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

transmitter optimization for the multi antenna downlink with per antenna power constraints this paper considers the transmitter optimization problem for a multiuser downlink channel with multiple transmit antennas at the base station in contrast to the conventional sum power constraint on the transmit antennas this paper adopts a more realistic per antenna power constraint because in practical implementations each antenna is equipped with its own power amplifier and is limited individually by the linearity of the amplifier assuming perfect channel knowledge at the transmitter this paper investigates two different transmission schemes under the per antenna power constraint a minimum power beamforming design for downlink channels with a single antenna at each remote user and a capacity achieving transmitter design for downlink channels with multiple antennas at each remote user it is shown that in both cases the per antenna downlink transmitter optimization problem may be transformed into a dual uplink problem with an uncertain noise this generalizes previous uplink downlink duality results and transforms the per antenna transmitter optimization problem into an equivalent minimax optimization problem further it is shown that various notions of uplink downlink duality may be unified under a lagrangian duality framework this new interpretation of duality gives rise to efficient numerical optimization techniques for solving the downlink per antenna transmitter optimization problem

duality between channel capacity and rate distortion with two sided state information we show that the duality between channel capacity and data compression is retained when state information is available to the sender to the receiver to both or to neither we present a unified theory for eight special cases of channel capacity and rate distortion with state information which also extends existing results to arbitrary pairs of independent and identically distributed i i d correlated state information s sub 1 s sub 2 available at the sender and at the receiver respectively in particular the resulting general formula for channel capacity c max sub p u x s sub 1 i u s sub 2 y i u s sub 1 assumes the same form as the generalized wyner ziv 1976 rate distortion function r d min sub p u x s sub 1 p x spl i cap u s sub 2 i u s sub 1 x 1 u s sub 2

use of higher order shape functions in the scaled boundary finite element method the scaled boundary finite element method is a novel semi analytical technique whose versatility accuracy and efficiency are not only equal to but potentially better than the finite element method and the boundary element method for certain problems this paper investigates the possibility of using higher order polynomial functions for the shape functions two techniques for generating the higher order shape functions are investigated in the first the spectral element approach is used with lagrange interpolation functions in the second hierarchical polynomial shape functions are employed to add new degrees of freedom into the domain without changing the existing ones as in the p version of the finite element method to check the accuracy of the proposed procedures a plane strain problem for which an exact solution is available is employed a more complex example involving three scaled boundary subdomains is also addressed the rates of convergence of these examples under p refinement are compared with the corresponding rates of convergence achieved when uniform h refinement is used allowing direct comparison of the computational cost of the two approaches the results show that it is advantageous to use higher order elements and that higher rates of convergence can be obtained using p refinement instead of h refinement copyright 2005 john wiley sons ltd

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

the parallel gaussian watermarking game rates of reliable transmission of hidden information are derived for watermarking problems involving parallel gaussian sources which are often used to model host images and audio signals constraints are imposed on the average squared error distortion that can be introduced by the information hider and by the attacker when distortions are measured with respect to the original host data the optimal covert and attack channels are two banks of gaussian test channels the solution to the watermarking game involves an optimal allocation of distortions by the information hider and by the attacker to the different channels a fast algorithm is given for computing the optimal solution based on duality theory for each channel we derive analytical expressions for two asymptotic regimes weak and strong host signals finally we extend these results to the class of stationary gaussian host signals with bounded continuous spectral density the analysis also provides an upper bound on watermarking capacity for nongaussian host signals

from h to p efficiently implementing finite and spectral hp element methods to achieve optimal performance for low and high order discretisations the spectral hp element method can be considered as bridging the gap between the traditionally low order finite element method on one side and spectral methods on the other side consequently a major challenge which arises in implementing the spectral hp element methods is to design algorithms that perform efficiently for both low and high order spectral hp discretisations as well as discretisations in the intermediate regime in this paper we explain how the judicious use of different implementation strategies can be employed to achieve high efficiency across a wide range of polynomial orders furthermore based upon this efficient implementation we analyse which spectral hp discretisation which specific combination of mesh size h and polynomial order p minimises the computational cost to solve an elliptic problem up to a predefined level of accuracy we investigate this question for a set of both smooth and non smooth problems

a framework for evaluating the data hiding capacity of image sources an information theoretic model for image watermarking and data hiding is presented in this paper previous theoretical results are used to characterize the fundamental capacity limits of image watermarking and data hiding systems capacity is determined by the statistical model used for the host image by the distortion constraints on the data hider and the attacker and by the information available to the data hider to the attacker and to the decoder we consider autoregressive block dct and wavelet statistical models for images and compute data hiding capacity for compressed and uncompressed host image sources closed form expressions are obtained under sparse model approximations models for geometric attacks and distortion measures that are invariant to such attacks are considered

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

optimum allocation of treatments for welch s test in equivalence assessment as an extension of welch s test to equivalence trials in a matched pair design we determine the sample sizes n1 and n2 that maximize the power at given alternatives for a given total sample size n n1 n2 although the optimal allocation is obtained asymptotically when the ratio of the standard deviations in both treatment groups equals the ratio of the sample sizes numerical investigations show that this result does not hold for sample sizes where n or 25 for convenience we provide tables containing the optimal combinations for the bioequivalence problem as well as for the problem of testing a clinically relevant difference results indicate that for small sample sizes the optimum allocations of the treatments differ significantly in both testing problems although they are asymptotically identical in addition we provide simple approximate equations that can be used for the determination of the required sample sizes to control a preassigned probability of type ii error

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

superposition coding for side information channels we present simple practical codes designed for the binary and gaussian dirty paper channels we show that the dirty paper decoding problem can be transformed into an equivalent multiple access decoding problem for which we apply superposition coding our concept is a generalization of the nested lattices approach of zamir shamai and erez in a theoretical setting our constructions are capable of achieving capacity using random component codes and maximum likelihood decoding we also present practical implementations of the constructions and simulation results for both dirty paper channels our results for the gaussian dirty paper channel are on par with the best known results for nested lattices we discuss the binary dirty tape channel for which we present a simple effective coding technique finally we propose a framework for extending our approach to general gel fand pinsker channels

the computation of resonances in open systems using a perfectly matched layer in this paper we consider the problem of computing resonances in open systems we first characterize resonances in terms of improper eigen functions of the helmholtz operator on an unbounded domain the perfectly matched layer pml technique has been successfully applied to the computation of scattering problems we shall see that the application of pml converts the resonance problem to a standard eigenvalue problem still on an infinite domain this new eigenvalue problem involves an operator which resembles the original helmholtz equation transformed by a complex shift in the coordinate system our goal will be to approximate the shifted operator first by replacing the infinite domain by a finite computational domain with a convenient boundary condition and second by applying finite elements on the computational domain we shall prove that the first of these steps leads to eigenvalue convergence to the desired resonance values which is free from spurious computational eigenvalues provided that the size of computational domain is sufficiently large the analysis of the second step is classical finally we illustrate the behavior of the method applied to numerical experiments in one and two spatial dimensions

hybrid mu miso scheduling with limited feedback using hierarchical codebooks the multiuser mimo mu mimo systems tend to have inter user interference in practical systems with limited feedback practical mu mimo systems with limited feedback can be divided into two classes in general one is zero forcing beamforming zfbf and the other is per user unitary rate control pu2rc which is an extended version of random beamforming rbf to improve performance zfbf needs more feedback bits and pu2rc needs a larger number of users we propose a new hybrid mu miso system which has the advantages of the two mu mimo schemes simultaneously and analyze the sum rate performance and the quantization error of the hybrid scheme the analysis shows how the number of feedback bits the number of users and the signal power affect the sum rate the throughput scaling laws are also derived in the high and the medium snr regimes simulation results show that the proposed hybrid mu miso system performs better than either of the two mu mimo systems with the same number of feedback bits another advantage is that it has lower complexity for codeword search since it has a hierarchical codebook structure

on random coding error exponents of watermarking systems watermarking codes are analyzed from an information theoretic viewpoint as a game between an information hider and an active attacker while the information hider embeds a secret message watermark in a covertext message typically text image sound or video stream within a certain distortion level the attacker processes the resulting watermarked message within limited additional distortion in attempt to invalidate the watermark for the case where the covertext source is memoryless or more generally where there exists some transformation that makes it memoryless we provide a single letter characterization of the maximin game of the random coding error exponent associated with the average probability of erroneously decoding the watermark this single letter characterization is in effect because if the information hider utilizes a memoryless channel to generate random codewords for every covertext message the causal attacker will maximize the damage by implementing a memoryless channel as well partial results for the dual minimax game and the conditions for the existence of a saddle point are also presented

an improvement of commonly used tests in bioequivalence assessment if equivalence of two treatments has to be proved by an experiment with normally distributed observations and fixed sample size there are two usual methods on the one hand there is the double t test and on the other hand a test procedure suggested by anderson hauck which is uniformly more powerful than the first one but only capable of keeping asymptotically to the nominal level based on these two methods a new test is presented which is uniformly more powerful than the double t test and also keeps the preassigned level

analog matching of colored sources to colored channels analog uncoded transmission provides a simple and robust scheme for communicating a gaussian source over a gaussian channel under the mean squared error mse distortion measure unfortunately its performance is usually inferior to the all digital separation based source channel coding solution which requires exact knowledge of the channel at the encoder the loss comes from the fact that except for very special cases e g white source and channel of matching bandwidth bw it is impossible to achieve perfect matching of source to channel and channel to source by linear means we show that by combining prediction and modulo lattice operations it is possible to match any colored gaussian source to any colored gaussian noise channel of possibly different bw hence achieve shannon s optimum attainable performance r d c furthermore when the source and channel bws are equal but otherwise their spectra are arbitrary this scheme is asymptotically robust in the sense that for high signal to noise ratio snr a single encoder independent of the noise variance achieves the optimum performance the derivation is based upon a recent modulo lattice modulation scheme for transmitting a wyner ziv source over a dirty paper channel

on the capacity of the carbon copy onto dirty paper channel the carbon copy onto dirty paper ccdp channel is the compound writing on dirty paper channel in which the channel output is obtained as the sum of the channel input white gaussian noise and a gaussian state sequence randomly selected among a set possible realizations the transmitter has non causal knowledge of the set of possible state sequences but does not know which sequence is selected to produce the channel output we study the capacity of the ccdp channel for two scenarios 1 the state sequences are independent and identically distributed and 2 the state sequences are scaled versions of the same sequence in the first scenario we show that a combination of superposition coding time sharing and gel fand pinsker binning is sufficient to approach the capacity to within 3 bits per channel use for any number of possible state realizations in the second scenario we derive capacity to within 4 bits per channel use for the case of two possible state sequences this result is extended to the ccdp channel with any number of possible state sequences under certain conditions on the scaling parameters which we denote as strong fading regime we conclude by providing some remarks on the capacity of the ccdp channel in which the state sequences have any jointly gaussian distribution

welch s approximate solution for the behrens fisher problem the wald likelihood ratio and score statistics have been calculated for the behrens fisher problem these statistics provide asymptotically equivalent and weakly optimal tests the test based on the wald statistic was found to be very similar to the v test discussed by welch 1937 hence the v test was compared with the likelihood ratio and score tests in a power study since the powers were very similar and the v test was more convenient to use from several points of view we recommend this test sizes of the v test as well as a power comparison with the usual pooled t test were also obtained

multiple description quantization via gram schmidt orthogonalization the multiple description md problem has received considerable attention as a model of information transmission over unreliable channels a general framework for designing efficient md quantization schemes is proposed in this paper we provide a systematic treatment of the el gamal cover egc achievable md rate distortion region and show it can be decomposed into a simplified egc segc region and a superimposed refinement operation furthermore any point in the segc region can be achieved via a successive quantization scheme along with quantization splitting for the quadratic gaussian case the proposed scheme has an intrinsic connection with the gram schmidt orthogonalization which implies that the whole gaussian md rate distortion region is achievable with a sequential dithered lattice based quantization scheme as the dimension of the optimal lattice quantizers becomes large moreover this scheme is shown to be universal for all independent and identically distributed i i d smooth sources with performance no worse than that for an i i d gaussian source with the same variance and asymptotically optimal at high resolution a class of md scalar quantizers in the proposed general framework is also constructed and is illustrated geometrically the performance is analyzed in the high resolution regime which exhibits a noticeable improvement over the existing md scalar quantization schemes

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

vector perturbation based on symbol scaling for limited feedback miso downlinks we propose a low complexity vector precoding vp scheme for the downlink of multi user multiple input single output mu miso systems with limited feedback conventional vp requires the use of modulo operation and knowledge of the scaling factor used at the transmitter in order to remove the perturbation quantity at the receiver the latter may be problematic in certain limited feedback scenarios where only quantized versions of the scaling factor can be made available at the receiver to circumvent this shortcoming we propose a modified vp technique where the search of perturbing vectors is limited to the area in the symbol constellation which is constrictive to the information symbols i e the area where the distances from the decision thresholds are increased with respect to a distance threshold by doing this the perturbation quantities can only enhance detection and need not be removed at the receiver successful detection can therefore be done without the use of the modulo operation and the scaling factor which makes the proposed vp scheme applicable to limited feedback scenarios analytical and simulation results show that the performance of the proposed scheme is free of the error floor typically encountered with conventional vp in the presence of limited feedback

exact sum rate analysis of mimo broadcast channels with random unitary beamforming random unitary beamforming rub is an attractive transmission scheme for mimo broadcast channels because of its ability to achieve high sum rate capacity with limited feedback in this letter we derive the exact analytical expressions for the ergodic sum rate of mimo broadcast channels with rub the analysis is facilitated by the development of the complete statistical characterization of ordered beam sinrs for a user which can find their application in many related problems

an extension of welch s approximate t solution to comparative bioequivalence trials summary we consider the problem of proving statistically the equivalence of two treatments with normally distributed observations the size and the power of the commonly used test procedures which assume equality of the variances are investigated when this assumption is violated on the one hand the preassigned level is considerably exceeded and on the other hand the power if no treatment difference exists drops heavily for differing sample sizes we propose an extension of welch s approximate t solution for the behrens fisher problem in bioequivalence assessment which is asymptotically optimal in a certain subclass of tests the behaviour of the proposed test is investigated in various finite sample situations the results show that the extension of welch s approximate t solution should be preferred for testing bioequivalence of two treatments whenever the population variances cannot be assumed equal and the sample sizes are different sometimes the experimenter knows which sample has the larger variance in this case the larger sample size should always be assigned to that group with the larger variance in order to optimize the actual level and power of the test

random coding lower bounds for the error exponent of joint quantization and watermarking systems we establish random coding lower bounds to the error exponent of discrete and gaussian joint quantization and private watermarking systems in the discrete system both the covertext and the attack channel are memoryless and have finite alphabets in the gaussian system the covertext is memoryless gaussian and the attack channel has additive memoryless gaussian noise in both cases our bounds on the error exponent are positive in the interior of the achievable quantization and watermarking rate region

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

some results in lumped mass finite element approximation of eigenvalue problems using numerical quadrature formulas in this paper we establish the convergence and the rate of convergence for approximate eigenvalues and eigenfunctions of second order elliptic eigenvalue problems obtained by a lumped mass finite element approximation various aspects of lumped mass techniques have been discussed for such eigenvalue problems by fix 1972 ishihara 1977 strang and fix 1973 and tong et al 1971 among others in our approach the lumping of the mass matrix results from the use of a lobatto quadrature formula for the integrals over rectangular lagrange finite elements of degree k

spectral element computation of high frequency leaky modes in three dimensional solid waveguides a numerical method is proposed to compute high frequency low leakage modes in structural waveguides surrounded by infinite solid media in order to model arbitrary shape structures a waveguide formulation is used which consists of applying to the elastodynamic equilibrium equations a space fourier transform along the waveguide axis and then a discretization method to the cross section coordinates however several numerical issues must be faced related to the unbounded nature of the cross section the number of degrees of freedom required to achieve an acceptable error in the high frequency regime as well as the number of modes to compute in this paper these issues are circumvented by applying perfectly matched layers pml along the cross section directions a high order spectral element method for the discretization of the cross section and an eigensolver shift suited for the computation of low leakage modes first computations are performed for an embedded cylindrical bar for which literature results are available the proposed pml waveguide formulation yields good agreement with literature results even in the case of weak impedance contrast its performance with high order spectral elements is assessed in terms of convergence and accuracy and compared to traditional low order finite elements then computations are performed for an embedded square bar dispersion curves exhibit strong similarities with cylinders these results show that the properties of low leakage modes observed in cylindrical bars can also occur in other types of geometry

a spectral element method for fluid dynamics laminar flow in a channel expansion a spectral element method that combines the generality of the finite element method with the accuracy of spectral techniques is proposed for the numerical solution of the incompressible navier stokes equations in the spectral element discretization the computational domain is broken into a series of elements and the velocity in each element is represented as a high order lagrangian interpolant through chebyshev collocation points the hyperbolic piece of the governing equations is then treated with an explicit collocation scheme while the pressure and viscous contributions are treated implicitly with a projection operator derived from a variational principle the implementation of the technique is demonstrated on a one dimensional inflow outflow advection diffusion equation and the method is then applied to laminar two dimensional separated flow in a channel expansion comparisons are made with experiment and previous numerical work

the computation of dispersion relations for three dimensional elastic waveguides using the scaled boundary finite element method abstract in this paper a numerical approach for the computation of dispersion relations for three dimensional waveguides with arbitrary cross section is proposed the formulation is based on the scaled boundary finite element method sbfem it is an extension of the approach previously derived for plate structures it is shown that the wavenumbers of guided waves in a waveguide can be obtained as the eigenvalues of the z matrix which is well known in the sbfem the hamiltonian properties of this matrix are utilized to derive an efficient way to compute the group velocities of propagating waves as eigenvalue derivatives the cross section of the waveguide is discretized using higher order spectral elements it is discussed in detail how symmetry axes can be utilized to reduce computational costs in order to sort the solutions at different frequencies a mode tracking algorithm is proposed based on the pade expansion

a 2 5d boundary element formulation for modeling damped waves in arbitrary cross section waveguides and cavities a regularized 2 5d boundary element method bem is proposed to predict the dispersion properties of damped stress guided waves in waveguides and cavities of arbitrary cross section the wave attenuation induced by material damping is introduced using linear viscoelastic constitutive relations and described in a spatial manner by the imaginary component of the axial wavenumber the discretized dispersive wave equation results in a nonlinear eigenvalue problem which is solved obtaining complex axial wavenumbers for a fixed frequency using a contour integral algorithm due to the singular characteristics and the multivalued feature of the wave equation the requirement of holomorphicity inside the contour region over the complex wavenumber plane is fulfilled by the introduction of the sommerfeld branch cuts and by the choice of the permissible riemann sheets a post processing analysis is developed for the extraction of the energy velocity of propagative guided waves the reliability of the method is demonstrated by comparing the results obtained for a rail and a bar with square cross section with those obtained from a 2 5d finite element formulation also known in literature as semi analytical finite element safe method next to show the potential of the proposed numerical framework dispersion properties are predicted for surface waves propagating along cylindrical cavities of arbitrary cross section it is demonstrated that the attenuation of surface waves approaches asymptotically the attenuation of rayleigh waves

the p and h p versions of the finite element method basic principles and properties in the classical form of the finite element method called the hversion piecewise polynomials of fixed degree p are used and the mesh size h is decreased for accuracy in this paper we discuss the fundamental theoretical ideas behind the relatively recent p version and h p version in the p version a fixed mesh is used and p is allowed to increase the h p version combines both approaches the authors describe and explain the basic properties and characteristics of these newer versions especially in areas where their behavior is significantly different from that of the h version simplified proofs of key concepts are included and computational illustrations of several results are provided a benchmark comparison between the various versions in included

causal state communication the problem of state communication over a discrete memoryless channel with discrete memoryless state is studied when the state information is available strictly causally at the encoder it is shown that block markov encoding in which the encoder communicates a description of the state sequence in the previous block by incorporating side information about the state sequence at the decoder yields the minimum state estimation error when the same channel is used to send additional independent information at the expense of a higher channel state estimation error the optimal tradeoff between the rate of the independent information and the state estimation error is characterized via the capacity distortion function it is shown that any optimal tradeoff pair can be achieved via rate splitting these coding theorems are then extended optimally to the case of causal channel state information at the encoder using the shannon strategy

digital image watermarking using balanced multiwavelets in this paper a robust watermarking algorithm using balanced multiwavelet transform is proposed the latter transform achieves simultaneous orthogonality and symmetry without requiring any input prefiltering therefore considerable reduction in computational complexity is possible making this transform a good candidate for real time watermarking implementations such as audio broadcast monitoring and dvd video watermarking the embedding scheme is image adaptive using a modified version of a well established perceptual model therefore the strength of the embedded watermark is controlled according to the local properties of the host image this has been achieved by the proposed perceptual model which is only dependent on the image activity and is not dependent on the multifilter sets used unlike those developed for scalar wavelets this adaptivity is a key factor for achieving the imperceptibility requirement often encountered in watermarking applications in addition the watermark embedding scheme is based on the principles of spread spectrum communications to achieve higher watermark robustness the optimal bounds for the embedding capacity are derived using a statistical model for balanced multiwavelet coefficients of the host image the statistical model is based on a generalized gaussian distribution limits of data hiding capacity clearly show that balanced multiwavelets provide higher watermarking rates this increase could also be exploited as a side channel for embedding watermark synchronization recovery data finally the analytical expressions are contrasted with experimental results where the robustness of the proposed watermarking system is evaluated against standard watermarking attacks

on distortion compensated dither modulation data hiding with repetition coding an exhaustive analysis of the distortion compensated dither modulation dc dm data hiding method with repetition coding is presented two decoding strategies maximum likelihood lattice decoding and euclidean distance decoding are discussed and some simplifications presented an exact performance analysis in terms of the bit error rate ber is given such an exact analysis is currently not available in the literature two methods for computing the exact ber and several approximations and bounds most of them in closed form are provided these approximations are employed to propose two novel improvements on the standard dc dm method with repetition the use of a weighted euclidean distance with optimizable weights and a vector form of the distortion compensation parameter both account for significant performance improvements dc dm is compared with quantization methods in the projected domain showing worse performance against additive noise attacks but higher robustness to cropping attacks a performance analysis of dc dm under coarse quantization that can be specialized to jpeg compression is also supplied all our results are validated with numerical simulations with both synthetic data and real images

achievable error exponents for the private fingerprinting game fingerprinting systems in the presence of collusive attacks are analyzed as a game between a fingerprinter and a decoder on the one hand and a coalition of two or more attackers on the other hand the fingerprinter distributes to different users different fingerprinted copies of a host data covertext drawn from a memoryless stationary source embedded with different fingerprints the coalition members create a forgery of the data while aiming at erasing the fingerprints in order not to be detected their action is modeled by a multiple access channel mac we analyze the performance of two classes of decoders associated with different kinds of error events the decoder of the first class aims at detecting the entire coalition whereas the second is satisfied with the detection of at least one member of the coalition both decoders have access to the original covertext data and observe the forgery in order to identify member s of the coalition motivated by a worst case approach we assume that the coalition of attackers is informed of the hiding strategy taken by the fingerprinter and the decoder while they are uninformed of the attacking scheme achievable single letter expressions for the two kinds of error exponents are obtained single letter lower bounds are also derived for the subclass of constant composition codes these lower and the upper bounds coincide for the error exponent of the first class further for the error of the first kind a decoder that is optimal is introduced and the worst case attack channel is characterized