Results 11  20
of
264
MIMO wireless linear precoding
 IEEE Signal Processing Magazine
, 2006
"... The benefits of using multiple antennas at both the transmitter and the receiver in a wireless system are well established. Multipleinput multipleoutput (MIMO) systems enable a growth in transmission rate linear in the minimum of the number of antennas at either end [1][2]. MIMO techniques also en ..."
Abstract

Cited by 44 (0 self)
 Add to MetaCart
(Show Context)
The benefits of using multiple antennas at both the transmitter and the receiver in a wireless system are well established. Multipleinput multipleoutput (MIMO) systems enable a growth in transmission rate linear in the minimum of the number of antennas at either end [1][2]. MIMO techniques also enhance link reliability and
Capacityachieving input covariance for singleuser multiantenna channels
 IEEE Trans. Wireless Commun
, 2006
"... Abstract — We characterize the capacityachieving input covariance for multiantenna channels known instantaneously at the receiver and in distribution at the transmitter. Our characterization, valid for arbitrary numbers of antennas, encompasses both the eigenvectors and the eigenvalues. The eigenv ..."
Abstract

Cited by 40 (11 self)
 Add to MetaCart
Abstract — We characterize the capacityachieving input covariance for multiantenna channels known instantaneously at the receiver and in distribution at the transmitter. Our characterization, valid for arbitrary numbers of antennas, encompasses both the eigenvectors and the eigenvalues. The eigenvectors are found for zeromean channels with arbitrary fading profiles and a wide range of correlation and keyhole structures. For the eigenvalues, in turn, we present necessary and sufficient conditions as well as an iterative algorithm that exhibits remarkable properties: universal applicability, robustness and rapid convergence. In addition, we identify channel structures for which an isotropic input achieves capacity. Index Terms — Capacity, MIMO, input optimization, fading, antenna correlation, Ricean fading, keyhole channel.
Optimality of diagonalization of multihop MIMO relays
 IEEE Trans. Wireless Commun
"... Abstract—For a twohop linear nonregenerative multipleinput multipleoutput (MIMO) relay system where the direct link between source and destination is negligible, the optimal design of the source and relay matrices has been recently established for a broad class of objective functions. The optima ..."
Abstract

Cited by 39 (26 self)
 Add to MetaCart
(Show Context)
Abstract—For a twohop linear nonregenerative multipleinput multipleoutput (MIMO) relay system where the direct link between source and destination is negligible, the optimal design of the source and relay matrices has been recently established for a broad class of objective functions. The optimal source and relay matrices jointly diagonalize the MIMO relay system into a set of parallel scalar channels. In this paper, we show that this diagonalization is also optimal for a multihop MIMO relay system with any number of hops, which is a further generalization of several previously established results. Specifically, for Schurconcave objective functions, the optimal source precoding matrix, the optimal relay amplifying matrices and the optimal receiving matrix jointly diagonalize the multihop MIMO relay channel. And for Schurconvex objectives, such joint diagonalization along with a rotation of the source precoding matrix is also shown to be optimal. We also analyze the system performance when each node has the same transmission power budget and the same asymptotically large number of antennas. The asymptotic analysis shows a good agreement with numerical results under a finite number of antennas. Index Terms—MIMO relay network, multihop relay, linear nonregenerative relay, majorization.
Practical Algorithms for a Family of Waterfilling Solutions
 IEEE Trans. Signal Process
, 2005
"... Abstract—Many engineering problems that can be formulated as constrained optimization problems result in solutions given by a waterfilling structure; the classical example is the capacityachieving solution for a frequencyselective channel. For simple waterfilling solutions with a single waterleve ..."
Abstract

Cited by 39 (5 self)
 Add to MetaCart
(Show Context)
Abstract—Many engineering problems that can be formulated as constrained optimization problems result in solutions given by a waterfilling structure; the classical example is the capacityachieving solution for a frequencyselective channel. For simple waterfilling solutions with a single waterlevel and a single constraint (typically, a power constraint), some algorithms have been proposed in the literature to compute the solutions numerically. However, some other optimization problems result in significantly more complicated waterfilling solutions that include multiple waterlevels and multiple constraints. For such cases, it may still be possible to obtain practical algorithms to evaluate the solutions numerically but only after a painstaking inspection of the specific waterfilling structure. In addition, a unified view of the different types of waterfilling solutions and the corresponding practical algorithms is missing. The purpose of this paper is twofold. On the one hand, it overviews the waterfilling results existing in the literature from a unified viewpoint. On the other hand, it bridges the gap between a wide family of waterfilling solutions and their efficient implementation in practice; to be more precise, it provides a practical algorithm to evaluate numerically a general waterfilling solution, which includes the currently existing waterfilling solutions and others that may possibly appear in future problems. Index Terms—Constrained optimization problems, MIMO transceiver, parallel channels, practical algorithms, waterfilling, waterpouring. I.
BER criterion and codebook construction for finiterate precoded spatial multiplexing with linear receivers
 IEEE TRANS. SIGNAL PROCESS
, 2006
"... Precoded spatial multiplexing systems with ratelimited feedback have been studied recently based on various precoder selection criteria. Instead of those based on indirect performance indicators, we in this paper propose a new criterion directly based on the exact bit error rate (BER) that is appl ..."
Abstract

Cited by 33 (1 self)
 Add to MetaCart
(Show Context)
Precoded spatial multiplexing systems with ratelimited feedback have been studied recently based on various precoder selection criteria. Instead of those based on indirect performance indicators, we in this paper propose a new criterion directly based on the exact bit error rate (BER) that is applicable to systems with linear receivers and rectangular/square quadratureamplitudemodulation constellations. The BER criterion outperforms any other alternative in terms of optimizing the BER performance for an uncoded system with linear receivers. We then develop a precoder codebook construction method based on the generalized Lloyd algorithm from the vector quantization literature. This construction is not directly based on the BER criterion. Hence, it is suboptimal in the BER sense. However, relative to those currently available, our newfound codebooks improve considerably various minimum distances between any pair of codewords of the codebook. Finally, we analyze the BERoptimal precoder in the asymptotic case with infiniterate feedback that amounts to perfect channel knowledge at the transmitter. The infiniterate optimal precoder based on the BER criterion is drastically different from the counterparts with other criteria, and it leads to a benchmark performance for finiterate precoded spatial multiplexing systems. We observe from numerical results that the BER performance of finiterate feedback with suboptimal codebooks approaches quickly the benchmark performance of infiniterate feedback. This suggests that i) the number of feedback bits in practical systems need not be large and ii) the room for performance improvement via further codebook optimization shrinks quickly as the codebook size increases.
MIMO Gaussian Channels With Arbitrary Inputs: Optimal Precoding and Power Allocation
, 2010
"... In this paper, we investigate the linear precoding and power allocation policies that maximize the mutual information for general multipleinput–multipleoutput (MIMO) Gaussian channels with arbitrary input distributions, by capitalizing on the relationship between mutual information and minimum me ..."
Abstract

Cited by 30 (5 self)
 Add to MetaCart
(Show Context)
In this paper, we investigate the linear precoding and power allocation policies that maximize the mutual information for general multipleinput–multipleoutput (MIMO) Gaussian channels with arbitrary input distributions, by capitalizing on the relationship between mutual information and minimum meansquare error (MMSE). The optimal linear precoder satisfies a fixedpoint equation as a function of the channel and the input constellation. For nonGaussian inputs, a nondiagonal precoding matrix in general increases the information transmission rate, even for parallel noninteracting channels. Whenever precoding is precluded, the optimal power allocation policy also satisfies a fixedpoint equation; we put forth a generalization of the mercury/waterfilling algorithm, previously proposed for parallel noninterfering channels, in which the mercury level accounts not only for the nonGaussian input distributions, but also for the
MIMO multichannel beamforming: SER and outage using new eigenvalue distributions of complex noncentral Wishart matrices
 IEEE Transactions on Communications
, 2008
"... This paper analyzes MIMO systems with multichannel beamforming in Ricean fading. Our results apply to a wide class of multichannel systems which transmit on the eigenmodes of the MIMO channel. We first present new closedform expressions for the marginal ordered eigenvalue distributions of complex n ..."
Abstract

Cited by 28 (5 self)
 Add to MetaCart
(Show Context)
This paper analyzes MIMO systems with multichannel beamforming in Ricean fading. Our results apply to a wide class of multichannel systems which transmit on the eigenmodes of the MIMO channel. We first present new closedform expressions for the marginal ordered eigenvalue distributions of complex noncentral Wishart matrices. These are used to characterize the statistics of the signal to noise ratio (SNR) on each eigenmode. Based on this, we present exact symbol error rate (SER) expressions. We also derive closedform expressions for the diversity order, array gain, and outage probability. We show that the global SER performance is dominated by the subchannel corresponding to the minimum channel singular value. We also show that, at low outage levels, the outage probability varies inversely with the Ricean Kfactor for cases where transmission is only on the most dominant subchannel (i.e. a singlechannel beamforming system). Numerical results are presented to validate the theoretical analysis.
MIMO minimum total MSE transceiver design with imperfect CSI at both ends
 IEEE Trans. Signal Processing
, 2009
"... Abstract—This paper presents new results on joint linear transceiver design under the minimum total meansquare error (MSE) criterion, with channel mean as well as both transmit and receive correlation information at both ends of a multipleinput multipleoutput (MIMO) link. The joint design is form ..."
Abstract

Cited by 27 (3 self)
 Add to MetaCart
(Show Context)
Abstract—This paper presents new results on joint linear transceiver design under the minimum total meansquare error (MSE) criterion, with channel mean as well as both transmit and receive correlation information at both ends of a multipleinput multipleoutput (MIMO) link. The joint design is formulated into an optimization problem. The optimum closedform precoder and decoder are derived. Compared to the case with perfect channel state information (CSI), linear filters are added at both ends to balance the suppression of channel noise and the noise from imperfect channel estimation. The impact of channel estimation error as well as channel correlation on system performance is assessed, based on analytical and simulation results. Index Terms—Channel state information (CSI), meansquare error (MSE), multipleinput multipleoutput (MIMO), precoding, spatial multiplexing. I.
MIMO radar waveform design based on mutual information and minimum meansquare error estimation
 IEEE Transactions on Aerospace and Electronic Systems
, 2007
"... Abstract — This paper addresses the problem of radar waveform design for target identification and classification. Both the ordinary radar with a single transmitter and receiver and the recently proposed multipleinput multipleoutput (MIMO) radar are considered. A random target impulse response is ..."
Abstract

Cited by 26 (3 self)
 Add to MetaCart
(Show Context)
Abstract — This paper addresses the problem of radar waveform design for target identification and classification. Both the ordinary radar with a single transmitter and receiver and the recently proposed multipleinput multipleoutput (MIMO) radar are considered. A random target impulse response is used to model the scattering characteristics of the extended (nonpoint) target, and two radar waveform design problems with constraints on waveform power have been investigated. The first one is to design waveforms that maximize the conditional mutual information (MI) between the random target impulse response and the reflected waveforms given the knowledge of transmitted waveforms. The second one is to find transmitted waveforms that minimize the meansquare error (MSE) in estimating the target impulse response. Our analysis indicates that under the same total power constraint, these two criteria lead to the same solution for a matrix which specifies the essential part of the optimum waveform design. The solution employs waterfilling to allocate the limited power appropriately. We also present an asymptotic formulation which requires less knowledge of the statistical model of the target. Index Terms — Multipleinput multipleoutput (MIMO) radar, radar waveform design, identification, classification, extended radar targets, mutual information (MI), minimum meansquare error (MMSE), waveform diversity. I.
Robust beamforming for security in MIMO wiretap channels with imperfect CSI
 IEEE Trans. Signal Process
, 2011
"... Abstract—In this paper, we investigate methods for reducing the likelihood that a message transmitted between two multiantenna nodes is intercepted by an undetected eavesdropper. In particular, we focus on the judicious transmission of artificial interference to mask the desired signal at the time ..."
Abstract

Cited by 26 (4 self)
 Add to MetaCart
Abstract—In this paper, we investigate methods for reducing the likelihood that a message transmitted between two multiantenna nodes is intercepted by an undetected eavesdropper. In particular, we focus on the judicious transmission of artificial interference to mask the desired signal at the time it is broadcast. Unlike previous work that assumes some prior knowledge of the eavesdropper’s channel and focuses on maximizing secrecy capacity, we consider the case where no information regarding the eavesdropper is available, and we use signaltointerferenceplusnoiseratio (SINR) as our performance metric. Specifically, we focus on the problem of maximizing the amount of power available to broadcast a jamming signal intended to hide the desired signal from a potential eavesdropper, while maintaining a prespecified SINR at the desired receiver. The jamming signal is designed to be orthogonal to the information signal when it reaches the desired receiver, assuming both the receiver and the eavesdropper employ optimal beamformers and possess exact channel state information (CSI). In practice, the assumption of perfect CSI at the transmitter is often difficult to justify. Therefore, we also study the resulting performance degradation due to the presence of imperfect CSI, and we present robust beamforming schemes that recover a large fraction of the performance in the perfect CSI case. Numerical simulations verify our analytical performance predictions, and illustrate the benefit of the robust beamforming schemes. I.