the extended hyperbolic functions method and new exact solutions to the zakharov equations abstract the multiple exact solutions for the nonlinear evolution equations describing the interaction of laser plasma are developed the extended hyperbolic function method are employed to reveal these new solutions the solutions include that of the solitary wave solutions of bell type for n and e the solitary wave solutions of kink type for e and bell type for n the solitary wave solutions of a compound of the bell type and the kink type for n and e the singular traveling wave solutions periodic traveling wave solutions of triangle function types and solitary wave solutions of rational function types in addition to re deriving all known solutions in a systematic way several new and more general solutions can be obtained by using our method

semi blind simo flat fading channel estimation in unknown spatially correlated noise using the em algorithm we present a maximum likelihood ml method for semi blind estimation of single input multi output simo flat fading channels in spatially correlated noise having unknown covariance an expectation maximization em algorithm is utilized to compute the ml estimates of the channel and spatial noise covariance we derive the crame spl acute r rao bound crb matrix for the unknown parameters and present a symbol detector that utilizes the em channel estimates numerical simulations demonstrate the performance of the proposed method

link between solitary waves and projective riccati equations many solitary wave solutions of nonlinear partial differential equations can be written as a polynomial in two elementary functions which satisfy a projective hence linearizable riccati system from that property the authors deduce a method for building these solutions by determining only a finite number of coefficients this method is much shorter and obtains more solutions than the one which consists of summing a perturbation series built from exponential solutions of the linearized equation they handle several examples for the henon heiles hamiltonian system they obtain several exact solutions one of them defines a new solitary wave solution for a coupled system of boussinesq and nonlinear schrodinger equations for a third order dispersive equation with two monomial nonlinearities they isolate all cases where the general solution is single valued

comparison of em based algorithms for mimo channel estimation iterative channel estimation can improve the channel state information csi with respect to noniterative estimation new iterative channel estimators based on the expectation maximization em algorithm are proposed in this paper a first estimator called the unbiased em uem is designed to unbias the em estimates a second estimator is then put forward which is based on the expectation conditional maximization ecm algorithm and its complexity is lower than that of the em an unbiased ecm uecm estimator is also proposed although the unbiasedness of the uem and uecm estimators is not rigorously proved the use of these names is explained in the paper the new estimators are compared with well known ones such as the em the decision directed dd and the data aided da estimators simulations are reported for a turbo receiver operating over frequency selective multiple input multiple output channels it is shown that the uem channel estimator outperforms the em and that the ecm based estimators are very close to the em based ones

on the integrability of systems of nonlinear ordinary differential equations with superposition principles a new class of solvable nonlinear dynamical systems has been recently identified by the requirement that the ordinary differential equations ode s describing each member of this class possess nonlinear superposition principles these systems of ode s are generally not derived from a hamiltonian and are classified by associated pairs of lie algebras of vector fields in this paper all such systems of n 3 ode s are integrated in a unified way by finding explicit integrals for them and relating them all to a pivotal member of their class the projective riccati equations moreover by perturbing two parametrically driven projective riccati equations thus making them nonsolvable in the above sense evidence is discovered of chaotic behavior on the poincare surface of section in the form of sensitive dependence on initial conditions near a boundary separating bounded from unbounded motion

generalized tanh method with symbolic computation and generalized shallow water wave equation abstract we report that symbolic computation with the generalized tanh method leads to new soliton like solutions for a 2 1 dimensional generalization of the shallow water wave equations

new exact traveling wave solutions for the klein gordon zakharov equations based on the extended hyperbolic functions method we obtain the multiple exact explicit solutions of the klein gordon zakharov equations the solutions obtained in this paper include a the solitary wave solutions of bell type for u and n b the solitary wave solutions of kink type for u and bell type for n c the solitary wave solutions of a compound of the bell type and the kink type for u and n d the singular traveling wave solutions e periodic traveling wave solutions of triangle function types and solitary wave solutions of rational function types we not only rederive all known solutions of the klein gordon zakharov equations in a systematic way but also obtain several entirely new and more general solutions the variety of structures of the exact solutions of the klein gordon zakharov equations is illustrated

on the combinatorial problem of codes composed of two words resume nous montrons que si x est un code compose de deux mots x et y alors un mot de x suffisamment long admettant deux x interp etations disjointes est necessairement facteur d un mot de x ou de y ou de y ou d une puissance d un mot imprimitif appartenant a x y xy

traveling wave solutions for nonlinear equations using symbolic computation abstract in this paper a direct and unified algorithm for constructing multiple travelling wave solutions of nonlinear partial differential equations pdes is presented and implemented in a computer algebraic system the key idea of this method is to take full advantage of a riccati equation involving a parameter and use its solutions to replace the tanh function in the tanh method it is quite interesting that the sign of the parameter can be used to exactly judge the number and types of such travelling wave solutions in this way we can successfully recover the previously known solitary wave solutions that had been found by the tanh method and other more sophisticated methods more importantly for some equations with no extra effect we also find other new and more general solutions at the same time by introducing appropriate transformations our method is further extended to the nonlinear pdes whose balancing numbers may be any nonzero real numbers the efficiency of the method can be demonstrated on a large variety of nonlinear pdes such as those considered in this paper burgers huxley equation coupled korteweg de vries equation caudrey dodd gibbon kawada equation active dissipative dispersive media equation generalized fisher equation and nonlinear heat conduction equation

exact travelling wave solutions of nonlinear evolution equations in 1 1 and 2 1 dimensions abstract based upon the symbolic computation system maple the projective riccati equation method is improved to seek for travelling wave solutions in 1 1 and 2 1 dimensional nonlinear evolution equations by introducing two new elementary bell shaped and kink shaped functions the validity and reliability of the method is tested by applying it to the 2 1 dimensional generalized of the shallow water wave equation potential kdv equation and burgers kdv equation

low complexity blind equalization for ofdm systems with general constellations this paper proposes a low complexity algorithm for blind equalization of data in orthogonal frequency division multiplexing ofdm based wireless systems with general constellations the proposed algorithm is able to recover the transmitted data even when the channel changes on a symbol by symbol basis making it suitable for fast fading channels the proposed algorithm does not require any statistical information about the channel and thus does not suffer from latency normally associated with blind methods the paper demonstrates how to reduce the complexity of the algorithm which becomes especially low at high signal to noise ratio snr specifically it is shown that in the high snr regime the number of operations is of the order o ln where l is the cyclic prefix length and n is the total number of subcarriers simulation results confirm the favorable performance of the proposed algorithm

semi blind data detection for unitary space time modulation in mimo communications systems we propose an iterative algorithm based on expectation maximization em to jointly estimate the system parameters and decode the data in a mimo system using unitary space time block codes it is assumed that the receiver is unaware of the channel coefficients and their distribution the average energy of the received signal the prior probability of each signal in the constellation and the noise power the algorithm works for arbitrary modulation schemes and any channel model including rayleigh and rician fading the complexity of the proposed receiver is computed and it is shown to be significantly lower than previously published methods as it does not require any matrix inversion or trellis search the performance of the proposed receiver is evaluated by simulations in terms of symbol error rate ser vs signal to noise ratio snr and it is shown that with only a few iterations of the algorithm it achieves a performance close to that of the receiver which knows all the parameters

iterative maximum likelihood sequence estimation for space time coded systems in previous work on decoding space time codes it is either assumed that perfect channel state information csi is present or a channel estimate is obtained using pilot symbols and then used as if it were perfect to extract symbol estimates in the latter case a loss in performance is incurred since the resulting overall receiver is not optimal we look at maximum likelihood ml sequence estimation for space time coded systems without assuming csi the log likelihood function is presented for both quasi static and nonstatic fading channels and an expectation maximization em based algorithm is introduced for producing ml data estimates whose complexity is much smaller than a direct evaluation of the log likelihood function simulation results indicate the em based algorithm achieves a performance close to that of a receiver which knows the channel perfectly

superimposed training based noncoherent mimo systems the training based scheme constitutes an efficient method for noncoherent multiantenna communications in this paper we propose a superimposed training based linear dispersion stld transmission scheme where the transmitted symbols are superposition of the training pilots and the data symbols the stld system enjoys simple encoding and efficient suboptimal decoding since for noncoherent multiple input multiple output systems employing the stld scheme analytical expressions of block or bit error probabilities do not exist deterministic optimization methods cannot be used to design the optimal stld system we therefore propose to design the optimal stld systems using simulation based optimization techniques together with gradient estimation simulation results show that with either maximum likelihood or suboptimal decoding the stld systems obtained by the proposed design algorithm generally outperform the conventional training based scheme employing space time codes designed for coherent channels

new exact travelling wave solutions of two nonlinear physical models abstract in this paper an improved tanh function method is used with a computerized symbolic computation for constructing new exact travelling wave solutions on two nonlinear physical models namely the quantum zakharov equations and the 2 1 dimensional broer kaup kupershmidt bkk system the main idea of this method is to take full advantage of the riccati equation which has more new solutions the exact solutions are obtained which include new soliton like solutions trigonometric function solutions and rational solutions the method is straightforward and concise and its applications are promising

backlund transformation lax pairs and explicit exact solutions for the shallow water waves equation in this paper we consider the hirota satsuma equation for shallow water waves we first obtain the backlund transformation and lax pairs by using the extended homogeneous balance method then we find some explicit exact solutions by means of backlund transformation and the extended hyperbolic function method these solutions include the solitary wave solution of rational function soliton solutions double soliton solutions n soliton solutions the multiple solitary wave solutions singular solutions and the periodic wave solutions of triangle function type

noncoherent receivers for differential space time modulation in this paper noncoherent receivers for differential space time modulation dstm are investigated it is shown that the performance of the previously proposed conventional differential detection dd receiver is satisfactory only for very slow flat fading channels however conventional dd suffers from a considerable loss in performance even for moderately fast fading especially if more than one transmit antenna is used in order to overcome this problem two improved noncoherent receivers are considered the first one is the multiple symbol detection msd receiver because of the high computational complexity of msd also a low complexity decision feedback differential detection df dd receiver is derived analytical and simulation results confirm that both receivers perform equally well and can take full advantage of the enhanced diversity provided by multiple transmit antennas even for fast fading

data detection and kalman estimation for multiple space time trellis codes this work presents a joint channel estimation and data detection algorithm over high doppler fading channels for space time trellis codes sttcs having more than one code vector per trellis branch such codes are referred to as multiple sttcs msttcs this algorithm belongs to the per survivor processing psp family where a survivor sequence associated with a trellis state can be considered as the data sequence aiding per path channel estimation in a joint detection and estimation procedure we propose a smoothed data detection technique that utilizes past present and future received symbols to increase the probability of the survivor being a correct data sequence a symbol by symbol maximum a posteriori probability map criterion with a fixed delay d is employed for data detection combined with a kalman predictor kp for channel estimation this novel algorithm called smoothed data detection and kalman estimation sdd ke provides a significant performance gain when d 0 over d 0 with a linear increase in complexity when d increases comparison with the delayed mixture kalman filtering d mkf technique shows that the sdd ke algorithm provides important performance and complexity advantages

fano multiple symbol differential detectors for differential unitary space time modulation we present a class of suboptimal multiple symbol differential detectors msdds for differential unitary space time st codes in a time selective rayleigh flat fading channel these noncoherent detectors termed fano st msdds employ the well known fano algorithm as their decoding engines their bit error rate ber performance is excellent as there is no irreducible error floor even at very high fade rates compared with the sphere decoder which is optimal our best detector termed an on demand bi fano st msdd suffers only a 0 3 db degradation in power efficiency however its computational complexity as a function of the signal to noise ratio snr is consistently lower than that of the sphere decoder and does not experience the exponential growth in complexity in the latter when the snr decreases it can thus be concluded that the fano algorithm is a powerful detection strategy for differential st codes in fading channels our main contribution is in making the modifications and improvements to the fano algorithm that enables this realization the innovations include the bi fano edge bi fano and on demand bi fano search strategies as well as a new dynamic threshold adjustment scheme for avoiding unnecessary back and forth node evaluations during backtracking

sequence estimation in the presence of random parameters via the em algorithm the expectation maximization em algorithm was first introduced in the statistics literature as an iterative procedure that under some conditions produces maximum likelihood hit parameter estimates in this paper we investigate the application of the em algorithm to sequence estimation in the presence of random disturbances and additive white gaussian noise as examples of the use of the em algorithm we look at the random phase and fading channels and show that a formulation of the sequence estimation problem based on the em algorithm can provide a means of obtaining ml sequence estimates a task that has been previously too complex to perform