MedWorm.com provides a medical RSS filtering service. Over 6000 RSS medical sources are combined and output via different filters. This feed contains the latest items from the 'IEEE Transactions on Signal Processing' source. Tue, 07 Feb 2012 07:42:49 +0100 http://www.medworm.com/index.php?rid=5657922&cid=s_38180_169_f&fid=38180&url=http%3A%2F%2Fieeexplore.ieee.org%2Fxpls%2Fabs_all.jsp%3Fisnumber%3D6126210%26arnumber%3D6051526 In this paper, we propose novel l1-regularized space-time adaptive processing (STAP) algorithms with a generalized sidelobe canceler architecture for airborne radar applications. The proposed methods suppose that a number of samples at the output of the blocking process are not needed for sidelobe canceling, which leads to the sparsity of the STAP filter weight vector. The core idea is to impose a sparse regularization (l1-norm type) to the minimum variance criterion. By solving this optimization problem, an l1-regularized recursive least squares (l1-based RLS) adaptive algorithm is developed. We also discuss the SINR steady-state performance and the penalty parameter setting of the proposed algorithm. To adaptively set the penalty parameter, two switched schemes are proposed for l1-based ... IEEE Transactions on Signal Processing journals http://www.medworm.com/rss/comments.php?id=5657922 Wed, 01 Feb 2012 05:00:00 +0100 5657922 http://www.medworm.com/index.php?rid=5605671&cid=s_38180_169_f&fid=38180&url=http%3A%2F%2Fieeexplore.ieee.org%2Fxpls%2Fabs_all.jsp%3Fisnumber%3D6126210%26arnumber%3D6126215 (Source: IEEE Transactions on Signal Processing) IEEE Transactions on Signal Processing journals http://www.medworm.com/rss/comments.php?id=5605671 Thu, 19 Jan 2012 13:01:45 +0100 5605671 http://www.medworm.com/index.php?rid=5605670&cid=s_38180_169_f&fid=38180&url=http%3A%2F%2Fieeexplore.ieee.org%2Fxpls%2Fabs_all.jsp%3Fisnumber%3D6126210%26arnumber%3D6126216 (Source: IEEE Transactions on Signal Processing) IEEE Transactions on Signal Processing journals http://www.medworm.com/rss/comments.php?id=5605670 Thu, 19 Jan 2012 13:01:45 +0100 5605670 http://www.medworm.com/index.php?rid=5605669&cid=s_38180_169_f&fid=38180&url=http%3A%2F%2Fieeexplore.ieee.org%2Fxpls%2Fabs_all.jsp%3Fisnumber%3D6126210%26arnumber%3D6126212 (Source: IEEE Transactions on Signal Processing) IEEE Transactions on Signal Processing journals http://www.medworm.com/rss/comments.php?id=5605669 Thu, 19 Jan 2012 13:01:45 +0100 5605669 http://www.medworm.com/index.php?rid=5605668&cid=s_38180_169_f&fid=38180&url=http%3A%2F%2Fieeexplore.ieee.org%2Fxpls%2Fabs_all.jsp%3Fisnumber%3D6126210%26arnumber%3D6126213 (Source: IEEE Transactions on Signal Processing) IEEE Transactions on Signal Processing journals http://www.medworm.com/rss/comments.php?id=5605668 Thu, 19 Jan 2012 13:01:45 +0100 5605668 http://www.medworm.com/index.php?rid=5605667&cid=s_38180_169_f&fid=38180&url=http%3A%2F%2Fieeexplore.ieee.org%2Fxpls%2Fabs_all.jsp%3Fisnumber%3D6126210%26arnumber%3D6064907 During the last decade, multiple-input multiple-ouput (MIMO) radar has received an increasing interest. One can find several estimation schemes in the literature related to the direction of arrivals and/or direction of departures, but their ultimate performance in terms of the statistical resolution limit (SRL) have not been fully investigated. In this correspondence, we fill this lack. Particulary, we derive the SRL to resolve two closely spaced targets in clutter interference using a MIMO radar with widely separated antennas. Toward this end, we use a hypothesis test formulation based on the generalized likelihood ratio test (GLRT). Furthermore, we investigate the link between the SRL and the minimum signal-to-noise ratio (SNR) required to resolve two closely spaced targets for a given p... IEEE Transactions on Signal Processing journals http://www.medworm.com/rss/comments.php?id=5605667 Thu, 19 Jan 2012 13:01:45 +0100 5605667 http://www.medworm.com/index.php?rid=5605666&cid=s_38180_169_f&fid=38180&url=http%3A%2F%2Fieeexplore.ieee.org%2Fxpls%2Fabs_all.jsp%3Fisnumber%3D6126210%26arnumber%3D6072308 Infinite impulse response (IIR) digital filters with prescribed magnitude and phase responses have been used in many applications. To approximate the prescribed magnitude and phase responses, we propose a new approach to the design of general IIR filters by minimizing the maximum phase error subject to a prescribed or simultaneously minimized maximum magnitude error, where the phase error and magnitude error are controlled by two elliptic constraints respectively with major and minor axes along the desired frequency response. The sequential constrained least-squares method and Levy–Sanathanan–Koerner strategy are used to convert the nonconvex constraints into convex ones, resulting in a series of convex optimization subproblems. Design examples and comparisons with recent met... IEEE Transactions on Signal Processing journals http://www.medworm.com/rss/comments.php?id=5605666 Thu, 19 Jan 2012 13:01:45 +0100 5605666 http://www.medworm.com/index.php?rid=5605665&cid=s_38180_169_f&fid=38180&url=http%3A%2F%2Fieeexplore.ieee.org%2Fxpls%2Fabs_all.jsp%3Fisnumber%3D6126210%26arnumber%3D6059517 In this correspondence, we analyze the effects of noisy links on the steady-state performance of diffusion least-mean-square (LMS) adaptive networks. Using the established weighted spatial-temporal energy conservation argument, we derive a variance relation which contains moments that represent the effects of noisy links. We evaluate these moments and derive closed-form expressions for the mean-square deviation (MSD), excess mean-square error (EMSE) and mean-square error (MSE) to explain the steady-state performance at each individual node. The derived expressions, supported by simulations, reveal that unlike the ideal link case, the steady-state MSD, EMSE, and MSE curves are not monotonically increasing functions of the step-size parameter when links are noisy. Moreover, the diffusion LMS... IEEE Transactions on Signal Processing journals http://www.medworm.com/rss/comments.php?id=5605665 Thu, 19 Jan 2012 13:01:45 +0100 5605665 http://www.medworm.com/index.php?rid=5605664&cid=s_38180_169_f&fid=38180&url=http%3A%2F%2Fieeexplore.ieee.org%2Fxpls%2Fabs_all.jsp%3Fisnumber%3D6126210%26arnumber%3D6061973 A fruitful approach for solving signal deconvolution problems consists of resorting to a frame-based convex variational formulation. In this context, parallel proximal algorithms and related alternating direction methods of multipliers have become popular optimization techniques to approximate iteratively the desired solution. Until now, in most of these methods, either Lipschitz differentiability properties or tight frame representations were assumed. In this paper, it is shown that it is possible to relax these assumptions by considering a class of non-necessarily tight frame representations, thus offering the possibility of addressing a broader class of signal restoration problems. In particular, it is possible to use non-necessarily maximally decimated filter banks with perfect reconst... IEEE Transactions on Signal Processing journals http://www.medworm.com/rss/comments.php?id=5605664 Thu, 19 Jan 2012 13:01:45 +0100 5605664 http://www.medworm.com/index.php?rid=5605663&cid=s_38180_169_f&fid=38180&url=http%3A%2F%2Fieeexplore.ieee.org%2Fxpls%2Fabs_all.jsp%3Fisnumber%3D6126210%26arnumber%3D6072273 Grid selection for sparse estimation of spectral-line parameters is a critical problem that was in need of a satisfactory solution: assuming the usual case of a uniform spectral grid how should one select the number of grid points, $K?$ We first present a simple practical rule for choosing an initial value (or initial values) of $K$ in a given situation. Then, we go on to explain how the estimation results corresponding to different values of $K$ can be compared with one another and therefore how to select the “best” value of $K$ among those considered. Furthermore, we introduce a method for detecting when a grid is “too rough” and for obtaining refined parameter estimates in such a case. (Source: IEEE Transactions on Signal Processing) IEEE Transactions on Signal Processing journals http://www.medworm.com/rss/comments.php?id=5605663 Thu, 19 Jan 2012 13:01:45 +0100 5605663 http://www.medworm.com/index.php?rid=5605662&cid=s_38180_169_f&fid=38180&url=http%3A%2F%2Fieeexplore.ieee.org%2Fxpls%2Fabs_all.jsp%3Fisnumber%3D6126210%26arnumber%3D6071014 This correspondence is concerned with network-based $H_{infty}$ filtering for discrete-time systems. The output signals of the system under consideration are transmitted to the filter through a constraint communication network, which usually leads to network-induced delays and packet dropouts. By introducing a logic data packet processor to choose the newest data signal from the network to actuate the filter, network-induced delays and packet dropouts are modeled as a Markov chain taking values in a finite set. As a result, the filter to be designed is modeled as a Markov jumping linear filter. By introducing some slack matrix variables in terms of probability identity, a less conservative bounded real lemma (BRL) is derived to ensure that the filtering error system is stochastically stabl... IEEE Transactions on Signal Processing journals http://www.medworm.com/rss/comments.php?id=5605662 Thu, 19 Jan 2012 13:01:45 +0100 5605662 http://www.medworm.com/index.php?rid=5605661&cid=s_38180_169_f&fid=38180&url=http%3A%2F%2Fieeexplore.ieee.org%2Fxpls%2Fabs_all.jsp%3Fisnumber%3D6126210%26arnumber%3D6060925 We propose a novel algorithm for the compression of ECG signals, in particular QRS complexes. The algorithm is based on the expansion of signals with compact support into a basis of discrete Hermite functions. These functions can be constructed by sampling continuous Hermite functions at specific sampling points. They form an orthogonal basis in the underlying signal space. The proposed algorithm relies on the theory of signal models based on orthogonal polynomials. We demonstrate that the constructed discrete Hermite functions have important advantages compared to continuous Hermite functions, which have previously been suggested for the compression of QRS complexes. Our algorithm achieves higher compression ratios compared with previously reported algorithms based on continuous Hermite f... IEEE Transactions on Signal Processing journals http://www.medworm.com/rss/comments.php?id=5605661 Thu, 19 Jan 2012 13:01:44 +0100 5605661 http://www.medworm.com/index.php?rid=5605660&cid=s_38180_169_f&fid=38180&url=http%3A%2F%2Fieeexplore.ieee.org%2Fxpls%2Fabs_all.jsp%3Fisnumber%3D6126210%26arnumber%3D6062691 This paper derives tight ergodic sum-rate capacity scaling limits for cognitive radio secondary networks under five different communication environments (CoE) for two different network types when secondary users' (SUs) transmission powers are optimally allocated. The network types studied are power-interference limited (PIL) networks and interference limited (IL) networks. In PIL networks, SUs' transmissions are limited by both an average total power constraint and a constraint on the average interference that they cause to primary users (PUs). In IL networks, SUs' transmissions are only limited by an average interference constraint. The capacity scaling results in PIL networks are derived for three different CoEs in which secondary transmitter to secondary base station (STSB) channel gain... IEEE Transactions on Signal Processing journals http://www.medworm.com/rss/comments.php?id=5605660 Thu, 19 Jan 2012 13:01:44 +0100 5605660 http://www.medworm.com/index.php?rid=5605659&cid=s_38180_169_f&fid=38180&url=http%3A%2F%2Fieeexplore.ieee.org%2Fxpls%2Fabs_all.jsp%3Fisnumber%3D6126210%26arnumber%3D6069883 In this paper, we propose and analyze a generalized construction of distributed network codes for a network consisting of $M$ users sending independent information to a common base station through independent block fading channels. The aim is to increase the diversity order of the system without reducing its throughput. The proposed scheme, called generalized dynamic-network codes (GDNC), is a generalization of the dynamic-network codes (DNC) recently proposed by Xiao and Skoglund. The design of the network codes that maximize the diversity order is recognized as equivalent to the design of linear block codes over a nonbinary finite field under the Hamming metric. We prove that adopting a systematic generator matrix of a maximum distance separable block code over a sufficiently large finit... IEEE Transactions on Signal Processing journals http://www.medworm.com/rss/comments.php?id=5605659 Thu, 19 Jan 2012 13:01:44 +0100 5605659 http://www.medworm.com/index.php?rid=5605658&cid=s_38180_169_f&fid=38180&url=http%3A%2F%2Fieeexplore.ieee.org%2Fxpls%2Fabs_all.jsp%3Fisnumber%3D6126210%26arnumber%3D6064911 The present paper is concerned with a sensor network, where each sensor is modeled by either a linear or nonlinear sensing system. These sensors team up in observing either static or dynamic random targets and transmit their observations through noisy communication channels to a fusion center (FC) for locating/tracking the targets. Physically, the network is limited by energy resource. According to the available sum power budget, we develop a novel technique for power allocation to the sensor nodes that enables the FC produce the best linear estimate in terms of the mean square error (MSE). Regardless of whether the sensor measurements are linear or nonlinear, the targets are scalar or vectors, static or dynamic, the corresponding optimization problems are shown to be semidefinite programs... IEEE Transactions on Signal Processing journals http://www.medworm.com/rss/comments.php?id=5605658 Thu, 19 Jan 2012 13:01:44 +0100 5605658 http://www.medworm.com/index.php?rid=5605657&cid=s_38180_169_f&fid=38180&url=http%3A%2F%2Fieeexplore.ieee.org%2Fxpls%2Fabs_all.jsp%3Fisnumber%3D6126210%26arnumber%3D6072310 This paper is concerned with distributed Kalman filtering for linear time-varying systems over multiagent sensor networks. We propose a diffusion Kalman filtering algorithm based on the covariance intersection method, where local estimates are fused by incorporating the covariance information of local Kalman filters. Our algorithm leads to a stable estimate for each agent regardless of whether the system is uniformly observable locally by the measurements of its neighbors which include the measurements of itself as long as the system is uniformly observable by the measurements of all the agents and the communication is sufficiently fast compared to the sampling. Simulation results validate the effectiveness of the proposed distributed Kalman filtering algorithm. (Source: IEEE Transactions ... IEEE Transactions on Signal Processing journals http://www.medworm.com/rss/comments.php?id=5605657 Thu, 19 Jan 2012 13:01:44 +0100 5605657 http://www.medworm.com/index.php?rid=5605656&cid=s_38180_169_f&fid=38180&url=http%3A%2F%2Fieeexplore.ieee.org%2Fxpls%2Fabs_all.jsp%3Fisnumber%3D6126210%26arnumber%3D6059514 We study the problem of minimizing the sum transmit power in mutliple-input multiple-output (MIMO) downlink channels with linear transceivers if per-user quality of service (QoS) constraints (expressed in terms of rates) have to be fulfilled. To find a suboptimal solution of the arising non-convex optimization problem, we introduce new auxiliary variables representing the division of the per-user rate constraints into per-stream rate targets, and we optimize these variables by means of gradient-projection steps. This new method is combined with alternating updates of the transmit and receive filters. Furthermore, the proposed algorithm ensures that the mean square error (MSE) matrices of all users are diagonal, and in the course of the execution of the algorithm, it is possible that inacti... IEEE Transactions on Signal Processing journals http://www.medworm.com/rss/comments.php?id=5605656 Thu, 19 Jan 2012 13:01:44 +0100 5605656 http://www.medworm.com/index.php?rid=5605655&cid=s_38180_169_f&fid=38180&url=http%3A%2F%2Fieeexplore.ieee.org%2Fxpls%2Fabs_all.jsp%3Fisnumber%3D6126210%26arnumber%3D6059515 We consider joint scheduling and diversity to enhance the benefits of multiuser diversity in an orthogonal frequency-division multiple access (OFDMA) downlink system. The OFDMA spectrum is assumed to consist of $N_{rm RB}$ resource blocks and the reduced feedback scheme consists of each user feeding back channel quality information (CQI) for only the best-$N_{rm FB}$ resource blocks. Assuming largest normalized CQI scheduling and a general value for $N_{rm FB}$, we develop a unified framework to analyze the sum rate of the system for both the quantized and nonquantized CQI feedback schemes. Based on this framework, we provide closed-form expressions for the sum rate for three different multiantenna transmitter schemes; transmit antenna selection (TAS), orthogonal space time block codes (OS... IEEE Transactions on Signal Processing journals http://www.medworm.com/rss/comments.php?id=5605655 Thu, 19 Jan 2012 13:01:44 +0100 5605655 http://www.medworm.com/index.php?rid=5605654&cid=s_38180_169_f&fid=38180&url=http%3A%2F%2Fieeexplore.ieee.org%2Fxpls%2Fabs_all.jsp%3Fisnumber%3D6126210%26arnumber%3D6072309 This paper deals with the fundamental limit of capacity for MIMO wireless systems with antenna mutual coupling. Motivated by practical considerations, the capacity-achieving precoder is found by maximizing the capacity subject to two separate power constraints; namely, a constraint on the available power at the transmitter which is imposed on a per-amplifier basis, and a constraint on the allowable radiated power. These two separate constraints occur because MIMO antenna systems are usually unable to use a perfect conjugate multiport impedance match in practice and therefore MIMO systems with mutual coupling usually do not radiate all of the power input or available to them. Assuming that perfect channel state information is available to both the transmitter and receiver, we first derive s... IEEE Transactions on Signal Processing journals http://www.medworm.com/rss/comments.php?id=5605654 Thu, 19 Jan 2012 13:01:44 +0100 5605654 http://www.medworm.com/index.php?rid=5605653&cid=s_38180_169_f&fid=38180&url=http%3A%2F%2Fieeexplore.ieee.org%2Fxpls%2Fabs_all.jsp%3Fisnumber%3D6126210%26arnumber%3D6059516 Optimization under multiple linear constraints is important for practical systems with individual power constraints, per-antenna power constraints, and/or interference constraints as in cognitive radios. While for single-user multiple-input multiple-output (MIMO) channel transmitter optimization, no one uses general purpose convex programming because water-filling is optimal and much simpler, it is not true for MIMO multiaccess channels (MAC), broadcast channels (BC), and the nonconvex optimization of interference networks because the traditional water-filling is far from optimal for networks. We recently found the right form of water-filling, polite water-filling, for capacity or achievable regions of the general MIMO interference networks, named B-MAC networks, which include BC, MAC, int... IEEE Transactions on Signal Processing journals http://www.medworm.com/rss/comments.php?id=5605653 Thu, 19 Jan 2012 13:01:44 +0100 5605653 http://www.medworm.com/index.php?rid=5605652&cid=s_38180_169_f&fid=38180&url=http%3A%2F%2Fieeexplore.ieee.org%2Fxpls%2Fabs_all.jsp%3Fisnumber%3D6126210%26arnumber%3D6059518 Equal gain transmission (EGT) requires only the feedback of phase information and is known to enjoy several implementational advantages compared to maximum ratio transmission (MRT). This paper investigates the use of lattice quantization for quantizing phases in EGT systems. In practice, the feedback rate is finite and the lattices need to be truncated to have finite code rate. The truncation of lattices results in boundary effect; hence, earlier results developed for untruncated lattices, e.g., fast algorithm and mean-square error (MSE) analysis, cannot be applied directly. Exploiting the fact that the quantized signals are phases, we show how to quantize using truncated lattices so that there is no boundary effect. Moreover, we propose efficient methods to convert between lattice codewor... IEEE Transactions on Signal Processing journals http://www.medworm.com/rss/comments.php?id=5605652 Thu, 19 Jan 2012 13:01:44 +0100 5605652 http://www.medworm.com/index.php?rid=5605651&cid=s_38180_169_f&fid=38180&url=http%3A%2F%2Fieeexplore.ieee.org%2Fxpls%2Fabs_all.jsp%3Fisnumber%3D6126210%26arnumber%3D6061974 Consider a $K$-user flat fading MIMO interference channel where the $k$th transmitter (or receiver) is equipped with $M_k$ (respectively $N_k$ ) antennas. If an exponential (in $K$) number of generic channel extensions are used either across time or frequency, Cadambe and Jafar showed that the total achievable degrees of freedom (DoF) can be maximized via interference alignment, resulting in a total DoF that grows linearly with $K$ even if $M_k$ and $N_k$ are bounded. In this work we consider the case where no channel extension is allowed, and establish a general condition that must be satisfied by any degrees of freedom tuple $(d_1,d_2,ldots,d_K)$ achievable through linear interference alignment. For a symmetric system with $M_k=M,$ $N_k=N,$ $d_k=d$ for all $k$, this condition implies tha... IEEE Transactions on Signal Processing journals http://www.medworm.com/rss/comments.php?id=5605651 Thu, 19 Jan 2012 13:01:44 +0100 5605651 http://www.medworm.com/index.php?rid=5605650&cid=s_38180_169_f&fid=38180&url=http%3A%2F%2Fieeexplore.ieee.org%2Fxpls%2Fabs_all.jsp%3Fisnumber%3D6126210%26arnumber%3D6069882 Multiple distributed nodes in cooperative networks generally are subject to multiple carrier frequency offsets (MCFOs) and multiple timing offsets (MTOs), which result in time varying channels and erroneous decoding. This paper seeks to develop estimation and detection algorithms that enable cooperative communications for both decode-and-forward (DF) and amplify-and-forward (AF) relaying networks in the presence of MCFOs, MTOs, and unknown channel gains. A novel transceiver structure at the relays for achieving synchronization in AF-relaying networks is proposed. New exact closed-form expressions for the Cramér–Rao lower bounds (CRLBs) for the multi-parameter estimation problem are derived. Next, two iterative algorithms based on the expectation conditional maximization (ECM)... IEEE Transactions on Signal Processing journals http://www.medworm.com/rss/comments.php?id=5605650 Thu, 19 Jan 2012 13:01:44 +0100 5605650 http://www.medworm.com/index.php?rid=5605649&cid=s_38180_169_f&fid=38180&url=http%3A%2F%2Fieeexplore.ieee.org%2Fxpls%2Fabs_all.jsp%3Fisnumber%3D6126210%26arnumber%3D6069880 This paper considers the spectrum sharing multiple-input–multiple-output (MIMO) cognitive radio network, in which multiple primary users (PUs) coexist with multiple secondary users (SUs). Joint transceiver cognitive beam former design is introduced to minimize the transmit power of the SU base station (SBS) while simultaneously targeting lower bounds on the received signal-to-interference-plus-noise ratio (SINR) for the SUs and imposing upper limits on the interference temperature to the PUs. With the perfect knowledge of all links, the optimal secondary transceiver beam former is achieved iteratively. Due to the limited cooperation between SBS and PUs, perfect information of primary links may not be available at SBS which could lead to severe interference to the PUs. Robust designs... IEEE Transactions on Signal Processing journals http://www.medworm.com/rss/comments.php?id=5605649 Thu, 19 Jan 2012 13:01:44 +0100 5605649 http://www.medworm.com/index.php?rid=5605648&cid=s_38180_169_f&fid=38180&url=http%3A%2F%2Fieeexplore.ieee.org%2Fxpls%2Fabs_all.jsp%3Fisnumber%3D6126210%26arnumber%3D6062692 This paper presents new linear time-invariant (LTI) block-based transceivers which employ a reduced amount of redundancy to eliminate the interblock interference. The proposals encompass both multicarrier and single-carrier systems with either zero-forcing or minimum mean-square error (MSE) equalizers. The amount of redundancy ranges from the minimum, $lceil{Lover 2}rceil$, to the most commonly used value, $L$, assuming a channel-impulse response of order $L$. The resulting transceivers allow for superfast equalization of the received data blocks, since they only use fast Fourier transforms and single-tap equalizers in their structures. The paper also includes an MSE analysis of the proposed transceivers with respect to the amount of redundancy. Indeed, we demonstrate that larger amounts o... IEEE Transactions on Signal Processing journals http://www.medworm.com/rss/comments.php?id=5605648 Thu, 19 Jan 2012 13:01:44 +0100 5605648 http://www.medworm.com/index.php?rid=5605647&cid=s_38180_169_f&fid=38180&url=http%3A%2F%2Fieeexplore.ieee.org%2Fxpls%2Fabs_all.jsp%3Fisnumber%3D6126210%26arnumber%3D6062694 In this paper, the problem of joint carrier frequency offset (CFO) and channel estimation for OFDM systems over the fast time-varying frequency-selective channel is explored within the framework of the expectation-maximization (EM) algorithm and parametric channel model. Assuming that the path delays are known, a novel iterative pilot-aided algorithm for joint estimation of the multipath Rayleigh channel complex gains (CG) and the carrier frequency offset (CFO) is introduced. Each CG time-variation, within one OFDM symbol, is approximated by a basis expansion model (BEM) representation. An autoregressive (AR) model is built to statistically characterize the variations of the BEM coefficients across the OFDM blocks. In addition to the algorithm, the derivation of the hybrid Cramér-Ra... IEEE Transactions on Signal Processing journals http://www.medworm.com/rss/comments.php?id=5605647 Thu, 19 Jan 2012 13:01:44 +0100 5605647 http://www.medworm.com/index.php?rid=5605646&cid=s_38180_169_f&fid=38180&url=http%3A%2F%2Fieeexplore.ieee.org%2Fxpls%2Fabs_all.jsp%3Fisnumber%3D6126210%26arnumber%3D6064910 Over the last decade, several set-based worst-case beamformers have been proposed. It has been shown that some of these beamformers can be formulated equivalently as one-dimensional (1D) covariance fitting problems. Based on this formulation, we show that these beamformers lead to inherently nonoptimum results in the presence of interferers. To mitigate the detrimental effect of interferers, we extend the 1D covariance fitting approach to multidimensional (MD) covariance fitting, modeling the source steering vectors by means of uncertainty sets. The proposed MD covariance fitting approach leads to a nonconvex optimization problem. We develop a convex approximation of this problem, which can be solved, for example, by means of the logarithmic barrier method. The complexity required to compu... IEEE Transactions on Signal Processing journals http://www.medworm.com/rss/comments.php?id=5605646 Thu, 19 Jan 2012 13:01:44 +0100 5605646 http://www.medworm.com/index.php?rid=5605645&cid=s_38180_169_f&fid=38180&url=http%3A%2F%2Fieeexplore.ieee.org%2Fxpls%2Fabs_all.jsp%3Fisnumber%3D6126210%26arnumber%3D6064909 Compressive sensing and processing handles high-resolution delay-Doppler radar measurements using a low sampling rate, simple receiver design, and inexpensive processing when Nyquist rate sensing and processing becomes impractical. The benefits of compressive sensing and processing are, however, offset by an increase in estimation error that is introduced when processing compressed measurements versus measurements sampled at the Nyquist rate. In this work, an adaptive compressive sensing and processing method is proposed for the radar tracking problem. The adaptive scheme naturally incorporates information on target state that is readily available from a particle filter based tracker. The proposed method is shown to improve tracking performance over nonadaptive compressive sensing and proc... IEEE Transactions on Signal Processing journals http://www.medworm.com/rss/comments.php?id=5605645 Thu, 19 Jan 2012 13:01:43 +0100 5605645 http://www.medworm.com/index.php?rid=5605644&cid=s_38180_169_f&fid=38180&url=http%3A%2F%2Fieeexplore.ieee.org%2Fxpls%2Fabs_all.jsp%3Fisnumber%3D6126210%26arnumber%3D6095653 We propose a cognitive radar network (CRN) system for the joint estimation of the target state comprising the positions and velocities of multiple targets, and the channel state comprising the propagation conditions of an urban transmission channel. We develop a measurement model for the received signal by considering a finite-dimensional representation of the time-varying system function which characterizes the urban transmission channel. We employ sequential Bayesian filtering at the receiver to estimate the target and the channel state. We propose a hybrid Bayesian filter that operates by partitioning the state space into smaller subspaces and thereby reducing the complexity involved with high-dimensional state space. The feedback loop that embodies the radar environment and the receive... IEEE Transactions on Signal Processing journals http://www.medworm.com/rss/comments.php?id=5605644 Thu, 19 Jan 2012 13:01:43 +0100 5605644 http://www.medworm.com/index.php?rid=5605643&cid=s_38180_169_f&fid=38180&url=http%3A%2F%2Fieeexplore.ieee.org%2Fxpls%2Fabs_all.jsp%3Fisnumber%3D6126210%26arnumber%3D6074956 This paper formulates and solves a sequential detection problem that involves the mutual information (stochastic observability) of a Gaussian process observed in noise with missing measurements. The main result is that the optimal decision is characterized by a monotone policy on the partially ordered set of positive definite covariance matrices. This monotone structure implies that numerically efficient algorithms can be designed to estimate and implement monotone parametrized decision policies. The sequential detection problem is motivated by applications in radar scheduling where the aim is to maintain the mutual information of all targets within a specified bound. We illustrate the problem formulation and performance of monotone parametrized policies via numerical examples in fly-by an... IEEE Transactions on Signal Processing journals http://www.medworm.com/rss/comments.php?id=5605643 Thu, 19 Jan 2012 13:01:43 +0100 5605643 http://www.medworm.com/index.php?rid=5605642&cid=s_38180_169_f&fid=38180&url=http%3A%2F%2Fieeexplore.ieee.org%2Fxpls%2Fabs_all.jsp%3Fisnumber%3D6126210%26arnumber%3D6025317 The interaction between a smart target and a smart MIMO radar is investigated from a game theory perspective. Since the target and the radar form an adversarial system, their interaction is modeled as a two-person zero-sum game. The mutual information criterion is used in formulating the utility functions. The unilateral, hierarchical, and symmetric games are studied, and the equilibria solutions are derived. (Source: IEEE Transactions on Signal Processing) IEEE Transactions on Signal Processing journals http://www.medworm.com/rss/comments.php?id=5605642 Thu, 19 Jan 2012 13:01:43 +0100 5605642 http://www.medworm.com/index.php?rid=5605641&cid=s_38180_169_f&fid=38180&url=http%3A%2F%2Fieeexplore.ieee.org%2Fxpls%2Fabs_all.jsp%3Fisnumber%3D6126210%26arnumber%3D6051526 In this paper, we propose novel $l_1$-regularized space-time adaptive processing (STAP) algorithms with a generalized sidelobe canceler architecture for airborne radar applications. The proposed methods suppose that a number of samples at the output of the blocking process are not needed for sidelobe canceling, which leads to the sparsity of the STAP filter weight vector. The core idea is to impose a sparse regularization ($l_1$ -norm type) to the minimum variance criterion. By solving this optimization problem, an $l_1$-regularized recursive least squares ( $l_1$-based RLS) adaptive algorithm is developed. We also discuss the SINR steady-state performance and the penalty parameter setting of the proposed algorithm. To adaptively set the penalty parameter, two switched schemes are proposed... IEEE Transactions on Signal Processing journals http://www.medworm.com/rss/comments.php?id=5605641 Thu, 19 Jan 2012 13:01:43 +0100 5605641 http://www.medworm.com/index.php?rid=5605640&cid=s_38180_169_f&fid=38180&url=http%3A%2F%2Fieeexplore.ieee.org%2Fxpls%2Fabs_all.jsp%3Fisnumber%3D6126210%26arnumber%3D6072307 This paper presents a novel algorithm for the automatic 3D localization of a set of sensors in an unknown environment. Given the measures of a set of time of arrival delays at each sensor, the approach simultaneously estimates the 3D position of the sensors and the sources that have generated the event. Such inference is obtained with no assumption about the sensor localization; the only assumption made is that the emission time of the sources must be known in order to evaluate the time of flight for each event. Moreover, we propose a further method that deals with the likely case of missing data in the measurements. This occurs when sensors are far apart or behind natural barriers that avoids the registration of the given event. Simulated experiments show the validity of the approach for ... IEEE Transactions on Signal Processing journals http://www.medworm.com/rss/comments.php?id=5605640 Thu, 19 Jan 2012 13:01:43 +0100 5605640 http://www.medworm.com/index.php?rid=5605639&cid=s_38180_169_f&fid=38180&url=http%3A%2F%2Fieeexplore.ieee.org%2Fxpls%2Fabs_all.jsp%3Fisnumber%3D6126210%26arnumber%3D6062424 Many signal processing problems are tackled by filtering the signal for subsequent feature classification or regression. Both steps are critical and need to be designed carefully to deal with the particular statistical characteristics of both signal and noise. Optimal design of the filter and the classifier are typically aborded in a separated way, thus leading to suboptimal classification schemes. This paper proposes an efficient methodology to learn an optimal signal filter and a support vector machine (SVM) classifier jointly. In particular, we derive algorithms to solve the optimization problem, prove its theoretical convergence, and discuss different filter regularizers for automated scaling and selection of the feature channels. The latter gives rise to different formulations with th... IEEE Transactions on Signal Processing journals http://www.medworm.com/rss/comments.php?id=5605639 Thu, 19 Jan 2012 13:01:43 +0100 5605639 http://www.medworm.com/index.php?rid=5605638&cid=s_38180_169_f&fid=38180&url=http%3A%2F%2Fieeexplore.ieee.org%2Fxpls%2Fabs_all.jsp%3Fisnumber%3D6126210%26arnumber%3D6062423 In this paper, we improve iterative greedy search algorithms in which atoms are selected serially over iterations, i.e., one-by-one over iterations. For serial atom selection, we devise two new schemes to select an atom from a set of potential atoms in each iteration. The two new schemes lead to two new algorithms. For both the algorithms, in each iteration, the set of potential atoms is found using a standard matched filter. In case of the first scheme, we propose an orthogonal projection strategy that selects an atom from the set of potential atoms. Then, for the second scheme, we propose a look-ahead strategy such that the selection of an atom in the current iteration has an effect on the future iterations. The use of look-ahead strategy requires a higher computational resource. To achi... IEEE Transactions on Signal Processing journals http://www.medworm.com/rss/comments.php?id=5605638 Thu, 19 Jan 2012 13:01:43 +0100 5605638 http://www.medworm.com/index.php?rid=5605637&cid=s_38180_169_f&fid=38180&url=http%3A%2F%2Fieeexplore.ieee.org%2Fxpls%2Fabs_all.jsp%3Fisnumber%3D6126210%26arnumber%3D6071015 In this paper, we investigate the problem of designing compact-support interpolation kernels for a given class of signals. By using calculus of variations, we simplify the optimization problem from an nonlinear infinite dimensional problem to a linear finite dimensional case, and then find the optimum compact-support function that best approximates a given filter in the least square sense ($ell_{2}$ norm). The benefit of compact-support interpolants is the low computational complexity in the interpolation process while the optimum compact-support interpolant guarantees the highest achievable signal-to-noise ratio (SNR). Our simulation results confirm the superior performance of the proposed kernel compared to other conventional compact-support interpolants such as cubic spline. (Source: IE... IEEE Transactions on Signal Processing journals http://www.medworm.com/rss/comments.php?id=5605637 Thu, 19 Jan 2012 13:01:43 +0100 5605637 http://www.medworm.com/index.php?rid=5605636&cid=s_38180_169_f&fid=38180&url=http%3A%2F%2Fieeexplore.ieee.org%2Fxpls%2Fabs_all.jsp%3Fisnumber%3D6126210%26arnumber%3D6072311 We present methods for computing optimal solutions which are guaranteed to be stable and causal. Detailed comparisons to alternative methods are provided. We discuss some applications in sound and image reconstruction. (Source: IEEE Transactions on Signal Processing) IEEE Transactions on Signal Processing journals http://www.medworm.com/rss/comments.php?id=5605636 Thu, 19 Jan 2012 13:01:43 +0100 5605636 http://www.medworm.com/index.php?rid=5605635&cid=s_38180_169_f&fid=38180&url=http%3A%2F%2Fieeexplore.ieee.org%2Fxpls%2Fabs_all.jsp%3Fisnumber%3D6126210%26arnumber%3D6061972 The concept of a common modulated oscillation spanning multiple time series is formalized, a method for the recovery of such a signal from potentially noisy observations is proposed, and the time-varying bias properties of the recovery method are derived. The method, an extension of wavelet ridge analysis to the multivariate case, identifies the common oscillation by seeking, at each point in time, a frequency for which a bandpassed version of the signal obtains a local maximum in power. The lowest-order bias is shown to involve a quantity, termed the instantaneous curvature, which measures the strength of local quadratic modulation of the signal after demodulation by the common oscillation frequency. The bias can be made to be small if the analysis filter, or wavelet, can be chosen such t... IEEE Transactions on Signal Processing journals http://www.medworm.com/rss/comments.php?id=5605635 Thu, 19 Jan 2012 13:01:43 +0100 5605635 http://www.medworm.com/index.php?rid=5605634&cid=s_38180_169_f&fid=38180&url=http%3A%2F%2Fieeexplore.ieee.org%2Fxpls%2Fabs_all.jsp%3Fisnumber%3D6126210%26arnumber%3D6062693 In this paper the problem of semisupervised hyperspectral unmixing is considered. More specifically, the unmixing process is formulated as a linear regression problem, where the abundance's physical constraints are taken into account. Based on this formulation, a novel hierarchical Bayesian model is proposed and suitable priors are selected for the model parameters such that, on the one hand, they ensure the nonnegativity of the abundances, while on the other hand they favor sparse solutions for the abundances' vector. Performing Bayesian inference based on the proposed hierarchical Bayesian model, a new low-complexity iterative method is derived, and its connection with Gibbs sampling and variational Bayesian inference is highlighted. Experimental results on both synthetic and real hypers... IEEE Transactions on Signal Processing journals http://www.medworm.com/rss/comments.php?id=5605634 Thu, 19 Jan 2012 13:01:43 +0100 5605634 http://www.medworm.com/index.php?rid=5605633&cid=s_38180_169_f&fid=38180&url=http%3A%2F%2Fieeexplore.ieee.org%2Fxpls%2Fabs_all.jsp%3Fisnumber%3D6126210%26arnumber%3D6072274 We study the problem of joint quantization and power allocation in wireless sensor networks where spatially distributed sensors observe a Gaussian random source, quantize the resulting noisy observations, and transmit over orthogonal fading channels to a remote fusion center (FC). The role of the FC is to reconstruct the source with minimal distortion using linear minimum mean square error estimation rule. In this paper, we undertake the design of joint quantization and power allocation based on the following optimization problem: minimize the reconstruction distortion for a given total network power consumption. To address this problem, at each sensor node uniform scalar quantization is assumed. Moreover, assuming pseudo-quantization noise model we show that the problem can be solved usin... IEEE Transactions on Signal Processing journals http://www.medworm.com/rss/comments.php?id=5605633 Thu, 19 Jan 2012 13:01:43 +0100 5605633 http://www.medworm.com/index.php?rid=5605632&cid=s_38180_169_f&fid=38180&url=http%3A%2F%2Fieeexplore.ieee.org%2Fxpls%2Fabs_all.jsp%3Fisnumber%3D6126210%26arnumber%3D6064908 This paper deals with the detection of hidden bits in the Least Significant Bit (LSB) plane of a natural image. The mean level and the covariance matrix of the image, considered as a quantized Gaussian random matrix, are unknown. An adaptive statistical test is designed such that its probability distribution is always independent of the unknown image parameters, while ensuring a high probability of hidden bits detection. This test is based on the likelihood ratio test except that the unknown parameters are replaced by estimates based on a local linear regression model. It is shown that this test maximizes the probability of detection as the image size becomes arbitrarily large and the quantization step vanishes. This provides an asymptotic upper-bound for the detection of hidden bits based... IEEE Transactions on Signal Processing journals http://www.medworm.com/rss/comments.php?id=5605632 Thu, 19 Jan 2012 13:01:43 +0100 5605632 http://www.medworm.com/index.php?rid=5605631&cid=s_38180_169_f&fid=38180&url=http%3A%2F%2Fieeexplore.ieee.org%2Fxpls%2Fabs_all.jsp%3Fisnumber%3D6126210%26arnumber%3D6051522 The unscented Kalman filter (UKF) has become a popular alternative to the extended Kalman filter (EKF) during the last decade. UKF propagates the so called sigma points by function evaluations using the unscented transformation (UT), and this is at first glance very different from the standard EKF algorithm which is based on a linearized model. The claimed advantages with UKF are that it propagates the first two moments of the posterior distribution and that it does not require gradients of the system model. We point out several less known links between EKF and UKF in terms of two conceptually different implementations of the Kalman filter: the standard one based on the discrete Riccati equation, and one based on a formula on conditional expectations that does not involve an explicit Ricca... IEEE Transactions on Signal Processing journals http://www.medworm.com/rss/comments.php?id=5605631 Thu, 19 Jan 2012 13:01:43 +0100 5605631 http://www.medworm.com/index.php?rid=5605630&cid=s_38180_169_f&fid=38180&url=http%3A%2F%2Fieeexplore.ieee.org%2Fxpls%2Fabs_all.jsp%3Fisnumber%3D6126210%26arnumber%3D6126214 (Source: IEEE Transactions on Signal Processing) IEEE Transactions on Signal Processing journals http://www.medworm.com/rss/comments.php?id=5605630 Thu, 19 Jan 2012 13:01:43 +0100 5605630 http://www.medworm.com/index.php?rid=5605629&cid=s_38180_169_f&fid=38180&url=http%3A%2F%2Fieeexplore.ieee.org%2Fxpls%2Fabs_all.jsp%3Fisnumber%3D6126210%26arnumber%3D6126211 (Source: IEEE Transactions on Signal Processing) IEEE Transactions on Signal Processing journals http://www.medworm.com/rss/comments.php?id=5605629 Thu, 19 Jan 2012 13:01:42 +0100 5605629 http://www.medworm.com/index.php?rid=5521916&cid=s_38180_169_f&fid=38180&url=http%3A%2F%2Fieeexplore.ieee.org%2Fxpls%2Fabs_all.jsp%3Fisnumber%3D6104236%26arnumber%3D6104239 (Source: IEEE Transactions on Signal Processing) IEEE Transactions on Signal Processing journals http://www.medworm.com/rss/comments.php?id=5521916 Wed, 21 Dec 2011 00:25:05 +0100 5521916 http://www.medworm.com/index.php?rid=5521915&cid=s_38180_169_f&fid=38180&url=http%3A%2F%2Fieeexplore.ieee.org%2Fxpls%2Fabs_all.jsp%3Fisnumber%3D6104236%26arnumber%3D6104241 (Source: IEEE Transactions on Signal Processing) IEEE Transactions on Signal Processing journals http://www.medworm.com/rss/comments.php?id=5521915 Wed, 21 Dec 2011 00:25:05 +0100 5521915 http://www.medworm.com/index.php?rid=5521914&cid=s_38180_169_f&fid=38180&url=http%3A%2F%2Fieeexplore.ieee.org%2Fxpls%2Fabs_all.jsp%3Fisnumber%3D6104236%26arnumber%3D6104240 (Source: IEEE Transactions on Signal Processing) IEEE Transactions on Signal Processing journals http://www.medworm.com/rss/comments.php?id=5521914 Wed, 21 Dec 2011 00:25:05 +0100 5521914 http://www.medworm.com/index.php?rid=5521913&cid=s_38180_169_f&fid=38180&url=http%3A%2F%2Fieeexplore.ieee.org%2Fxpls%2Fabs_all.jsp%3Fisnumber%3D6104236%26arnumber%3D6104275 (Source: IEEE Transactions on Signal Processing) IEEE Transactions on Signal Processing journals http://www.medworm.com/rss/comments.php?id=5521913 Wed, 21 Dec 2011 00:25:05 +0100 5521913 http://www.medworm.com/index.php?rid=5521912&cid=s_38180_169_f&fid=38180&url=http%3A%2F%2Fieeexplore.ieee.org%2Fxpls%2Fabs_all.jsp%3Fisnumber%3D6104236%26arnumber%3D6104237 (Source: IEEE Transactions on Signal Processing) IEEE Transactions on Signal Processing journals http://www.medworm.com/rss/comments.php?id=5521912 Wed, 21 Dec 2011 00:25:05 +0100 5521912 http://www.medworm.com/index.php?rid=5521911&cid=s_38180_169_f&fid=38180&url=http%3A%2F%2Fieeexplore.ieee.org%2Fxpls%2Fabs_all.jsp%3Fisnumber%3D6104236%26arnumber%3D6035800 We derive and analyze two modified Kalman channel estimators (KCE) for time-varying, flat, spatially correlated MIMO channels in systems employing orthogonal space-time block codes: the steady-state KCE, which is less complex than the KCE, and the fading memory KCE, which is more robust to model mismatch. (Source: IEEE Transactions on Signal Processing) IEEE Transactions on Signal Processing journals http://www.medworm.com/rss/comments.php?id=5521911 Wed, 21 Dec 2011 00:25:05 +0100 5521911 http://www.medworm.com/index.php?rid=5521910&cid=s_38180_169_f&fid=38180&url=http%3A%2F%2Fieeexplore.ieee.org%2Fxpls%2Fabs_all.jsp%3Fisnumber%3D6104236%26arnumber%3D6026260 We consider a robust downlink beamforming optimization problem for secondary multicast transmission in a multiple-input multiple-output (MIMO) spectrum sharing cognitive radio (CR) network. The minimization of transmit power is formulated subject to both quality-of-service (QoS) constraints on the secondary receivers and interference temperature constraints on the primary users, under the assumption of imperfect channel state information (CSI). The problem is a nonconvex quadratically constrained quadratic program (QCQP), and in general it is hard to achieve the global optimality. As a compromise, we present two randomized approximation algorithms for the problem via convex optimization techniques. Apart from the general setting of the robust beamforming problem, we identify one interestin... IEEE Transactions on Signal Processing journals http://www.medworm.com/rss/comments.php?id=5521910 Wed, 21 Dec 2011 00:25:05 +0100 5521910 http://www.medworm.com/index.php?rid=5521909&cid=s_38180_169_f&fid=38180&url=http%3A%2F%2Fieeexplore.ieee.org%2Fxpls%2Fabs_all.jsp%3Fisnumber%3D6104236%26arnumber%3D6045353 Recently, it has been proved in Babadi [B. Babadi, N. Kalouptsidis, and V. Tarokh, “Asymptotic achievability of the Cramér–Rao bound for noisy compressive sampling,” IEEE Trans. Signal Process., vol. 57, no. 3, pp. 1233–1236, 2009] that in noisy compressed sensing, a joint typical estimator can asymptotically achieve the Cramér–Rao lower bound of the problem. To prove this result, Babadi used a lemma, which is provided in Akçakaya and Tarokh [M. Akçakaya and V. Trarokh, “Shannon theoretic limits on noisy compressive sampling,” IEEE Trans. Inf. Theory, vol. 56, no. 1, pp. 492–504, 2010] that comprises the main building block of the proof. This lemma is based on the assumption of Gaussianity of the measuremen... IEEE Transactions on Signal Processing journals http://www.medworm.com/rss/comments.php?id=5521909 Wed, 21 Dec 2011 00:25:04 +0100 5521909 http://www.medworm.com/index.php?rid=5521908&cid=s_38180_169_f&fid=38180&url=http%3A%2F%2Fieeexplore.ieee.org%2Fxpls%2Fabs_all.jsp%3Fisnumber%3D6104236%26arnumber%3D6026259 In a previous work, we have developed a low-rank (LR) spatio-temporal adaptive processing (STAP) filter when the disturbance is modeled as the sum of a low-rank spherically invariant random vector (SIRV) clutter and a zero-mean white Gaussian noise. This LR-STAP filter is built from the normalized sample covariance matrix (NSCM) and exhibits good robustness properties to secondary data contamination by target components. In this correspondence, we derive the bias of the NSCM with this noise model. We show that the eigenvectors estimated from the NSCM are unbiased. The new expressions of the expectation of NSCM eigenvalues are also given. From these results, we also show that the estimate of the clutter subspace projector based on the NSCM used in our LR-STAP is a consistent estimate of the... IEEE Transactions on Signal Processing journals http://www.medworm.com/rss/comments.php?id=5521908 Wed, 21 Dec 2011 00:25:04 +0100 5521908 http://www.medworm.com/index.php?rid=5521907&cid=s_38180_169_f&fid=38180&url=http%3A%2F%2Fieeexplore.ieee.org%2Fxpls%2Fabs_all.jsp%3Fisnumber%3D6104236%26arnumber%3D6025312 Solving Sudoku puzzles is formulated as an optimization problem over a set of probabilities. The constraints for a given puzzle translate into a convex polyhedral feasible set for the probabilities. The solution to the puzzle lies at an extremal point of the polyhedron where the probabilities are either zero or one and the entropy is zero. Because the entropy is positive at all other feasible points, an entropy minimization approach is adopted to solve Sudoku. To escape local entropy minima at nonsolution extremal points, a search procedure is proposed in which each iteration involves solving a simple convex optimization problem. This approach is evaluated on thousands of puzzles spanning four levels of difficulty from “easy” to “evil”. (Source: IEEE Transaction... IEEE Transactions on Signal Processing journals http://www.medworm.com/rss/comments.php?id=5521907 Wed, 21 Dec 2011 00:25:04 +0100 5521907 http://www.medworm.com/index.php?rid=5521906&cid=s_38180_169_f&fid=38180&url=http%3A%2F%2Fieeexplore.ieee.org%2Fxpls%2Fabs_all.jsp%3Fisnumber%3D6104236%26arnumber%3D6031935 This correspondence presents an efficient method for reconstructing a band-limited signal in the discrete domain from its crossings with a sine wave. The method makes it possible to design analog-to-discrete (A/D) converters that only deliver the crossing timings, which are then used to interpolate the input signal at arbitrary instants. Potentially, it may allow for reductions in power consumption and complexity in these converters. The reconstruction in the discrete domain is based on a recently-proposed modification of the Lagrange interpolator, which is readily implementable with linear complexity and efficiently, given that it reuses known schemes for variable fractional-delay (VFD) filters. As a spin-off, the method allows one to perform spectral analysis from sine wave crossings wit... IEEE Transactions on Signal Processing journals http://www.medworm.com/rss/comments.php?id=5521906 Wed, 21 Dec 2011 00:25:04 +0100 5521906 http://www.medworm.com/index.php?rid=5521905&cid=s_38180_169_f&fid=38180&url=http%3A%2F%2Fieeexplore.ieee.org%2Fxpls%2Fabs_all.jsp%3Fisnumber%3D6104236%26arnumber%3D6044726 We present a novel method to generate centered discrete dilated Hermite functions by utilizing Hermite–Gaussian differential equation and DFT commuting matrix proposed by Pei Compared with the conventional methods, our method provides much higher accuracy and wider working range. Based on expansion of compact support signals into discrete dilated Hermite basis, several examples of signal approximation and scaling are demonstrated. Our results in ECG signal compression can achieve lesser approximation error in comparison with discrete Daubechies wavelet transform. Also, our proposed discrete dilated Hermite functions have better ability to do signal scaling than the existing method. (Source: IEEE Transactions on Signal Processing) IEEE Transactions on Signal Processing journals http://www.medworm.com/rss/comments.php?id=5521905 Wed, 21 Dec 2011 00:25:04 +0100 5521905 http://www.medworm.com/index.php?rid=5521904&cid=s_38180_169_f&fid=38180&url=http%3A%2F%2Fieeexplore.ieee.org%2Fxpls%2Fabs_all.jsp%3Fisnumber%3D6104236%26arnumber%3D6035801 Interpolation is responsible for digital signal resampling and can significantly degrade the original signal quality if not done properly. For many years, optimal interpolation algorithms were sought within constrained classes of interpolation kernel functions. We derive a new family of unconstrained, finitely supported ${rm L} _{2}$ -optimal interpolation kernels $H _{L} (x)$, and compare their properties to the previously known results. Our research demonstrates that ${rm L} _{2}$-optimal kernels provide superior interpolation quality, and can be efficiently applied to any digital signal, of arbitrary nature, bandwidth, and dimensionality. (Source: IEEE Transactions on Signal Processing) IEEE Transactions on Signal Processing journals http://www.medworm.com/rss/comments.php?id=5521904 Wed, 21 Dec 2011 00:25:04 +0100 5521904 http://www.medworm.com/index.php?rid=5521903&cid=s_38180_169_f&fid=38180&url=http%3A%2F%2Fieeexplore.ieee.org%2Fxpls%2Fabs_all.jsp%3Fisnumber%3D6104236%26arnumber%3D6045354 The concept of rotation in the joint time-frequency plane can be exploited in order to generalize classical Fourier-based operations. It is known that filtering in rotated time-frequency domains can lead to significant performance advantages for certain types of signals as compared to conventional linear time invariant systems. In this correspondence, we revisit the design problem of such a scheme and derive a formulation that does not require knowledge of the statistics of the corrupting noise. Simulations have been used to confirm the validity of the proposed solution. (Source: IEEE Transactions on Signal Processing) IEEE Transactions on Signal Processing journals http://www.medworm.com/rss/comments.php?id=5521903 Wed, 21 Dec 2011 00:25:04 +0100 5521903 http://www.medworm.com/index.php?rid=5521902&cid=s_38180_169_f&fid=38180&url=http%3A%2F%2Fieeexplore.ieee.org%2Fxpls%2Fabs_all.jsp%3Fisnumber%3D6104236%26arnumber%3D6026258 This correspondence outlines a method for designing two-stage Nyquist filters. The Nyquist filter is split into two equal and linear-phase finite-length impulse response spectral factors. The per-time-unit multiplicative complexity, of the overall structure, is included as the objective function. Examples are then provided where Nyquist filters are designed so as to minimize the multiplicative complexity subject to the constraints on the overall Nyquist filter. In comparison to the single-stage case, the two-stage realization reduces the multiplicative complexity by an average of 48%. For two-stage sampling rate conversion (SRC), the correspondence shows that it is better to have a larger SRC ratio in the first stage. (Source: IEEE Transactions on Signal Processing) IEEE Transactions on Signal Processing journals http://www.medworm.com/rss/comments.php?id=5521902 Wed, 21 Dec 2011 00:25:04 +0100 5521902 http://www.medworm.com/index.php?rid=5521901&cid=s_38180_169_f&fid=38180&url=http%3A%2F%2Fieeexplore.ieee.org%2Fxpls%2Fabs_all.jsp%3Fisnumber%3D6104236%26arnumber%3D6025319 The strong uncorrelating transformation (SUT) is an effective tool for blind separation of complex-valued independent sources, commonly applied to the (spatial) sample autocovariance and pseudo-autocovariance matrices of the observed mixtures. In this work we analyze the performance (in terms of the resulting interference to source ratio (ISR)) of SUT-based blind separation of general wide-sense stationary complex-valued sources. Based on a small-errors analysis, we derive explicit expressions for the attainable ISR in terms of the temporal correlations and pseudo-correlations of the sources. We demonstrate by simulation that the empirical performance closely follows our analytic prediction at moderate to long observation lengths. An important implication ensuing from our analysis is that ... IEEE Transactions on Signal Processing journals http://www.medworm.com/rss/comments.php?id=5521901 Wed, 21 Dec 2011 00:25:04 +0100 5521901 http://www.medworm.com/index.php?rid=5521900&cid=s_38180_169_f&fid=38180&url=http%3A%2F%2Fieeexplore.ieee.org%2Fxpls%2Fabs_all.jsp%3Fisnumber%3D6104236%26arnumber%3D6036189 In this correspondence, we develop superfast approximative one-dimensional algorithms for the computationally efficient implementation of the recent iterative adaptive approach (IAA) spectral estimate. The proposed methods are based on rewriting the IAA algorithm with suitable Gohberg–Semencul representations, solving the resulting linear systems of equations using the preconditioned conjugate gradient method, where a novel preconditioning is applied using an incomplete factorization of the Toeplitz matrix. Numerical simulations illustrate the efficiency of both the proposed preconditioning as well as the overall algorithm, offering a computational reduction of up to two orders of magnitude as compared to our recently proposed efficient and exact IAA implementation. (Source: IEEE Tr... IEEE Transactions on Signal Processing journals http://www.medworm.com/rss/comments.php?id=5521900 Wed, 21 Dec 2011 00:25:04 +0100 5521900 http://www.medworm.com/index.php?rid=5521899&cid=s_38180_169_f&fid=38180&url=http%3A%2F%2Fieeexplore.ieee.org%2Fxpls%2Fabs_all.jsp%3Fisnumber%3D6104236%26arnumber%3D6026972 We note that the well-known Fast Rayleigh's quotient-based Adaptive Noise Subspace (FRANS), FRANS with Householder transformation (HFRANS), and fast data projection method (FDPM) algorithms all inherit from the data projection method (DPM) algorithm, but with different orthonormalization matrices. Starting from the DPM, we analyze the orthonormalization matrices of all these algorithms and develop a novel orthonormalization matrix for our algorithm. Based on this novel orthonormalization matrix, a fast and stable implementation of the DPM algorithm which has the merits of both the FRANS and FDPM approaches is investigated for principal and minor subspace tracking. The proposed algorithm can switch between the principal and minor subspace tracking with a simple sign change of its step size ... IEEE Transactions on Signal Processing journals http://www.medworm.com/rss/comments.php?id=5521899 Wed, 21 Dec 2011 00:25:04 +0100 5521899 http://www.medworm.com/index.php?rid=5521898&cid=s_38180_169_f&fid=38180&url=http%3A%2F%2Fieeexplore.ieee.org%2Fxpls%2Fabs_all.jsp%3Fisnumber%3D6104236%26arnumber%3D6006548 Studying brain connectivity has provided new insights to the understanding of brain function. While connectivity measures are conventionally computed from electroencephalogram (EEG) signals directly, the presence of volume conduction represents a serious confound affecting interpretation of results. A common solution is to use a two-stage approach which involves estimating underlying brain sources from scalp EEG recordings and subsequently estimating the connectivity between the inferred sources. Recently, a state-space framework which jointly models the instantaneous mixing effects of volume conduction and the causal relationships between underlying brain sources is proposed. In this paper, we extend the state-space framework and model the source activity by a generalized multivariate aut... IEEE Transactions on Signal Processing journals http://www.medworm.com/rss/comments.php?id=5521898 Wed, 21 Dec 2011 00:25:04 +0100 5521898 http://www.medworm.com/index.php?rid=5521897&cid=s_38180_169_f&fid=38180&url=http%3A%2F%2Fieeexplore.ieee.org%2Fxpls%2Fabs_all.jsp%3Fisnumber%3D6104236%26arnumber%3D6026969 Saddle point problems arise from many wireless applications, and primal-dual iterative algorithms are widely applied to find the saddle points. In the existing literature, the convergence results of such algorithms are established assuming the problem specific parameters remain unchanged during the iterations. However, this assumption is unrealistic in time varying wireless systems, as explicit message passing is usually involved in the iterations and the channel state information (CSI) may change in a time scale comparable to the algorithm update period. This paper investigates the convergence behavior and the tracking error of primal-dual iterative algorithms under time varying CSI. The convergence results are established by studying the stability of an equivalent virtual dynamic system ... IEEE Transactions on Signal Processing journals http://www.medworm.com/rss/comments.php?id=5521897 Wed, 21 Dec 2011 00:25:04 +0100 5521897 http://www.medworm.com/index.php?rid=5521896&cid=s_38180_169_f&fid=38180&url=http%3A%2F%2Fieeexplore.ieee.org%2Fxpls%2Fabs_all.jsp%3Fisnumber%3D6104236%26arnumber%3D6045351 This paper presents a randomized linear-dispersion space-time block code for decode-and-forward synchronous relays. The coding matrices are obtained as a set of columns (or rows) of randomly generated Haar-distributed unitary matrices. With respect to independent and identically distributed (i.i.d.)-generated codes, this particular isometric structure reduces the intersymbol interference generated within each relay. The gain over i.i.d. codes in terms of spectral efficiency is analyzed for both the LMMSE and the ML receivers under the assumption of frequency-flat quasi-static fading. In this setting, the spectral efficiency is a random quantity, since it depends on the random coding matrices. However, it is proven that the spectral efficiency converges in probability to a deterministic qua... IEEE Transactions on Signal Processing journals http://www.medworm.com/rss/comments.php?id=5521896 Wed, 21 Dec 2011 00:25:03 +0100 5521896 http://www.medworm.com/index.php?rid=5521895&cid=s_38180_169_f&fid=38180&url=http%3A%2F%2Fieeexplore.ieee.org%2Fxpls%2Fabs_all.jsp%3Fisnumber%3D6104236%26arnumber%3D6035798 Base station (BS) coordination is a key technique to handle intercell interference (ICI) in cellular networks. Nevertheless, recent work on scheduling indicates that the value of coordination is less prominent when the number of users grows large. More specifically, the loss in sum rate due to ICI in uncoordinated networks can be made arbitrarily small as the number of users goes to infinity. However, the gap in performance for a finite number of users has remained unknown so far. From this perspective we study the gains of multicell zero-forcing beamforming (ZFBF) on the downlink of a Wyner-type network. We first identify the beamforming weights and the optimal scheduling policy under a per-base power constraint. To compare ZFBF with single-cell processing (SCP) we focus on the extra numb... IEEE Transactions on Signal Processing journals http://www.medworm.com/rss/comments.php?id=5521895 Wed, 21 Dec 2011 00:25:03 +0100 5521895 http://www.medworm.com/index.php?rid=5521894&cid=s_38180_169_f&fid=38180&url=http%3A%2F%2Fieeexplore.ieee.org%2Fxpls%2Fabs_all.jsp%3Fisnumber%3D6104236%26arnumber%3D6093758 Consider a wireless sensor network (WSN) with a fusion center (FC) deployed to estimate signal parameters from noisy sensor measurements. If the WSN has a large number of low-cost, battery-operated sensor nodes with limited transmission bandwidth, then conservation of transmission resources (power and bandwidth) is paramount. To this end, the present paper develops a novel data reduction method which requires no inter-sensor collaboration and results in only a subset of the sensor measurements transmitted to the FC. Using interval censoring as a data-reduction method, each sensor decides separately whether to censor its acquired measurements based on a rule that promotes censoring of measurements with least impact on the estimator mean-square error (MSE). Leveraging the statistical distrib... IEEE Transactions on Signal Processing journals http://www.medworm.com/rss/comments.php?id=5521894 Wed, 21 Dec 2011 00:25:03 +0100 5521894 http://www.medworm.com/index.php?rid=5521893&cid=s_38180_169_f&fid=38180&url=http%3A%2F%2Fieeexplore.ieee.org%2Fxpls%2Fabs_all.jsp%3Fisnumber%3D6104236%26arnumber%3D6044727 Consensus algorithms have generated a lot of interest due to their ability to compute globally relevant statistics by only exploiting local communications among sensors. However, when implemented over wireless sensor networks, the inherent iterative nature of consensus algorithms may cause a large energy consumption. Hence, to make consensus algorithms really appealing in sensor networks, it is necessary to minimize the energy necessary to reach a consensus, within a given accuracy. We propose a method to optimize the network topology and the power allocation over each active link in order to minimize the energy consumption. We consider two network models: a deterministic model, where the nodes are located arbitrarily but their positions are known, and a random model, where the network top... IEEE Transactions on Signal Processing journals http://www.medworm.com/rss/comments.php?id=5521893 Wed, 21 Dec 2011 00:25:03 +0100 5521893 http://www.medworm.com/index.php?rid=5521892&cid=s_38180_169_f&fid=38180&url=http%3A%2F%2Fieeexplore.ieee.org%2Fxpls%2Fabs_all.jsp%3Fisnumber%3D6104236%26arnumber%3D6025314 This paper addresses the optimal design of limited-feedback downlink multiuser spatial multiplexing systems. A multiple-antenna base-station is assumed to serve multiple single-antenna users, who quantize and feed back their channel state information (CSI) through a shared rate-limited feedback channel. The optimization problem is cast in the form of minimizing the average transmission power at the base-station subject to users' target signal-to-interference-plus-noise ratios (SINR) and outage probability constraints. The goal is to derive the feedback bit allocations among the users and the corresponding channel magnitude and direction quantization codebooks in a high-resolution quantization regime. Toward this end, this paper develops an optimization framework using approximate analytica... IEEE Transactions on Signal Processing journals http://www.medworm.com/rss/comments.php?id=5521892 Wed, 21 Dec 2011 00:25:03 +0100 5521892 http://www.medworm.com/index.php?rid=5521891&cid=s_38180_169_f&fid=38180&url=http%3A%2F%2Fieeexplore.ieee.org%2Fxpls%2Fabs_all.jsp%3Fisnumber%3D6104236%26arnumber%3D6045355 To take the advantages of the $M$-ary space-shift keying (MSSK) modulation invented recently, a MSSK fast antenna-hopping space-division multiple-access (MSSK FAH-SDMA) scheme is proposed and studied in this paper. In addition to supporting multiple-access, the FAH is introduced also to achieve transmit diversity by sending every MSSK symbol over several time-slots under the control of a FAH pattern (address). Associated with the MSSK FAH-SDMA, a range of linear and nonlinear detection schemes are studied. Specifically, the linear detection schemes considered include the matched-filtering single-user detector (MF-SUD), zero-forcing multiuser detector (ZF-MUD) and minimum mean-square error (MMSE)-MUD, while the nonlinear detection schemes addressed include the maximum likelihood (ML)-MUD an... IEEE Transactions on Signal Processing journals http://www.medworm.com/rss/comments.php?id=5521891 Wed, 21 Dec 2011 00:25:03 +0100 5521891 http://www.medworm.com/index.php?rid=5521890&cid=s_38180_169_f&fid=38180&url=http%3A%2F%2Fieeexplore.ieee.org%2Fxpls%2Fabs_all.jsp%3Fisnumber%3D6104236%26arnumber%3D6032116 This paper considers the joint transceiver design for downlink multiuser multiple-input single-output (MISO) systems with coordinated base stations (BSs) where imperfect channel state information (CSI) is available at the BSs and mobile stations (MSs). By incorporating antenna correlation at the BSs and taking channel estimation errors into account, we solve two robust design problems: 1) minimizing the weighted sum of mean-square-error (MSE) with per BS antenna power constraint, and 2) minimizing the total power of all BSs with per user MSE target and per BS antenna power constraints. These problems are solved as follows. First, for fixed receivers, we propose centralized and novel computationally efficient distributed algorithms to jointly optimize the precoders of all users. Our central... IEEE Transactions on Signal Processing journals http://www.medworm.com/rss/comments.php?id=5521890 Wed, 21 Dec 2011 00:25:03 +0100 5521890 http://www.medworm.com/index.php?rid=5521889&cid=s_38180_169_f&fid=38180&url=http%3A%2F%2Fieeexplore.ieee.org%2Fxpls%2Fabs_all.jsp%3Fisnumber%3D6104236%26arnumber%3D6043915 This paper considers communication networks where individual links can be described as those based on multiple-input multiple-output channels. Unlike orthogonal modulation methods (such as the singular-value decomposition), we allow interference between subchannels, which can be removed by the receivers via successive cancellation. The degrees of freedom earned by this relaxation are used for obtaining a basis, and corresponding decomposition, which are simultaneously good for more than one link. Specifically, we derive necessary and sufficient conditions for shaping the ratio vector of subchannel gains of two broadcast-channel receivers. We then apply this decomposition to two scenarios: First, in digital multicasting we present a practical capacity-achieving scheme which uses only scalar... IEEE Transactions on Signal Processing journals http://www.medworm.com/rss/comments.php?id=5521889 Wed, 21 Dec 2011 00:25:03 +0100 5521889 http://www.medworm.com/index.php?rid=5521888&cid=s_38180_169_f&fid=38180&url=http%3A%2F%2Fieeexplore.ieee.org%2Fxpls%2Fabs_all.jsp%3Fisnumber%3D6104236%26arnumber%3D6051523 An amplify-and-forward (AF) multiple-input multiple-output (MIMO) relay network composed of a source, a relay, and a destination is considered, where transmit beamforming is employed both at the source and at the relay. The relay is a user who is willing to help the communication from the source to the destination. In our paper, however, the relay is untrusted in the sense that it may make a passive security attack; that is, it may decode messages of the source. We consider two ways to transmit confidential information of the source to the destination: noncooperative secure beamforming and cooperative secure beamforming. In the noncooperative scheme, the relay is simply treated as an eavesdropper, and does not participate in communication. In the cooperative scheme, the relay is asked to r... IEEE Transactions on Signal Processing journals http://www.medworm.com/rss/comments.php?id=5521888 Wed, 21 Dec 2011 00:25:03 +0100 5521888 http://www.medworm.com/index.php?rid=5521887&cid=s_38180_169_f&fid=38180&url=http%3A%2F%2Fieeexplore.ieee.org%2Fxpls%2Fabs_all.jsp%3Fisnumber%3D6104236%26arnumber%3D6035799 Due to its application in numerous engineering problems, the restless multi-armed bandit (RMAB) problem is of fundamental importance in stochastic decision theory. However, solving the RMAB problem is well known to be PSPACE-hard, with the optimal policy usually intractable due to the exponential computation complexity. A natural alternative approach is to seek simple myopic policies which are easy to implement. This paper presents a generic study on the optimality of the myopic policy for the RMAB problem. More specifically, we develop three axioms characterizing a family of generic and practically important functions termed as regular functions. By performing a mathematical analysis based on the developed axioms, we establish the closed-form conditions under which the myopic policy is gu... IEEE Transactions on Signal Processing journals http://www.medworm.com/rss/comments.php?id=5521887 Wed, 21 Dec 2011 00:25:03 +0100 5521887 http://www.medworm.com/index.php?rid=5521886&cid=s_38180_169_f&fid=38180&url=http%3A%2F%2Fieeexplore.ieee.org%2Fxpls%2Fabs_all.jsp%3Fisnumber%3D6104236%26arnumber%3D6022809 In this paper, we expand our recently introduced concept of unique word orthogonal frequency division multiplexing (UW-OFDM). In UW-OFDM the cyclic prefixes (CPs) are replaced by deterministic sequences, the so-called unique words (UWs). The UWs are generated by appropriately loading a set of redundant subcarriers. By that a systematic complex number Reed–Solomon (RS) code construction is introduced in a quite natural way, because an RS code may be defined as the set of vectors, for which a block of successive zeros occurs in the other domain w.r.t. a discrete Fourier transform. (For a fixed block different to zero, i.e., a UW, a coset code of an RS code is generated.) A remaining problem in the original systematic coded UW-OFDM concept is the fact that the redundant subcarrier symb... IEEE Transactions on Signal Processing journals http://www.medworm.com/rss/comments.php?id=5521886 Wed, 21 Dec 2011 00:25:03 +0100 5521886 http://www.medworm.com/index.php?rid=5521885&cid=s_38180_169_f&fid=38180&url=http%3A%2F%2Fieeexplore.ieee.org%2Fxpls%2Fabs_all.jsp%3Fisnumber%3D6104236%26arnumber%3D6025313 In this paper, joint channel estimation and data detection in orthogonal frequency division multiplexing (OFDM) amplify-and-forward (AF) cooperative systems under high mobility is investigated. Unlike previous works on cooperative systems in which a number of subcarriers are solely occupied by pilots, partial data-dependent superimposed training (PDDST) is considered here, thus preserving the spectral efficiency. First, a closed-form channel estimator is developed based on the least squares (LS) method with Tikhonov regularization and a corresponding data detection algorithm is proposed using the linear minimum mean square error (LMMSE) criterion. In the derived channel estimator, the unknown data is treated as part of the noise and the resulting data detection may not meet the required pe... IEEE Transactions on Signal Processing journals http://www.medworm.com/rss/comments.php?id=5521885 Wed, 21 Dec 2011 00:25:02 +0100 5521885 http://www.medworm.com/index.php?rid=5521884&cid=s_38180_169_f&fid=38180&url=http%3A%2F%2Fieeexplore.ieee.org%2Fxpls%2Fabs_all.jsp%3Fisnumber%3D6104236%26arnumber%3D5958630 We investigate robust turbo equalization over frequency selective channels in the presence of channel uncertainties. The turbo equalization framework investigated here contains a linear equalizer to combat ISI and a trellis based decoder. However, instead of completely tuning the linear equalizer parameters to the available inaccurate channel information, a minimax scheme and a competitive scheme are studied, which incorporate the uncertainty in channel information to equalizer design in order to improve robustness. Approximate implementations of these methods are also presented with reduced computational complexity. The performance improvement obtained by the proposed algorithms are demonstrated through simulations under different scenarios. (Source: IEEE Transactions on Signal Processing... IEEE Transactions on Signal Processing journals http://www.medworm.com/rss/comments.php?id=5521884 Wed, 21 Dec 2011 00:25:02 +0100 5521884 http://www.medworm.com/index.php?rid=5521883&cid=s_38180_169_f&fid=38180&url=http%3A%2F%2Fieeexplore.ieee.org%2Fxpls%2Fabs_all.jsp%3Fisnumber%3D6104236%26arnumber%3D6031934 Widely distributed multiple radar architectures offer parameter estimation improvement for target localization. For a large number of radars, with full resource allocation, the achievable localization minimum estimation mean-square error (MSE) may extend beyond the system predetermined performance goals. In this paper, performance driven resource allocation schemes for multiple radar systems are proposed. Two operational policies are considered. In the first, the number of transmit and receive antennas employed in the estimation process is minimized by effectively selecting a subset of active antennas such that the required MSE performance threshold is attained. In the second, an optimal subset of active antennas of predetermined size is selected such that the localization MSE is minimized... IEEE Transactions on Signal Processing journals http://www.medworm.com/rss/comments.php?id=5521883 Wed, 21 Dec 2011 00:25:02 +0100 5521883 http://www.medworm.com/index.php?rid=5521882&cid=s_38180_169_f&fid=38180&url=http%3A%2F%2Fieeexplore.ieee.org%2Fxpls%2Fabs_all.jsp%3Fisnumber%3D6104236%26arnumber%3D6026968 In this paper, we consider the linearly constrained distributed adaptive node-specific signal estimation (LC-DANSE) algorithm, which generates a node-specific linearly constrained minimum variance (LCMV) beamformer, i.e., with node-specific linear constraints, at each node of a wireless sensor network. The algorithm significantly reduces the number of signals that are exchanged between nodes, and yet obtains the optimal LCMV beamformers as if each node has access to all the signals in the network. We consider the case where all the steering vectors are known, as well as the blind beamforming case where the steering vectors are not known. We formally prove convergence and optimality for both versions of the LC-DANSE algorithm. We also consider the case where nodes update their local beamfor... IEEE Transactions on Signal Processing journals http://www.medworm.com/rss/comments.php?id=5521882 Wed, 21 Dec 2011 00:25:02 +0100 5521882 http://www.medworm.com/index.php?rid=5521881&cid=s_38180_169_f&fid=38180&url=http%3A%2F%2Fieeexplore.ieee.org%2Fxpls%2Fabs_all.jsp%3Fisnumber%3D6104236%26arnumber%3D6016250 We generalize the concept of multiuser peer-to-peer (MUP2P) relay networks, where $K$ source-destination pairs communicate through $L$ relays, to that of a multi-group multicasting (MGM) relay network. In the MGM scenario, each source may broadcast its message to a group of multiple users rather than to a single user only. Common distributed beamformer designs for MUP2P relay networks aim to minimize the total transmitted relay power subject to receiver quality-of-service (QoS) constraints. In state-of-the-art techniques, the resulting nonconvex problem is approximated by a convex one which is efficiently solvable using interior point methods. These techniques are shown to be straightforwardly extendable to more general MGM relay networks. However, as the number of receivers increases (whi... IEEE Transactions on Signal Processing journals http://www.medworm.com/rss/comments.php?id=5521881 Wed, 21 Dec 2011 00:25:02 +0100 5521881 http://www.medworm.com/index.php?rid=5521880&cid=s_38180_169_f&fid=38180&url=http%3A%2F%2Fieeexplore.ieee.org%2Fxpls%2Fabs_all.jsp%3Fisnumber%3D6104236%26arnumber%3D6051525 We consider distributed estimation of the inverse covariance matrix in Gaussian graphical models. These models factorize the multivariate distribution and allow for efficient distributed signal processing methods such as belief propagation (BP). The classical maximum likelihood approach to this covariance estimation problem, or potential function estimation in BP terminology, requires centralized computing and is computationally intensive. This motivates suboptimal distributed alternatives that tradeoff accuracy for communication cost. A natural solution is for each node to perform estimation of its local covariance with respect to its neighbors. The local maximum likelihood estimator is asymptotically consistent but suboptimal, i.e., it does not minimize mean squared estimation (MSE) erro... IEEE Transactions on Signal Processing journals http://www.medworm.com/rss/comments.php?id=5521880 Wed, 21 Dec 2011 00:25:02 +0100 5521880 http://www.medworm.com/index.php?rid=5521879&cid=s_38180_169_f&fid=38180&url=http%3A%2F%2Fieeexplore.ieee.org%2Fxpls%2Fabs_all.jsp%3Fisnumber%3D6104236%26arnumber%3D6025318 The dual purpose principal and minor subspace gradient flow can be used to track principal subspace (PS) and if altered simply by the sign, it can also serve as a minor subspace (MS) trackor. This is of practical significance in the implementations of algorithms. In this paper, a unified information criterion is proposed and a dual purpose principal and minor subspace gradient flow is derived based on the information criterion. In this dual purpose gradient flow, the weight matrix length is self-stabilizing, i.e., moving towards unit length in each learning step. The energy function associated with the dual purpose gradient flow for tracking PS and MS is given, and it exhibits a unique global minimum attained if and only if its state matrices span the PS or MS of the autocorrelation matrix... IEEE Transactions on Signal Processing journals http://www.medworm.com/rss/comments.php?id=5521879 Wed, 21 Dec 2011 00:25:02 +0100 5521879 http://www.medworm.com/index.php?rid=5521878&cid=s_38180_169_f&fid=38180&url=http%3A%2F%2Fieeexplore.ieee.org%2Fxpls%2Fabs_all.jsp%3Fisnumber%3D6104236%26arnumber%3D6036190 We study the problem of sparse reconstruction from noisy undersampled measurements when the following knowledge is available. (1) We are given partial, and partly erroneous, knowledge of the signal's support, denoted by $T$ . (2) We are also given an erroneous estimate of the signal values on $T$, denoted by $( {mathhat {mu }})_{T}$ . In practice, both of these may be available from prior knowledge. Alternatively, in recursive reconstruction applications, like real-time dynamic MRI, one can use the support estimate and the signal value estimate from the previous time instant as $T$ and $( {mathhat {mu }})_{T}$. In this paper, we introduce regularized modified basis pursuit denoising (BPDN) (reg-mod-BPDN) to solve this problem and obtain computable bounds on its reconstruction error. Reg-mo... IEEE Transactions on Signal Processing journals http://www.medworm.com/rss/comments.php?id=5521878 Wed, 21 Dec 2011 00:25:02 +0100 5521878 http://www.medworm.com/index.php?rid=5521877&cid=s_38180_169_f&fid=38180&url=http%3A%2F%2Fieeexplore.ieee.org%2Fxpls%2Fabs_all.jsp%3Fisnumber%3D6104236%26arnumber%3D6025311 In contrast to the vast amount of literature in random matrices in the field of compressed sensing, the subject of deterministic matrix design is at its early stages. Since these deterministic matrices are usually constructed using the polynomials in finite Galois fields, the number of rows (number of samples) is restricted to some specific integers such as prime powers. In this paper, besides extending a previous matrix design based on the binary BCH codes to the $p$-ary codes, we introduce matrices with wide variety of options for the number of rows. Simulation results demonstrate that these matrices perform almost as well as random matrices. (Source: IEEE Transactions on Signal Processing) IEEE Transactions on Signal Processing journals http://www.medworm.com/rss/comments.php?id=5521877 Wed, 21 Dec 2011 00:25:02 +0100 5521877 http://www.medworm.com/index.php?rid=5521876&cid=s_38180_169_f&fid=38180&url=http%3A%2F%2Fieeexplore.ieee.org%2Fxpls%2Fabs_all.jsp%3Fisnumber%3D6104236%26arnumber%3D6026970 The random demodulator (RD) and the modulated wideband converter (MWC) are two recently proposed compressed sensing (CS) techniques for the acquisition of continuous-time spectrally sparse signals. They extend the standard CS paradigm from sampling discrete, finite dimensional signals to sampling continuous and possibly infinite dimensional ones, and thus establish the ability to capture these signals at sub-Nyquist sampling rates. The RD and the MWC have remarkably similar structures (similar block diagrams), but their reconstruction algorithms and signal models strongly differ. To date, few results exist that compare these systems, and owing to the potential impacts they could have on spectral estimation in applications like electromagnetic scanning and cognitive radio, we more fully inv... IEEE Transactions on Signal Processing journals http://www.medworm.com/rss/comments.php?id=5521876 Wed, 21 Dec 2011 00:25:02 +0100 5521876 http://www.medworm.com/index.php?rid=5521875&cid=s_38180_169_f&fid=38180&url=http%3A%2F%2Fieeexplore.ieee.org%2Fxpls%2Fabs_all.jsp%3Fisnumber%3D6104236%26arnumber%3D6041037 This paper introduces a new framework to construct fast and efficient sensing matrices for practical compressive sensing, called Structurally Random Matrix (SRM). In the proposed framework, we prerandomize the sensing signal by scrambling its sample locations or flipping its sample signs and then fast-transform the randomized samples and finally, subsample the resulting transform coefficients to obtain the final sensing measurements. SRM is highly relevant for large-scale, real-time compressive sensing applications as it has fast computation and supports block-based processing. In addition, we can show that SRM has theoretical sensing performance comparable to that of completely random sensing matrices. Numerical simulation results verify the validity of the theory and illustrate the promi... IEEE Transactions on Signal Processing journals http://www.medworm.com/rss/comments.php?id=5521875 Wed, 21 Dec 2011 00:25:02 +0100 5521875 http://www.medworm.com/index.php?rid=5521874&cid=s_38180_169_f&fid=38180&url=http%3A%2F%2Fieeexplore.ieee.org%2Fxpls%2Fabs_all.jsp%3Fisnumber%3D6104236%26arnumber%3D6045352 This paper considers interleaved, multichannel measurements as arise for example in time-interleaved analog-to-digital (A/D) converters and in distributed sensor networks. Such systems take the form of either uniform or recurrent nonuniform sampling, depending on the relative timing between the channels. Uniform (i.e., linear) quantization in each channel results in an effective overall signal-to-quantization-error ratio (SQNR) in the reconstructed output which is dependent on the quantizer step size in each channel, the relative timing between the channels, and the oversampling ratio. It is shown that in the multichannel sampling system when the quantization step size is not restricted to be the same in each channel and the channel timing is not constrained to correspond to uniform sampli... IEEE Transactions on Signal Processing journals http://www.medworm.com/rss/comments.php?id=5521874 Wed, 21 Dec 2011 00:25:01 +0100 5521874 http://www.medworm.com/index.php?rid=5521873&cid=s_38180_169_f&fid=38180&url=http%3A%2F%2Fieeexplore.ieee.org%2Fxpls%2Fabs_all.jsp%3Fisnumber%3D6104236%26arnumber%3D6025316 Filter bank optimization for specific input statistics has been of great interest in both theory and practice in many signal processing applications. In this paper we propose GTD (generalized triangular decomposition) filter banks as a subband coder for optimizing the theoretical coding gain. We focus on perfect reconstruction orthonormal GTD filter banks and biorthogonal GTD filter banks. We show that in both cases there are two fundamental properties in the optimal solutions, namely, total decorrelation and spectrum equalization. The optimal solutions can be obtained by performing the frequency dependent GTD on the Cholesky factor of the input power spectrum density matrices. We also show that in both theory and numerical simulations, the optimal GTD subband coders have superior performa... IEEE Transactions on Signal Processing journals http://www.medworm.com/rss/comments.php?id=5521873 Wed, 21 Dec 2011 00:25:01 +0100 5521873 http://www.medworm.com/index.php?rid=5521872&cid=s_38180_169_f&fid=38180&url=http%3A%2F%2Fieeexplore.ieee.org%2Fxpls%2Fabs_all.jsp%3Fisnumber%3D6104236%26arnumber%3D6031936 A popular technique to design variable fractional delay (VFD) filters or variable bandedge filters is the polynomial based finite impulse response (FIR) filters, where each filter coefficient is approximated as a polynomial of the variable parameter. However, if the filter is required to have both VFD and variable bandedge, the computational complexity becomes very high, because two-dimensional polynomials have to be used, provided that the same polynomial idea is followed. In this paper, a filter bank approach is proposed for the design of VFD filters. The basic idea of the approach is to split the full band signals into subbands and each subband is, respectively, shifted by a phase, which is determined by the required fractional delay. The overall fractional delay is achieved by combinin... IEEE Transactions on Signal Processing journals http://www.medworm.com/rss/comments.php?id=5521872 Wed, 21 Dec 2011 00:25:01 +0100 5521872 http://www.medworm.com/index.php?rid=5521871&cid=s_38180_169_f&fid=38180&url=http%3A%2F%2Fieeexplore.ieee.org%2Fxpls%2Fabs_all.jsp%3Fisnumber%3D6104236%26arnumber%3D6025315 Balancing between power amplifier (PA) linearity and power efficiency is one of the biggest implementation challenges in radio communication transmitters. Among various linearization methods, the feedforward linearization technique is a fairly established principle offering a good tradeoff between linearity and power-efficiency even under wideband operation. Moreover, adaptive techniques for such linearizer have been proposed in literature to track parameter changes in the main PA and other circuitry. Among those, least mean squares (LMS) method for adapting signal cancellation loop (SCL) and error cancellation loop (ECL) coefficients is an attractive low-complexity alternative. In this paper, we carry out extensive closed-form performance analysis of the achievable intermodulation distort... IEEE Transactions on Signal Processing journals http://www.medworm.com/rss/comments.php?id=5521871 Wed, 21 Dec 2011 00:25:01 +0100 5521871 http://www.medworm.com/index.php?rid=5521870&cid=s_38180_169_f&fid=38180&url=http%3A%2F%2Fieeexplore.ieee.org%2Fxpls%2Fabs_all.jsp%3Fisnumber%3D6104236%26arnumber%3D6036188 An improved set-membership affine-projection (AP) adaptive-filtering algorithm is proposed. The new algorithm uses two error bounds that are estimated during the learning phase and by this means significantly reduced steady-state misalignment is achieved as compared to those in the conventional AP and set-membership AP algorithms while achieving similar convergence speed and re-adaptation capability. In addition, the proposed algorithm offers robust performance with respect to the error bound, projection order, impulsive-noise interference, and in tracking abrupt changes in the underlying system. These features of the proposed algorithm are demonstrated through extensive simulation results in system-identification and echo-cancellation applications. (Source: IEEE Transactions on Signal Pro... IEEE Transactions on Signal Processing journals http://www.medworm.com/rss/comments.php?id=5521870 Wed, 21 Dec 2011 00:25:01 +0100 5521870 http://www.medworm.com/index.php?rid=5521869&cid=s_38180_169_f&fid=38180&url=http%3A%2F%2Fieeexplore.ieee.org%2Fxpls%2Fabs_all.jsp%3Fisnumber%3D6104236%26arnumber%3D6026971 The blind identification of single-input multiple-output (SIMO) systems is often performed by exploiting a cross-relation (CR) between channel pairs. It has been shown that this property allows an estimation of channel impulse responses up to a common gain factor if certain identifiability conditions are met. In this case, the estimated channels can be evaluated by a gain-compensated system distance known as normalized projection misalignment (NPM). Current algorithms for blind channel identification, however, suffer in the presence of insufficient channel diversity and observation noise. In this paper, we first demonstrate that in the absence of noise the CR identification error for channels with exact common zeros is given by a single-channel pole-zero transfer function. Next, we extend ... IEEE Transactions on Signal Processing journals http://www.medworm.com/rss/comments.php?id=5521869 Wed, 21 Dec 2011 00:25:01 +0100 5521869 http://www.medworm.com/index.php?rid=5521868&cid=s_38180_169_f&fid=38180&url=http%3A%2F%2Fieeexplore.ieee.org%2Fxpls%2Fabs_all.jsp%3Fisnumber%3D6104236%26arnumber%3D6051524 One of the central problems of the stochastic approximation theory is the proper adjustment of the smoothing algorithm to the unknown, and possibly time-varying, rate and mode of variation of the estimated signals/parameters. In this paper we propose a novel locally adaptive parallel estimation scheme which can be used to solve the problem of fixed-interval Kalman smoothing in the presence of model uncertainty. The proposed solution is based on the idea of cooperative smoothing—the Bayesian extension of the leave-one-out cross-validation approach to model selection. Within this approach the smoothed estimates are evaluated as a convex combination of the estimates provided by several competing smoothers. We derive computationally attractive algorithms allowing for cooperative Kalman ... IEEE Transactions on Signal Processing journals http://www.medworm.com/rss/comments.php?id=5521868 Wed, 21 Dec 2011 00:25:01 +0100 5521868 http://www.medworm.com/index.php?rid=5521867&cid=s_38180_169_f&fid=38180&url=http%3A%2F%2Fieeexplore.ieee.org%2Fxpls%2Fabs_all.jsp%3Fisnumber%3D6104236%26arnumber%3D6043914 While a pair of $N times N$ matrices can almost always be exactly and simultaneously diagonalized by a generalized eigendecomposition, no exact solution exists in the case of a set with more than two matrices. This problem, termed approximate joint diagonalization (AJD), is instrumental in blind signal processing. When the set of matrices to be jointly diagonalized includes at least $N$ linearly independent matrices, we propose a suboptimal but closed-form solution for AJD in the direct least-squares sense. The corresponding non-iterative algorithm is given the acronym ${hbox{DIEM}}$ (DIagonalization using Equivalent Matrices). Extensive numerical simulations show that ${hbox{DIEM}}$ is both fast and accurate compared to the state-of-the-art iterative AJD algorithms. (Source: IEEE Transact... IEEE Transactions on Signal Processing journals http://www.medworm.com/rss/comments.php?id=5521867 Wed, 21 Dec 2011 00:25:01 +0100 5521867 http://www.medworm.com/index.php?rid=5521866&cid=s_38180_169_f&fid=38180&url=http%3A%2F%2Fieeexplore.ieee.org%2Fxpls%2Fabs_all.jsp%3Fisnumber%3D6104236%26arnumber%3D6035802 We consider regularized covariance estimation in scaled Gaussian settings, e.g., elliptical distributions, compound-Gaussian processes and spherically invariant random vectors. Asymptotically in the number of samples, the classical maximum likelihood (ML) estimate is optimal under different criteria and can be efficiently computed even though the optimization is nonconvex. We propose a unified framework for regularizing this estimate in order to improve its finite sample performance. Our approach is based on the discovery of hidden convexity within the ML objective. We begin by restricting the attention to diagonal covariance matrices. Using a simple change of variables, we transform the problem into a convex optimization that can be efficiently solved. We then extend this idea to nondiago... IEEE Transactions on Signal Processing journals http://www.medworm.com/rss/comments.php?id=5521866 Wed, 21 Dec 2011 00:25:01 +0100 5521866 http://www.medworm.com/index.php?rid=5521865&cid=s_38180_169_f&fid=38180&url=http%3A%2F%2Fieeexplore.ieee.org%2Fxpls%2Fabs_all.jsp%3Fisnumber%3D6104236%26arnumber%3D6036191 This paper focuses on the performance analysis and comparison of hard decision (HD) and soft decision (SD) based approaches for cooperative spectrum sensing in the presence of reporting channel errors. For cooperative sensing (CS) in cognitive radio networks, a distributed detection approach with displaced sensors and a fusion center (FC) is employed. For HD based CS, each secondary user (SU) sends a one-bit hard local decision to the FC. For SD based CS, each SU sends a quantized version of a local decision statistic such as the log-likelihood ratio or any suitable sufficient statistic. The decision statistics are sent through channels that may cause errors. The effects of channel errors are incorporated in the analysis through the bit error probability (BEP). For HD based CS, the countin... IEEE Transactions on Signal Processing journals http://www.medworm.com/rss/comments.php?id=5521865 Wed, 21 Dec 2011 00:25:01 +0100 5521865 http://www.medworm.com/index.php?rid=5521864&cid=s_38180_169_f&fid=38180&url=http%3A%2F%2Fieeexplore.ieee.org%2Fxpls%2Fabs_all.jsp%3Fisnumber%3D6104236%26arnumber%3D6021387 We propose a closed-form Gaussian sum smoother and, more importantly, closed-form smoothing solutions for increasingly complex problems arising from practice, including tracking in clutter, joint detection and tracking (in clutter), and multiple target tracking (in clutter) via the probability hypothesis density. The solutions are based on the corresponding forward–backward smoothing recursions that involve forward propagation of the filtering densities, followed by backward propagation of the smoothed densities. The key to the exact solutions is the use of alternative forms of the backward propagations, together with standard Gaussian identities. Simulations are also presented to verify the proposed solutions. (Source: IEEE Transactions on Signal Processing) IEEE Transactions on Signal Processing journals http://www.medworm.com/rss/comments.php?id=5521864 Wed, 21 Dec 2011 00:25:00 +0100 5521864 http://www.medworm.com/index.php?rid=5521863&cid=s_38180_169_f&fid=38180&url=http%3A%2F%2Fieeexplore.ieee.org%2Fxpls%2Fabs_all.jsp%3Fisnumber%3D6104236%26arnumber%3D6104276 (Source: IEEE Transactions on Signal Processing) IEEE Transactions on Signal Processing journals http://www.medworm.com/rss/comments.php?id=5521863 Wed, 21 Dec 2011 00:25:00 +0100 5521863 http://www.medworm.com/index.php?rid=5521862&cid=s_38180_169_f&fid=38180&url=http%3A%2F%2Fieeexplore.ieee.org%2Fxpls%2Fabs_all.jsp%3Fisnumber%3D6104236%26arnumber%3D6104238 (Source: IEEE Transactions on Signal Processing) IEEE Transactions on Signal Processing journals http://www.medworm.com/rss/comments.php?id=5521862 Wed, 21 Dec 2011 00:25:00 +0100 5521862 http://www.medworm.com/index.php?rid=5521861&cid=s_38180_169_f&fid=38180&url=http%3A%2F%2Fieeexplore.ieee.org%2Fxpls%2Fabs_all.jsp%3Fisnumber%3D6104236%26arnumber%3D6104274 (Source: IEEE Transactions on Signal Processing) IEEE Transactions on Signal Processing journals http://www.medworm.com/rss/comments.php?id=5521861 Wed, 21 Dec 2011 00:25:00 +0100 5521861 http://www.medworm.com/index.php?rid=5438848&cid=s_38180_169_f&fid=38180&url=http%3A%2F%2Fieeexplore.ieee.org%2Fxpls%2Fabs_all.jsp%3Fisnumber%3D6069620%26arnumber%3D6020820 Compressed sensing aims at reconstructing sparse signals from significantly reduced number of samples, and a popular reconstruction approach is $ell_{1}$-norm minimization. In this correspondence, a method called orthonormal expansion is presented to reformulate the basis pursuit problem for noiseless compressed sensing. Two algorithms are proposed based on convex optimization: one exactly solves the problem and the other is a relaxed version of the first one. The latter can be considered as a modified iterative soft thresholding algorithm and is easy to implement. Numerical simulation shows that, in dealing with noise-free measurements of sparse signals, the relaxed version is accurate, fast and competitive to the recent state-of-the-art algorithms. Its practical application is demonstrat... IEEE Transactions on Signal Processing journals http://www.medworm.com/rss/comments.php?id=5438848 Thu, 24 Nov 2011 00:43:24 +0100 5438848 http://www.medworm.com/index.php?rid=5429436&cid=s_38180_169_f&fid=38180&url=http%3A%2F%2Fieeexplore.ieee.org%2Fxpls%2Fabs_all.jsp%3Fisnumber%3D6069620%26arnumber%3D6078478 (Source: IEEE Transactions on Signal Processing) IEEE Transactions on Signal Processing journals http://www.medworm.com/rss/comments.php?id=5429436 Mon, 21 Nov 2011 00:47:23 +0100 5429436 http://www.medworm.com/index.php?rid=5429435&cid=s_38180_169_f&fid=38180&url=http%3A%2F%2Fieeexplore.ieee.org%2Fxpls%2Fabs_all.jsp%3Fisnumber%3D6069620%26arnumber%3D6078479 (Source: IEEE Transactions on Signal Processing) IEEE Transactions on Signal Processing journals http://www.medworm.com/rss/comments.php?id=5429435 Mon, 21 Nov 2011 00:47:23 +0100 5429435 http://www.medworm.com/index.php?rid=5429434&cid=s_38180_169_f&fid=38180&url=http%3A%2F%2Fieeexplore.ieee.org%2Fxpls%2Fabs_all.jsp%3Fisnumber%3D6069620%26arnumber%3D6078475 (Source: IEEE Transactions on Signal Processing) IEEE Transactions on Signal Processing journals http://www.medworm.com/rss/comments.php?id=5429434 Mon, 21 Nov 2011 00:47:23 +0100 5429434 http://www.medworm.com/index.php?rid=5429433&cid=s_38180_169_f&fid=38180&url=http%3A%2F%2Fieeexplore.ieee.org%2Fxpls%2Fabs_all.jsp%3Fisnumber%3D6069620%26arnumber%3D6078476 (Source: IEEE Transactions on Signal Processing) IEEE Transactions on Signal Processing journals http://www.medworm.com/rss/comments.php?id=5429433 Mon, 21 Nov 2011 00:47:23 +0100 5429433 http://www.medworm.com/index.php?rid=5429432&cid=s_38180_169_f&fid=38180&url=http%3A%2F%2Fieeexplore.ieee.org%2Fxpls%2Fabs_all.jsp%3Fisnumber%3D6069620%26arnumber%3D6069621 Lists the reviewers who contributed to IEEE Transactions on Signal Processing. (Source: IEEE Transactions on Signal Processing) IEEE Transactions on Signal Processing journals http://www.medworm.com/rss/comments.php?id=5429432 Mon, 21 Nov 2011 00:47:23 +0100 5429432 http://www.medworm.com/index.php?rid=5429431&cid=s_38180_169_f&fid=38180&url=http%3A%2F%2Fieeexplore.ieee.org%2Fxpls%2Fabs_all.jsp%3Fisnumber%3D6069620%26arnumber%3D6020820 Compressed sensing aims at reconstructing sparse signals from significantly reduced number of samples, and a popular reconstruction approach is $ell_{1}$-norm minimization. In this correspondence, a method called orthonormal expansion is presented to reformulate the basis pursuit problem for noiseless compressed sensing. Two algorithms are proposed based on convex optimization: one exactly solves the problem and the other is a relaxed version of the first one. The latter can be considered as a modified iterative soft thresholding algorithm and is easy to implement. Numerical simulation shows that, in dealing with noise-free measurements of sparse signals, the relaxed version is accurate, fast and competitive to the recent state-of-the-art algorithms. Its practical application is demonstrat... IEEE Transactions on Signal Processing journals http://www.medworm.com/rss/comments.php?id=5429431 Mon, 21 Nov 2011 00:47:23 +0100 5429431 http://www.medworm.com/index.php?rid=5429430&cid=s_38180_169_f&fid=38180&url=http%3A%2F%2Fieeexplore.ieee.org%2Fxpls%2Fabs_all.jsp%3Fisnumber%3D6069620%26arnumber%3D6006547 This contribution studies the convergence of consensus algorithms in random wireless sensor networks with spatially correlated links. Aiming at reducing the convergence time, we adopt an optimization criterion based on the minimization of the spectral radius of a matrix for which we derive closed-form expressions for both directed and undirected topologies. We show that the minimization of the spectral radius assuming constant link weights is a convex optimization problem. The expressions derived subsume known protocols found in literature. (Source: IEEE Transactions on Signal Processing) IEEE Transactions on Signal Processing journals http://www.medworm.com/rss/comments.php?id=5429430 Mon, 21 Nov 2011 00:47:23 +0100 5429430 http://www.medworm.com/index.php?rid=5429429&cid=s_38180_169_f&fid=38180&url=http%3A%2F%2Fieeexplore.ieee.org%2Fxpls%2Fabs_all.jsp%3Fisnumber%3D6069620%26arnumber%3D6016249 Parallel multiple-input multiple-output (MIMO) broadcast channels have been shown to be separable from an information theoretic point of view, i.e., capacity can be achieved with a strategy that performs separate encoding and decoding on each subchannel subject to a power allocation across subchannels. In this paper, we show that separability does not necessarily hold if the transmit strategy is restricted to linear transceivers. The proof will be done by identifying a rate tuple that is achievable in a certain set of channels with joint treatment of the subchannels, but lies outside the achievable rate region of separate linear precoding. The implications of this result are that any algorithm to optimize transmit strategies in parallel MIMO broadcast channels that is based on both linear ... IEEE Transactions on Signal Processing journals http://www.medworm.com/rss/comments.php?id=5429429 Mon, 21 Nov 2011 00:47:22 +0100 5429429 http://www.medworm.com/index.php?rid=5429428&cid=s_38180_169_f&fid=38180&url=http%3A%2F%2Fieeexplore.ieee.org%2Fxpls%2Fabs_all.jsp%3Fisnumber%3D6069620%26arnumber%3D5986745 A simple and straightforward method of constructing higher-level three-dimensional (3-D) signal constellations for a reliable digital communication system is proposed in this paper. The new method expands basic 8-ary constellation into 3-D signal space systematically so that it produces lattice configurations. We also derive accurate closed-form symbol error probability (SEP) of cross-lattice constellations in additive white Gaussian noise (AWGN). It is verified that the theoretical SEPs are almost the same as simulation results. Minimum Euclidean distance (MED) of the higher-level 3-D constellations is increased at least 49% in comparison with quadrature amplitude modulation (QAM). When the number of symbols is 256, the 3-D constellation has around 105% longer MED than the 2-D QAM. Due to... IEEE Transactions on Signal Processing journals http://www.medworm.com/rss/comments.php?id=5429428 Mon, 21 Nov 2011 00:47:22 +0100 5429428 http://www.medworm.com/index.php?rid=5429427&cid=s_38180_169_f&fid=38180&url=http%3A%2F%2Fieeexplore.ieee.org%2Fxpls%2Fabs_all.jsp%3Fisnumber%3D6069620%26arnumber%3D5986747 We consider the problem of energy-efficient point-to-point transmission of delay-sensitive data (e.g., multimedia data) over a fading channel. We propose a rigorous and unified framework for simultaneously utilizing both physical-layer and system-level techniques to minimize energy consumption, under delay constraints, in the presence of stochastic and unknown traffic and channel conditions. We formulate the problem as a Markov decision process and solve it online using reinforcement learning. The advantages of the proposed online method are that i) it does not require a priori knowledge of the traffic arrival and channel statistics to determine the jointly optimal physical-layer and system-level power management strategies; ii) it exploits partial information about the system so that less... IEEE Transactions on Signal Processing journals http://www.medworm.com/rss/comments.php?id=5429427 Mon, 21 Nov 2011 00:47:22 +0100 5429427 http://www.medworm.com/index.php?rid=5429426&cid=s_38180_169_f&fid=38180&url=http%3A%2F%2Fieeexplore.ieee.org%2Fxpls%2Fabs_all.jsp%3Fisnumber%3D6069620%26arnumber%3D6020818 In this work, a new fast variational sparse Bayesian learning (SBL) approach with automatic relevance determination (ARD) is proposed. The sparse Bayesian modeling, exemplified by the relevance vector machine (RVM), allows a sparse regression or classification function to be constructed as a linear combination of a few basis functions. It is demonstrated that, by computing the stationary points of the variational update expressions with noninformative (ARD) hyperpriors, a fast version of variational SBL can be constructed. Analysis of the computed stationary points indicates that SBL with Gaussian sparsity priors and noninformative hyperpriors corresponds to removing components with signal-to-noise ratio below a 0 dB threshold; this threshold can also be adjusted to significantly improve t... IEEE Transactions on Signal Processing journals http://www.medworm.com/rss/comments.php?id=5429426 Mon, 21 Nov 2011 00:47:22 +0100 5429426 http://www.medworm.com/index.php?rid=5429425&cid=s_38180_169_f&fid=38180&url=http%3A%2F%2Fieeexplore.ieee.org%2Fxpls%2Fabs_all.jsp%3Fisnumber%3D6069620%26arnumber%3D6004841 In this correspondence, we introduce a dual-tree rational-dilation complex wavelet transform for oscillatory signal processing. Like the short-time Fourier transform and the dyadic dual-tree complex wavelet transform, the introduced transform employs quadrature pairs of time-frequency atoms which allow to work with the analytic signal. The introduced wavelet transform is a constant-$Q$ transform, a property lacked by the short-time Fourier transform, which in turn makes the introduced transform more suitable for models that depend on scale. Also, the frequency resolution can be as high as desired, a property lacked by the dyadic dual-tree complex wavelet transform, which makes the introduced transform more suitable for processing oscillatory signals like speech, audio and various biomedica... IEEE Transactions on Signal Processing journals http://www.medworm.com/rss/comments.php?id=5429425 Mon, 21 Nov 2011 00:47:22 +0100 5429425 http://www.medworm.com/index.php?rid=5429424&cid=s_38180_169_f&fid=38180&url=http%3A%2F%2Fieeexplore.ieee.org%2Fxpls%2Fabs_all.jsp%3Fisnumber%3D6069620%26arnumber%3D5997323 This study is concerned with quantifying shift variance of linear discrete-time multirate systems. Based on commutators of a system and the shift operators, we introduce a shift-variance measure for the multirate system. The measure is defined as the half of the ratio of the maximal norm of the commutators to the norm of the multirate system. It ranges from zero to unity, corresponding to minimal shift variance (i.e., full shift invariance) and maximal shift variance, respectively. We derive analytical expressions on the shift-variance measure of multirate filterbanks. The relation between shift variance of the individual channels of multichannel filterbanks is then studied. We also analyze the shift invariance of some particular filterbanks, including biorthogonal filterbanks and complex ... IEEE Transactions on Signal Processing journals http://www.medworm.com/rss/comments.php?id=5429424 Mon, 21 Nov 2011 00:47:22 +0100 5429424 http://www.medworm.com/index.php?rid=5429423&cid=s_38180_169_f&fid=38180&url=http%3A%2F%2Fieeexplore.ieee.org%2Fxpls%2Fabs_all.jsp%3Fisnumber%3D6069620%26arnumber%3D5997320 This correspondence investigates the least squares and minimax design problems for allpass variable fractional delay (VFD) filters. A two stage optimization approach is proposed to solve the resulting minimax optimization problem. This approach includes a combination of a one-dimensional global search method and an adaptive scheme to refine the discretization points. In addition, the paper investigates the design of allpass VFD filters which minimizes the weighted integral squared error subject to constraints on peak error deviation from the desired response. By using approximations, the design problem can be formulated as a quadratic optimization problem. Design examples show that a tradeoff between the weighted integral squared error and the peak error deviation can be achieved. In addit... IEEE Transactions on Signal Processing journals http://www.medworm.com/rss/comments.php?id=5429423 Mon, 21 Nov 2011 00:47:22 +0100 5429423 http://www.medworm.com/index.php?rid=5429422&cid=s_38180_169_f&fid=38180&url=http%3A%2F%2Fieeexplore.ieee.org%2Fxpls%2Fabs_all.jsp%3Fisnumber%3D6069620%26arnumber%3D6021386 In this paper, we present a theoretical convergence analysis of the affine projection algorithm (APA) based on the arguments of energy conservation. Although the APA and its convergence analysis have been widely studied, the dependency of weight-error vector on past noise is usually neglected for simplicity. To obtain accurate theoretical results for the APA, we here consider the dependency between the weight-error vector and past noise in the mean-square analysis presented by Shin and Sayed in [“Mean-square performance of a family of affine projection algorithms,” IEEE Transactions on Signal Processing, vol. 52, no. 1, pp. 90–102, January 2004]. Through this work, we can also theoretically analyze the behavior of the periodic APA, which updates its weights periodicall... IEEE Transactions on Signal Processing journals http://www.medworm.com/rss/comments.php?id=5429422 Mon, 21 Nov 2011 00:47:22 +0100 5429422 http://www.medworm.com/index.php?rid=5429421&cid=s_38180_169_f&fid=38180&url=http%3A%2F%2Fieeexplore.ieee.org%2Fxpls%2Fabs_all.jsp%3Fisnumber%3D6069620%26arnumber%3D5955137 In this correspondence, we provide a transient analysis of an affinely constrained mixture method that adaptively combines the outputs of adaptive filters running in parallel on the same task. The affinely constrained mixture is adapted using a stochastic gradient update to minimize the square of the prediction error. Although we specifically carry out the transient analysis for a combination of two equal length adaptive filters trying to learn a linear model working on real valued data, we also provide the final equations and the necessary extensions in order to generalize the transient analysis to mixtures combining more than two filters; using Newton based updates to train the mixture weights; working on complex valued data; or unconstrained mixtures. The derivations are generic such th... IEEE Transactions on Signal Processing journals http://www.medworm.com/rss/comments.php?id=5429421 Mon, 21 Nov 2011 00:47:22 +0100 5429421 http://www.medworm.com/index.php?rid=5429420&cid=s_38180_169_f&fid=38180&url=http%3A%2F%2Fieeexplore.ieee.org%2Fxpls%2Fabs_all.jsp%3Fisnumber%3D6069620%26arnumber%3D6021384 Several SOA (state of the art) self-tuning software libraries exist, such as the Fastest Fourier Transform in the West (FFTW) for fast Fourier transform (FFT). FFT is a highly important kernel and the performance of its software implementations depends on the memory hierarchy's utilization. FFTW minimizes register spills and data cache accesses by finding a schedule that is independent of the number of the registers and of the number of levels and size of the cache, which is a serious drawback. In this paper, a new methodology is presented, achieving improved performance by focusing on memory hierarchy utilization. The proposed methodology has three major advantages. First, the combination of production and consumption of butterflies' results, data reuse, FFT parallelism, symmetries of twi... IEEE Transactions on Signal Processing journals http://www.medworm.com/rss/comments.php?id=5429420 Mon, 21 Nov 2011 00:47:22 +0100 5429420 http://www.medworm.com/index.php?rid=5429419&cid=s_38180_169_f&fid=38180&url=http%3A%2F%2Fieeexplore.ieee.org%2Fxpls%2Fabs_all.jsp%3Fisnumber%3D6069620%26arnumber%3D5993551 The Federal Communications Commission (FCC) Phase II enhanced 911 (E-911) requirements have motivated increased interest in the challenge of localizing mobile sources in urban environments. The FCC E-911 Phase-II requires wireless carriers to provide the location of a 911 caller with accuracy of 100 meters in 67% of cases and 300 meters in 95% of cases. This work proposes an information theoretic bound on mobile station (MS) localization performance in urban environments that provides an alternative criterion for the MS localization performance evaluation. The proposed lower bound provides necessary, but not sufficient conditions for achieving arbitrary small probability of the localization error. The MS localization problem is modeled in the framework of communication via channels where t... IEEE Transactions on Signal Processing journals http://www.medworm.com/rss/comments.php?id=5429419 Mon, 21 Nov 2011 00:47:22 +0100 5429419 http://www.medworm.com/index.php?rid=5429418&cid=s_38180_169_f&fid=38180&url=http%3A%2F%2Fieeexplore.ieee.org%2Fxpls%2Fabs_all.jsp%3Fisnumber%3D6069620%26arnumber%3D5993550 In this paper, we address the problem of gesture recognition using the theory of random projection (RP) and by formulating the whole recognition problem as an $ell_{1}$-minimization problem. The gesture recognition system operates primarily on data from a single 3-axis accelerometer and comprises two main stages: a training stage and a testing stage. For training, the system employs dynamic time warping as well as affinity propagation to create exemplars for each gesture while for testing, the system projects all candidate traces and also the unknown trace onto the same lower dimensional subspace for recognition. A dictionary of 18 gestures is defined and a database of over 3700 traces is created from seven subjects on which the system is tested and evaluated. To the best of our knowledge,... IEEE Transactions on Signal Processing journals http://www.medworm.com/rss/comments.php?id=5429418 Mon, 21 Nov 2011 00:47:21 +0100 5429418 http://www.medworm.com/index.php?rid=5429417&cid=s_38180_169_f&fid=38180&url=http%3A%2F%2Fieeexplore.ieee.org%2Fxpls%2Fabs_all.jsp%3Fisnumber%3D6069620%26arnumber%3D5985553 This paper deals with network-coded multicast for real-time and streaming-media applications where packets have explicit expiration deadlines. Most of the popular network coding approaches require asymptotically large block-lengths, thereby incurring long decoding delays. The present paper introduces a joint scheduling and network coding design that aims to maximize the average throughput while respecting the packet deadlines. The novel approach relies on a time-unwrapped graph expansion in order to construct the network codes. The resultant algorithm draws from the well-known augmenting-path algorithm, and is both distributed as well as scalable. For networks with primary interference, a lower-bound on the worst-case performance of the algorithm is provided. The associated optimization pr... IEEE Transactions on Signal Processing journals http://www.medworm.com/rss/comments.php?id=5429417 Mon, 21 Nov 2011 00:47:21 +0100 5429417 http://www.medworm.com/index.php?rid=5429416&cid=s_38180_169_f&fid=38180&url=http%3A%2F%2Fieeexplore.ieee.org%2Fxpls%2Fabs_all.jsp%3Fisnumber%3D6069620%26arnumber%3D6006543 In this paper, an optimal amplitude weight expression is derived and presented in closed form. The minimal error variance for location estimation of a near-field source signal that has a low time-bandwidth product is also presented. A noniterative method to calculate and apply weights is proposed to yield more robust estimation results at a lower calculational cost when compared to the traditional iterative method. Besides a theoretical evaluation, the proposed algorithm is also verified through Monte Carlo simulation. The weight expression derived also optimizes the system signal-to-noise ratio (SNR), hence it can be applied to improve the performance of any estimator/detector that utilizes the energy in the sum of sensor output signals. (Source: IEEE Transactions on Signal Processing) IEEE Transactions on Signal Processing journals http://www.medworm.com/rss/comments.php?id=5429416 Mon, 21 Nov 2011 00:47:21 +0100 5429416 http://www.medworm.com/index.php?rid=5429415&cid=s_38180_169_f&fid=38180&url=http%3A%2F%2Fieeexplore.ieee.org%2Fxpls%2Fabs_all.jsp%3Fisnumber%3D6069620%26arnumber%3D6006542 The goal of this paper is to propose a bio-inspired radio access mechanism for cognitive networks mimicking the behavior of a flock of birds swarming in search for food in a cohesive fashion without colliding with each other. The equivalence between swarming and radio resource allocation is established by modeling the interference distribution in the resource domain, e.g., frequency and time, as the spatial distribution of food, while the position of the single bird represents the radio resource chosen by each radio node. The swarming mechanism is enforced by letting every node allocate its resources (power/bits) in the time-frequency regions where the interference is minimum (the food density is maximum), avoiding collisions with other nodes (birds), yet limiting the spread in the time-fr... IEEE Transactions on Signal Processing journals http://www.medworm.com/rss/comments.php?id=5429415 Mon, 21 Nov 2011 00:47:21 +0100 5429415 http://www.medworm.com/index.php?rid=5429414&cid=s_38180_169_f&fid=38180&url=http%3A%2F%2Fieeexplore.ieee.org%2Fxpls%2Fabs_all.jsp%3Fisnumber%3D6069620%26arnumber%3D5997321 In this paper, we investigate the distortion outage performance of distributed estimation schemes in wireless sensor networks, where a distortion outage is defined as the event that the estimation error or distortion exceeds a predetermined threshold. The sensors transmit their observation signals using the analog amplify and forward scheme through coherent multiaccess channels to the fusion center, which reconstructs a minimum mean squared error (MMSE) estimate of the physical quantity observed. We consider three power allocation schemes: 1) equal power allocation (EPA); 2) short-term optimal power allocation (ST-OPA), where we minimize the distortion subject to a power constraint at each time step; and 3) long-term optimal power allocation (LT-OPA), where we minimize the distortion outag... IEEE Transactions on Signal Processing journals http://www.medworm.com/rss/comments.php?id=5429414 Mon, 21 Nov 2011 00:47:21 +0100 5429414 http://www.medworm.com/index.php?rid=5429413&cid=s_38180_169_f&fid=38180&url=http%3A%2F%2Fieeexplore.ieee.org%2Fxpls%2Fabs_all.jsp%3Fisnumber%3D6069620%26arnumber%3D5986748 Maximizing the minimum weighted signal-to-interference-and-noise ratio (SINR), minimizing the weighted sum mean-square error (MSE) and maximizing the weighted sum rate in a multiuser downlink system are three important performance objectives in nonconvex joint transceiver and power optimization, where all the users have a total power constraint. We show that, through connections with the nonlinear Perron–Frobenius theory, jointly optimizing power and beamformers in the max-min weighted SINR problem can be solved optimally in a distributed fashion. Then, connecting these three performance objectives through the arithmetic-geometric mean inequality and nonnegative matrix theory, we solve the weighted sum MSE minimization and the weighted sum rate maximization in the weak interference ... IEEE Transactions on Signal Processing journals http://www.medworm.com/rss/comments.php?id=5429413 Mon, 21 Nov 2011 00:47:21 +0100 5429413 http://www.medworm.com/index.php?rid=5429412&cid=s_38180_169_f&fid=38180&url=http%3A%2F%2Fieeexplore.ieee.org%2Fxpls%2Fabs_all.jsp%3Fisnumber%3D6069620%26arnumber%3D5985549 Spatial interference avoidance is a simple and effective way of mitigating interference in multiantenna wireless networks. The deployment of this technique requires channel-state information (CSI) feedback from each receiver to all interferers, resulting in substantial network overhead. To address this issue, this paper proposes the method of distributive control that intelligently allocates CSI bits over multiple feedback links and adapts feedback to channel dynamics. For symmetric channel distributions, it is optimal for each receiver to equally allocate the average sum-feedback rate for different feedback links, thereby decoupling their control. Using the criterion of minimum sum-interference power, the optimal feedback-control policy is shown using stochastic-optimization theory to exh... IEEE Transactions on Signal Processing journals http://www.medworm.com/rss/comments.php?id=5429412 Mon, 21 Nov 2011 00:47:21 +0100 5429412 http://www.medworm.com/index.php?rid=5429411&cid=s_38180_169_f&fid=38180&url=http%3A%2F%2Fieeexplore.ieee.org%2Fxpls%2Fabs_all.jsp%3Fisnumber%3D6069620%26arnumber%3D5997324 This paper addresses cooperation in a multicell environment where base stations (BSs) wish to jointly serve multiple users, under a constrained-capacity backhaul. We point out that for finite backhaul capacity a tradeoff between sharing user data, which allows for full MIMO cooperation, and not doing so, which reduces the setup to an interference channel but also requires less overhead, emerges. We optimize this tradeoff by formulating a rate splitting approach in which non-shared data (private to each transmitter) and shared data are superimposed. We derive the corresponding achievable rate region and obtain the optimal beamforming design for both shared and private symbols. We illustrate how the capacity of the backhaul determines how much of the user data is worth sharing across multipl... IEEE Transactions on Signal Processing journals http://www.medworm.com/rss/comments.php?id=5429411 Mon, 21 Nov 2011 00:47:21 +0100 5429411 http://www.medworm.com/index.php?rid=5429410&cid=s_38180_169_f&fid=38180&url=http%3A%2F%2Fieeexplore.ieee.org%2Fxpls%2Fabs_all.jsp%3Fisnumber%3D6069620%26arnumber%3D5993552 The throughput of multicell systems is inherently limited by interference and the available communication resources. Coordinated resource allocation is the key to efficient performance, but the demand on backhaul signaling and computational resources grows rapidly with number of cells, terminals, and subcarriers. To handle this, we propose a novel multicell framework with dynamic cooperation clusters where each terminal is jointly served by a small set of base stations. Each base station coordinates interference to neighboring terminals only, thus limiting backhaul signalling and making the framework scalable. This framework can describe anything from interference channels to ideal joint multicell transmission. The resource allocation (i.e., precoding and scheduling) is formulated as an op... IEEE Transactions on Signal Processing journals http://www.medworm.com/rss/comments.php?id=5429410 Mon, 21 Nov 2011 00:47:21 +0100 5429410 http://www.medworm.com/index.php?rid=5429409&cid=s_38180_169_f&fid=38180&url=http%3A%2F%2Fieeexplore.ieee.org%2Fxpls%2Fabs_all.jsp%3Fisnumber%3D6069620%26arnumber%3D5985552 Unique word—orthogonal frequency division multiplexing (UW-OFDM) is a novel OFDM signaling concept, where the guard interval is built of a deterministic sequence—the so-called unique word—instead of the conventional random cyclic prefix. In contrast to previous attempts with deterministic sequences in the guard interval the addressed UW-OFDM signaling approach introduces correlations between the subcarrier symbols, which can be exploited by the receiver in order to improve the bit error ratio performance. In this paper we develop several linear data estimators specifically designed for UW-OFDM, some based on classical and some based on Bayesian estimation theory. Furthermore, we derive complexity optimized versions of these estimators, and we study their individual com... IEEE Transactions on Signal Processing journals http://www.medworm.com/rss/comments.php?id=5429409 Mon, 21 Nov 2011 00:47:21 +0100 5429409 http://www.medworm.com/index.php?rid=5429408&cid=s_38180_169_f&fid=38180&url=http%3A%2F%2Fieeexplore.ieee.org%2Fxpls%2Fabs_all.jsp%3Fisnumber%3D6069620%26arnumber%3D5986744 Dynamically allocating the available spectrum in the cognitive radio networks (CRN) where licensed users allow unlicensed users to make use of part of their allocated spectrum is a complex task. It requires, among others, that the interference generated by the CRN is well controlled. In this paper we address this problem for a particular type of interference constraints, in which the aggregated powers of the interference generated by the unlicensed network are required not to exceed certain thresholds. Traditional distributed “water filling” based spectrum allocation schemes are not well equipped to enforce such interference constraints. A natural extension to these algorithms involves penalizing each unlicensed user with a set of time-varying prices based upon its contributi... IEEE Transactions on Signal Processing journals http://www.medworm.com/rss/comments.php?id=5429408 Mon, 21 Nov 2011 00:47:21 +0100 5429408 http://www.medworm.com/index.php?rid=5429407&cid=s_38180_169_f&fid=38180&url=http%3A%2F%2Fieeexplore.ieee.org%2Fxpls%2Fabs_all.jsp%3Fisnumber%3D6069620%26arnumber%3D6016251 We address the problem of primary user detection in Cognitive Radio from a wideband signal comprising multiple primary channels, exploiting a priori knowledge about the primary network: channelization and spectral shape of primary transmissions. Using this second-order statistical information, a multichannel Gaussian model is formulated. In order to obtain a generalized likelihood ratio test, we first address maximum likelihood (ML) estimation of the power levels at the different channels, as well as of the noise variance. The ML conditions suggest a suboptimal closed-form estimate, which takes the form of a constrained least squares estimator whose asymptotic efficiency is shown for flat bandpass spectra in white noise, a case of practical importance. The resulting detectors exploit those... IEEE Transactions on Signal Processing journals http://www.medworm.com/rss/comments.php?id=5429407 Mon, 21 Nov 2011 00:47:21 +0100 5429407 http://www.medworm.com/index.php?rid=5429406&cid=s_38180_169_f&fid=38180&url=http%3A%2F%2Fieeexplore.ieee.org%2Fxpls%2Fabs_all.jsp%3Fisnumber%3D6069620%26arnumber%3D6016252 In a cognitive sensor network (CSN), selfish sensors can choose to conduct cooperative spectrum sensing (CSS) or local spectrum sensing (LSS). CSS usually improves sensing performance at the price of delay and energy consumption. A selfish sensor only decides to conduct CSS if it is more profitable than performing LSS. A key issue is how to achieve a desired decision outcome that maximizes spectrum utilization under the requirement of self-interest maximization and primary user (PU) protection. To address this problem, we formulate the interactive deciding of sensors as a noncooperative game, and Nash equilibrium (NE) corresponds to a stable decision outcome that no sensor has an incentive to resist unilaterally. It is shown that the desired decision outcome can be obtained by solving a co... IEEE Transactions on Signal Processing journals http://www.medworm.com/rss/comments.php?id=5429406 Mon, 21 Nov 2011 00:47:21 +0100 5429406 http://www.medworm.com/index.php?rid=5429405&cid=s_38180_169_f&fid=38180&url=http%3A%2F%2Fieeexplore.ieee.org%2Fxpls%2Fabs_all.jsp%3Fisnumber%3D6069620%26arnumber%3D6004843 Location fingerprinting utilizing ultrawideband (UWB) radio frequency (RF) signals is an attractive alternative to conventional positioning concepts based on range, angle, or received signal strength estimates. Such a location fingerprinting method proves particularly beneficial in indoor environments with dense multipath propagation and nonline-of-sight situations where conventional approaches would fail. The ultrawide bandwidth allows for location fingerprints with many degrees of freedom and thus gives the important advantage that a single anchor suffices for good localization performance. The downside is that a large amount of training data is usually required, which makes the training phase time-consuming and tedious. In this paper, we propose and study a novel and efficient training ... IEEE Transactions on Signal Processing journals http://www.medworm.com/rss/comments.php?id=5429405 Mon, 21 Nov 2011 00:47:21 +0100 5429405 http://www.medworm.com/index.php?rid=5429404&cid=s_38180_169_f&fid=38180&url=http%3A%2F%2Fieeexplore.ieee.org%2Fxpls%2Fabs_all.jsp%3Fisnumber%3D6069620%26arnumber%3D5985547 This paper introduces a novel method of spectrum sensing in communication systems that utilizes nonuniform sampling in conjunction with a suitable spectral analysis tool. It is referred to here as spectral analysis for randomized sampling (SARS). Owing to the deployment of nonuniform sampling, the proposed technique can accomplish the sensing task by using sampling rates well below the ones demanded by uniform-sampling-based digital signal processing (DSP). The effect of the cyclostationary nature of the incoming digital communication signal on the adequacy of the adopted periodogram-type estimator for the spectrum sensing operation is addressed. The statistical characteristics of the estimator are presented. General reliability conditions on the length of the required signal observation w... IEEE Transactions on Signal Processing journals http://www.medworm.com/rss/comments.php?id=5429404 Mon, 21 Nov 2011 00:47:21 +0100 5429404 http://www.medworm.com/index.php?rid=5429403&cid=s_38180_169_f&fid=38180&url=http%3A%2F%2Fieeexplore.ieee.org%2Fxpls%2Fabs_all.jsp%3Fisnumber%3D6069620%26arnumber%3D6006541 This paper introduces a new multicarrier system using a low computational complexity transform that combines the Walsh-Hadamard transform (WHT) and the discrete Fourier transform (DFT) into a single fast orthonormal unitary transform. The proposed transform is used in a new orthogonal frequency division multiplexing ( ${rm T}$-OFDM) system, leading to a significant improvement in bit error rate (BER) and reasonable reduction in the peak-to-average power ratio (PAPR). Use of the proposed transform with OFDM has been found to attain high frequency diversity gain by combining all data samples resulting in the transmission over many subcarriers. Consequently, the detrimental effect arising from channel fading on the subcarrier power is minimized. Theoretical analysis of the uncoded ${rm T}$-OF... IEEE Transactions on Signal Processing journals http://www.medworm.com/rss/comments.php?id=5429403 Mon, 21 Nov 2011 00:47:21 +0100 5429403 http://www.medworm.com/index.php?rid=5429402&cid=s_38180_169_f&fid=38180&url=http%3A%2F%2Fieeexplore.ieee.org%2Fxpls%2Fabs_all.jsp%3Fisnumber%3D6069620%26arnumber%3D5985554 Full-duplex relaying is more spectrally efficient than half-duplex relaying as only one channel use is needed per two hops. However, it is crucial to minimize relay self-interference to render full duplex feasible. For this purpose, we analyze a broad range of multiple-input multiple-output (MIMO) mitigation schemes: natural isolation, time-domain cancellation, and spatial suppression. Cancellation subtracts replicated interference signal from the relay input while suppression reserves spatial dimensions for receive and transmit filtering. Spatial suppression can be achieved by antenna subset selection, null-space projection, i.e., receiving and transmitting in orthogonal subspaces, or joint transmit and receive beam selection to support more spatial streams by choosing the minimum eigenmo... IEEE Transactions on Signal Processing journals http://www.medworm.com/rss/comments.php?id=5429402 Mon, 21 Nov 2011 00:47:21 +0100 5429402 http://www.medworm.com/index.php?rid=5429401&cid=s_38180_169_f&fid=38180&url=http%3A%2F%2Fieeexplore.ieee.org%2Fxpls%2Fabs_all.jsp%3Fisnumber%3D6069620%26arnumber%3D6020816 In this paper, the problem of detecting a multi-channel signal in the presence of spatially and temporally colored disturbance is considered. By modeling the disturbance as a multi-channel auto-regressive (AR) process with a random cross-channel (spatial) covariance matrix, two knowledge-aided parametric adaptive detectors are developed within a Bayesian framework. The first knowledge-aided parametric detector is developed using an ad hoc two-step procedure for the estimation of the signal and disturbance parameters, which leads to a successive spatio-temporal whitening process. The second knowledge-aided parametric detector takes a joint approach for the estimation of the signal and disturbance parameters, which leads to a joint spatio-temporal whitening process. Both knowledge-aided para... IEEE Transactions on Signal Processing journals http://www.medworm.com/rss/comments.php?id=5429401 Mon, 21 Nov 2011 00:47:21 +0100 5429401 http://www.medworm.com/index.php?rid=5429400&cid=s_38180_169_f&fid=38180&url=http%3A%2F%2Fieeexplore.ieee.org%2Fxpls%2Fabs_all.jsp%3Fisnumber%3D6069620%26arnumber%3D6020817 We propose a novel approach to the design of array geometries for azimuthal direction-of-arrival (DOA) estimation. The proposed array design is related to that of minimum redundancy arrays, but the array sensors are not required to lie on a uniform grid. Based on the proposed array geometry design, we develop a subspace-based DOA estimation technique, which allows to estimate the DOAs of more sources than sensors, using only second-order statistics of the received data. This DOA estimation technique is related to the covariance augmentation technique, but in contrast to the latter technique, it provides nonambiguous DOA estimates for the full 360 $^{circ}$ azimuth field-of-view. (Source: IEEE Transactions on Signal Processing) IEEE Transactions on Signal Processing journals http://www.medworm.com/rss/comments.php?id=5429400 Mon, 21 Nov 2011 00:47:20 +0100 5429400 http://www.medworm.com/index.php?rid=5429399&cid=s_38180_169_f&fid=38180&url=http%3A%2F%2Fieeexplore.ieee.org%2Fxpls%2Fabs_all.jsp%3Fisnumber%3D6069620%26arnumber%3D5986746 In this paper, we consider the problem of direction of arrival (DOA) estimation in the presence of sensor gain-phase errors. Under some mild assumptions, we propose a new DOA estimation method based on the eigendecomposition of a covariance matrix which is constructed by the dot product of the array output vector and its conjugate. By combining the new DOA estimation with the conventional gain-phase error estimation, a method is proposed to simultaneously estimate the DOA and gain-phase errors without joint iteration. Theoretical analysis shows that the proposed method performs independently of phase errors and thus behaves well regardless of phase errors. However, the resolution capability of the proposed method is lower than that of the method in [A. J. Weiss and B. Friedlander, “... IEEE Transactions on Signal Processing journals http://www.medworm.com/rss/comments.php?id=5429399 Mon, 21 Nov 2011 00:47:20 +0100 5429399 http://www.medworm.com/index.php?rid=5429398&cid=s_38180_169_f&fid=38180&url=http%3A%2F%2Fieeexplore.ieee.org%2Fxpls%2Fabs_all.jsp%3Fisnumber%3D6069620%26arnumber%3D5985550 The analysis of the fully three-dimensional and time-varying polarization characteristics of a modulated trivariate, or three-component, oscillation is addressed. The use of the analytic operator enables the instantaneous three-dimensional polarization state of any square-integrable trivariate signal to be uniquely defined. Straightforward expressions are given which permit the ellipse parameters to be recovered from data. The notions of instantaneous frequency and instantaneous bandwidth, generalized to the trivariate case, are related to variations in the ellipse properties. Rates of change of the ellipse parameters are found to be intimately linked to the first few moments of the signal's spectrum, averaged over the three signal components. In particular, the trivariate instantaneous ba... IEEE Transactions on Signal Processing journals http://www.medworm.com/rss/comments.php?id=5429398 Mon, 21 Nov 2011 00:47:20 +0100 5429398 http://www.medworm.com/index.php?rid=5429397&cid=s_38180_169_f&fid=38180&url=http%3A%2F%2Fieeexplore.ieee.org%2Fxpls%2Fabs_all.jsp%3Fisnumber%3D6069620%26arnumber%3D6004842 This paper is concerned with spherically invariant or elliptically contoured vector random fields in space and/or time, which are formulated as scale mixtures of vector Gaussian random fields. While a spherically invariant vector random field may or may not have second-order moments, a spherically invariant second-order vector random field is determined by its mean and covariance matrix functions, just like the Gaussian one. This paper explores basic properties of spherically invariant second-order vector random fields, and proposes an efficient approach to develop covariance matrix functions for such vector random fields. (Source: IEEE Transactions on Signal Processing) IEEE Transactions on Signal Processing journals http://www.medworm.com/rss/comments.php?id=5429397 Mon, 21 Nov 2011 00:47:20 +0100 5429397 http://www.medworm.com/index.php?rid=5429396&cid=s_38180_169_f&fid=38180&url=http%3A%2F%2Fieeexplore.ieee.org%2Fxpls%2Fabs_all.jsp%3Fisnumber%3D6069620%26arnumber%3D5997322 Volterra and polynomial regression models play a major role in nonlinear system identification and inference tasks. Exciting applications ranging from neuroscience to genome-wide association analysis build on these models with the additional requirement of parsimony. This requirement has high interpretative value, but unfortunately cannot be met by least-squares based or kernel regression methods. To this end, compressed sampling (CS) approaches, already successful in linear regression settings, can offer a viable alternative. The viability of CS for sparse Volterra and polynomial models is the core theme of this work. A common sparse regression task is initially posed for the two models. Building on (weighted) Lasso-based schemes, an adaptive RLS-type algorithm is developed for sparse pol... IEEE Transactions on Signal Processing journals http://www.medworm.com/rss/comments.php?id=5429396 Mon, 21 Nov 2011 00:47:20 +0100 5429396 http://www.medworm.com/index.php?rid=5429395&cid=s_38180_169_f&fid=38180&url=http%3A%2F%2Fieeexplore.ieee.org%2Fxpls%2Fabs_all.jsp%3Fisnumber%3D6069620%26arnumber%3D6021385 The present paper is a continuing work on the recently established adaptive Fourier decomposition (AFD) mainly stressing on the algorithm aspect, including algorithm analysis and numerical examples. AFD is a variation and realization of greedy algorithm (matching pursuit) suitable for the Hardy $H^{2}$ and the $L^{2}$ spaces. Applying AFD to a given signal, one obtains a series expansion in the basic signals, called mono-components, that possess non-negative analytic phase derivatives (functions), or, equivalently, meaningful analytic instantaneous frequencies. AFD is shown to be robust with computational complexity comparable with DFT. Consistent to the greedy algorithm principle experiments show that AFD produces (pre-) mono-component series with efficient energy decay that also leads to... IEEE Transactions on Signal Processing journals http://www.medworm.com/rss/comments.php?id=5429395 Mon, 21 Nov 2011 00:47:20 +0100 5429395 http://www.medworm.com/index.php?rid=5429394&cid=s_38180_169_f&fid=38180&url=http%3A%2F%2Fieeexplore.ieee.org%2Fxpls%2Fabs_all.jsp%3Fisnumber%3D6069620%26arnumber%3D5985548 In signal processing, data analysis and scientific computing, one often encounters the problem of decomposing a tensor into a sum of contributions. To solve such problems, both the search direction and the step size are two crucial elements in numerical algorithms, such as alternating least squares algorithm (ALS). Owing to the nonlinearity of the problem, the often used linear search direction is not always powerful enough. In this paper, we propose two higher-order search directions. The first one, geometric search direction, is constructed via a combination of two successive linear directions. The second one, algebraic search direction, is constructed via a quadratic approximation of three successive iterates. Then, in an enhanced line search along these directions, the optimal complex ... IEEE Transactions on Signal Processing journals http://www.medworm.com/rss/comments.php?id=5429394 Mon, 21 Nov 2011 00:47:20 +0100 5429394 http://www.medworm.com/index.php?rid=5429393&cid=s_38180_169_f&fid=38180&url=http%3A%2F%2Fieeexplore.ieee.org%2Fxpls%2Fabs_all.jsp%3Fisnumber%3D6069620%26arnumber%3D6006544 We develop a novel sampling theorem on the sphere and corresponding fast algorithms by associating the sphere with the torus through a periodic extension. The fundamental property of any sampling theorem is the number of samples required to represent a band-limited signal. To represent exactly a signal on the sphere band-limited at $L$, all sampling theorems on the sphere require ${cal O}({L}^{2})$ samples. However, our sampling theorem requires less than half the number of samples of other equiangular sampling theorems on the sphere and an asymptotically identical, but smaller, number of samples than the Gauss-Legendre sampling theorem. The complexity of our algorithms scale as ${cal O}({L}^{3})$, however, the continual use of fast Fourier transforms reduces the constant prefactor associa... IEEE Transactions on Signal Processing journals http://www.medworm.com/rss/comments.php?id=5429393 Mon, 21 Nov 2011 00:47:20 +0100 5429393 http://www.medworm.com/index.php?rid=5429392&cid=s_38180_169_f&fid=38180&url=http%3A%2F%2Fieeexplore.ieee.org%2Fxpls%2Fabs_all.jsp%3Fisnumber%3D6069620%26arnumber%3D6006545 Theoretical analysis of randomized, compressive operators often depends on a concentration of measure inequality for the operator in question. Typically, such inequalities quantify the likelihood that a random matrix will preserve the norm of a signal after multiplication. Concentration of measure results are well established for unstructured compressive matrices, populated with independent and identically distributed (i.i.d.) random entries. Many real-world acquisition systems, however, are subject to architectural constraints that make such matrices impractical. In this paper we derive concentration of measure bounds for two types of block diagonal compressive matrices, one in which the blocks along the main diagonal are random and independent, and one in which the blocks are random but ... IEEE Transactions on Signal Processing journals http://www.medworm.com/rss/comments.php?id=5429392 Mon, 21 Nov 2011 00:47:20 +0100 5429392 http://www.medworm.com/index.php?rid=5429391&cid=s_38180_169_f&fid=38180&url=http%3A%2F%2Fieeexplore.ieee.org%2Fxpls%2Fabs_all.jsp%3Fisnumber%3D6069620%26arnumber%3D6021388 A novel framework of compressed sensing, namely statistical compressed sensing (SCS), that aims at efficiently sampling a collection of signals that follow a statistical distribution, and achieving accurate reconstruction on average, is introduced. SCS based on Gaussian models is investigated in depth. For signals that follow a single Gaussian model, with Gaussian or Bernoulli sensing matrices of ${cal O}(k)$ measurements, considerably smaller than the ${cal O}(k log(N/k))$ required by conventional CS based on sparse models, where $N$ is the signal dimension, and with an optimal decoder implemented via linear filtering, significantly faster than the pursuit decoders applied in conventional CS, the error of SCS is shown tightly upper bounded by a constant times the best $k$-term approximati... IEEE Transactions on Signal Processing journals http://www.medworm.com/rss/comments.php?id=5429391 Mon, 21 Nov 2011 00:47:20 +0100 5429391 http://www.medworm.com/index.php?rid=5429390&cid=s_38180_169_f&fid=38180&url=http%3A%2F%2Fieeexplore.ieee.org%2Fxpls%2Fabs_all.jsp%3Fisnumber%3D6069620%26arnumber%3D5993553 Two-sided diagonal scaling for transfer matrices is formulated. An efficient algorithm is proposed to compute globally optimal solutions using the iterated bi-section and linear matrix inequality (LMI) solver. It is shown that the two-sided scaling of filter bank (FB) frames can be implemented by the adjustment of channel gains and the periodic precoding of source signal, and that the frame-bound-ratio of FB frames can be effectively improved by such scaling. Explicit formulas are established for both uniform and nonuniform FB frames, including detail formulas for discrete Weyl-Heisenberg frames and tree-structured FBs (discrete wavelets). Different examples show the effectiveness of the obtained results. (Source: IEEE Transactions on Signal Processing) IEEE Transactions on Signal Processing journals http://www.medworm.com/rss/comments.php?id=5429390 Mon, 21 Nov 2011 00:47:20 +0100 5429390 http://www.medworm.com/index.php?rid=5429389&cid=s_38180_169_f&fid=38180&url=http%3A%2F%2Fieeexplore.ieee.org%2Fxpls%2Fabs_all.jsp%3Fisnumber%3D6069620%26arnumber%3D6006546 We study the feasibility of short finite impulse response (FIR) synthesis for perfect reconstruction (PR) in generic FIR filter banks. Among all PR synthesis banks, we focus on the one with the minimum filter length. For filter banks with oversampling factors of at least two, we provide prescriptions for the shortest filter length of the synthesis bank that would guarantee PR almost surely. The prescribed length is as short or shorter than the analysis filters and has an approximate inverse relationship with the oversampling factor. Our results are in form of necessary and sufficient statements for PR feasibility that hold generically, hence only fail for elaborately designed nongeneric examples. We provide extensive numerical verification of the theoretical results and demonstrate that th... IEEE Transactions on Signal Processing journals http://www.medworm.com/rss/comments.php?id=5429389 Mon, 21 Nov 2011 00:47:20 +0100 5429389 http://www.medworm.com/index.php?rid=5429388&cid=s_38180_169_f&fid=38180&url=http%3A%2F%2Fieeexplore.ieee.org%2Fxpls%2Fabs_all.jsp%3Fisnumber%3D6069620%26arnumber%3D6016246 In this paper, we aim at finding the conditions that an oversampled filter bank (OFB) should satisfy, in order to maintain its perfect reconstruction property when erasures happen in the subband domain. This problem has been addressed before mainly from frame-theoretic point of view and only for the case of what we call in this paper classic erasure. In the frame-theoretic approach, the stable filter banks are associated with frames in $ell^{2}(BBZ)$ and a subband erasure is defined as the deletion of the frame expansion coefficients corresponding to the frame vectors resulting from each filter and all its translated versions. This is equivalent to assuming that all the samples of a subband have been completely lost (classic erasure) and this is why in this approach it is always assumed th... IEEE Transactions on Signal Processing journals http://www.medworm.com/rss/comments.php?id=5429388 Mon, 21 Nov 2011 00:47:20 +0100 5429388