error probability bounds and approximations for ds spread spectrum communication systems with mutiple tone or multiple access interference upper and lower bounds on the average probability of error of direct sequence ds spread spectrum communication systems operating in the presence of either multiple tone or multiple access interference are presented the bounds are quite tight and can be used without the restriction that the peak level of the interference be less than the desired signal level a simple method for evaluating approximations to the bounds for multiple access systems in which the peak interference does indeed exceed the desired signal level is presented as well the tightness of both the bounds and the approximations are illustrated with numerical results

minimum probability of error for asynchronous gaussian multiple access channels consider a gaussian multiple access channel shared by k users who transmit asynchronously independent data streams by modulating a set of assigned signal waveforms the uncoded probability of error achievable by optimum multiuser detectors is investigated it is shown that the k user maximum likelihood sequence detector consists of a bank of single user matched filters followed by a viterbi algorithm whose complexity per binary decision is o 2 k the upper bound analysis of this detector follows an approach based on the decomposition of error sequences the issues of convergence and tightness of the bounds are examined and it is shown that the minimum multiuser error probability is equivalent in the iow noise region to that of a single user system with reduced power these results show that the proposed multiuser detectors afford important performance gains over conventional single user systems in which the signal constellation carries the entire burden of complexity required to achieve a given performance level

dehn surgery on arborescent links this paper studies dehn surgery on a large class of links called arborescent links it will be shown that if an arborescent link l is sufficiently complicated in the sense that it is composed of at least 4 rational tangles t pl qi with all qj 2 and none of its length 2 tangles are of the form t 1 2ql 1 2q2 then all complete surgeries on l produce haken manifolds the proof needs some result on surgery on knots in tangle spaces let t r 2s p 2q b ti u t2 li k be a tangle with k a closed circle and let m b int n ti u t2 we will show that if s 1 and p 1 mod 2q then om remains incompressible after all nontrivial surgeries oln k two bridge links are a subclass of arborescent links for such a link l p q most dehn surgeries on it are non haken however it will be shown that all complete surgeries yield manifolds containing essential laminations unless p q has a partial fraction decomposition of the form 1 r 1 s in which case it does admit non laminar surgeries

some kinds of view the fuzzy filters of bl algebras the concepts of view the mathml source fuzzy implicative positive implicative and fantastic filters of bl algebras are introduced and some related properties are investigated some characterizations of these generalized fuzzy filters are derived in particular we describe the relationships among ordinary fuzzy implicative positive implicative and fantastic filters view the mathml source fuzzy implicative positive implicative and fantastic filters and view the mathml source fuzzy implicative positive implicative and fantastic filters of bl algebras finally we prove that a fuzzy set f of a bl algebra l is an view the mathml source fuzzy implicative filter of l if and only if it is both an view the mathml source fuzzy positive implicative filter and an view the mathml source fuzzy fantastic filter

partial correlation effects in direct sequence spread spectrum multiple access communication systems nearly all previous analytical results on the performance of direct sequence spread spectrum multiple access ds ssma communication systems are restricted to systems in which the period p of the signature sequence is equal to the number n of chips per data symbol in many applications however it is necessary to employ signature sequences whose period p is much larger than n thus successive n chip segments of the signature sequence are used to phase code the carrier during the transmission of successive data symbols the performance of such systems depends on the partial correlation properties of the signature sequences rather than the aperiodic correlation properties as in the case when n p in this paper we consider the performance of a ds ssma system for arbitrary values of p and n as special cases of our results we delermine the effects of partial correlation in three classes of systems those for which n p those for which n and p are relatively prime and those for which n is a divisor of p we also provide two methods for the design of sequences for systems for which n is a divisor of p

error probability for direct sequence spread spectrum multiple access communications part i upper and lower bounds upper and lower bounds on the average probability of error are obtained for direct sequence spread spectrum multipleaccess communications systems with additive white gaussian noise channels the bounds which are developed from convexity properties of the error probability function are valid for systems in which the maximum multiple access interference does not exceed the desired signal and the signature sequence period is equal to the duration of the data pulse the tightness of the bounds is examined for systems with a small number of simultaneously active transmitters this is accomplished by comparisons of the upper and lower bounds for several values of the system parameters the bounds are also compared with an approximation based on the signal to noise ratio and with the chernoff upper bound

fuzzy groups some group theoretic analogs abstract we introduce the concepts of 1 order of a fuzzy subgroup of a finite group 2 a fuzzy abelian group and 3 a fuzzy solvable group we obtain some results involving these notions which are analogs of results from group theory also we prove analogs of two basic theorems of group theory namely cayley s theorem and lagrange s theorem

fuzzy normal subgroups and fuzzy cosets abstract we introduce here the notion of 1 i a fuzzy normal subgroup and 2 ii a fuzzy coset we prove that for a group g a fuzzy subgroup is fuzzy normal if and only if it is constant on the conjugate classes of g further we show that the level subgroups of a fuzzy normal subgroup are all normal we obtain several results which are analogs of some basic theorems of group theory in particular a fuzzy version of lagrange s theorem is established

bit error rate evaluation for spread spectrum multiple access systems a unified method for approximating and bounding the average bit error probability for spread spectrum multiple access communication systems is presented various forms of direct sequence spreadspectrum modulation are considered including binary phase shift keying quadriphase shift keying and minimum shift keying the analysis of the multiple access interference makes use of a number of moments sufficent to evaluate the error probability with a high degree of accuracy a computationally efficient algorithm for computing the moments is also given the subsequent transformation from the moments to the average bit error probability is carried out by means of gauss type numerical integration formulas it is shown that the same approach can be exploited for evaluating two classes of upper and lower bounds on the bit error rate finally some results and comparisons are reported

a contribution to the theory of fuzzy subgroups abstract in this paper we continue our study in order to give a partial answer to the question suggested by asaad in 1991 what can be said about the structure of a group g when the information are known about the structure of a fuzzy subgroup a of g and viceversa

fuzzy h v ideals in γ h v rings in this paper by means of a kind of new idea we consider the q fuzzy h v ideals of a c h v ring the concept of c h v rings which is a generalization of c rings and h v rings is introduced the notion of q fuzzy h v ideals of a c h v ring is provided and some related properties are investigated the concept of implication based fuzzy h v ideals of a c h v ring is studied in particular the implication operators in the lukasiewicz system of continuous valued logic are discussed finally the homomorphism of q fuzzy h v ideals of a c h v ring is explored

performance bounds for ds ssma communications with complex signature sequences a unified performance analysis of direct sequence spread spectrum multiple access ds ssma communications with deterministic complex signature sequences is presented the probability density function pdf of the multiple user interference is determined using a round down and round up procedure on the pdf arbitrarily tight lower and upper bounds on the probability of bit error pbe are obtained results based on the gaussian approximation method are also presented it is shown that complex sequences can yield better pbe performance than binary sequences using complex sequences the number of signature sequences that have good auto and cross correlation properties is greatly enlarged new users employing complex or binary signature sequences can be added to existing systems with graceful performance degradation

e e v q fuzzy normal quasinormal and maximal subgroups abstract the notions of and q fuzzy normality and quasinormality for a q fuzzy subgroup are introduced the notions of an q fuzzy core subgroup and an q fuzzy p sylow subgroup are also introduced and some fundamental properties are dealt with q fuzzy normality and q fuzzy quasinormality are found to be more generalised concepts than those introduced by others a detailed study with a fuzzy maximal subgroup is incorporated with the limitation of this concept

generalizations of fuzzy subalgebras in bck bci algebras more general form of the notion of quasi coincidence of a fuzzy point with a fuzzy set is considered and generalizations of results in the papers y b jun on a b fuzzy subalgebras of bck bci algebras bull korean math soc 42 4 2005 703 711 y b jun fuzzy subalgebras of type a b in bck bci algebras kyungpook math j 47 2007 403 410 are discussed the notions of q k fuzzy subalgebras and email protected q k fuzzy subalgebras in a bck bci algebra x are introduced and several properties are investigated characterizations of email protected q k fuzzy subalgebra in a bck bci algebra x are discussed

unlinking via simultaneous crossing changes given two distinct crossings of a knot or link projection we consider the question under what conditions can we obtain the unlink by changing both crossings simultaneously more generally for which simultaneous twistings at the crossings is the genus reduced though several examples show that the answer must be complicated they also suggest the correct necessary conditions on the twisting numbers let l be an oriented link in s3with a generic projection onto the plane r let a be a short arc in r2 transverse to both strands of l at a crossing so that the strands pass through a in opposite directions then the inverse image of a contains a disk punctured twice with opposite orientation by l define a crossing disk d for a link l in s3 to be a disk which intersects l in precisely two points of opposite orientation it is easy to see that any crossing disk arises in the manner described twisting the link q times as it passes through d is equivalent to doing llq surgery on dd in s3 and adds 29 crossings to this projection of l we say that this new link l q is obtained by adding q twists at d call dd a crossing circle for l a crossing disk d and its boundary do are essential if dd bounds no disk disjoint from l this is equivalent to the requirement that l cannot be isotoped off d in s3 od here we examine how a link can be turned into the unlink via simultaneous twists on disjoint crossing disks in particular we prove an analogue for pairs of crossing disks of the following theorem a much more general version of which is proven in st 1 41 see also gal

generalized discrete fourier transform with nonlinear phase constant modulus transforms like discrete fourier transform dft walsh transform and gold codes have been successfully used over several decades in several engineering applications including discrete multi tone dmt orthogonal frequency division multiplexing ofdm and code division multiple access cdma communications systems in this paper we present a generalized framework for dft called generalized dft gdft with nonlinear phase by exploiting the phase space we show that gdft offers sizable correlation improvements over dft walsh oppermann and gold codes leading to better performance in all multi carrier communications scenarios investigated we also highlight how known constant modulus orthogonal transforms are special solutions of the proposed gdft framework moreover we introduce practical design methods offering computationally efficient implementations of gdft as enhancements to dft we conclude the paper with examples of communications applications where gdft is shown to outperform dft and other known constant modulus bases

a new view of fuzzy hypernear rings in this survey article we first introduce the concept of quasi coincidence of a fuzzy interval value with an interval valued fuzzy set this concept is a generalized concept of quasi coincidence of a fuzzy point within a fuzzy set by using this new idea we consider the interval valued q fuzzy sub hypernear rings hyperideals of a hypernear ring and hence a generalization of a fuzzy sub near ring ideal is given some related properties of fuzzy hypernear rings are described finally we consider the concept of implication based interval valued fuzzy sub hypernear rings hyperideals in a hypernear ring in particular the implication operators in lukasiewicz system of continuous valued logic are discussed

some types of generalized fuzzy filters of bl algebras the aim of this paper is to introduce the notions of interval valued q fuzzy boolean implicative positive implicative and fantastic filters in bl algebras and to investigate some related properties some characterizations of these generalized fuzzy filters are derived finally the relations among these generalized fuzzy filters are discussed it is proved that an interval valued q fuzzy filter in bl algebras is an interval valued q fuzzy boolean implicative filter if and only if it is both an interval valued q fuzzy positive implicative filter and an interval valued q fuzzy fantastic filter

interference modeling in a direct sequence spread spectrum packet radio network a technique for characterizing multiuser interference and background noise in a direct sequence spread spectrum network is introduced and packet error probabilities are calculated the multiuser interference over a packet in the network is modeled as a compound gaussian multivariate random variable for moderate to large values of the processing gain the conditional variance is dependent on the number of users and their interference powers the method works for any interference with statistics of the block interference having a spherically symmetric distribution the best performance results in terms of the expected total interference power are obtained for the case of a large number of interferers with comparable interference powers as the number of interferers approaches infinity the performance is the same as that for gaussian noise for a small number of interferers the block error probability curve is broader than that for gaussian noise for small values of snr the probability of error is smaller than that corresponding to gaussian noise and for large values of snr it is larger modifications to the basic direct sequence scheme that improve performance in the case of one strong interferer are suggested

generalized fuzzy h bi ideals and h quasi ideals of hemirings a new kind of generalized fuzzy h ideals of a hemiring namely the set membership variant set membership variantlogical orq fuzzy h bi ideal resp h quasi ideal is studied and the relationships between these generalized fuzzy h ideals are described some characterization theorems of prime and semiprime set membership variant set membership variantlogical orq fuzzy h bi ideals resp h quasi ideals of a hemiring are also given in particular we show that the h hemiregular hemirings and h intra hemiregular hemirings can be described by using some of their generalized fuzzy h ideals finally the implication based fuzzy h bi ideals resp h quasi ideals of a hemiring are considered

characterizations of hemirings by νq k fuzzy ideals in this paper we define q k fuzzy h sub hemirings q k fuzzy h bi ideals q k fuzzy h quasi ideals we characterize h hemiregular and h intra hemiregular hemirings by the properties of their q k fuzzy h ideals q k fuzzy h bi idealsand q k fuzzy h quasi ideals some of these characterizations are generalizations of the characterizations given in 36 x ma j zhan generalized fuzzyh bi ideals and h quasi ideals of hemirings inform sci 179 2009 1249 1268

joint signal detection and parameter estimation in multiuser communications the problem of simultaneously detecting the information bits and estimating signal amplitudes and phases in a k user asynchronous direct sequence spread spectrum multiple access communication system is addressed the joint maximum likelihood ml estimator has a computational complexity that is exponential in the total number of bits transmitted and thus does not represent a practical solution to the problem an estimator that combines a suboptimum tree search algorithm with a recursive least squares estimator of complex signal amplitude is considered the complexity of this estimator is o k sup 2 computations per decoded bit and its performance is very close to that of the joint ml receiver this receiver has the advantage that the transmitted signal powers and phases are extracted from the received signal in an adaptive fashion without using a test sequence

fuzzy subrings and ideals redefined abstract v q fuzzy subrings and ideals of a ring are defined the concepts of v q fuzzy semiprime prime semi primary primary and maximal ideals are introduced and characterization of such fuzzy ideals are obtained v q fuzzy cosets determined by v q fuzzy ideals and v q fuzzy radicals of v q fuzzy ideals are discussed

redefined fuzzy hv submodules and many valued implications this paper considers a relationship between fuzzy sets and algebraic hyperstructures a generalization of ideas presented by davvaz b davvaz fuzzy h v submodules fuzzy sets syst 117 2001 477 484 and bhakat and das s k bhakat p das email protected q fuzzy subgroup fuzzy sets syst 80 1996 359 368 is presented in fact the main purpose of this paper is to introduce and study a new sort of fuzzy h v submodule of an h v module called email protected q fuzzy h v submodules these fuzzy h v submodules are characterized by their level h v submodules the concept of a fuzzy h v submodule with thresholds is introduced and some interesting properties are investigated

ucht based complex sequences for asynchronous cdma system the use of orthogonal spreading codes has attracted much attention due to their ability to suppress interference from other users compared with the nonorthogonal sequences in the synchronous case in this paper new sets of orthogonal sequences derived from the unified complex hadamard transforms uchts are investigated various correlation properties of the sequences are mathematically derived and analyzed it is shown that some ucht sequences provide better autocorrelation properties than orthogonal walsh hadamard sequences performance comparisons between ucht sequences gold small set of kasami and m sequences show that some ucht sequences outperform these well known spreading sequences under simulation of systems in the presence of multiple access interference and additive white gaussian noise

new types of fuzzy ideals in bck bci algebras a generalization of an email protected q fuzzy ideal of a bck bci algebra is discussed characterizations of an email protected q k fuzzy ideal and an email protected email protected email protected q email protected fuzzy ideal are provided conditions for an email protected q k fuzzy ideal resp email protected email protected email protected q email protected fuzzy ideal to be a fuzzy ideal are provided using the notion of a fuzzy ideal with thresholds characterizations of a fuzzy ideal an email protected q k fuzzy ideal and an email protected email protected email protected q email protected fuzzy ideal are discussed

bit to bit error dependence in slotted ds ssma packet systems with random signature sequences a technique is developed to find an accurate approximation to the probability of data bit error and the probability of packet success in a direct sequence spread spectrum multiple access ds ssma packet radio system with random signature sequences an improved gaussian approximation to the probability of data bit error is performed packet performance is analyzed by using the theory of moment spaces to gain insight into the effect of bit to bit error dependence caused by interfering signal relative delays and phases which are assumed constant over the duration of a desired packet numerical results show that if no error control exists in the desired packet or if block error control is used when multiple access interference is high the error dependence increases the average probability of packet success beyond that predicted by models which use independent bit errors however when block error control is used and the multiple access interference is low the bit error dependencies cause a reduction in packet error performance

α β fuzzy ideals of hemirings we give a characterization of different types of a b fuzzy ideals of hemirings where a b q q q and a q special attention is paid to q fuzzy prime and semiprime ideals

computationally efficient bounds for the performance of direct sequence spread spectrum multiple access communications systems in jamming environments an approach for calculating upper and lower bounds for the probability of error for asynchronous multiple access spread spectrum communication systems using deterministic codes is presented the techniques is then generalized to include multiple tone jamming the approach utilizes the cumulative distribution function of individual interference terms the computational complexity of the technique is calculated to the polynomial like results showing the multiple access performance of gold codes of lengths 31 and 127 in the presence of jamming are shown the fact that this computational technique gives upper and lower bounds is rigorously proved using the riemann stieltjes integral

semigroups characterized by c c νqk fuzzy ideals generalizing the notions of q fuzzy ideal q fuzzy quasi ideal and q fuzzy bi ideal the concepts of q k fuzzy ideal q k fuzzy quasi ideal and q k fuzzy bi ideal are defined different classes of semigroups are characterized by the properties of these fuzzy ideals

generalized fuzzy hyperideals of hyperrings the concept of quasi coincidence of a fuzzy interval value with an interval valued fuzzy set is considered in fact this is a generalized concept of the quasi coincidence of a fuzzy point with a fuzzy set by using this new idea the notion of interval valued a b fuzzy hyperideals in a hyperring is introduced and consequently a generalization of a fuzzy hyperideal is defined in this paper we study the related properties of the fuzzy hyperideals and in particular the interval valued q fuzzy hyperideals in a hyperring will be investigated moreover we also consider the concept of implication based interval valued fuzzy hyperideals in a hyperring some recent results obtained by b davvaz and j m zhan on hyperstructures are extended and consolidated

optimum multiuser asymptotic efficiency the degradation in bit error rate due to the presence of multiple access interference in a white gaussian channel can be measured by the multiuser asymptotic efficiency defined as the ratio between the snr required to achieve the same uncoded bit error rate in the absence of interfering users and the actual snr in this paper the asymptotic efficiency of the optimum multiuser demodulator a bank of matched filters followed by a viterbi algorithm is investigated and compared to that of the conventional single user matched filter receiver the computation of the optimum asymptotic efficiency of any given user is equivalent to the minimization of the euclidean distance between any pair of multiuser signals which differ in at least one of the symbols of that user it is shown that the optimum multiuser efficiency of asynchronous systems is nonzero with probability 1 and therefore the optimum demodulator does not become multiple access limited in contrast to the single user receiver a class of signal constellations with moderate cross correlation requirements is shown to achieve unit optimum multiuser efficiencies and hence to be equivalent to orthogonal signal sets from the viewpoint of performance of the optimum multiuser detector

error probabilities for binary direct sequence spread spectrum communications with random signature sequences binary direct sequence spread spectrum multiple access communications an additive white gaussian noise channel and a coherent correlation receiver are considered an expression for the output of the receiver is obtained for the case of random signature sequences and the corresponding characteristic function is determined the expression is used to study the density function of the multiple access interference and to determine arbitrarily tight upper and lower bounds on the average probability of error the bounds which are obtained without making a gaussian approximation are compared to results obtained using a gaussian approximation the effects of transmitter power the length of the signature sequences and the number of interfering transmitters are illustrated each transmitter is assumed to have the same power although the general approach can accommodate the case of transmitters with unequal powers

on the definition of a fuzzy subgroup abstract using the idea of quasi coincidence of a fuzzy point with a fuzzy set some new concepts of a fuzzy subgroup are introduced and their acceptibility is investigated some fundamental properties of one such viable fuzzy subgroup are obtained

level subgroups and union of fuzzy subgroups abstract in this paper we investigate the conditions under which a given fuzzy subgroup of a given group can or can not be realized as a union of two proper fuzzy subgroups moreover we formulate the notion of fuzzy subgroup generated by a given fuzzy subset by level subgroups we also give characterizations of fuzzy conjugate subgroups and fuzzy characteristic subgroups by their level subgroups also we discuss the relationship between level subgroups of a given fuzzy subgroup and the level subgroups of its homomorphic image

characterizations of regular semigroups by α β fuzzy ideals using the ideas of belonging and quasi coincidence of a fuzzy point with a fuzzy set the concepts of a b fuzzy ideals and a b fuzzy generalized bi ideals which are generalization of fuzzy ideals and fuzzy generalized bi ideals in a semigroup are introduced and related properties are investigated we also define the lower and upper parts of fuzzy subsets of a semigroup characterizations of regular semigroups by the properties of the lower part of q fuzzy left ideals q fuzzy quasi ideals and q fuzzy generalized bi ideals are given

some kinds of c ccq interval valued fuzzy ideals of bci algebras in this paper we first introduce the notions of positive implicative implicative and commutative interval valued fuzzy ideals of bci algebras which are generalizations of positive implicative implicative and commutative fuzzy ideals respectively and investigate some of their related properties the concept of quasi coincidence of an interval valued fuzzy point within an interval valued fuzzy set is introduced in fact the concept is a generalized concept of quasi coincidence of a fuzzy point within a fuzzy set by using this new idea we further introduce the notions of positive implicative implicative and commutative q interval valued fuzzy ideals of bci algebras and investigate some of their related properties some characterization theorems of these generalized interval valued fuzzy ideals are derived the relationship among these generalized interval valued fuzzy ideals of bci algebras is also considered

generalized fuzzy groups and many valued implications in this paper we give the definition of a fuzzy subgroup with thresholds which is a generalization of rosenfeld s fuzzy subgroup and bhakat and das s fuzzy subgroup we also give the definition of an implication based fuzzy subgroup and discuss relations between two fuzzy subgroups

fuzzy invariant subgroups and fuzzy ideals abstract the purpose of this paper is to introduce some basic concepts of fuzzy algebra as fuzzy invariant subgroups fuzzy ideals and to prove some fundamental properties in particular it will give a characteristic of a field by a fuzzy ideal

quasinormality and fuzzy subgroups abstract we extend the notion of quasinormality to the fuzzy setting we prove that a fuzzy subgroup of a group is fuzzy quasinormal if and only if all its level subsets are quasinormal in the usual group theoretic sense we investigate the natures of homomorphic image and preimage of a fuzzy quasinormal subgroup moreover we introduce the notions of core of a fuzzy subgroup core free fuzzy subgroup fuzzy sylow subgroup and fuzzy maximal subgroup of a group consequently we establish that in a finite group all the fuzzy sylow subgroups of a core free fuzzy quasinormal subgroup are fuzzy quasinormal furthermore we also establish that a fuzzy maximal quasinormal subgroup with the sup property is fuzzy normal

soft bl algebras based on fuzzy sets by means of soft sets and q soft sets some characterizations of implicative positive implicative and fantastic filteristic soft bl algebras are investigated finally we prove that a soft set is an implicative filteristic soft bl algebra if and only if it is both a positive implicative filteristic soft bl algebra and a fantastic filteristic soft bl algebra

an asymptotic analysis of ds ssma communication systems with general linear modulation and error control coding we investigate direct sequence spread spectrum multiple access ds ssma communication systems with general linear modulation and error control coding by the central limit theorem for martingale difference arrays it is proved that under general conditions the overall multiple access interference mai across different symbol intervals tends to a jointly complex gaussian random vector as both the number of chips per symbol interval and the number of interferers tend to infinity the result allows the calculation of the limiting exact error probabilities and justifies the use of the popular standard gaussian approximation the asymptotic properties of the mai from each individual interferer are also examined the results lead to another approximation the conditional gaussian approximation which provides better estimates to the error probabilities especially in near far situations

direct sequence spread spectrum multiple access communications with random signature sequences a large deviations analysis a direct sequence spread spectrum multiple access bit error probability analysis is developed using large deviations theory let m denote the number of interfering spread spectrum signals and let n denote the signature sequence length then the large deviations limit is as n to infinity with m fixed a tight asymptotic expression for the bit error probability is proven and in addition recent large deviations results with the importance sampling monte carlo estimation technique are applied to obtain accurate and computationally efficient estimates of the bit error probability for finite values of m and n the large deviations point of view is compared also to the conventional asymptotics of central limit theory and the associated gaussian approximation the gaussian approximation is accurate and the ratio m n is moderately large and all signals have roughly equal power in the near far situation however the gaussian approximation is quite poor in contrast large deviations techniques are more accurate in the near far situation and it is here that these methods provide some important practical insight

a novel frequency hopping spread spectrum multiple access network using m ary orthogonal walsh sequence keying a novel frequency hop spread spectrum multiple access network employing m ary orthogonal walsh sequence keying with noncoherent demodulation is proposed the transmitted walsh sequence is overlaid by a user specific pseudonoise sequence to reduce the effect of multiple access hits two gaussian approximations for the multiple access interference from both the dehopped slot and its neighboring slots are developed and are used to analyze the performance of the proposed network for synchronous and asynchronous hopping under nonfading and rayleigh fading channels the effect of imperfect hop timing synchronization at the receiver is also analyzed it is shown that the proposed network offers significantly improved network throughput compared to networks based on traditional m ary frequency shift keying modulation

some kinds of fuzzy ideals of bci algebras the concepts of c c q d fuzzy positive implicative implicative and commutative ideals and c c q d fuzzy positive implicative implicative and commutative ideals in bci algebras are introduced some new characterizations are investigated in particular we prove that a fuzzy set m of a bci algebra x is an c c q d fuzzy implicative ideal of x if and only if it is both an c c q d fuzzy positive implicative ideal and an c c q d fuzzy commutative ideal finally we give some characterizations of three particular classes of bci algebras by these generalized fuzzy ideals

redefined fuzzy implicative filters using the belongs to relation and quasi coincidence with relation q between fuzzy points and fuzzy sets the concept of q j fuzzy implicative filters where q j are any two of q email protected q email protected q with q email protected q is introduced and related properties are discussed relations between email protected q email protected q fuzzy implicative filters and email protected q fuzzy implicative filters are investigated and conditions for an email protected q fuzzy implicative filter to be an fuzzy implicative filter are provided characterizations of email protected q fuzzy implicative filters are given and conditions for a fuzzy set to be a q email protected q fuzzy implicative filter are provided

fuzzy n ary polygroups related to fuzzy points recently fuzzy n ary sub polygroups were introduced and studied by davvaz corsini and leoreanu fotea b davvaz p corsini v leoreanu fotea fuzzy n ary sub polygroups comput math appl 57 2008 141 152 now in this paper the concept of email protected q fuzzy n ary sub polygroups email protected email protected email protected email protected fuzzy n ary sub polygroups and fuzzy n ary sub polygroup with thresholds of an n ary polygroup are introduced and some characterizations are described also we give the definition of implication based fuzzy n ary sub polygroups in an n ary polygroup in particular the implication operators in lukasiewicz system of continuous valued logic are discussed

performance evaluation for band limited ds cdma systems based on simplified improved gaussian approximation the standard gaussian approximation sga for error analysis of direct sequence code division multiple access ds cdma systems is very optimistic in many cases improved gaussian approximation iga is a technique that produces accurate error probabilities but is still computationally intensive simplified iga siga has complexity similar to that of sga and at the same time provides sufficient accuracy in this paper we consider siga for ds cdma systems employing random sequences in a band limited scenario the validity of iga for band limited systems is established in a rigorous mathematical sense then a key parameter in siga is derived via a frequency domain approach applications to a number of typical chip waveforms including the popular sinc and raised cosine pulses are investigated performance comparison with iga based lower and upper bounds shows that siga yields very accurate probability of error

an efficient technique for evaluating direct sequence spread spectrum multiple access communications a technique is presented for obtaining bounds on the average probability of error for direct sequence spread spectrum multiple access ds ssma communications the technique is of interest because it yields arbitrarily right bounds involves a small amount of computation avoids numerical integrations and applies to many types of detection as an illustration the technique is applied to binary ds ssma communications an additive white gaussian noise channel and a coherent correlation receiver it is assumed that all the signature sequences are deterministic each transmitter is assumed to have the same power although the approach can accommodate the case of transmitters with unequal powers expressions are given for the density functions of the random variables that model the multiple access interference these expressions are used to obtain arbitrarily tight upper and lower bounds on the average probability of error without making a gaussian approximation or performing numerical integrations to incorporate the effects of multiple access interference

bit error probabilities of multicode direct sequence spread spectrum multiple access systems many techniques for calculating bit error probabilities beps of direct sequence spread spectrum multiple access systems ds ssma have been reported among them are the following three techniques 1 the standard gaussian approximation 2 the improved gaussian approximation 3 and the simplified improved gaussian approximation we extend these techniques to derive the beps of multicode ds ssma systems we assess the three techniques by comparing their results with the result of computer simulation

ϵ q level subset abstract the notion of q level subset is introduced the study of q level subset of an q fuzzy subgroup subring or ideal are dealt with

fuzzy subgroups some characterizations the notion of a fuzzy set was first introduced in 1965 by zadeh 12 since then the theory of fuzzy sets has gone through remarkably rapid strides with well over 4000 papers by now see for example the bibliography 3 several textbooks for example 2 and 6 and an international journal solely devoted to it s the theory has found wideranging applications in such diverse fields as automata control theory decision theory and social behavior pattern studies to name just a few for an interesting expository account see rosenfeld lo and also the book review 7 in 9 rosenfeld introduced the notion of a fuzzy group and showed that many concepts of group theory can be extended in an elementary manner to develop the theory of fuzzy groups in particular he characterized all the fuzzy subgroups of cyclic groups of prime order 9 proposition 5 101 fuzzy groups were further investigated by das in 1 where he characterized all the fuzzy subgroups of finite cyclic groups l theorem 4 21 in this connection he introduced the notion of level subgroups of a fuzzy subgroup which is based on the notion of a level subset introduced earlier by zadeh for a finite group das showed that these level subgroups of a fuzzy subgroup form a chain 1 corollary 3 11 and also constructed a fuzzy subgroup whose chain of level subgroups is maximal in the following special cases when the group is i a direct product of cyclic groups of prime orders ii abelian l theorem 3 41 we analyze the level subgroups of a fuzzy subgroup in more detail and investigate whether the family of level subgroups of a fuzzy subgroup deter

generalized fuzzy interior ideals in semigroups using the idea of quasi coincidence of a fuzzy point with a fuzzy set the concept of an a b fuzzy interior ideal which is a generalization of a fuzzy interior ideal in a semigroup is introduced and related properties are investigated

characterizations of regular ordered semigroups in terms of α β fuzzy generalized bi ideals in this paper the concept of an a b fuzzy generalized bi ideal in an ordered semigroup is introduced which is a generalization of the concept of a fuzzy generalized bi ideal in an ordered semigroup using this concept some characterization theorems are provided the upper lower parts of an q fuzzy generalized bi ideal are introduced and some characterizations of regular ordered semigroups are given also we consider the concept of implication based fuzzy generalized bi ideals in an ordered semigroup in particular the implication operators in lukasiewicz system of continuous valued logic are discussed

dehn surgery on knots in 3 manifolds it has been known for over 30 years that every closed connected orientable 3manifold is obtained by surgery on a link in s3 8 however a classification of such 3 manifolds in terms of this surgery construction has remained elusive this is due primarily to the lack of uniqueness of the surgery description in 5 kirby gave us a calculus of surgery diagrams however the lack of a canonical surgical method of getting from one 3 manifold to another has hampered further progress in this paper we show that if one restricts attention to the case where a surgery curve is homotopically trivial in a 3 manifold then one has the following uniqueness theorem

more on fuzzy lattices in this paper the concept of an q k fuzzy sublattice ideal filter and q k fuzzy sublattice ideal filter in a lattice is introduced which is a generalization of the concept as given by davvaz and kazanci 2011 18 characterizations for an q k fuzzy sublattice ideal filter and q k fuzzy sublattice ideal filter are provided different classes of lattices are characterized by the properties of these fuzzy sublattices ideals filters using the notions of a fuzzy sublattice ideal filter with thresholds characterization of a fuzzy sublattice ideal filter an q k fuzzy sublattice ideal filter and q k fuzzy sublattice ideal filter are discussed

performance of ds ssma communications in impulsive channels ii hard limiting correlation receivers for pt i see ibid vol com 35 no 11 p 1179 88 1987 in part i it was demonstrated that impulsive channel noise can be a serious detriment to the performance of direct sequence spread spectrum multiple access ds ssma communications when conventional linear correlation reception is used here a hard limiting correlator as an alternative for reception of multiple access transmission in impulsive channels is considered for k asynchronous binary psk ds ssma users sharing a linear channel corrupted by impulsive noise that is modeled at the output of the front end filter of the receiver techniques are developed for analyzing bit error probabilities of this hard limiting receiver by exact computation for short spreading sequences by approximation for longer spreading sequences and by asymptotic limits for infinitely long spreading sequences performance is compared to that of the linear correlator under a variety of conditions showing that hard limiting correlation reception can offer substantial improvement over conventional systems in impulsive channels however the linear receiver is more effective against multiple access noise only and so a tradeoff emerges between rejection of impulsive noise and rejection of multiple access interference

fuzzy subgroup some characterizations ii abstract we consider an analysis of fuzzy subgroups in terms of the corresponding family of level subgroups given a finite chain of subgroups of a group g we prove that there exists a fuzzy subgroup of g whose level subgroups are exactly the subgroups of this chain as a corollary we obtain an interpretation of the number of chains of subgroups of a group g in which a subgroup h is a member when the group g is a supersolvable group some further interpretation of this number is obtained