Capacity Of Multiple-input Multiple-output Systems Research Articles

Adaptive Transmission Based on MIMO Mode Switching Over Malaga Turbulence Channel With Pointing Error

In this paper, we propose a dynamic adaptive multiple input multiple output (MIMO) free space optical (FSO) system with spatial mode switching. Based on the channel conditions, the proposed system can select different MIMO transmission modes: diversity, multiplexing or hybrid mode that yields the maximum average channel capacity while satisfying the reliable average bit error rate (BER). Considering the combined effects of path loss, pointing error and atmospheric turbulence-induced fading modeled by Malaga distribution, we derive the closed-form expressions of average channel capacity and average BER of MIMO system for each transmission mode. From adaptive system performance evaluated results, we establish the signal-to-noise ratio (SNR) threshold look-up table (LUT) in different scenarios to select the optimal transmission mode. The extensive numerical results demonstrate that the proposed adaptive system has a significant improvement in average channel capacity compared with each stand-alone mode system. Finally, Monte Carlo simulation is also provided to verify the correctness of the proposed adaptive scheme and conclusions.

Ergodic Capacity of IRS-Assisted MIMO Systems With Correlation and Practical Phase-Shift Modeling

We focus on the maximization of the exact ergodic capacity (EC) of a point-to-point multiple-input multiple-output (MIMO) system assisted by an intelligent reflecting surface (IRS). In addition, we account for the effects of correlated Rayleigh fading and the intertwinement between the amplitude and the phase shift of the reflecting coefficient of each IRS element, which are usually both neglected despite their presence in practice. Random matrix theory tools allow to derive the probability density function (PDF) of the cascaded channel in closed form, and subsequently, the EC, which depend only on the large-scale statistics and the phase shifts. Notably, we optimize the EC with respect to the phase shifts with low overhead, i.e., once per several coherence intervals instead of the burden of frequent necessary optimization required by expressions being dependent on instantaneous channel information. Monte-Carlo (MC) simulations verify the analytical results and demonstrate the insightful interplay among the key parameters and their impact on the EC.

Evaluation of Development Level and Technical Contribution of Recent Technologies Adopted to Meet the Challenges of 5G Wireless Cellular Networks

The evolution of the global wireless market is accompanied by an increased need in terms of speed and number of users, lower latency, better coverage, better spectral efficiency and quality of service, etc. To meet these needs, 5G has recently been introduced as an effective solution which targets, via the large scale deployment of symmetric antennas, a wide variety of sectors such as energy, health, media, industry, transport and especially wireless cellular networks which are among the most important pillars of modern societies. Multiple Input, Multiple Output (MIMO) systems, which have been extended to “Massive MIMO” mode and which consist of increasing the number of radiating elements involved in the transmission and reception of the radio link, are a very promising solution for improving the spectral efficiency of wireless communication systems (WCSs). Motivated by the aforementioned developments, the present paper investigates the increased capacity of MIMO systems to improve transmission in WCSs using 5G. It carefully focuses on the evaluation of the development level and technical contribution of MIMO systems and millimeter wave (mmWave) bands in 5G wireless cellular networks (WCNs) and gives important recommendations.

Performance assessment of orthogonal space‐time block codes in Nakagami‐m/inverse Gaussian fading MIMO channels

This paper evaluates the performance of multiple-input multiple-output systems with orthogonal space-time block code transmit diversity technique experiencing over G composite fading channels. Particularly, closed form expressions for ergodic capacity, average symbol error rate and outage probability are presented in high SNR regime. The ergodic capacity of multiple-input multiple-output systems with orthogonal space-time block code is also measured in low signal-to noise ratio regime. Other essential statistical properties such as variance and probability density function of capacity are also explored for comprehensive analysis. Compared to the exact expressions, the derived analytical formulations are found to be involved with considerably less mathematical exercise and provide additional insights into the implications of model parameters on system performance. The accuracy of G distribution in approximating Nakagami- m / lognormal over several realistic scenario are examined and simultaneously the efficiency of distribution is compared with that of Nakagami- m / Gamma distribution. The obtained analytical expressions are corroborated using Monte-Carlo simulations where it is observed that the approximated results remain notably tight in asymptotically high signal-to noise ratio regime.

Atmospheric turbulence mitigation using spatial mode multiplexing and modified pulse position modulation in hybrid RF/FSO orbital-angular-momentum multiplexed based on MIMO wireless communications system

Abstract In this paper, the capacity of a free-space optical (FSO) communication over radio frequency (RF) could potentially be increased by the simultaneous transmission of multiple orbital angular momentum (OAM) based on spatial mode multiplexing (SMM) as an additional effective degree of freedom (EDOF) and quadrature amplitude modulation (QAM). This paper describes using hybrid RF/FSO-OAM based on multiple-input multiple-output (MIMO)/SMM using M-ary modified pulse position modulation (MPPM) and spatial PPM (SPPM) for potentially enhancing capacity in wireless communication systems. We present an analytical system design concerning OAM multiplexing and MIMO/SMM processing in free space communications channel under atmospheric turbulence (AT). Here, we assume a new architecture that closes the gap in speeds between millimeter-wave (mm-wave) wireless and optical links. In this study, we highlight recent advances in the use of OAM multiplexing for high-capacity FSO and mm-wave communications. We have developed the MPPM in FSO communication over RF using the source Gaussian model and SMM by proposing a new version of hybrid SPPM and MPPM. The novelty approach presents performance enhancement of the acquisition, pointing, tracking position and AT mitigation of link. We propose to use SMM combined with OAM-QAM based MIMO communications system to mitigate both weak and strong turbulence distortions. Simulation results show that the capacity of OAM-based MIMO system outperforms the capacity of the conventional MIMO system when the propagation distance is larger than a specific threshold. The use of transmitter lenses could enhance the OAM beams with a larger mode spacing (MS) of 2 (OAM l = + 1 , l = + 3 , l = + 5 , l = + 7 transmitted) shows a lower power penalty (PP) when the inter-channel crosstalk overwhelms a larger lateral displacement of about 2 mm. Using the lenses at the transmitter to focus OAM beams could reduce power loss and PP in OAM-based FSO links and that this improvement might be more significant for higher-order OAM beams and provide high power-efficiency. With a larger of the transmitter and receiver 8 cm, 10 cm aperture size respectively, the system with mode spacing of 2 (OAM l = + 1 , l = + 3 , l = + 5 , l = + 7 transmitted) and mode spacing of 3 (OAM l = + 1 , l = + 4 , l = + 7 , l = + 10 transmitted) of OAM beams based on MIMO should fulfill lower-power penalty of 2.2 dB, 3.4 dB, as respectively and could enhance system robustness under angular error but degrade tolerance of lateral displacement. The proposed system provides an excellent signal-to-noise ratio (SNR) for the capacity in the regime of strong atmospheric turbulence. In this way, the maximization of FSO communication and RF wide, the data capacity enhancement, and it is considered a massive solution in the bandwidth provision for future access networks. This work could be beneficial to the practical implementation of OAM-MIMO/SMM multiplexed RF/FSO links.

MIMO Channel Reconstruction from Lower Dimensional Multiple Antenna Measurements

A method for reconstructing multiple-input multiple-output (MIMO) channel correlation matrices from lower dimensional channel measurements is presented. Exploiting the symmetry of correlation matrix structure enables reproducing higher dimensional MIMO channel matrices from available lower order measurements. This leads to practically important applications allowing prediction of higher dimensional MIMO system capacity. In particular, we study Kronecker-type MIMO channels suitable for reconstructing full channel matrices from partial information about transmit-receive fading in spatial and polarimetric domains and analyze validity conditions for such models. One of the important channel conditions is Doppler frequency related to non-stationarity in the environment. We present simulations of cluster-type scattering model using $$2\times 2$$ MIMO channel correlation matrices to predict performance of $$2\times 4$$ MIMO system including recovery of angular power spectrum. An example of dual circular polarized $$2\times 4$$ MIMO land mobile satellite measurements in 2.5 GHz frequency band illustrates applicability of the method to reconstruct spatial and polarimetric channel correlation matrices for estimating ergodic channel capacity from single-antenna or uni-polarized measurements.

Capacity Analysis of Orbital Angular Momentum Wireless Channels

The orbital angular momentum (OAM) technology is able to provide a new degree of freedom for wireless communication systems. The energy of OAM waves is focused within a circle region surrounding the beam axis, which makes the propagation gains inside and outside the circle region different. However, in the existing literature, the propagation gains inside and outside the circle region are assumed to be the same. Therefore, the impact of OAM waves’ spatial energy distribution on the capacity of OAM wireless communication systems has not been fully investigated. Considering the spatial energy distribution characteristics of OAM waves, in this paper, an OAM wireless channel model is proposed. Based on the proposed OAM wireless channel model, the capacity of OAM-based multiple-input multiple-output (MIMO) communication system is analytically derived. Simulation results indicate that the capacity of OAM-based MIMO system outperforms the capacity of conventional MIMO system when the transmission distance is larger than a specific threshold. Our results provide a basic capacity model for OAM-based MIMO communication systems.

3-D Geometrical Model for Multi-Polarized MIMO Systems

Multiple-input multiple-output (MIMO) systems capacity is highly influenced by the correlation between antennas, and the high correlation will result in a low capacity. Therefore, the multi-polarized antennas have been implemented in MIMO systems to reduce the correlation between antennas and realize the space efficiency. To better understand the performance of multi-polarized MIMO systems, polarization channel modeling is of great importance. In this paper, we establish a 3-D geometrical model for multi-polarized MIMO systems. Antenna cross-polar isolation (XPI), channel cross-polarization discrimination (XPD) and antenna tilt parameters have been considered in our model. The correlation and capacity of multi-polarized MIMO systems are analyzed, and we find that the XPI, XPD, and antenna tilt have an effect on the correlation and capacity simultaneously, which cannot be analyzed separately. Also, we compare our model with the existing measurements for validation, which shows that the proposed model is well in agreement with the measurements. Finally, we compare the performance of multi-polarized MIMO systems with the traditional uni-polarized MIMO systems, which shows that the performance of multi-polarized MIMO systems have robustness to the communication environment, and multi-polarized MIMO systems outperform uni-polarized MIMO systems in many communication scenarios.

Capacity Analysis and Optimization of Satellite MIMO System

Multiple-Input Multiple-Output (MIMO) technology is widely applied in terrestrial wireless communication system, which greatly increases the system capacity. Satellite communication system has many advantages such as wide coverage and strong flexibility. Therefore, how to make a better use of MIMO technology in satellite communication system has become a research hotspot in recent years. The purpose of this paper is to analysis the relationship between satellite MIMO system capacity and parameters of terrestrial antenna such as angle and distance. The parameters of terrestrial antenna were derived and calculated to keep a higher capacity for satellite MIMO system. Numerical analysis of system capacity performance before and after optimization was obtained, which proved the correctness of the theory proposed in this paper.

Shannon information capacity of time reversal wideband multiple-input multiple-output system based on correlated statistical channels**Project supported by the National Natural Science Foundation of China (Grant Nos. 61331007, 61361166008, and 61401065) and the Specialized Research Fund for the Doctoral Program of Higher Education of China (Grant No. 20120185130001).

Utilizing channel reciprocity, time reversal (TR) technique increases the signal-to-noise ratio (SNR) at the receiver with very low transmitter complexity in complex multipath environment. Present research works about TR multiple-input multiple-output (MIMO) communication all focus on the system implementation and network building. The aim of this work is to analyze the influence of antenna coupling on the capacity of wideband TR MIMO system, which is a realistic question in designing a practical communication system. It turns out that antenna coupling stabilizes the capacity in a small variation range with statistical wideband channel response. Meanwhile, antenna coupling only causes a slight detriment to the channel capacity in a wideband TR MIMO system. Comparatively, uncorrelated stochastic channels without coupling exhibit a wider range of random capacity distribution which greatly depends on the statistical channel. The conclusions drawn from information difference entropy theory provide a guideline for designing better high-performance wideband TR MIMO communication systems.

On the Capacity of MIMO Weibull-Gamma Fading Channels in Low SNR Regime

We present capacity analysis for multiple-input multiple-output (MIMO) system under a low signal-to-noise ratio (SNR) regime. We have selected a composite fading channel that considers Weibull fading for multipath and gamma fading for shadowing. We have presented the analysis in a detailed form for three different techniques, namely, spatial multiplexing (SM) with optimal detection, SM with minimum mean square error (MMSE) detection, and orthogonal space-time block codes (OSTBC). Because capacity analysis at arbitrary signal-to-noise (SNR) is stringent, a low SNR regime is considered to achieve a positive rate and wideband slope. The improvement is the result of minimizing energy per information bit (Eb). For the first time, closed-form expressions are evaluated for the capacity of MIMO systems at low SNR under WG fading channels which facilitate the performance comparison for proposed techniques.

On Capacity of Downlink Underwater Wireless Optical MIMO Systems With Random Sea Surface

In this letter, we focus on the relationship among channel capacity, signal-to-noise ratio (SNR), water types, wind speed, and characteristics of transmiter/receiver array such as inter-spacing and link range for downlink underwater wireless optical communications (UWOC) multiple-input multiple-output (MIMO) systems. Numerical results suggest that more turbid water, larger link range, and larger inter-spacing may reduce the channel capacity, and meanwhile more turbid water and larger link range can weaken the effects of random slopes and inter-spacing at the expense of larger SNR to balance the channel capacity.

Application of a Galaxy-Based Search Algorithm to MIMO System Capacity Optimization

The objective of this paper is to use the recently proposed galaxy-based search optimization algorithm to enhance the capacity of a multiple input multiple output (MIMO) system with rectangular arrays at both communication ends (transmitter and receiver). This new optimization tool has been recently introduced and is a metaheuristic technique inspired by the dynamics of galactic arm spirals. It is characterized by its robustness, immunity to local optima trapping, relative fast convergence and ease of implementation. The idea is to extend the results obtained for the one-dimensional array geometry to the two-dimensional case. The purpose is to find out which array geometrical dimensions produce the highest capacity value. Compared to the linear array case, promising capacity values are found using the two-dimensional arrays which suggests their deployment in future MIMO communication systems.

Rainfall Effect on the Performance of Millimeter-Wave MIMO Systems

This paper considers the rainfall effect on the capacities and achievable rates of millimeter-wave (mmW) multiple-input multiple-output (MIMO) systems. We first develop a new channel model for point-to-point mmW MIMO systems to characterize the rainfall effect. This rain propagation model is derived based on stochastic properties of signal propagation in a general random scattering medium. Under this model, we evaluate the channel capacity of the mmW MIMO system at various rain rates and show that rainfall does not always have a negative impact on the system performance, provided that accurate instantaneous channel state information (CSI) is available at both the transmitter and receiver. We also show that a transmit strategy of statistical water-filling (SWF) allows the mmW MIMO system to have near-optimal performance.

Mimo Channel and Performance Analysis using OFDM System for Reduced Bit Error Rate

Multiple-input Multiple-output (MIMO) systems use multiple antennas at the transmitter and receiver end, are a key technology to meet the growing demand for high data rate wireless systems. The aim of this thesis is to investigate MIMO system capacity with the aim of achieving optimum Bit Error Rate (BER) while increasing the system capacity using multicarrier delay diversity modulation (MDDM), proposed for fifth generation systems. In principle, the capacity of MIMO system can increase linearly with the number of antennas. Multiple antennas at the transmitter and receiver provide diversity in a fading environment. Furthermore, the research work in this thesis consists of different investigations of the basic principle of MIMO, Multiple-input Single-output (MISO) and Single-input Single-output (SISO) wireless communication systems with Space Time Codes (STC). A MISO systems and MIMO systems are schematized using MDDM which incorporated with Orthogonal Frequency Division Multiplexing (OFDM). OFDM is chosen over a single-carrier solution due to lower complexity of equalizers for high delay spread channels or high data rates. The design is implemented with binary Phase Shift Keying (BPSK) and simulated using MATLAB, which is examined in associated Additive White Gaussian Noise (AWGN) channel. The receiver-design is included with the maximal ratio combiner (MRC) receiving technique with perfect wisdom of channel state information (CSI). The theoretical performance is derived for AWGN channels and compared with the simulated results as well as compared between each system to another.

A low computational complexity V-BLAST/STBC detection mechanism in MIMO system

Abstract The idea of multiple antenna arrays has evolved into multiple-input multiple-output (MIMO) system, which provides transmit and receive diversities. It increases robustness of the effect of multipath fading in wireless channels, besides yielding higher capacity, spectral efficiency and better bit error rate (BER) performance. The spatial diversity gain is obtained by transmitting or receiving multiple copies of a signal through different antennas to combat fading and improves the system BER performance. However, the computational complexity of MIMO system is inevitably increased. Space-time coding (STC) technique such as Alamouti’s space-time block code (STBC) that combines coding, modulation and signal processing has been used to achieve spatial diversity. Vertical Bell Laboratories Layered Space-Time (V-BLAST) uses antenna arrays at both the transmitter and receiver to achieve spatial multiplexing gain. Independent data streams that share both frequency bands and time slots are transmitted from multiple antennas and jointly detected at the receiver. The theoretical capacity of V-BLAST increases linearly with the number of antennas in rich scattering environments. It's well-known that maximization of spatial diversity gain leads to degradation of spatial multiplexing gain or vice versa. In order to achieve spatial multiplexing and diversity gains simultaneously, the V-BLAST/STBC scheme has been introduced. This hybrid scheme increases MIMO system capacity and maintains reliable BER performance at the same time. However, both V-BLAST and STBC layers, in this hybid scheme, assume each other as an interferer. Thus, the symbols must be decoded with a suitable detection mechanism. In this paper, a new low complexity detection mechanism for V-BLAST/STBC scheme based on QR decomposition, denoted as low complexity QR (LC-QR) decomposition, is presented. The performance of the proposed LC-QR decomposition detection mechanism in V-BLAST/STBC transceiver scheme is compared with other detection mechanisms such as ZF, MMSE and QR decomposition. It is shown that the BER performance in V-BLAST/STBC scheme is better than V-BLAST scheme while its system capacity is higher than orthogonal STBC scheme when the LC-QR decomposition detection mechanism is exploited. Moreover, the computational complexity of proposed LC-QR decomposition mechanism is significantly lower than other abovementioned detection mechanisms.

Capacity of generalised network multiple‐input–multiple‐output systems with multicell cooperation

In network multiple-input–multiple-output (MIMO) systems, cooperative base stations (BSs) and mobile terminals (MTs) are in general at different geographic locations. Correspondingly, the channel gains with respect to different BSs and/or MTs may obey different distributions, which resulted from, different pathlosses, different strength of line-of-sight (LOS) components and so on. Furthermore, future wireless communication systems are expected to be equipped with multiple antennas for transmission/receiving. In these multiantenna systems, signals received by the antennas of one BS from one MT may be correlated. Against the above-mentioned scenarios, in this contribution, the authors study the capacity of the generalised uplink network MIMO systems with multicell cooperation (MCoP), when propagation pathlosses, fast Rician fading with various LOS components and spatial correlation are simultaneously considered. Specifically, the theory of operator-valued free probability is introduced to derive the approximate eigenvalue distribution (AED) of the correlation matrix of the equivalent channels. Based on the AED, the approximate capacity of uplink network MIMO systems is then studied. Furthermore, a range of special cases are analysed by specialise the authors model and modifying their results. Finally, both numerical and simulation results are provided for characterising the capacity of network MIMO systems with MCoP.

Channel Capacity and BER Performance Analysis of MIMO System with Linear Receiver in Nakagami Channel

Multiple input mult iple output (MIMO) is one of the key technology to accomplish the goal of the future wireless broadband commun ication. This paper deals with the bit error rate (BER) and capacity performance of the Vert ical Bell laboratories layered space-time (VBA LST) M IMO systems with a linear receiver such as minimu m mean-square error (MMSE) and zero forcing (ZF) over Nakagami-m channel. Both the BER and the capacity of M IMO systems have been analyzed for different modulat ion techniques and also with various configurations of MIMO systems. We have also analyzed the VBLAST MIM O system perfo rmance in a higher SNR region.

Multiple-Input Multiple-Output System Capacity: Antenna and Propagation Aspects

This tutorial aims to review some of the system and measurement work done at Qualcomm related to multiple-input-multiple-output (MIMO) systems around the 2000–2005 timeframe. During the same period, Qualcomm was actively involved in the development of the MIMO technology adopted by IEEE 802.11n. In this tutorial, we show the spectral efficiency and physical-layer (PHY) data rates that can be reached with Qualcomm's MIMO technology using practical 8 × 8 and 16 × 16 antenna arrays mounted on a laptop. The results are based on measurements performed in Qualcomm's New England offices. We show that very high data rates can be achieved for an office deployment. The results were compared with the simulated results obtained with IEEE802.11n MIMO channel models, and a good match was observed with channel model E.

SER analysis based on different modulation techniques in MIMO system

Physical limitations of the wireless medium create a technical challenge for reliable wireless communication. Moreover, the need for high-speed wireless Internet has led to the demand for technologies delivering higher capacities and link reliability than achieved by current systems. Multiple -input multiple-output (MIMO) based communication systems are capable accomplishing these objectives. Multiple input multiple output (MIMO) systems take advantage of spatial diversity obtained through the spatially separated antennas in a dense multipath scattering environment. Spatial diversity can increase the gain diversity consequently increase the reliability of the wireless link. Theoretical studies indicate that the capacity of MIMO systems grows linearly with the number of transmit antennas used. In this paper Space Time Coding techniques is covered which leads to much improvement in Symbol Error Rate within the same spectrum and bandwidth. Also a comparison is made between different modulation techniques.