robust and ubiquitous on off intermittency in active coupling abstract on off intermittency is an aperiodic switching between synchronized dynamics and non synchronized chaotic dynamics intermittency is observed near the onset of chaos on a bifurcation diagram produced by varying the parameters of its coupling strength therefore its occurrence depends upon tuning the parameters of the system in a very sensitive way in the present paper a concept of observational heterarchy is reviewed with a simple model and characters of on off intermittency derived from active coupling systems acs are investigated generally on off intermittency results from fluctuation of the local transverse lyapunov exponent through points of marginal stability acs can retain such a character of the lyapunov exponent by the time evolution of the maps so on off intermittency occurs on wider parameter regions this paper presents a certain approach to the notion of robustness that is regarded as a persistent feature conceptually different from the strict notion of stability on dynamical systems

global attractivity for discrete models of nonautonomous logistic equations consider the following discrete model of a nonautonomous logistic equation n n 1 n n exp c n j 0mb j n n n j n 0 n 0 n 0 0andn j n j 0 1 j m where c n and b j n 0 j m n 0 are bounded and c n 0 b 0 n 0 b j n 0 1 j m n 0 in this paper using some kind of iterative method to the above equation we establish sufficient conditions that ensure the global attractivity for solutions the result is an extension of the former work k uesugi y muroya e ishiwata on the global attractivity for a logistic equation with piecewise constant arguments j math anal appl 294 2004 560 580 to the nonautonomous case

global attractivity of positive periodic solution to periodic lotka volterra competition systems with pure delay abstract we consider a periodic lotka volterra competition system without instantaneous negative feedbacks i e pure delay systems x i t x i t r i t j 1 n a i j t x j t i j t i 1 2 n we establish some 3 2 type criteria for global attractivity of a positive periodic solution of the system which generalize the well known wright s 3 2 criteria for the autonomous delay logistic equation and thereby address the open problem proposed by both kuang y kuang global stability in delayed nonautonomous lotka volterra type systems without saturated equilibria differential integral equations 9 1996 557 567 and teng z teng nonautonomous lotka volterra systems with delays j differential equations 179 2002 538 561

self organized criticality resulting from minimization of perpetual disequilibration abstract a bootstrapping system is proposed in order to describe nonlogical properties of living systems in which the velocity of observation propagation is finite a cellular automaton ca model of the system combines two logics which are the a priori non boolean logic and the a posteriori boolean logic because of inconsistency between the two logics the system evolves perpetually generating disequilibrium and perpetually equilibrating the generated disequilibrium the system tends to self organize to the border between order and disorder and shows critical behaviours as class iv ca although the critical behaviors of the two systems are similar the bootstrapping ssstem has twice stronger undecidability than class iv ca or edge of chaos dynamics it is stressed that real living systems are not computable and should be described by strongly undecidable systems

stochastic differential equation theory applied to wireless channels modeling wireless channels is essential to wireless communication systems an autoregressive ar process of order one for wireless channel has long been assumed but without a rigorous mathematical physical basis in this paper we derive a first order stochastic ar model for a flat stationary wireless channel which comes from stochastic differential equation sde theory concerning the nature of multipath fading channels the resulting ar model describes more of the origin of multipath fading channels than previous ar models and it can efficiently model and generate rayleigh distributed stationary fading channels the markovian property of the ar model is inherited through the sde approach

capacity analysis for finite state markov mapping of flat fading channels in this paper time varying flat fading channels are modeled as first order finite state markov channels fsmc the effect of this modeling on the channel information capacity is addressed the approximation accuracy of the first order memory assumption in the markov model is validated by comparing the fsmc capacity with the channel capacity assuming perfect state information at the receiver side the results indicate that the first order markovian assumption is accurate for normalized doppler frequencies f sub d t spl lsim 0 01 in amplitude only quantization of the channel gain for noncoherent binary signaling in phase only and joint phase and amplitude quantization of the channel gain for coherent binary signaling the first order markovian assumption is accurate for f sub d t spl lsim 0 001 furthermore the effect of channel quantization thresholds on the fsmc capacity is studied in high signal to noise ratio snr conditions nonuniform two level amplitude quantization scheme outperforms equiprobable quantization method by 0 8 1 5 db

global periodic solutions of a generalized n species gilpin ayala competition model abstract in this paper we investigate a generalized n species gilpin ayala competition system with several deviating arguments in periodic environment which is more general and more realistic than the classical lotka volterra competition systems by using the method of coincidence degree a set of easily verifiable sufficient conditions are derived for the existence of at least one strictly positive componentwise periodic solution some new results are obtained as applications we also apply our main results to some special cases of the system we consider here including the classical n species lotka volterra competition systems and n species gilpin ayala competition model which have been studied extensively in the literature some known results are improved and generalized the examples show that our criteria are new general and easily verifiable

permanence in nonautonomous lotka volterra system with predator prey the nonautonomous lotka volterra system with m predators and n preys is considered in this paper average conditions are obtained for permanence and global attractivity in the system it is shown that our results are generalization of those of the periodic system

spectrum sensing for cognitive radios in time variant flat fading channels a joint estimation approach most of the existing spectrum sensing schemes utilize only the statistical property of fading channels which unfortunately fails to cope with the time varying fading channel that has disastrous effects on sensing performance as a consequence such sensing schemes may not be applicable to distributed cognitive radio networks in this paper we develop a promising spectrum sensing algorithm for time variant flat fading tvff channels we first formulate a dynamic state space model dsm to characterize the evolution behaviors of two hidden states i e the primary user pu state and the fading gain by utilizing a two state markov process and another finite state markov chain respectively the summed energy which serves as the observation of dsm is employed for the ease of implementation relying on a bayesian statistical inference framework the sequential importance sampling based particle filtering is then exploited to numerically and recursively estimate the involved posterior probability and thus the pu state and the fading gain are jointly estimated in time the estimations of two states are soft outputs which are successively refined with a designed iterative approach simulation results demonstrate that the new scheme can significantly improve the sensing performance in tvff channels which in turn provides particular promise to realistic applications

adaptive training for correlated fading channels with feedback we consider data transmission through a time selective correlated first order markov rayleigh fading channel subject to an average power constraint the channel is estimated at the receiver with a pilot signal and the estimate is fed back to the transmitter the estimate is used for coherent demodulation and to adapt the data and pilot powers we derive the hamilton jacobi bellman hjb equation for the optimal policy in a continuous time limit where the channel state evolves as an ornstein uhlenbeck diffusion process and is estimated by a kalman filter at the receiver finding an explicit solution to the hjb equation as well as proving that a twice differentiable solution exists appears to be quite challenging however assuming that such a solution does exist we explicitly determine the optimal pilot and data power control policies the optimal pilot policy switches between zero and the maximum peak constrained value bang bang control and approximates the optimal discrete time policy at low signal to noise ratios snrs equivalently large bandwidths the switching boundary is defined in terms of the system state estimated channel mean and associated error variance and can be explicitly computed under the optimal policy the transmitter conserves power by decreasing the training power when the channel is faded thereby increasing the data rate numerical results show a significant increase in achievable rate due to the adaptive training scheme with feedback relative to constant nonadaptive training which does not require feedback the gain is more pronounced at relatively low snrs and with fast fading results are further verified through monte carlo simulations

lattice driven cellular automata implementing local semantics abstract we propose a model based on elementary cellular automata eca where each cell has its own semantics defined by a lattice semantics play the following two roles 1 a state space for computation and 2 a mediator generating and negotiating the discrepancy between the rule and the state we call semantics playing such roles local semantics a lattice is a mathematical structure with certain limits weakening the limits reveals local semantics firstly we implement local semantics for eca and call the result lattice driven cellular automata ldca in eca rules are common and invariant for all cells and uniquely determine the state changes whereas in ldca rules and states interplay with each other dynamically and directly in each cell secondly we compare the space time patterns of ldca with those of eca with respect to the relationship between the mean value and variance of the input entropy the comparison reveals that ldca generate complex patterns more universally than eca lastly we discuss the observation that the direct interplay between levels yields wholeness dynamically

almost periodic solutions of n species competitive system with feedback controls abstract in this paper the following almost periodic n species competitive system with feedback controls x i t x i t b i t j 1 n a ij t x j t j 1 j i n c ij t x i t x j t d i t u i t u i t r i t e i t u i t f i t x i t i 1 2 n are studied by using the comparison theorem and constructing suitable lyapunov function where some important factors such as the effect of toxic and the age structure are also considered simultaneously some sufficient conditions are obtained for the existence of a unique almost periodic solution of above model examples show that the obtained criteria are new general and easily verifiable

global attractivity of an almost periodic n species nonlinear ecological competitive model abstract by using comparison theorem and constructing suitable lyapunov functional we study the following almost periodic nonlinear n species competitive lotka volterra model x i t x i t r i t j 1 n a i j t x j i j t j 1 n b i j t x j i j t i j t j 1 n c i j t x i i i t x j i j t a set of sufficient conditions is obtained for the existence and global attractivity of a unique positive almost periodic solution of the above model as applications some special competition models are studied again our new results improve and generalize former results examples and their simulations show the feasibility of our main results

the origin of universality making and invalidating a free category we propose a model of evolutionary systems characterized by internal measurement or endo physics that is based on a particular graph morphism if we take an internal stance we have to focus on the influence of the outside of the domain of choice the outside of the domain is not explicitly expressed as a particular ensemble in advance although a formal expression generally requires an explicit form of the outside as the possible forms in our model a system is expressed by a directed graph and the time transition is expressed as a particular graph morphism referring to the outside of the domain of the morphism referring to the outside of the domain is expressed by dynamical decomposition and synthesis of the relationship between a graph and its possible forms expressed as an underlying free category because the transformations from a graph to a category and vice versa are expressed as two adjunctive functors a graph morphism is defined by a sequence of the operation of a free functor and a special operator standing for invalidation of the operation of the free functor time development of this system can generate a particular universal structure like a limit and co limit as a part of a directed graph which stands for generation of a higher order we also argue that the process toward the generation of a universal structure can reveal intermittency and that an emergent boundary in pattern formation can be demonstrated by the generation of this universal structure in addition we discuss emergent computation such as the origin of primitive recursive functions through the origination of a universal structure

limited feedback for temporally correlated mimo channels with other cell interference limited feedback improves link reliability with a small amount of feedback from the receiver to the transmitter in cellular systems the performance of limited feedback will be degraded in the presence of other cell interference when the base stations have limited or no coordination this paper establishes the degradation in sum rate of users in a cellular system due to uncoordinated other cell interference and feedback delay a goodput metric is defined as the rate when the bits are successfully received at the mobile station and used to derive an upper bound on the performance of limited feedback systems with delay this paper shows that the goodput gained from having delayed limited feedback decreases doubly exponentially as the delay increases the analysis is extended to precoded spatial multiplexing systems where it is shown that the same upper bound can be used to evaluate the decay in the achievable sum rate to reduce the effects of interference zero forcing interference nulling is applied at the receiver where it is shown that the effect of the interference on the achievable sum rate can be suppressed by nulling out the interferer numerical results show that the decay rate of the goodput decreases when the codebook quantization size increases and when the doppler shift in the channel decreases

new contractivity condition in a population model with piecewise constant arguments abstract in this paper we improve contractivity conditions of solutions for the positive equilibrium n 1 a i 0 m b i of the following differential equation with piecewise constant arguments d n t d t n t r t 1 a n t i 0 m b i n n i n t n 1 n 0 1 2 n 0 n 0 0 and n j n j 0 j 1 2 m where r t is a nonnegative continuous function on 0 r t 0 i 0 m b i 0 b i 0 i 0 1 2 m and a b 0 i 1 m b i in particular for the case a 0 and m 1 we really improve the known three type conditions of the contractivity for solutions of this model see for example y muroya a sufficient condition on global stability in a logistic equation with piecewise constant arguments hokkaido math j 32 2003 75 83 for the other case a 0 and m 1 under the condition j 1 m b j 2 b 0 a j 1 m b j 1 b 0 j 0 m b j the obtained result partially improves the known results on the contractivity of solutions for the positive equilibrium of this model given by the author y muroya persistence contractivity and global stability in logistic equations with piecewise constant delays j math anal appl 270 2002 602 635 and others

existence and global attractivity of an almost periodic ecological model the almost periodic lotka volterra model with m predators and n preys is considered in this paper by constructing suitable lyapunov function some sufficient conditions are obtained for the existence and global attractivity of a unique positive almost periodic solution of this model examples show that our criteria are new general and easily verifiable

on a periodic multi species ecological model a periodic predator prey model with m predators and n preys is proposed in this paper which can be seen as the modification of the traditional lotka volterra model by using comparison theorem the ultimately bounded region of the system is obtained by using comparison theorem and brouwer fixed point theorem sufficient conditions with guarantee the existence of a positive periodic solution of the system is obtained finally by constructing a suitable lyapunov function some sufficient conditions are obtained for the existence of a unique globally attractive periodic solution of system the results obtained here generalized the main results of j d zhao w c chen global asymptotic stability of a periodic ecological model applied mathematics and computation 147 3 2004 881 892

permanence criteria for general delayed discrete nonautonomous n species kolmogorov systems and its applications in this paper the permanence for the general nonautonomous n species discrete kolmogorov systems with delays is studied by using the method of multiple discrete lyapunov like functionals a quite general sufficient condition is established as application of this result new sufficient conditions are obtained to ensure the permanence of all species for the discrete nonautonomous pure delayed n species lotka volterra competitive systems and food chain systems particularly as special cases a series of new sufficient conditions on the permanence for the discrete nonautonomous pure delayed lotka volterra two species competitive systems predator prey systems and three species food chain systems and the discrete autonomous pure delayed lotka volterra competition systems and food chain systems are obtained

autonomic life as the proof of incompleteness and lawvere s theorem of fixed point abstract if finite velocity of observation propagation is taken into consideration one is faced with a paradox or infinite regression in his own logic it is the same as goedel s theorem of incompleteness or wittgenstein s paradox and in general it can be formally replaced by lawvere s theorem of a fixed point to describe time evolution under finite velocity of observation propagation is not to construct a new logic in which the paradox can be removed or improved but to accept the paradox itself given a system in which a paradox is deduced by taking the finite velocity of observation propagation we can regard the whole formal description which consists of the system and a proof sequence toward the paradox as an evolutionary system a formal evolutionary system defined here is one demonstration of autonomic life

positive almost periodic solutions of a class of lotka volterra type competitive system with delays and feedback controls abstract in this paper we study the positive almost periodic solutions for a class of almost periodic lotka volterra type system with delays and feedback controls applying schauder s fixed point theorem a criterion on the existence of the positive almost periodic solution of the system is obtained our new criterion which improves and generalizes some well known results can be easily checked

dynamically changing interface as a model of measurement in complex systems abstract we propose and sketch a novel approach toward the study of complex systems by considering a basic type of measurement problem hidden in any system we call this approach hyper dilation and cover it under the label of measurement oriented physics mop as compared with state oriented physics sop the essential difference between the two concerns the concepts of state to which they refer mop deals with two different concepts of state non measured states with infinite precision and measured states with finite precision the measurement process is expressed as a dynamically changing interface between them sop deals with one single concept of state and does not comprise a corresponding distinction we show fundamental differences between mop and sop with respect to the noise characteristics of complex systems around critical states mop can give rise to exact and universal 1 noise while sop shows 1 noise with 1 in general in mop a self similar return map can be degenerate with a cantor set rendering a solution for a basic measurement paradox the significance of this degeneracy as a model for emergent properties is discussed

infinite series representations of the bivariate rayleigh and nakagami m distributions despite the usefulness of the bivariate correlated nakagami m cumulative distribution function cdf in communications systems analysis an infinite series for the computation of this function is not known in this letter an infinite series representation of the bivariate cdf is derived bounds on the error resulting from truncation of the infinite series are also derived

on the multivariate nakagami m distribution with exponential correlation capitalizing on the proof of a theorem presented by l e blumenson and k s miller see ann math statist vol 34 p 903 10 1963 we propose a useful closed formula for the exponentially correlated n variate nakagami m probability density function moreover an infinite series approach for the corresponding cumulative distribution function is presented bounds on the error resulting from the truncation of the infinite series are also derived finally in order to check the accuracy of the proposed formulation numerical results are presented

a different consideraton about the globally asymptotically stable solution of the periodic n competing species problem abstract we consider the volterra lotka equations for n competing species n 2 in which the right hand sides are periodic in time we show that conditions given by k gopalsamy j austral math soc ser b 27 1985 66 72 which imply the existence of a periodic solution with positive components also imply the uniqueness and asymptotic stability of the solution

persistence and global stability in discrete models of lotka volterra type abstract in this paper we establish new sufficient conditions for global asymptotic stability of the positive equilibrium in the following discrete models of lotka volterra type n i p 1 n i p exp c i a i n i p j 1 n a i j n j p k i j p 0 1 i n n i p n i p 0 p 0 and n i 0 0 1 i n where each n i p for p 0 each c i a i and a i j are finite and a i 0 a i a i i 0 1 i n and k i j 0 1 i j n applying the former results y muroya persistence and global stability for discrete models of nonautonomous lotka volterra type j math anal appl 273 2002 492 511 on sufficient conditions for the persistence of nonautonomous discrete lotka volterra systems we first obtain conditions for the persistence of the above autonomous system and extending a similar technique to use a nonnegative lyapunov like function offered by y saito t hara and w ma y saito t hara w ma necessary and sufficient conditions for permanence and global stability of a lotka volterra system with two delays j math anal appl 236 1999 534 556 for n 2 to the above system for n 2 we establish new conditions for global asymptotic stability of the positive equilibrium in some special cases that k i j k j j 1 i j n and j 1 n a j i a j k 0 i k these conditions become a i j 1 n a j i 2 1 i n and improve the well known stability conditions a i j 1 n a j i 1 i n obtained by k gopalsamy k gopalsamy global asymptotic stability in volterra s population systems j math biol 19 1984 157 168

formal model of internal measurement alternate changing between recursive definition and domain equation abstract we sketch a paradox generally resulting from recursivity and propose a novel model to express evolutionary processes that requires identification of an interaction with internal measurement in this model a paradox is not resolved and the notion of relativity of any resolution is implicit in a dynamical system a certain transition rule is used recursively along time if one takes the foundation or context of recursivity into consideration one obtains a fixed point or one confronts a paradox in order to resolve this paradox we adopt scott s technical way to identify the form of a fixed point with a domain equation and to obtain a reflective domain however we simultaneously show that any resolution is destined to be relative in utilizing this notion we construct a model of dynamical process by embedding a measurement process in one time step any time transition involves the process of doubting the foundation of a transition rule leading to a fixed point solving it and obtaining a reflexive domain is used as a new transition rule also this process perpetually proceeds along time and then the system perpetually proceeds while any solution is destined to be relative we illustrate this type of model by using a dynamically changing contraction mapping as the interface of state and transition rule finally we show that one can formalize emergent properties by using this model and discuss the relationship between endo physics and internal measurement

observational heterarchy enhancing active coupling heterarchy and the agent of self organization are ones of most challengeable topics in complex systems when the notion of heterarchy is generalized and dilated to general phenomena and is replaced by observational heterarchy the agent of self organization i e internal observer carrying measurement is found even in non hierarchical system a usual dynamics in the sense of complex system is articulated into two kinds of dynamics intent and extent dynamics and the interaction between them where intent corresponds to an attribute to a given phenomenon and extent corresponds to a collection of objects satisfying the phenomenon we formalize observational heterarchy by introducing pre equivalence pre adjunction between intent and extent and apply it to a coupled map system since the model inherits evoluvability of dynamics we call it active coupling to distinguish usual passive coupling from it we show that perturbation can modify the dynamics itself and enhance robust behavior opened to emergence in the system of active coupling and discuss the significance of observational heterarchy in complex systems

average conditions for kolmogorov systems in this paper we consider nonautonomous competitive kolmogorov systems which is a generalization of classical lotka volterra competition model applying ahmad and lazer s definitions of lower and upper averages of a function we give the average conditions for the persistence permanence and global attractivity of the system

permanence and asymptotic behavior of the n species nonautonomous lotka volterra competitive systems abstract in this paper we study the permanence and global asymptotic behavior for the n species nonautonomous lotka volterra competitive systems where all the parameters are time dependent and asymptotically approach periodic functions respectively some new criteria are established the corresponding results given by peng and chen in 1 are improved and extended

persistence and global stability for discrete models of nonautonomous lotka volterra type abstract consider the following discrete models of nonautonomous lotka volterra type n i p 1 n i p exp c i p a i p n i p j 1 n l 0 m a ij l p n j p k l 1 i n p 0 1 2 n i p n ip 0 p 0 and n i0 0 1 i n where each c i p a i p and a ij l p are bounded for p 0 and inf p 0 a i p 0 a ii 0 p 0 1 i n a ij l p 0 1 i j n 0 l m k 0 0 integers k l 0 1 l m in this paper to the above discrete system we apply the techniques offered by ahmad and lazer nonlinear anal 40 2000 37 49 and establish similar conditions of the persistence and global asymptotic stability of the system

on first order markov modeling for the rayleigh fading channel previous models for the received signal amplitude of the flat fading channel that use first order finite state markov chains are examined the stochastic properties of a proposed first order model based on these models are examined the limitations of using an information theoretic metric which is sometimes used to justify a first order markov chain as a sufficient model for very slowly fading channels are discussed a simple method of qualitatively comparing autocorrelation functions is instead proposed the usefulness of the first order markov chain in representing the flat fading channel is examined by looking at two specific problems in wireless system applications that represent two disparate cases the first case involves analysis over a short duration of time relative to the inverse of the normalized doppler frequency while the second involves analysis over a long duration of time contrary to previous reports the results indicate that first order markov chains are not generally suitable for very slowly fading channels rather first order markov chains can be suitable for very slowly fading applications which require analysis over only a short duration of time

coexistence states for periodic competitive kolmogorov systems abstract we prove the existence of positive periodic solutions for a class of nonautonomous competitive periodic kolmogorov systems which generalize the may leonard model a necessary and sufficient condition is also obtained

principles of biological organization local global negotiation based on material cause organization of living things is characterized by dynamical hierarchical structures inheriting discrepancy among levels it can be expressed as a system consisting of two layers the microscopic perspective extent defined by a collection of elements and the macroscopic perspective intent defined by the property as a whole and the interplay between them first we show that if the microscopic and macroscopic perspectives are consistent with each other an ideal case then the operation between the two layers can be expressed as a sheaf between a lattice and a quotient lattice where a sheaf is a mathematical operation representing the gluing process second we introduce an observer who cannot look out over the whole world and this reveals a discrepancy between the two layers third we introduce a new mathematical construction called skeleton that is derived by the sheaf operation the skeleton reduces the discrepancy between the micro and macroscopic perspectives and that reveals the perpetual transition between the perspectives this process yields a basic framework of biological organizations finally we argue that the skeleton mediating between the two levels is a particular expression for the material cause

on a model of competition in periodic environments abstract sufficient conditions are obtained for the existence and global attractivity of a positive periodic solution of the system x i n 1 b i n x i n 1 j 1 m c ij n x j n i 1 2 m n n in which bi n cij n i j 1 2 m n n denote positive periodic sequences with a common period also a method is proposed for the derivation of the discrete system from a continuous time analogue modelling competition in periodic environments with time delays in the stabilizing negative feedback effects

performance analysis of likelihood based multiple access for detection over fading channels in this paper we consider the binary hypothesis testing problem using wireless sensor networks we analyze the case where sensors transmit their local log likelihood ratio llr directly to a fusion center fc using an analog transmission scheme over multiple access fading channels due to the nature of the wireless medium the fc receives a superposition of sensor transmissions the decision is made by the fc and is based on received data from the sensors in contrast to the case of identical channels and i i d observations the analog transmission of the llr over multiple access fading channels does not achieve the centralized error exponent large deviation tools are used in this paper to characterize the error exponent in the asymptotic regime when the number of sensors approaches infinity in the case of non i i d observations and non i i d fading channels chernoff bounding techniques are used to provide bounds on the error probability for a finite number of sensors when the observations and the fading channels are independent across sensors specific performance analysis is provided for detection over both i i d and spatially correlated markovian fading channels simulation results then illustrate the detector s performance

a binary communication channel with memory based on a finite queue a model for a binary additive noise communication channel with memory is introduced the channel noise process which is generated according to a ball sampling mechanism involving a queue of finite length m is a stationary ergodic mth order markov source the channel properties are analyzed and several of its statistical and information theoretical quantities e g block transition distribution autocorrelation function acf capacity and error exponent are derived in either closed or easily computable form in terms of its four parameters the capacity of the queue based channel qbc is also analytically and numerically compared for a variety of channel conditions with the capacity of other binary models such as the well known gilbert elliott channel gec the fritchman channel and the finite memory contagion channel we also investigate the modeling of the traditional gec using this qbc model the qbc parameters are estimated by minimizing the kullback leibler divergence rate between the probability of noise sequences generated by the gec and the qbc while maintaining identical bit error rates ber and correlation coefficients the accuracy of fitting the gec via the qbc is evaluated in terms of acf channel capacity and error exponent numerical results indicate that the qbc provides a good approximation of the gec for various channel conditions it thus offers an interesting alternative to the gec while remaining mathematically tractable

limited feedback beamforming over temporally correlated channels feedback of quantized channel state information csi called limited feedback enables transmit beamforming in multiple input multiple output mimo wireless systems with a small amount of overhead due to its efficiency beamforming with limited feedback has been adopted in several wireless communication standards prior work on limited feedback commonly adopts the block fading channel model where temporal correlation in wireless channels is neglected in this paper we consider temporally correlated channels and design single user transmit beamforming with limited feedback analytical results concerning csi feedback are derived by modeling quantized csi as a first order finite state markov chain these results include the information rate of the csi quantizer output the bit rate a csi feedback channel is required to support and the effect of feedback delay on throughput in particular based on the theory of markov chain convergence rate feedback delay is proved to reduce the throughput gain due to csi feedback at least exponentially furthermore an algorithm is proposed for csi feedback compression in time combining the results in this work leads to a new method for designing limited feedback beamforming as demonstrated by a design example

global asymptotic stability of a periodic ecological model the periodic lotka volterra model with m predators and n preys is considered in this paper under the suppose that the intrinsic growth rate of the prey species may be negative while the total intrinsic growth rate in a period are positive sufficient conditions are obtained for existence and global asymptotic stability of the periodic solution of this model

global stability of discrete population models with time delays and fluctuating environment the global stability of a discrete population model of volterra type is studied the model incorporates time delays and allows for a fluctuating environment by linearization of the model at positive solutions and construction of liapunov functionals sufficient conditions are obtained to ensure a positive solution of the model is stable and attracts all positive solutions

dynamic behaviors of a delay differential equation model of plankton allelopathy in this paper we consider a modified delay differential equation model of the growth of n species of plankton having competitive and allelopathic effects on each other we first obtain the sufficient conditions which guarantee the permanence of the system as a corollary for periodic case we obtain a set of delay dependent condition which ensures the existence of at least one positive periodic solution of the system after that by means of a suitable lyapunov functional sufficient conditions are derived for the global attractivity of the system for the two dimensional case under some suitable assumptions we prove that one of the components will be driven to extinction while the other will stabilize at a certain solution of a logistic equation examples show the feasibility of the main results

on the global attractivity for a logistic equation with piecewise constant arguments in this paper we consider the following logistic equation with piecewise constant arguments dn t dt rn t 1 j 0majn t j t 0 m 1 n 0 n0 0 n j n j 0 j 1 2 m where r 0 a0 a1 am 0 j 0maj 0 and x means the maximal integer not greater than x the sequence nn n 0 where nn n n n 0 1 2 satisfies the difference equation nn 1 nnexpr1 j 0majnn j n 0 1 2 under the condition that the first term a0 dominates the other m coefficients ai 1 i m we establish new sufficient conditions of the global asymptotic stability for the positive equilibrium n 1 j 0maj

new conditions on the existence and stability of periodic solution in lotka volterra s population system in this paper we revisit the famous periodic lotka volterra competitive system some new and interesting sufficient conditions are obtained to guarantee the existence and global asymptotic stability of the periodic solution in the lotka volterra competitive system our method is based on mawhin s coincidence degree matrix s spectral theory and some new estimation techniques for the priori bounds of unknown solutions to the equation lx lambda nx due to this new method our new results are much different from the known results in the previous literature finally some examples and their simulations show the feasibility of our results

extinction and permanence in nonautonomous competitive system with stage structure in this paper the n species nonautonomous stage structured competitive system is constructed and considered sufficient conditions for its extinction and permanence are obtained results here generalize and unify some previous ones moreover it is concluded that stage structure in this system is one of the important factors that effect the extinction and permanence of species

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

a necessary and sufficient condition for permanence of a lotka volterra discrete system with delays abstract in this paper we consider the permanence of the following lotka volterra discrete competition system with delays k1 k2 l1 and l2 x n 1 x n exp r1 1 x n k1 1y n k2 y n 1 y n exp r2 1 2x n l1 y n l2 we show the system is permanent for all nonnegative integers k1 k2 l1 and l2 if and only if 1

existence uniqueness and stability of positive periodic solution for a nonlinear prey competition model with delays a nonlinear periodic predator prey model with m preys and n m predators and delays is proposed in this paper which can be seen as the modification of the traditional lotka volterra prey competition model sufficient conditions which guarantee the existence of a unique globally attractive positive periodic solution of the system are obtained

persistence and global stability in discrete models of pure delay nonautonomous lotka volterra type abstract consider the persistence and the global asymptotic stability of the following discrete model of pure delay nonautonomous lotka volterra type n i p 1 n i p exp c i p j 1 n l 0 m a ij l p n j p k l p 0 1 2 1 i n n i p n i p 0 p 0 and n i 0 0 1 i n where each ci p and aijl p are bounded for p 0 and inf p 0 l 0 m a ii l p 0 a ij l p 0 i j n 1 i n and k l 0 1 l m in this paper for the above discrete system of pure delay type by improving the former work j math anal appl 273 2002 492 511 which extended the averaged condition offered by s ahmad and a c lazer nonlinear anal 40 2000 37 49 we offer conditions of persistence and considering a lyapunov like discrete function to the above discrete system we establish sufficient conditions of global asymptotic stability

markov characterization of channels with soft decision outputs it is shown that a methodology based on hidden markov models is applicable to the modeling of slowly varying rayleigh fading channels with additive gaussian noise and soft decision outputs the fading is considered to be frequency nonselective and ideal demodulation is considered throughout to prove the validity of robustness of the modeling technique various results that show good agreement between the simulated channels and the models found are presented two soft decision statistical distributions namely the soft burst and soft burst interval distributions are defined and compared to illustrate the accuracy of the models obtained the simulation and model outputs are compared for a convolutional encoder with viterbi decoding and various degrees of interleaving