Multiple-input And Multiple-output Systems Research Articles

Enhancing gain and isolation of a quad-element MIMO antenna array design for 5G sub-6 GHz applications assisted with characteristic mode analysis

This paper presents a novel quad-element array with multiple inputs and multiple outputs (MIMO) designed for 5th generation sub-6 GHz applications. The MIMO system achieves a wide impedance bandwidth, high gain, and high isolation among its components, representing significant advancements in sub-6 GHz antenna applications. The single element, an elliptical resonator with a circular slot, is fed by a 50 Ω microstrip feedline, achieves a broad characteristic bandwidth from 3.7 to 5.7 GHz with a resonant frequency of 4.33 GHz and a gain of 1.81 dBi. Characteristic Mode Analysis (CMA) was employed to elucidate the evolution phases of this design. The quad-element MIMO antenna array maintains a compact size and broadband characteristics by arranging mirrored elements on the same ground plane. Implemented on a cost-effective FR-4 substrate measuring 44 × 44 × 1.6 mm3, the recommended MIMO antenna array, enhanced with a partial ground plane and due to the introduction of a vertical strip, a high isolation of − 38.53 dB is achieved between MIMO components along with a realized gain of 3.01 dBi and a radiation efficiency of 71% in the 5G sub-6 GHz band. Noteworthy properties include high isolation, diversity gain (DG), and envelope correlation coefficient (ECC), verifying the appropriateness of the suggested MIMO scheme for 5G transmission and reception in sub-6 GHz applications.

Enhanced MIMO CSI Estimation Using ACCPM with Limited Feedback.

Multiple Input and Multiple Output (MIMO) is a promising technology to enable spatial multiplexing and improve throughput in wireless communication networks. To obtain the full benefits of MIMO systems, the Channel State Information (CSI) should be acquired correctly at the transmitter side for optimal beamforming design. The analytical centre-cutting plane method (ACCPM) has shown to be an appealing way to obtain the CSI at the transmitter side. This paper adopts ACCPM to learn down-link CSI in both single-user and multi-user scenarios. In particular, during the learning phase, it uses the null space beamforming vector of the estimated CSI to reduce the power usage, which approaches zero when the learned CSI approaches the optimal solution. Simulation results show our proposed method converges and outperforms previous studies. The effectiveness of the proposed method was corroborated by applying it to the scattering channel and winner II channel models.

Decentralized QFT Controller Design Based on the Equivalent Subsystems Method

Since the 1970s various decentralized control methodologies have been developed to deal with the challenge of controlling complex and/or spatially distributed systems with multiple inputs and multiple outputs (MIMO), e.g., chemical plants, power systems, water systems, etc. In general, the use of distributed information and control structures requires the synthesis of control laws in a constrained (decentralized) information structure. The article presents a novel frequency domain robust decentralized controller design method that is appropriate for uncertain dynamic MIMO systems with equal numbers of input and output variables, which consist of interconnected physical subsystems and are given as a set of square transfer function matrices. The main framework of the proposed method provides the Equivalent Subsystems Method (ESM), whereby the overall closed-loop system under a decentralized controller is stable if, and only if, all the individual closed-loop equivalent subsystems are stable. By generating equivalent subsystems for all transfer matrices, which describe the uncertain MIMO system, the individual uncertain equivalent subsystems are obtained as sets of respective frequency responses. Such representation allows the application of the QFT (quantitative feedback theory) approach to independently design local single-input single-output (SISO) robust controllers which constitute the resulting decentralized controller implemented in real subsystems. The designed controller ensures robust stability of the overall closed-loop system and the required performance as specified by the standard QFT performance specification types in both the equivalent subsystems and the overall closed-loop system. Compared to the existing method and references therein, the proposed method reduces the conservatism of the robust stability conditions and enables the exploitation of the benefits by the SISO QFT approach in the independent design of the robust decentralized controller. The developed design procedure is verified and illustrated in a case study on the robust decentralized level controller design of the quadruple tank process.

Observer normal form design for the nonlinear MIMO systems using coupled auxiliary dynamics

This paper presents a transformation of a class of nonlinear multiple-input and multiple-output (MIMO) dynamical systems into a class of extended nonlinear normal forms. The extended normal forms are compatible with the widely used high-gain observer, which enables the estimation of the system’s states. It is realized by using a series of transformations which are performed by means of the so-called dynamics extension method, which explicitly supplies a set of auxiliary dynamics and a change of coordinates. Many researchers have focused their efforts on transforming nonlinear dynamical systems into normal forms of nonlinear observers. However, few of proposed transformations have been specifically developed for MIMO systems using an extended dynamics transformation. The main objective of this work is to fill this gap and provide a class of nonlinear dynamical systems that support the extended dynamics method, which can lead to a better understanding of their structures. Additionally, the results are highlighted by studying a class of nonlinear systems that describe the Dengue fever infection status of both human and mosquito populations. Finally, the effectiveness of the proposed high-gain observer is verified through a numerical example.

Performance Analysis of Spatially Multiplexed MIMO System

Abstract: In SISO (single input and single output) system, refers to have only one input and one output. Here only one antenna is used at receiver and transmitter side. SISO are relatively simple to design and implement. They are of low cost and used in wide range of applications. However, SISO systems are poor in performance and deliver low data rate. So we’ll prefer MIMO (multiple input and multiple output) over SISO as it gives better spectral efficiency, improved reliability and good coverage. In MIMO we use multiple antennas at transmitter and receiver side which is known as Spatial Multiplexing(SM) which enhances the data rate. In the paper the performance of spatial combining MIMO system is analysed. Matlab used for simulation.

Joint-Transceiver Equalization Technique over a 1.4 km Multi-Mode Fiber Using Optical MIMO Technique in IM/DD Systems

In optical fiber communication, recent advances in multiple-input and multiple-output (MIMO) systems using space-division multiplexing have helped achieve higher spectral efficiency and data rates. Propagating higher-order modulation formats over MIMO systems further strengthens the capacity of the transmission link. In the optical-MIMO system, the dispersion impairments originating from a 1.4 km long multi-mode fiber (MMF) are mitigated using the proposed joint-transceiver equalization technique. A numerical convex optimization algorithm is used to compute and optimize the pre- and post-equalization (PPE) coefficients jointly restricted by cost and power budgets. The potential of the proposed joint-PPE technique is tested on an MMF link, which is severely degraded by dispersion compared to a single-mode fiber channel. From the experimental results, the average optical received power gain necessary to reach 10−4 bit-error rate is improved by nearly 2.5 dB using the joint-PPE compared to the post-equalization only based on the minimum mean-squared error principle. When the efficiency of the conventional zero-forcing (ZF) principle-based PPE and the joint-PPE is compared, the joint-PPE scheme outperforms the ZF-PPE by approximately 1.5 dB. The enhancement in the transmission quality is observed with experimentally measured eye diagrams using the joint-PPE scheme. Under the analyzed scenarios, computer simulation also confirms the hypothesis, which establishes the effectiveness of the proposed joint-transceiver equalization over the conventional ZF-PPE scheme. Moreover, the simulated performance benefits of the joint-PPE are evaluated using the singular value decomposition (SVD) technique. Improvement of ≈3.86 dB in the average optical received power gain required to reach 10−4 bit-error rate is witnessed with the PAM-4 format. Overall, the joint-transceiver equalization technique is proven to be beneficial in optical MIMO systems.

Analysis of increasing channel capacity of MIMO communication system by vortex electromagnetic wave

Multiple-input and multiple-output (MIMO) communication technology which depends on multipath reflection can bring more efficient use of spectrum and higher channel capacity without expanding the bandwidth. This technology has been widely used in 5G communication system these days. However, under some circumstances which are lack of multipath reflection, the performance of traditional MIMO communication is not satisfying. Therefore, some researchers have pointed out that the technology of vortex electromagnetic wave can improve this situation efficiently. This article has done some researches on analyzing the channel capacity in traditional MIMO system and the MIMO system with vortex electromagnetic wave. Firstly, the spatial channel geometry model has been established with a 4-antenna transmit array and a 25-antenna receiving array in a three-dimensional rectangular coordinate system. In order to obtain the total channel capacity, the Los channel fading matrix should be calculated through calculating the distances between each two transmit and receiving antennas. After that the water filling algorithm has been used to decide the power allocation method to each subchannel to get the maximum capacity of the system. Finally, the relationship between maximum channel capacities and the signal-noise ratio (SNR) can be plotted as a line chart. The experiment first compared the capacities with and without the vortex electromagnetic wave of MIMO communication system under different SNR and found that the adding of vortex electromagnetic wave can increase the capacity efficiently. Next the influences of some variables to the channel capacity include the height of transmit antenna array, the distance between each two nearby transmit antenna elements and the variable Q which can change the phase complexity of wavefront have been discussed.

Ultra Wideband (UWB) Multiple Input and Multiple Output (MIMO) Antenna Design : A Review

Since the Federal Communication Commission (FCC) issued a license for the 3.1 – 10.6 GHz frequency spectrum for unlicensed radio applications, many papers have been published regarding ultrawideband (UWB) antenna design. The issue of UWB antenna design is determining how to create an antenna with a wide bandwidth, capable of rejecting communication systems that coexist with UWB bands, and capable of designing UWB antennas for multiple input multiple output (MIMO) communication system applications. This study examines the design of UWB antennas with monopole and slot types based on evaluations published over the last two decades. The discussion began with UWB and MIMO systems and then moved on to the configuration of monopole and slot UWB antennas. UWB antenna layout with notched bands and the several types of notched bands available. Finally, two port and quad-port MIMO antenna configuration is examined. To further understand UWB antenna design, numerous UWB antenna configurations are simulated. The outcomes of this review can be utilized as preliminary reading material for researchers looking into UWB antennas.

Performance Analysis of MIMO-mQAM System with Pointing Errors and Beam Spreading in Underwater Málaga Turbulence Channel

Both the long-term beam spreading caused by ocean turbulence and the pointing errors induced by the jitter of transmitters and receivers degrade the performance of underwater wireless optical communication (UWOC) links. To effectively alleviate their effects, an in-depth study was carried out over the Málaga turbulence channel with pointing errors and beam spreading in multiple-input and multiple-output (MIMO) UWOC. First, we analyzed the long-term beam spreading and the received light power for the finite receiving aperture in the presence of pointing error displacements. Based on this, the relationship between beam spreading, pointing errors, and signal power was established. Second, the approximate expressions of the average bit error rate (BER) and the communication outage probability were derived theoretically for this MIMO system using maximal-ratio combining (MRC) diversity. Third, the effects of the pointing errors on the coding and the diversity gains were explored for the MIMO links. Finally, using the observed ocean data from the Global Ocean Argo gridded dataset, we numerically verified the combined effects of ocean turbulence strength, beam spreading, and pointing errors on the average BER and outage probability of this system. These results also proved that adjusting the size of the receiving aperture or the order of the multiple quadrature amplitude modulation (mQAM) could effectively mitigate their effects.

Efficient Channel Estimation for RIS-Aided MIMO Communications With Unitary Approximate Message Passing

Reconfigurable intelligent surface (RIS) is very promising for wireless networks to achieve high energy efficiency, extended coverage, improved capacity, massive connectivity, etc. To unleash the full potentials of RIS-aided communications, acquiring accurate channel state information is crucial, which however is very challenging. For RIS-aided multiple-input and multiple-output (MIMO) communications, the existing channel estimation methods have computational complexity growing rapidly with the number of RIS units <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$N$ </tex-math></inline-formula> (e.g., in the order of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$N^{2}$ </tex-math></inline-formula> or <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$N^{3}$ </tex-math></inline-formula> ) and/or have special requirements on the matrices involved (e.g., the matrices need to be sparse for algorithm convergence to achieve satisfactory performance), which hinder their applications. In this work, instead of using the conventional signal model in the literature, we derive a new signal model obtained through proper vectorization and reduction operations. Then, leveraging the unitary approximate message passing (UAMP), we develop a more efficient channel estimator that has complexity linear with <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$N$ </tex-math></inline-formula> and does not have special requirements on the relevant matrices, thanks to the robustness of UAMP. These facilitate the applications of the proposed algorithm to a general RIS-aided MIMO system with a larger <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$N$ </tex-math></inline-formula> . Moreover, extensive numerical results show that the proposed estimator delivers much better performance and/or requires significantly less number of training symbols, thereby leading to notable reductions in both training overhead and latency.

Ergodic capacity of correlated multiple-input–multiple-output channel with impact of transmitter impairments

Abstract The ergodic capacity of the ideal multiple-input and multiple-output (MIMO) channel grows unboundedly at the-high SNRs because of the assumption that the transceivers used in the system do not affect the signal that passes through them. In reality, the transceivers used in the MIMO system suffer from many impairments such as phase noise, quantization noise, and non-linear amplifier. These physical transceivers will affect the signal that passes through them. Thus, the influence of the physical transceivers cannot be neglected in the analysis of the MIMO channel capacity. Additionally, another essential thing that must be considered when analyzing the MIMO channel capacity is the correlation between the channel elements. Therefore, to get results close to the behavior of the practical results for the capacity of any MIMO system, this article proposes an algorithm that simulates the capacity of the correlated MIMO channel that suffers from Rayleigh flat fading with the presence of the physical transmitter. This work is done by considering that the effect of the physical transmitter at the nth transmitting antenna is a Gaussian distortion noise with a zero mean and variance proportional to the power of the signal transmitted through the same antenna. The simulation process for the proposed technique is manipulated by MATLAB software with 10,000 realizations of the channel. Also, the transmitter impairment thresholds employ in the simulation are 0.08 and 0.175. The simulation results showed that the channel capacity with the physical transmitter stopped growing at a specific limit in the very high-SNRs, and it decreased at the medium and high SNRs when the correlation coefficient increased.

Validation of Parallel Distributed Adaptive Signal Processing (PDASP) Framework through Processing-Inefficient Low-Cost Platforms

The computational complexity of the multiple-input and multiple-output (MIMO) based least square algorithm is very high and it cannot be run on processing-inefficient low-cost platforms. To overcome complexity-related problems, a parallel distributed adaptive signal processing (PDASP) architecture is proposed, which is a distributed framework used to efficiently run the adaptive filtering algorithms having high computational cost. In this paper, a communication load-balancing procedure is introduced to validate the PDASP architecture using low-cost wireless sensor nodes. The PDASP architecture with the implementation of a multiple-input multiple-output (MIMO) based Recursive Least Square (RLS) algorithm is deployed on the processing-inefficient low-cost wireless sensor nodes to validate the performance of the PDASP architecture in terms of computational cost, processing time, and memory utilization. Furthermore, the processing time and memory utilization provided by the PDASP architecture are compared with sequentially operated RLS-based MIMO channel estimator on 2×2, 3×3, and 4×4 MIMO communication systems. The measurement results show that the sequentially operated MIMO RLS algorithm based on 3×3 and 4×4 MIMO communication systems is unable to work on a single unit; however, these MIMO systems can efficiently be run on the PDASP architecture with reduced memory utilization and processing time.

Joint Pre- and Post-Equalization with Higher-Order Modulation Formats in SDM-Based Optical MIMO Systems

The multiple-input and multiple-output (MIMO) technology is a promising area of research to cope up with the demands of higher data rates and capacity. In the optical communication domain, the combination of space-division multiplexing (SDM) with higher-order modulation (HOM) formats over an optical MIMO system actively addresses these challenges. By allowing multi-level signaling with limited increment in the transmitter’s complexity, a jointly designed pre- and post-equalization (PPE) for an optical MIMO system with a multi-mode fiber (MMF) link is proposed. Cost-effectiveness of the system is incorporated by utilizing intensity modulation/direct detection (IM/DD) with HOM formats such as pulse-amplitude modulation (PAM) schemes. With the aid of a numerical optimization algorithm, the proposed joint-PPE filter coefficients are optimized with respect to the MMF channel and the transmit power constraint. In contrast to existing research on the single-mode fiber (SMF) based optical systems, the effectiveness of the proposed joint-PPE filter is analyzed on an MMF link, which is considerably degraded by the modal dispersion. In the analyzed experimental scenario, the proposed joint-PPE scheme confirms to be beneficial as compared to the post-equalization only (PE-only) in terms of bit-error rate (BER) performance. Furthermore, the required average received optical power to reach a BER 10−4 by the joint-PPE scheme is improved by 2 dB with comparison to the minimum mean-squared error (MMSE) PE-only.

Dual band 8 × 8 MIMO antenna system for DCS 1800 and 5G mobile applications

SummaryA dual‐band (1.6–1.9 GHz and 3.3–3.9 GHz) eight‐antenna multiple‐input and multiple‐output (MIMO) system is proposed in this paper. The basic structure of the proposed antenna element consists of microstrip lines, cylindrically shaped shorting, and a rectangular‐shaped defected ground structure (DGS). This structure is responsible for the production of a self‐ isolated MIMO system. The performance of the MIMO antenna system is investigated by the detailed analysis of S‐parameters, Envelope Correlation Coefficient (ECC), Mean Effective Gain (MEG), Total Active Reflection Coefficient (TARC), and Channel Capacity (CC). The proposed MIMO antenna system offers a good S‐parameter, radiation pattern, and satisfactory isolation characteristics. The MIMO antenna system is fabricated on lossy high dielectric ( = 4.3) FR4 substrate (loss tangent 0.02). The measured results are in good agreement with simulated one. The proposed antenna focuses on the 3.3–3.9 GHz frequency band, which covers bands 3.3–3.6 GHz (center frequency, 3.45 GHz) or 3.4–3.8 GHz (center frequency, 3.6 GHz) under the band below 6 GHz for 5G operation.

Performance Evaluation of Two System Models for a MIMO System to Hover the Bicopter Unmanned Aerial Vehicle

Building unmanned aerial vehicle (UAV) control system models are highly challenging due to multiple inputs and multiple outputs (MIMO). Not only does it have various angular position outputs such as roll, yaw, and pitch, but also flight control has more than one input; for instance, a bicopter has dual rotors. More rotors have more complex model. The hover condition has a zero resultant force which can be utilized to design a system model. On the other hand, an attractive identification system method is applied to develop the design. This research aims to evaluate the performance of two MIMO design on bicopter between methods based on the hover principle and identification technique. Experimental validation by employing bicopter simulator is an excellent strategy to fulfil this purpose. The results of the investigation of the experiment showed that the identification model was more accurate than the hover design, particularly regarding the overshot phenomenon and error. In addition, the hover principle tended to build ideal model because it did not include the dynamic, uncertainty and nonlinear conditions in aeroplane control design. Although the identification system was complicated because it previously needed to measure the input and output values, it performed closer to the actual experiment. It performed more satisfactory overshoot values compared with the experimental validation than the hover model by 1°, 3°, and 8° in roll, pitch, and yaw angles, respectively.

Power Amplifier Linearization in the Presence of Crosstalk and Measurement Noise in MIMO System

The crosstalk and transceiver noise is an intrinsic part of the multiple-input and multiple-output (MIMO) System, becoming more prominent in low-cost systems. Moreover, the power amplifiers (PAs) cause nonlinearity, propagating to the complete chain. The conventional techniques do not provide the joint method for crosstalk, transceiver noise, and PA nonlinearity. This results in the performance limitation of the digital predistortion (DPD). Hence we propose a wavelet multiscale principal component analysis (PCA) based technique to deal with such problems (crosstalk, transceiver noise, and system nonlinearities). It is reported using measurement and simulation that numerical stability issue is no longer an issue when wavelet multiscale PCA-based DPD is applied. The effect of wavelet multiscale PCA on bit-resolution of DPD is shown to be better than established DPD Models. On a field-programmable gate array and direct conversion transceiver-based platform, the performance of the proposed model is analyzed using PA. Parameters like normalized mean square error have shown an improvement of around 23 dB and adjacent channel error power ratio has shown an improvement of around 22 dBc for a ZX60-V63+ power amplifier using LTE-OFDM signals.

Deep graph neural network optimized with fertile field algorithm based detection model for uplink multiuser massive multiple‐input and multiple‐output system

AbstractThe core requirements are generated for sixth generation (6G) wireless communication with low‐latency and ultra‐high speeds to increase the count of ultra scale intelligent factors, like smart cars, mobile root users. The advancement of 6G communication can lead the interference exploitation. To manage the exploitation of uplink multiuser massive (UMM), the multiple‐input and multiple‐output (MIMO) is very difficult to detect the mechanisms, particularly, quadrature amplitude modulation (QAM) signals. To overcome these issues, a novel deep graph neural network optimized with fertile field algorithm based detection model (DGNNO‐FFA) is proposed in this article for uplink multiuser massive MIMO System. The proposed DGNNO‐FFA approach minimizes the channel estimation errors under low signal to noise ratio (SNR) with better bit error rate (BER). Finally, the proposed DGNNO‐FFA approach attains 11.02%, 12.22%, and 25.27% lower BER value, 14.55%, 18.66%, and 29.49% higher energy efficiency, 15.59%, 19.06%, and 29.59% lower NMSE, and 15.59%, 19.06%, and 29.59% lower computational complexity compared with other existing approaches, like deep neural network based semi definite relaxation (DNN‐SDR), QR based zero forcing algorithms (QR‐ZF), and QAM based 2‐dimensional double successive projection model (QAM‐2D‐DSP).

Study on precoding optimization algorithms in massive MIMO system with multi-antenna users

The paper studies the multi-user precoding problem as a non-convex optimization problem for wireless multiple inputs and multiple outputs (MIMO) systems. In our work, we approximate the target Spectral Efficiency function with a novel computationally simpler function. Then, we reduce the precoding problem to an unconstrained optimization task using a special differential projection method and solve it by the Quasi-Newton L-BFGS iterative procedure to achieve gains in capacity. We are testing the proposed approach in several scenarios generated using Quadriga-open-source software for generating realistic radio channel impulse response. Our method shows monotonic improvement over heuristic methods with reasonable computation time. The proposed L-BFGS optimization scheme is novel in this area and shows a significant advantage over the standard approaches. The proposed method has simple implementation and can be a good reference for other heuristic algorithms in this field.

Interlacing Properties of System-Poles, System-Zeros, and Spectral-Zeros in MIMO Systems

Single-input single-output (SISO), systems with zeros interlacing poles (ZIP) have been extensively studied in the literature and have received interest widely. However, the ZIP property for multiple-input and multiple-output (MIMO), systems has not been pursued sufficiently. In this article, we pursue the ZIP property for MIMO systems and link this to strict passivity. For the class of systems that admit a symmetric state-space realization, which for the SISO case is equivalent to ZIP, we obtain sufficient conditions under which MIMO systems too have ZIP. We also present new results in the context of “spectral-zero” of a system, a notion that plays a key role in many optimal control and estimation problems. We formulate conditions under which the spectral-zeros of a MIMO system are real, and further conditions that guarantee that the system-zeros, spectral-zeros, and the system-poles are all interlaced for MIMO systems.

16-ports indoor base station MIMO array for sub-6 GHz 5G applications

A typical 5G multiple-input and multiple-output (MIMO) system must combine a high number of antennas at both the transmitter and receiver to realize spatial multiplexing capability. In this paper, a wideband 16- element indoor base station (BS) antenna array that can cover 3.3–6.0 GHz is proposed for 5G applications. A π-shaped monopole antenna is designed to cover the Lower band (LTE bands 42/43–N77–N78), the intermediate band (N79), and the higher band (LTE 46). The antenna elements are arranged in a limited space printed on a substrate take the Hexakaidecagon Polygon shape. As the antenna elements are arranged with good isolation, achieving good polarization diversity. The proposed BS array is simulated, fabricated, and tested. The typical results, S-parameters, antenna efficiency, and radiation patterns are investigated. Moreover, to validate the MIMO performances, a very low envelope correlation coefficient (ECC) below 0.02, high antenna efficiency of about 82–93.2% are achieved. The calculated ergodic channel capacity of the 16 × 16 MIMO system reached up to 85 bps/Hz. The proposed antenna array was compared to some other 5G MIMO indoor base station antennas.