Performance Of Multiple-input Multiple-output Systems Research Articles

Performance analysis comparison of transmit antenna selection with maximal ratio combining and orthogonal space time block codes in equicorrelated Rayleigh fading multiple input multiple output channels

In this study, bit error rate (BER) performance of multiple input multiple output (MIMO) systems employing transmit antenna selection with maximal ratio combining (TAS/MRC) and orthogonal space time block codes (OSTBC) is analysed and compared. Analysis has been done for several modulation schemes in equicorrelated Rayleigh fading channels. Novel infinite series expressions for BER of TAS/MRC are proposed in this work. The authors observe that the existing literature on performance analysis of TAS/MRC in correlated channels implicitly or explicitly assume no correlation on the transmitter side. In this work the authors overcome this shortcoming. An alternate closed-form expression for BER performance of OSTBC MIMO systems is derived. This closed-form expression is computationally efficient than existing expressions. Monte Carlo simulations were performed to validate the analytical results. It has been observed that TAS/MRC outperforms OSTBC in terms of BER performance in equicorrelated Rayleigh fading channel. As a case study, performance comparison of cognitive radio (CR) links employing OSTBC and TAS/MRC MIMO systems is investigated in order to show the usefulness of the present analytical study. Even though TAS is the optimum transmit antenna technique in terms of BER performance, OSTBC seems to be a promising alternative for more realistic scenarios in CR systems.

Design and Evaluation of Pattern Reconfigurable Antennas for MIMO Applications

In recent years, reconfigurable antennas have been sought to improve the performance of multiple-input multiple-output (MIMO) wireless communication systems. Their ability to dynamically reconfigure their radiation pattern adds diversity in a manner that is not possible with fixed antennas. This paper investigates the performance benefits provided by pattern reconfigurable receiving antennas with uniform beam steering capability. Their potential performance is first estimated using simulations, and for the first time, the effect of uniform beam steering on MIMO system performance is evaluated in a real indoor channel using two electrically steerable passive array radiator (ESPAR) antennas. Performance comparison is made against a pair of monopole antennas using a hardware bit error rate (BER) test-bed that incorporates statistical spatial averaging in order to assess performance improvements in a more realistic way, and analyze the effect of antenna diversity on the overall system performance. The MIMO-ESPAR system reduces BER with certain pattern combinations and excels in capacity evaluations. The ESPAR antennas improve the spatially averaged channel capacity by as much as 37% at 10 dB transmit SNR, and gain an additional 1 bit/s/Hz in peak capacity at 10 dB receive SNR from diversity gain alone. These improvements make pattern reconfigurable antennas promising options in MIMO-related applications.

Simplified Processing for High Efficiency Wireless Communication Employing Multiple Antenna Array

use of multiple antennas for wireless systems has gained vast interest during the last decade - both in academic world and industry. Multiple antennas can be utilized in order to accomplish a multiplexing gain, a diversity gain, or an antenna gain, thus enhancing the bit rate, the error performance, or the signal-to-noise-plus- interference ratio of wireless systems, respectively. With the huge amount of research in the field of multiple- antenna systems, often called multiple-input multiple- output (MIMO) systems, has evolved rapidly. This paper is intended to provide the complete understanding of the MIMO System. In this work, the performance of MIMO Systems have been analyzed with transmit and receive diversity. This paper also includes the comparison of MIMO technology with SISO, MISO and SIMO on the basis of capacity by simulating different scenarios in MATLAB.

LR-Aided MIMO Detectors under Correlated and Imperfectly Estimated Channels

In this contribution, lattice reduction (LR) technique is applied to improve the multiple-input multiple-output (MIMO) detector performance under correlated channels and imperfect channel estimation constrains. Zero-forcing, minimum mean squared error, ordered successive interference cancellation and sphere decoding (SD) detectors are analysed taking into consideration (a) different correlated fading channel indexes, (b) increasing spectral efficiency, by combining number of transmit antennas and modulation formats, and (c) channel coefficient error estimations. Analysis of correlated channel effects over the MIMO system performance equipped with different LR-aided detectors are carried out, indicating the robustness of those detectors and the SD–MIMO detector deficiency to deal with such channel condition. Besides, computational complexities are compared aiming to determine the best LR–MIMO detection scheme under the perspective of performance-complexity tradeoff.

Two-Stage Channel Quantization for Scheduling and Beamforming in Network MIMO Systems: Feedback Design and Scaling Laws

This paper proposes an efficient two-stage channel quantization and feedback scheme for the downlink limited-feedback network multiple-input multiple-output (MIMO) system. In the first stage, the users report their best set of base-station antenna and physical resource block combinations, and the base-stations schedule the best user for each antenna in each resource block. The scheduled users are then polled in the second stage to feedback their quantized channel vectors. This paper proposes an analytical framework to show that, under a total feedback budget of B bits, the number of bits assigned to the second feedback stage should scale as log B, and in quantizing channel vectors from different base-stations, each user should allocate feedback bits in proportion to the channel magnitudes in dB scale. Under these optimized bit allocations, the overall sum rate of the system is shown to scale double-logarithmically with B, linearly with the total number of antennas, and logarithmically with transmit power, thus achieving both multiuser diversity and spatial multiplexing gains under limited feedback. Finally, realistic wireless propagation model of an urban small-cell deployment is used to show that the proposed scheme can approach the performance of a network MIMO system with full channel state information with only modest amount of channel feedback.

Energy‐efficient power allocation for training‐based multiple‐input multiple‐output system with and without feedback

In this study, the authors discuss energy-efficient power allocation for training-based multiple-input multiple-output (MIMO) system with and without feedback. Firstly, they consider the non-feedback MIMO system, where data power is equally allocated to transmit antennas. With pilot power fixed, the energy efficiency (EE)-optimal data power is derived based on the pseudo-concavity of the EE expression. When data power and pilot power are both variable, a convergent alternating optimisation algorithm is proposed to obtain EE-suboptimal data power and pilot power. Then, they consider the feedback MIMO system where data power is water-filling allocated to transmit antennas. Although the effective transmit antennas number at this scenario is discrete, they propose an algorithm to calculate it and its corresponding EE-optimal data power with pilot power fixed. When data power and pilot power are both variable, a similar convergent alternating optimisation algorithm is given. The numerical results demonstrate the EE performance of the training-based MIMO system with and without feedback. The impacts of multi-antennas configuration, circuit power and block length are also shown and analysed.

Effects of channel aging in massive MIMO systems

Multiple-input multiple-output (MIMO) communication may provide high spectral efficiency through the deployment of a very large number of antenna elements at the base stations. The gains from massive MIMO communication come from the use of multiuser MIMO on the uplink and downlink, but with a large excess of antennas at the base station compared to the number of served users. Initial work on massive MIMO did not fully address several practical issues associated with its deployment. This paper considers the impact of channel aging on the performance of massive MIMO systems. The effects of channel variation are characterized as a function of different system parameters assuming a simple model for the channel time variations at the transmitter. Channel prediction is proposed to overcome channel aging effects. The analytical results on aging show how capacity is lost due to time variation in the channel. Numerical results in a multiceli network show that massive MIMO works even with some channel variation and that channel prediction could partially overcome channel aging effects.

On the Performance of Downlink MIMO Systems with Different Operating Frequencies

Currently, multiple input multiple output (MIMO) systems are adopted in many current cellular systems such as Long Term Evolution or 802.16 m. However, the performance of MIMO systems is greatly dependent on system parameters and environments. In this study, we evaluate the performance of downlink MIMO systems to find out which operating frequency among 800 MHz, 2.5 GHz, and 3.5 GHz is the best for next generation MIMO cellular systems. For each operating frequency, we consider the most prevalent types of mobile stations (MSs), the USB type, PDA type, and laptop type, which experience different mutual coupling between neighbor antenna elements mainly caused by the miniaturization of MSs. System simulation results show that regardless of the MS type, average and edge throughputs are almost the same for all the considered frequencies in the interference-limited environment. In contrast, the operating frequency of 800 MHz at which the mobile type with a larger antenna spacing has spatial multiplexing gain, provides the best average and edge throughputs in noise limited system environments.

A smart scheme for relay selection in cooperative wireless communication systems

The performance of multiple-input multiple-output systems using spatial multiplexing can be degraded when the spatial information channels are correlated. This work proposes a solution to this problem, which is based on a cooperative wireless communication system. Within the cooperative system, the relay is selected either randomly or using the smart selection scheme, a simple and distributed approach proposed herein. These relay selection schemes are evaluated for several situations within a small cell environment, using a simulator that generates frequency-selective channel realizations. The simulation results show that the smart selection scheme yields high capacity gains close to the theoretical maximum gain.

Impact and compensation of I / Q imbalance on channel reciprocity of time‐division‐duplexing multiple‐input multiple‐output systems

Direct-conversion-based wireless communication systems suffer from I/Q imbalances in the front-end analog processing. In this study, the authors investigate the impact of frequency-independent (FI) I/Q imbalance on the channel reciprocity of time-division-duplexing (TDD) multiple-input multiple-output (MIMO) systems over frequency flat-fading channels. Moreover, in order to compensate the channel non-reciprocity caused by FI I/Q imbalance, the authors propose two pre-compensation algorithms with and without I/Q imbalance parameters. The performance of the TDD MIMO system under study is evaluated in terms of downlink capacity and bit-error rate. Simulation results show that the proposed algorithms can effectively mitigate the negative effect of FI I/Q imbalance on the channel reciprocity.

Performance Comparison of MIMO Systems over AWGN and Rician Channels with Zero Forcing Receivers

Multiple-Input Multiple-Output (MIMO) systems have been emerged as a technical breakthrough for high-data-rate wireless transmission. The performance of MIMO system can be improved by using different antenna selection so as to provide spatial diversity. In this paper, the performance of MIMO system over AWGN (Additive White Gaussian Noise) and Rician fading channels with ZF receiver is analyzed using different antenna configurations. The bit error rate performance characteristics of ZeroForcing (ZF) receiver is studied for M-PSK (M-ary Phase Shift Keying) modulation technique using AWGN and Rician channels for the analysis purpose and their effect on BER (Bit Error Rate) have been presented.

Performance Analysis of MIMO Systems over AWGN Channel with Antenna Selection using Zero Forcing Receivers

data rates within the limited radio frequency (RF) spectrum is always desirable that leads to radios with capabilities beyond a single-input single-output (SISO) topology. Recently introduced wireless systems have adopted multiple-input multiple-output (MIMO) topologies that use two or more transmitters and two or more receivers to send data simultaneously over the same RF bandwidth. The performance of MIMO system can be improved by using multiple antennas at transmitter and receiver so as to provide spatial diversity. In this paper, the performance analysis of MIMO system over AWGN fading channel with ZF receiver is presented. The effects of the antenna selection can also be analyzed from the simulated results. The BER (Bit Error Rate) performance characteristics of Zero-Forcing (ZF) receiver is investigated for M-PSK modulation technique over the AWGN channel.

Performance Analysis of Various Symbol Detection Techniques in Wireless MIMO System With MQAM Modulation Over Rayleigh Fading Channel

Wireless communication is one of the most effective areas of technology development of our time. Wireless communications today covers a very wide array of applications. In this paper, we study the performance of general MIMO system, the performance of Zero Forcing (ZF), Linear Least Square Estimator (LLSE), V-BLAST/ZF, V-BLAST/LLSE of 4x4, 4x6 & 4x8 with 4-QAM & 16-QAM modulation in i i d Rayleigh fading channel. We seen that SER performance of 4x8 antennas and 4-QAM modulation scheme outperforms others. Result shows that for higher modulation schemes SER performance degrades as well as SER performance increases for higher no of receiver antennas. Keywords - Multi Input Multi Output, Zero-forcing receiver, Linear Least Square Estimation, V-BLAST. I. INTRODUCTION Multiple antennas placed at the transmitter and/or receiver in wireless communication systems can be used to substantially improve system performance by leveraging the characteristics of the wireless channel. These systems, termed as Multiple Input Multiple Output (MIMO), require two or more antennas placed at the transmitter and at the receiver. In these systems, performance gains are achieved as multiple transmitters simultaneously input their signal into the wireless channel and then combinations of these signals simultaneously output from the wireless channel into the multiple receivers. Multiple antenna systems take advantage of the spatial diversity obtained by placing separate antennas in a dense multipath scattering environment (2). There are two modes of employing MIMO - spatial multiplexing and diversity. Spatial multiplexing mode is aimed at transmitting independent data through each transmit antenna; thereby increasing data transmission rate. In diversity mode, same data is transmitted through more than one antenna; thus increasing the chances of the transmitted data reaching the receiver correctly(4).

Experimental verification of decoupling on channel capacity for MIMO communications

In multiple-input multiple-output (MIMO) communications, mutual coupling is a notorious issue due to limited space available for mobile terminals. Most of theoretical analysis and simulation investigated the channel capacity and the performance of MIMO systems in the presence of antenna coupling. But in this paper, we have firstly experimentally studied the impact of the decoupling on channel capacity for MIMO radio communications. It is demonstrated that channel capacity can be enhanced by decoupling.

Performance of MUTP-aided MIMO systems over correlated frequency-selective wireless communication channels: a multi-cell perspective

In this article, we investigate the performance of multiuser transmitter preprocessing (MUTP)-aided multiple-input multiple-output (MIMO) systems in a multi-cell multiuser setting where co-channel interference (CCI) is the major channel impairment, for both uplink (UL) and downlink (DL) transmissions. CCI can considerably reduce data rates resulting in outages in cellular systems, particularly at the cell edges in DL transmission. The MUTP considered in this article is based on singular value decomposition (SVD), which exploits the channel state information (CSI) of all the users at the base stations (BSs) with the aid of BS cooperation, and only the individual users' CSI at the mobile stations (MSs) for both UL and DL transmissions. In particular, in this article, we study the effects of three types of delay spread distributions coupled with different interferer configurations over correlated and uncorrelated frequency-selective channels. Our simulation study shows that SVD-aided MUTP perfectly eliminates CCI with lesser detection complexity under perfect CSI. Also, we provide performance comparisons of SVD-aided MUTP with various precoding techniques widely addressed in literature, and the results show that it provides better achievable symbol error rate (SER) by mitigating multi-stream interference (MSI) and CCI. Further, simulation results demonstrate that compared to equal CCI, the presence of a dominant interferer can lead to more degradation in the system performance in terms of achievable SER while, further degradation results when noise is dominant. Furthermore, this study confirms that imperfect CSI as well as imperfect power control can lead to degradation in the system performance.

Performance of MIMO systems in measured indoor channels with transmitter noise

Abstract This study analyzes the impact of transmitter noise on the performance of multiple-input multiple-output (MIMO) systems with linear and nonlinear receivers and precoders. We show that the performance of MIMO linear and decision-feedback receivers is not significantly influenced by the presence of transmitter noise, which does not hold true in the case of MIMO systems with precoding. Nevertheless, we also show that this degradation can be greatly alleviated when the transmitter noise is considered in the MIMO precoder design. A MIMO testbed developed at the University of A Coruña has been employed for experimentally evaluating how much the transmitter noise impacts the system performance. Both the transmitter noise and the receiver noise covariance matrices have been estimated from a set of 260 indoor MIMO channel realizations. The impact of transmitter noise has been assessed in this realistic scenario.

Impact of Transceiver RFIC Impairments on MIMO System Performance

This paper addresses the performance degradation of multiple-input multiple-output (MIMO) communication systems due to MIMO wireless transceiver radio frequency integrated circuits (RFIC) imperfections. The effects of signal coupling in RF front-end, frequency synthesizer phase noise, and the gain imbalance between different radio paths are investigated. These issues are explored by analytical derivations and results are verified by Monte Carlo simulations. The analytical model achieves a good agreement with the simulation results. The conclusion can serve as a useful reference for MIMO RFIC designers.

QR Decomposition-Based Antenna Selection for Spatial Multiplexing UWB Systems with Zero-Forcing Detectors Followed by Rake Combiners

This letter presents a criterion for selecting a transmit antenna subset when ZF detectors followed by Rake combiners are employed for spatial multiplexing (SM) ultra-wideband (UWB) multiple input multiple output (MIMO) systems. The presented criterion is based on the largest minimum post-processing signal to interference plus noise ratio of the multiplexed streams, which is obtained on the basis of QR decomposition. Simulation results show that the proposed antenna selection algorithm considerably improves the BER performance of the SM UWB MIMO systems when the number of multipath diversity branches is not so large and thus offers diversity advantages on a log-normal multipath fading channel.

Distribution and Density Functions of Capacity for Layered Space Time Architecture

In wireless communications spectrum is a scarce resource, and hence imposes a high cost on high data rate transmission. With the emergence of multiple antenna system, another very resourceful dimension-space was utilized for information transmission in air. It has been proved that multiple antenna systems provide higher gain in capacity without increasing the use of spectrum, reliability, throughput, power consumption and less sensitivity to fading, therefore leading to high data rates of wireless communication systems, which is the most sorted outcome of all research work. The study of performance limits of Multiple Input Multiple Output (MIMO) system becomes most important to design and understanding MIMO systems. There are many schemes that can be applied to MIMO systems, such as space time block codes, space time trellis codes and Layered Space Time Architecture. In this paper, the performance of general MIMO system based on Layered Space Time Architecture is studied. For different number of transmit and receive antennas, the Probability Density Function (pdf) and Cumulative Distribution Function (cdf) distributions for capacity of different layers for different SNRs were analyzed and plotted.

Effect of antenna directivity on performance of multiple input multiple output systems in an underground gold mine

In this study two measurement campaigns are presented, where two types of multiple input multiple output (MIMO) antennas are investigated in an underground mine environment, aiming to identify the optimal antenna technology that allows to improve the performance of MIMO system in terms of root mean square (RMS) delay spread, path loss and capacity. It is found that in such scatter-rich environment, for line of sight scenario the directional antennas have provided significant suppression of multipath, giving a reduction in received RMS delay spread, and a corresponding increase in the correlation, which consequently decrease the channel capacity.