integration of singular galerkin type boundary element integrals for 3d elasticity problems a galerkin approximation of both strongly and hypersingular boundary integral equation bie is considered for the solution of a mixed boundary value problem in 3d elasticity leading to a symmetric system of linear equations the evaluation of cauchy principal values v p and finite parts p f of double integrals is one of the most difficult parts within the implementation of such boundary element methods bems a new integration method which is strictly derived for the cases of coincident elements as well as edge adjacent and vertex adjacent elements leads to explicitly given regular integrand functions which can be integrated by the standard gauss legendre and gauss jacobi quadrature rules problems of a wide range of integral kernels on curved surfaces can be treated by this integration method we give estimates of the quadrature errors of the singular four dimensional integrals

a fast algorithm for computing distance spectrum of convolutional codes a fast algorithm for searching a tree fast is presented for computing the distance spectrum of convolutional codes the distance profile of a code is used to limit substantially the error patterns that have to be searched the algorithm can easily be modified to determine the number of nonzero information bits of an incorrect path as well as the length of an error event for testing systematic codes a faster version of the algorithm is given fast is much faster than the standard bidirectional search on a microvax d sub infinity 27 was verified for a rate r 1 2 memory m 25 code in 37 s of cpu time extensive tables of rate r 1 2 encoders are given several of the listed encoders have distance spectra superior to those of any previously known codes of the same rate and memory a conjecture than an r 1 2 systematic convolutional code of memory 2m will perform as well as a nonsystematic convolutional code of memory m is given strong support

total positivity and its applications preface i spline functions total positivity of the spline kernel and its applications b bojanov total positivity properties of lb splines t lyche l l schumaker total positivity and splines k morken totally positive systems and interpolation by subspaces of generalized splines m sommer h strauss ii matrix theory preservation of total nonnegativity under the hadamard product and related topics j garloff d g wagner vertex implications for totally nonnegative under the hadamard product and related topics j garloff on factorizations of totally positive matrices j garloff on factorizations of totally positive matrices m gasca j m pena iii geometric modeling total positivity and optimal bases j m carnicer j m pena total positivity and the shape of curves t n t goodman tchebycheff curves m l mazure h pottmann iv probability and mathematical biology analytical and probabilistic methods for totally positive matrices g s goodman some inequalities of total positivity in pure and applied mathematics s karlin z ziegler new directions and problems of multivariate total positivity motivated by genetic recombination probabilities s karlin v approximation theory tchebycheff spaces and total positivity j m carnicer j m pena cebysev and weak cebysev systems r a zalik vi complex analysis zero sets of entire fourier transforms of multiply positive density functions o m katkova vii statistics total nonnegativity of moment matrices and its application to e optimal designs in polynomial regression b heiligers analysis of regression dependence in 2 xn bivariate distributions and some applications in contingency tables s kasala m b rao viii real analysis total positivity and nonlinear analysis r q jia solutions of certain functional equations s karlin alternance and snakes in the nonlinear finite moment problem k tatalian ix combinatorics the applications of total positivity to combinatorics and conversely f brenti x integral equations spectral properties of totally positive kernels and matrices a pinkus index

a hierarchical approach to adaptive local refinement in isogeometric analysis abstract adaptive local refinement is one of the key issues in isogeometric analysis in this article we present an adaptive local refinement technique for isogeometric analysis based on extensions of hierarchical b splines we investigate the theoretical properties of the spline space to ensure fundamental properties like linear independence and partition of unity furthermore we use concepts well established in finite element analysis to fully integrate hierarchical spline spaces into the isogeometric setting this also allows us to access a posteriori error estimation techniques numerical results for several different examples are given and they turn out to be very promising

precoding for outage probability minimization on block fading channels the outage probability limit is a fundamental and achievable lower bound on the word error rate of coded communication systems affected by fading this limit is mainly determined by two parameters the diversity order and the coding gain with linear precoding full diversity on a block fading channel can be achieved without error correcting code however the effect of precoding on the coding gain is not well known mainly due to the complicated expression of the outage probability using a geometric approach this paper establishes simple upper bounds on the outage probability the minimization of which yields to precoding matrices that achieve very good performance for discrete alphabets it is shown that the combination of constellation expansion and precoding is sufficient to closely approach the minimum possible outage achieved by an i i d gaussian input distribution thus essentially maximizing the coding gain

gallager bounds for noncoherent decoders in fading channels recently gallager s bounding techniques have been used to derive tight performance bounds for coded systems in fading channels most works in this field have thus far dealt with coherent decoding this paper develops gallager bounds for noncoherent systems in fading channels unlike coherent decoding the exact error probability of a noncoherent decoder detector conditioned on the fading coefficients does not admit a closed form expression this difficulty is overcome in this paper by employing the chernoff technique although it weakens the bounds to some extent the chernoff technique enables the derivations of the limit before average lba bound and gallager bounds in closed form for noncoherent fading channels numerical examples show that the proposed bounds are convergent and are tighter than the conventional union bound

a new ber upper bound for multiuser downlink systems we consider improvement of bit error rate ber upper bounds based on the notion of decomposable error vectors devs introduced by s verdu for downlink multiuser space time systems over rayleigh fading channels although omission of devs and limiting before averaging lba technique are known to improve the standard union bound ub considerably it is mathematically intractable to obtain a bound in a closed form in this paper assuming maximum likelihood ml detection for downlink multiuser space time spreading sts systems we introduce a new modification of the decomposability of error vectors and propose a new ber upper bound we prove that the proposed bound is tighter than the standard union bound and the bound based on the overall decomposability the numerical results show that the proposed bound is also tighter than the bound based on positive sum decomposability psd in the scenario of downlink multiuser transmission

on the design and selection of convolutional codes for an uninterleaved bursty rician channel this article focuses on code design and code selection rules under power and decoding delay constraints for an antipodal bpsk modulated and convolutionally encoded communication system the system operates over a slowly fading awgn channel described by the block fading model we emphasize perfect coherent detection with maximum likelihood decoding assuming ideal channel information the instantaneous fading values the dominant design criterion in this scenario is the code diversity level in terms of blocks while the standard hamming distance plays a secondary role a code design procedure based on maximum distance separable mds cyclic block codes is presented along with a code search algorithm the performance results of selected codes are assessed via simulation and compared to those achieved by reed solomon codes with erasure and error decoding

low density graph codes for coded cooperation on slow fading relay channels we study low density parity check ldpc codes with iterative decoding on block fading bf relay channels we consider two users that employ coded cooperation a variant of decode and forward with a smaller outage probability than the latter an outage probability analysis for discrete constellations shows that full diversity can be achieved only when the coding rate does not exceed a maximum value that depends on the level of cooperation we derive a new code structure by extending the previously published full diversity root ldpc code designed for the bf point to point channel to exhibit a rate compatibility property which is necessary for coded cooperation we estimate the asymptotic performance through a new density evolution analysis and the word error rate performance is determined for finite length codes we show that our code construction exhibits near outage limit performance for all block lengths and for a range of coding rates up to 0 5 which is the highest possible coding rate for two cooperating users

a 3d isogeometric be fe analysis with dynamic remeshing for the simulation of a deformable particle in shear flows abstract a three dimensional isogeometric coupled boundary element and finite element approach based on analysis suitable t splines is developed for the simulation of deformable capsules suspended in shear flows boundary element analysis is used to solve the fluid stokes equation whereas the hydrodynamic membrane load is computed via isogeometric analysis under the assumption that the membrane is a hyper elastic thin shell with negligible bending resistance the smoothness of the t spline basis functions accommodate large deformations of the capsule without the need for additional smoothing techniques and can be used to accurately compute the membrane load a balanced distribution of membrane elements can be constructed using an unstructured locally refined mesh these properties are coupled with an adaptive temporal implicit integration scheme several benchmark examples are solved to illustrate the accuracy and potential of the method the approach is then applied to simulate the dynamics of a capsule in a real geometry of a brain capillary

edge coloring and stopping sets analysis in product codes with mds components we consider non binary product codes with mds components and their iterative row column algebraic decoding on the erasure channel both independent and block erasures are considered in this paper a compact graph representation is introduced on which we define double diversity edge colorings via the rootcheck concept an upper bound of the number of decoding iterations is given as a function of the graph size and the color palette size m then we propose a differential evolution edge coloring algorithm that produces colorings with a large population of minimal rootcheck order symbols the complexity of this algorithm per iteration is o m aleph for a given differential evolution parameter aleph where m aleph itself is small with respect to the huge cardinality of the coloring ensemble stopping sets of a product code are defined in the context of mds components and a relationship is established with the graph representation a full characterization of these stopping sets is given up to a size d 1 2 where d is the minimum hamming distance of the mds component code the performance of mds based product codes with and without double diversity coloring is analyzed in presence of both the block and the independent erasures in the latter case ml and iterative decoding are proven to coincide at small channel erasure probability furthermore numerical results show excellent performance in presence of unequal erasure probability due to double diversity colorings

coded modulation in the block fading channel coding theorems and code construction we consider coded modulation schemes for the block fading channel in the setting where a codeword spans a finite number n of fading degrees of freedom we show that coded modulations of rate r bit per complex dimension over a finite signal set spl chi spl sube spl copf of size 2 sup m achieve the optimal rate diversity tradeoff given by the singleton bound spl delta n m r 1 spl lfloor n 1 r m spl rfloor for r spl isin 0 m spl rfloor furthermore we show also that the popular bit interleaved coded modulation achieves the same optimal rate diversity tradeoff we present a novel coded modulation construction based on blockwise concatenation that systematically yields singleton bound achieving turbo like codes defined over an arbitrary signal set spl chi spl sub spl copf the proposed blockwise concatenation significantly outperforms conventional serial and parallel turbo codes in the block fading channel we analyze the ensemble average performance under maximum likelihood ml decoding of the proposed codes by means of upper bounds and tight approximations we show that differently from the additive white gaussian noise awgn and fully interleaved fading cases belief propagation iterative decoding performs very close to ml on the block fading channel for any signal to noise ratio snr and even for relatively short block lengths we also show that at constant decoding complexity per information bit the proposed codes perform close to the information outage probability for any block length while standard block codes e g obtained by trellis termination of convolutional codes have a gap from outage that increases with the block length this is a different and more subtle manifestation of the so called interleaving gain of turbo codes

generalized union bound for space time codes gallager s second bounding technique also known as the generalized union bound is employed to derive a new upper bound on the error probability of space time codes stcs with maximum likelihood ml decoding on quasi static rayleigh fading channels the new bound is distinguished by two characteristics unlike the classical union bound the new bound is rapidly convergent and is only a few decibels away from simulation results and compared with gallager s first bound it has better computational efficiency and numerical stability hence the new bound is a useful tool for performance analysis and computer search of good stcs moreover the correlation between fading coefficients is easily accommodated by the new bound the application of the new bound to convolutional coding on block fading channels is also demonstrated and an improved version is derived for the bit error probability of maximum a posteriori probability decoding

distance spectra and performance bounds of space time trellis codes over quasistatic fading channels this correspondence presents a general approach to upper bounding coded system performance over quasistatic fading channels qsfc this approach has the advantage of yielding a closed form upper bound that converge for all signal to noise ratios snrs the proposed approach is used to upper bound the performance of space time trellis codes sttc over qsfcs the resulting upper bounds for sttcs are better adapted to the qsfc and present an improvement over worst case pairwise error probability pep analysis used so far in its second part this correspondence investigates several ways to reduce the complexity of computing the distance spectrum of sttcs the combined result obtained from using the new upper bounds and the computed distance spectra are shown to be close to simulated performance for all snrs

some spectral approximations of two dimensional fourth order problems this paper deals with the approximation of the biharmonic equation in a square domain with dirichlet boundary conditions two types of discrete problems are presented the numerical analysis is performed and estimates for the error between the exact and approximate solutions are given

constructing totally positive piecewise chebyshevian b spline bases abstract we consider piecewise chebyshevian splines in the sense of splines with pieces taken from any different five dimensional extended chebyshev spaces and with connection matrices at the knots in this large context we establish necessary and sufficient conditions for the existence of totally positive refinable b spline bases these conditions are applied in many important special cases e g symmetric cardinal geometrically continuous quartic b spline parametrically continuous mixed l splines the great variety of illustrations provided proves the richness of this class of splines for design this richness can be exploited in various other fields as well

isogemetric analysis and symmetric galerkin bem isogeometric approach applied to boundary element methods is an emerging research area see e g simpson et al 2012 33 in this context the aim of the present contribution is that of investigating from a numerical point of view the symmetric galerkin boundary element method sgbem devoted to the solution of 2d boundary value problems for the laplace equation where the boundary and the unknowns on it are both represented by b splines de boor 2001 9 we mainly compare this approach which we call iga sgbem with a curvilinear sgbem aimi et al 1999 2 which operates on any boundary given by explicit parametric representation and where the approximate solution is obtained using lagrangian basis both techniques are further compared with a standard conventional sgbem approach aimi et al 1997 1 where the boundary of the assigned problem is approximated by linear elements and the numerical solution is expressed in terms of lagrangian basis several examples will be presented and discussed underlying benefits and drawbacks of all the above mentioned approaches

symmetric galerkin boundary formulations employing curved elements accounts of the symmetric galerkin approach to boundary element analysis bea have recently been published this paper attempts to add to the understanding of this method by addressing a series of fundamental issues associated with its potential computational efficiency a new symmetric galerkin theoretical formulation for both the harmonic heat conduction and the biharmonic elasticity problem that employs regularized singular and hypersingular boundary integral equations bies is presented the novel use of regularized bies in the galerkin context is shown to allow straightforward incorporation of curved isoparametric elements a symmetric reusable intrinsic sample point risp numerical integration algorithm is shown to produce a galerkin i e double integration strategy that is competitive with its counterpart i e singular integration procedure in the collocation bea approach when the time saved in the symmetric equation solution phase is also taken into account this new formulation is shown to be capable of employing hypersingular bies while obviating the requirement of c 1 continuity a fact that allows the employment of the popular continuous element technology the behavior of the symmetric galerkin bea method with regard to both direct and iterative equation solution operations is also addressed a series of example problems are presented to quantify the performance of this symmetric approach relative to the more conventional unsymmetric bea in terms of both accuracy and efficiency it is concluded that appropriate implementations of the symmetric galerkin approach to bea indeed have the potential to be competitive with if not superior to collocation based bea for large scale problems

on low complexity space time coding for quasi static channels we propose a new space time coding scheme for the quasi static multiple antenna channel with perfect channel state information at the receiver and no channel state information at the transmitter in our scheme codewords produced by a trellis encoder are formatted into space time codeword arrays such that decoding can be implemented efficiently by minimum mean square error mmse decision feedback interference mitigation coupled with viterbi decoding through the use of per survivor processing we discuss the code design for the new scheme and show that finding codes with optimal diversity is much easier than for conventional trellis space time codes stcs we provide an upper bound on the word error rate wer of our scheme which is both accurate and easy to evaluate then we find upper and lower bounds on the information outage probability with discrete independent and identically distributed i i d inputs as opposed to gaussian inputs as in most previous works and we show that the mmse front end yields a large advantage over the whitened matched filter i e zero forcing front end finally we provide a comprehensive performance complexity comparison of our scheme with coded vertical bell labs layered space time v blast architecture and with the recently proposed threaded space time codes we also discuss the concatenation of our scheme with block space time precoders such as the linear dispersion codes

diversity analysis of bit interleaved coded multiple beamforming in this paper diversity analysis of bit interleaved coded multiple beamforming bicmb is extended to the case of general spatial interleavers removing a condition on their previously known design criteria we provide a method to get diversity order simplifying the calculation of pairwise error probability pep by using the singleton bound we also show the maximum achievable diversity for given code rate and the number of subchannels

on the performance analysis of space time codes in quasi static rayleigh fading channels in this paper we analyze the performance of space time codes by deriving a new approximation of the frame error probabilities for space time trellis coded modulations over quasi static rayleigh fading channels we take advantage of two techniques the modified bounding technique and the limiting before averaging technique to tighten the upper bound in addition we establish a theorem that enables us to reduce the computation and memory needed to calculate the frame error rate fer approximation the newly derived approximation is very tight requires only the distance spectrum of the space time code and can be computed through single numerical integration numerical results exhibit that the new approximation is much closer to the simulation results than other existing bounds are especially in the case of one receive antenna

performance of viterbi decoding with and without arq on rician fading channels in this paper we investigate the performance of the viterbi decoding algorithm with without automatic repeat request arq over a rician flat fading channel with unlimited interleaving we show that the decay rate of the average bit error probability with respect to the bit energy to noise ratio is at least equal to d f at high bit energy to noise ratio for both cases with arq and without arq where d f is the free distance of the convolutional code the yamamoto itoh flag helps to reduce the average bit error probability by a factor of 4 d f with a negligible retransmission rate we also prove an interesting result that the average bit error probability decays exponentially fast with respect to the rician factor for any fixed bit energy per noise ratio in addition the average bit error exponent with respect to the rician factor is shown to be d f

performance of space time codes gallager bounds and weight enumeration since the standard union bound for space time codes may diverge in quasi static fading channels the limit before average lba technique has been exploited to derive tight performance bounds however it suffers from the computational burden arising from a multidimensional integral in this paper efficient bounding techniques for space time codes are developed in the framework of gallager bounds two closed form upper bounds the ellipsoidal bound and the spherical bound are proposed that come close to simulation results within a few tenths of a decibel in addition two novel methods of weight enumeration operating on a further reduced state diagram are presented which in conjunction with the bounding techniques give a thorough treatment of performance bounds for space time codes

space time coded systems using continuous phase modulation we develop space time trellis coded stc schemes using continuous phase modulation cpm we employ the rimoldi model of cpm to create a decomposed model of stc cpm the decomposition separates the coding from the modulation the space time encoding and the inherent cpm encoding is combined into a single trellis encoder on the ring of integers modulo this is followed by a bank of memoryless modulators the model allows the search for good space time codes to take into account the inherent encoding of the modulation

new gallager bounds in block fading channels in this paper we propose a new upper bound on the error performance of binary linear codes over block fading channels by employing gallager s first and second bounding techniques as the proposed bound is numerically intensive in its general form we consider two special cases namely the spherical bound and the ds2 exponential bound which are found to be tight in nonergodic and near ergodic block fading channels respectively the tightness of the proposed bounds is demonstrated for turbo codes many existing bounds for quasistatic or fully interleaved fading channels can be viewed as special cases of the proposed gallager bound

trellis codes for periodic erasures this paper describes techniques for the design and analysis of trellis codes that provide reliable communication over every channel in a specified set of possible channels where each channel is characterized by additive white gaussian noise with a distinct periodic variation in signal to noise ratio an important practical application for such trellis codes is the periodic erasure channel produced by partial band interference dispersed by a block interleaver we present trellis codes that provide reliable communication over all periodic erasure patterns of a given period for which the number of unerased coded bits per period is at least equal to the number of information bits per period

a galerkin symmetric boundary element method in elasticity formulation and implementation a symmetric boundary element method based on a weighted residual galerkin approach for elastoplastic analysis is revisited and its computer implementation for two dimensional homogeneous problems is described

b spline linear multistep methods and their continuous extensions in this paper starting from a sequence of results which can be traced back to i j schoenberg we analyze a class of spline collocation methods for the numerical solution of ordinary differential equations odes with collocation points coinciding with the knots such collocation methods are naturally associated to a special class of linear multistep methods here called b spline bs methods which are able to generate the spline values at the knots we prove that provided the additional conditions are appropriately chosen such methods are all convergent and a stable the convergence property of the bs methods is naturally inherited by the related spline extensions which by the way are easily and safely computable using their b spline representation

a two dimensional isogeometric boundary element method for elastostatic analysis the concept of isogeometric analysis where functions that are used to describe geometry in cad software are used to approximate the unknown fields in numerical simulations has received great attention in recent years the method has the potential to have profound impact on engineering design since the task of meshing which in some cases can add significant overhead has been circumvented much of the research effort has been focused on finite element implementations of the isogeometric concept but at present little has been seen on the application to the boundary element method the current paper proposes an isogeometric boundary element method bem which we term igabem applied to two dimensional elastostatic problems using non uniform rational b splines nurbs we find it is a natural fit with the isogeometric concept since both the nurbs approximation and bem deal with quantities entirely on the boundary the method is verified against analytical solutions where it is seen that superior accuracies are achieved over a conventional quadratic isoparametric bem implementation

generalized b splines as a tool in isogeometric analysis the concept of isogeometric analysis has been proposed in 13 where nurbs are considered as basis of the analysis thanks to their ability to construct an exact geometric model in several practical applications and to their popularity in commercial cad systems in this paper we propose an alternative to the rational model presenting an isogeometric analysis approach based on generalized b splines geometric models exactly represented by generalized b splines include those generated by nurbs moreover generalized b splines possess all fundamental properties of algebraic b splines and nurbs including classical refinement processes as h p k refinements finally since generalized b splines are not confined to rational functions they behave completely similar to algebraic b splines with respect to differentiation and integration this seems to be of interest in the treatment of some relevant problems

isogeometric symmetric galerkin boundary element method for three dimensional elasticity problems abstract the isogeometric analysis iga is applied for the weakly singular symmetric galerkin boundary element method sgbem to analyzelinear elastostatics problems in three dimensional domains the background of the proposed method is to use non uniform rational b splines nurbs as the basis functions for the approximation of both geometry and field variables i e displacement and traction of the governing integral equations same as weakly singular sgbem the basic ingredient of the method is a pair of weakly singular weak form integral equations for the displacement and traction on the boundary of the domain these integral equations are solved approximately using standard galerkin approximation in addition to the advantages that iga owned the proposed method exploits the common boundary representation of cad model and boundary element method various numerical examples of both simple and complex geometries are examined to validate the accuracy and efficiency of the proposed method through the numerical examples it is observed that the iga sgbem produces highly accurate results

distance spectrum analysis of space time trellis coded modulations in quasi static rayleigh fading channels in this correspondence we propose an algorithm for computing the distance spectrum of a space time trellis code achieving maximal diversity gain in quasi static fading channels we further present a state reduction technique for trellis codes that can reduce the complexity of the distance spectrum computation we provide numerical results supporting the empirical evidence that a truncated union bound obtained from the distance spectrum provides an accurate characterization of the relative performance ordering of different space time trellis codes and therefore it offers a tool for better space time trellis code design

tight analytical and asymptotic upper bound for the ber and fer of linear codes over exponentially correlated generalized fading channels in this paper the upper bound and asymptotical approximation for the bit error rate ber as well as for the frame error rate of linear block codes under maximum likelihood decoding operating over exponentially correlated ec generalized fading channels are proposed particularly our analysis takes the convolutional codes as an example and three different fading scenarios are considered namely rice nakagami m and weibull fading such scenarios have a common property that is spherically invariant random process sirp our analysis relies on the derivation of new lower bounds per each eigenvalue since the ber as well as the fer expressions are written in terms of the pairwise error probability which by its turn depends on the eigenvalues of the channel covariance matrix based on that the upper bounds and asymptotic expressions of the considered metrics subject to the three above fading models are derived which show to be tighter than the previous results published elsewhere in the literature especially for the high signal to noise ratio regions

coding in the block erasure channel in this correspondence we study an m ary block erasure channel with b blocks where with probability epsi a block of l coded symbols is erased the behavior of the error probability of coded systems over such channels is studied and we show that if the code is diversity wise maximum distance separable its word error probability is equal to the outage probability which admits a very simple expression this correspondence is intended to complement the error probability analysis in previous work by lapidoth and shed some light on the design of coding schemes for nonergodic channels

on performance bounds for space time codes on fading channels we evaluate truncated union bounds on the frame error rate fer performance of space time st codes operating over the quasi static fading channel and compare them with computer simulation results we consider both st trellis and block codes we make the following contributions for the case of st trellis codes we develop a general method which we denote as measure spectrum analysis that characterizes st codeword differences and accommodates the combined influences of the st code and channel scenario we propose a numerical bounding method that converges in the measure spectrum to within a very small fraction of a decibel to the simulated fer over the full range of signal to noise ratio in addition we demonstrate the existence of dominant quasi static fading error events and detail a method for predicting them using only this set of dominant measure spectrum elements very rapid and tight numerical estimation of fer performance is attained

multifrequency trellis coding with low delay for fading channels an l frequency trellis coding scheme designed for fading channels that provides diversity up to order l is described l frequency coding is advantageous over channel coding schemes that achieve implicit time diversity through trellis coding in conjunction with time interleaving because it requires negligible end to end delay the authors derive an upper bound for the probability of symbol error of the l frequency code based on this upper bound they then deduce the design criteria for optimum l frequency codes a numerical approximation to this upper bound and the design of a two state and two four state two frequency codes are presented through simulations it was found that relative to the traditional dual frequency diversity approach the two state and four state codes achieve 3 and 4 db coding gains respectively this energy efficiency gain can be translated into a spectral efficiency gain a brief discussion on the difference in code design techniques for the gaussian channel and the fading channel is also presented

universal trellis codes for diagonally layered space time systems foschini s diagonally layered space time transmission system known as d blast is an architecture designed for a rayleigh fading environment using multiple element antenna arrays at both the transmit and receive sites to achieve very high spectral efficiencies in this paper we propose a simple coding technique for d blast that uses a single trellis code with finite traceback viterbi decoding we examine the performance of universal trellis codes that are designed to have a distance structure that is matched to the periodic signal to noise ratio snr variation of the channel created by d blast under the assumption that the channel is static during one burst but may change from burst to burst we show that a universal 64 state trellis code on a 2 spl times 2 d blast system with long enough block lengths displays universal behavior working on almost every 2 spl times 2 channel with at least the mutual information required by a standard 64 state awgn trellis code the only 2 spl times 2 channel where more mutual information is required is a certain rotation of the zero eigenvalue channel we also present 4 spl times 4 and 8 spl times 8 examples

evaluating the performance of convolutional codes over block fading channels this correspondence considers union upper bound techniques for error control codes with limited interleaving over block fading rician channels a modified bounding technique is presented that relies on limiting the conditional union bound before averaging over the fading process this technique although analytically not very attractive provides tight and hence useful numerical results

some new twists to problems involving the gaussian probability integral using an alternate form of the gaussian probability integral discovered a number of years ago it is shown that the solution to a number of previously considered communication problems can be simplified and in some cases made more accurate i e exact rather than bounded these problems include the evaluation of 1 the bit error probability of uncoded phase shift keying psk with costas loop tracking 2 word error probability of antipodal modulation in the presence of fading 3 bit error probability of coded m ary psk mpsk over the memoryless fading channel with given channel state information 4 conditional symbol error probability of mpsk in the presence of carrier synchronization error and 5 the average error probability for the binary additive white gaussian noise awgn intersymbol interference channel also obtained is a generalization of this new alternate form to the case of a two dimensional gaussian probability integral with arbitrary correlation which can be used to evaluate the symbol error probability of mpsk with i q unbalance

low density parity check codes for nonergodic block fading channels we design powerful low density parity check ldpc codes with iterative decoding for the block fading channel we first study the case of maximum likelihood decoding and show that the design criterion is rather straightforward since optimal constructions for maximum likelihood decoding do not perform well under iterative decoding we introduce a new family of full diversity ldpc codes that exhibit near outage limit performance under iterative decoding for all block lengths this family competes favorably with multiplexed parallel turbo codes for nonergodic channels

hypersingular kernel integration in 3d galerkin boundary element method we consider cauchy singular and hypersingular boundary integral equations associated with 3d potential problems defined on polygonal domains whose solutions are approximated with a galerkin boundary element method related to a given triangulation of the boundary in particular for constant and linear shape functions the most frequently used basis functions we give explicit results of the analytical inner integrations and suggest suitable quadrature schemes to evaluate the outer integrals required to form the galerkin matrix elements these numerical indications are given after an analysis of the singularities arising in the whole integration process which is valid also for shape functions of higher degrees

on the convergence of the p version of the boundary element galerkin method abstract the authors consider various physical problems which may be formulated in terms of integral equations of the first kind including the two dimensional screen neumann and dirichlet problems in acoustics and crack problems in elasticity sharp regularity results for the solutions are available for these problems proven is the convergence of the p version for some galerkin boundary element schemes based on the integral equation formulations it is shown that the rate of convergence obtained by our method is twice that for the usual h version

error probability bounds for bit interleaved space time trellis coding over block fading channels in this correspondence we investigate the error probability bounds of a bit interleaved space time trellis coding bisttc scheme which concatenates bit interleaved coded modulation bicm with a space time trellis code sttc we focus on general block fading channels wherein each data packet or frame spans a number of independent fading blocks bicm applied to such channel environments can effectively exploit both time and frequency selectivity while a sttc maximizes the spacial diversity order the exact pairwise error probability pep and weight enumeration function wef of bisttc are used to evaluate the error bound due to the concatenation of an outer error correction code ecc and a sttc the overall wef of bisttc is obtained by combining the wef of the outer code with that of the sttc through an uniform interleaver the main challenge here is to compute the wef of a sttc for block fading channels with reasonable complexity we rely on constructing a composite state transition matrix based on a number of single step virtual trellises each corresponding to an independent fading block within a frame we discuss how this approach reduces storage and computational requirements in the bound analysis compared to the existing method of obtaining the state transition matrix through accumulation of single step transition matrices the derived bound is applicable to both spatially uncorrelated and correlated channels as well as to both flat and frequency selective block fading channels the bound is shown to provide a reasonably close estimate of the simulated performance based on the turbo equalizer like iterative processing of soft information between the sttc decoder and the ecc decoder

pragmatic space time trellis codes gtf based design for block fading channels the pragmatic approach for the construction of space time codes over block fading channels leads to low complexity encoders decoders making them suitable for various applications including cooperative communications we propose a design methodology for pragmatic space time codes which is based on an extension of the concept of generalized transfer function our search algorithm provides code generators for arbitrary number of states antennas and fading rates numerical results show that the performance of the pragmatic space time codes obtained by our design methodology is generally better than that of previously known space time trellis codes in block fading channels

numerical integration schemes for the bem solution of hypersingular integral equations in this paper we consider singular and hypersingular integral equations associated with 2d boundary value problems defined on domains whose boundaries have piecewise smooth parametric representations in particular given any polynomial local basis we show how to compute efficiently all integrals required by the galerkin method the proposed numerical schemes require the user to specify only the local polynomial degrees therefore they are quite suitable for the construction of p and h p versions of galerkin bem copyright 1999 john wiley sons ltd

coded diversity on block fading channels this paper considers coded diversity schemes over block fading rician channels using random coding techniques two random coding upper bounds on the error probability of block codes are derived a new bound and a simpler but looser bound assuming binary input distribution also a new lower bound for any block code is derived using the strong converse to channel coding theorem the lower bound shows that the new random coding upper bound is quite tight furthermore it is shown that the maximum achievable diversity order in a block fading channel with finite interleaving depends not only on the number of subchannels l but also on the code rate r and that the performance can only marginally be improved by increasing the block length of the code the random coding upper bound and the lower bound are shown to converge to the capacity outage for large channel block lengths n demonstrating that the capacity outage can be used for estimating the error probability of coded diversity schemes

isogeometric analysis with powell sabin splines for advection diffusion reaction problems abstract this paper presents the use of powell sabin splines in the context of isogeometric analysis for the numerical solution of advection diffusion reaction equations powell sabin splines are piecewise quadratic c 1 functions defined on a given triangulation with a particular macro structure we discuss the galerkin discretization based on a normalized powell sabin b spline basis we focus on the accurate detection of internal and boundary layers and on local refinements we apply the approach to several test problems and we illustrate its effectiveness by a comparison with classical finite element and recent isogeometric analysis procedures

further results on convolutional code search for block fading channels this correspondence presents results of code search for convolutional codes over block fading channels bfcs search criteria are based on a union bound approach which exploits the concept of generalized transfer function gtf of the error trellis diagram a new asymptotic bound is derived and the performance of the codes found using our search criterion is compared analytically and by numerical simulation with already existing codes