joint source channel coding with side information using hybrid digital analog codes we study the joint source channel coding problem of transmitting a gaussian source over a gaussian channel in two cases i the presence of interference known only to the transmitter and ii in the presence of side information about the source known only to the receiver we introduce hybrid digital analog forms of the costa and wyner ziv coding schemes we present the random coding counterpart of schemes based on lattices proposed by kochman and zamir then we discuss applications of the hybrid digital analog schemes in the case of channel signal to noise ratio mismatch and for lossy multicasting of a common source with bandwidth compression

multi grid algorithms with applications to elliptic boundary value problems this work is primarily concerned with solving the large sparse linear systems which arise in connection with finite element or finite difference procedures for solving self adjoint elliptic boundary value problems these problems can be expressed in terms of abstract variational problems on hilbert spaces our mufti grid schemes involve a sequence of auxiliary finite dimensional spaces which do not have to be nested we approximate the solution using the largest finite dimensional space these schemes are recursive in nature they combine smoothing iterations in a space with solving one or more correction problems using smaller spaces under certain circumstances the solution to a problem can be approximated well using smaller spaces since the smaller spaces are required to have geometrically fewer unknowns than the largest space the savings in computation can be substantial in fact we prove that these procedures are optimal order under appropriate conditions our general theory is discretization

preconditioned conjugate gradient methods for three dimensional linear elasticity finite element modelling of three dimensional elasticity problems give rise to large sparse matrices various preconditioning methods are developed for use in preconditioned conjugate gradient iterative solution techniques incomplete factorizations based on levels of fill drop tolerance and a two level hierarchical basis are developed various techniques for ensuring that the incomplete factors have positive pivots are presented computational tests are carried out for problems generated using unstructured tetrahedral meshes quadratic basis functions are used the performance of the iterative methods is compared to a standard direct sparse matrix solver problems with up to 70 000 degrees of freedom and small 1 element aspect ratio are considered

a proof of marton s coding theorem for the discrete memoryless broadcast channel corresp a simple proof using random partitions and typicality is given for marton s coding theorem for broadcast channels

spatial frequency signal alignment for opportunistic transmission in this paper we investigate opportunistic transmission based on signal alignment for multiple input multiple output mimo orthogonal frequency division multiplexing ofdm cognitive radio cr systems where both primary and secondary users have multiple antennas in the studied scenario primary users are transmitting based on ofdm and secondary users generate interference free transmission to the primary users by using both the spatial and frequency space leftover by the primary system moreover inter and intra interference among secondary users are considered as well the number of symbols that can be transmitted by each secondary user satisfying all interference free constraints is obtained precoding matrix design will be discussed for perfectly and partially aligned transmission two chordal distance based schemes called as exhaustive search algorithm and heuristic algorithm will be developed for each case compared to the traditional time division multiple access tdma scheme the proposed scheme can support more interference free symbols to be transmitted by secondary users simultaneously

electromagnetic scattering from 3 d curved dielectric bodies using time domain integral equations a boundary integral equation bie approach is developed to calculate transient scattering from dielectric bodies the treatment is directly in terms of the e and h fields rather than magnetic and electric currents it employs curvilinear quadratic modeling which allows accurate representation of arbitrarily shaped curved bodies the treatment is isoparametric with the same quadratic representation of the spatial field variation and with the temporal variation modeled by similar quadratic elements integration employs high order gaussian quadrature with special treatment of the singular and hypersingular integrals that arise the treatment is implicit requiring the solution of a sparse matrix equation at each timestep this adds only trivially to the cost at each timestep and by freeing the timestep from the constraint that it be smaller than the smallest nodal spacing can greatly reduce the number of timesteps that must be employed additionally it produces stable results without resort to the averaging processes proposed elsewhere example calculations of scattering from a sphere a cube and an almond are presented and compared with earlier published transient results and with results from a frequency domain treatment good agreement and improved accuracy is found

antenna characterization in the time domain a theory for a complete far field transmit receive system characterization of short pulse antennas is derived in the time domain the transmit receive antenna system is characterized by a set of cascaded operators which transform the source waveform and power into similar quantities at the receiving antenna terminals two such sets are defined the first one is phrased in terms of the wave type time dependent effective height operator while the second one is defined in terms of the energy type gain operator both definitions fit within a complete transmit receive system description the latter being equivalent to the frequency domain friis equation however these operators are derived entirely in the context of the time domain field equation the starting point in the time domain analysis of the effective height is the slant stack transform sst of the time dependent current distribution in a manner equivalent to the spatial fourier transform used in the frequency domain the vector autocorrelation of the transmitting effective height is then used to define the time dependent gain operator under impulsive source excitation time domain reciprocity leads to the definitions of antenna parameters under receiving conditions and the corresponding equivalent circuit the parameters defined in this way fit within a consistent transmit receive convolution operator operating on the autocorrelation of the input signal this independent time domain representation is thus similar to the frequency domain representation however unlike the conventional frequency domain circuit parameters which relate voltage and current amplitudes the time domain circuit representation is based on incident and reflected wave type constituents in addition the use of appropriate norms facilitates the transformation of our operators to stand alone figures of merits the general concepts developed are demonstrated for a short dipole antenna

a general incomplete block matrix factorization method abstract a general method for incomplete factorization of m matrices in block matrix form is presented the method generalizes previous methods for pointwise incomplete factorization methods of varga 1960 of wo nicki 1973 and of meijerink and van der vorst 1977 as well as a method for tridiagonal block matrices also we present a new and more general result on the existence of so called modified incomplete factorizations which satisfy a generalized rowsum criterion

multilevel aggregation method for solving large scale generalized eigenvalue problems in structural dynamics in this paper a novel iterative method of multilevel type for solving large scale generalized eigenvalue problems encountered in structural dynamics is presented a preconditioned iterative technique which can be viewed as a modification of the subspace iteration method is used for simultaneous calculation of a group of lowest modes and frequencies the paper demonstrates that a coarse aggregation model can be employed in the hierarchical structure of the preconditioner in order to provide a good resemblance of the latter to the stiffness matrix of the finite element approximation with respect to low frequency modes this leads to a fast convergent procedure of subspace iterations as opposed to the coarse grid used in methods of multigrid type this model allows for solving problems with different finite elements including reticulated structures in the framework of large comprehensive finite element software systems numerical experiments performed for three dimensional truss frame and solid structures demonstrate an excellent performance of the method 1997 by john wiley sons ltd

transient scattering from two dimensional dielectric cylinders of arbitrary shape the problem of transient scattering by arbitrarily shaped two dimensional dielectric cylinders is solved using the marching on in time technique the dielectric problem is approached via the surface equivalence principle two coupled integral equations are derived by enforcing the continuity of the electric and magnetic fields which are solved by using the method of moments numerical results are presented for two cross sections viz a circle and a square and compared with inverse discrete fourier transform idft techniques in each case good agreement is obtained with the idft solution

high performance multilevel iterative aggregation solver for large finite element structural analysis problems the present study is aimed to overcome difficulties faced with industrial applications of multilevel iterative methods to arbitrary finite element fe structural analysis problems the coarse grid concept used in multigrid methods is substituted with an aggregation coarse model based on the mechanical principle on the base of this approach together with previously developed multilevel preconditioner an efficient iterative equation solver feags was developed for using in standard comprehensive finite element software systems numerical examples for analyses of three dimensional 3 d frame structures demonstrate the efficiency of the method comparison with incomplete cholesky conjugate gradient iccg method and direct methods is presented

low complexity user selection algorithms for multiuser mimo systems with block diagonalization block diagonalization bd is a precoding technique that eliminates interuser interference in downlink multiuser multiple input multiple output mimo systems with the assumptions that all users have the same number of receive antennas and utilize all receive antennas when scheduled for transmission the number of simultaneously supportable users with bd is limited by the ratio of the number of base station transmit antennas to the number of user receive antennas in a downlink mimo system with a large number of users the base station may select a subset of users to serve in order to maximize the total throughput the brute force search for the optimal user set however is computationally prohibitive we propose two low complexity suboptimal user selection algorithms for multiuser mimo systems with bd both algorithms aim to select a subset of users such that the total throughput is nearly maximized the first user selection algorithm greedily maximizes the total throughput whereas the criterion of the second algorithm is based on the channel energy we show that both algorithms have linear complexity in the total number of users and achieve around 95 of the total throughput of the complete search method in simulations

on the use of spatio temporal multiresolution analysis in method of moments solutions of transient electromagnetic scattering a novel method of moments approach to the solution of time domain integral equation formulation of electromagnetic scattering problems is presented the method is based on a spatio temporal multiresolution analysis this analysis facilitates a basis from which a small number of expansion functions is selected via an iterative procedure and utilized to model the unknown current distribution in contrast to marching on in time sequential procedures the proposed method models the unknown current simultaneously at all the time steps within the time frame of interest this new method is applied to a one dimensional 1 d problem of electromagnetic plane wave interaction with a dielectric slab a comparison of the computed results with results based on the analytic solution demonstrates that the method is capable of attaining accurate results while achieving substantial reduction in computation time and resources

achievable rates of multi antenna downlink channels with peak power constraints this paper considers a gaussian multiple input single output miso broadcast channel with a per antenna peak power constraint or simply peak power constraint it is more realistic to consider the peak power constraint on each transmit antenna because in many practical implementations each antenna is equipped with its own power amplifier assuming the perfect knowledge of the channel state information csi at the transmitter we propose an achievable scheme using dirty tape coding dtc the ideal dirty paper coding dpc which is a capacity achieving scheme for the gaussian multiple input multiple output mimo broadcast channel cannot be used for our model because its optimal input distribution is gaussian and thus the peak power constraint is violated on the other hand the channel input of dtc is uniformly distributed in a fixed range which helps to control the peak power of the transmit signal easily we also present an algorithm that finds capacity achieving beamforming vectors and power allocation factors under a per antenna average power constraint and use the optimized parameters in the proposed scheme simulation results show that the proposed scheme provides gains of 2 7db over a non dtc scheme based on minimum mean square error mmse beamforming at high signal to noise ratio snr when there are three receivers and the transmitter has three antennas

quantization based methods additive attacks performance analysis the main goal of this study consists in the development of the worst case additive attack wcaa for ary quantization based data hiding methods using as design criteria the error probability and the maximum achievable rate of reliable communications our analysis focuses on the practical scheme known as distortion compensated dither modulation dc dm from the mathematical point of view the problem of the worst case attack wca design using probability of error as a cost function is formulated as the maximization of the average probability of error subject to the introduced distortion for a given decoding rule when mutual information is selected as a cost function a solution of the minimization problem should provide such an attacking noise probability density function pdf that will maximally decrease the rate of reliable communications for an arbitrary decoder structure the obtained results demonstrate that within the class of additive attacks the developed attack leads to a stronger performance decrease for the considered class of embedding techniques than the additive white gaussian or uniform noise attacks

algorithms for construction of preconditioners based on incomplete block factorizations of the matrix when applying an incomplete block factorization technique one needs sparse approximate inverses of the successive schur complements computed throughout the factorization here we propose a method for the construction of such sparse approximate inverses the method has an advantage over earlier versions in that such approximate inverses of block tridiagonal matrices can be computed in parallel comparative numerical experiments for solving a number of discretized diffusion equations by this preconditioning matrix in a preconditioned conjugate gradient method and earlier versions of incomplete block factorization preconditioners are presented

coarse division transform based preconditioner for boundary element problems this paper is devoted to the development of efficient preconditioners for an iterative solution of equation sets arising in the boundary element method bem a standard collocation system of equations is transformed to a new basis associated with an auxiliary coarse division model for boundary unknowns and solved in this basis new systems have rapidly decreasing coefficients and by neglecting a large number of them it is possible to construct readily invertible sparse preconditioners for iterative procedures the specific features of the transformed matrix can be attributed to the analytical properties of integral equations although the transformation is based on an auxiliary coarse division model it does not require any additional operations with boundary elements all manipulations necessary to construct the mapping are performed on the level of algebraic equations numerical experiments included in the paper confirm a high rate of convergence of the developed iterative scheme

impedance matrix compression imc using iteratively selected wavelet basis we present a novel approach for the incorporation of wavelets into the solution of frequency domain integral equations arising in scattering problems in this approach we utilize the fact that when the basis functions used are wavelet type functions only a few terms in a series expansion are needed to represent the unknown quantity to determine these dominant expansion functions an iterative procedure is devised the new approach combined with the iterative procedure yields a new algorithm that has many advantages over the presently used methods for incorporating wavelets numerical results which illustrate the approach are presented for three scattering problems

on the multi grid technique for solving three dimensional boundary value engineering problems the paper proposes an iterative technique with a similar multi grid operator for solving complex spatial bounctary value problems the description of the method and efficient vectorial algorithms based on a simple ctata structure applicable to solving three dimensional engineering problems are presented the discussion of the method s convergence includes theoretical grounds and practical aspects we give a general proof of convergence and consider the model cases to estimate the rate of convergence we also address the histories of convergence derived from the numerical tests and consider two examples of practical problems

user selection in mimo interfering broadcast channels interference alignment aims to achieve maximum degrees of freedom in an interference system for achieving interference alignment in interfering broadcast systems a closed form solution is proposed in which is an extension of the grouping scheme in in a downlink scenario where there are a large number of users the base station is required to select a subset of users such that the sum rate is maximized to search for the optimal user subset using brute force approach is computationally exhaustive because of the large number of possible user subset combinations we propose a user selection algorithm achieving sum rate close to that of optimal solution the algorithm employs coordinate ascent approach and exploits orthogonality between the desired signal space and the interference channel space in the reciprocal system to select the user at each step for the sake of completeness we have also extended the sum rate approach based algorithm to interfering broadcast channel the complexity of both these algorithms is shown to be linear with respect to the total number of users as compared to exponential in brute force search

on the use of spatio temporal wavelet expansions for transient analysis of wire antennas and scatterers to analyze a wire antenna excited by a time varying voltage source or a wire scatterer excitated by transient electromagnetic incident wave the problem is formulated in terms of a time domain integral equation for the induced current to solve the integral equation we reduce it to matrix equation via the method of moments using the known to be stable implicit scheme however rather than directly constructing and solving the relatively large matrix equation we propose an iterative procedure which allows us to gradually obtain a solution of refined accuracy both everywhere and simultaneously at any time instance to render this procedure rapidly converging we use a basis of spatio temporal wavelet functions this basis facilitates a good approximation of the induced current using far less basis functions than would be needed if other expansions such as standard pulse or fourier basis functions were chosen the use of this basis further enables the iterative procedure to increase the temporal and spatial resolutions where required without unnecessarily affecting their levels elsewhere

zero forcing methods for downlink spatial multiplexing in multiuser mimo channels the use of space division multiple access sdma in the downlink of a multiuser multiple input multiple output mimo wireless communications network can provide a substantial gain in system throughput the challenge in such multiuser systems is designing transmit vectors while considering the co channel interference of other users typical optimization problems of interest include the capacity problem maximizing the sum information rate subject to a power constraint or the power control problem minimizing transmitted power such that a certain quality of service metric for each user is met neither of these problems possess closed form solutions for the general multiuser mimo channel but the imposition of certain constraints can lead to closed form solutions this paper presents two such constrained solutions the first referred to as block diagonalization is a generalization of channel inversion when there are multiple antennas at each receiver it is easily adapted to optimize for either maximum transmission rate or minimum power and approaches the optimal solution at high snr the second known as successive optimization is an alternative method for solving the power minimization problem one user at a time and it yields superior results in some e g low snr situations both of these algorithms are limited to cases where the transmitter has more antennas than all receive antennas combined in order to accommodate more general scenarios we also propose a framework for coordinated transmitter receiver processing that generalizes the two algorithms to cases involving more receive than transmit antennas while the proposed algorithms are suboptimal they lead to simpler transmitter and receiver structures and allow for a reasonable tradeoff between performance and complexity

on the use of wavelet expansions in the method of moments em scattering an approach which incorporates the theory of wavelet transforms in method of moments solutions for electromagnetic wave interaction problems is presented the unknown field or response is expressed as a twofold summation of shifted and dilated forms of a properly chosen basis function which is often referred to as the mother wavelet the wavelet expansion can adaptively fit itself to the various length scales associated with the scatterer by distributing the localized functions near the discontinuities and the more spatially diffused ones over the smooth expanses of the scatterer the approach is thus best suited for the analysis of scatterers which contain a broad spectrum of length scales ranging from a subwavelength to several wavelengths using a galerkin method and subsequently applying a threshold procedure the moment method matrix is rendered sparsely populated the structure of the matrix reveals the localized scale fitting distribution long before the matrix equation is solved the performance of the proposed discretization scheme is illustrated by a numerical study of electromagnetic coupling through a double slot aperture

achievable rates for multiple descriptions consider a sequence of independent identically distributed i i d random variables x l x 2 cdots x n and a distortion measure d x i x i on the estimates x i of x i two descriptions i x in 1 2 cdots 2 nr 1 and j x in 1 2 cdots 2 nr 2 are given of the sequence x x 1 x 2 cdots x n from these two descriptions three estimates i x x2 j x and hat x o i x j x are formed with resulting expected distortions e frac 1 n sum n k 1 d x k hat x mk d m m 0 1 2 we find that the distortion constraints d 0 d 1 d 2 are achievable if there exists a probability mass distribution p x p hat x 1 hat x 2 hat x 0 x with ed x hat x m leq d m such that r 1 i x hat x 1 r 2 i x hat x 2 where i cdot denotes shannon mutual information these rates are shown to be optimal for deterministic distortion measures

on approximate factorization methods for block matrices suitable for vector and parallel processors abstract some existence results for methods based on the approximate factorization of block matrices are proven these methods are based on recursive computations of diagonal block matrices and the approximation of their inverses to preserve sparsity we also discuss a recently proposed 1 inverse free factorization method and present some numerical tests for it

on the stability of time marching schemes for the general surface electric field integral equation we demonstrate that time marching algorithms which use the electric field integral equation to compute the current induced on a perfect conductor by a transient electric field may have unstable modes that are due to the particular basis functions used to represent the current on the conductor these modes are not removed by averaging the solution in time but they can be eliminated by averaging in space appropriately

a user selection algorithm using angle between subspaces for downlink mu mimo systems one of major issues in the efficient use of radio resource for multiuser multiple input multiple output mu mimo systems is the selection of users to achieve the maximum system throughput the optimal user selection algorithm which requires exhaustive search is prohibitive due to its high computational complexity where block diagonalization bd method is applied and known as a suboptimal precoding technique for downlink mu mimo systems which intents to perfectly eliminate inter user interference in this paper we propose efficient iterative user selection algorithms with low complexity where the product of eigenvalues of effective channels is utilized as a selection metric by applying the concept of principal angles between subspaces and we further examined the applicability of the proposed algorithms to limited feedback systems and proportional fair pf scheduling through computational complexity analysis we show that the proposed algorithm has low complexity with a little loss in throughput simulation results validate that the proposed algorithm achieves almost the same system throughput by a capacity based algorithm under high snr regime with considerable reduction in complexity

a hierarchical iterative procedure for the analysis of composite laminates a multilevel recursively defined preconditioner for use with the preconditioned conjugate gradient pcg algorithm is developed and applied to solve thin and thick laminated plate problems the preconditioner is constructed from a sequence of hierarchical vector spaces arising from the p version of the finite element fe method numerical studies have been conducted using quadrilateral elements for two dimensional problems up to p 8 and serendipity brick elements for three dimensional problems up to p 5 the efficiency of the iterative procedure is illustrated using bending response of laminated plates the effects of element span ratios convergence tolerance polynomial order material properties and plate span ratios on the number of iterations required for convergence has been investigated results indicate that the preconditioner developed herein can be used to produce an efficient iterative solver for two and three dimensional problems in structural mechanics

writing on dirty paper corresp a channel with output y x s z is examined the state s sim n 0 qi and the noise z sim n 0 ni are multivariate gaussian random variables i is the identity matrix the input x in r n satisfies the power constraint l n sum i 1 n x i 2 leq p if s is unknown to both transmitter and receiver then the capacity is frac 1 2 ln 1 p n q nats per channel use however if the state s is known to the encoder the capacity is shown to be c ast frac 1 2 ln 1 p n independent of q this is also the capacity of a standard gaussian channel with signal to noise power ratio p n therefore the state s does not affect the capacity of the channel even though s is unknown to the receiver it is shown that the optimal transmitter adapts its signal to the state s rather than attempting to cancel it

impedance matrix compression using adaptively constructed basis functions wavelet expansions have been employed recently in numerical solutions of commonly used frequency domain integral equations in this paper we propose a novel method for integrating wavelet based transforms into existing numerical solvers the newly proposed method differs from the presently used ones in two ways first the transformation is affected by means of a digital filtering approach this approach renders the transform algorithm adaptive and facilitates the derivation of a basis which best suits the problem at hand second the conventional thresholding procedure applied to the impedance matrix is substituted for by a compression process in which only the significant terms in the expansion of the yet unknown current are retained and subsequently derived numerical results for a few tm scattering problems are included to demonstrate the advantages of the proposed method over the presently used ones

a marching on in time hierarchical scheme for the solution of the time domain electric field integral equation a spatially hierarchical current expansion is used to construct a marching on in time based time domain electric field integral equation solver the formulation gives rise to well conditioned linear systems and is immune to time domain low frequency breakdown phenomena numerical results that demonstrate the effectiveness of the proposed hierarchical approach in comparison with existing technologies are presented

towards a stable two dimensional time domain source model solution by use of a combined source formulation the application of the source model technique to the solution of two dimensional 2 d transient scattering problems directly in the time domain is described special attention is given to the accuracy and the stability of the numerical solution scheme a detailed comparison is made between the more often used single type source solution scheme and a newly proposed combined source solution scheme it is found that the combined source scheme can offer a significant advantage in terms of stability without any appreciable loss in accuracy over the single type source scheme

transient analysis of em pulse penetration into a conducting layer using wavelet based implicit tdie and iterative imc technique the penetration of a wide band electromagnetic pulse into a conducting layer is formulated in terms of an implicit time domain integral equation and cast into matrix form via the method of moments though such a wide band problem indeed calls for a time domain solution one may argue that the frequency dependent attenuation of the field penetrating the conductor could suggest a frequency domain approach that would greatly reduce the number of unknowns the proposed via media is to use spatio temporal wavelet functions instead of the standard pulse basis owing to their multiresolution property both in the spatial and temporal domains these functions can span the field propagating inwardly with substantially fewer terms the reduction in the number of basis functions used is effected by the impedance matrix compression technique which automatically omits the basis functions whose coefficients would be insignificant due to the attenuation reducing the number of basis functions renders the matrix equation much smaller and the overall solution far more efficient

multiuser mimo user selection based on chordal distance multiuser mimo mu mimo systems have advantages over single user mimo systems in terms of system performance in mu mimo systems inter user interference needs to be dealt with especially when linear processing is used the block diagonalization bd method is one of techniques that are widely used to eliminate the inter user interference in a cellular system where there are many users the subset of users which maximizes the system performance should be selected since the base station cannot support all the users in the cell in this paper we propose a low complexity mu mimo scheduling scheme using bd with chordal distance for a large number of users the optimal scheduling technique needs an exhaustive search which is impractical one of the key ideas of this paper is to use chordal distance as a measure of orthogonality between different users simulation results show the proposed algorithm has throughput close to the optimal scheduling scheme with lower complexity than existing low complexity scheduling algorithms