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Adaptive analog beamforming is a key technology to enable spatial control of millimeter-wave wireless signals radiated from phased array antennas (PAAs) which is essential to maximize the capacity of future mobile networks and to ensure efficient usage of scarce spectrum. Intermediate frequency-over-fiber (IFoF), on the other hand, is a promising t...
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With the emergence of 5G and satellite communication applications, where millimeter-wave (mm-wave) active phased arrays play an important role, the demand for a highly integrated and cost-effective method to achieve mm-wave antennas is an inevitable trend. Antenna-in-package (AiP) design is therefore becoming a hotspot. This paper presents the desi...
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... When included, wireless ranges up to 10m are typically achieved when relying on standard horn antennas in indoor and regulated environments. Outdoor measurements with distances over 100m, based on a highly directive 8x8 patch phased arrayed antenna (PAA), are reported in [100], whereas a 4.6km long wireless link is obtained by relying on power amplifiers and dielectric lenses to maximize the wireless reach [110], [111]. However, in the context of MMW and sub-THz operation, dynamic radio beam steering and forming stand out as pivotal features. ...
... However, in the context of MMW and sub-THz operation, dynamic radio beam steering and forming stand out as pivotal features. Practical implementations found in the researched literature incorporate standard PAA electronic beam steering functionalities [100], [106]. While these demonstrate notable progress, the advantages of converged optical-radio approaches, such as photonically aided beam steering, are becoming increasingly apparent. ...
Towards supporting a myriad of new services and applications under highly heterogeneous operating conditions, while dynamically adapting to capacity and quality-of-service (QoS) demands, the sixth generation (6G) communication systems are required to undergo significant advances. Along with the proliferation of devices, a multitude of challenges remain towards aspired performance, versatility, security, and cost-effectiveness of next generation networks. The aim of this work is to identify said challenges and promising approaches, within the scenario of dense and complex urban deployments enabled by optical-wireless coexistence. Towards enabling such operation scenario, our 6G vision focuses on various aspects of four main innovation paradigms. First, as future systems target network capacities beyond the capabilities of current technologies, the scientific trend of pursuing radio frequencies edging towards the THz domain continues. To ensure reliable and efficient deployment and mobility under the cell densification paradigm, particularly in complex urban environments, novel approaches are required to address the challenges as latency, signal blockages, and unreliable handovers. Second, towards enabling efficient operation under the heterogeneous scenario, we highlight the cooperative coexistence paradigm as a key feature of the underlying physical layer architecture. Third, joint and holistic resource optimization is required towards dynamically optimized support of mm-wave and sub-THz operation while retaining legacy coexistence, where we consider features that may benefit from the research paths proposed within the second paradigm. Fourth, network security is identified as critical towards the market adoption of technologies proposed within the first paradigm, where we highlight aspects unique to our scenario and network vision. We provide a comprehensive overview of promising state-of-the-art approaches and identify relevant research gaps while holistically addressing the four aforementioned innovation paradigms.
... The new generation 5G and 6G wireless systems are expected to be used in many civil, commercial, and military areas such as massive multiple-input multiple-output (mMIMO) [5], [6], autonomous driving [7], satellite systems [3], internet of things (IoT) [4], anti-jamming, and antispoofing [8]. With the latest developments in phased array antenna technology, beamforming is intended to be one of the key techniques for the next generation wireless systems [1], [2], [9]. Beamforming techniques direct the pattern of the antenna array in the desired direction by varying the phase of each antenna element, maximizing signal-to-noise ratio (SNR), compensating for high path losses, distinguishing users, and canceling interference to improve signal quality [2], [9], [10]. ...
... With the latest developments in phased array antenna technology, beamforming is intended to be one of the key techniques for the next generation wireless systems [1], [2], [9]. Beamforming techniques direct the pattern of the antenna array in the desired direction by varying the phase of each antenna element, maximizing signal-to-noise ratio (SNR), compensating for high path losses, distinguishing users, and canceling interference to improve signal quality [2], [9], [10]. Depending on the application, beamforming system architectures can be active, hybrid or fully digital [2]. ...
This paper proposes a mutual coupling based self-calibration method for transmit mode large scale antenna arrays. In accord with the proposed active antenna array model, gain/phase uncertainties, antenna element position errors and mutual coupling effects are reduced to an error matrix. The expansion of equations of the proposed calibration method are presented. The proposed calibration procedure is capable of compensating the error matrix while the system is operating and is suitable for off-line, on-site and online calibration procedures. The calibration procedure relies on the measurements of the error signal related to scan reflection coefficient while the system is operating, and the premeasured inter-element couplings. The calibration system takes pre-measured couplings, the geometry of the antenna array, the antenna weights and pointing direction as input, then, during the operation it combines input with the measured feedback signals to construct an array manifold. The coefficients of the error matrix are later estimated from the array manifold. The antenna weights are compensated by direct inversion of the estimated error matrix which involves division operator, yielding possible inaccurate coefficient estimation in hardware. Therefore, a globally convergent generalized inverse matrix approximation method is adopted. Simulation results with worst case errors and a simple experimental study are presented. The results show that with the proposed method, accurate calibration can be made with couplings only in the first and second order neighbors of an antenna element.
In the epoch of the fifth generation (5G) of wireless communication, this survey article
illuminates the nuanced landscape of 5G Channel Measurements and Models. It meticulously navigates the
challenges, methodologies, and practical implications that define the implementation of this groundbreaking
technology. Embarking on the exploration, the article unravels the Challenges in 5G Implementation,
addressing technological hurdles and standardized protocols pivotal for seamless integration. Unveiling the
Existing Methods and Technologies, it highlights Massive MIMO, millimeter-wave communications, and the
integration of artificial intelligence (AI) as transformative elements shaping high-capacity wireless
communication. Beyond the technical intricacies, the article delves into the Diverse Applications and Use
Cases of 5G, promising a paradigm shift from the Internet of Things (IoT) to mission-critical communications.
Frequency Considerations and Channel Bands take center stage, dissecting the critical spectrum domain and
exploring high-frequency millimeter-wave bands for enhanced data rates. Addressing concerns, the survey
scrutinizes Health Concerns and Regulatory Considerations, presenting a balanced perspective on the impact
of 5G networks on health and regulatory landscapes. The Benefits Over 4G and LTE drive the transition,
with enhanced data rates, lower latency, and massive device connectivity distinguishing 5G. The
environmental impact is considered in Energy Efficiency in 5G Networks, exploring strategies and
innovations for making 5G networks more energy-efficient. Global Standards and Interoperability become
imperative for 5G's global potential, examining ongoing efforts by standardization bodies for a unified
framework. The exploration extends to the realm of 5G Channel Measurements and Models, dissecting
Massive MIMO Channel Measurements, Millimeter-Wave Channel Measurements, Beamforming, Antenna
Array Configurations, Time-Variant, and Time-Invariant Channel Measurements, Channel Modeling, and
Measurement Tools and Techniques. Critically addressing Challenges in 5G Channel Measurements and
Models, the article explores limitations and proposes avenues for future research. This survey article serves
as a definitive compendium on 5G Channel Measurements and Models, unraveling the complexities,
challenges, and opportunities inherent in the deployment of this transformative technology. Its holistic
examination provides a valuable resource for researchers, practitioners, and industry stakeholders navigating
the dynamic landscape of 5G wireless communication.
In the rapidly evolving landscape of wireless communication, each successive generation of networks has achieved significant technological leaps, profoundly transforming the way we connect and interact. From the analog simplicity of 1G to the digital prowess of 5G, the journey of mobile networks has been marked by constant innovation and escalating demands for faster, more reliable, and more efficient communication systems. As 5G becomes a global reality, laying the foundation for an interconnected world, the quest for even more advanced networks leads us to the threshold of the sixth-generation (6G) era. This paper presents a hierarchical exploration of 6G networks, poised at the forefront of the next revolution in wireless technology. This study delves into the technological advancements that underpin the need for 6G, examining its key features, benefits, and key enabling technologies. We dissect the intricacies of cutting-edge innovations like terahertz communication, ultra-massive MIMO, artificial intelligence (AI), machine learning (ML), quantum communication, and reconfigurable intelligent surfaces. Through a meticulous analysis, we evaluate the strengths, weaknesses, and state-of-the-art research in these areas, offering a wider view of the current progress and potential applications of 6G networks. Central to our discussion is the transformative role of AI in shaping the future of 6G networks. By integrating AI and ML, 6G networks are expected to offer unprecedented capabilities, from enhanced mobile broadband to groundbreaking applications in areas like smart cities and autonomous systems. This integration heralds a new era of intelligent, self-optimizing networks that promise to redefine the parameters of connectivity and digital interaction. We also address critical challenges in the deployment of 6G, from technological hurdles to regulatory concerns, providing a holistic assessment of potential barriers. By highlighting the interplay between 6G and AI technologies, this study maps out the current landscape and lights the path forward in this rapidly evolving domain. This paper aims to be a cornerstone resource, providing essential insights, addressing unresolved research questions, and stimulating further investigation into the multifaceted realm of 6G networks. By highlighting the synergy between 6G and AI technologies, we aim to illuminate the path forward in this rapidly evolving field.
This manuscript proposes a dual-band dual-polarized 64-element phased array antenna (PAA) with suppressed higher order modes (HoMs). Each array element is a microstrip patch structure with complementary split ring resonator (CSRR) loading, allowing for simultaneous dual-band and dual-polarization performance at 3.45 GHz and 3.87 GHz. The proposed PAA exhibits impedance matching of $$\le - 20$$ ≤ - 20 dB at 3.45 GHz and 3.87 GHz while limiting the mutual coupling below $$- 19$$ - 19 dB between the adjacent elements at both the operating bands. The proposed design includes a plated through hole placed near the CSRR loading to suppress any higher-order modes (HOMs). Two antenna prototypes, without and with HOMs suppression techniques are fabricated and measured. In addition, we demonstrate the beam steering of the proposed PAA up to $$\pm 60^0$$ ± 60 0 using an off-the-shelf 6-bit phase shifter module. The proposed 64 -element array achieves a gain of 23 dBi, and shows a minimal steering loss of $$\simeq 3$$ ≃ 3 dB over the steering angle.
This paper investigates a millimeter-wave sigma-delta-over-fiber distributed multiple-input-multiple-output (D-MIMO) solution, in which a central unit connects two remote radio heads (RRH) with two standardized QSFP28 fiber connections. The four subchannels of the QSFP28 carry three individually controlled intermediate frequency (IF) sigma-delta modulated bitstreams and one local oscillation signal to each RRH. At each RRH, the upconversion to mm-wave frequency is performed while maintaining full phase coherence between all channels and distributed RRHs. This solution offers an effective and scalable way to feed multiple radio heads with coherent signals proper for high performance millimeter-wave D-MIMO systems. Wireless performance of the transmitter is experimentally verified by multiple-input-single-output (MISO) and multiple-user MIMO cases in a 1.4 m × 1.6 m area with 748 MHz wideband signals. The comparison with other publications shows that the proposed system is the first millimeter-wave sigma-delta-over-fiber D-MIMO solution that serves multiple users and reaches the largest bandwidth.
