bandpass correlator analysis for general input assumptions corresp for general assumptions concerning bandpass signal and noise inputs previous analyses of analog cross correlators have yielded very complicated expressions for the probability density function pdf of the correlator output the inherent computational difficulties therefore limited the application of these pdf s almost exclusively to special cases of equal noise powers and noise spectrums symmetric about the signal s frequency in this correspondence it is shown that for general bandpass inputs the correlator output can always be expressed as the difference of two scaled independent noncentral chi squared variables if a certain matrix transformation of variables is employed the characteristic function method is then used to derive the pdf which is as readily computed as for the case of special assumptions

downlink throughput maximization for ofdma systems with feedback channel capacity constraints in this correspondence we study the downlink throughput maximization for orthogonal frequency division multiple access ofdma systems in the presence of feedback channel capacity constraints we establish an information theoretic lower bound on the capacity of feedback channel and build the corresponding test channel that achieves this lower bound based on the derived test channel we formulate two optimization problems that maximize the downlink throughput with quantized channel state information csi i one problem where throughput is defined with the ergodic throughput and ii the other problem with the outage throughput from which we can see the performance limit for given limit feedback channels we solve the throughput maximization problem through an iterative approach which achieves the optimal ergodic throughput and the near optimal outage throughput numerical results show that the downlink throughput with a limited feedback of csi can be close to that with perfect csi by exploiting correlation properties of downlink csi for quantization

optimal least squares approximations to the transient behavior of the stable m m 1 queue we present simple exponential approximations to the transient behavior of the stable m m 1 queue the approximations are optimal in a least squares sense and we find them to agree well with exact results our approach can be used to derive approximations for any time dependent quantity with a known laplace transform e g the probability distribution and the moments of the queue size of the waiting time etc it is the only approach we are aware of in which the error between approximations and exact results can be explicitly computed

new representations and bounds for the generalized marcum q function via a geometric approach and an application the generalized marcum q function of order m qm a b is interpreted geometrically as the probability of a 2m dimensional real gaussian random vector z2m whose mean vector has a frobenius norm of a lying outside of a hyperball bo b 2m of 2m dimensions with radius b and centered at the origin o based on this new geometric view some new representations and closed form bounds are derived for qm a b for the case that m is an odd multiple of 0 5 a new closed form representation is derived which involves only simple exponential and erfc functions for the case that m is an integer a pair of new finite integral representations for qm a b is derived some generic exponential bounds and erfc bounds are also derived by computing the probability of z2m lying outside of various bounding geometrical shapes whose surfaces tightly enclose or are tightly enclosed by the surface of bo b 2m these bounding shapes consist of an arbitrarily large number of parts as their closeness of fit with bo b 2m improves our generic bounds approach the exact value of qm a b the function qm a b is proved to be an increasing function of its order when 2m is a positive integer thus qm 0 5 a b and qm 0 5 a b can be used as tight upper and lower bounds respectively on qm a b their average is a good approximation to qm a b an application of our new representations and bounds is also given

on the stabilization of finite volume methods with co located variables for incompressible flow finite volume methods with co located variables for incompressible flow suffer from spurious pressure oscillations unless a stabilization method is applied variations of the pressure weighed interpolation pwi method are typically used for this purpose but the pwi method does not only prevent spurious oscillations counter intuitively it also simplifies the approximation of the schur complement pressure matrix which appears in iterative solution methods such as simple

numerical study of the turbulent flow past an airfoil with trailing edge separation presentation d une methode numerique par volume fini pour la resolution des equations de navier stokes bidimensionnelles incompressibles et stationnaires en coordonnees generales curvilignes application de la methode aux ecoulements turbulents sur des profils avec et sans separation au bord de sortie posterieur comparaison des calculs avec des donnees experimentales

a new higher order finite volume method based on moving least squares for the resolution of the incompressible navier stokes equations on unstructured grids in this work a new higher order 2 accurate finite volume method for the resolution of the incompressible navier stokes equations on unstructured grids is presented the formulation is based on the use of moving least squares mls approximants third and fourth order accurate discretizations of the convective and viscous fluxes are obtained on collocated meshes in addition mls is employed to design a new momentum interpolation method that allows interpolations better than linear on any kind of mesh the accuracy and performance of the proposed method is demonstrated by solving different steady and unsteady benchmark problems on unstructured grids

new upper bounds on error exponents we derive new upper bounds on the error exponents for the maximum likelihood decoding and error detecting in the binary symmetric channels this is an improvement on the best earlier known bounds by shannon gallager berlekamp 1967 and mceliece omura 1977 for the probability of undetected error the new bounds are better than the bounds by levenshtein 1978 1989 and the bound by abdel ghaffar see ibid vol 43 p 1489 502 1997 moreover we further extend the range of rates where the undetected error exponent is known to be exact the new bounds are based on an analysis of possible distance distributions of the codes along with some inequalities relating the distance distributions to the error probabilities

m m 1 transient state occupancy probabilities via the discrete fourier transform a procedure is given for the computation of the transient state occupancy probabilities of the m m 1 queue the method makes use of the inverse discrete fourier transform computed by means of the fast fourier transform it avoids the direct evaluation of modified bessel functions and sidesteps difficulties due to the computation of very large and very small intermediate quantities

pressure based calculation procedure for viscous flows at all speeds in arbitrary configurations a calculation procedure for viscous flows at all mach numbers has been described the scheme has been developed for a nonorthogonal coordinate system in order to handle both incompressible and compressible flows pressure has been selected as a primary dependent variable in preference to density the pressure field is evaluated using the compressible form of the simpler algorithm the accuracy of the proposed scheme has been assessed by comparing the results with experimental data or other numerical results available in the literature

transient m m 1 queue variance computation using generalized q functions a generalized q function representation for the transient m m 1 queue variance is developed the expression is highly accurate and computationally efficient and an upper bound on the error is easily calculated for a q function relative error of 2 10 sup 12 using parl s method the relative error of the variance is generally less than 10 sup 9 average execution time is of the order of 70 ms per point on a vax 11 750 but faster execution times can be obtained by using larger q function relative errors

maximum likelihood detection for differential unitary space time modulation with carrier frequency offset can conventional differential unitary space time modulation dustm be applied when there is an unknown carrier frequency offset cfo this paper answers this question affirmatively and derives the necessary maximum likelihood ml detection rule the asymptotic performance of the proposed ml rule is analyzed leading to a code design criterion for dustm by using the modified diversity product the resulting proposed decision rule is a new differential modulation scheme in both the temporal and spatial domains two sub optimal multiple symbol decision rules with improved performance are also proposed for the efficient implementation of these we derive a modified bound intersection detector bid a generalization of the previously derived optimal bid for the conventional dustm the simulation results show that the proposed differential modulation scheme is more robust against cfo drifting than the existing double temporal differential modulation

an empirical investigation of the transient behavior of stationary queueing systems this paper examines the transient behavior of infinite capacity single server markovian queueing systems it estimates q t the expected number of customers in queue at time t by numerically solving the sets of simultaneous first order differential equations that describe these systems empirical results have been drawn from these observations for small values of t the behavior of q t is strongly influenced by the initial state of the queueing system for systems with deterministic initial conditions one can roughly predict which of a small set of patterns this behavior will follow after an initial period of time and independently of initial conditions q t approaches q in a manner that can be approximated through a decaying exponential function on the basis of experimental evidence we have developed an expression that provides a good approximation to the observed values of the time constant associated with this exponential function this expression can also be used to determine an upper b

on the calculation of the generalized q function via parl s method corresp parl has previously given error bounds suitable for calculating marcum s q function however it is shown that additional terms in the error bound are necessary for accurate calculations of the generalized q function q m alpha beta the values of m alpha and beta that result in successful algorithm completion are examined numerical results are presented for calculations of the noncentral chi square distribution and the probability of detection for a classical multiobservation detection problem

computation of the transient m m 1 queue cdf pdf and mean with generalized q functions generalized q function expressions are developed for the transient state occupancy cumulative distribution function cdf probability density function pdf and expected value for an m m 1 queue the pdf equation is an extension of a previous result when parl s method is used to calculate the generalized q function the equations are computationally efficient and accurate for a q function relative error of 2 cdot10 12 the relative error of the result is typically 10 10or better relative error will increase however for cdf and pdf values on the order of the q function relative error execution time per point on a vax 11 750 is on the order of tens of milliseconds for the range of parameters considered

throughput optimal precoding and rate allocation for miso systems with noisy feedback channels a throughput metric is considered for a multiple input single output miso system with noisy feedback of channel state information csi the goal is to optimize a precoding matrix with a medium access control layer metric the problem is a nonlinear multidimensional optimization results show that the optimal precoding turns into beamforming when the signal to noise ratio snr of csi feedback is sufficiently large a necessary condition for the optimality of beamforming under the throughput metric is determined and the necessary and sufficient condition is numerically found based on the gauss chebyshev quadrature method next the rate allocation for beamforming and spatial diversity is analyzed then a two mode transmission scheme is proposed such that the transmitter is engaged in either the beamforming mode or the spatial diversity mode depending on the snr of the csi feedback it is shown that at a fairly high snr of csi feedback the rate allocation needs to be reduced while at a low snr of csi feedback the allocated rate should be increased it is shown that when the snr of csi feedback is lower than a threshold there always exists an snr of the transmitted signal such that the csi feedback can be viewed as the real csi solely for the purpose of rate allocation the result also shows that the throughput of two mode transmission is almost the same as the throughput of the optimal precoding scheme even with a low snr and large feedback delay

on the finite volume discretization of discontinuous body force field on collocated grid application to vof method discontinuities in the body force field typically appear at the interface of two fluid systems modeled with the volume of fluid vof and discretized with the finite volume method the discontinuous body force fields are represented as abruptly variable in the present study gravity and continuum surface force csf are considered such strongly variable body forces can produce unphysical spikes in the velocity field when collocated variable arrangement is used the spikes can be eliminated following a force field discretization rule which is deduced by imposing a constraint requiring a zero velocity solution when the forces applied to the system are equilibrated with the gradient of the pressure field it is shown as a byproduct of the present work that a zero velocity solution can only be obtained if the force field is conservative on the discrete level which applies also for the studied case of a stationary bubble finally the case of a rising bubble demonstrates that the proposed rule should be obeyed generally although it is obtained for a quiescent fluid

unified formulation of the momentum weighted interpolation for collocated variable arrangements abstract momentum weighted interpolation mwi is a widely used discretisation method to prevent pressure velocity decoupling in simulations of incompressible and low mach number flows on meshes with a collocated variable arrangement despite its popularity a unified and consistent formulation of the mwi is not available at present in this work a discretisation procedure is devised following an in depth analysis of the individual terms of the mwi derived from physically consistent arguments based on which a unified formulation of the mwi for flows on structured and unstructured meshes is proposed including extensions for discontinuous source terms in the momentum equations as well as discontinuous changes of density as shown by the presented analysis and numerical results the mwi enforces a low pass filter on the pressure field which suppresses oscillatory solutions furthermore the numerical dissipation of kinetic energy introduced by the mwi is shown to converge with third order in space and is independent of the time step if the mwi is derived consistently from the momentum equations in the presence of source terms the low pass filter on the pressure field can be shaped by a careful choice of the interpolation coefficients to ensure the filter only acts on the driving pressure gradient that is associated with the fluid motion which is shown to be vitally important for the accuracy of the numerical solution to this end a force balanced discretisation of the source terms is proposed that precisely matches the discretisation of the pressure gradients and preserves the force applied to the flow using representative test cases of incompressible and low mach number flows including flows with discontinuous source terms and two phase flows with large density ratios the newly proposed formulation of the mwi is favourably compared against existing formulations and is shown to significantly reduce or even eliminate solution errors with an increased stability for flows with large density ratios

approximate expressions for the output signal to noise ratios for two types of cross correlators with correlated bandpass inputs thus far analytical expressions have not been developed for the output signal to noise ratio of a polarity coincidence correlator when the noise is correlated between the input channels approximate expressions are developed here for the output signal to noise ratios for two types of cross correlator systems one being the polarity coincidence correlator with a hard limiter in each input channel and the other variation of this correlator having a hard limiter in only one input channel the approximation scheme is based upon the known output signal to noise characteristics of a limiter and that of the standard analog correlator with no limiters the derived expressions are applicable for the case of deterministic sine waves plus narrow band gaussian noise in each input channel where the noise between channels may be correlated for the case of uncorrelated noise between input channels good agreement is found between the approximate formulas and known exact results finally asymptotic expressions are developed for certain limiting cases of input signal to noise ratios having extreme values in one or both input channels

note on the calculation of the probability of detection and the generalized marcum q function a highly reliable accurate and efficient method of calculating the probability of detection p sub n x y for n incoherently integrated samples where x is the constant received signal to noise ratio of a single pulse and y is the normalized threshold level is presented the useful range of parameters easily exceeds most needs on a vax 11 computer with double precision calculations better than 13 place absolute accuracy is normally achieved there is a gradual loss of accuracy with increasing parameter values for example for n 10 sup 9 and with both nx and y near 10 sup 7 the accuracy can drop to ten places the function p sub n x y can be equated to the generalized marcum q function q sub m alpha beta the corresponding limits on alpha and beta are roughly 4500 for the 13 place accuracy and 60000 for ultimate integer 4 limit

an oscillation free flow solver based on flux reconstruction abstract in this paper a segregated algorithm is proposed to suppress high frequency oscillations in the velocity field for incompressible flows in this context a new velocity formula based on a reconstruction of face fluxes is defined eliminating high frequency errors in analogy to the rhie chow interpolation this approach is equivalent to including a flux based pressure gradient with a velocity diffusion in the momentum equation in order to guarantee second order accuracy of the numerical solver a set of conditions are defined for the reconstruction operator to arrive at the final formulation an outlook over the state of the art regarding velocity reconstruction procedures is presented comparing them through an error analysis a new operator is then obtained by means of a flux difference minimization satisfying the required spatial accuracy the accuracy of the new algorithm is analyzed by performing mesh convergence studies for unsteady navier stokes problems with analytical solutions the stabilization properties of the solver are then tested in a problem where spurious numerical oscillations arise for the velocity field the results show a remarkable performance of the proposed technique eliminating high frequency errors without losing accuracy

exponential type bounds on the generalized marcum q function with application to error probability analysis over fading channels strict upper and lower bounds of exponential type are derived for the generalized mth order marcum q function which enable simple evaluation of a tight upper bound on the average bit error probability performance of a wide class of noncoherent and differentially coherent communication systems operating over generalized fading channels for the case of frequency selective fading with arbitrary statistics per independent fading path the resulting upper hound on performance is expressed in the form of a product of moment generating functions of the instantaneous power random variables that characterize these paths

distance distribution of binary codes and the error probability of decoding we address the problem of bounding below the probability of error under maximum likelihood decoding of a binary code with a known distance distribution used on a binary symmetric channel bsc an improved upper bound is given for the maximum attainable exponent of this probability the reliability function of the channel in particular we prove that the random coding exponent is the true value of the channel reliability for codes rate r in some interval immediately below the critical rate of the channel an analogous result is obtained for the gaussian channel

new expressions for the pdf and cdf of the filtered output of an analog cross correlator corresp a general expression is derived for the probability density function pdf associated with the filtered output of an analog cross correlator the inputs of which consist of deterministic signals having the same frequency plus correlated stationary gaussian noise processes the correlator is composed of input bandpass filters a multiplier and a zonal iowpass filter the noise components in each channel have distinct variances and obey no spectral symmetry condition using the derived expression for the pdf the cumulative distribution function cdf under the same general conditions is calculated all previous known special cases are subsequently deduced from the general expressions given here the general results derived here are more suitable for numerical computations than comparable previous results found in the literature due to the fact that expressions here do not involve multiple infinite series lastly asymptotic formulas are developed for both the pdf and cdf which may be helpful in certain calculations

a unified approach to the probability of error for noncoherent and differentially coherent modulations over generalized fading channels we present a unified approach to determine the exact bit error rate ber of noncoherent and differentially coherent modulations with single and multichannel reception over additive white gaussian noise and generalized fading channels the multichannel reception results assume independent fading in the channels and are applicable to systems that employ post detection equal gain combining our approach relies on an alternate form of the marcum q function and leads to expressions of the ber involving a single finite range integral which can be readily evaluated numerically aside from unifying the past results the new approach also allows for a more general solution to the problem in that it includes many situations that in the past defied a simple solution the best example of this occurs for multichannel reception where the fading on each channel need not be identically distributed nor even distributed according to the same family of distributions

modified q functions and their use in detection analysis the marcum s q function is extended to complex arguments in particular a set of modified generalized q functions for imaginary values of one or both arguments are defined and their properties are investigated an extended probabilistic interpretation for the modified q functions is given appealing to a proposed generalization of the concept of random variable complex pseudo random variables pseudo events and pseudo probability measures are defined which formally obey the usual rules of composition of probability measures of independent events the modified q functions are then used to derive the rayleigh multivariate multidimensional distribution function and the error probability for partially coherent detection of equicorrelated signals

new bounds for the generalized marcum q function in this paper we study the generalized marcum q function q nu a b where a nu 0 and b ges 0 our aim is to extend the results of corazza and ferrari ieee trans inf theory vol 48 pp 3003 3008 2002 to the generalized marcum q function in order to deduce some new tight lower and upper bounds the key tools in our proofs are some monotonicity properties of certain functions involving the modified bessel function of the first kind and some classical inequalities i e the cauchy buniakowski schwarz and chebyshev integral inequalities these bounds are shown to be very tight for large b i e the relative errors of our bounds converge to zero as b increases both theoretical analysis and numerical results are provided to show the tightness of our bounds

chernoff type bounds for the gaussian error function we study single term exponential type bounds also known as chernoff type bounds on the gaussian error function this type of bound is analytically the simplest such that the performance metrics in most fading channel models can be expressed in a concise closed form we derive the conditions for a general single term exponential function to be an upper or lower bound on the gaussian error function we prove that there exists no tighter single term exponential upper bound beyond the chernoff bound employing a factor of one half regarding the lower bound we prove that the single term exponential lower bound of this letter outperforms previous work numerical results show that the tightness of our lower bound is comparable to that of previous work employing eight exponential terms

generalized formulations for the rhie chow interpolation in this paper generalized formulations for the rhie chow interpolation for co located grid discretizations are derived these generalized formulations eliminate the major known defects in the standard rhie chow interpolation including the following dependence of the converged solution on the value of the under relaxation factor saw tooth pressure oscillations in transient problems with small time steps and incorrect or non converged solutions for problems with discontinuities the generalized formulations are also shown to be applicable to a wider range of flow conditions than the standard rhie chow interpolation the derivation of the rhie chow interpolation is first recalled and its numerical errors are analyzed then the generalized formulations are presented and explained and the way in which they eliminate or counter some of the known defects of the standard rhie chow interpolation are outlined the generalized formulations are then verified and validated with numerical experiments including experiments with flow in porous media and in a packed bed it is then concluded that the generalized formulations presented in this work represent an advance over the standard rhie chow interpolation with a negligible increase in computational cost

projection methods for two velocity two pressure models for flows of heterogeneous mixtures in this paper a numerical analysis of two velocity two pressure models for flows of solid particles and fluids is presented first a formal exploitation of the weak formulation of such models asserts that they are amenable to integration via projection methods the challenging issues in the algorithm development for these models are then documented and suitable numerical methodologies for their remedy are devised subsequently an algorithm for the integration of the models of interest is proposed this is a two phase projection method on collocated grids that utilizes a fractional step time marching scheme it is further endowed with an interface detection and treatment methodology to properly account for the stiffness induced by the presence of moving and deforming material interfaces the efficiency and robustness of the proposed numerical method are assessed in a series of numerical experiments that are delineated in the last part of this paper

bounds for the generalized marcum q function abstract in this paper we consider the generalized marcum q function of order 0 real defined by q a b 1 a 1 b t e t 2 a 2 2 i 1 at dt where a 0 b 0 and i stands for the modified bessel function of the first kind our aim is to extend some results on the first order marcum q function to the generalized marcum q function in order to deduce some new lower and upper bounds moreover we show that the proposed bounds are very tight for the generalized marcum q function of integer order and we deduce some new inequalities for the more general case of real order the chief tools in our proofs are some monotonicity properties of certain functions involving the modified bessel function of the first kind which are based on a criterion for the monotonicity of the quotient of two maclaurin series

comparison of generalized q function algorithms corresp several methods have been proposed for calculating the generalized q function q m alpha beta but only isolated comparisons of the various techniques have been reported the accuracy range and execution time of prominent methods for computing the q function are compared and limitations of the algorithms are identified

on the distance distribution of codes the distinct distribution of a binary code c is the sequence b sub i sub i 0 sup n defined as follows let b sub i w be the number of codewords at distance i from the codeword w and let b sub i be the average of b sub i w over all w in c in this correspondence we study the distance distribution for codes of length n and minimal distance spl delta n with spl delta 0 fixed and n spl rarr spl infin our main aim is to relate the size of the code with the distribution of distances near the minimal distance

high snr consistent linear model order selection and subset selection high snr consistency of model order selection criteria in linear regression models has attracted a lot of attention in the signal processing community recently it is now known that exponentially embedded family versions of minimum description length etc are high snr consistent however a general framework for high snr consistency in linear regression is still missing this paper fills this gap by deriving necessary and sufficient conditions nscs for model order selection criteria in both known and unknown noise variance situations to be high snr consistent many popular model order selection criteria are proved to be high snr consistent using these nscs we also provide a convergence rate analysis to discriminate between various high snr consistent model order selection criteria a direct application of model order selection techniques to the very important subset selection problem is computationally infeasible this paper establish the high snr consistency of an existing t statistics based index ordering scheme that allows the conversion of a subset selection problem into a model order selection problem combining this index ordering with high snr consistent model order selection criteria leads to a novel subset selection procedure ssp that is numerically shown to outperform existing high snr consistent ssps

analytic expressions and bounds for special functions and applications in communication theory this paper is devoted to the derivation of novel analytic expressions and bounds for a family of special functions that are useful in wireless communication theory these functions are the well known nuttall q function incomplete toronto function rice ie function and incomplete lipschitz hankel integrals capitalizing on the offered results useful identities are additionally derived between the above functions and humbert phi 1 function as well as for specific cases of the kampede feriet function these functions can be considered as useful mathematical tools that can be employed in applications relating to the analytic performance evaluation of modern wireless communication systems such as cognitive radio cooperative and free space optical communications as well as radar diversity and multiantenna systems as an example new closed form expressions are derived for the outage probability over nonlinear generalized fading channels namely alpha eta mu alpha lambda mu and alpha kappa mu as well as for specific cases of the eta mu and lambda mu fading channels furthermore simple expressions are presented for the channel capacity for the truncated channel inversion with fixed rate and corresponding optimum cutoff signal to noise ratio for single antenna and multiantenna communication systems over rician fading channels the accuracy and validity of the derived expressions is justified through extensive comparisons with respective numerical results

tight bounds for the generalized marcum q function abstract in this paper we study the generalized marcum q function of order 0 real defined by q a b 1 a 1 b t e t 2 a 2 2 i 1 a t dt where a 0 b 0 and i stands for the modified bessel function of the first kind our aim is to improve and extend some recent results of wang to the generalized marcum q function in order to deduce some sharp lower and upper bounds in both cases b a and b a we give the best possible upper bound for q a b the key tools in our proofs are some monotonicity properties of certain functions involving the modified bessel function of the first kind these monotonicity properties are deduced from some results on modified bessel functions which have been used in wave mechanics and finite elasticity

strong asymptotics for krawtchouk polynomials we determine the strong asymptotics for the class of krawtchouk polynomials on the real line we show how our strong asymptotics describes the limiting distribution of the zeros of the krawtchouk polynomials

computing and bounding the first order marcum q function a geometric approach a geometric interpretation of the first order marcum q function q a b is introduced as the probability that a complex gaussian random variable with real mean a takes on values outside of a disk co b of radius b centered at the origin o this interpretation engenders a fruitful approach for deriving new representations and tight upper and lower bounds on q a b the new representations obtained involve finite range integrals with pure exponential integrands they are shown to be simpler and more robust than their counterparts in the literature the new bounds obtained include the generic exponential bounds which involve an arbitrarily large number of exponential functions and the simple erfc bounds which involve just a few erfc functions together with exponential functions in some cases the new generic exponential bounds approach the exact value of q a b as the number of exponential terms involved increases these generic exponential bounds evaluated with only two terms and the new simple erfc bounds are much tighter than the existing exponential bounds in most cases especially when the arguments a and b are large thus in many applications requiring further analytical manipulations of q a b these new bounds can lead to some closed form results which are better than the results available so far

algorithm for calculating the noncentral chi square distribution this article presents a new algorithm for evaluating the noncentral chi square distribution based on parl s 1980 method of neumann series expansion it is applicable to both even and odd degrees of freedom unlike most prior work which has been directed at the even cases convergence tests and procedures for detection of loss of precision are given the overall method is extremely simple to program accurate to many decimal places where applicable and efficient over a wide range of parameters the method is reliable provided the proper expansion is chosen based on the parameters

upper bound on list decoding radius of binary codes consider the problem of packing hamming balls of a given relative radius subject to the constraint that they cover any point of the ambient hamming space with multiplicity at most l for odd l ge 3 an asymptotic upper bound on the rate of any such packing is proved the resulting bound improves the best known bound due to blinovsky 1986 for rates below a certain threshold the method is a superposition of the linear programming idea of ashikhmin barg and litsyn that was previously used to improve the estimates of blinovsky for l 2 and a ramsey theoretic technique of blinovsky as an application it is shown that for all odd l the slope of the rate radius tradeoff is zero at zero rate

a theoretical and experimental comparison of output signal to noise ratios of three types of cross correlators the output signal to noise ratio as a function of input signal to noise ratios is compared for three different types of cross correlators 1 the standard analog cross correlator consisting of bandpass filters multiplier and low pass filter 2 the polarity coincidence correlator pcc which incorporates hard limiters in each analog input channel and 3 a modified type of pcc wherein only one of the analog channels utilizes a hard limiter some of the previous theoretical work on the pcc is extended to include new expressions for the output signal to noise ratio from which computations can more readily be made in addition discrete circuits were fabricated that closely approximate idealized elements so as to experimentally verify the theoretical results in almost all cases tested the experimental results were in close agreement with the math models

calculating time dependent performance measures for the m m 1 queue methods are discussed for computing transient performance measures for the m m 1 queue these performance measures are often expressed in terms of modified bessel functions without any discussion about computation in fact a common expression for the probability transition function of the m m 1 queue length process has an infinite sum of modified bessel functions for actually generating numbers however it is convenient to use numerical integration with associated integral representations as was first pointed out by p m morse oper res vol 3 p 255 61 1955