Design Of MIMO Systems Research Articles

HOS-Based Semi-Blind Spatial Equalization for MIMO Rayleigh Fading Channels

In this paper, we concentrate on the direct semi-blind spatial equalizer design for MIMO systems with Rayleigh fading channels. Our aim is to develop an algorithm which can outperform the classical training-based method with the same training information used and avoid the problems of low convergence speed and local minima due to pure blind methods. A general semi-blind cost function is first constructed which incorporates both the training information from the known data and some kind of higher order statistics (HOS) from the unknown sequence. Then, based on the developed cost function, we propose two semi-blind iterative and adaptive algorithms to find the desired spatial equalizer. To further improve the performance and convergence speed of the proposed adaptive method, we propose a technique to find the optimal choice of step size. Simulation results demonstrate the performance of the proposed algorithms and comparable schemes.

Investigations in Satellite MIMO Channel Modeling: Accent on Polarization

Due to the much different environment in satellite and terrestrial links, possibilities in and design of MIMO systems are rather different as well. After pointing out these differences and problems arising from them, two MIMO designs are shown rather well adapted to satellite link characteristics. Cooperative diversity seems to be applicable; its concept is briefly presented without a detailed discussion, leaving solving particular satellite problems to later work.On the other hand, a detailed discussion of polarization time-coded diversity (PTC) is given. A physical-statistical model for dual-polarized satellite links is presented together with measuring results validating the model. The concept of 3D polarization is presented as well as briefly describing compact 3D-polarized antennas known from the literature and applicable in satellite links. A synthetic satellite-to-indoor link is constructed and its electromagnetic behavior is simulated via the FDTD (finite-difference time-domain) method. Previous result of the authors states that in 3D-PTC situations, MIMO capacity can be about two times higher than SIMO (single-input multiple-output) capacity while a diversity gain of nearly 2 × 3 is further verified via extensive FDTD computer simulation.

Stable controller design for MIMO systems: an LMI approach

A unified approach to the strong stabilisation problem and the H infin strong stabilisation problem is presented. New sufficient conditions for the existence of strongly stabilising controllers and stable H infin controllers are derived, in a unified manner, in terms of the solvability of a positive real controller synthesis problem and a multi-objective control problem, respectively. A linear matrix inequality (LMI) technique developed by Scherer et al. is adopted to make the most use of its power to deal with the general case of the problems. Several advantages brought by the adopted LMI technique are explored. New parameterisations of stable controllers for both the problems are discussed. In particular, the parameterisations are independent of a particular method for solving strong stabilisation problems. Explicit state-space synthesis algorithms are given and numerical examples are provided to demonstrate the potential of the proposed methods

Finite-SNR Diversity–Multiplexing Tradeoff for Correlated Rayleigh and Rician MIMO Channels

A nonasymptotic framework is presented to analyze the diversity-multiplexing tradeoff of a multiple-input-multiple-output (MIMO) wireless system at finite signal-to-noise ratios (SNRs). The target data rate at each SNR is proportional to the capacity of an additive white Gaussian noise (AWGN) channel with an array gain. The proportionality constant, which can be interpreted as a finite-SNR spatial multiplexing gain, dictates the sensitivity of the rate adaptation policy to SNR. The diversity gain as a function of SNR for a fixed multiplexing gain is defined by the negative slope of the outage probability versus SNR curve on a log-log scale. The finite-SNR diversity gain provides an estimate of the additional power required to decrease the outage probability by a target amount. For general MIMO systems, lower bounds on the outage probabilities in correlated Rayleigh fading and Rician fading are used to estimate the diversity gain as a function of multiplexing gain and SNR. In addition, exact diversity gain expressions are determined for orthogonal space-time block codes (OSTBC). Spatial correlation significantly lowers the achievable diversity gain at finite SNR when compared to high-SNR asymptotic values. The presence of line-of-sight (LOS) components in Rician fading yields diversity gains higher than high-SNR asymptotic values at some SNRs and multiplexing gains while resulting in diversity gains near zero for multiplexing gains larger than unity. Furthermore, as the multiplexing gain approaches zero, the normalized limiting diversity gain, which can be interpreted in terms of the wideband slope and the high-SNR slope of spectral efficiency, exhibits slow convergence with SNR to the high-SNR asymptotic value. This finite-SNR framework for the diversity-multiplexing tradeoff is useful in MIMO system design for realistic SNRs and propagation environments

A Markov-Kronecker model for analysis of closed-loop MIMO systems

Closed-loop MIMO systems have gained much interest recently due to their ability in improving performance. Although many spatial-temporal MIMO channel models have been proposed, system limitations are not considered and the effects of a time varying channel on MIMO systems with a realistic feedback delay are also not available in an analytically tractable form. In this letter, we propose a composite model where both propagation and system factors are considered thus providing a simple and analytically tractable model for the performance evaluation and design of closed-loop MIMO systems

IMC-Based Controller Design for MIMO Systems.

In this paper, a design method for multivariable controllers in a unit output feedback configuration is presented. With the internal model control (IMC) principles, the objective closed-loop transfer functions are characterized in terms of process unavoidable non-minimum phase elements. A multivariable controller for best achievable performance is obtained with block diagram analysis and model reduction. The proposed design provides users with an option to choose between PID and high-order controllers to suit applications better. Stability and robustness are analyzed and simulation is provided to substantiate the superior performance of the proposed method.

Quantitative robust diagonal controller design for Mimo systems

In this paper we present a robust decoupled controller design method for MIMO systems by combining Perron‐Frobenius (PF) theory, Ostrowski's theorem and quantitative feedback theory (QFT). Our aim is to find a required robust controller with less complexity, namely to keep the number of ‘cross‐couplings’ of the controller as low as possible. To this end, the PF theory is first adopted to almost decouple the n‐dimensional perturbed MIMO inverse system into n SISO inverse subsystems, where the synthesized decoupler has a diagonal form. Moreover, Ostrowski's theorem allows us to design a constant feedback gain matrix with diagonal form such that the compensated inverse plant is of more diagonal dominance. The SISO QFT technique is then utilized to design a robust diagonal controller for each single loop of compensated plant. Ultimately, the required robust stability and tracking performance can indeed be achieved by the designed robust decoupled controller. Two numerical examples are given to illustrate that not only are all the required performances achieved, but also that the combined technique for designing a robust decoupled controller for a perturbed MIMO system is actually workable.

MSIM_RP - A Program Package for Design and Simulation of MIMO-Systems in Undergraduate Courses

Abstract The paper describes the essential features of a program package which was developed to provide help for design and simulation of linear MIMO-Systems. The main objective of the program is for use in education. This aspect is illustrated by two examples rather than going into details of the software.

Optimal design of discrete-time MIMO systems in the frequency domain

The purpose of this paper is to present a new design algorithm for discrete-time MIMO systems given as strictly proper z-domain transfer matrices. The algorithm combines some well-known results, partly adapting them for application to discrete-time systems. Basically, it consists of the following steps: (a) represent the system as a coprime right matrix fraction description G(z) = N(z)D−1(z), where D(z) is column reduced; (b) optimally (in some sense to be specified) choose a closed-loop denominator polynomial matrix DC1(z); and (c) compute a controller following the method by Wolovich (1973) such that the closed-loop transfer matrix is T(z) = N(z)D c1 −1(z)F for some constant matrix F.