundamental parameters used to establish vehicular communication channel models and the quality of service parameters used in vehicular applications and international standards.
14 Performance evaluation and compliance testing of 5G/6G base stations, user-devices and systems
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Antennas and electromagnetic characterizations have been challenging topics for more than 50 years. The measurement of an antenna or device is commonly an evaluation of the radiation properties in the far field (FF) assuming that the origin is positioned at an infinite distance from the observation point. The effort to perform the measurement in sufficiently good approximation to FF condition is a paradox since a major part of modern communications supported by antennas and devices occur at a finite distance and often in near field (NF). The FF condition is also often referred to as plane wave condition since radiation tends to approximate a plane wave at infinity. Far from the antenna or device origin, electromagnetic radiation will have spread out sufficiently that it will appear as uniform amplitude and phase on a plane perpendicular to its direction of travel. Thus, at sufficient distance an antenna will appear to radiate plane waves in all directions. Due to reciprocity, the FF radiation of an antenna can also be measured by exposing the entire antenna locally to an approximate plane wave.
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Part V. Propagation channel metrology
15 Metrology for channel sounding
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Nowadays, fifth-generation (5G) wireless technology has been applied to various aspects of our daily life, such as public transportation and shopping malls. In addition to these daily applications, compared with the traditional third-generation/fourth-generation (3G/4G) system, 5G new radio (NR) is widely used in other scientific research and technology scenarios because of its ultrahigh traffic volume density, ultrahigh connection density, ultrahigh mobility, and other diversified characteristics. A variety of technologies are used to serve the end users, such as massive multiple-input-multiple-output (mMIMO) channel models, millimetre-wave (mm-wave) communications, ultra dense networks, and device-to-device (D2D) communications. Therefore, the main requirements of 5G NR channel models could be divided into five areas: (1) higher frequency and larger bandwidth, (2) mMIMO, (3) spatial consistency and deal mobility, (4) wide-range propagation scenarios and diverse network topologies, and (5) high mobility. In general, channel sounders are divided into frequency-and time-domain-based methods according to different detection methods. The method based on the frequency domain is mainly implemented with a vector network analyser (VNA). A VNA measures the frequency-domain response of the wireless channel based on frequency-domain scanning and then obtains the time delay power profiles (PDP) of the wireless channel through Fourier transform. By setting a narrower IF signal bandwidth, a VNA can achieve a higher measurement dynamic range. Meanwhile, the delay estimation accuracy will be higher as the frequency-domain range of the scan increases. A MIMO channel sounder can also be realized based on a VNA. However, due to the long measurement time, the VNA-based channel sounder is only suitable for detecting and analysing static wireless channel scenarios.
16 Empirical mmWave channel measurements and modelling in indoor and outdoor complex environments for 5G communications
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Millimetre-wave (mmWave) communication systems have become one of the key technologies that are used in the fifth-generation (5G) of the mobile networks. The availability of large chunks of lightly licensed/unlicensed spectrum in the mmWave bands provide the opportunity to deliver revolutionary data rates in 5G systems compared to its predecessors. However, the characteristics of radio propagation channels in such frequency bands impose severe constraints on the design and deployment of such systems. For example, the transmitted signals over mmWave channels experience high attenuation, which can significantly limit the communication range and link reliability in practical systems. Such characteristics directly impact the system requirements for mmWave technology in terms of hardware, algorithms and even protocols. In the following, first we present an overview of mmWave technology and the current efforts towards modelling their radio propagation channel. After introducing the necessary theoretical tools and terminology related to channel modelling, we present empirical mmWave channel measurements and modelling in realistic indoor and outdoor environments with the focus on 5G communications. The results are focused on 26, 32 and 39 GHz bands with 2-GHz bandwidths based on several extensive measurement campaigns that were conducted at the University of Surrey, United Kingdom.
17 Massive MIMO: real-world trials and practical solutions for 5G and beyond
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This chapter describes the world's first real-time 128-antenna M-MIMO testbed implementation and how it was used to evaluate the technology in real-world trials. Subsequently, these trials revealed insights on the structure of signal to interference plus noise ratio (SINR) estimation and a mechanism of predicting error vector magnitude (EVM) for connected terminals in a multi-user configuration.
18 Millimetre-wave radio propagation measurements towards 5G NR standardizations
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This chapter deals with the topic related to millimetre-wave (mmWave) radio propagation measurements and indoor channel characteristics from 5G mmWave new radio (NR) standardization aspect. The mmWave wireless channel, in some way as the traditional microwave band channel, is characterized by series of relevant spatial-temporal propagation parameters as a function of traversed distance, carrier frequency and application scenarios; however, mmWave signals experience severe path loss and are more sensitive to physical blockages due to the relatively shorter wavelength. Accordingly, it is hoped that this will allow readers to become acquainted with the mmWave channel sounding methodologies and propagation characteristics across multiple frequency bands in indoor environments.
19 Terahertz communications on various beyond 5G real-world use cases for IoT, railway, train, drone communications—propagation channel characterization and challenges
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In recent decades, the demand for higher data rates has almost doubled year by year. Very large swaths of the spectrum (tens to hundreds of gigahertz) are still available in the THz band, which is unused for communications so far. In this chapter, a comprehensive introduction of various real-world use cases at THz band for 5G and beyond wireless communications as well as their propagation channel characterizations and challenges are presented. We provide a brief survey and most relevant scenarios for THz-band communications, including IoT, railway, train, drone, and wireless connections on a desktop. Last but not least, we highlight new concerns in THz communication systems from the meteorological impact, beam split effect of large antenna arrays, and multifield noise sources from devices themselves. Thus, this chapter schemes the foundation for future work that aims to streamline the design, simulation, and development of 5G and beyond THz communication systems.
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Part VI. RF exposure metrology
20 Measurement of 5G new radio-base stations
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The ability to measure the exposure of new radio (NR)-base stations is an important requirement towards the deployment of 5G in our countries. According to manufacturers, the 5G technology allows larger transmission capacity as compared to the previous generations. Different techniques are used to increase the transmission capacity, one of them being beamforming. The 5G technology is thus very attractive, but at the same time significantly more complex than the previous generations of mobile communication technologies.
21 Metrology for RF-exposure from massive MIMO system
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This chapter first makes a case about the importance of the metrology form MIMO when it comes to RF-exposure in order to provide meaningful data for the regulatory bodies so they can, in turn, make informed and sensible decisions on how to set exposure limits for 5G BS. It then describes some of the existing works on the topic and focus in more detail on experimental work. It then explains the way forward that is currently taken to define how to measure and regulate the RF-exposure of 5G BS, by mainly using statistical approaches to better reflect the beamforming nature of the mMIMO transmission. Statistical models based on simple theory and system level simulations have first been proposed, before data from real 5G BS have been acquired to confirm the results of these models. The main finding is that using statistical approaches for defining the exclusion zone of 5G BS seems reasonable in comparison with the traditional method that creates unrealistically large exclusion zones. However, more works need to be done to fully understand how the RF-exposure generated by mMIMO BS fluctuates over time and space; a metrology method based on a fully reconfigurable 5G mMIMO testbed is fully detailed to do so. The main findings of this method are: the RF exposure decays in a quadratic manner as a function of the distance, even when there is no main beam pointing directly into this direction; the peak of the RF exposure at a particular point in space is reached as an active beam is directly steered towards it; the overall RF-exposure at a given point increases with the number of users that are served simultaneously by the mMIMO BS and this effect is more significant close to the mMIMO BS than further away; and the RF-exposure of a mMIMO BS varies significantly as a function of the amount of data it transmits.
22 Conclusions and future perspectives
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This book presents a comprehensive overview of the state-of-the-art measurement capabilities, testbeds and relevant research and development (R&D) activities for fifth generation (5G) and emerging wireless technologies at a wide range of frequencies up to THz frequency bands. Several real-world field trials and use cases are also presented, for example, massive multiple-input-multiple-output(mMIMO), autonomous vehicles, drones, railways and Internet of Things (IoT). The focus has been on R&D of measurement techniques and metrology for 5G and beyond that underpin all aspects, from new radio (NR) signals, devices, antennas, systems and propagation environments to RF exposure. The presented material will support readers from universities, industry, standard bodies and national measurement institutes to enable further metrological R&D activities by describing advances in the triad of measurement system design, measurement techniques and underpinning metrology required to cover many communication aspects from the network-edge to the network-core. In next section, the open challenges that seed the future research directions on metrology for 5G and emerging wireless technologies are discussed.
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Back Matter
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