Showing papers on "MIMO published in 1996"
18 Nov 1996
TL;DR: The discrete matrix multitone (DMMT) is proposed as an asymptotically optimal, practical spatio-temporal coding structure for the multiple-input multiple output, dispersive, spatially selective wireless communication channel.
Abstract: A compact model is derived for the multiple-input multiple output (MIMO), dispersive, spatially selective wireless communication channel. The multivariate information capacity behavior is then analyzed for various input and output antenna configurations. For high SNR conditions, the MIMO channel can exhibit a capacity slope in bits per dB of power increase that is proportional to the minimum of the number multipath components, the number of input antennas, or the number of output antennas. The discrete matrix multitone (DMMT) is proposed as an asymptotically optimal, practical spatio-temporal coding structure. Experimental examples that support the theoretical results are presented.
217 citations
11 Dec 1996
TL;DR: It is shown that, by inserting a nonlinear term of the system state in the MIMO linear sliding mode, a new terminal sliding mode is obtained for MIMo linear systems.
Abstract: A new terminal sliding mode control of MIMO linear systems is proposed. It is shown that, by inserting a nonlinear term of the system state in the MIMO linear sliding mode, a new terminal sliding mode is obtained for MIMO linear systems. A terminal sliding mode controller can then be designed to drive the system dynamics to reach and retain in the terminal sliding mode. By suitably designing the parameter matrices of the terminal sliding mode, the system states reach the system origin in finite time and the closed loop system is infinite stable in the terminal sliding mode.
126 citations
TL;DR: A direct data stream architecture for complete digital fuzzy controller is shown as an improved solution for high-speed, cost-effective, real-time control applications.
Abstract: In this paper, various aspects of digital fuzzy logic controller (FLC) design and implementation are discussed, Classic and improved models of the single-input single-output (SISO), multiple-input single-output (MISC), and multiple-input multiple-output (MIMO) FLCs are analyzed in terms of hardware cost and performance. A set of universal parameters to characterize any hardware realization of digital FLCs is defined. The comparative study of classic and alternative MIMO FLCs is presented as a generalization of other controller configurations. A processing element for the parallel FLC architecture realizing improved inferencing of MIMO system is designed, characterized, and tested. Finally, as a case feasibility study, a direct data stream architecture for complete digital fuzzy controller is shown as an improved solution for high-speed, cost-effective, real-time control applications.
110 citations
07 May 1996
TL;DR: A novel method of second order channel estimation exploiting the simultaneous MA and AR nature of the observations, it displays however a considerable improvement as compared to the original linear prediction approach.
Abstract: Multipath propagation appears to be a typical limitation in mobile digital communications where it leads to severe intersymbol interference. The classical techniques to overcome this problem use either periodically sent training sequences or blind approaches. This paper addresses the blind identification of FIR multiple input multiple output (MIMO) transfer functions in the case where the number of inputs is strictly less than the number of outputs. We consider a second order identification providing signals extraction up to a regular instantaneous mixture matrix. A novel method of second order channel estimation is presented. Basically exploiting the simultaneous MA and AR nature of the observations, it displays however a considerable improvement as compared to the original linear prediction approach. Performance study and comparison with the existing approach is provided by computer simulations.
59 citations
11 Dec 1996
TL;DR: In this article, the use of a continuous-time subspace model identification method was demonstrated in the identification of MIMO state-space models. But the proposed method gives a biased estimate of the system matrices, but the authors show how to minimise this bias by a proper choice of the lag used for the instruments.
Abstract: This paper demonstrates the use of a continuous-time subspace model identification method, in the identification of MIMO state-space models. The measured input and output signals are assumed to be measured at regularly spaced sampling instances. The presence of both measurement and process noise is considered. The proposed method gives a biased estimate of the system matrices, but we shall show how to minimise this bias by a proper choice of the lag used for the instruments. Finally, the applicability of the method is demonstrated in the identification of aircraft dynamics.
55 citations
07 May 1996
TL;DR: This work considers mobile radio communications with one user of interest and possibly interfering users and noise, over several discrete-time channels obtained either by oversampling or from multiple antennas, and shows it can alternatively pass the vector received signal through both a MISO matched filter and a MIMO blocking equalizer.
Abstract: We consider mobile radio communications with one user of interest and possibly interfering users and noise, over several discrete-time channels obtained either by oversampling or from multiple antennas. The optimal receiver structure for one signal of interest plus spatially and temporally correlated noise is MLSE equalization with an appropriately weighted metric for vector signals. We show however that we can alternatively pass the vector received signal through both a MISO (multi-input single output) matched filter and a MIMO blocking equalizer. The blocking equalizer output is independent of the signal of interest and is used as the input to a MISO Wiener filter that reduces the noise in the matched filter output. The training sequence of the signal of interest can be used to estimate the corresponding channel, from which the matched filter and blocking equalizer can be determined. The remaining quantities can be adapted from the available signals.
38 citations
28 Apr 1996
TL;DR: In the case of narrowband multipath propagation, it is shown that the m parameter is interpreted in a similar fashion as the K parameter of the Rice distribution, and a geometric theory of Nakagami multipath fading is formulated.
Abstract: The focus in this paper is on physical interpretation of the Nakagami fading phenomenon in multipath mobile radio propagation through its parameters m and /spl Omega/. In the case of narrowband multipath propagation, it is shown that the m parameter is interpreted in a similar fashion as the K parameter of the Rice distribution. We also formulate a geometric theory of Nakagami multipath fading and relate the m parameter with the number of resolvable multipaths in a wideband multipath propagation scenario. We provide a physical interpretation of this geometric theory which can also be shown to be supported by channel measurements reported in literature. Finally the two interpretations are used together to quantify the multipath diversity of a given channel.
35 citations
TL;DR: The theoretical results are illustrated on an extensive numerical example to demonstrate the effectiveness of the identification schemes developed and the worst-case identifiers obtained using the cost-to-come function method.
Abstract: This paper addresses the worst-case parameter identification problem for uncertain single-input/single-output (SISO) and multi-input/multi-output (MIMO) linear systems under partial state measurements and derives worst-case identifiers using the cost-to-come function method. In the SISO case, the worst-case identifier obtained subsumes the Kreisselmeier observer as part of its structure with parameters set at some optimal values. Its structure is different from the common least-squares (LS) identifier, however, in the sense that there is additional dynamics for the state estimate, coupled with the dynamics of the parameter estimate in a nontrivial way. In the MIMO case as well, the worst-case identifier has additional dynamics for the state estimate which do not appear in the conventional LS-based schemes. Also for both SISO and MIMO problems, approximate identifiers are obtained which are numerically much better conditioned when the disturbances in the measurement equations are "small". The theoretical results are then illustrated on an extensive numerical example to demonstrate the effectiveness of the identification schemes developed.
34 citations
TL;DR: In this article, a new algorithm for control loop performance monitoring based on Filtering and Correlation Analysis (FCOR) is introduced, which requires only routine closed-loop process output data, plus a priori knowledge or estimation of the time-delay or interactor matrix of the MIMO process.
27 citations
TL;DR: An alternative QFT framework is proposed for the design of multiple-input multiple-output feedback systems with significant plant uncertainty, such that not only is the main channel performance easily achieved, but also the trade-offs of performance bounds between the loops become transparent during the system synthesis.
Abstract: An alternative QFT framework is proposed for the design of multiple-input multiple-output (MIMO) feedback systems with significant plant uncertainty. Sufficient conditions are first derived to assure the achievement of the given off-diagonal performance. Then the given performance bounds on each main channel are reallocated on a reasonable basis, such that not only is the main channel performance easily achieved, but also the trade-offs of performance bounds between the loops become transparent during the system synthesis.
26 citations
TL;DR: The problem of decision feedback equalization (DFE) for such a system with multitone modulation with direct sequence spectrum spreading with adaptive least mean square (LMS) and recursive least square (RLS) structures is analyzed.
Abstract: The combination of multitone modulation with direct sequence spectrum spreading (DS/SS) has been introduced in the past. The performance of a correlation receiver has been evaluated for a multipath channel and in the presence of an additional multiple access interference. We analyze the problem of decision feedback equalization (DFE) for such a system. In order to understand the potential of the system with equalization, we first study the steady-state behavior of the equalizer for a minimum mean square error (MMSE) criterion. The investigation is carried out for a receiver made of a bank of filters matched to both the symbol shape and the channel, and for a two path channel. Assuming transmission of binary phase shift keying (BPSK) symbols, an exact expression of the bit error probability is obtained in the form of an integral. Then adaptive least mean square (LMS) and recursive least square (RLS) structures are derived. The performance of the adaptive RLS algorithm is demonstrated by means of computer simulations.
TL;DR: This paper employs the spatial diversity equalizers (SDE) to increase the effective channel bandwidth by minimizing the mean-square error (mse) and calculates the probability of error (PE) to show that a factor of 3-4 of channel reuse is possible.
Abstract: The available bandwidth of ocean acoustic channels is inherently narrow that impedes high-transmission rate and makes it difficult for multiple users to communicate simultaneously. To alleviate this problem, spatial diversity antennas are used to increase the date rate. In this paper, we employ the spatial diversity equalizers (SDE) to increase the effective channel bandwidth by minimizing the mean-square error (mse). Although joint equalizers have been used in digital telephone subscriber lines to suppress crosstalk, we apply the concept to ocean acoustic channels and show that multiuser communication is possible despite the narrow-channel bandwidth. In addition, we will show that the advantage of SDE is not because we use more taps, but because we collect the data carried through various ocean paths. By applying the saddle point integration method to multiinput multioutput (MIMO) channels, we compute the probability of error (PE) to show that a factor of 3-4 of channel reuse is possible.
23 Jun 1996
TL;DR: The new blind equalization algorithm for MIMO channels can be applied to separate and equalize the signals received by antenna arrays in communication systems.
Abstract: This paper investigates adaptive blind equalization for multiple-input and multiple-output (MIMO) channels and its application to blind separation of multiple signals received by antenna arrays in communication systems. The performance analysis of the CMA equalizer used in MIMO channels is first presented. Our analysis results indicate that for the MIMO FIR channels satisfying certain conditions, the MIMO-CMA FIR equalizer is able to remove the ISI and co-channel interference regardless of the initial setting of the blind equalizer. To recover all input signals simultaneously, a novel MIMO channel blind equalization algorithm is then developed. The global convergence of the new algorithm for MIMO channels is proved. Hence, the new blind equalization algorithm for MIMO channels can be applied to separate and equalize the signals received by antenna arrays in communication systems. Finally, computer simulations are presented to confirm our analysis and illustrate the performance of the new algorithm.
TL;DR: In this article, a two-step procedure for the design of multivariable controllers is presented, where SISO controllers are designed for every process transfer function matrix element separately, and then the MIMO controller is computed by inverting a matrix containing the reciprocals of the SISO controller.
03 Nov 1996
TL;DR: In this article, a new prefilter design method for MIMO communication channels with equalizers is described, which is designed in the frequency domain to make the channel easier to equalize.
Abstract: This paper describes a new prefilter design method for MIMO communication channels with equalizers. The prefilter is designed in the frequency domain to make the channel easier to equalize. We apply the singular value decomposition (SVD) of the channel frequency response to design the prefilter. The new prefilter achieves a performance improvement at high signal to noise ratio (SNR) while keeping the performance at low SNR. We also show the advantage of transmitter diversity.
TL;DR: In this article, a methodology for identifying multiple-input multiple-output (MIMO) step response models while the process is operating under multivariable control is presented. But the identification of these models is usually carried out under Open-Loop conditions, where large quantities of data are collected and/or large process perturbations are used.
01 Sep 1996
TL;DR: This paper indicates how to extend the original subspace based approach to the general MIMO case based on a sub-space analysis to allow a perfect recovery of the system parameters and excitation in a noise free environment.
Abstract: This contribution addresses the blind identification of Multiple Input Multiple Output (MIMO) linear FIR systems having a number of inputs less than the number of outputs. Recent publications have proposed an efficient second order identification method in the Single Input Multiple Output (SIMO) case. Based on a sub-space analysis, it allows a perfect recovery of the system parameters and excitation in a noise free environment. In this paper we indicate how to extend the original subspace based approach to the general MIMO case.
07 May 1996
TL;DR: An iterative, Godard (1980) cost based approach is considered for spatio-temporal equalization and MIMO impulse response estimation, showing that all stable local minima correspond to desirable minima when doubly infinite equalizers are used.
Abstract: Equalization and estimation of the matrix impulse response function of MIMO digital communications channels in the absence of any training sequences is considered. An iterative, Godard (1980) cost based approach is considered for spatio-temporal equalization and MIMO impulse response estimation. Stationary points of the cost function are investigated and it is shown that all stable local minima correspond to desirable minima when doubly infinite equalizers are used. The inputs are extracted and cancelled one-by-one. The matrix impulse response is then obtained by cross-correlating the extracted inputs with the observed outputs. Identifiability conditions are analyzed. Computer simulation examples are presented to illustrate the proposed approach.
10 Sep 1996
TL;DR: This paper investigates the performance of OFDM without guard time but with MIMO equalization, and shows that equalized OFDM outperforms OFDM with guard time.
Abstract: Recently the concept of multitone modulation or OFDM has received much attention. For such a modulation, the dispersiveness of the channel is classically solved by the technique of guard time. In the present paper we investigate the performance of OFDM without guard time but with MIMO equalization. Linear and decision-feedback structures structures are derived for an MMSE criterion and their performance is assessed by means of their steady-state behavior. Symbol rate equalizers following channel matched filters are derived and investigated. It is shown that equalized OFDM outperforms OFDM with guard time.
TL;DR: An iterative, Godard cost based approach is considered for spatio-temporal equalization and MIMO impulse response estimation and it is shown that all stable local minima correspond to desirable minima when doubly infinite equalizers are used.
Abstract: This paper is concerned with the problem of blind separation of independent signals (sources) from their linear convolutive mixtures. The problem consists of recovering the sources up to shaping filters from the observations of multiple-input multiple-output (MIMO) system output. The various signals are assumed to be linear but not necessarily i.i.d. (independent and identically distributed). The problem is cast into the framework of spatio-temporal equalization and estimation of the matrix impulse response function of MIMO channels (systems). An iterative, Godard cost based approach is considered for spatio-temporal equalization and MIMO impulse response estimation. Stationary points of the cost function are investigated and it is shown that all stable local minima correspond to desirable minima when doubly infinite equalizers are used. Analysis is also provided for the case when finite-length equalizers exist. The various input sequences are extracted and cancelled one-by-one. The matrix impulse response is then obtained by cross-correlating the extracted inputs with the observed outputs. Identifiability conditions are analyzed. Computer simulation examples are presented to illustrate the proposed approach.
11 Dec 1996
TL;DR: In this article, a new approach for the solution for the l/sub 1/ optimal control problem in the MIMO case which avoids zero interpolation in the numerical solution is provided.
Abstract: The aim of this paper is to provide a new approach for the solution for the l/sub 1/ optimal control problem in the MIMO case which avoids zero interpolation in the numerical solution. While exact optimal solutions may not be computed, solutions which are arbitrarily close to optimal are obtained. Duality theory is utilized to provide converging upper and lower bounds for the optimal l/sub 1/ norm.
23 Jun 1996
TL;DR: A new technique for blind equalization of multiple-input multiple-output (MIMO) communication channels is presented, and it is shown through simulations that the new technique can converge much faster than prior techniques.
Abstract: We present a new technique for blind equalization of multiple-input multiple-output (MIMO) communication channels. In scalar channels it is common to follow a blind equalizer adapted according to the constant-modulus algorithm (CMA) by a phase-locked loop to compensate for carrier frequency offset. We generalize this structure to multiple dimensions, and propose to follow a blind MIMO equalizer adapted according to the vector CMA by a multidimensional phase-locked loop. We show through simulations that the new technique can converge much faster than prior techniques.
08 Jan 1996
Abstract: This paper proposes some effective self-tuning control strategies for isolated wind-diesel power generation systems. Detailed modelling and studies on both single-input single-output (SISO) as well as multi-input multi-output (MIMO) self tuning regulators, applied to a typical system, are reported. Further, the effect of introducing a superconducting magnetic energy storage (SMES) unit on the system performance has been investigated. The MIMO self-tuning regulator controlling the hybrid system and the SMES in a coordinated manner exhibits the best performance.
TL;DR: The result is based on the robustness of the well known diagonal dominance of the system return difference matrix, which allows for a simple application of the Nyquist criterion to a multi-input/multi-output (MIMO) system.
Abstract: This paper provides sufficient conditions for robust stability of a multivariable interval feedback system. The result is based on the robustness of the well known diagonal dominance of the system return difference matrix, which allows for a simple application of the Nyquist criterion to a multi-input/multi-output (MIMO) system.
AT&T1
TL;DR: In this paper, a blind identification of multiple-input/multiple-output (MIMO) channels based on second-order statistics of the channel outputs and its application in blind channel equalization and signal-separation is discussed.
Abstract: To separate and recover multiple signals in data communications, antenna arrays and acoustic sensor arrays, the impulse responses of multiple-input/multiple-output (MIMO) channels have to be identified explicitly or implicitly. This paper deals with the blind identification of MIMO FIR channels based on second-order statistics of the channel outputs and its application in blind channel equalization and signal-separation. We first investigate the identifiability of MIMO FIR channels, and obtain a necessary and sufficient condition for MIMO FIR channels to be identifiable up to a unitary ambiguity matrix using second-order statistics. Next, we extend the identification algorithms for single-input/multiple-output (SIMO) FIR channels, such as the algebraic algorithm and the subspace algorithm to the identification of MIMO FIR channels. Since the ambiguity matrix cannot be estimated using second-order statistics, we then present a fourth-order cumulant based ambiguity matrix estimation algorithm. Finally, we demonstrate effectiveness of the algorithms in this paper by computer simulations.
11 Dec 1996
TL;DR: This paper presents a novel off-line algorithm to train direct linear feedthrough radial basis function (DLF-RBF) networks that leads to parsimonious models of SISO or MIMO dynamical systems, a primordial aim when solving nonlinear system identification problems.
Abstract: This paper presents a novel off-line algorithm to train direct linear feedthrough radial basis function (DLF-RBF) networks. The algorithm basically explores the model error surfaces and combines an automatic determination of the number of RBF neurons with a hybrid optimization step to tune all parameters in the network. This leads to parsimonious models of SISO or MIMO dynamical systems, a primordial aim when solving nonlinear system identification problems. To demonstrate the effectiveness and the performance of the new method, it is applied to the identification of two highly nonlinear systems (one SISO and one MIMO system).
TL;DR: In this article, a recently presented tuning technique for multiple-input multiple-output (MIMO) systems, which avoids a trial-and-error approach, is analyzed into detail to understand to what systems it can be extended and in which cases it is unsuccessful, and the technique is shown to be applicable also to the control of MIMO systems with negative values of the relative gain array (RGA) and to systems with inner cascade loops.
01 Jan 1996
01 Jan 1996
TL;DR: In this article, a new approach for the solution for the e1 optimal control problem in the MIMO case which avoids zero interpolation in the numerical solution is proposed, while exact optimal solutions may not be computed, solutions which are aribitrarily close to optimal are obtained.
Abstract: The aim of this paper is to provide a new approach for the solution for the e1 optimal control problem in the MIMO case which avoids zero interpolation in the numerical solution. While exact optimal solutions may not be computed, solutions which are aribitrarily close to optimal are obtained. Duality theory is utilized to provide converging upper and lower bounds for the optimal l1 norm.
24 Jun 1996
TL;DR: This paper addresses the blind identification of multiple input multiple output (MIMO) systems with the number of inputs strictly less then the numberof outputs with a focus on the deconvolution performance, i.e the residual ISI at the output of ZFE.
Abstract: This paper addresses the blind identification of multiple input multiple output (MIMO) systems with the number of inputs strictly less then the number of outputs. In contrast to the standard FIR modelling we assume that the overall channel has an arbitrary finite order rational transfer function. Certain quite reasonable technical hypotheses allow one to adapt the existing linear prediction and subspace based approach and to implement a finite order zero-forcing equalizer (ZFE) in the noise-free case. The noise-free condition also yields a simple performance analysis which is quite accurate at low noise levels and provides a meaningful comparison of the proposed estimators. The robustness to additive noise is studied by computer simulations for both techniques. We focus on the deconvolution performance, i.e the residual ISI at the output of ZFE.