mmW Systems Research Articles

Millimeter-Wave Image Deblurring via Cycle-Consistent Adversarial Network

Millimeter-wave (MMW) imaging has a tangible prospect in concealed weapon detection for security checks. Typically, a one-dimensional (1D) linear antenna array with mechanical scanning along a perpendicular direction is employed for MMW imaging. To achieve high-resolution imaging, the target under test needs to keep steady enough during the mechanical scanning process since slight movement can induce large phase variation for MMW systems, which will result in a blurred image. However, in the scenario of imaging of a human body, sometimes it is difficult to meet this requirement, especially for the elderly. Such blurred MMW images would reduce the detection accuracy of the concealed weapons. In this paper, we propose a deblurring method based on cycle-consistent adversarial network (Cycle GAN). Specifically, the Cycle GAN can learn the mapping between the blurred MMW images and the focused ones. To minimize the effect of the shaking blur, we introduce an identity loss. Moreover, a mean squared error loss (MSE loss) is utilized to stabilize the training, so as to obtain more refined deblurred results. The experimental results demonstrate that the proposed method can efficiently suppress the blurring effect in the MMW image.

Capacity Performance Analysis of 73 GHz Frequency Band for 5G Technology

Small cells, millimeter waves (mmW), and massive multiple-input multiple-output (MIMO) deployments have emerged as key technologies for mobile systems in the fifth generation (5G). However, a very few studies have been done on combining these three technologies into the cellular systems. In this paper, the authors provide an in-depth capacity analysis for the integrated small cells of mmW systems. Small cells are deployed for enhancing the capacity. It turns out that mmW signals are responsive to blockages, leading the line of sight (LOS) and non-line of sight (NLOS) conditions to have very different path loss rules. They divide power research into low signal-to-noise (SNR) and high SNR regimes based on signal-to-interference plus noise ratio. In the noise-dominated (low-SNR regime), the capacity analysis is derived by the simplest assumptions of the Shannon-Hartley theorem. The results of this study show that under NLOS and LOS scenarios, mmW frequency and distance between the user equipment and base station decrease logarithmically for system capacity.

Integrated Antennas on MnM Interposer for the 60 GHz Band

In this article, antennas for the 60 GHz ISM band designed to be integrated to a new high-frequency, low-cost interposer technology called Membrane-nanowire-Membrane (MnM) are discussed, manufactured, and measured. Also, an antenna characterization system under development at the Microelectronic Laboratory (LME-USP) is introduced, showing promising results for the deployment of mmW systems.

Review on Substrate Integrated Waveguide Cavity Backed Slot Antennas

Substrate Integrated Waveguide Cavity Backed Slot Antennas (SIW CBSA) are emerging candidates for planar Integrated Circuit (IC) technology in Millimetre-wave (MMW) bands. This peculiar antenna holds the advantage of conventional metallic cavity-backed antennas, with high gain, high front-to-back ratio, and low cross-polarization level. SIW CBSA structures are the best option for planar integration with a low profile, and low fabrication cost in the design of MMW systems. This paper discusses various forms of SIW CBSA structures, their operating mechanism, and methods of improving their performance in terms of gain, bandwidth, size reduction, beamforming capability, and multiple bands of operation. From this discussion, we can select the antenna with the required characteristics in terms of gain, dual-band, and dual-polarization suited for present and future-generation applications.

Networking and Positioning Co-Design in Multi-Connectivity Industrial mmW Systems

Highly directional millimeter-wave (mmW) connectivity – especially in industry-grade scenarios with complex and unpredictable device mobility – requires a certain degree of structural redundancy in the network, which can be provided by utilizing multi-connectivity mechanisms. To lower the coordination complexity and overhead of tracking multiple directional beams, mmW networks can retrieve and leverage timely positioning information. In this paper, we develop a holistic framework for the co-design of networking and positioning in industrial 5G mmW deployments with multi-connectivity capabilities. In particular, we propose a flexible two-stage positioning solution – mindful of information uncertainty – that relies upon the 5G NR system design and can be seamlessly integrated into the mmW cellular infrastructure with reasonable overheads. We reproduce a typical 5G mmW network deployment featuring dissimilar device mobility patterns and assess the performance of the proposed architecture. In particular, we evaluate the precision of our positioning and base station orientation estimation methods as well as analyze the impact of the proposed scheme on the system-level performance. Our numerical results demonstrate that the proposed solution yields highly accurate position estimates and significantly improves the average network spectral efficiency.

A Millimeter-Wave Fully Metallic Six-Channel Crossover Based on Maxwell Fish-Eye Lens

A millimeter-wave (mmW) fully metallic crossover with six intersecting channels based on Maxwell fish-eye (MFE) lens is proposed. The quasi-MFE lens consists of an almost-parallel plate waveguide with a curved top plate and an array of uniform metallic posts loaded on the bottom plate. Six pairs of rectangular waveguides are added that surround the lens to form a six-channel crossover. The results show a performance of broadband and efficient crossing transmissions, indicating the application potential of the proposed crossover in the multichannel mmW systems.

Joint transmit antenna selection and precoding for millimeter wave massive MIMO systems

Millimeter wave (mmW) communication coupled with massive MIMO architecture is attaining considerable attention to overcome the huge data rate requirements. Increasing the dimensions of a massive MIMO architecture provides spatial multiplexing gains, but at the cost of decrease in hardware efficiency. To optimize the energy efficiency of massive MIMO systems, in this paper, focusing on a sub-connected hybrid architecture, we propose a joint transmit antenna selection and precoding technique. Low Complexity heuristic algorithms are used to perform the antenna selection in order to limit the number of active antennas, hence, decreasing the power consumption which subsequently increases the energy efficiency. Precoding for the selected transmit antennas is performed using successive interference cancellation (SIC) based scheme. Simulation results show that the heuristic algorithms based transmit antenna selection scheme requires less computations and its performance is close to exhaustive search algorithm. Furthermore, SIC based precoding enables to overcome serious signal attenuation of mmW systems and performs best in terms of spectral efficiency for a partially connected hybrid structure. The joint solution is optimal in-terms of computational complexity and energy efficiency, which optimizes the performance of mmW massive MIMO systems.

Efficient Beam Sweeping Algorithms and Initial Access Protocols for Millimeter-Wave Networks

5G millimeter-wave (mmW) systems rely on electronically steerable antenna arrays to support directional communications. Directionality complicates the initial access (IA) process, whereby a base station (BS) announces itself to nearby user equipments (UEs), giving them the opportunity to associate with this BS. Existing approaches for IA suffer from long discovery time and/or nonnegligable probability of missing UEs. In this paper, we propose FastLink, an efficient IA protocol for mmW systems, in which discovery beacons are transmitted/received using the narrowest possible beams, allowing for high beamforming gains and low misdetection rate, while maintaining low discovery time. Fastlink executes a unique algorithm, called 3-dimensional peak finding (3DPF), to find the best beam in logarithmic time. We formulate the beam-finding process as a sparse problem and use compressive sensing to determine the minimum number of measurements needed for this process. We first study FastLink for the discovery of a single UE and then extend our analysis to a multi-user scenario. Both simulations and over-the-air experiments based on a custom mmW testbed are used to evaluate FastLink. Our results verify its efficiency, and show that it can reduce the search time by 90% compared to the scanning approach used in 802.11ad systems.

System EVM Characterization and Coverage Area Estimation of 5G Directive mmW Links

RF performance of fifth-generation (5G) new radio (NR) millimeter-wave (mmW) system will be characterized over-the-air (OTA) in 3GPP 5G NR performance and type approval testing. Total system error vector magnitude (EVM) performance has not been standardized in 3GPP since mobile and base stations are certified separately. In this article, we extend the OTA measured system EVM concept to cover EVM performance testing with beam steering for 5G mmW radio link. We show that the OTA measured system EVM inside of an electromagnetic compatibility (EMC) chamber can be directly converted to an expected link range, and this has been verified with outdoor measurements. The EVM measurements are performed for a set of beamforming directions to form an expected coverage area. The OTA measured system EVM results confirm that the 5G mmW proof-of-concept (PoC) radio supports 5G NR 16-QAM and 64-QAM modulations as well as 256-QAM modulation, which is currently specified for sub-6 GHz, only. The maximum estimated range of the 5G PoC mmW link is 840 m with 16-QAM modulation and 150 m with 256-QAM modulation. The estimated cell coverage with ±15° beam steering varies from 205 000 to 6500 m2 using 16-QAM and 256-QAM modulations, respectively. Usable beamwidth (BW) of the transceiver array is dependent on the system EVM requirement. It varies based on modulation, coding, and link distance. This phenomenon is called cell breathing, which is similar to any cellular system with adaptive coding techniques, although BW might be much narrower in 5G mmW systems.

Channel capacity model in urban areas at 20–70 GHz for 5G systems

ABSTRACTIn this paper, a millimeter-wave (mm-W)–multiple-input multiple-output (MIMO) channel model is introduced for the fifth-generation (5G) of microcellular communication systems. This deterministic channel model is based on reflection phenomena, which is a dominated propagation mechanism at mm-W communication systems. The model analyzes the channel capacity (CP) based on some important factors including frequency, absorption atmosphere, polarization, materials of surfaces and distance between the transmitter and the receiver. Four urban scenarios are considered in the analyses which are based on real urban constructions. Finally, Measurement data that have been conducted on the other work validate the theoretical analysis and demonstrate that the proposed model can be used to predict CP in urban areas for 5G systems.

Monolithic InAs/InP quantum dash dual-wavelength DFB laser with ultra-low noise common cavity modes for millimeter-wave applications.

We have developed and experimentally demonstrated a novel monolithic InAs/InP quantum-dash dual-wavelength distributed feedback (QD DW-DFB) C-band laser as a compact optical beat source to generate millimeter-wave (MMW) signals. The device uses a common gain medium in a single cavity structure for simultaneous correlated and stable dual-mode lasing in the 1550-nm wavelength range. A record narrow optical linewidth down to 15.83 kHz and average relative intensity noise (RIN) as low as -158.3 dB/Hz from 10 MHz to 20 GHz are experimentally demonstrated for the two optical modes generated by the laser. As a result, the beat note between these two lasing modes generates spectrally pure MMW signals between 46 GHz and 48 GHz. Such an efficient, coherent, and compact optical source is extremely attractive for applications in MMW systems, such as Radar and fiber-wireless integrated fronthaul for 5G and beyond.

Hybrid Precoding Design Using MMSE Baseband Precoder for mm-Wave Multi-User MIMO Systems

For future 5G wireless communication networks, millimeter-wave (mmWave) cellular systems is considered to be the key enabling technology because of its high data rates, low latency, high system capacity, and huge available bandwidths. However, multiuser networks in mmWave frequency bands encounter high path loss and interference, thus degrading the performance. Applying large antenna arrays at the base stations (BS) in order to achieve high beamforming gains with the help of precoding techniques is an efficient way of improving the performance of the system. Although multi-user beamforming can improve spectral efficiencies, full digital beamforming strategies used in the conventional microwave systems increase the hardware cost and consumes high power for large number of antennas in mmW systems. In this paper, a low-complexity multi-user hybrid precoding structure is proposed for mmWave multiple input multiple output (MIMO) channels utilizing Minimum Mean Square Error (MMSE) precoders at the BS with perfect channel knowledge. Simulations show that the achievable rate obtained by the proposed hybrid precoding scheme is very close to the single-user rate and also performs better compared to other hybrid precoding approaches.

Statistical Blockage Modeling and Robustness of Beamforming in Millimeter-Wave Systems

There has been a growing interest in the commercialization of millimeter wave (mmW) technology as a part of the Fifth-Generation New Radio (5G-NR) wireless standardization efforts. In this direction, many sets of independent measurement campaigns show that wireless propagation at mmW carrier frequencies is only marginally worse than propagation at sub-6 GHz carrier frequencies for small-cell coverage --- one of the most important use-cases for 5G-NR. On the other hand, the biggest determinants of viability of mmW systems in practice are penetration and blockage of mmW signals through different materials in the scattering environment. With this background, the focus of this paper is on understanding the impact of blockage of mmW signals and reduced spatial coverage due to penetration through the human hand, body, vehicles, etc. Leveraging measurements with a 28 GHz mmW experimental prototype and electromagnetic simulation studies, we first propose statistical blockage models to capture the impact of the hand, human body and vehicles. We then study the time-scales at which mmW signals are disrupted by blockage (hand and human body). Our results show that these events can be attributed to physical movements and the time-scales corresponding to blockage are hence on the order of a few 100 ms or more. Building on this fundamental understanding, we finally consider the broader question of robustness of mmW beamforming to handle blockage. Network densification, subarray switching in a user equipment (UE) designed with multiple subarrays, fall back mechanisms such as codebook enhancements and switching to legacy carriers in non-standalone deployments, etc. can address blockage before it leads to a deleterious impact on the mmW link margin.

Electrical models of through silicon Vias and silicon‐based devices for millimeter‐wave application

As the short vertical interconnections can significantly shorten the interconnect length between different circuits, three-dimensional integrated circuits (3D ICs) based on the through-silicon via (TSV) technology are considered as one of the most promising alternatives to overcome the scaling limits of Moore's low. Moreover, as the silicon technologies have been progressively expanded into the millimeter-wave (mmW) realm, the TSV technology also provides a promising option to realize a compact system with high performance and operating frequencies. This article provides an overview of recent advances in the development of TSV technologies and silicon-based passive devices for mmW applications. As various kinds of TSV losses are detrimental to the electrical performance of 3D ICs, especially in mmW systems, TSVs exploiting novel structures and materials still needs much more research, making it possible to integrate the passive device on 3D ICs and providing a promising option to realize a compact mmW system with excellent electrical performance and system reliability.

An improved method for TOA analysis in MMW systems

The energy detector (ED) receiver is a promising solution for time-of-arrival (TOA) based positioning using millimeter-wave (MMW) pulses in multipath environments due to its simple circuitry. Usually in ED receiver, the optimum threshold values required for TOA estimates cannot be acquired particularly when the signal-to-noise ratio (SNR) is low. In this paper, a new ED receiver is discussed based on the results of the ensemble empirical mode decomposition (EEMD) of the received MMW pulses. Meanwhile, the extreme learning machine (ELM) is used to determine optimum threshold values via analyzing the characteristics of the calculated energy samples. The discussed technique can provide efficient threshold values with lower complexity and lower sampling frequency. The proposed receiver is evaluated using measurements obtained in IEEE 802.15.3c models, which show its effectiveness compared to the conventional ED receivers.

Millimeter Wave Channel Measurements and Implications for PHY Layer Design

There has been an increasing interest in the millimeter wave (mmW) frequency regime in the design of next-generation wireless systems. The focus of this work is on understanding mmW channel properties that have an important bearing on the feasibility of mmW systems in practice and have a significant impact on physical (PHY) layer design. In this direction, simultaneous channel sounding measurements at 2.9, 29 and 61 GHz are performed at a number of transmit-receive location pairs in indoor office, shopping mall and outdoor environments. Based on these measurements, this paper first studies large-scale properties such as path loss and delay spread across different carrier frequencies in these scenarios. Towards the goal of understanding the feasibility of outdoor-to-indoor coverage, material measurements corresponding to mmW reflection and penetration are studied and significant notches in signal reception spread over a few GHz are reported. Finally, implications of these measurements on system design are discussed and multiple solutions are proposed to overcome these impairments.

Pea-Sized mmW Transceivers: QFN-?Based Packaging Concepts for Millimeter-Wave Transceivers

Enormous technological progress accomplished over the last several decades has facilitated the use of millimeter-wave (mmW) frequencies for mass-produced products such as automotive radars, industrial sensors, highspeed data communication links, and medical devices. The main enablers are new semiconductor technologies, with constantly improving cut-off frequencies reaching several hundred gigahertz. However, the dominant limiting factor for the mass production of low-cost mmW systems above 100 GHz is that suitable packaging technologies are not yet available. Still, a dramatic increase in research and development is taking place in the area of mmW packaging. The goal of this article is to provide a short overview of the topic and then present one particular approach in detail: the idea of integrating a complete mmW front end, including the antenna, into one small solderable surfacemount device (SMD).

Hybrid MMSE Precoding for Millimeter-Wave (mmW) Multi-user Massive MIMO Systems

Millimeter-wave (mmWave) cellular systems is considered to be the key enabling technology for the future 5G wireless communication systems because of its high data rates, low latency, high system capacity, and huge available bandwidths. However, in order to meet the increasing demand, mmWave communications need to overcome certain challenges including high path loss and interference which can be reduced by applying large antenna arrays to achieve high beamforming gains. Although multi-user beamforming can improve spectral efficiencies, full digital beamforming strategies used in the conventional microwave systems increase the hardware cost and consumes high power for large number of antennas in mmW systems. In this paper, a multi-user hybrid precoding structure is proposed for mmWave massive-MIMO channels utilizing MMSE precoders at the BS with perfect channel knowledge. Simulations show that the sum-rate obtained by the proposed hybrid precoding scheme is nearly similar to the single-user rate and also performs better compared to other hybrid precoding approaches.

5G Millimeter-Wave Antenna Array: Design and Challenges

As there has been an explosive increase in wireless data traffic, mmw communication has become one of the most attractive techniques in the 5G mobile communications systems. Although mmw communication systems have been successfully applied to indoor scenarios, various external factors in an outdoor environment limit the applications of mobile communication systems working at the mmw bands. In this article, we discuss the issues involved in the design of antenna array architecture for future 5G mmw systems, in which the antenna elements can be deployed in the shapes of a cross, circle, or hexagon, in addition to the conventional rectangle. The simulation results indicate that while there always exists a non-trivial gain fluctuation in other regular antenna arrays, the circular antenna array has a flat gain in the main lobe of the radiation pattern with varying angles. This makes the circular antenna array more robust to angle variations that frequently occur due to antenna vibration in an outdoor environment. In addition, in order to guarantee effective coverage of mmw communication systems, possible solutions such as distributed antenna systems and cooperative multi-hop relaying are discussed, together with the design of mmw antenna arrays. Furthermore, other challenges for the implementation of mmw cellular networks, for example, blockage, communication security, hardware development, and so on, are discussed, as are potential solutions.

A Revolution on the Horizon from DARPA: Heterogeneous Integration for Revolutionary Microwave\/Millimeter-Wave Circuits at DARPA: Progress and Future Directions

The Microsystems Technology Office of the U.S. Defense Advanced Research Projects Agency (DARPA) is developing revolutionary materials, devices, and integration techniques to meet the performance requirements for advanced microwave and millimeter-wave (mmW) systems. The DARPA Compound Semiconductor Materials on Silicon (COSMOS) program focused on developing new methods to tightly integrate compound semiconductor (CS) technologies within state-of-the-art silicon (Si) complementary?metal-oxide-semiconductor (CMOS) circuits to achieve unprecedented circuit performance levels. The DARPA Diverse Accessible Heterogeneous Integration (DAHI) program is continuing that work by developing heterogeneous integration processes to intimately combine advanced CS devices, as well as other emerging materials and devices, with high-density Si CMOS technology. DARPA has also pushed limits in Si technology and driven seminal developments in gallium nitride (GaN) device technology. Taken together, these programs are addressing many critical challenges for next-generation microwave and mmW systems and seek to revolutionize U.S. Department of Defense (DoD) capabilities in these areas.