mmWave Wireless Systems Research Articles

LSTM-Aided Selective Beam Tracking in Multi-Cell Scenario for mmWave Wireless Systems

Millimeter wave systems rely on narrow beams (beamforming) and dense cell deployments for reliable communication. Tracking these beams from multiple cells can increase power consumption and signaling overhead. Therefore, a mobile needs to selectively and smartly track beams under power/overhead constraints. In this paper, we propose a fully data-driven, long short-term memory (LSTM)-based, selective link tracking approach. These approaches are developed for both fixed and adaptive power/overhead constraints, which also predict the magnitude of the best performing beam. The algorithms are validated in simulations of a 28GHz 5G New Radio (NR)-like system in an urban area with realistic navigation routes utilizing detailed ray-tracing. The simulations demonstrate that the proposed methods outperform classic and deep reinforcement learning (RL) approaches in terms of tracking accuracy, power saving and overhead for both analog and digital beamforming architectures. We also argue that the prediction of the proposed method can be easily performed on a digital signal processor of a modern chipset with minimal resource consumption.

Spanning the Spectrum: High-Performance Signal Source Design for the Millimeter-Wave Age

The millimeter-wave (mm-wave) frequency range is consumer wireless technology’s next frontier. Next-generation cellular technologies demand ever-increasing data rates, reduced latency, and robust service for a massive number of users. The mm-wave wireless systems operating in the frequency range from 10 to 100 GHz have the potential to satisfy the requirements presented by these consumer demands <xref ref-type="bibr" rid="ref1" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">[1]</xref> . High carrier frequencies offer increased communication bandwidths for improved throughput with relatively small fractional bandwidths. Furthermore, because the development of mm-wave wireless and cellular technologies is in its infancy, relatively few external interferers exist at these frequencies. Thanks to the continued scaling of CMOS devices and increased transit and maximum frequencies, the integration of high-performance mm-wave transceivers is more viable than ever before. Transceiver integration further benefits from the decreased size of passive devices with high-frequency operation, decreasing silicon area and minimizing parasitic effects. Thanks to these benefits, 5G hardware research has focused on exploring limitations and establishing design principles for integrated CMOS mm-wave front ends.

A mm-Wave Frequency Modulated Transmitter Array for Superior Resolution in Angular Localization Supporting Low-Latency Joint Communication and Sensing

Joint sensing-and-communication is envisioned to play a major role in emerging mm-Wave wireless systems to perform rapid tracking of wireless nodes for reliable wireless communication and ubiquitous distributed sensing. Phased arrays are essential to realize high array gains and enhance the communication distance. However, their pencil sharp beams require precise localization and tracking of wireless nodes to maintain beam alignment and reliable communication, especially in mobile wireless links. In parallel, array-based mm-Wave radars require large arrays for precise angular resolution that is fundamentally limited by the form factor and power consumption of the radar systems. We propose a frequency modulated array (FMA) transmitter (Tx) to convert locations/positions to timing information, which supports dual-modes for joint sensing-and-communication: rapid and precise full field-of-view (FoV) receiver (Rx) localization in the Tx/Rx localization mode for wireless communication and target angular detection in its radar mode. Exploiting its unique joint space-time-frequency dependent signals, the FMA distinguishes spatial signatures far below its array 3-dB beamwidth, i.e., achieving super-resolution and can simultaneously localize multiple Rx nodes or detect multiple targets in “one-shot.” Moreover, FMA only adds minimal circuit/computation overhead on traditional multi-in multi-out (MIMO) arrays. A proof-of-concept 28-GHz four-element multi-mode FMA Tx array is implemented in a 45 nm CMOS silicon on insulator (SOI) process. Over-the-air (OTA) measurements with Rx nodes in the communication-mode or reflectors in radar-mode demonstrate the four-element FMA Tx array operations and achieve a full-FoV coverage with <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$&lt;$</tex-math> </inline-formula> 2 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$^{\circ}$</tex-math> </inline-formula> –4 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$^{\circ}$</tex-math> </inline-formula> accuracy in angular localization with a 10 ns timing resolution (i.e., 100 MHz digital clock in Rx). Sensing aided communication is demonstrated to create sharp and secure constellation decomposition array (CDA) 64 quadratic-amplitude modulation (QAM) beams toward target Rx at low rms error vector magnitude (EVM) of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$&lt;$</tex-math> </inline-formula> 5.33% using the sensed data from FMA based Rx localization scheme.

Guest Editorial 2022 Radio Frequency Integrated Circuits Symposium

This Special Issue of the IEEE Journal of Solid-State Circuits features expanded versions of selected articles presented at the 2022 Radio Frequency Integrated Circuits Symposium (RFIC) that was held in Denver, CO, USA, during June 19–21, 2022. The invited papers introduce innovative concepts at the circuit or architecture levels and cover low-power RF to high-data-rate mm-wave wireless systems.

Amplitude Modeling of Specular Multipath Components for Robust Indoor Localization.

Ultra-Wide Bandwidth (UWB) and mm-wave radio systems can resolve specular multipath components (SMCs) from estimated channel impulse response measurements. A geometric model can describe the delays, angles-of-arrival, and angles-of-departure of these SMCs, allowing for a prediction of these channel features. For the modeling of the amplitudes of the SMCs, a data-driven approach has been proposed recently, using Gaussian Process Regression (GPR) to map and predict the SMC amplitudes. In this paper, the applicability of the proposed multipath-resolved, GPR-based channel model is analyzed by studying features of the propagation channel from a set of channel measurements. The features analyzed include the energy capture of the modeled SMCs, the number of resolvable SMCs, and the ranging information that could be extracted from the SMCs. The second contribution of the paper concerns the potential applicability of the channel model for a multipath-resolved, single-anchor positioning system. The predicted channel knowledge is used to evaluate the measurement likelihood function at candidate positions throughout the environment. It is shown that the environmental awareness created by the multipath-resolved, GPR-based channel model yields higher robustness against position estimation outliers.

A Wide-Band High-Efficiency Hybrid-Feed Antenna Array for mm-Wave Wireless Systems

A wide-band and high-efficiency planar antenna array with a novel hybrid-feed structure is proposed in this article. By combing the coaxial-line feed magneto-electric (ME) dipoles with the aperture coupled dielectric cavity, a hybrid-feed 2 × 2-unit ME-dipole sub-array is invented. The low-loss ridge gap waveguide (RGWG) corporate-feed network is used to replace the high-loss substrate-based feed networks and high-cost RWG feed networks. New forms of RGWG H-plane divider are designed to build the RGWG feed network. An 8 × 8-unit ME-dipole antenna array is designed and fabricated to verify the validity of the array. The radiation part consists of two layers of a low-cost printed circuit board (PCB), and the feeding part consists of two copper plates manufactured by computer numerical control (CNC) milling. Measured results show that a relative bandwidth of 16.4% with |S11| &lt; −10 dB is achieved, with a maximum radiation efficiency of 85%. The stable symmetric radiation patterns are observed in both the E-plane and H-plane, covering the operation band. Based on the measured results, a 16 × 16-unit ME-dipole antenna array is simulated. Results indicate that the proposed array has wide-band and high-efficiency features, which is suitable for large-scale array design in mm-wave wireless systems.

Accurate and broadband manipulations of harmonic amplitudes and phases to reach 256 QAM millimeter-wave wireless communications by time-domain digital coding metasurface

We propose a theoretical mechanism and new coding strategy to realize extremely accurate manipulations of nonlinear electromagnetic harmonics in ultrawide frequency band based on a time-domain digital coding metasurface (TDCM). Using the proposed mechanism and coding strategy, we design and fabricate a millimeter-wave (mmWave) TDCM, which is composed of reprogrammable meta-atoms embedded with positive-intrinsic-negative diodes. By controlling the duty ratios and time delays of the digital coding sequences loaded on a TDCM, experimental results show that both amplitudes and phases of different harmonics can be engineered at will simultaneously and precisely in broad frequency band from 22 to 33 GHz, even when the coding states are imperfect, which is in good agreement with theoretical calculations. Based on the fabricated high-performance TDCM, we further propose and experimentally realize a large-capacity mmWave wireless communication system, where 256 quadrature amplitude modulation, along with other schemes, is demonstrated. The new wireless communication system has a much simpler architecture than the currently used mmWave wireless systems, and hence can significantly reduce the hardware cost. We believe that the proposed method and system architecture can find vast application in future mmWave and terahertz-wave wireless communication and radar systems.

Millimeter-Wave Dual-Band Bandpass Filter With Large Bandwidth Ratio Using GaAs-Based Integrated Passive Device Technology

In this letter, a millimeter-wave (mm-wave) dual-band bandpass filter is proposed with large bandwidth ratio by using gallium arsenide (GaAs)-based integrated passive device (IPD) technology. To realize small chip size, one dual-mode on-chip resonator is designed by using quasi-lumped capacitors and microstrip lines. In addition, multiple transmission zeroes are generated by further introducing both the electric and magnetic couplings between adjacent resonators. To realize large bandwidth ratio of two passbands, the external quality factors are investigated at both passband, and can be independently controlled. For demonstration, a 28-/50-GHz dual-band bandpass filter is designed, fabricated, and measured. The fractional bandwidth ratio is 7.8, which is much larger than the reported on-chip filters. Meanwhile, very low insertion loss of 0.58-dB is realized for the lower passband at 28 GHz, indicating the proposed dual-band bandpass filter a promising application in mm-wave wireless systems.

A Cascaded Multi-IRSs Beamforming Scheme in mmWave Communication Systems

In this paper, we design a cascaded multiple intelligent reflecting surfaces (IRSs) assisted system to improve the user equipment (UE) received signal-to-noise-ratio (SNR) for mmWave wireless systems in dense blocked areas where a single IRS cannot establish visual path between the base station (BS) and UE. In our designed system, we aim to maximize the UE received SNR by optimizing the phase shifts (PSs) at cascaded IRSs and precoding vector at the BS and formulate an optimization problem. However, it is non-convex and difficult to solve. By employing the characteristics of the mmWave wireless channel, we divide the formulated problem into multiple sub-problems. After solving all the sub-problems, we obtain a near-optimal analytical solution with low computational complexity. However, in practical system, due to the hardware limitations, the PSs cannot to be infinite precision values. Therefore, we provide a n-bit discrete PS (DPS) scheme for practical deployment. The simulation results show that comparing with existing scheme, our proposed scheme has a better performance.

An Energy-Efficient 10-Gb/s CMOS Millimeter-Wave Transceiver With Direct-Modulation Digital Transmitter and I/Q Phase-Coupled Frequency Synthesizer

A fully integrated energy-efficient 10-Gb/s millimeter-wave transceiver with direct-modulation digital transmitter (TX) and I/ Q phase-coupled frequency synthesizer in 65 nm CMOS is presented. The transceiver consists of a direct-conversion receiver (RX), a digital TX with on-chip QPSK modulation, and a quadrature local-oscillation (LO) generation network with a 20-GHz phase-locked loop (PLL) frequency synthesizer. A T/R switch is integrated to interface with an E-shaped patch antenna. The QPSK modulation is directly realized in the I/ Q digital power amplifier (DPA), which simplifies the TX complexity and reduces the power consumption. A 20-GHz sub-sampling PLL (SSPLL) and a quadrature phased-coupled injection-locked oscillator (QILO) are integrated on-chip to generate 60-GHz quadrature LO signals. The QILO utilizes in-phase coupling technique to improve the LO I/ Q matching and phase noise performance. The RX achieves 7.1-dB noise figure (NF) and 25- to 47-dB dynamic gain range. The LO phase noise measured at the TX output is -115.6 dBc/Hz at 10 MHz offset from 60 GHz carrier. The measured error vector magnitude (EVM) of the TX is -23.9 dB for 10-Gb/s QPSK signals at 7-dBm output power. The EVM of the over-the-air (OTA) modulation-demodulation system is -13.8 dB for 10-Gb/s QPSK signals. The transceiver achieves the 10-Gb/s data rate while consuming 340.4 mW. The energy efficiency is 34 pJ/bit. This work demonstrates the fully functional wireless link based on the proposed mm-wave transceiver, which highlights the possibility of energy-efficient solution for future high throughputs mm-wave wireless systems.

Single RF-Chain Beam Training for MU-MIMO Energy Efficiency and Information-Centric IoT Millimeter Wave Communications

In a multi-user multiple-input multiple-output (MU-MIMO) communication system, multiple RF (radio frequency) chains are generally connected corresponding to the antenna elements. However, the system complexity, hardware cost, and energy consumption are challenging while using many RF chains. In addition, an information-centric Internet of Things (IoT) will be significant to guarantee fast service demand for radio access in the fifth generation (5G) mmWave wireless systems. In this paper, a new beam training method based on a single RF chain is proposed to overcome these challenges by using the downlink–uplink and downlink–downlink beam training techniques to establish the elite users’ subset group which can be trained in a single training time slot. Additionally, the users’ subset mechanism is implemented by selecting an arbitrary function to guarantee the convergence. Moreover, the proposed techniques are compared with the conventional full search method regarding searching time, cost, and complexity. Different user subset functions are modeled, evaluated, and compared with the existing ones with respect to effective channel gain and average system capacity. The simulation results show that the proposed method can achieve a significant system performance, and the single RF chain is serviceable for a large number of users when connected with a maximum of 64 antenna elements at the BS. The proposed method can also be implemented in a massive MU-MIMO system by using multiple RF chains in which each RF chain is connected to a group of 64 antenna elements. This work is applicable in 5G mmWave communications, which require robust infrastructure to meet the future IoT service demand in 5G hot scenarios.

Hardware-Efficient Hybrid Precoding for Millimeter Wave Systems With Multi-Feed Reflectarrays

Current hybrid precoding schemes for large-scale antenna array-aided millimeter wave (mmWave) wireless systems adopt either full-connected or sub-connected architectures based on phased array antennas (PAAs). The former achieves excellent precoding performance but imposes considerably high hardware complexity, while the latter is relatively simple but suffers from high performance loss. In this paper, we exploit the new technology of reflectarray antennas, which among other advantages offers significant hardware efficiency gain, and propose a novel hybrid precoding architecture based on multi-feed reflectarray antennas (MRAs) for mmWave wireless systems, which is capable of achieving considerable hardware efficiency gain even over the low-hardware-complexity sub-connected architecture with PAAs. The mathematical model is provided for this novel hybrid precoding architecture, and an efficient alternating descent algorithm is developed to jointly design the analog and digital precoders for the proposed hybrid precoding scheme. Numerical results obtained demonstrate that our proposed precoding scheme with MRAs achieves much better precoding performance than its sub-connected counterpart with PAAs.

Millimeter-Wave MultiBeam Aperture-Coupled Magnetoelectric Dipole Array With Planar Substrate Integrated Beamforming Network for 5G Applications

A modified topology of the 2-D multibeam antenna array fed by a passive beamforming network (BFN) is proposed by introducing two sets of vertical interconnections into the conventional array configuration. Different from the traditional design, the new array structure can be integrated into multilayered planar substrates conveniently, which has advantages of low loss characteristics, ease of realization, and low fabrication cost for millimeter-wave (mmWave) applications. A $4\times4$ multibeam antenna array that can generate 16 beams is then designed, fabricated, and measured in order to demonstrate the correctness of the proposed topology. As the crucial components of the design, two kinds of aperture-coupled magnetoelectric dipole antenna elements with multilayered feed structures and three types of vertical interconnections consisting of the vertical substrate integrated waveguides are investigated, respectively. Wide bandwidth of 16.4%, stable radiation beams, and gain up to 14.7 dBi are achieved by the fabricated prototype. The proposed array configuration provides a new mean to implement the relatively large size 2-D multibeam antenna arrays with planar passive BFNs, which would be attractive for future mmWave wireless systems used for 5G communications and other applications.

Attenuation by a Human Body and Trees as well as Material Penetration Loss in 26 and 39 GHz Millimeter Wave Bands

This paper investigates the attenuation by a human body and trees as well as material penetration loss at 26 and 39 GHz by measurements and theoretical modeling work. The measurements were carried out at a large restaurant and a university campus by using a time domain channel sounder. Meanwhile, the knife-edge (KE) model and one-cylinder and two-cylinder models based on uniform theory of diffraction (UTD) are applied to model the shape of a human body and predict its attenuation in theory. The ITU (International Telecommunication Union) and its modified models are used to predict the attenuation by trees. The results show that the upper bound of the KE model is better to predict the attenuation by a human body compared with UTD one-cylinder and two-cylinder models at both 26 and 39 GHz. ITU model overestimates the attenuation by willow trees, and a modified attenuation model by trees is proposed based on our measurements at 26 GHz. Penetration loss for materials such as wood and glass with different types and thicknesses is measured as well. The measurement and modeling results in this paper are significant and necessary for simulation and planning of fifth-generation (5G) mm-wave radio systems in ITU recommended frequency bands at 26 and 39 GHz.

An Overview of Signal Processing Techniques for Millimeter Wave MIMO Systems

Communication at millimeter wave (mmWave) frequencies is defining a new era of wireless communication. The mmWave band offers higher bandwidth communication channels versus those presently used in commercial wireless systems. The applications of mmWave are immense: wireless local and personal area networks in the unlicensed band, 5G cellular systems, not to mention vehicular area networks, ad hoc networks, and wearables. Signal processing is critical for enabling the next generation of mmWave communication. Due to the use of large antenna arrays at the transmitter and receiver, combined with radio frequency and mixed signal power constraints, new multiple-input multiple-output (MIMO) communication signal processing techniques are needed. Because of the wide bandwidths, low complexity transceiver algorithms become important. There are opportunities to exploit techniques like compressed sensing for channel estimation and beamforming. This article provides an overview of signal processing challenges in mmWave wireless systems, with an emphasis on those faced by using MIMO communication at higher carrier frequencies.

A survey of single and multi-hop link schedulers for mmWave wireless systems

Wireless communication at 60GHz, aka mmWave, provides extremely high data rates, i.e., several Gb/s. Moreover, devices have a much shorter transmission range as compared to those operating in the 2.4 and 5GHz bands. Indeed, links can be treated as pseudo-wires with minimal interference leakage. As a result, future 60GHz systems will have very high spatial reuse. This, however, is at the expense of high propagation loss, which can be overcome using directional or smart antennas. Another promising solution is to employ relays to boost the signal of weak links. In particular, if relays are properly selected, they are able to offer higher data rates than direct links, and also help circumvent obstacles. To this end, we review state-of-the-art schedulers that take advantage of the high spatial re-use afforded by 60GHz wireless systems to activate multiple links within a channel time allocation. Moreover, we survey works that use passive and active relays to overcome obstacles and to facilitate novel applications. We also survey those that maximize both spatial reuse and throughput of both direct and indirect (relay) links simultaneously.

Millimeter-wave communications for 5G – Part 2: applications [Guest Editorial

In the September 2014 issue of IEEE Communications Magazine, the first part of this Feature Topic included five articles that covered the fundamentals of mmWave communications with topics ranging from propagation to coverage, presenting a holistic view of research challenges and opportunities in the emerging area of mmWave radio systems and 5G mobile broadband. The use of this technology is expected to surge in the next few years and to transform the Internet industry in the next 10 years. This part of the Feature Topic will address in more detail many technical and application issues related to beamforming, device-to-device communications, heterogeneous networks, and multimedia transmission.

High speed optical mixer for distribution of 16QAMor QPSK data signals over 38 GHz

The authors demonstrate that an optoelectronic millimetre-wave (mm-wave) laser mixer operating at 38 GHz is capable of managing different modulation formats at different rates with the same identical operating conditions. This mixer is a relatively simple and compact optical source which integrates a wideband distributed transimpedance amplifier with a fast MQW VUG DFB laser. The mixer is fed with an electrical power of only 3 dBm at 7.6 or 9.5 GHz to provide the 38 GHz carrier. The device is capable of handling generated harmonics with either 16 QAM at 5 Mbit/s, QPSK at 60 Mbit/s or NRZ at 622 Mbit/s signals over 15 km fibre fed mm-wave radio systems without optical amplification.