Showing papers on "MIMO published in 1999"
TL;DR: The capacity of multiple input, multiple output (MIMO) wireless channels is computed for Ricean channels using a geometrical interpretation of the MIMO channel capacity formula to find array geometries which greatly enhance channel capacity compared to single input-single output (SISO) systems.
Abstract: The capacity of multiple input, multiple output (MIMO) wireless channels is computed for Ricean channels. The novelty is a geometrical (ray-tracing) interpretation of the MIMO channel capacity formula to find array geometries which greatly enhance channel capacity compared to single input-single output (SISO) systems.
375 citations
06 Jun 1999
TL;DR: The capacity of multiple input, multiple output wireless channels is computed for Ricean channels using a geometrical interpretation of the MIMO channel capacity formula to find array geometries which greatly enhance channel capacity compared to SISO systems.
Abstract: The capacity of multiple input, multiple output wireless channels is computed for Ricean channels The novelty is a geometrical (ray-tracing) interpretation of the MIMO channel capacity formula to find array geometries which greatly enhance channel capacity compared to SISO systems
232 citations
24 Oct 1999
TL;DR: A joint transmit and receive optimization scheme for the multi-input multi-output (MIMO) spatial multiplexing system (also known as BLAST) in a narrowband wireless channel is proposed and the optimum power allocation policy is derived.
Abstract: We propose a joint transmit and receive optimization scheme for the multi-input multi-output (MIMO) spatial multiplexing system (also known as BLAST) in a narrowband wireless channel. The optimum solution is found using the minimum mean square error criterion subject to average transmitter power constraint. The transmit and receive filters are shown to decouple the MIMO channel into parallel sub-chanhels. The optimum power allocation policy on these sub-channels is derived.
134 citations
TL;DR: This work proposes a statistically optimal least-squares identification procedure for MIMO polynomial transfer functions with the number of inputs strictly less than thenumber of outputs, characterized by high estimation accuracy as well as robustness to the model order choice.
85 citations
TL;DR: It is shown in this correspondence that the introduction of some cyclostationarity at the input may lead to an algorithm that is far more satisfactory because for both, it is less prone to indetermination problems, and the required assumptions are not too sophisticated.
Abstract: The blind identification of vector-valued FIR transfer functions using exclusively second-order statistics of the output has become conventional. The so-called subspace method provides a nice and efficient way of solving the problem. However, the extension to the multi-input/multi-output (MIMO) case is not that straightforward, and, for instance, some indetermination drawbacks may occur. We show in this correspondence that the introduction of some cyclostationarity at the input (which still leads to feasible systems) may lead to an algorithm that is far more satisfactory because for both, it is less prone to indetermination problems, and the required assumptions are not too sophisticated.
54 citations
TL;DR: The authors solve the open problem of the existence of double coprime factorizations for a large class of multi-input/multi-output (MIMO) three-dimensional (3-D) linear systems by proving that if all the unstable zeros of the contents associated with left and right matrix fraction descriptions of a given feedback stabilizable causal MIMO 3-D plant are simple, then the plant has a double copRime factorization.
Abstract: The authors solve the open problem of the existence of double coprime factorizations for a large class of multi-input/multi-output (MIMO) three-dimensional (3-D) linear systems. It is proven that if all the unstable zeros of the contents associated with left and right matrix fraction descriptions of a given feedback stabilizable causal MIMO 3-D plant are simple, then the plant has a double coprime factorization. The authors then give a parameterization of all stabilizing compensators for a MIMO 3-D system in this class. The key result developed in the paper is a novel and constructive technique of "replacing" an unstable polynomial with a stable polynomial step by step. An illustrative example is also provided.
47 citations
TL;DR: This effort removes the last restriction in the pole placement of such systems aside from being controllable as well as appending additional state equations to ensure that the embedded system has the property of lexicographically fixedness.
46 citations
07 Dec 1999
TL;DR: The concept of hierarchy of control is introduced leading to a new control parametrization and an error equation with triangular HFGM, which allows a sequential design of the adaptation scheme.
Abstract: This paper addresses the problem of designing model-reference adaptive control for linear MIMO systems with unknown high-frequency gain matrix (HFGM). The concept of hierarchy of control is introduced leading to a new control parametrization and an error equation with triangular HFGM, which allows a sequential design of the adaptation scheme. Significant reduction of the prior knowledge about the HFGM is achieved, overcoming the limitations of the known methods. A complete stability and convergence analysis is developed based on a new class of signals and their properties. Exponential stability is guaranteed under explicit persistency of excitation conditions.
38 citations
TL;DR: A multiple input multiple output (MIMO) broadband excitation and measurement method which is more time efficient than the standard standstill frequency response (SSFR) method and the identification procedure is self starting.
Abstract: This paper presents an alternative method for the identification of the d-axis parameters of a synchronous machine. The first part of the paper describes a multiple input multiple output (MIMO) broadband excitation and measurement method which is more time efficient than the standard standstill frequency response (SSFR) method. The second part describes a MIMO frequency domain identification procedure which estimates the d-axis parameters in 3 steps. The proposed identification procedure is self starting. It does not require starting values or other prior information. The measurement method and the identification procedure are tested on a 20 kVA salient pole synchronous machine.
38 citations
22 Aug 1999
TL;DR: This paper proposes to combine space-time block codes with multiple input multiple output equalizer (MIMO-EQ) for achieving transmit diversity in a frequency selective Rayleigh fading channel and simulation results show that the proposed system can achieve the full spatial diversity gain.
Abstract: In this paper, we propose to combine space-time block codes (ST-BC) with multiple input multiple output equalizer (MIMO-EQ) for achieving transmit diversity in a frequency selective Rayleigh fading channel In the proposed system, MIMO-EQ equalizes the channel into a temporal intersymbol interference (ISI)-free channel, and then a simple linear processing is used to perform the maximum likelihood (ML) decoding for ST-BC Our simulation results show that the proposed system can achieve the full spatial diversity gain
31 citations
TL;DR: It is shown that the variable rate scheme can only increase the channel error exponent and the optimal rate control rules are found for Rayleigh fading channels with feedback of channel states.
Abstract: We have evaluated the information theoretical performance of variable rate adaptive channel coding for Rayleigh fading channels. The channel states are detected at the receiver and fed back to the transmitter by means of a noiseless feedback link. Based on the channel state informations, the transmitter can adjust the channel coding scheme accordingly. Coherent channel and arbitrary channel symbols with a fixed average transmitted power constraint are assumed. The channel capacity and the error exponent are evaluated and the optimal rate control rules are found for Rayleigh fading channels with feedback of channel states. It is shown that the variable rate scheme can only increase the channel error exponent. The effects of additional practical constraints and finite feedback delays are also considered. Finally, we compare the performance of the variable rate adaptive channel coding in high bandwidth-expansion systems (CDMA) and high bandwidth-efficiency systems (TDMA).
TL;DR: It appears that uncoded filter-bank based MC transmission and single carrier transmission, both used over the same channel and with optimum DF, lead to the same achievable bit rate.
Abstract: We investigate the asymptotic performance of a multi-input multi-output decision-feedback (DF) equalizer used to detect a multicarrier (MC) signal based on a filter-bank and transmitted over a linear dispersive channel We derive the optimum DF structure for a minimum-mean square-error criterion We basically show that with infinite length forward and feedback filters and at high signal-to-noise ratio, the geometrical mean of prediction errors does not depend on the paraunitary filter-bank used in the transmitter Hence, it appears that uncoded filter-bank based MC transmission and single carrier transmission, both used over the same channel and with optimum DF, lead to the same achievable bit rate
24 Oct 1999
TL;DR: A new approach to adaptive spatio-temporal equalization for MIMO (multiple-input multiple-output) channels is proposed and a recursive solution using Riccati recursions is proposed.
Abstract: The purpose of this paper is to propose and investigate a new approach to adaptive spatio-temporal equalization for MIMO (multiple-input multiple-output) channels. A system with n transmit and m (n/spl ges/m) receiver antennas is assumed. An adaptive MIMO linear equalizer has been considered. For the considered equalizer a least squares solution is formulated, based on which a recursive solution using Riccati recursions is proposed. The solutions are tested by simulating the MIMO system. It is shown that the adaptive solutions will achieve the same performance as the optimum least squares solutions. The effect of the nondiagonal channel elements (acting as interference) on the system performance is also studied. It has been shown that in order to achieve better performance, the interference from nondiagonal channel elements needs to be minimized. This can be done by using orthogonal transmission. Moreover the proposed solutions do not require channel identification and will also enable equalizer adaptation to channel changes.
01 Jan 1999
TL;DR: In this paper, a methodology combining modal control theory and multiple input multiple output (MIMO) control theory is presented to simultaneously determine the locations and input signals for multiple static VAr compensators (SVCs) in order to damp multiple electromechanical oscillation modes in extensive power systems.
Abstract: This paper presents a methodology to simultaneously determine the locations and input signals for multiple static VAr compensators (SVCs) in order to damp multiple electromechanical oscillation modes in extensive power systems. This methodology combines modal control theory and multiple input multiple output (MIMO) control theory. Modal control theory indicates the sensitivity of a controller to the critical mode of interest, whilst MIMO control theory gives a measure of interactions caused by decentralized control. The usefulness of this methodology is illustrated on a 46 generator, 190 busbar, 253 circuit test power system.
17 Feb 1999
TL;DR: The basis of the approach is the design of a zero-forcing equalizer that whitens the noise-free data and allows infinite impulse response (IIR) channels and the multichannel transfer function need not be column-reduced.
Abstract: Channel estimation and blind equalization of MIMO (multiple-input multiple-output) communications channels is considered using primarily the second-order statistics of the data. We consider estimation of (partial) channel impulse response and design of finite-length MMSE (minimum mean-square error) blind equalizers. The basis of the approach is the design of a zero-forcing equalizer that whitens the noise-free data. We allow infinite impulse response (IIR) channels. Moreover, the multichannel transfer function need not be column-reduced. Our approaches also work when the "subchannel" transfer functions have common zeros so long as the common zeros are minimum-phase zeros. The channel length or model orders need not be known. The sources are recovered up to a unitary mixing matrix and are further 'unmixed" using higher-order statistics of the data. An illustrative simulation example is provided.
TL;DR: Two dynamical feedback controls are proposed in order to solve control tracking problems involving sliding manifolds by means of singular perturbation methods and an integral action is introduced to reject constant disturbances and follow constant references.
Abstract: By means of singular perturbation methods, the authors propose two dynamical feedback controls in order to solve control tracking problems involving sliding manifolds. The first control strategy introduces an integral action to reject constant disturbances and follow constant references. The second approach, in addition to the integral action, allows the designer to take into account limits on the maximum allowable control rate. Simulations on a multi-input/multi-output (MIMO) system are considered to show the effectiveness of the proposed approach and to discuss the choice of the parameters involved.
06 Jun 1999
TL;DR: A family of new MMSE blind channel equalization algorithms based on second order statistics are proposed, which can effectively equalize single-input multiple-output systems and can reduce the multiple-inputmultiple-output (MIMO) systems into a memoryless signal mixing system for source separation.
Abstract: A family of new MMSE blind channel equalization algorithms based on second order statistics are proposed. Instead of estimating the channel impulse response, we directly estimate the cross-correlation function needed in Wiener-Hopf filters. We develop several different schemes to estimate the cross-correlation vector, with which different Wiener filters are derived according to minimum mean square error (MMSE). Unlike many known subspace methods, these equalization algorithms do not rely on signal and noise subspace separation and are consequently more robust to channel order estimation errors. Their implementation requires no adjustment for either single or multiple user systems. They can effectively equalize single-input multiple-output (SIMO) systems and can reduce the multiple-input multiple-output (MIMO) systems into a memoryless signal mixing system for source separation. The implementations of these algorithms on SIMO system are given and simulation examples are provided to demonstrate their superior performance over some existing algorithms.
TL;DR: The random coding error exponent for the time-independent flat fading channel is derived with perfect knowledge of the channel state information (CSI) at both the receiver and the transmitter, which is feedback from the receiver to the transmitter.
Abstract: We derive the random coding error exponent for the time-independent flat fading channel with perfect knowledge of the channel state information (CSI) at both the receiver and the transmitter. That is, the CSI is feedback from the receiver to the transmitter. In such a situation, the transmitter is capable of optimizing the power allocation of the transmitted signal according to the fading state in order to obtain, for our case, the best error exponent. The power scheme obtained here is different from the water-pouring one, which is known to maximize the channel capacity.
15 Mar 1999
TL;DR: The basis of the approach is the design of a zero-forcing equalizer that whitens the noise-free data and allows infinite impulse response (IIR) channels and /spl Gamma/ the multichannel transfer function need not be column-reduced.
Abstract: Channel estimation and blind equalization of MIMO (multiple-input multiple-output) communications channels is considered using primarily the second-order statistics of the data. We consider estimation of (partial) channel impulse response and design of finite-length MMSE (minimum mean-square error) blind equalizers. The basis of the approach is the design of a zero-forcing equalizer that whitens the noise-free data. We allow infinite impulse response (IIR) channels. Moreover /spl Gamma/ the multichannel transfer function need not be column-reduced. Our approaches also work when the "subchannel" transfer functions have common zeros so long as the common zeros are minimum-phase zeros. The channel length or model orders need not be known. The sources are recovered up to a unitary mixing matrix and are further "unmixed" using higher-order statistics of the data. An illustrative simulation example is provided.
TL;DR: In this article, simulation results for the comparative performance of a number of space-time coding (STC) schemes in a multiple-input-multiple-output (MIMO) channel are presented.
Abstract: Simulation results for the comparative performance of a number of space-time coding (STC) schemes in a multiple-input-multiple-output (MIMO) channel are presented, and compared with a single-antenna benchmark and two-antenna space-time transit diversity (STTD) scheme. Both the space-time trellis coding (STTC) and BLAST approaches offer high spectral efficiencies, but STTC outperforms BLAST in terms of its power efficiency.
03 Sep 1999
TL;DR: It turned out that the method presented in this paper is computationally more efficient and gives more accurate models, however, sometimes the nonlinear optimization involved in the method does not converge to the global optimum and consequently the estimated model is bad.
Abstract: A subspace-based algorithm for the identification of discrete-time bilinear systems is presented. The algorithm uses a subspace-based step to estimate the order of the system and to generate initial estimates of the system matrices. These matrices are iteratively refined by numerically solving a nonlinear optimization problem. The principle of separable least squares is exploited, to make the algorithm computationally efficient. The method can deal with both process and measurement noise. By means of a Monte-Carlo simulation, the method is compared with another recently proposed subspace-based algorithm for bilinear systems. It turned out that the method presented in this paper is computationally more efficient and gives more accurate models. However, sometimes the nonlinear optimization involved in the method does not converge to the global optimum and consequently the estimated model is bad.
TL;DR: Simulation results show that the CAZE is not only effective for blind equalization of linear quadrature amplitude modulation (QAM) systems, but it is also applicable to the nonlinear GMSK modulation in the popular wireless GSM systems when computational cost severely limits the use of nonlinear methods such as the Viterbi algorithm.
Abstract: We propose a direct blind zeroforcing approach to cancel intersymbol interference (ISI) in multiple user finite impulse response (FIR) channels. By selectively anchoring columns of the channel convolution matrix, we present two column-anchored zeroforcing equalizers (CAZE), one without output delay and one with a chosen delay. Unlike many known blind identification algorithms, these equalizers do not need an accurate estimate of the channel orders. Exploiting second-order statistics (SOS) of the received signals, they can retain preselected d columns in the channel convolution matrix (d is the number of users) and force the remaining columns to zero. CAZE can effectively equalize single-input-multiple-output (SIMO) systems and can reduce dynamic multiple-input-multiple-output (MIMO) systems into a memoryless signal mixing system for source separation. Simulation results show that the CAZE is not only effective for blind equalization of linear quadrature amplitude modulation (QAM) systems, but it is also applicable to the nonlinear GMSK modulation in the popular wireless GSM systems when computational cost severely limits the use of nonlinear methods such as the Viterbi algorithm.
09 May 1999
TL;DR: Pre-filters can be applied to wireless communications for building a new multiple-access method potentially, by which multiple signals can be transmitted on the same narrow-band carrier simultaneously.
Abstract: By the use of pre-filters, the uncorrelated white source signals can be separated from an unknown MIMO (multiple-input-multiple-output) FIR channel based only on the second order statistics of the received signals. Precisely, if the white source signals are mutually uncorrelated, then a set of special pre-filters with order K can be designed so that the unknown MIMO FIR channel is equalized if, and only if, the output signals of the equalizer are mutually uncorrelated and K-step temporally uncorrelated. A method for designing such pre-filters is given. These results can be applied to wireless communications for building a new multiple-access method potentially, by which multiple signals can be transmitted on the same narrow-band carrier simultaneously.
AT&T1
TL;DR: Close-form expressions for computing the finite-length MIMO MMSE-DFE are presented for two common multi-user detection scenarios and quantifies the diversity performance improvement as a function of the number of transmit/receive antennas and equalizer taps.
Abstract: A new theoretical framework is introduced for analyzing the performance of a finite-length minimum mean square error decision feedback equalizer (MMSE-DFE) in a multi-input multi-output (MIMO) environment. The framework includes transmit and receive diversity systems as special cases and quantifies the diversity performance improvement as a function of the number of transmit/receive antennas and equalizer taps. Closed-form expressions for computing the finite-length MIMO MMSE-DFE are presented for two common multi-user detection scenarios.
05 Dec 1999
TL;DR: It is shown that the pre-RAKE maximises the correlation between the received and the desired signal, and this demonstration provides the means to obtain an instant power control at bit level that improves performance significantly.
Abstract: The pre-RAKE technique for the downlink transmission in TDD-based CDMA wireless systems has been shown to provide greater capacity and a simpler receiver design at the mobile receiver. Nevertheless this technique is very affected by fast changing channels, since it relies on uplink channel measurements for the downlink transmission. In this paper a semi-analytical approach to the performance, including channel coding is presented. Furthermore we analyse the pre-RAKE performance including its behaviour with changing channels. Finally we show that the pre-RAKE maximises the correlation between the received and the desired signal, and this demonstration provides us the means to obtain an instant power control at bit level that improves performance significantly.
02 Jun 1999
TL;DR: In this paper, the authors present an algorithm to identify MIMO discrete-time bilinear state space models from input-output measurements by optimizing an output error criterion, which depends linearly on some of the system matrices and nonlinearly on the others.
Abstract: We present an algorithm to identify MIMO discrete-time bilinear state space models from input-output measurements. We estimate the system matrices by optimizing an output error criterion. This criterion depends linearly on some of the system matrices and nonlinearly on the others. Using the principle of separable least squares, we first solve for the matrices that enter nonlinearly and then obtain the others by solving a linear least squares problem. It is pointed out that subspace-based techniques can be used to estimate the order of the system and to compute initial estimates of the matrices that enter the criterion in a nonlinear way. The algorithm has been tested on a MIMO simulation example.
TL;DR: In this article, the parity interlacing property of shift-invariant linear MIMO plants is generalized to the case of real one-dimensional MISO/SIMO plants.
Abstract: A plant is strongly stabilizable if there exists a stable compensator to stabilize it. Based on some theorems in complex analysis of several variables proved in this paper, we present necessary conditions for the strong stabilizability of complex and real n-D multi-input multi-output (MIMO) shift-invariant linear plants. For the real case, the condition is a generalization of the parity interlacing property of Youla, Bongiorno, and Lu [ Automatica J. IFAC, 10 (1974), pp. 159--173] for the strong stabilizability of a real one-dimensional MIMO plant.
These conditions are also sufficient for the cases of n-D plants with a single output (MISO) or with a single input (SIMO). For general n-D MIMO plants, we do not know if the conditions are sufficient or not. A useful sufficient, but not necessary, condition for the strong stabilizability of a class of n-D $(n\geq 2)$ MIMO plants is given.
01 Jan 1999
TL;DR: A spatial multipath model suitable for computer simulation is proposed in order to quantify the achievable performance in presence of arbitrary antenna correlation and results for different angular spread scenarios and power allocation strategies are presented.
Abstract: Recently, capacity studies for wireless multiple-input multiple-output (MIMO) channels have been performed. Significant gains have been forecasted for relatively high signal-to-noise ratios when using multiple antenna elements at both the transmitter and the receiver. However, most of these results have been obtained under antenna independence assumptions. In this paper, further insights on the effect of realistic antenna correlation values for small antenna spacings as a function of angular spread are provided. A spatial multipath model suitable for computer simulation is proposed in order to quantify the achievable performance in presence of arbitrary antenna correlation. Results for different angular spread scenarios and power allocation strategies are presented.
TL;DR: An optimal dynamic channel assignment algorithm for smart antennas that can deal with the Spatial Division Multiple Access (SDMA) and traditional channel multiple accesses simultaneously to enlarge the capacity of communication systems.
Abstract: The paper describes an optimal dynamic channel assignment algorithm for smart antennas. This algorithm can deal with the Spatial Division Multiple Access (SDMA) and traditional channel multiple accesses (FDMA, TDMA, or CDMA) simultaneously to enlarge the capacity of communication systems. This algorithm has several merits, including less computer time, the largest capacity, and avoidance of co-channel interference. The paper also describes the idea of a spatial channel pattern, in which several users can share a channel. Several simulation results are presented in the paper.
15 Mar 1999
TL;DR: This article follows the approach undertaken to consider the particular blind forward channel estimation problem, and improves quite significantly the results presented by Wang and Poor.
Abstract: Blind channel estimation for periodic sequence DS-CDMA systems can be cast into the framework of "structured" blind estimation of multi-input/multi-output (MIMO) FIR systems, where the structure is imposed by the user's signatures. A possible approach to tackle this problem consists in looking for a structured solution to one of the so-called "blind" MIMO-FIR system identification techniques proposed previously. This is the approach undertaken, among others, by Wang and Poor (see IEEE Trans. on Communications, vol.46, no.1, p.92-103, 1998), who proposed an adaptation of the subspace method originally developed by Moulines et al. (see IEEE Trans. on Signal Processing, vol.43, no.2, p.516-25, 1995) for single-input multiple outputs (SIMO) FIR systems, and later extended by Abed-Meraim et al. (see IEEE Trans. on Information Theory, vol.43, no.2, p.499-511, 1997) to MIMO-FIR systems. In this article, we follow this approach to consider the particular blind forward channel estimation problem, and improve quite significantly the results presented by Wang and Poor.