mmWave Spectrum Research Articles

High gain and circularly polarised metasurface suspended twin port Al2O3 based antenna for mm-wave 5G communication system

Abstract This article discusses design and analysis of two-port alumina ceramic based aerial in mm-wave spectrum. Aperture coupling stimulate ceramic and produce dual fundamental orthogonal field i.e. HEM11δx and HEM11δy mode. Important features of structured aerial are: (i) designed antenna produces the circular wave within 32.65-33.25 GHz; (ii) double negative unit cell based metasurface suspension enhances the antenna’s broadsided gain to 9.0 dBi; and (iii) orthogonal arrangement of aerial ports improve the separation to over 25 dB. Experimental outcomes confirm the working spectrum of design aerial in between 32.21-33.55 GHz. Directional pattern and decent assessment of diversity parameters prepares the planned aerial appropriate for 5G communication in mm-wave regime.

Unlicensed Spectrum Access and Performance Analysis for NR-U/WiGig Coexistence in UAV Communication Systems

Unmanned aerial vehicles (UAVs) are extensively employed in pursuit, rescue missions, and agricultural applications. These operations necessitate substantial data and video transmission, requiring significant spectral resources. The unlicensed millimeter wave (mmWave) spectrum, especially in the 60 GHz frequency band, offers promising potential for UAV communications. However, WiGig users are the incumbent users of the 60 GHz unlicensed spectrum. Therefore, to ensure fair coexistence between UAV-based new radio-unlicensed (NR-U) users and WiGig users, unlicensed spectrum-sharing strategies need to be meticulously designed. Due to the beam directionality of the NR-U system, traditional listen-before-talk (LBT) spectrum sensing strategies are no longer effective in NR-U/WiGig systems. To address this, we propose a new cooperative unlicensed spectrum sensing strategy based on mmWave beamforming direction. In this strategy, UAV and WiGig users cooperatively sense the unlicensed spectrum and jointly decide on the access strategy. Our analysis shows that the proposed strategy effectively resolves the hidden and exposed node problems associated with traditional LBT strategies. Furthermore, we consider the sensitivity of mmWave to obstacles and analyze the effects of these obstacles on the spectrum-sharing sensing scheme. We examine the unlicensed spectrum access probability and network throughput under blockage scenarios. Simulation results indicate that although obstacles can attenuate the signal, they positively impact unlicensed spectrum sensing. The presence of obstacles can increase spectrum access probability by about 60% and improve system capacity by about 70%.

Design and characterization of a meandered V-shaped antenna using characteristics mode analysis and its MIMO configuration for future mmWave devices

This study presents a novel four-element MIMO antenna system designed for the millimeter-wave (mmWave) spectrum. Each MIMO antenna element features a meandered V-shaped radiating structure fed by a 50Ω microstrip line and a partial ground plane with a square notch printed on a 0.254-mm thick RO5880 substrate. The characteristic mode analysis (CMA) of the antenna is done, which reveals that the antenna efficiently utilizes Mode 2, while Modes 1 and 4 also contribute to the resonance, resulting in a wideband response within the mmWave spectrum. A four-element pattern diversity MIMO configuration is developed to evaluate its suitability for MIMO communication, incorporating a connected ground-structure decoupling network to enhance isolation. The MIMO system achieves over 20 dB isolation between elements, with an impedance bandwidth ranging from 20.2 to 33.05 GHz and a peak gain of 6.6 dBi at 28 GHz. Fabrication and measurement validate the design, showing strong agreement with simulations. The MIMO performance metrics, including envelope correlation coefficient (ECC), diversity gain (DG), mean effective gain (MEG), total active reflection coefficient (TARC), and channel capacity loss (CCL), are within acceptable limits, suggesting that the proposed MIMO antenna system is a promising candidate for future mmWave applications.

High-gain mmWave shorted rectangular ring antenna with complementary segmented-cavity backed structure

An efficient gain-enhancement technique for millimeter wave (mmWave) planar patch antennas (PPAs) using a novel slot-loaded and segmented-cavity backed structure is newly proposed in this study. By incorporating a main radiator with a rectangular slot and employing a muli-layered segemented-cavity, the proposed antenna design significantly increases antenna gain beyond conventional approaches. Unlike traditional patch antennas or those with shorting pin structures, our gain-enhanced PPA utilizes the rectangular slot to electrically expand the radiation aperture, while the addition of substrate integrated pillars acorss multiple segmented ground layers markedly improves antenna directivity. The strategric use of a segmented cavity not only facilitates flexible impedance matching but also ensures consistent performance within the n257 band, accompanied by minimal gain variation. To verify the gain enhancement from the conventional patch, the proposed antenna was fabricated with a size of 1.03 λ0 × 1.03 λ0 × 0.1 λ0 at 28 GHz. The measured 10-dB impedance bandwidth was 12.14 % with a maximum measured gain of the 11.28 dBi at 28 GHz. Compared to the measured gain of the conventional PPA with the same size, the gain was 39.6 % higher, which represents the highest gain per total antenna volume observed for a single PPA in the mmWave spectrum for high-gain applications, to the best of our knowledge.

Quad-Band 1 × 4 Linear MIMO Antenna for Millimeter-Wave, Wearable and Biomedical Telemetry Applications.

In this paper, we present the design of a millimeter-wave 1 × 4 linear MIMO array antenna that operates across multiple resonance frequency bands: 26.28-27.36 GHz, 27.94-28.62 GHz, 32.33-33.08 GHz, and 37.59-39.47 GHz, for mm-wave wearable biomedical telemetry application. The antenna is printed on a flexible substrate with dimensions of 11.0 × 44.0 mm2. Each MIMO antenna element features a modified slot-loaded triangular patch, incorporating 'cross'-shaped slots in the ground plane to improve impedance matching. The MIMO antenna demonstrates peak gains of 6.12, 8.06, 5.58, and 8.58 dBi at the four resonance frequencies, along with a total radiation efficiency exceeding 75%. The proposed antenna demonstrates excellent diversity metrics, with an ECC < 0.02, DG > 9.97 dB, and CCL below 0.31 bits/sec/Hz, indicating high performance for mm-wave applications. To verify its properties under flexible conditions, a bending analysis was conducted, showing stable S-parameter results with deformation radii of 40 mm (Rx) and 25 mm (Ry). SAR values for the MIMO antenna are calculated at 28.0/38.0 GHz. The average SAR values for 1 gm/10 gm of tissues at 28.0 GHz are found to be 0.0125/0.0079 W/Kg, whereas, at 38.0 GHz, average SAR values are 0.0189/0.0094 W/Kg, respectively. Additionally, to demonstrate the telemetry range of biomedical applications, a link budget analysis at both 28.0 GHz and 38.0 GHz frequencies indicated strong signal strength of 33.69 dB up to 70 m. The fabricated linear MIMO antenna effectively covers the mm-wave 5G spectrum and is suitable for wearable and biomedical applications due to its flexible characteristics.

A 28 GHz wideband planar stepped-shaped MIMO antenna with isolating metallic sheet for 5G millimeter wave communications

Presented work describes the symmetrical quad-element Multiple-Input Multiple-Output (MIMO) antenna operating at 28 GHz for Fifth generation (5G) millimeter-wave (mm-wave) spectrum. The core of this antenna system features a stepped-shaped patch radiator precisely tuned to 28 GHz, effectively broadening its resonance across the desired operational frequency band. To improve isolation, an Isolating Metallic Sheet (IMS) is precisely placed between the patch radiators of projected antenna. Rogers RT5880 substrate is used to fabricate with dimensions of 20.48 × 20.48 mm2, thickness of 1.6 mm, and dielectric constant of 2.2. Both simulationand measurement outcomesindicate that the antenna has a bandwidth of 7.13 GHz, covering frequencies ranging from 25.21 GHz to 32.34 GHz, for a fractional bandwidth of 24.78 %. Key antenna performance measurements include a peak amplitude of up to 53 dB and a significant port-to-port isolation of more than 20 dB. Ithasbeen carefully examined revealing a minimum channel capacity loss of 0.135 bits/s/Hz, a mean effectivegain of −3 dB, a diversity gain of around 10 dB, a total active reflection coefficient of −10 dB, and an envelope correlation coefficient of less than 0.005. Presentedantenna meets industrial requirementsfor high-speed mm-wave communications in 28 GHz 5G networks.

Absorption‐Dominant Electromagnetic Interference (EMI) Shielding across Multiple mmWave Bands Using Conductive Patterned Magnetic Composite and Double‐Walled Carbon Nanotube Film

AbstractThe revolution of millimeter‐wave (mmWave) technologies is prompting a need for absorption‐dominant EMI shielding materials. While conventional shielding materials struggle in the mmWave spectrum due to their reflective nature, this study introduces a novel EMI shielding film with ultralow reflection (&lt;0.05 dB or 1.5%), ultrahigh absorption (&gt;70 dB or 98.5%), and superior shielding (&gt;70 dB or 99.99999%) across triple mmWave frequency bands with a thickness of 400 µm. By integrating a magnetic composite layer (MCL), a conductive patterned grid (CPG), and a double‐walled carbon nanotube film (DWCNTF), specific resonant frequencies of electromagnetic waves are transmitted into the film with minimized reflection, and trapped and dissipated between the CPG and the DWCNTF. The design factors for resonant frequencies, such as the CPG geometry and the MCL refractive index, are systematically investigated based on electromagnetic wave propagation theories. This innovative approach presents a promising solution for effective mmWave EMI shielding materials, with implications for mobile communication, radar systems, and wireless gigabit communication.

Delay analysis of ring resonator-based beam-forming network in z-domain

During the next generation of wireless cellular networks, the millimeter-wave (mm-wave) spectrum will bring new opportunities for exceptionally high data transfer speeds and extensive network connectivity. Millimeter waves, on the other hand, are subject to a significant loss of propagation, which is the most significant impediment. A beneficial solution to this difficulty, which can be overcome, is to use a beam-forming system that consists of many antennas. The purpose of this study is to provide a concept for an integrated photonic beam-forming system that utilises multiple ring resonators for a 1 × 4 phase array antenna operating in the Ka-Band frequency range. The waveguide technology is the foundation for a signal that operates at 28 GHz. It is through the use of the optical ring resonator that the actual time delay line may accomplish its goal. The suggested method can be imDuring the next generation of wireless cellular networks, the millimeter-wave (mm-wave) spectrum will bring new opportunities for exceptionally high data transfer speeds and extensive network connectivity. Millimeter waves, on the other hand, are subject to a significant loss of propagation, which is the most significant impediment. A beneficial solution to this difficulty, which can be overcome, is to use a beam-forming system that consists of many antennas. The purpose of this study is to provide a concept for an integrated photonic beam-forming system that utilises multiple ring resonators for a 1 × 4 phase array antenna operating in the Ka-Band frequency range. The waveguide technology is the foundation for a signal that operates at 28 GHz. It is through the use of the optical ring resonator that the actual time delay line may accomplish its goal. The suggested method can be implemented as a variable true time delay (TTD) line to change the radiation angle of phase array antennas (PAA). The main lobe radiated by the PAA can be directed squint-free between the angles from −28° to +28°. The mathematical analysis and design of the beam producing the structure are presented. Following that, delays of 650 ps, 350 ps, and 250 ps could be produced with coupling coefficients of κ = 0.5 , κ = 0.7, and κ = 0.9 , respectively, and the associated phase shifts were 0.469π, 0.146π, and 0.387π.plemented as a variable true time delay (TTD) line to change the radiation angle of phase array antennas (PAA). The main lobe radiated by the PAA can be directed squint-free between the angles from −28° to +28°. The mathematical analysis and design of the beam producing the structure are presented. Following that, delays of 650 ps, 350 ps, and 250 ps could be produced with coupling coefficients of κ = 0.5 , κ = 0.7, and κ = 0.9 , respectively, and the associated phase shifts were 0.469π, 0.146π, and 0.387π.

Effect of the boson peak and the ionic resonance in the dielectric properties of silicate materials at mm-wave and THz frequencies

In this paper, a broadband measurement of the dielectric properties of silicates has been done to cover the seldom characterized mm-wave spectrum and the low THz spectrum. The dielectric properties, i.e. loss and permittivity, show a frequency independent response up to approximately 40 GHz and the loss monotonically increases to the THz frequency range. Two resonance peaks appear at THz frequencies: the first is the boson peak, and the second one corresponds to the ionic resonance of the network former, which in this case is silicon. Even though the materials belong to different groups in the silicate family (crystalline and non-crystalline, with different levels of purity), they seem to have the same overall tendency in the dielectric properties. Argand plots are used for the first time at THz frequencies to provide physical insight into the boson peak and ionic resonance. The complex plane analysis reveals details on the polarization mechanisms underlying silicate network vibrations through direct visualization of their characteristic signatures, and simplifies the process of modeling the dielectric response, leading to a better fit.

Automotive Grade WLCSP for Radar Applications

Wafer-Level Chip Scale Packages (WLCSPs) are becoming commonplace in the industry due to their small form factor. Applications include industrial and automotive which demand high reliability performance. Additionally, WLCSPs may be superior in some implementations to other package options for RF performance in the mmWave spectrum, which is desired for automotive radar application. In this study the industry’s first auto grade 1 capable large WLCSP package. (~ 72 mm2 body size, 18x15 BGA array, 0.5 mm pitch) will be presented. It will be demonstrated how extensive design enhancements, predictive simulations, careful package materials and process selection and assembly process optimization studies are required to develop a robust package solution. Multiple assembly process experiments and corner studies were conducted to demonstrate robustness of WLCSP package solution to meet automotive grade quality and reliability requirements. Both component/unit level and board level reliability was evaluated as per AECQ100 standards. Robustness margins were confirmed through reliability testing performed up to 2-3x reliability requirements.

Design and Implementation of a Specialised Millimetre-Wave Exposure System for Investigating the Radiation Effects of 5G and Future Technologies.

As the fifth-generation (5G) network is introduced in the millimetre-wave (mmWave) spectrum, and the widespread deployment of 5G standalone (SA) is approaching, it becomes essential to establish scientifically grounded exposure limits in the mmWave frequency band. To achieve this, conducting experiments at specific frequencies is crucial for obtaining reliable evidence of potential biological impacts. However, there is a literature gap where experimental research either does not utilise the mmWave high band (e.g., the 26 Gigahertz (GHz) band) or most studies mainly rely on computational approaches. Moreover, some experimental studies do not establish reproducible test environment and exposure systems. Addressing these gaps is vital for a comprehensive exploration of the biological implications associated with mmWave exposure. This study was designed to develop and implement a mmWave exposure system operating at 26 GHz. The step-by-step design and development of the system are explained. This specialised system was designed and implemented within an anechoic chamber to minimise external electromagnetic (EM) interference, creating a controlled and reproducible environment for experiments involving high-frequency EM fields. The exposure system features a 1 cm radiation spot size, enabling highly localised exposure for various biological studies. This configuration facilitates numerous dosimetry studies related to mmWave frequencies.

A Frequency Reconfigurable Graphene-Based Microstrip Antenna with Mushroom-Like EBG

The growing demand for wireless applications has led to network congestion issues. In response, network operators have recommended a transition to higher frequencies, particularly within the unlicensed millimeter-wave (mm-wave) spectrum. This shift aims to fulfill users' desires for rapid data transmission within personal networks, whether at home or in the office, exemplified by technologies like WiGig technology and indoor applications. However, a significant challenge in achieving high data transfer speeds within this frequency range lies in the design of the antenna. These antennas must strike a balance between size and performance. Microstrip Patch (MP) antennas have gained recognition for their compact form and seamless integration into mobile communication systems. Nonetheless, they grapple with limitations such as poor gain and narrow bandwidth, largely attributable to surface waves negatively impacting antenna performance. In this study, we introduce, design, and optimize an MP antenna tailored for 60 GHz applications. To enhance the performance of the MP antenna, we introduce various mushroom-like Electromagnetic Bandgap (EBG) structures. These structures address the propagation of the surface waves issue that affects the antenna performance. Additionally, to create a tunable frequency antenna the variable conductivity of the graphene material is used in the form of implanted slots on the patch and tuned by applied DC voltage on the slots. Finally, the parameters of the MP antenna undergo enhancement based on simulation results obtained through CST software.

A Compact Dual-Band Millimeter Wave Antenna for Smartwatch and IoT Applications with Link Budget Estimation.

Advancement in smartwatch sensors and connectivity features demands low latency communication with a wide bandwidth. ISM bands below 6 GHz are reaching a threshold. The millimeter-wave (mmWave) spectrum is the solution for future smartwatch applications. Therefore, a compact dual-band antenna operating at 25.5 and 38 GHz is presented here. The characteristics mode theory (CMT) aids the antenna design process by exciting Mode 1 and 2 as well as Mode 1-3 at their respective bands. In addition, the antenna structure generates two traverse modes, TM10 and TM02, at the lower and higher frequency bands. The antenna measured a bandwidth (BW) of 1.5 (25-26.5 GHz) and 2.5 GHz (37-39.5 GHz) with a maximum gain of 7.4 and 7.3 dBi, respectively. The antenna performance within the watch case (stainless steel) showed a stable |S11| with a gain improvement of 9.9 and 10.9 dBi and a specific absorption rate (SAR) of 0.063 and 0.0206 W/kg, respectively, at the lower and higher bands. The link budget analysis for various rotation angles of the watch indicated that, for a link margin of 20 dB, the antenna can transmit/receive 1 Gbps of data. However, significant fading was noticed at certain angles due to the shadowing effect caused by the watch case itself. Nonetheless, the antenna has a workable bandwidth, a high gain, and a low SAR, making it suitable for smartwatch and IoT applications.

System-Level Simulation Suite for the Design of mmWave-Over-Fiber-Based Distributed Antenna Systems

Although challenging propagation conditions reduce its reliability, the mmWave spectrum is considered a cornerstone of (beyond-)5G networks. Recently, distributed antenna systems (DASs) surrounding the mobile users with multiple remote antenna units (RAUs) interconnected by mmWave-over-fiber technology were identified as a prime candidate to unlock high throughput and reliable coverage. This article proposes a dedicated simulation suite facilitating the deployment of such a mmWave-over-fiber-based DAS by accurately predicting system-level performance and enabling time-efficient optimization of the hardware configuration, including the RAUs, the central office (CO), and the signal processing units, toward the target application. It incorporates accurate models for the mmWave-over-fiber link and the amplifiers, including nonlinear distortion and noise, full-wave electromagnetic models for the antenna front-ends, and analytical models for the wireless channel. The simulation suite is validated by a measurement campaign, not only focusing on a single mobile user served by a fixed-beam RAU but also considering a multibeam RAU serving two users simultaneously by means of two independent mmWave-over-fiber links. The model accurately predicts up-and downlink quality over a wide range of user positions, different system parameters, and also accurately captures inter-user interference.

Polarization-Insensitive and Oblique Incident Angle Stable Miniaturized Conformal FSS for 28/38 GHz mm-Wave Band 5G EMI Shielding Applications

This letter presents a miniaturized conformal dual-band mm-wave frequency selective surface (FSS) for fifth-generation (5G) electromagnetic interference (EMI) shielding applications. Two back-to-back resonators are separated with a 0.254 mm thin dielectric substrate. The proposed FSS exhibits two wide stopbands (S21<-10 dB) in the mm-wave 5G frequency spectrum. The stopband bandwidths (BW) are 42.8% at 28 GHz and 24.2% at 38 GHz. The periodicity of the unit cell is 0.26 λ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> , where λ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> is the wavelength of the lower stopband. The key features of the proposed FSS include a miniaturized unit cell structure for 28 GHz and 38 GHz frequency bands with a high oblique incident angle (OIA) stable filter behavior up to 60°. The proposed FSS also features polarization insensitivity and conformality. The simulated and measured results show good agreement for EMI shielding applications.

6-20 GHz 30% ScAlN Lateral Field-Excited Cross-Sectional Lamé Mode Resonators for Future Mobile RF Front Ends.

This article reports on 30% scandium-doped AlN (ScAlN) lateral field-excited (LFE) cross-sectional Lame' mode resonators (CLMRs) with unprecedented performance in the 6-20 GHz range. By combining high-crystallinity 30% ScAlN piezoelectric thin films, a lithographic tunability of the resonance frequency, and a simple three-mask post-CMOS compatible fabrication process, we propose a technology platform that can enable the mass production of low-loss, wideband, and compact microacoustic filtering devices spanning a wide spectrum portion on the same chip for the next-generation radio frequency front ends (RFFEs) of handsets. This article demonstrates a successful scaling of the microacoustic technology well beyond the sub-6-GHz fifth-generation (5G) band, as well as the outstanding capabilities of high-crystallinity 30% ScAlN piezoelectric layers in delivering high-quality factor ( Q ) and high-electromechanical coupling ( kt2 ) resonators, notably exceeding the state of the art in terms of relevant figures of merit (FOMs). Furthermore, we experimentally investigate the impact of geometrical parameters, such as tethering configuration and width-over-length ratio on the devices' 3-dB quality factor ( [Formula: see text]), power linearity (PL), and temperature coefficient of frequency (TCF). By adopting a statistical approach for data analysis, we determine the optimal geometry to maximize the Q value. Moreover, we experimentally demonstrate that a fully tethered device's configuration ensures superior PL, lower TCF, and higher device yield and select that as the best design tradeoff between all the variables under consideration. Finally, we discuss a further scaling of LFE CLMRs, both in terms of higher doping levels in the piezoelectric layer, in order to enhance the performance of microacoustic filters, and in terms of higher operation frequencies, in order to reach and cover the mm-wave spectrum.

Fair and Efficiency Coexistence Between NR-U and WiGig Networks Enabled by a Matching-Based Framework With Forbidden Pairs

Deploying the 5 G new radio network on the unlicensed mmWave band (NR-U) is a promising solution to meet the constantly increasing traffic demand of the cellular network. However, the coexistence issue on the unlicensed mmWave spectrum between NR-U and Wireless Gigabit (WiGig) networks becomes a significant concern. The coexistence schemes between LTE and Wi-Fi networks cannot be readily applied to support the coexistence between NR-U and WiGig networks due to the directional beamforming and propagation characteristic of the mmWave band. The directional transmission complicates the coexistence problem but opens up possibilities for increased system capacity via concurrent multi-user MIMO (MU-MIMO) transmission at the expense of interference management. To this end, we consider an NR-U and WiGig coexisting scenario and aim to maximize the total NR-U throughput on the unlicensed spectrum via resource allocation and inter-beam interference mitigation. The optimization problem is formulated into an integer nonlinear programming (INLP) problem and is further transformed into a many-to-one matching game for tractability. We propose a matching-based concurrent algorithm (MBCA) to solve it and the inter-beam interference is mitigated via the forbidden pairs (FPs). In comparison to the exhaustive search-based algorithm (ESA), simulation results show that FP effectively mitigates inter-beam interference and achieves near-optimal performance. The proposed algorithm also outperforms the state-of-art algorithms in existing research.

MmWave Polarization Diversity Wideband Multiple-Input/Multiple-Output Antenna System with Symmetrical Geometry for Future Compact Devices

The fifth generation (5G) of mobile networks is a significant technological advancement in telecommunications that provides faster data speeds, lower latency, and greater network capacity. One of the key technologies that enables 5G is multiple-input/multiple-output (MIMO) antenna systems, which allow for the transmission and reception of multiple data streams simultaneously, improving network performance and efficiency. MIMO is essential to meeting the demand for higher data rates and improved network performance in 5G networks. This work presents a four-element MIMO antenna system dedicated to the upper 5G millimeter-wave (mmWave) spectrum. The suggested antenna system is designed using an ultra-thin RO5880 substrate having total dimensions of 20 × 20 × 0.254 mm3 with symmetrical geometry. The proposed antenna covers a fractional bandwidth of 46.875% (25–38 GHz), covering potential 5G bands of 26, 28, and 32 GHz, and offers isolation of &gt;18 dB. The proposed MIMO system is fabricated and tested in-house. The antenna showed efficiency &gt;88% at the potential band of interest and a peak gain of 3.5 dBi. The orthogonal arrangement of the resonating elements provides polarization diversity. Also, the MIMO parameters obtained, such as mean effective gain (MEG), envelope correlation coefficient (ECC), diversity gain (DG), channel capacity loss (CCL), and total active reflection coefficient (TARC), are found to have good performance. The measured results obtained are found to be in good agreement with simulations, hence making the proposed MIMO antenna suitable for handheld mmWave 5G devices.

Design of a Novel Four-element Koch-Sierpinski fractal mmwave antenna for 5G applications

ABSTRACT The paper presents a novel fractal antenna in millimetre wavebands for 5 G applications involving the fusion of Koch and Sierpinski methods. A 4-element MIMO antenna is designed using the unique fractal structure. The proposed four-element MIMO antenna operates from 27.55 GHz to 28.6 GHz with resonant frequency at 28 GHz and the obtained mutual coupling between the MIMO elements is well below -25 dB. The performance of the antenna is characterised in MIMO environment by studying the important MIMO parameters like Envelope Correlation Coefficient (ECC), Channel Capacity Loss (CCL), Mean Effective Gain (MEG)and Total Active Reflection Coefficient (TARC). The proposed antenna is highly suitable for 5 G applications in the mmwave spectrum owing to its stable and directional radiation patterns on both the E and H planes. A prototype of the proposed model is fabricated and measured results are obtained with good matching to the simulated results.

A Framework to Address Mobility Management Challenges in Emerging Networks

The key enablers for emerging cellular networks such as densification, concurrent operation at multiple bands and harnessing mmWave spectrum give birth to a peculiar set of new network management challenges. One such key challenge is the user mobility management. In this article, we identify the key issues that render current mobility management paradigm inadequate for delivering the expected Quality of Experience (QoE) and resource efficiency in emerging and future cellular networks. Together, these challenges call for paradigm shift in the way mobility is managed in cellular networks. We present an Advanced Mobility Management and Utilization Framework (A-MMUF) that can enable this paradigm shift by transforming mobility management from being a reactive to a proactive process. The core idea of A-MMUF is to build upon Mobility Prediction Models (MPMs) to predict various attributes of user mobility and traffic patterns such as next candidate cell for handover (HO), time of HO, future cell loads. These predictions are then leveraged to not only improve HO process for better QoE and less signaling overhead, but also to enable proactive automation to further maximize network performance in terms of energy and spectrum efficiency. However, understandably, the gains offered by the A-MMUF hinge on the accuracy of the MPMs, which may vary, not only with the choice of underlying machine learning technique, but also with the volume, variety, and fidelity of the training data. We analyze the potential gains of A-MMUF through three case studies: namely proactive HO, proactive Mobility Load Balancing (P-MLB), and proactive Energy Savings (P-ES). In addition to demonstrating significant gains in all three case studies, the results provide useful insights into the agility vs accuracy tradeoff that can be leveraged for choosing optimal machine learning models for practical deployment of A-MMUF.