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1
Lee, Hyukjun, Wonjae Ryu, Wonjin Sung, and Jonghyun Park. "Beamforming for Rotated 3D Multipanel Array Structures for 5G NR MIMO Transmission." International Journal of Antennas and Propagation 2019 (July 7, 2019): 1–11. http://dx.doi.org/10.1155/2019/2830792.
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5G new radio (NR) provides enhanced transmission capabilities to transceivers by utilizing the massive multiple-input multiple-output (MIMO) technology with a significantly increased number of antenna elements. Such transmission requires massive arrays to perform accurate high-gain beamforming over the millimeter-wave frequency band. There is no fixed form of array structures for 5G NR base stations, but they are likely to include multiple subarrays or panels for practicality of implementation and are expected to cover the user equipment (UE) in various locations. In this paper, we propose an array structure to transmit signals over the three-dimensional (3D) space in an isotropic fashion for all types of UEs in ground, aerial, and high-rise building locations, by employing panels on surfaces of a polyhedron. We further derive exact beamforming equations for the proposed array and show the resulting beams provide improved receiver performance over the exiting conventional beamforming. The presented beamforming expressions can be applied to an arbitrary multipanel array with massive antenna elements.
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Noor, Hidayah Muhamad Adnan, Md. Rafiqul Islam, and Zahirul Alam AHM. "Effects of Inter-Element Spacing and Number of Elements on Planar Array Antenna Characteristics." Indonesian Journal of Electrical Engineering and Computer Science 10, no. 1 (2018): 230–40. https://doi.org/10.11591/ijeecs.v10.i1.pp230-240.
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Planar array antenna is seen as one of the innovative solutions of massive MIMO and 5G networks since they provide directive beams. In this paper, planar array antenna with square and rectangular arrangements based on 2 x 2 antenna elements as one subarray was proposed. Then, array factor for the the planar array antenna with up to 64 antenna elements was calculated to analyze the effects of inter-element spacing and number of elements on the antenna characteristics. Higher values of inter-element spacing contributed to higher number of side lobes, narrower main lobe, higher directivity and lower half power beamwidth (HPBW). Inter-element spacing equals to 0.5λ was found to be the most suitable value for planar array antenna design based on the analysis. Meanwhile, higher number of antenna elements increased the value of directivity of the planar array with narrower HPBW. Therefore, there is a tradeoff between directivity and HPBW in designing planar array antenna for massive MIMO application.
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Dicandia, Francesco Alessio, and Simone Genovesi. "Spectral Efficiency Improvement of 5G Massive MIMO Systems for High-Altitude Platform Stations by Using Triangular Lattice Arrays." Sensors 21, no. 9 (2021): 3202. http://dx.doi.org/10.3390/s21093202.
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The beneficial effects of adopting a triangular lattice on phased arrays with regular and periodic grids for high-altitude platform station (HAPS) systems are presented in the scenario of massive MIMO communications operating within the 5G NR n257 and n258 frequency bands. Assessment of a planar array with 64 elements (8 × 8) is provided for both a triangular lattice and a square one in terms of array gain, average sidelobe level (ASLL), and mutual coupling. Particular attention is devoted to illustrating the impact of the antenna array lattice at the system level by evaluating its significant merits, such as its spectral efficiency (SE) and signal-to-interference ratio (SIR). The better performance exhibited by the triangular lattice array in comparison to the square one makes it appealing for the 5G massive MIMO paradigm.
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Gong, Pan, Tanveer Ahmed, and Jianfeng Li. "Three-Dimensional Coprime Array for Massive MIMO: Array Configuration Design and 2D DOA Estimation." Wireless Communications and Mobile Computing 2020 (January 13, 2020): 1–14. http://dx.doi.org/10.1155/2020/2686257.
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In massive multiple-input multiple-output (MIMO) systems, it is critical to obtain the accurate direction of arrival (DOA) estimation. Conventional three-dimensional array mainly focuses on the uniform array. Due to the dense arrangement of the sensors, the array aperture is limited and severe mutual coupling effects arise. In this paper, a coprime cubic array (CCA) configuration design is presented, which is composed of two uniform cubic subarrays and can extend the interelement spacing with a selection of three pairs of coprime integers. Compared with uniform cubic array (UCA), CCA achieves the larger array aperture and less MC effects. And the analytical expression of Cramer–Rao Bound (CRB) for CCA is derived which verifies that the proposed CCA geometry outperforms the conventional UCA in two-dimensional (2D) DOA estimation performance in massive MIMO systems. Meanwhile, we propose a computationally efficient 2D DOA estimation algorithm with high accuracy for CCA. Specifically, we utilize array mapping to extract two uniform arrays from the nonuniform array by exploiting the relation derived from the signal subspace and the two directional matrices. Then, we operate a reduced dimension process on the uniform arrays and convert the 2D spectrum peak searching (SPS) problem into one-dimensional (1D) one, which significantly reduces the computational complexity. In addition, we employ the polynomial root finding technique with a lower complexity instead of 1D SPS to further relieve the computational complexity. Simultaneously, with coprime property, the phase ambiguity problem is solved, which results from the large interelement spacing. Numerical simulation results demonstrate that the proposed algorithm is very computationally efficient without degradation of DOA estimation performance.
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Wu, Wei, Yunfei Wang, Xiaofei Zhang, and Jianfeng Li. "Computationally Efficient Sources Location Method for Nested Array via Massive Virtual Difference Co-Array." Sensors 19, no. 9 (2019): 1961. http://dx.doi.org/10.3390/s19091961.
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In this paper, we derive the discrete Fourier transform (DFT) method for direction of arrival (DOA) estimation by generating the massive virtual difference co-array with the nested array. By contrast with the spatial smoothing (SS) subspace-based methods for nested array, which halve the array aperture, the proposed method can take full advantage of the total array aperture. Since the conventional DFT method is a non-parametric method and is limited by Rayleigh threshold, we perform the phase rotation operation to obtain the fine DOA estimates. Owing to the full utilization of the array aperture and phase rotation operation, the proposed method can achieve better performance than SS subspace-based methods for far-field sources especially with massive virtual difference co-arrays which possess a large number of virtual sensors. Besides, as the fast Fourier transform (FFT) is attractive in practical implementation, the proposed method lowers the computational cost, as compared with the subspace-based methods. Numerical simulation results validate the superiority of the proposed method in both estimation performance and complexity.
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Su, Xin, Jie Zeng, Jingyu Li, et al. "Limited Feedback Precoding for Massive MIMO." International Journal of Antennas and Propagation 2013 (2013): 1–9. http://dx.doi.org/10.1155/2013/416352.
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The large-scale array antenna system with numerous low-power antennas deployed at the base station, also known as massive multiple-input multiple-output (MIMO), can provide a plethora of advantages over the classical array antenna system. Precoding is important to exploit massive MIMO performance, and codebook design is crucial due to the limited feedback channel. In this paper, we propose a new avenue of codebook design based on a Kronecker-type approximation of the array correlation structure for the uniform rectangular antenna array, which is preferable for the antenna deployment of massive MIMO. Although the feedback overhead is quite limited, the codebook design can provide an effective solution to support multiple users in different scenarios. Simulation results demonstrate that our proposed codebook outperforms the previously known codebooks remarkably.
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Ding, Xuhui, Jiawen Chen, Dekang Liu, Bizheng Liang, and Xiangyuan Bu. "Sparse Multiuser Receiver Design in Large Scale Array System." Electronics 12, no. 4 (2023): 996. http://dx.doi.org/10.3390/electronics12040996.
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This paper focuses on the problem of utilizing millimeter wave (mmWave) and Terahertz (THz) massive hybrid arrays to serve multiple users simultaneously. The mmWave and THz massive arrays are characterized by wide bandwidth and high gain, leading to extensive application prospects. Moreover, a hybrid structure array can combine multiple antenna signals through the phase shifter network. Compared with the full digital array, it is a cost-effective technique that can be functional with fewer radio frequency (RF) chains. However, owing to the adoption of a discrete Fourier transform (DFT) structure, most traditional massive hybrid arrays, which allocate one chain to each user, are restricted to scenarios where the number of RF chains is more than that of users. Otherwise, even users with ideal channel conditions and short distances are inherently difficult to assign an independent chain. Thus, it will limit the scale of users that the base station (BS) can support. Inspired by the above analysis, this paper develops a method to provide service for more users with limited RF chains. Firstly, an analog matrix designing method based on the minimax criterion, which enables arrays access to multiple users, is proposed to guarantee each user a good array gain. Secondly, we establish a receiver designing scheme by the GAMP algorithm to receive signals from multiple users at the same time. Additionally, good bit error rate (BER) performance can be obtained under the condition that the observation matrix is not of full rank. Finally, numerical simulations demonstrate the effectiveness of our proposed method.
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Anam, Mohamad Khoirul, Yudhistira Yudhistira, and Sangjo Choi. "Optimization of Thermoelectric Nanoantenna for Massive High-Output-Voltage Arrays." Nanomaterials 14, no. 13 (2024): 1159. http://dx.doi.org/10.3390/nano14131159.
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Thermoelectric nanoantennas have been extensively investigated due to their ability to directly convert infrared (IR) radiation into direct current without an additional rectification device. In this study, we introduce a thermoelectric nanoantenna geometry for maximum output voltage (Voc) and propose an optimal series array configuration with a finite number of antennas to enhance the Voc. A finite and open-ended SiO2 substrate, with a thickness of a quarter-effective wavelength at a frequency of 28.3 THz, is used to generate standing waves within the substrate. An array of antennas is then positioned optimally on the substrate to maximize the temperature difference (∆T) between hot and cold areas, thereby increasing the average Voc per antenna element. In numerical simulations, a linearly polarized incident wave with a power density of 1.42 W/cm2 is applied to the structure. The results show that a single antenna with the optimum geometry on a substrate measuring 35 µm × 35 µm generates a ∆T of 64.89 mK, corresponding to a Voc of 1.75 µV. Finally, a series array of 5 × 6 thermoelectric nanoantennas on a 150 µm × 75 µm substrate including measurement pads achieves an average ∆T of 49.60 mK with a total Voc of 40.18 µV, resulting in an average Voc of 1.34 µV per antenna element and a voltage responsivity (βv) of 0.77 V/W. This value, achieved solely by optimizing the antenna geometry and open-ended substrate, matches or exceeds the Voc and βv of approximately 1 µV and 0.66 V/W, respectively, from suspended thermoelectric antenna arrays over air cavities. Therefore, the proposed thermoelectric nanoantenna array device, characterized by high stability and ease of fabrication, is suitable for manufacturing massive nanoantenna arrays for high-output IR-DC energy harvesters.
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Lu, Xing, Qizhou Zhang, Jens Kauffmann, and Thushara Pillai. "SMA observations towards massive clouds in the central molecular zone." Proceedings of the International Astronomical Union 9, S303 (2013): 191–93. http://dx.doi.org/10.1017/s1743921314000532.
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AbstractRecently we conducted a mini-survey towards a sample of six massive clouds with surface density >1024 cm−2 in the central molecular zone (CMZ) of the Milky Way, with the SMA at 280 GHz in the compact array and at 230 GHz in the compact/subcompact arrays. The data reveal compact dust continuum peaks, some of which are also associated with organic molecular lines and thermal SiO emission. The subcompact array data helps recover more structures, e.g. the regularly spaced, well-aligned continuum fragments in the 20 km s−1 cloud. Shock tracers such as SiO are found in all the clouds. Our observations suggest potential protostellar origin for some of the dust continuum peaks in these regions.
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Alnajjar, Khawla A., Peter J. Smith, Philip Whiting, and Graeme K. Woodward. "Size and Array Shape for Massive MIMO." IEEE Wireless Communications Letters 4, no. 6 (2015): 653–56. http://dx.doi.org/10.1109/lwc.2015.2477513.
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Tengah, Zanurlida, Nurul Huda Abd Rahman, Yoshihide Yamada, and Suhaila Subahir. "DESIGN OF CONVEX AND CONCAVE DUAL BENT ARRAY FOR 5G LENS ANTENNA SYSTEM." ASEAN Engineering Journal 12, no. 3 (2022): 143–48. http://dx.doi.org/10.11113/aej.v12.17326.
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Previous research on the multi-beam system for the fifth generation (5G) application has shown that the number of feed elements of a lens antenna system at the mobile base station is increasing due to the massive MIMO requirements. The design of the array circuits of the 5G lens antenna systems will be more complicated due to the feeding structure, which consists of the power dividers and phase shifters, thus contributing to higher feeding losses. The antenna fabrication process also becomes more complicated. Besides that, the conventional array feed also produces a single radiation beam only. Thus, a large space is needed, where array feed antennas should be arranged to perform wide-angle beam scanning for 5G massive MIMO operation. Therefore, to overcome these issues, this paper uses a bent array configuration as the lens antenna feed to produce bifurcated beam radiation and has a wide beam angle from the feed radiator to the lens edge. Multiple bent arrays are arranged on the lens axis to generate a multi-beam by cylindrical lens antenna. This paper shows a comparison of the bent array in convex and concave configurations. This process investigates the mutual coupling when more than one bent array is arranged as feed radiators. By comparing the arrays in convex and concave structures, it is observed that the convex structure produces a better-bifurcated beam with a smaller middle lobe. The antenna also produces the same bifurcated beam shifting angle, θs for both ports, when s = 4λ is used. It is verified as the optimum spacing value between two bent array structures by the optimization process.
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Khan, Anindita, and Jibendu Roy. "Design of thinned smart antenna of semi-circular dipole array for 5G massive MIMO system." Facta universitatis - series: Electronics and Energetics 37, no. 3 (2024): 409–22. https://doi.org/10.2298/fuee2403409k.
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In a multi-user environment, wireless networks should be massive MIMO (MMIMO) systems consisting of multiple antennas. MMIMO installs antenna arrays at base stations and uses hundreds of transceivers and other RF modules to form a very narrow and focused beam, thus reducing interference. The disadvantage of MMIMO systems is large power consumption, and the RF module beamforming network for multiple antennas is significant in terms of power consumption. This paper presents a new low power beamforming technique for MMIMO systems. The proposed semicircular array thinned smart antenna (TSA) can form a secure beam for user terminals while reducing interference. In a thinned array, selected antennas are kept off, which reduces power consumption but the array pattern remains the same as the built-in array, and the sidelobe level (SLL) is reduced. The thinned array antennas are designed at 5 GHz of the sub-6GHz band. The differential evolution (DE) algorithm is utilized to determine the optimal array sequence and least mean square (LMS), recursive least square (RLS), and sample matrix inversion (SMI) algorithms are used for beam generation of the TSA and the algorithms are DE-LMS, DE-RLS and DE-SMI. A maximum of 48% energy savings is achieved. Using the DE-LMS, DE-RLS and DE-SMI algorithms, TSA achieved maximum SLL reduction of 11 dB, 11 dB and 9 dB, respectively.
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Gadiel, Godwin Mruma. "Performance Evaluation of Full Array, Sub-Array and Overlapped-Sub-Array Hybrid Beamforming Architectures for Massive Mimo Systems." Tanzania Journal of Engineering and Technology 42, no. 2 (2023): 134–40. http://dx.doi.org/10.52339/tjet.v42i2.797.
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The technological advancement in wireless communication, promises high data rate for end users. This has led to the possibility of smart cities, inter connected vehicles, and virtual reality applications. One of the recent technologies in wireless communication is massive MIMO where large number of antennas are deployed at the transmitter or receiver. This is possible due to the use of mmWave in wireless communication. With massive MIMO, beamforming technique can be employed in the communication system. Beamforming is the ability of communication system to direct power to the intended users and to cancel power at non-intended users and thus significantly improving communication system performance. Digital beamforming was initially used in MIMO systems. However, for massive MIMO systems it leads to high power consumption due to large number of dedicated radio frequency chain in each antenna. To address this challenge, hybrid beamforming techniques were introduced. There are three architectures for hybrid beamforming: Fully array architecture (FAA), overlapped sub-array architecture (OSA) and sub-array architecture (SAA). This paper has analysed three performance parameters of the mentioned hybrid beamforming architectures. The simulation results show that, FAA architecture has high performance in outage probability and spectral efficiency. However, its energy efficiency is lower compared to OSA and SAA. Specifically, SAA has the highest energy efficiency in comparison to FAA and OSA. It can also be observed that, with only 25% increased number of elements in OSA, the energy efficiency can be slightly lower compared to SAA, while achieving appreciable spectral efficiency performance with respect to FAA. Additionally, this work has derived an outage probability expression, which has not been covered in most of the studies. This study gives an insight of selecting the best architecture based on the performance requirement.
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Zalipynis, Ramon Antonio Rodriges. "FastMosaic in Action: A New Mosaic Operator for Array DBMSs." Proceedings of the VLDB Endowment 16, no. 12 (2023): 3938–41. http://dx.doi.org/10.14778/3611540.3611590.
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Array DBMSs operate on N -d arrays. During the Data Ingestion phase, the widely used mosaic operator ingests a massive collection of overlapping arrays into a single large array, called mosaic. The operator can utilize sophisticated statistical and machine learning techniques, e.g. Canonical Correlation Analysis (CCA), to produce a high quality seamless mosaic where the contrasts between the values of cells taken from input overlapping arrays are minimized. However, the performance bottleneck becomes a major challenge when applying such advanced techniques over increasingly growing array volumes. We introduce a new, scalable way to perform CCA that is orders of magnitude faster than the popular Python's scikit-learn library for the purpose of array mosaicking. Furthermore, we developed a hybrid web-desktop application to showcase our novel FastMosaic operator, based on this new CCA. A rich GUI enables users to comprehensively investigate in/out arrays, interactively guides through an end-to-end mosaic construction on real-world geospatial arrays using FastMosaic, facilitating a convenient exploration of the FastMosaic pipeline and its internals.
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Lonkeng, Alban Doumtsop, and Jie Zhuang. "Two-Dimensional DOA Estimation Using Arbitrary Arrays for Massive MIMO Systems." International Journal of Antennas and Propagation 2017 (2017): 1–9. http://dx.doi.org/10.1155/2017/6794920.
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With the quick advancement of wireless communication networks, the need for massive multiple-input-multiple-output (MIMO) to offer adequate network capacity has turned out to be apparent. As a portion of array signal processing, direction-of-arrival (DOA) estimation is of indispensable significance to acquire directional data of sources and to empower the 3D beamforming. In this paper, the performance of DOA estimation for massive MIMO systems is analyzed and compared using a low-complexity algorithm. To be exact, the 2D Fourier domain line search (FDLS) MUSIC algorithm is studied to mutually estimate elevation and azimuth angle, and arbitrary array geometry is utilized to represent massive MIMO systems. To avoid the computational burden in estimating the data covariance matrix and its eigenvalue decomposition (EVD) due to the large-scale sensors involved in massive MIMO systems, the reduced-dimension data matrix is applied on the signals received by the array. The performance is examined and contrasted with the 2D MUSIC algorithm for different types of antenna configuration. Finally, the array resolution is selected to investigate the performance of elevation and azimuth estimation. The effectiveness and advantage of the proposed technique have been proven by detailed simulations for different types of MIMO array configuration.
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Salsabila, Salwa, Rina Pudjiastuti, Levy Olivia Nur, Harfan Hian Ryanu, and Bambang Setia Nugroho. "Scalable modular massive MIMO antenna of rectangular truncated corner patch antenna and circular slotted X patch antenna for 5G antenna communication." JURNAL INFOTEL 15, no. 3 (2023): 274–80. http://dx.doi.org/10.20895/infotel.v15i3.962.
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Massive MIMO Antenna Design results in a very large antenna size that hinders the design process. The arrangement of Massive MIMO Antennas which consists of many antenna elements is a challenge in the design process due to the limited capability of the simulation software and the complicated process. Thus, a scalability technique is used to predict the specification results produced by a Massive MIMO Antenna array with a certain configuration based on a simple MIMO Antenna array with a 2x2, 4x4, 8x8, 16x16 MIMO element configuration scheme, etc. exponential increments. This research will discuss the scaling process to predict the specifications of a Massive MIMO Antenna array. The designed MIMO antenna arrangement is based on the design of a rectangular antenna with a truncated corner and a circular antenna with an X slot for further design with various types of configurations that work at a frequency of 3.5 GHz.
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Shikhantsov, Sergei, Arno Thielens, Sam Aerts, et al. "Ray-Tracing-Based Numerical Assessment of the Spatiotemporal Duty Cycle of 5G Massive MIMO in an Outdoor Urban Environment." Applied Sciences 10, no. 21 (2020): 7631. http://dx.doi.org/10.3390/app10217631.
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In the near future, wireless coverage will be provided by the base stations equipped with dynamically-controlled massive phased antenna arrays that direct the transmission towards the user. This contribution describes a computational method to estimate realistic maximum power levels produced by such base stations, in terms of the time-averaged normalized antenna array gain. The Ray-Tracing method is used to simulate the electromagnetic field (EMF) propagation in an urban outdoor macro-cell environment model. The model geometry entities are generated stochastically, which allowed generalization of the results through statistical analysis. Multiple modes of the base station operation are compared: from LTE multi-user codebook beamforming to the more advanced Maximum Ratio and Zero-Forcing precoding schemes foreseen to be implemented in the massive Multiple-Input Multiple-Output (MIMO) communication protocols. The influence of the antenna array size, from 4 up to 100 elements, in a square planar arrangement is studied. For a 64-element array, the 95th percentile of the maximum time-averaged array gain amounts to around 20% of the theoretical maximum, using the Maximum Ratio precoding with 5 simultaneously connected users, assuming a 10 s connection duration per user. Connection between the average array gain and actual EMF levels in the environment is drawn and its implications on the human exposure in the next generation networks are discussed.
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Bilel, Hamdi, and Aguili Taoufik. "Floquet Spectral Almost-Periodic Modulation of Massive Finite and Infinite Strongly Coupled Arrays: Dense-Massive-MIMO, Intelligent-Surfaces, 5G, and 6G Applications." Electronics 11, no. 1 (2021): 36. http://dx.doi.org/10.3390/electronics11010036.
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In this study, we introduce a new formulation based on Floquet (Fourier) spectral analysis combined with a spectral modulation technique (and its spatial form) to study strongly coupled sublattices predefined in the infinite and large finite extent of almost-periodic antenna arrays (e.g., metasurfaces). This analysis is very relevant for dense-massive-MIMO, intelligent-surfaces, 5G, and 6G applications (used for very small areas with a large number of elements such as millimeter and terahertz waves applications). The numerical method that is adopted to model the structure is the method of moments simplified by equivalent circuits MoM GEC. Other numerical methods (such as the ASM-array scanning method and the windowing Fourier method) used this analysis in their kernel to treat periodic and pseudo-periodic (or quasi-periodic) arrays.
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Albagory, Yasser, and Fahad Alraddady. "An Efficient Adaptive and Steep-Convergent Sidelobes Simultaneous Reduction Algorithm for Massive Linear Arrays." Electronics 11, no. 2 (2022): 170. http://dx.doi.org/10.3390/electronics11020170.
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Antenna arrays have become an essential part of most wireless communications systems. In this paper, the unwanted sidelobes in the symmetric linear array power pattern are reduced efficiently by utilizing a faster simultaneous sidelobes processing algorithm, which generates nulling sub-beams that are adapted to control and maintain steep convergence toward lower sidelobe levels. The proposed algorithm is performed using adaptive damping and heuristic factors which result in learning curve perturbations during the first few loops of the reduction process and is followed by a very steep convergence profile towards deep sidelobe levels. The numerical results show that, using the proposed adaptive sidelobes simultaneous reduction algorithm, a maximum sidelobe level of −50 dB can be achieved after only 10 iteration loops (especially for very large antenna arrays formed by 256 elements, wherein the processing time is reduced to approximately 25% of that required by the conventional fixed damping factor case). On the other hand, the generated array weights can be applied to practical linear antenna arrays under mutual coupling effects, which have shown very similar results to the radiation pattern of the isotropic antenna elements with very deep sidelobe levels and the same beamwidth.
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Ding, Mingjun, Xiaodong Yang, Rui Hu, Zhitao Xiao, Jun Tong, and Jiangtao Xi. "On Matrix Completion-Based Channel Estimators for Massive MIMO Systems." Symmetry 11, no. 11 (2019): 1377. http://dx.doi.org/10.3390/sym11111377.
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Large-scale symmetric arrays such as uniform linear arrays (ULA) have been widely used in wireless communications for improving spectrum efficiency and reliability. Channel state information (CSI) is critical for optimizing massive multiple-input multiple-output(MIMO)-based wireless communication systems. The acquisition of CSI for massive MIMO faces challenges such as training shortage and high computational complexity. For millimeter wave MIMO systems, the low-rankness of the channel can be utilized to address the challenge of training shortage. In this paper, we compared several channel estimation schemes based on matrix completion (MC) for symmetrical arrays. Performance and computational complexity are discussed and compared. By comparing the performance in different scenarios, we concluded that the generalized conditional gradient with alternating minimization (GCG-Alt) estimator provided a low-cost, robust solution, while the alternating direction method of multipliers (ADMM)-based hybrid methods achieved the best performance when the array response was perfectly known.
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Zheng, Kan, Suling Ou, and Xuefeng Yin. "Massive MIMO Channel Models: A Survey." International Journal of Antennas and Propagation 2014 (2014): 1–10. http://dx.doi.org/10.1155/2014/848071.
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The exponential traffic growth of wireless communication networks gives rise to both the insufficient network capacity and excessive carbon emissions. Massive multiple-input multiple-output (MIMO) can improve the spectrum efficiency (SE) together with the energy efficiency (EE) and has been regarded as a promising technique for the next generation wireless communication networks. Channel model reflects the propagation characteristics of signals in radio environments and is very essential for evaluating the performances of wireless communication systems. The purpose of this paper is to investigate the state of the art in channel models of massive MIMO. First, the antenna array configurations are presented and classified, which directly affect the channel models and system performance. Then, measurement results are given in order to reflect the main properties of massive MIMO channels. Based on these properties, the channel models of massive MIMO are studied with different antenna array configurations, which can be used for both theoretical analysis and practical evaluation.
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Zhao, Renjie, Timothy Woodford, Teng Wei, Kun Qian, and Xinyu Zhang. "M-CUBE." GetMobile: Mobile Computing and Communications 25, no. 1 (2021): 30–33. http://dx.doi.org/10.1145/3471440.3471449.
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Millimeter-wave (mmWave) technologies represent a cornerstone for emerging wireless network infrastructure, and for RF sensing systems in security, health, and automotive domains. However, the lack of an experimental platform has been impeding research in this field. In this article, we propose to fill the gap with M3 (M-Cube), the first mmWave massive MIMO software radio. M3 features a fully reconfigurable array of phased arrays, with up to 8 RF chains and 256 antenna elements. Despite the orders of magnitude larger antenna arrays, its cost is orders of magnitude lower, even when compared with state-of-the-art single RF chain mmWave software radios. Case studies have demonstrated the usefulness of M3 design for research in mmWave massive MIMO communication and sensing.
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Hidayah Muhamad Adnan, Noor, Islam Md. Rafiqul, and AHM Zahirul Alam. "Effects of Inter-Element Spacing and Number of Elements on Planar Array Antenna Characteristics." Indonesian Journal of Electrical Engineering and Computer Science 10, no. 1 (2018): 230. http://dx.doi.org/10.11591/ijeecs.v10.i1.pp230-240.
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<p>Planar array antenna is seen as one of the innovative solutions of massive MIMO and 5G networks since they provide directive beams. In this paper, planar array antenna with square and rectangular arrangements based on 2 x 2 antenna elements as one subarray was proposed. Then, array factor for the the planar array antenna with up to 64 antenna elements was calculated to analyze the effects of inter-element spacing and number of elements on the antenna characteristics. Higher values of inter-element spacing contributed to higher number of side lobes, narrower main lobe, higher directivity and lower half power beamwidth (HPBW). Inter-element spacing equals to 0.5λ was found to be the most suitable value for planar array antenna design based on the analysis. Meanwhile, higher number of antenna elements increased the value of directivity of the planar array with narrower HPBW. Therefore, there is a tradeoff between directivity and HPBW in designing planar array antenna for massive MIMO application. </p><p> </p>
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Yang, Jiyeong, Wonjae Ryoo, Wonjin Sung, Jeong-Ho Kim, and Jonghyun Park. "3D Antenna Structures Using Uniform Triangular Arrays for Efficient Full-Directional Multiuser Transmission." International Journal of Antennas and Propagation 2019 (November 5, 2019): 1–12. http://dx.doi.org/10.1155/2019/4150378.
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In order to increase the system capacity of the 5G mobile communication system, multiple-input multiple-output (MIMO) transmission techniques using a large-scale array over the millimeter-wave band have attracted a great amount of attention. To cope with various types of receivers expected in 5G communications such as user equipment (UE) in small cells, indoor Internet-of-Things (IoT) devices at diverse locations, and drones performing aerial navigation, newer types of antenna arrays require all-directional transmission capability. Existing antenna structures with typical panel arrays, however, have restrictions on their transmission angles in both horizontal and vertical directions. In this paper, we propose to employ three-dimensional (3D) array structures composed of multiple triangular panels for efficient massive MIMO transmission of the next-generation wireless systems. We analyze beamforming characteristics of a uniform triangular array (UTA) suitable for such 3D array configurations and present a basic codebook applicable to UTAs. Using antenna structures with multiple UTA panels, multiuser transmission performance is evaluated to demonstrate the effectiveness of the proposal.
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Чирков, О. Н., and Ю. М. Пшеницина. "THE EFFECT OF ANTENNA ARRAY GEOMETRY ON DATA TRANSMISSION IN MASSIVE MIMO." ВЕСТНИК ВОРОНЕЖСКОГО ГОСУДАРСТВЕННОГО ТЕХНИЧЕСКОГО УНИВЕРСИТЕТА 20, no. 1 (2024): 51–56. http://dx.doi.org/10.36622/1729-6501.2024.20.1.008.
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исследуется влияние геометрии антенной решетки на производительность сетей массивных MIMO при передаче данных внутри помещений. Многопользовательские массивные системы пространственного кодирования сигнала с множественными входами и множественными выходами (системы из нескольких антенн MIMO) будут играть ключевую роль в будущих сетях беспроводной связи. Различие между каналами пространственного разнесения представляет собой ключевое преимущество технологии многоатенного кодирования, сильная зависимость между каналами имеет потенциал ограничить качество и эффективность передачи информации. Исследование направлено на изучение воздействия корреляции между каналами на прототипную модель MIMO сети с целью определения оптимальной геометрии антенной решетки, которая минимизирует взаимное влияние и корреляцию сигналов в каналах. В результате исследования был разработан эффективный высоконаправленный широкополосный одиночный антенный элемент, предназначенный для использования в антенных решетках и оборудовании для конечных пользователей. Предложенная модель антенной решетки протестирована в экспериментальной широкополосной модели для массивных MIMO в помещении. В канале проведен анализ следующих системных параметров: корреляция каналов, профили задержек и средняя мощность. Кроме того, на основе измеренных данных канала выполняются моделирование на системном уровне и расчеты пропускной способности сети с множественными входами и множественными выходами, а также оценка производительности разработанных прототипированных антенных решеток. Для сравнительного анализа разработана тестовая матрица. Результаты показывают, что измененная геометрия антенной решетки превосходит однородную антенную решетку с точки зрения взаимной связи и пропускной способности канала the article examines the effect of the antenna array geometry on the performance of massive MIMO networks for indoor data transmission. Multi-user massive spatial signal encoding systems with multiple inputs and multiple outputs (systems of multiple MIMO antennas) will play a key role in future wireless communication networks. While spatial channel separation is a fundamental advantage of this encoding method, high channel correlation can significantly limit its capabilities and data transmission quality. The paper examines the effect of channel correlation on a prototyped MIMO network model in order to determine the geometry of the antenna array, which reduces the interconnection and correlation of channels. A highly efficient directional broadband single antenna element has been developed for antenna arrays and user equipment. The developed lattice geometry has been tested in an experimental broadband model for massive indoor MIMO. The following system parameters were analyzed in the channel: channel correlation, delay profiles and average power. In addition, based on the measured channel data, system-level modeling and calculations of network bandwidth with multiple inputs and multiple outputs are performed, as well as performance evaluation of the developed prototyped antenna arrays. A test matrix has been developed for comparative analysis. The results show that the modified geometry of the antenna array is superior to a homogeneous antenna array in terms of interconnection and channel capacity
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Ma, Yan, Jian-Zhang Pan, Shi-Ping Zhao, Qi Lou, Ying Zhu, and Qun Fang. "Microdroplet chain array for cell migration assays." Lab on a Chip 16, no. 24 (2016): 4658–65. http://dx.doi.org/10.1039/c6lc00823b.
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We developed a miniaturized and massive parallel microfluidic platform for multiple cell migration assays combining the traditional membrane-based cell migration technique and the droplet-based microfluidic technique.
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Druzhinina, N. S., and I. M. Daudov. "Analysis of the massive MIMO technology." Journal of Physics: Conference Series 2061, no. 1 (2021): 012094. http://dx.doi.org/10.1088/1742-6596/2061/1/012094.
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Abstract The article discusses the features of the Massive MIMO technology, the structure of the antenna array, as well as the advantages and example of using the massive MIMO system. The use of Massive MIMO opens up new opportunities and makes a significant contribution to achieving the stated requirements for the further evolution of LTE and 5G.
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Zheng, Wang, Xiaofei Zhang, Yunfei Wang, Mengjie Zhou, and Qihui Wu. "Extended Coprime Array Configuration Generating Large-Scale Antenna Co-Array in Massive MIMO System." IEEE Transactions on Vehicular Technology 68, no. 8 (2019): 7841–53. http://dx.doi.org/10.1109/tvt.2019.2925528.
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Kim, Tae-yun, and Suk-seung Hwang. "Cascade AOA Estimation Algorithm Based on Flexible Massive Antenna Array." Sensors 20, no. 23 (2020): 6797. http://dx.doi.org/10.3390/s20236797.
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The Angle-of-Arrival (AOA) has a variety of applications in civilian and military wireless communication fields. Due to the rapid development of the location-based service (LBS) industry, the importance of the AOA estimation technique has increased. Although a large antenna array is necessary to estimate accurate AOA information of many signals, the computational complexity of conventional AOA estimation algorithms, such as Multiple Signal Classification (MUSIC), is dramatically increased. In this paper, we propose a cascade AOA estimation algorithm employing CAPON and Beamspace MUSIC, based on a flexible (on/off) antenna array. First, this approach roughly finds AOA groups, including several signal AOAs using CAPON, by applying some of the antenna elements. Then, it estimates each signal AOA in the estimated AOA groups using Beamspace MUSIC by applying the full size of the antenna array. In addition to extremely low computational complexity, the proposed algorithm also has similar estimation performance to that of MUSIC. In particular, the proposed cascade AOA estimation algorithm is highly efficient when employing a massive antenna array. Representative computer simulation examples are provided to illustrate the AOA estimation performance of the proposed technique.
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JHANG, Wei, Shiaw-Wu CHEN, and Ann-Chen CHANG. "Efficient Hybrid DOA Estimation for Massive Uniform Linear Array." IEICE Transactions on Fundamentals of Electronics, Communications and Computer Sciences E102.A, no. 5 (2019): 721–24. http://dx.doi.org/10.1587/transfun.e102.a.721.
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Wang, Jun, and Dejun Mu. "FDD LTE Performance Simulation Based on Massive Antenna Array." Wireless Communications and Mobile Computing 2022 (July 4, 2022): 1–8. http://dx.doi.org/10.1155/2022/9945908.
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There are two methodologies to realize 3D MIMO for FDD LTE, MU-MIMO-based virtual beam (VB), and four-cell soft-split cell (SSC), which beamforms four logical cells in one physical sector, and this paper is aimed at figuring out which brings more performance between VB and SSC. In the first place, brief introduction for the mechanism of VB and SSC are presented. Subsequently, detailed systematic simulations based on WINNER II are carried out based on different traffic models (low load, medium load, and high load) and user distribution is also considered. For accurate evaluation on the performance gain of VB and SSC, 4T4R solution is also simulated as the benchmark, which is widely deployed to improve the capacity of FDD LTE by operators. Based on the simulation of results of the subsequent KPIs, cell throughput, average cell throughput, average UE throughput, and average layer number, VB and SSC effectively increase single-cell capacity and user experience in high load scenario compared with 4T3S solution and VB can bring more gain.
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JHANG, Wei, Shiaw-Wu CHEN, and Ann-Chen CHANG. "Computationally Efficient DOA Estimation for Massive Uniform Linear Array." IEICE Transactions on Fundamentals of Electronics, Communications and Computer Sciences E103.A, no. 1 (2020): 361–65. http://dx.doi.org/10.1587/transfun.2019eal2107.
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JHANG, Wei, Shiaw-Wu CHEN, and Ann-Chen CHANG. "Efficient Hybrid DOA Estimation for Massive Uniform Rectangular Array." IEICE Transactions on Fundamentals of Electronics, Communications and Computer Sciences E103.A, no. 6 (2020): 836–40. http://dx.doi.org/10.1587/transfun.2019eal2172.
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Sousa de Sena, Arthur, Daniel Benevides da Costa, Zhiguo Ding, Pedro H. J. Nardelli, Ugo Silva Dias, and Constantinos B. Papadias. "Massive MIMO-NOMA Networks With Successive Sub-Array Activation." IEEE Transactions on Wireless Communications 19, no. 3 (2020): 1622–35. http://dx.doi.org/10.1109/twc.2019.2955647.
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Zhang, Jian, Xiaojing Huang, Val Dyadyuk, and Y. Guo. "Massive hybrid antenna array for millimeter-wave cellular communications." IEEE Wireless Communications 22, no. 1 (2015): 79–87. http://dx.doi.org/10.1109/mwc.2015.7054722.
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Ribeiro, Lucas N., André L. F. Almeida, Josef A. Nossek, and João César M. Mota. "Low‐Complexity separable beamformers for massive antenna array systems." IET Signal Processing 13, no. 4 (2019): 434–42. http://dx.doi.org/10.1049/iet-spr.2018.5115.
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Liu, Peiqin, Yue Li, and Zhijun Zhang. "Multiple Fan-Beam Antenna Array for Massive MIMO Applications." Journal of Communications and Information Networks 3, no. 1 (2018): 38–42. http://dx.doi.org/10.1007/s41650-018-0003-8.
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Alemaishat, Saraereh, Khan, Affes, Li, and Lee. "An Efficient Precoding Scheme for Millimeter-Wave Massive MIMO Systems." Electronics 8, no. 9 (2019): 927. http://dx.doi.org/10.3390/electronics8090927.
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Aiming at the problem of high computational complexity due to a large number of antennas deployed in mmWave massive multiple-input multiple-output (MIMO) communication systems, this paper proposes an efficient algorithm for optimizing beam control vectors with low computational complexity based on codebooks for millimeter-wave massive MIMO systems with split sub-arrays hybrid beamforming architecture. A bidirectional method is adopted on the beam control vector of each antenna sub-array both at the transmitter and receiver, which utilizes the idea of interference alignment (IA) and alternating optimization. The simulation results show that the proposed algorithm has low computational complexity, fast convergence, and improved spectral efficiency as compared with the state-of-the-art algorithms.
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Bazuhair, Basem, and Omar Aldayel. "Fast Antenna Array Calibration Using One External Receiver." Sensors 23, no. 22 (2023): 9026. http://dx.doi.org/10.3390/s23229026.
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In multiple array communication or radar systems, waveform diversity can be utilized for beampattern design. However, one of the critical issues for such systems is the presence of mutual coupling, which degrades the beampattern design’s quality. We address the calibration of the mutual coupling of transmit arrays by developing a new matrix-inversion-free algorithm that requires only a single antenna receiver. It has a very low computational complexity for accelerating the mutual coupling calibration compared to previous methods; therefore, it can be utilized for large array systems such as massive multiple-input–single-output (MISO) systems. The key idea here revolves around utilizing fast Fourier transform (FFT). This approach simplifies matrix calculations and reduces the number of multiplications required to compute the inverse of FFT. Moreover, the algorithm is applicable for high-power active radar calibration, since it incorporates a constant modulus training sequence. The application of the algorithm in MISO systems, including massive MISO, offers the potential for calibrating mutual coupling. It enables the precise measurement and compensation of mutual coupling effects, improving the signal quality and system performance in areas such as radars, mobile communications and more. We evaluated the proposed algorithm under various scenarios, compared it with the ground truth and showed that it achieves excellent performance with few computations.
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Saha, Anindya, Anandmayee Tej, Hong-Li Liu, et al. "Direct Observational Evidence of Multi-epoch Massive Star Formation in G24.47+0.49." Astrophysical Journal Letters 970, no. 2 (2024): L40. http://dx.doi.org/10.3847/2041-8213/ad6144.
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Abstract Using new continuum and molecular line data from the Atacama Large Millimeter/submillimeter Array Three-millimeter Observations of Massive Star-forming Regions (ATOMS) survey and archival Very Large Array, 4.86 GHz data, we present direct observational evidence of hierarchical triggering relating three epochs of massive star formation in a ringlike H ii region, G24.47+0.49. We find from radio flux analysis that it is excited by a massive star(s) of spectral type O8.5V–O8V from the first epoch of star formation. The swept-up ionized ring structure shows evidence of secondary collapse, and within this ring, a burst of massive star formation is observed in different evolutionary phases, which constitutes the second epoch. ATOMS spectral line (e.g., HCO+(1–0)) observations reveal an outer concentric molecular gas ring expanding at a velocity of ∼9 km s−1, constituting the direct and unambiguous detection of an expanding molecular ring. It harbors twelve dense molecular cores with surface mass density greater than 0.05 g cm−2, a threshold typical of massive star formation. Half of them are found to be subvirial and thus in gravitational collapse making them the third epoch of potential massive star-forming sites.
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Chen, Yiwen, Qijuan Jie, Yiqiao Zhang, et al. "Two Rapid Power Iterative DOA Estimators for UAV Emitter Using Massive/Ultra-Massive Receive Array." Drones 7, no. 6 (2023): 361. http://dx.doi.org/10.3390/drones7060361.
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To provide rapid direction finding (DF) for unmanned aerial vehicle (UAV) emitters in future wireless networks, a low-complexity direction of arrival (DOA) estimation architecture for massive multiple-input multiple-output (MIMO) receiver arrays is constructed. In this paper, we propose two strategies to address the extremely high complexity caused by eigenvalue decomposition of the received signal covariance matrix. Firstly, a rapid power iterative rotational invariance (RPI-RI) method is proposed, which adopts the signal subspace generated by power iteration to obtain the final direction estimation through rotational invariance between subarrays. RPI-RI causes a significant complexity reduction at the cost of a substantial performance loss. In order to further reduce the complexity and provide good directional measurement results, the rapid power iterative polynomial rooting (RPI-PR) method is proposed, which utilizes the noise subspace combined with the polynomial solution method to obtain the optimal direction estimation. In addition, the influence of initial vector selection on convergence in the power iteration is analyzed, especially when the initial vector is orthogonal to the incident wave. Simulation results show that the two proposed methods outperform the conventional DOA estimation methods in terms of computational complexity. In particular, the RPI-PR method achieves more than two orders of magnitude lower complexity than conventional methods and achieves performance close to the Cramér–Rao Lower Bound (CRLB). Moreover, it is verified that the initial vector and the relative error have a significant impact on the performance with respect to the computational complexity.
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Um, Dugan. "Massive Sensor Array Fault Tolerance: Tolerance Mechanism and Fault Injection for Validation." Journal of Robotics 2010 (2010): 1–8. http://dx.doi.org/10.1155/2010/745834.
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As today's machines become increasingly complex in order to handle intricate tasks, the number of sensors must increase for intelligent operations. Given the large number of sensors, detecting, isolating, and then tolerating faulty sensors is especially important. In this paper, we propose fault tolerance architecture suitable for a massive sensor array often found in highly advanced systems such as autonomous robots. One example is the sensitive skin, a type of massive sensor array. The objective of the sensitive skin is autonomous guidance of machines in unknown environments, requiring elongated operations in a remote site. The entirety of such a system needs to be able to work remotely without human attendance for an extended period of time. To that end, we propose a fault-tolerant architecture whereby component and analytical redundancies are integrated cohesively for effective failure tolerance of a massive array type sensor or sensor system. In addition, we discuss the evaluation results of the proposed tolerance scheme by means of fault injection and validation analysis as a measure of system reliability and performance.
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Khan, A., and J. S. Roy. "Thinned Smart Antenna of a Semi-circular Dipole Array for Massive MIMO Systems." Advanced Electromagnetics 12, no. 4 (2023): 17–25. http://dx.doi.org/10.7716/aem.v12i4.2303.
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Massive MIMO (multiple-input multiple-output) is a multi-user MIMO technology that can provide high-speed multimedia services in 5G wireless networks using sub-6 GHz and millimeter wave bands. The massive MIMO (MMIMO) installs array antennas in the base stations, using hundreds of transceivers with other RF modules. One of the drawbacks of the MMIMO system is its huge power consumption, and the beamforming network with RF modules for a large number of antennas is the main contributor to the power consumption. In this paper, a novel beamforming method is proposed for the low power consumption of an MMIMO system. The proposed thinned smart antenna (TSA) of a semi-circular array produces a secure beam toward the user’s terminal with reduced interference. By thinning the antenna array, some of the antenna elements are kept off, resulting in less power consumption, while the array pattern remains the same as a fully populated array with a reduced side lobe level (SLL). The sub-6 GHz band of 5 GHz is used for the design of thinned array antennas. The genetic algorithm (GA) is used to determine the array sequence in thinning, and the adaptive signal processing algorithms least mean square (LMS), recursive least square (RLS), and sample matrix inversion (SMI) are used for the beamforming of the TSA, and the corresponding algorithms are GA-LMS, GA-RLS, and GA-SMI. The power saving of 40% to 55% is achieved using TSA. The maximum SLL reductions of 13 dB, 12 dB, and 14 dB are achieved for TSA using GA-LMS, GA-RLS, and GA-SMI algorithms, respectively.
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Londhe, Gayatri D., and Vaibhav S. Hendre. "An Effective Kalman Based Hybrid Beamforming for Millimeter Wave Massive MIMO System by Using 2D Overlapped Partially Connected Sub-Array Structure." Traitement du Signal 39, no. 6 (2022): 2141–47. http://dx.doi.org/10.18280/ts.390627.
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In 5G mobile communication networks, millimeter-wave (mmWave) technology plays a key role. To deal with the problem of path loss that happens in the mmWave band, competent beamforming employing a large antenna array is required. Fully digital beamforming approaches currently require separate radio frequency chains (RF chains) for each antenna, which adds to the computational complexity and hardware expense. In a multi-user environment, fully digital beamforming suffers from a larger antenna array layout, whereas analog beamforming solutions are prone to numerous performance concerns. Hybrid beamforming, on the other hand, offers a promising solution for multi-user mmWave communication. This work proposes a two-dimensional overlapping partially connected (2D-OPC) sub-array structure to reduce the antenna structure's hardware complexity and cost. The suggested technique comprises several sub-arrays that are overlapped in 2D space in the form of a Uniform Planar Array (UPA). The suggested scheme's performance is assessed using Kalman-based hybrid beamforming, which exhibits a considerable increase in spectral efficiency when compared to existing hybrid beamforming techniques. The suggested technique, which uses Kalman based hybrid beamforming and 2D-OPC provides 3.14% and 4.96% improvement over the MMSE hybrid beamforming and ZF pre-coding technique respectively.
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Lee, Minju. "Massive and dusty Hα emitters in protocluster revealed by ALMA and JVLA". Proceedings of the International Astronomical Union 11, S319 (2015): 96. http://dx.doi.org/10.1017/s1743921315010236.
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AbstractWe investigate the physical properties of Hα emitters (HAEs) associated to the protocluster 4C23.56 at z ~ 2.5 using continuum observations at submm (270 GHz) and radio (3 GHz) frequencies with Atacama Large Mm/submm Array (ALMA) and K. Jansky Very Large Array (JVLA). For more details see Lee et al. (in prep).
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Gunawan, D. Y. A. Setia, M. Curé, S. Kanaan, et al. "ALMA Observation of Mass Loss from Massive Stars." Proceedings of the International Astronomical Union 12, S329 (2016): 403–4. http://dx.doi.org/10.1017/s1743921317002861.
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AbstractWe present a pilot study of using the Atacama Large Millimeter/sub-millimeter Array (ALMA) continuum observations to constrain the density structure in the intermediate wind zone of massive stars, in which the wind is extremely sensitive to clumping.
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Varsha, Varsha. "Analog Beamforming for Massive MIMO in 5G Wireless Communication Systems." International Scientific Journal of Engineering and Management 04, no. 06 (2025): 1–9. https://doi.org/10.55041/isjem04629.
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Abstract Analog beamforming has emerged as a promising solution for power- and cost-efficient wireless communication in massive MIMO (Multiple Input Multiple Output) systems, especially within 5G and millimetre-wave (mm Wave) domains. This paper presents a comprehensive study of analog beamforming architecture, its integration in MIMO systems, key performance metrics, simulation results, and a critical comparison with digital and hybrid beamforming methods. The paper explores system-level modelling, performance evaluation, and practical challenges including beam squint, hardware impairments, and phase quantization. Simulation results demonstrate how varying the number of antenna elements and steering angles influence array gain, beamwidth, and sidelobe levels, validating the practicality of analog beamforming for specific wireless applications. Index Terms Analog beamforming, Massive MIMO, mm Wave, 5G, phase shifter, spectral Efficiency, beam squint, SNR, antenna arrays, signal processing.
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Danuor, Patrick, and Emmanuel Ampoma Affum. "Performance Analysis of Spatially Correlated Cylindrical Antenna Array for 3D Massive MIMO." International Journal of Wireless & Mobile Networks 12, no. 6 (2020): 1–10. http://dx.doi.org/10.5121/ijwmn.2020.12601.
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The spectral efficiency of three-dimensional (3D) massive MIMO is impaired due to the spatial correlation (SC) between closed-spaced elements of antenna arrays (AAs). This paper investigates the impacts of arbitrary Q-power variations of the Power Cosine distribution for a precise characterization of the SC. This is done by presenting mathematical expressions characterizing the SC of cylindrical antenna array (CAA) regarding Student's -t, Von Mises and Cosine distributions, for the direction of arrival (DoA) of the electromagnetic waves impinging on the receiving antenna. Unlike the Student's -t and Von Mises distribution, our outcome recorded huge mismatch between theoretical and simulation correlation coefficients for arbitrary Q-power values above ten (10) which also reduced the downlink channel capacity. The practical relevance is that even though higher Q-power values are the key parameters for system performance, meticulous selection of arbitrary Q-power values above ten (10) is essential to minimize errors regarding channel modelling.
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Albadarn, Saleh M. "The Effect of Pilot Reuse Factor on Massive MIMO Spectral Efficiency." Engineering, Technology & Applied Science Research 13, no. 3 (2023): 10703–7. http://dx.doi.org/10.48084/etasr.5605.
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Due to their much increased spatial resolution and array gain, large-scale antenna arrays have the potential to significantly enhance the spectral efficiency of wireless systems. Recent research in the area of massive Multiple-Input Multiple-Output (MIMO) antennas shows that user channels are enhanced as the number of antennas at the Base Stations (BSs) rises, allowing achieving high signal improvement with minimum inter-user interference. The combined effects of the pilot reuse factor and the BS number of antennas on average overall spectral efficiency in huge MIMO antennas will be investigated. To examine the SE of these receivers, several channel estimators will be utilized, including LMMSE, ZF, and MR methods. Theoretically, BS could offer a substantially higher average total SE if it had more antennas.
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Cesaroni, R., L. Moscadelli, R. Neri, et al. "Radio outburst from a massive (proto)star." Astronomy & Astrophysics 612 (April 2018): A103. http://dx.doi.org/10.1051/0004-6361/201732238.
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Context. Recent observations of the massive young stellar object S255 NIRS 3 have revealed a large increase in both methanol maser flux density and IR emission, which have been interpreted as the result of an accretion outburst, possibly due to instabilities in a circumstellar disk. This indicates that this type of accretion event could be common in young/forming early-type stars and in their lower mass siblings, and supports the idea that accretion onto the star may occur in a non-continuous way. Aims. As accretion and ejection are believed to be tightly associated phenomena, we wanted to confirm the accretion interpretation of the outburst in S255 NIRS 3 by detecting the corresponding burst of the associated thermal jet. Methods. We monitored the radio continuum emission from S255 NIRS 3 at four bands using the Karl G. Jansky Very Large Array. The millimetre continuum emission was also observed with both the Northern Extended Millimeter Array of IRAM and the Atacama Large Millimeter/Submillimeter Array. Results. We have detected an exponential increase in the radio flux density from 6 to 45 GHz starting right after July 10, 2016, namely ~13 months after the estimated onset of the IR outburst. This is the first ever detection of a radio burst associated with an IR accretion outburst from a young stellar object. The flux density at all observed centimetre bands can be reproduced with a simple expanding jet model. At millimetre wavelengths we infer a marginal flux increase with respect to the literature values and we show this is due to free–free emission from the radio jet. Conclusions. Our model fits indicate a significant increase in the jet opening angle and ionized mass loss rate with time. For the first time, we can estimate the ionization fraction in the jet and conclude that this must be low (<14%), lending strong support to the idea that the neutral component is dominant in thermal jets. Our findings strongly suggest that recurrent accretion + ejection episodes may be the main route to the formation of massive stars.