coded continuous phase modulation with low complexity noncoherent reception coded continuous phase modulation based on a feedback free modulator with noncoherent detection is discussed low complexity receiver processing is achieved by using only two or three linear filters for demodulation and applying noncoherent sequence estimation with reduced state viterbi decoding and simple branch metric calculation overall the proposed noncoherent receiver provides significant advantages over previously presented approaches

on the capacity achieving distribution of the discrete time noncoherent and partially coherent awgn channels we investigate the communication limits over rapid phase varying channels and consider the capacity of a discrete time noncoherent additive white gaussian noise ncawgn channel under the average power constraint we obtain necessary and sufficient conditions for the capacity achieving input distribution and show that this distribution is discrete and possesses an infinite number of mass points using this characterization of the capacity achieving distribution we compute a tight lower bound on the capacity of the channel based on examining suboptimal input distributions in addition we provide some easily computable lower and upper bounds on the channel capacity finally we extend some of these results to the partially coherent channel where it is assumed that a phase locked loop pll is used to track the carrier phase at the receiver and that an ideal interleaver and de interleaver are employed rendering the tikhonov distributed residual phase errors statistically independent from one symbol interval to another

nd convolutional codes i performance analysis a noncoherent coded system which incorporates convolutional codes in conjunction of multiple symbol noncoherent detection is presented in this two part paper where part i focuses on the performance analysis of the system and part ii deals with the structural properties of the underlying convolutional codes these convolutional codes are referred to as nd convolutional codes it is shown that nd convolutional codes provide a general framework for various noncoherent coding systems including differential systems two models of the carrier phase are examined and the relationships between them is established for the first one the carrier phase remains constant for l channels signals whereas for the second one it unvaries throughout the transmission period the regular structure of nd codes facilitates the evaluation of a simple upper bound on the pairwise and bit error probabilities as well as a simple expression for the generalized cutoff rate the exponential rate of the error probability which is the single parameter governing the error performance at large signal to noise ratios is identified via large deviations techniques this parameter leads to the interesting conclusion that increasing l does not necessarily monotonically improve the error performance of the noncoherent system the same conclusion is reached by examining upper bounds and computer simulation results of several interesting examples these examples also reveal that optimal codes for coherent detection are not necessarily optimal for noncoherent detection and a search for good codes some of which are tabulated in part ii of the paper is required

bit error rate of binary and quaternary dpsk signals with multiple differential feedback detection a differentially coherent detection scheme with improved bit error rate ber performance is presented for differentially encoded binary and quaternary phase shift keying psk modulation the improvement is based on using l symbol detectors with delays of 1 2 l symbol periods and on feeding back detected psk symbols exact formulas for the bit error probability are derived for the case that correct symbols are fed back the effect of symbol errors in the feedback path on the ber is determined by computer simulations

decoupling multivariate polynomials interconnections between tensorizations abstract decoupling multivariate polynomials is useful for obtaining an insight into the workings of a nonlinear mapping performing parameter reduction or approximating nonlinear functions several different tensor based approaches have been proposed independently for this task involving different tensor representations of the functions and ultimately leading to a canonical polyadic decomposition we first show that the involved tensors are related by a linear transformation and that their cp decompositions and uniqueness properties are closely related this connection provides a way to better assess which of the methods should be favored in certain problem settings and may be a starting point to unify the approaches second we show that taking into account the previously ignored intrinsic structure in the tensor decompositions improves the uniqueness properties of the decompositions and thus enlarges the applicability range of the methods

multiple symbol differential detection with interference suppression a multiple symbol differential detector is formulated for m ary differential phase shift keying modulation where the channel state information is unknown to the receiver the maximum likelihood decision statistic is derived for the detector and its performance is demonstrated by analysis and simulation under the gaussian assumption for the aggregate interference plus noise an exact expression for the symbol pairwise error probability is developed for m ary differential phase shift keying modulation over a diversity slow fading rayleigh channel in the presence of an interference source a simpler expression of the pairwise error probability is developed for the asymptotic case of large signal to noise ratio and small signal to interference ratio it is shown that with an increasing observation interval the performance of the differential detector over an unknown channel approaches that of optimum combining with known channel

time periodic solutions of the compressible magnetohydrodynamic equations abstract the compressible magnetohydrodynamic equations with a time periodic external force in r n are studied in this paper we establish the existence uniqueness and time asymptotic stability of time periodic solutions when n 5 our proof is essentially based on a combination of the energy method and the time decay estimates of solutions to the linearized system

noncoherent coded modulation trellis coded modulation with two or multidimensional signal constellations together with coherent maximum likelihood detection is considered an attractive solution for communications over the additive white gaussian noise awgn channel in this paper a new noncoherent communication system is introduced called noncoherent coded modulation ncm as an alternative to coherent coded modulation ncm achieves almost the same power efficiency without bandwidth expansion or an extensive increase in complexity as a noncoherent system the method does not need carrier phase estimation nonetheless differential encoding is not required high performance noncoherent detection is achieved by using multiple symbol observations unlike previous approaches a sliding window for the observations is used with each observation covering several branches of the trellis such that the observations are time overlapped we define a new type of noncoherent maximum likelihood sequence estimator mlse and analyze its performance over the awgn channel by numerical calculation of the union bound we perform a computerized search and present new codes for noncoherent detection with their performance the new codes cover many useful rates and complexities and achieve higher performance than existing codes for noncoherent detection the method can also be used for multiple symbol demodulation of mdpsk with better results than existing methods

joint noncoherent demodulation and decoding for the block fading channel a practical framework for approaching shannon capacity the paper contains a systematic investigation of practical coding strategies for noncoherent communication over fading channels guided by explicit comparisons with information theoretic benchmarks noncoherent reception is interpreted as joint data and channel estimation assuming that the channel is time varying and a priori unknown we consider iterative decoding for a serial concatenation of a standard binary outer channel code with an inner modulation code amenable to noncoherent detection for an information rate of about 1 2 bit per channel use the proposed scheme using a quaternary phase shift keying qpsk alphabet provides performance within 1 6 1 7 db of shannon capacity for the block fading channel and is about 2 5 3 db superior to standard differential demodulation in conjunction with an outer channel code we also provide capacity computations for noncoherent communication using standard phase shift keying psk and quadrature amplitude modulation qam alphabets comparing these with the capacity with unconstrained input provides guidance as to the choice of constellation as a function of the signal to noise ratio these results imply that qpsk suffices to approach the unconstrained capacity for the relatively low information and fading rates considered in our performance evaluations but that qam is superior to psk for higher information or fading rates motivating further research into efficient noncoherent coded modulation with qam alphabets

global existence of large solutions to initial boundary value problems for a viscous heat conducting one dimensional real gas abstract the existence of global classical solutions to initial boundary value problems in the dynamics of a one dimensional viscous heat conducting gas is established the nonlinear dissipative effects turn out to be sufficiently strong to prevent the development of singularities

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

generalized stokes parameters shift keying a new perspective on optimal detection over electrical and optical vector incoherent channels we consider block transmission over the incoherent channel whereby several symbols either launched consecutively in time or in parallel over several diversity paths are equally affected by common isotropic phase and additively corrupted by circularly gaussian additive noise our novel approach toward transmission over such a vector incoherent channel vic model is based on coherency matrix and generalized stokes parameters gsp descriptions of optimal detection inspired by classical optical polarization theory but further extended to the dual context of generic electrical as well as optical communication the four classical real valued parameters introduced into optics by stokes in 1853 to characterize the state of polarization of an optical beam extended to d sup 2 gsp underlie our new alternative novel description of maximum a posteriori maximum likelihood map ml optimal detection over the vic channel the modulation formats of polarization shift keying polsk differential phase shift keying and amplitude shift keying as well as recent and novel combinations thereof will all be seen to be equivalent to a new conceptual form of modulation called gsp shift keying several forms of the optimal map ml receiver for vector multienergy transmission are developed generalizing the classical scalar incoherent receiver and the known polsk receivers

turbo dpsk using soft multiple symbol differential sphere decoding coded interleaved differential m ary phase shift keying m dpsk with iterative decoding the so called turbo dpsk is known as a power efficient transmission format due to the rotational invariance of dpsk it particularly enables detection without channel state information csi however the soft input soft output siso component decoder for dpsk is the computational bottleneck if performance close to the ideal case of perfect csi is desired in this paper we take a fresh look at siso decoding without csi and apply sphere decoding sd to reduce complexity in particular we devise a maximum a posteriori probability map multiple symbol differential sphere decoder msdsd which efficiently solves the high dimensional search problem inherent to detection without csi together with a soft output generation device the map msdsd algorithm forms a new siso msdsd module for iterative decoding we analyze the extrinsic information transfer exit characteristic of the novel module by means of which we are able to design powerful encoder and decoder structures for respectively the additive white gaussian noise awgn and the continuously time varying rayleigh fading channel without csi these designs operate within 1 7 1 9 and 2 3 2 5 db of channel capacity assuming perfect csi these figures compare favorably with results available in the literature especially for reasonably high data rates of 1 2 bit channel use simulation studies of the average and the maximum complexity required by siso msdsd demonstrate the advantageous performance versus complexity tradeoff of our approach

global solutions of nonlinear magnetohydrodynamics with large initial data a free boundary problem for nonlinear magnetohydrodynamics with general large initial data is investigated the existence uniqueness and regularity of global solutions are established with large initial data in h1 it is shown that neither shock waves nor vacuum and concentration in the solutions are developed in a finite time although there is a complex interaction between the hydrodynamic and magnetodynamic effects an existence theorem of global solutions with large discontinuous initial data is also established

soft output decoding of rotationally invariant codes over channels with phase noise we consider rotationally invariant ri trellis coded modulations tcms transmitted over channels affected by phase noise to describe the main ideas of this paper we first concentrate as a case study on the simplest ri scheme namely the differentially encoded m ary phase shift keying m psk signal for this problem we use the framework based on factor graphs fgs and the sum product algorithm spa to derive the exact maximum a posteriori map symbol detection algorithm by analyzing its properties we demonstrate that it can be implemented by a forward backward estimator of the phase probability density function followed by a symbol by symbol completion to produce the a posteriori probabilities of the information symbols to practically implement the forward backward phase estimator we propose a couple of schemes with different complexity the resulting algorithms exhibit an excellent performance and in one case only a limited complexity increases with respect to the algorithm that perfectly knows the channel phase the properties of the optimal decoder and the proposed practical decoding schemes are then extended to the case of a generic ri code the proposed soft output algorithms can also be used in iterative decoding schemes for concatenated codes employing ri inner components among them in the numerical results we consider repeat accumulate ra codes and other serially concatenated schemes recently proposed in the technical literature

adaptive noncoherent dfe for mdpsk signals transmitted over isi channels a novel noncoherent decision feedback equalization ndfe scheme for m ary differential phase shift keying signals transmitted over intersymbol interference channels is presented a suboptimum version with lower computational complexity and a noncoherent linear equalizer nle are derived from the original ndfe scheme furthermore the relation of the novel nle to a previously proposed nle is investigated in contrast to known ndfe schemes the novel scheme can approach the performance of coherent minimum mean squared error decision feedback equalization for adaptation of the feedforward and feedback filters efficient novel modified least mean square and recursive least squares algorithms are presented finally it is shown that the proposed adaptive ndfe scheme is robust against frequency offset

tcm with differential encoding set partitioning trellis designs and distance analysis differential encoding de is a classical technique at the transmitter that allows simple noncoherent detection at the receiver on the other hand trellis coded modulation tcm is a bandwidth efficient technique which offers reliable data transmission in this paper we aim to find the best concatenation order of tcm and de for channel phase coherence over n 2 symbols besides the well known tcm followed by de called tcm de we propose a new trellis coding extension of de which extends our earlier work called differential trellis coded modulation dtcm dtcm is tcm with de defined in states where distinct states may have distinct de functions we propose design methods of de functions for noncoherently non catastrophic dtcm for both tcm de and dtcm we propose additive distance measures and set partitioning based on the proposed set partitioning trellis codes are designed or searched for both tcm de and dtcm both minimum distances and simulation results show that tcm de outperforms dtcm and the obtained new codes are better than the original codes

kalman state filtering based least squares iterative parameter estimation for observer canonical state space systems using decomposition this paper focuses on the parameter and state estimation problems for observer canonical state space systems from measurement information derives a kalman filter based least squares iterative kf lsi algorithm to estimate the parameters and states and a model decomposition based kf lsi algorithm to enhance computational efficiency an example is provided to confirm the effectiveness of the proposed algorithms

noncoherent sequence detection new noncoherent sequence detection algorithms for combined demodulation and decoding of coded linear modulations transmitted over additive white gaussian noise channels possibly affected by intersymbol interference are presented optimal sequence detection in the presence of a random rotation of the signal phase assumed to be constant during the entire transmission requires a receiver complexity exponentially increasing with the duration of the transmission based on proper approximations simple suboptimal detection schemes based on the viterbi algorithm are presented whose performance approaches that of coherent detection in a companion paper by colavolpe and raheli see ibid vol 47 no 9 p 1303 7 1999 noncoherent sequence detection is extended to continuous phase modulations in the proposed schemes the tradeoff between complexity and performance is simply controlled by a parameter referred to as implicit phase memory and the number of states of a trellis diagram besides being realizable these schemes have the convenient feature of allowing us to remove the constant phase assumption and encompass time varying phase models the proposed schemes compare favorably with other solutions previously proposed in the technical literature

multiple symbol differential detection with diversity reception in this letter we first consider the maximum likelihood sequence estimator for multiple symbol differential detection msdd over the slow fading diversity channel since this optimum decision metric results in a complex receiver implementation whose average bit error probability bep performance is difficult if not impossible to obtain analytically we then focus our attention on evaluating the average bep for msdd with diversity reception in the form of postdetection equal gain combining egc giving emphasis to its ability to bridge the gap between egc of conventional differentially detected m psk and maximal ratio combining of coherently detected m psk with differential encoding

existence and uniqueness of steady solutions to the magnetohydrodynamic equations of compressible flows abstract we establish the existence and uniqueness of a strong solution to the steady magnetohydrodynamic equations for the compressible barotropic fluids in a bounded smooth domain with a perfectly conducting boundary under the assumption that the external force field is small

symmetric tensor decomposition by an iterative eigendecomposition algorithm we present an iterative algorithm called the symmetric tensor eigen rank one iterative decomposition steroid for decomposing a symmetric tensor into a real linear combination of symmetric rank 1 unit norm outer factors using only eigendecompositions and least squares fitting originally designed for a symmetric tensor with an order being a power of two steroid is shown to be applicable to any order through an innovative tensor embedding technique numerical examples demonstrate the high efficiency and accuracy of the proposed scheme even for large scale problems furthermore we show how steroid readily solves a problem in nonlinear block structured system identification and nonlinear state space identification

parametric identification of structured nonlinear systems in this paper identification of structured nonlinear systems is considered using linear fractional transformations lft the a priori information regarding the structural interconnection is systematically exploited a parametric approach to the identification problem is investigated where it is assumed that the linear part of the interconnection is given and the input to the nonlinear part is measurable an algorithm for the identification of the nonlinear part is proposed the uniqueness properties of the estimate provided by the algorithm are examined it is shown that the estimate converges asymptotically to its true value under a certain persistence of excitation condition two simulated examples and a real data example are presented to show the effectiveness of the proposed algorithm

the performance of trellis coded mdpsk with multiple symbol detection the idea of using a multiple more than two symbol observation interval to improve error probability performance is applied to differential detection of trellis coded multiple phase shift keying mpsk over an additive white gaussian noise awgn channels an equivalent euclidean distance measure per trellis branch is determined for this detection scheme this is used to define an augmented larger multiplicity trellis code whose distance measure is the conventional squared euclidean distance typical of conventional trellis coded modulation on the awgn such an augmented multiple trellis code is a convenient mathematical tool for simplifying the analysis results are obtained by a combination of analysis and computer simulation it is shown that only a slight increase e g one symbol in the length of the observation interval will provide a significant improvement in bit error probability performance

noncoherent block coded tapsk for coherent detection block coded modulation is a bandwidth efficient scheme in this paper we propose theorems about the error performance of block coded modulation using m ary phase shift keying mpsk for noncoherent detection based on these theorems we propose a novel block coded modulation scheme for noncoherent detection called noncoherent block coded mpsk the proposed scheme provides flexible designs of noncoherent block codes with different code rate block length and error performance good noncoherent block codes can be easily obtained by properly choosing binary linear block codes as the component codes moreover noncoherent block codes of this new scheme can be decoded by multistage decoding which has the advantage of low complexity and satisfactory error performance in this paper two algorithms of multistage decoding for noncoherent detection are proposed as well the error performance of some designed codes and decoding algorithms is verified by computer simulation

the phase of a vector perturbed by gaussian noise and differentially coherent receivers some results are presented regarding the asymptotic distribution of the phase of a vector perturbed by gaussian noise it is shown that for large signal to noise ratio the asymptotic distribution of the phase is of the tikhonov type this framework is then used for the synthesis of differentially coherent receiver structures one for m ary phase shift keying mpsk and the other for minimum shift keying msk the first structure bridges the performance gap between coherent and differentially coherent demodulation of mpsk the msk receiver uses matched filtering with differential demodulation

reduced state sequence estimation with set partitioning and decision feedback a reduced state sequence estimator for linear intersymbol interference channels is described the estimator uses a conventional viterbi algorithm with decision feedback to search a reduced state subset trellis that is constructed using set partitioning principles the complexity of maximum likelihood sequence estimation mlse due to the length of the channel memory and the size of the signal set is systematically reduced an error probability analysis shows that a good performance complexity tradeoff can be obtained in particular the results indicate that the required complexity to achieve the performance of mlse is independent of the size of the signal set for large enough signal sets simulation results are provided for two partial response systems a simple technique for quadrature partial response signaling qprs is described that eliminates the quasicatastrophic nature of the ml trellis

navier stokes equations for compressible fluids global existence and qualitative properties of the solutions in the general case we consider the equations which describe the motion of a viscous compressible fluid taking into consideration the case of inflow and or outflow through the boundary by means of some a priori estimates we prove the existence of a global in time solution moreover as a consequence of a stability result we show that there exist a periodic solution and a stationary solution

channel coding with multilevel phase signals a coding technique is described which improves error performance of synchronous data links without sacrificing data rate or requiring more bandwidth this is achieved by channel coding with expanded sets of multilevel phase signals in a manner which increases free euclidean distance soft maximum likelihood ml decoding using the viterbi algorithm is assumed following a discussion of channel capacity simple hand designed trellis codes are presented for 8 phase shift keying psk and 16 quadrature amplitude shift keying qask modulation these simple codes achieve coding gains in the order of 3 4 db it is then shown that the codes can be interpreted as binary convolutional codes with a mapping of coded bits into channel signals which we call mapping by set partitioning based on a new distance measure between binary code sequences which efficiently lower bounds the euclidean distance between the corresponding channel signal sequences a search procedure for more powerful codes is developed codes with coding gains up to 6 db are obtained for a variety of multilevel phase modulation schemes simulation results are presented and an example of carrier phase tracking is discussed

measurement and identification of nonlinear systems consisting of linear dynamic blocks and one static nonlinearity this paper considers the measurement and the identification of nonlinear time invariant single input single output siso systems consisting of a multivariable linear dynamic system and one static nonlinear siso system this includes wiener hammerstein systems in a linear feedback loop the nonparametric identification of the frequency response functions of the linear parts are obtained without measuring the signals over the static nonlinearity measurements on an electronic circuit demonstrate the usability of this identification scheme

noncoherent block coded tapsk and 16qam using linear component codes in this paper we derive minimum noncoherent distances of block coded tapsk twisted amplitude and phase shift keying and 16qam quadrature amplitude modulation both using linear component codes according to the derived distances noncoherent block coded tapsk nbc tapsk and noncoherent block coded 16qam nbc 16qam are proposed if the block length is very small nbc 16tapsk performs best among all noncoherent schemes and nbc 16qam performs worse due to its small minimum noncoherent distance however if the block is not short nbc 16qam has the best error performance because the codewords with small noncoherent distances are rare

rotationally invariant and rotationally robust codes for the awgn and the noncoherent channel the paper investigates the design and robustness of rotationally invariant ri codes first ri codes are extended to the case of serially concatenated sc trellis coded modulation tcm and several high rate powerful ri sctcm codes are designed over 8 phase shift keying and 16 quadrature amplitude modulation alphabets the investigation continues by considering more realistic channels that introduce cycle slips during phase estimation and thus rotate only part of the transmitted codeword it is proven that ri codes with small state space are robust in these channels even when traditional coherent decoders are utilized furthermore it is demonstrated through simulations that the addition of a simple stopping criterion to the coherent iterative decoding algorithm is sufficient for robustness of the more powerful ri sctcm codes when partial codeword rotations are considered finally it is investigated whether ri codes are useful for transmission in the noncoherent channel it is proved that ri codes are as good as any other good codes for this channel when the phase dynamics are low and optimal decoding is performed however it is shown that for a certain class of receivers ri codes are also robust to partial phase rotations in this channel

subspace based multivariable system identification from frequency response data two noniterative subspace based algorithms which identify linear time invariant mimo multi input multioutput systems from frequency response data are presented the algorithms are related to the recent time domain subspace identification techniques the first algorithm uses equidistantly in frequency spaced data and is strongly consistent under weak noise assumptions the second algorithm uses arbitrary frequency spacing and is strongly consistent under more restrictive noise assumptions promising results are obtained when the algorithms are applied to real frequency data originating from a large flexible structure

noncoherent amplitude phase modulated transmission schemes for rayleigh block fading channels in this paper we investigate noncoherent transmission schemes using amplitude phase modulation for uncoded transmission schemes we derive the pairwise error probability pep and its high snr approximation for signal vectors with unequal power values using a noncoherent maximum likelihood detector under rayleigh block fading channels for coded transmission schemes we consider differential amplitude phase modulated signals and introduce a codeword interleaving strategy to improve the error performance the design criteria for the signal labelling and bit interleaving are also derived via the high snr approximation of the pep at the receiver we devise an iterative channel amplitude estimator to enhance the detection reliability with the help of a specially designed iterative receiving algorithm the designed noncoherent coded scheme can provide a significant improvement either in the error floor or the waterfall region

global smooth solutions for 1d thermally radiative magnetohydrodynamics this paper is concerned with the global existence of smooth solutions to equations describing one dimensional motion of a self gravitating radiative of magnetohydrodynamics gas we have proved that for any arbitrary large smooth initial data the problem under consideration admits a unique globally smooth classical solution our results have improved the results given by zhang and xie j differ equations 52 1853 1882 2008

df dd for channels with phase noise in this letter we design decision feedback differential detection df dd schemes for channels with phase noise if the df dd feedback filter is properly optimized a performance similar to that of a more complex scheme recently reported by chiavaccini and vitetta based on expectation maximization can be achieved however it is also shown that an error floor is unavoidable for channels with phase noise if a constraint is introduced the df dd receiver can be made robust against unknown frequency offsets

incompressible limit of the compressible magnetohydrodynamic equations with periodic boundary conditions this paper is concerned with the incompressible limit of the compressible magnetohydrodynamic equations with periodic boundary conditions it is rigorously shown that the weak solutions of the compressible magnetohydrodynamic equations converge to the strong solution of the viscous or inviscid incompressible magnetohydrodynamic equations as long as the latter exists both for the well prepared initial data and general initial data furthermore the convergence rates are also obtained in the case of the well prepared initial data

multiple symbol differential detection of mpsk a differential detection technique for mpsk multiple phase shift keying which uses a multiple symbol observation interval is presented and its performance is analyzed and simulated the technique makes use of maximum likelihood sequence estimation of the transmitted phases rather than symbol by symbol detection as in the conventional differential detection thus the performance of this multiple symbol detection scheme fills the gap between conventional two symbol observation differentially coherent detection of mpsk and ideal coherent of mpsk with differential encoding the amount of improvement gained over conventional differential detection depends on the number of phases m and the number of additional symbol intervals added to the observation what is particularly interesting is that substantial performance improvement can be obtained for only one or two additional symbol intervals of observation the analysis and simulation results presented are for uncoded mpsk

decision feedback detectors for soqpsk we consider highly simplified decision feedback detectors for shaped offset quadrature phase shift keying soqpsk a highly bandwidth efficient and popular constant envelope modulation in particular we show that the state complexity can be reduced to a minimal level two states with asymptotically optimum performance as demonstrated by performance analysis and confirmed by computer simulations the complexity reduction is achieved by a novel manipulation of the differential encoder and the soqpsk precoder which are both part of the transmission model for soqpsk we give two possible architectures for achieving this complexity reduction the pulse amplitude modulation pam technique and the pulse truncation pt technique we also formulate these detectors for coherent and noncoherent detection the resulting family of detectors makes use of recent advances in soqpsk technology based on a continuous phase modulation cpm interpretation of soqpsk the proposed simplifications are significant because they minimize the complexity of trellis based soqpsk detectors which have become available only in recent years because trellis based soqpsk detectors are 1 2 db superior to the widely deployed family of symbol by symbol soqpsk detectors the proposed two state detectors offer the simplest means of achieving these performance gains thus these simple detection schemes are applicable in settings where high performance and low complexity are needed to meet restrictions on power consumption and cost

on the information rate and repeat accumulate code design for phase noise channels we investigate the information rate of channels affected by phase noise aiming at predicting the ultimate performance limits in this scenario moreover a closed form upper bound is also derived for phase shift keying psk modulations finally we consider the design of nonsystematic irregular repeat accumulate ra codes for this channel trying to give new insights on the codes to be employed for such an application

theoretical analysis and performance limits of noncoherent sequence detection of coded psk a theoretical performance analysis of noncoherent sequence detection schemes previously proposed by the authors for combined detection and decoding of coded m ary phase shift keying m psk is presented a method for the numerical evaluation of the pairwise error probability for which no closed form expressions exist is described the classical union bound is computed and results are compared with computer simulations an upper bound on this pairwise error probability is also presented this upper bound may be effectively used for the definition of an equivalent distance which may be useful in exhaustive searches for optimal codes using this bound it is proven that in the general coded case the considered noncoherent decoding schemes perform as close as desired to an optimal coherent receiver when a phase memory parameter is sufficiently large in the case of differentially encoded m psk a simple expression of the asymptotic bit error probability is derived which is in agreement with simulations for high as well as low signal to noise ratio snr

identification of systems with localised nonlinearity from state space to block structured models this paper presents a method that generates initial estimates for a rather general block structured model starting from the more general polynomial nonlinear state space model the considered block structure sometimes referred to as linear fractional transformation lft or linear fractional representation lfr encompasses several simpler structures it can e g describe wiener hammerstein wiener hammerstein and nonlinear feedback structures in fact the chosen block structure is the most general representation of a system with one single input single output siso static nonlinearity as is quite common in block structure identification the states and internal signals are assumed to be unknown the method gradually imposes the structure of the lfr system and at the same time finds an estimate of the multiple input multiple output mimo linear dynamic part and the static nonlinearity snl the method is illustrated via an experimental data example

noncoherent sequence detection of continuous phase modulations in this paper noncoherent sequence detection proposed in a companion paper by colavolpe and raheli see ibid vol 47 no 9 p 1376 85 1999 is extended to the case of continuous phase modulations cpms the results in the companion paper on linear modulations with intersymbol interference isi are used here because a cpm signal is mathematically equivalent to a sum of isi affected linearly modulated components according to the laurent decomposition the proposed suboptimal detection schemes have a performance which approaches that of coherent detection with acceptable complexity allow for time varying phase models and compare favorably with previously proposed solutions

low mach number limit for the full compressible magnetohydrodynamic equations with general initial data abstract the low mach number limit for the full compressible magnetohydrodynamic equations with general initial data is rigorously justified in the whole space r 3 first the uniform in mach number estimates of the solutions in a sobolev space are established on a finite time interval independent of the mach number then the low mach number limit is proved by combining these uniform estimate with a theorem due to metivier and schochet 2001 45 for the euler equations that gives the local energy decay of the acoustic wave equations

identification of block oriented nonlinear systems starting from linear approximations a survey abstract block oriented nonlinear models are popular in nonlinear system identification because of their advantages of being simple to understand and easy to use many different identification approaches were developed over the years to estimate the parameters of a wide range of block oriented nonlinear models one class of these approaches uses linear approximations to initialize the identification algorithm the best linear approximation framework and the approximation framework or equivalent frameworks allow the user to extract important information about the system guide the user in selecting good candidate model structures and orders and prove to be a good starting point for nonlinear system identification algorithms this paper gives an overview of the different block oriented nonlinear models that can be identified using linear approximations and of the identification algorithms that have been developed in the past a non exhaustive overview of the most important other block oriented nonlinear system identification approaches is also provided throughout this paper

initial boundary value problems for the equations of motion of compressible viscous and heat conductive fluids the equations of motion of compressible viscous and heat conductive fluids are investigated for initial boundary value problems on the half space and on the exterior domain of any bounded region the global solution in time is proved to exist uniquely and approach the stationary state ast provided the prescribed initial data and the external force are sufficiently small

an l p theory for the n dimensional stationary compressible navier stokes equations and the incompressible limit for compressible fluids the equilibrium solutions in this paper we study the system 1 1 1 3 which describes the stationary motion of a given amount of a compressible heat conducting viscous fluid in a bounded domain ofr n n 2 hereu x is the velocity field x is the density of the fluid x is the absolute temperature f x andh x are the assigned external force field and heat sources per unit mass andp is the pressure in the physically significant case one hasg 0 we prove that for small data f g h there exists a unique solution u of problem 1 1 1 3 1 in a neighborhood of 0 m 0 for arbitrarily large data the stationary solution does not exist in general see sect 5 moreover we prove that for barotropic flows the stationary solution of the navier stokes equations 1 8 is the incompressible limit of the stationary solutions of the compressible navier stokes equations 1 7 as the mach number becomes small finally in sect 5 we will study the equilibrium solutions for system 4 1 for a more detailed explanation see the introduction

a per survivor phase estimation algorithm for detection of psk signals an expectation maximization em technique for maximum a posteriori map estimation of a random parameter is employed to devise a per survivor phase tracking algorithm for phase shift keyed signals transmitted over channels with phase jitter simulation results show that the proposed algorithm can provide substantial performance gains over recursive and nonrecursive phase estimators in the presence of a strong phase jitter

global well posedness of the cauchy problem for the navier stokes equations of nonisentropic flow with discontinuous initial data abstract we prove the global existence uniqueness and continuous dependence on initial data for discontinuous solutions of the navier stokes equations for nonisentropic compressible flow in one space dimension a great deal of information is obtained concerning the qualitative behavior of the solution including an analysis of the convection and evolution of jump discontinuities the derivation of sharp rates of smoothing and the l asymptotic behavior

further results on differential encoding by a table recently we proposed a novel differential encoder by a look up table in this paper we present further research results on this subject we first propose a bit assigning algorithm and construct some new tables for various constellations that maximize the minimum noncoherent distance then differential encoding for multiple symbol differential detection is proposed after that we indicate that differential encoding by a table is equivalent to differential encoding by a trellis so we propose a novel differential detector which uses the viterbi algorithm on the trellis a theorem about the sufficient number of states for various modulations is proposed in addition we further enhance the error performance of the proposed differential encoder by concatenating it with trellis coding for this noncoherent trellis coding scheme we propose augmented state viterbi decoding finally we extend the proposed differential encoding and detection to differential space time modulation dstm we propose a new definition of dstm by which the set of transmitted blocks is determined first the differential encoding is implemented by a look up table which can be optimized the proposed dstm has satisfactory error performance without constellation expansion

multiple symbol partially coherent detection of mpsk the authors show that by using the known or estimated value of carrier tracking loop snr in the decision metric it is possible to improve the error probability performance of a partially coherent mpsk system relative to that corresponding to the commonly used ideal coherent decision rule using a maximum likelihood approach an optimum decision metric is derived and shown to take the form of a weighted sum of the ideal coherent decision metric i e correlation and the noncoherent decision metric which is optimum for differential detection of mpsk the performance of a receiver based on this optimum decision rule is derived and shown to provide continued improvement with increasing length of observation interval data symbol sequence length unfortunately increasing the observation length does not eliminate the error floor associated with the finite loop snr nevertheless in the limit of infinite observation length the average error probability performance approaches the algebraic sum of the error floor and the performance of ideal coherent detection i e at any error probability above the error floor there is no degradation due to the partial coherence while the above is strictly speaking only true in the limit of infinite observation length it is shown that one can virtually achieve this limiting behavior with practical size observation lengths furthermore the performance is quite insensitive to mismatch between the estimate of loop snr e g obtained from measurement fed to the decision metric relative and its true value

noncoherent adaptive channel identification algorithms for noncoherent sequence estimation in this letter two novel noncoherent adaptive algorithms for channel identification are introduced the proposed noncoherent least mean square lms and noncoherent recursive least squares rls algorithms can be combined easily with noncoherent sequence estimation nse for m ary differential phase shift keying signals transmitted over intersymbol interference isi channels it is shown that the resulting adaptive noncoherent receivers are very robust against carrier phase variations for zero frequency offset the convergence speed and the steady state error of the noncoherent adaptive algorithms are similar to those of conventional lms and rls algorithms however the conventional algorithms diverge even for relatively small frequency offsets whereas the proposed noncoherent algorithms converge for relatively large frequency offsets simulations confirm the good performance of nse combined with noncoherent adaptive channel estimation in time variant fading isi channels

bandwidth efficient noncoherent trellis coded mpsk in this letter we propose a novel bandwidth efficient noncoherent trellis coded mpsk scheme in which a particularly designed differential encoder is added in front of the trellis encoder with this differential encoder trellis coded mpsk proposed by ungerboeck is no longer noncoherently catastrophic and thus achieves better error performance moreover new trellis codes which for the proposed scheme have better bit error rates than ungerboeck s codes are found by computer searches

noncoherent sequence detection of differential space time modulation approximate maximum likelihood noncoherent sequence detection nsd for differential space time modulation dstm in time selective fading channels is proposed the starting point is the optimum multiple symbol differential detection for dstm that is characterized by exponential complexity by truncating the memory of the incremental metric a finite state trellis is obtained so that a viterbi algorithm can be implemented to perform sequence detection compared to existing linear predictive receivers a distinguished feature of nsd is that it can accommodate nondiagonal constellations in continuous fading error analysis demonstrates that significant improvement in performance is achievable over linear prediction receivers by incorporating the reduced state sequence detection techniques performance and complexity tradeoffs can be controlled by the branch memory and trellis size numerical results show that most of the performance gain can be achieved by using an l state trellis where l is the size of the dstm constellation

iterative decision feedback differential demodulation of bit interleaved coded mdpsk for flat rayleigh fading channels a simple receiver structure previously proposed by the authors for convolutional coded m ary differential phase shift keying transmission over flat rayleigh fading channels without channel state information is analyzed in detail we present a thorough discussion of the iterative decoding procedure which is referred to as iterative decision feedback differential demodulation iterative df dm the convergence behavior of iterative df dm is theoretically examined the analysis supports the observation that the iterative decoding scheme works well for target bit error rates which are usually of interest furthermore the associated cut off rate for error free decision feedback is studied judging from this performance parameter remarkable gains in power efficiency compared to conventional differential demodulation are indicated while the computational complexity of the decoding remains low the results from information theory are in good agreement with the given simulation results

nd convolutional codes ii structural analysis for pt i see ibid vol 43 no 2 p 558 75 1997 the structural properties of a noncoherent coded system which incorporates convolutional codes in conjunction with multiple symbol noncoherent detection is presented in this second part of a two part paper where the performance analysis was provided in part i these convolutional codes are referred to as nd convolutional codes and they provide a general framework for various noncoherent coding systems including differential systems for several practical models of the carrier phase the exponential rate in which the error probability decays to zero derived in part i of the paper is used here to obtain the free equivalent distance of nd codes which is the single parameter dominating the error performance at large signal to noise ratios the free equivalent distance is upper bounded by the free nd distance which constitutes a more convenient and practical parameter to work with and it is the basis for a computer search for optimal nd codes the resultant codes of the computer search are compared to codes which are optimal for coherent detection and it is verified that the latter codes are not necessarily optimal for noncoherent detection since they exhibit in many cases a relatively small nd distance the ambiguity problem inherent to noncoherent systems is also treated in this paper in the general framework of nd catastrophic codes and necessary and sufficient conditions for catastrophic error propagation are identified

detection by multiple trellises in this paper we present a novel pragmatic approach referred to as detection by multiple trellises to perform trellis based detection over realistic channels more precisely we consider channels with unknown parameters and apply the concept of detection by multiple trellises to forward backward fb algorithms the key idea of our approach consists first of properly quantizing the channel parameters and then considering replication of coherent fb algorithms operating on parallel trellises one per hypothetical quantized value in order to make the receiver robust against a possibly time varying channel parameters the proposed soft output algorithms perform a proper manipulation of the forward and backward metrics computed by the parallel fb algorithms at regularly spaced trellis steps we consider two significant examples of application detection over i phase uncertain channels and ii fading channels the performance of the proposed algorithms is investigated considering differentially encoded de quaternary phase shift keying qpsk and iterative detection schemes based on low density parity check ldpc codes besides having a low complexity the proposed soft output algorithms turn out to be robust flexible blind in the sense that no knowledge of the channel parameter statistics is required and highly parallelizable as it is desirable in high throughput future wireless communication systems

identification of nonlinear systems using polynomial nonlinear state space models in this paper we propose a method to model nonlinear systems using polynomial nonlinear state space equations obtaining good initial estimates is a major problem in nonlinear modelling it is solved here by identifying first the best linear approximation of the system under test the proposed identification procedure is successfully applied to measurements of two physical systems

stability of stationary solution for the compressible viscous magnetohydrodynamic equations with large potential force in bounded domain abstract in this paper we consider the 3 d compressible viscous magnetohydrodynamic mhd equations with some large potential force in bounded rigid vessel we firstly construct the non constant stationary solutions of the compressible viscous mhd equations under suitable constitutive assumptions next a critical energy identity is established to achieve a universal stability criterion of the stationary solution in this case the stationary solution is exponential stable for any large external potential force finally we show the well posedness of the initial boundary value problem for the compressible viscous mhd equations with the large potential force provided that the prescribed initial data is close to the stationary solution it implies that the set satisfying the stability criterion is not empty

some mathematical questions related to the mhd equations some questions relating to the large time behavior of the solutions of mhd equations for a viscous incompressible resistive fluid are investigated the physical system is briefly described and the functional setting of the equations a flow in a bounded domain or in whole space with a space periodicity property in all directions the main existence and uniqueness results for weak and strong solutions of the mhd equations are recalled regularity properties and bounds on the solutions to the equations which are valid for all time are established and the concept of functional invariant sets is introduced which is contained in the space of smooth functions if the data are sufficiently regular the squeezing property of the trajectories are stated and it is shown that any functional invariant set for the mhd equations and in particular any attractor has a finite haussdorf dimension the flow is found to be totally determined for large dimensions by a finite number of parameters 26 references

maximum likelihood differential detection of uncoded and trellis coded amplitude phase modulation over awgn and fading channels spl minus metrics and performance this paper derives metrics for maximum likelihood differential detection of uncoded and trellis coded mpsk and qam transmitted over rayleigh and rician fading channels receiver structures based on these metrics are proposed and their error probability performance analyzed and or simulated the results represent a generalization of the notion of multiple symbol differential detection previously introduced by the authors for mpsk over an awgn to the fading channel and other modulations for the coded cases ideal interleaving deinterleaving is assumed and furthermore the presence or absence of channel state information an interesting side result is that for a constant envelope modulation transmitted over a fading channel with unknown but rapidly varying phase error the other extreme to the slowly varying phase error case normally assumed for differential detection under certain practical assumptions it is shown that the optimum receiver is of the limiter discriminator type

approximate ml decoding of coded psk with no explicit carrier phase reference an approximate method is discussed for maximum likelihood estimation of coded psk sequences in the presence of an unknown carrier phase this method makes use of the viterbi algorithm to find an optimum path in the encoder trellis diagram phase estimation is embedded into the structure of the detection algorithm and the branch metrics in the trellis are modified with respect to those employed with known carrier phase comparisons with traditional decoding schemes show that the proposed solution has better performance in terms of acquisition time and cycle slips

long time behavior of solution to the compressible magnetohydrodynamic equations abstract in this paper we study the long time behavior of solution for the compressible magnetohydrodynamic equations in three dimensional whole space more precisely we establish optimal decay rate for the higher order spatial derivatives of solution which improves the work of li and yu 2011 chen and tan 2010 furthermore one also investigates the long time behavior for the mixed space time derivatives of solution