MIMO Antenna Array Impact on Channel Capacity for a Realistic Macro-Cellular Urban Environment

In MIMO systems the antenna array configuration in the BS and MS has a large influence on the available channel capacity. In this paper, we first introduce a new Frequency Selective (FS) MIMO framework for macro-cells in a realistic urban environment. The MIMO channel is built over a previously developed directional channel model, which considers the terrain and clutter information in the cluster, line-of-sight and link loss calculations. Next, MIMO configuration characteristics are investigated in order to maximize capacity, mainly the number of antennas, inter-antenna spacing and SNR impact. Channel and capacity simulation results are presented for the city of Lisbon, Portugal, using different antenna configurations. Two power allocations schemes are considered, uniform distribution and FS spatial water-filling. The results suggest optimized MIMO configurations, considering the antenna array size limitations, specially at the MS side.

Adaptive switching between multiple-input multiple-output (MIMO) transmission strategies like diversity and spatial multiplexing is a flexible approach to respond to channel variations. It is desirable to obtain accurate estimates of the switching points between these transmission schemes to realize the capacity gains made possible by adaptive switching. In this paper, it is shown that the accuracy of switching point estimates for switching between statistical beamforming and spatial multiplexing is improved by taking into account the effects of mutual coupling between antenna array elements. The impact of mutual coupling on the ergodic capacities of these two transmission strategies is analyzed, by deriving expressions for the same. Adaptive switching between combinations of transmission strategies and antenna array configurations (using reconfigurable antenna arrays) is shown to produce maximum capacity gains. Expressions for the switching points between transmission strategies and/or antenna configurations, including mutual coupling effects, are derived and used to explore the influence of mutual coupling on the estimates. Finally, measurements taken from reconfigurable rectangular patch antenna arrays are used to validate the analytical results.

The design and analysis of a four-port Multiple Input Multiple Output (MIMO) configuration antenna have been discussed in this work. Firstly, a single-element antenna has been designed using a monopole feedline, split ring resonators (SRR), and Defective Ground Structures (DGS). The SRRs were designed using rectangular and circular configurations and analysed their characteristics. The DGS is used to enhance the bandwidth of the proposed single-element antenna. Further four port MIMO configurations have been designed using four single-element antennas. To enhance the isolation, antennas are placed orthogonally to each other in MIMO configuration. The coupling between the monopole feedline and SRR plays a vital role in enhancing the impedance matching of the antenna configuration. The proposed MIMO antenna provides improved gain, high isolation, and compactness in size. The diversity performance matrices such as envelope correlation coefficient, diversity gain), Mean effective gain and total active reflection coefficient are <0.01, >9.95 dB, -1.0, and <-10 dB, respectively, which meets the performance criterion of the MIMO antenna. The designed four-port MIMO antennas can be used in sub-6 GHz (3.3 to 3.8 GHz) and fixed satellite television data services (10.7 to 14.5 GHz) applications.

SummaryIn this paper, the efficiency of various multiple‐input multiple‐output (MIMO) detectors was analyzed from the perspective of highly correlated channels, where MIMO systems have a lack of performance, besides in some cases, an increasing complexity. Considering this hard but a useful scenario, various MIMO detection schemes were accurately evaluated concerning complexity and bit error rate performance. Specifically, successive interference cancellation, lattice reduction, and the combination of them were associated with conventional linear MIMO detection techniques. To demonstrate effectiveness, a wide range of the number of antennas and modulation formats have been considered aiming to verify the potential of such MIMO detection techniques according to their performance‐complexity trade‐off. We have also studied the correlation effect when both transmit and receiver sides are equipped with uniform linear array and uniform planar array antenna configurations. The performance of different detectors is carefully compared when both antenna array configurations are deployed considering a different number of antennas and modulation order, especially under near‐massive MIMO condition. We have also discussed the relationship between the array factor and the bit error rate performance of both antenna array structures.

Fifth Generation (5G) fosters the integration of several technologies for achieving the requirements of rapid and reliable communications. Multiple Input Multiple Output (MIMO) is one such technology implemented in communication systems with the aim of delivering better services to users. Machine Learning (ML) technologies are also being used alongside MIMO since they can aid with the selection of the most appropriate MIMO configuration based on antenna, data, and channel parameters. These parameters can be further used as input features to the models for obtaining the best data rate and throughput. In this paper, three different MIMO configurations, 2 × 2, 3 × 3, and 4 × 4 MIMO using directional and omnidirectional antennas have been simulated. Power propagation from each antenna, MIMO power, channel capacity, data rate, and throughput have been used as response variables. The data obtained from these simulations are used to train regression models for prediction of new data. Frankfurt city is used as scenario in this simulation and the models are analyzed based on the root mean squared error (RMSE) values obtained. The results demonstrate that the interactions linear regression, fine tree and medium tree models provide the lowest RMSE values when predicting the variables for different MIMO configurations using directional and omnidirectional antenna.

In this paper, ultra-massive multiple-input multiple-output (MIMO) channel measurements at 5.3 GHz are conducted, including different antenna array configurations and different measurement scenarios. The antenna array configurations include uniform linear array (ULA) and distributed uniform linear array (DULA). The measurement scenarios include single-user fixed-to-fixed (F2F), multi-user F2F, and single-user fixed-to-mobile (F2M) measurement scenarios. The statistical properties of ultra-massive MIMO channels are studied, including delay power spectral density (DPSD), space cross-correlation function (SCCF), angle cross-correlation function (ACCF), frequency correlation function (FCF), root mean square (RMS) delay spread (DS), RMS angle spread (AS), singular value spread (SVS), scalar product (SP), level crossing rate (LCR), average fading duration (AFD), Doppler power spectral density (PSD), etc. The specific ultra-massive MIMO channel characteristics are investigated and validated by channel measurements, including spatial non-stationarity, spherical wavefront behavior, channel hardening, and sparse properties in the angle domain. In addition, channel capacities are investigated. The channel measurement results will be a great importance for ultra-massive MIMO communication system deployments.

SummaryA compact circular fractal antenna element loaded with a central pentagonal slot is presented in this paper. This structure consists of a fourth iterative radiator fed by a partially tapered feed line and CPW defected ground plane. A superwide impedance bandwidth of 3.45–52.17 GHz (~175% fractional bandwidth) is achieved. Two multiple input multiple output (MIMO) configurations are also designed and analyzed by using this antenna element. For spatial and pattern diversity configurations, the impedance bandwidth of 3.45–52.2 and 3.1–52.2 GHz are achieved, respectively. The optimized footprints of antenna element, spatial diversity configuration, and pattern diversity configurations are 28 × 24, 28 × 53, and 45 × 48 mm2, respectively. The isolation for both MIMO configurations is more than 20 dB in maximum portion of the operating bandwidth. Desirable radiation and diversity performance characteristics are achieved for antenna element and MIMO configurations. The wide bandwidth, compact dimensions along with good radiation, and diversity performance characteristics make the proposed antenna configurations suitable for integration in superwideband wireless communication systems. A good agreement between the experimental and simulation results is observed.

In consequence of the high demand for high transmission data rates in the outdoor and indoor environment, an exploitation of multiple-input multiple output (MIMO) systems appears recently. The MIMO channel is obviously characterized by antenna configuration and propagation environment. The antenna configuration is responsible mainly for the antenna correlation effect which can be reduced by increasing antenna array spacing or by employing multi-polarized antenna arrays. In this paper, we assume that all scatterers are uncorrelated, independent and identically distributed (i.i.d). In addition we investigate the channel capacity of single, dual and triple polarized dipole antennas compared with omni-vertical and omni-horizontal antennas with various solid angles based on 2times2 and 3times3 MIMO systems. The results of simulations illustrate that a combination of angular and polarization diversities can be exploited to increase the transmission performance

In this paper, a novel low-complexity antenna-selection algorithm based on a constrained adaptive Markov chain Monte Carlo (CAMCMC) optimization method is proposed to approach the maximum capacity or minimum bit error rate (BER) of receive-antenna-selection multiple-input multiple-output (MIMO)-orthogonal frequency division multiplexing (OFDM) systems. We analyze the performance of the proposed system as the control parameters are varied and show that both the channel capacity and the system BER achieved by the proposed CAMCMC selection algorithm are close to the optimal results obtained by the exhaustive search (ES) method. We further demonstrate that this performance can be achieved with less than 1% of the computational complexity of the ES rule and is independent of the antenna-selection criteria, outage rate requirements, antenna array configuration, and channel frequency selectivity. Similar to the existing antenna-selection algorithms, both channel capacity and system BER improvements achieved by the proposed CAMCMC method are reduced as the channel frequency selectivity increases. Therefore, we conclude that, whether it is designed to maximize the channel capacity or minimize the system BER, the CAMCMC-optimization-method-based antenna-selection technique is appropriate for a MIMO-OFDM system with low frequency selectivity.

The need to achieve high data rates in modern telecommunication systems, such as 5G standard, motivates the study and development of large antenna and multiple-input multiple-output (MIMO) systems. This study introduces a large antenna-order design of MIMO quasi-orthogonal space-time block code (QO-STBC) system that achieves better signal-to-noise ratio (SNR) and bit-error ratio (BER) performances than the conventional QO-STBCs with the potential for massive MIMO (mMIMO) configurations. Although some earlier MIMO standards were built on orthogonal space-time block codes (O-STBCs), which are limited to two transmit antennas and data rates, the need for higher data rates motivates the exploration of higher antenna configurations using different QO-STBC schemes. The standard QO-STBC offers a higher number of antennas than the O-STBC with the full spatial rate. Unfortunately, also, the standard QO-STBCs are not able to achieve full diversity due to self-interference within their detection matrices; this diminishes the BER performance of the QO-STBC scheme. The detection also involves nonlinear processing, which further complicates the system. To solve these problems, we propose a linear processing design technique (which eliminates the system complexity) for constructing interference-free QO-STBCs and that also achieves full diversity using Hadamard modal matrices with the potential for mMIMO design. Since the modal matrices that orthogonalize QO-STBC are not sparse, our proposal also supports O-STBCs with a well-behaved peak-to-average power ratio (PAPR) and better BER. The results of the proposed QO-STBC outperform other full diversity techniques including Givens-rotation and the eigenvalue decomposition (EVD) techniques by 15 dB for both MIMO and multiple-input single-output (MISO) antenna configurations at 10 − 3 BER. The proposed interference-free QO-STBC is also implemented for 16 × N R and 32 × N R MIMO systems, where N R ≤ 2 . We demonstrate 8, 16 and 32 transmit antenna-enabled MIMO systems with the potential for mMIMO design applications with attractive BER and PAPR performance characteristics.

Motivated by the study of the optimization of the quality of service for multiple input multiple output (MIMO) technique in a wireless communication system. The capacity of MIMO channel in independent Rayleigh channels grows linearly as the number of antennas. However, some limitations on the MIMO capacity is due to the correlation between individual sub-channels of the matrix channel. In this paper, we investigate the MIMO channel capacity in correlated channels using a new correlation matrix model. After some mathematical recalls we derive the general upper bound on the MIMO channel capacity. We give the analytical results, which measure the effect of correlation on the MIMO capacity for a proposal model. Then, we use the correlation matrix approach to compute the capacity of MIMO with respect to signal-to-noise (snr) and then predict the numbers of antennas. By fixing the snr variable to a specific value, we extract informations on the optimal numbers of MIMO antennas. Finally, we have given the variation of the MIMO capacity in the limiting case of N rarr infin for our proposal model and the exponential correlation matrix model.

Problem statement: Multiple Input and Multiple Output (MIMO) system with Multihop relaying techhnique is significant and active areas of wireless communication. In a rich scattering environment MIMO antenna system provides better channel capacity and data rates than single antenna systems. To provide high throughput, reliable transmission and broad coverage, wireless relaying techniques are essential in a variety of applications. In a cellular environment a relay can be used to overcome shadowing effect due to obstacles and multihop relaying can improve the throughput for mobiles suffering from poor signal to interference, noise ratio at the edge of a cell and reduce cell size to increase spectral efficiency. Approach: This study analyzes average mutual information of the Ricean channel for single hop Multiple Input Multiple Output (MIMO) system for different antenna configuation and dependence of capacity on the Rice factor for cellular system. The asymptotic capacity of multiuser two-hop MIMO system with Regularization Block Diagonalization (RBD) precoding techniques for Indepenent Identically Distributed (IID) channal and realistic Mobile to Mobile fading channel model was examined. In this realistic model, Non-Line-Sight (NLOS) propagation conditions are assumed from source mobile station to mobile relay and also from mobile relay to destination station. A non regenerative Amplify and Forward (AF) relay is used to optimize the capacity between the source and destination and also the evaluation was made for multiuser multi-hop relay system with correlated fading channel model using RBD precoding matrix. Results: The simulation results for average mutual information of single hop MIMO relay system for different antenna configuration with ricean channel model, ergodic sum mutual information for two hop relay system with RBD precoding technique and mutual information results for multiuser multihop relay system with correlated channel model was presented. Conclusion/Recommendations: Cellular systems generally operated at a fairly low SINR which can be increased on each hop by adding relays. Multiuser two hop relay system with RBD precoding for realistic mobile to mobile fading channel model is simulated and compared with IID channel model. Multiuser Multi-hop relay with optimal precoding and RBD precoding technique results were analyzed for correlated fading channel and found that capacity offered by RBD precoding scheme is better than other relaying systems.

In Multiple-Input Multiple-Output (MIMO), there is multi-user interference because of the limited number of antennas at the Base Station (BS). Deploying more antenna elements at the BS to decrease the multi-user interference is a costly solution. Therefore, changing the configuration of antenna arrays at the BS is implemented as an alternative. In this paper, the impact of BS antenna array configurations on the performance of massive MIMO detection techniques is investigated where four different antenna array configurations are implemented at the BS: Uniform Linear Array (ULA), Uniform Rectangular Planar Array (URPA), Uniform Circular Array (UCA) and Uniform Circular Planar Array (UCPA). The performance of the massive MIMO system is based on the millimeter wave (mmWave) channel that depends on the array response vector of the BS antenna array configuration. To the best of our knowledge, this is the first paper to investigate the impact of antenna array configurations at the BS on the performance and the computational complexity of massive MIMO detection techniques. Numerical results show that the implementation of URPA at the BS with MMSE detection algorithm can achieve the best performance of BER=10−4 at SNR = 9dB. The deployment of the UCA at the BS with the successive over-relaxation (SOR), the Gauss-Seidel (GS), and the conjugate-gradient (CG) detection methods provides a performance of BER=10−4 at SNR = 12dB when the number of iterations equals eight. In the case of using the UCA at BS with the Richardson (RI) detection method, the number of iterations is required to be increased to achieve the same performance. To achieve BER=10−4, the detector based on the CG method has the lowest computational complexity while the RI method has the highest complexity.

Problem statement: Today's wireless technologies just won't get us to the hyper connectivity of uninterrupted access from any mobil e device with unlimited bandwidth at real-time speeds. This is due to the low data throughput and scarcity in spectrum. Approach: Under the condition of uncorrelated antenna elements, capacit y of the Multiple Input Multiple Output (MIMO) system can be increased linearly with the number of antennas. But in practice correlation among the antenna elements exists and it can reduce the chann el capacity. The effect of correlation can be reduced by using spatial diversity techniques. Results: The capacity of various MIMO configurations were analyzed and simulated. The effect of capacity of MIMO system due to correlation was presented with and without Eigen value distribution of the ch annel. The spatial correlation of dipole array and rectangular micro strip patch arrays were simulated with respect to various element spacing. Conclusion/Recommendations: The simulation results showed that, the capacity o f MIMO system without spatial correlation was higher than with co rrelation effect. By comparing, the rectangular micro strip patch array has low correlation than di pole array and provides high capacity which can be utilized for high data rate applications.

This paper clarifies the influence of the antenna configuration on the achievable throughput in a real indoor propagation environment employing 2-by-2 single-user (SU) multiple-input multiple-output (MIMO) in the Long Term Evolution (LTE)-Advanced uplink with single carrier-based radio access. For four antenna configurations, the achievable throughput performance with adaptive modulation and coding (AMC) and hybrid automatic repeat request (HARQ) is evaluated under line-of-sight (LOS) and non-LOS (NLOS) conditions using the implemented LTE-Advanced transceiver. Experimental results show that under LOS conditions, Rank-2 MIMO spatial multiplexing is invaluable in improving the achievable throughput because the restriction on the mobile station (MS) transmission power in an indoor environment is not so severe due to a small cell size compared to that in a field environment. The results also show that when a cross-polarized antenna configuration is employed, the location probability for achieving throughput greater than 200 Mbps is approximately 95%. We confirm that under NLOS conditions, Rank-1 closed-loop transmit diversity with precoding is effective in enhancing the coverage in an indoor environment. Furthermore, we clarify that high throughput performance is obtained irrespective of the MS or base station (BS) antenna separation since the appropriate precoding vector (PV) is selected for each antenna configuration.