Multidimensional Index Modulation for 5G and Beyond Wireless Networks

This study examines the flexible utilization of existing IM techniques in a comprehensive manner to satisfy the challenging and diverse requirements of 5G and beyond services. After spatial modulation (SM), which transmits information bits through antenna indices, application of IM to orthogonal frequency division multiplexing (OFDM) subcarriers has opened the door for the extension of IM into different dimensions, such as radio frequency (RF) mirrors, time slots, codes, and dispersion matrices. Recent studies have introduced the concept of multidimensional IM by various combinations of one-dimensional IM techniques to provide higher spectral efficiency (SE) and better bit error rate (BER) performance at the expense of higher transmitter (Tx) and receiver (Rx) complexity. Despite the ongoing research on the design of new IM techniques and their implementation challenges, proper use of the available IM techniques to address different requirements of 5G and beyond networks is an open research area in the literature. For this reason, we first provide the dimensional-based categorization of available IM domains and review the existing IM types regarding this categorization. Then, we develop a framework that investigates the efficient utilization of these techniques and establishes a link between the IM schemes and 5G services, namely enhanced mobile broadband (eMBB), massive machine-type communications (mMTC), and ultra-reliable low-latency communication (URLLC). Additionally, this work defines key performance indicators (KPIs) to quantify the advantages and disadvantages of IM techniques in time, frequency, space, and code dimensions. Finally, future recommendations are given regarding the design of flexible IM-based communication systems for 5G and beyond wireless networks.Comment: This work has been submitted to Proceedings of the IEEE for possible publicatio

Dual-band circularly polarized MIMO DRA for sub-6 GHz applications

In this article, a dual-band circularly polarized multiple-input-multiple-output (MIMO) dielectric resonator antenna (DRA) is proposed for 3.5 and 5.5 GHz bands, both being located under 6 GHz. Known as sub-6 (or as mid-band), they provide good coverage and capacity in the newly targeted fifth-generation (5G) systems. The proposed structure consists of two ring DRAs (RDRAs) etched on a 0.8 mm thick RT Duroid substrate. Measured impedance bandwidths in broadside direction are 3.1-3.75 GHz (19%) and 5.3-5.6 GHz (9.4%) and circular polarization (CP) bandwidths are 3.425-3.6 GHz (5%) and 5.45-5.55 GHz (2%), respectively. CP is achieved by exciting HE modes using two probes placed orthogonaly to each other, that is, at an azimuthal angular distance of 90∘. Varying the lengths of the probe allows achieving the necessary time-phase quadrature between modes. Comparison between recent multiband circularly polarized MIMO DRAs and proposed prototype has revealed that CP bandwidth in both bands is one of the highlighting advantages of the present configuration

Analysis of millimetre-wave polarization diverse multiple-input multiple-output capacity

Millimetre-waves offer the possibility of wide bandwidth and consequently high data rate for wireless communications. For both uni- and dual-polarized systems, signals sent over a link may suffer severe degradation due to antenna misalignment. Orientation robustness may be enhanced by the use of mutual orthogonality in three dimensions. Multiple-input multiple-output polarization diversity offers a way of improving signal reception without the limitations associated with spatial diversity. Scattering effects often assist propagation through multipath. However, high path loss at millimetre-wave frequencies may limit any reception enhancement through scattering. We show that the inclusion of a third orthogonal dipole provides orientation robustness in this setting, as well as in a rich scattering environment, by means of a Rician fading channel model covering all orientations for a millimetre-wave, tri-orthogonal, half-wave dipole transmitter and receiver employing polarization diversity. Our simulation extends the analysis into three dimensions, fully exploiting individual sub-channel paths. In both the presence and absence of multipath effects, capacity is observed to be higher than that of a dual-polarized system over the majority of a field of view.Nicholas P. Lawrence, Brian W.-H.Ng, Hedley J. Hansen, and Derek Abbot

Eight-Element Compact UWB-MIMO/Diversity Antenna with WLAN Band Rejection for 3G/4G/5G Communications

An eight element, compact Ultra Wideband-Multiple Input Multiple Output (UWB-MIMO) antenna capable of providing high data rates for future Fifth Generation (5G) terminal equipments along with the provision of necessary bandwidth for Third Generation (3G) and Fourth Generation (4G) communications that accomplishes band rejection from 4.85 to 6.35 GHz by deploying a Inductor Capacitor (LC) stub on the ground plane is presented. The incorporated stub also provides flexibility to reject any selected band as well as bandwidth control. The orthogonal placement of the printed monopoles permits polarization diversity and provides high isolation. In the proposed eight element UWB-MIMO/diversity antenna, monopole pair 3-4 are 180o mirrored transform of monopole pair 1-2 which lie on the opposite corners of a planar 50 x 50 mm2 substrate. Four additional monopoles are then placed perpendicularly to the same board leading to a total size of 50 x 50 x 25 mm3 only. The simulated results are validated by comparing the measurements of a fabricated prototype. It was concluded that the design meets the target specifications over the entire bandwidth of 2 to 12 GHz with a reflection coefficient better than -10 dB (except the rejected band), isolation more than 17 dB, low envelope correlation, low gain variation, stable radiation pattern, and strong rejection of the signals in the Wireless Local Area Network (WLAN) band. Overall, compact and reduced complexity of the proposed eight element architecture, strengthens its practical viability for the diversity applications in future 5G terminal equipments amongst other MIMO antennas designs present in the literature.Comment: 25 page

Antenna System Design for 5G and Beyond – A Modal Approach

Antennas are one of the key components that empower a new generation of wireless technologies, such as 5G and new radar systems. It has been shown that antenna design strategies based on modal theories represent a powerful systematic approach to design practical antenna systems with high performance. In this thesis, several innovative multi-antenna systems are proposed for wireless applications in different frequency bands: from sub-6 GHz to millimeter-wave (mm-wave) bands. The thesis consists of an overview (Part I) and six scientific papers published in peer-reviewed international journals (Part II). Part I provides the overall framework of the thesis work: It presents the background and motivation for the problems at hand, the fundamental modal theories utilized to address these problems, as well as subject-specific research challenges. Brief conclusions and future outlook are also provided. The included papers of Part II can be divided into two tracks with different 5G and beyond wireless applications, both aiming for higher data rates.In the first track, Papers [I] to [IV] investigate different aspects of antenna system design for smart-phone application. Since Long Term Evolution (LTE) (so-called 3.5G) was deployed in 2009, mobile communication systems have utilized multiple-input multiple-output antenna technology (MIMO) technology to increase the spectral efficiency of the transmission channel and provide higher data rates in existing and new sub-6 GHz bands. However, MIMO requires multi-antennas at both the base stations and the user equipment (mainly smartphones) and it is very challenging to implement sub-6 GHz multi-antennas within the limited space of smartphones. This points to the need for innovative design strategies. The theory of characteristic modes (TCM) is one type of modal theory in the antenna community, which has been shown to be a versatile tool to analyze the inherent resonance properties of an arbitrarily shaped radiating structure. Characteristic modes (CMs) have the useful property of their fields being orthogonal over both the source region and the sphere at infinity. This property makes TCM uniquely suited for electrically compact MIMO antenna design.In the second track, Papers [V]-[VI] investigate new integrated antenna arrays and subarrays for the two wireless applications, which are both implemented in a higher part of the mm-wave frequency range (i.e. E-band). Furthermore, a newly developed high resolution multi-layer “Any-Layer” PCB technology is investigated to realize antenna-in-package solutions for these mmwave antenna system designs. High gain and high efficiency antennas are essential for high-speed wireless point-to-point communication systems. To meet these requirements, Paper [V] proposes directive multilayer substrate integrated waveguide (SIW) cavity-backed slot antenna array and subarray. As a background, the microwave community has already shown the benefits of modal theory in the design and analysis of closed structures like waveguides and cavities. Higher-order cavity modes are used in the antenna array design process to facilitate lower loss, simpler feeding network, and lower sensitivity to fabrication errors, which are favorable for E-band communication systems. However, waveguide/cavity modes are confined to fields within the guided media and can only help to design special types of antennas that contain those structures. As an example of the versatility of TCM, Paper [VI] shows that apart from smartphone antenna designs proposed in Papers [I]-[IV], TCM can alsobe used to find the desirable modes of the linear antenna arrays. Furthermore, apart from E-band communications, the proposed series-fed patch array topology in Paper [VI] is a good candidate for application in 79 GHz MIMO automotive radar due to its low cost, compact size, ability to suppress surface waves, as well as relatively wide impedance and flat-gain bandwidths

Multiple input multiple output dielectric resonator antenna with circular polarized adaptability for 5G applications

In this paper, the concept of the circularly polarized agile, multiple-input multiple-output (MIMO) dielectric resonator antenna (DRA) structure for fifth generation (5G) new radio application in mobile terminal is presented. Two prototypes have been fabricated, namely one with cylindrical DRA (CDRA) referred as A1 and a second one with ring DRA (RDRA) named as A2. These practical realizations of dual-port MIMO antennas have been mounted on a Rogers 5870 substrate of octagonal shape with proper ground architecture. The proposed dual-port MIMO antennas have been excited with conformal probes and L-type feed network aiming to achieve circular polarization (CP). Measured impedance bandwidth of A1 and A2 are 21.2% (3.15-3.9 GHz) and 22.2% (3.12-3.9 GHz), respectively. Moreover, for both antennas low mutual coupling between ports with minimum isolation of dB over entire impedance bandwidth has been obtained by using triangular head slots in the ground plane. Measured axial ratio bandwidths in broadside direction are 5.66% (3.26-3.45 GHz) and 4.25% (3.45-3.6 GHz), respectively. Maximum gains are 7.3 and 7.2 dBi, in that order. MIMO antenna parameters such as envelope correction coefficient, diversity gain (DG), mean effective gain and total active reflection coefficient are also calculated to verify MIMO performance parameters. The proposed antennas also demonstrate CP agility with insertion of concentric cylindrical shells of different radii

Statistical Review Evaluation of 5G Antenna Design Models from a Pragmatic Perspective under Multi-Domain Application Scenarios

Antenna design for the 5G spectrum requires analysis of contextual frequency bands, design of miniaturization techniques, gain improvement models, polarization techniques, standard radiation pattern designs, metamaterial integration, and substrate selection. Most of these models also vary in terms of qualitative & and quantitative parameters, which include forward gain levels, reverse gain, frequency response, substrate types, antenna shape, feeding levels, etc. Due to such a wide variety in performance, it is ambiguous for researchers to identify the optimum models for their application-specific use cases. This ambiguity results in validating these models on multiple simulation tools, which increases design delays and the cost of deployments. To reduce this ambiguity, a survey of recently proposed antenna design models is discussed in this text. This discussion recommended that polarization optimization and gain maximization are the major impact factors that must be considered while designing antennas. It is also recommended that collocated microstrip slot antennas, fully planar dual-polarized broadband antennas, and real-time deployments of combined slot antenna pairs with wide-band decoupling are very advantageous. Based on this discussion, researchers will be able to identify optimal performance-specific models for different applications. This discussion also compares underlying models in terms of their quantitative parameters, which include forward gain levels, bandwidth, complexity of deployment, scalability, and cost metrics. Upon referring to this comparison, researchers will be able to identify the optimum models for their performance-specific use cases. This review also formulates a novel Antenna Design Rank Metric (ADRM) that combines the evaluated parameters, thereby allowing readers to identify antenna design models that are optimized for multiple parameters and can be used for large-scale 5G communication scenarios

Tri-Orthogonal Polarisation Diverse Communications

This thesis investigates improving communication link coverage through triorthogonal polarisation diversity. Tri-orthogonal polarisation diversity exploits radiated electromagnetic energy transmission and reception in three orthogonal spatial directions with an aim to provide enhanced communication link performance. Original contributions to this branch of diversity are presented in areas of both software and hardware design. First, simulations are presented highlighting the benefit of tri-orthogonal polarisation diversity at both the transmitter and receiver over a range of terrestrial channel conditions. The results are presented in an easily understandable graphical format that results from a novel model design considering all antenna orientations. Orientation robustness at the antenna is demonstrated as a consequence of a tri-orthgonal polarisation diverse approach. Second, additional research is performed in order to extend the model into the field of satellite systems. The ionosphere is required to be modelled, and this is performed according to a novel vectorised approach using realtime ionospheric data and terrestrial magnetic field appreciation. Third, ionospheric modelling is incorporated into a non-geosynchronous satellite orbit channel model that provides an insight into the benefit of applying a tri-orthogonal polarisation diverse approach uniquely at the receiver. Novelty is provided in the form of a vectorised approach to simulation covering all antenna orientations in a field-ofview as observed from a satellite transmitter. This is extended over the orbits of three distinct satellite systems. Output is provided in graphical format and conclusions are drawn form the data which suggest that a tri-orthogonal polarisation diverse approach applied at the receiver provides an increase in reception performance. Fourth, an antenna is designed, simulated, constructed and tested that provides three orthogonal polarisations in a phase-centred differentially-fed package. Novelty is provided in the design being planar in nature, with three orthogonal modes being able to be transmitted from a single slot. Results emanating from the testing procedure demonstrate the benefits of the design in terms of diversity and extension to beamforming applications. Fifth, as an extension to the antenna design, a circularly polarised feeding arrangement is used together with an omnidirectional vertically polarised mode feed in an antenna and feed combination. This provides the possibility of a direct comparison with conventional circularly polarised techniques, such as those used in both terrestrial and satellite receive antennas. Sixth, the operational bandwidth of the omnidirectional vertically polarised mode is extended by adapting the design of the cavity wall resonating slots in a substrateintegrated monopole antenna while maintaining a planar structure. The electric monopole design demonstrates an increase in operating bandwidth from 2.5% to 56%. In the thesis, a tri-orthogonal polarisation diverse approach is shown to be beneficial to signal reception over a range of channels, both in the areas of terrestrial and satellite communications. The concept is demonstrated to be feasible in a planar structure. Triorthogonal polarisation diversity is likely to play an increasing role in the future as systems look to cope with an ever increasing data flow. The demand for content on mobile devices has forced massive growth in mobile data over the past two decades. This growth has recently reached saturation point, and so new avenues for extending growth have to be considered. A search for available bandwidth has lead research to focus on the mmWave section of the electromagnetic spectrum. The advent of the next generation of wireless connectivity, dubbed fifth generation or 5G, is now upon us (Rappaport et al. 2013b). With data traffic set to multiply by up to one thousand fold by 2020 (Qualcomm Inc. Accessed: 2014b, Qualcomm Inc. Accessed: 2014a, Li et al. 2014, Chin et al. 2014), as The Internet of Things (Ashton 2009, Cisco Inc. Accessed: 2014, Gubbi et al. 2013) enters into the fray, an overhaul of wireless design is somewhat overdue. For static point-to-point, or LoS systems, challenges exist according to the channel environment and temporal changes that may occur within. For any network that has a mobile component built in, where spatial position and alignment of transmitter and receiver change over time, signal propagation is additionally influenced by link geometry. In an increasingly mobile world, this presents challenges as increased coverage, one of the main focus points of the 5G system, will require efficient use of radiated electromagnetic energy. Conventional techniques for improving data rate have typically aimed at increasing performance at the transmitter. For terrestrial networks, a transmitter is typically stationary. Performance outweighs size constraints and so power amplification and combination may be used to excite antennas that flood a network cell with a strong linearly polarised transmitted signal. For commercial providers, this has proved a very successful technique, mainly as a result of the majority of wireless subscribers living in dense urban environments. For a linearly polarised wave, operating at conventional operating frequencies around 2 GHz, and transmitted with relatively high power, the urban environment typically provides assistance for signal reception at the receiver through diversity brought about by reflection, refraction and scattering or multipath due to the presence of buildings. Small misalignments in transmit and receive antennas are mitigated as the propagating signal wavelength is large and a relatively high transmit power establishes a relatively high signal-to-noise ratio, providing useful multipath effects over the channel. At certain receive positions, channel fading may occur when superposition of received multipath components effectively cancel each other. This may be mitigated through additional transmitters that are spaced appropriately; a concept known as spatial diversity that has been cited at mmWave frequencies (Smulders 2002, Park and Pan 2012). Diversity of signal is important in that it offers a greater possibility of a signal being received due to individuality of uncorrelated channel propagation for each diverse signal component. As more content is demanded by subscribers within an ever shrinking timeframe, a higher frequency of operation is typically required for a carrier wave capable of providing this service. Add in the context of mobility, and issues quickly appear. Beneficial effects on a linearly polarised signal operating at conventional low gigahertz frequencies arising from reflection, refraction, and scattering or multipath effects, assist signal reception. Relatively long wavelengths are subjected to many scatterers, and due to the relatively high transmit power involved, scattering effects provide diversity at the receiver in the form of many smaller receivable diverse signal components. These signal components are superpositioned either constructively or destructively, after diverse individual propagation through the channel, at the receiver to provide signal reception. At mmWave frequencies, due to a shrinking wavelength, the following issues arise: • increased path loss over a defined range due to spreading loss (Pozar 2011), and increased atmospheric absorption (Liebe et al. 1989). An obvious solution is to provide more transmit power at the transmitter. At higher frequencies, miniaturisation of devices limits this possibility as heat sinking becomes problematic. Amplifier non-linearity and unwanted third order intermodulation impact on system performance (Niknejad and Hashemi 2008, Hashemi and Raman 2016) • the beneficial effect of multipath fading may not exist in a mmWave terrestrial channel (Pi and Khan 2011), as a smaller wavelength typically implies a reduced beamwidth and less scatterers available for the LoS signal to scatter into useful smaller diverse signal components. Due to a relatively low transmit power involved, any scattering of a LoS signal into smaller, weaker diverse signal components may result in no received signal. As a result, cell range is reduced and more transmitters are required to provide coverage over a network • with a shrinking wavelength, relatively lower transmit power, and increased mobility, antenna misalignment becomes problematic. A drive for radiated power efficiency is paramount in providing the next generation of wireless networks. An ability to transmit signals into and receive signals from all angles is necessary (Rappaport et al. 2013b). The terahertz range, for example, offers extremely high transfer rates, although any small misalignment greatly affects rate. The use of dielectric mirrors is required to effectively steer the transmitted signal to its destination. Mitigation of misalignment becomes important in maintaining system performance. For the next generation of mobile wireless systems to operate within the mmWave section of the electromagnetic spectrum, a solution to extend range is to increase radiated energy in a direction of propagation, through beam steering techniques. Within a mobile context, this poses challenges, not least as the link geometry is variable. For terrestrial networks, conventional transmitted waveforms are mainly vertically polarised, or circularly polarised, and as such are mainly one dimensional, or two dimensional at best, in performance. To provide the next generation of wireless networks, a third dimension needs to be considered to provide efficient use of radiated electromagnetic energy. Frequency bands of interest for 5G systems differ from country to country. According to the US Federal Communications Commission (FCC), the mmWave region that will be studied ranges from 24–80 GHz (Rappaport et al. 2013b, Rappaport Accessed: 2014, Above Ground Level Media Group Accessed: 2015). One of the aims of 5G is to improve coverage (Rappaport et al. 2013b). One method that is being considered is the joining of terrestrial and satellite services into one seamless network that may be readily accessed by the subscriber at the receiver (Evans et al. 2005, Evans et al. 2015, Federal Communications Commission Accessed: 2016). Satellite networks provide their own specific challenges, as transmit power is limited to payload specifications, and coverage typically requires a satellite that is moving relative to the Earth’s surface. Once again we find ourselves facing the same three issues that we encountered within the terrestrial context of a mmWave channel. If we are to increase link performance in a satellite channel to complement any improvement in terrestrial channels then the following points need to be considered: • propagation using higher operating frequencies typically suffers from higher path losses (Liebe et al. 1989, Pozar 2011). In some circumstances this can be mitigated by higher transmit power, but not all. A satellite payload is subject to a strict payload capacity and this restricts the size of transmit power devices and hence available transmit power that can be launched into orbit • a lack of beneficial reflectors, refractors, and scatterers is observed during channel propagation as the signal is typically LoS, narrow in beamwidth, and weak due to higher path loss and lower transmit power (Pi and Khan 2011). Multipath effects may degrade system performance as signals are weak • an evolving link geometry that affects antenna alignment. Linear and circular polarised signals are only two dimensional in nature. Three dimensions need to be considered, and beam steering of radiated power to provide the required range is a requirement (Evans et al. 2005, Hong et al. 2014b). To ensure that the next generation of mobile systems are fully mobile, while providing increased data rate, we need to consider diversity in three dimensions. Beam steering of a transmitted signal with high gain in the direction of a receiver is one viable option, and in the context of full mobility, three dimensional signal transmission and reception appears a logical step to achieving this (Hong et al. 2014a). While at a terrestrial transmitter, it is suggested that size is not a constraint, it remains so for a satellite transmitter, as it is at a mobile receiver. This rules out spatial diversity as an approach to increasing system performance. One approach of increasing diversity within a confined volume is through polarisation techniques (Vaughan 1990). In this thesis, we investigate the benefit of a subset of this approach—tri-orthogonal polarisation diversity (Andrews et al. 2001). In effect, the concept provides at least one additional degree of freedom or layer of diversity over conventional techniques such as circular polarisation. Due to orthogonality in three directions, this approach has a wide field of view, and potentially offers diversity and improved system performance through beam steering in any unit direction. Tri-orthogonal polarisation diversity may be applied either at the transmitter, at the receiver, or at both. In Chapter 1 of the thesis, both novel software and hardware aspects of the research are highlighted. Overall, the research outcomes of this thesis from both simulation and measured results suggest that the concept of tri-orthogonal polarisation diversity is: • beneficial to wireless performance over a majority of antenna orientations • plausible for implementation within typical antenna volume constraints.Thesis (Ph.D.) -- University of Adelaide, School of School of Electrical and Electronic Engineering, 201

Antenna Design for 5G and Beyond

With the rapid evolution of the wireless communications, fifth-generation (5G) communication has received much attention from both academia and industry, with many reported efforts and research outputs and significant improvements in different aspects, such as data rate speed and resolution, mobility, latency, etc. In some countries, the commercialization of 5G communication has already started as well as initial research of beyond technologies such as 6G.MIMO technology with multiple antennas is a promising technology to obtain the requirements of 5G/6G communications. It can significantly enhance the system capacity and resist multipath fading, and has become a hot spot in the field of wireless communications. This technology is a key component and probably the most established to truly reach the promised transfer data rates of future communication systems. In MIMO systems, multiple antennas are deployed at both the transmitter and receiver sides. The greater number of antennas can make the system more resistant to intentional jamming and interference. Massive MIMO with an especially high number of antennas can reduce energy consumption by targeting signals to individual users utilizing beamforming.Apart from sub-6 GHz frequency bands, 5G/6G devices are also expected to cover millimeter-wave (mmWave) and terahertz (THz) spectra. However, moving to higher bands will bring new challenges and will certainly require careful consideration of the antenna design for smart devices. Compact antennas arranged as conformal, planar, and linear arrays can be employed at different portions of base stations and user equipment to form phased arrays with high gain and directional radiation beams. The objective of this Special Issue is to cover all aspects of antenna designs used in existing or future wireless communication systems. The aim is to highlight recent advances, current trends, and possible future developments of 5G/6G antennas