the poisson multiple access channel the poisson multiple access channel mac models many to one optical communication through an optical fiber or in free space for this model we compute the capacity region for the two user case as a function of the allowed peak power focusing on the maximum throughput we generalize our results to the case where the users are subjected to an additional average power constraint and to the many users case we show that contrary to the gaussian mac in the poisson mac the maximum throughput is bounded in the number of users we quantify the loss that is incurred when time division multiple access tdma is employed and show that while in the two user case and in the absence of dark current the penalty is rather mild the penalty can be quite severe in the many users case in the presence of large dark current we introduce a generalized tdma technique that mitigates this loss to a large extent

the painleve test backlund transformation and solutions of the reduced maxwell bloch equations the painleve property for partial differential equations pdes proposed by weiss et al 1983 is studied for a system of pdes namely the reduced maxwell bloch rmb equations the rmb equations describe the propagation of short optical pulses through dielectric materials with a resonant non degenerate transition the author demonstrates that the rmb system passes the painleve test and constructs a backlund transformation and solutions of the rmb equations

cylindrical korteweg de vries equation and painleve property the authors demonstrate that the lax representation for the cylindrical korteweg de vries equation can be obtained with the help of the painleve property of this equation

randomized resource allocation in decentralized wireless networks in this paper we consider a decentralized wireless communication network with a fixed number u of frequency subbands to be shared among n transmitter receiver pairs it is assumed that the number of active users is a realization of a random variable with a given probability mass function moreover users are unaware of each other s codebooks and hence no multiuser detection is possible we propose a randomized frequency hopping fh scheme in which each transmitter randomly hops over a subset of u subbands from transmission slot to transmission slot assuming all users transmit gaussian signals the distribution of the noise plus interference is mixed gaussian which makes calculation of the mutual information between the transmitted and received signals of each user intractable we derive lower and upper bounds on the mutual information of each user and demonstrate that for large signal to noise ratio snr values the two bounds coincide this observation enables us to compute the sum multiplexing gain of the system and obtain the optimum hopping strategy for maximizing this quantity we compare the performance of the fh system to that of the frequency division fd system in terms of the following performance measures average sum multiplexing gain 1 and average minimum multiplexing gain per user 2 we show that depending on the probability mass function of the number of active users the fh system can offer a significant improvement in terms of 1 and 2 implying a more efficient usage of the spectrum in the sequel we consider a scenario where the transmitters are unaware of the number of active users in the network as well as the channel gains developing a new upper bound on the differential entropy of a mixed gaussian random vector and using entropy power inequality we obtain lower bounds on the maximum transmission rate per user to ensure a specified outage probability at a given snr level we demonstrate that the so called outage capacity can be considerably higher in the fh scheme than in the fd scenario for reasonable distributions on the number of active users this guarantees a higher spectral efficiency in fh compared to fd

use of historical controls in time adjusted trend tests for carcinogenicity we develop a method for incorporating historical control information into time adjusted tests for dose effects in carcinogenicity studies after discretizing the time scale we use a multinomial distribution to model the number of animals dying with tumor in each interval data from past studies are used to estimate the parameters characterizing the prior a score test derived from the resulting dirichlet multinomial generalizes the test of tarone 1982 biometrics 38 215 220 and reduces in the limit to the log rank test in the case of a diffuse prior the methodology is illustrated with data from a study of the fire retardant 2 2 bis bromomethyl 1 3 propanediol

using historical controls to adjust for covariates in trend tests for binary data abstract historical data often play an important role in helping interpret the results of a current study this article is motivated primarily by one specific application the analysis of data from rodent carcinogenicity studies by proposing a suitable informative prior distribution on the relationship between control outcome data and covariates we derive modified trend test statistics that incorporate historical control information to adjust for covariate effects frequentist and fully bayesian methods are presented and novel computational techniques are developed to compute the test statistics several attractive theoretical and computational properties of the proposed priors are derived in addition a semiautomatic elicitation scheme for the priors is developed our approach is used to modify a widely used prevalence test for carcinogenicity studies the proposed methodology is applied to data from a national toxicology program carcinogenicity experiment and is shown to provide helpful insight on t

random sequence multisets for synchronous code division multiple access channels the effect of using randomly selected sequence multisets for the uplink of a synchronous code division multiple access channel is considered a tight lower bound on the expected value of the sum capacity over the ensemble of randomly selected sequence multisets is given for large systems the sum rate penalty for using randomly selected multisets is shown to be at most 1 nat and to vanish as the number of users becomes large compared to the sequence length

sinh gordon equation painleve property and backlund transformation abstract the painleve property for partial differential equation proposed by weiss et al is studied for the sinh gordon equation we performed a singular point analysis to show that the painleve property is a valuable analytical test for integrability and we found in a remarkably straightforward manner the backlund transformation of the sinh gordon equation

polar codes for the two user multiple access channel in this paper polar codes for the m user multiple access channel mac with binary inputs are constructed it is shown that arikan s polarization technique applied individually to each user transforms independent uses of an m user binary input mac into successive uses of extremal macs this transformation has a number of desirable properties 1 the uniform sum rate of the original mac is preserved 2 the extremal macs have uniform rate regions that are not only polymatroids but matroids and thus 3 their uniform sum rate can be reached by each user transmitting either uncoded or fixed bits in this sense they are easy to communicate over a polar code can then be constructed with an encoding and decoding complexity of o n log n where n is the block length a block error probability of o exp n1 2 e and capable of achieving the uniform sum rate of any binary input mac with arbitrary many users applications of this polar code construction to channels with a finite field input alphabet and to the additive white gaussian noise channel are also discussed

asymptotically optimal multiple access communication via distributed rate splitting we consider the multiple access communication problem in a distributed setting for both the additive white gaussian noise channel and the discrete memoryless channel we propose a scheme called distributed rate splitting to achieve the optimal rates allowed by information theory in a distributed manner in this scheme each real user creates a number of virtual users via a power rate splitting mechanism in the m user gaussian channel or via a random switching mechanism in the m user discrete memoryless channel at the receiver all virtual users are successively decoded compared with other multiple access techniques distributed rate splitting drs can be implemented with lower complexity and less coordination furthermore in a symmetric setting we show that the rate tuple achieved by this scheme converges to the maximum equal rate point allowed by the information theoretic bound as the number of virtual users per real user tends to infinity when the capacity regions are asymmetric we show that a point on the dominant face can be achieved asymptotically finally when there is an unequal number of virtual users per real user we show that differential user rate requirements can be accommodated in a distributed fashion

combining historical and randomized controls for assessing trends in proportions abstract a statistical method for incorporating historical control data in the analysis of proportions is proposed and illustrated the method has as its extremes logistic regressions completely pooling and completely ignoring historical controls the degree of pooling used is determined by the variability from experiment to experiment in the control incidences the fit of historical control groups to an assumed normal logistic model is assessed using probability plotting techniques monte carlo studies evaluate the adequacy of the asymptotic approximation used sensitivity analyses show that results are insensitive to alternative priors the method is applied to several sets of tumor data from animal experiments

asynchronous communication exact synchronization universality and dispersion recently tchamkerten and coworkers proposed a novel variation of the problem of joint synchronization and error correction this paper considers a strengthened formulation that requires the decoder to estimate both the message and the location of the codeword exactly such a scheme allows for transmitting data bits in the synchronization phase of the communication thereby improving bandwidth and energy efficiencies it is shown that the capacity region remains unchanged under the exact synchronization requirement furthermore asynchronous capacity can be achieved by universal channel independent codes comparisons with earlier results on another delay compensated definition of rate are made the finite blocklength regime is investigated and it is demonstrated that even for moderate blocklengths it is possible to construct capacity achieving codes that tolerate exponential level of asynchronism and experience only a rather small loss in rate compared to the perfectly synchronized setting in particular the channel dispersion does not suffer any degradation due to asynchronism for the binary symmetric channel a translation coset of a good linear code is shown to achieve the capacity synchronization tradeoff

symmetric capacity and signal design for l out of k symbol synchronous cdma gaussian channels we consider the symbol synchronous gaussian l out of k code division multiaccess channel and obtain the capacity region and the upper and lower bounds to the symmetric capacity the capacity region is found to be the same with or without frame synchronism the lower bound depends on the signature waveforms through the eigenvalues of the snr weighted crosscorrelation matrix we find a sufficient condition for the signature waveform set to maximize this lower bound and give an algorithm to construct a set of signature waveforms satisfying the sufficient condition

a formulation of the channel capacity of multiple access channel the necessary and sufficient condition of the channel capacity is rigorously formulated for the n user discrete memoryless multiple access channel mac the essence is to invoke an elementary mac where sizes of input alphabets are not greater than the size of output alphabet the main objective is to demonstrate that the channel capacity of an mac is achieved by an elementary mac included in the original mac the proof is quite straightforward by the very definition of the elementary mac the second objective is to prove that the kuhn tucker conditions of the elementary mac are sufficient obviously necessary for the channel capacity the latter proof requires two distinctive properties of the mac every solution of the kuhn tucker conditions is a local maximum on the domain of all possible input probability distributions ipds and then particularly for the elementary mac a set of ipds for which the value of the mutual information is not smaller than the arbitrary positive number is connected on the domain as a result in respect of the channel capacity the mac in general can be regarded as an aggregate of a finite number of elementary macs

minimum breakdown degradation in binary source encoding a memoryless binary equiprobable source produces one letter per second two people each are provided separately with private information about the source data at a rate of 1 2 bit per second suppose that by pooling their information they can produce a long mn reconstruction of the source output that has arbitrarily small error frequency we prove that then the least common asymptotic error frequency d that each can achieve without the other s help is sqrt 2 1 2 0 207 since it had been shown previously that 0 200 leq d leq 0 207 our result closes the so called 007 gap new analytical techniques introduced to effect the proof are of broader significance in multiuser information theory

classical communication over a quantum interference channel calculating the capacity of interference channels is a notorious open problem in classical information theory such channels have two senders and two receivers and each sender would like to communicate with a partner receiver the capacity of such channels is known exactly in the settings of very strong and strong interference while the han kobayashi coding strategy gives the best known achievable rate region in the general case here we introduce and study the quantum interference channel a natural generalization of the interference channel to the setting of quantum information theory we restrict ourselves for the most part to channels with two classical inputs and two quantum outputs in order to simplify the presentation of our results though generalizations of our results to channels with quantum inputs are straightforward we are able to determine the exact classical capacity of this channel in the settings of very strong and strong interference by exploiting winter s successive decoding strategy and a novel two sender quantum simultaneous decoder respectively we provide a proof that a han kobayashi strategy is achievable with holevo information rates up to a conjecture regarding the existence of a three sender quantum simultaneous decoder this conjecture holds for a special class of quantum multiple access channels with average output states that commute and we discuss some other variations of the conjecture that hold finally we detail a connection between the quantum interference channel and prior work on the capacity of bipartite unitary gates

new results in binary multiple descriptions an encoder whose input is a binary equiprobable memoryless source produces one output of rate r 1 and another of rate r 2 let d 1 d 2 and d 0 respectively denote the average error frequencies with which the source data can be reproduced on the basis of the encoder output of rate r l only the encoder output of rate r 2 only and both encoder outputs the two descriptions problem is to determine the region r of all quintuples r 1 r 2 d 1 d 2 d 0 that are achievable in thc usual shannon sense let r d 1 d log 2 d 1 d log 2 1 d denote the error frequency rate distortion function of the source the no excess rate case prevails when r 1 r 2 r d 0 and the excess rate case when r 1 r 2 r d 0 denote the section of r at r 1 r 2 d 0 by d r 1 r 2 d 0 d 1 d 2 r 1 r 2 d 1 d 2 d 0 in r in the no excess rate case we show that a portion of the boundary of d r 1 r 2 d 0 coincides with the curve frac 1 2 d 1 2d 0 frac 1 2 d 2 2d 0 frac 1 2 1 2d 0 2 this curve is an extension of witsenhausen s hyperbola bound to the case d 0 0 it follows that the projection of r onto the d 1 d 2 plane at fixed d 0 consists of all d 1 geq d 0 and d 2 geq d 0 that lie on or above this hyperbola in the excess rate case we show by counterexample that the achievable region of el gamal and cover is not tight

fairness in multiuser systems with polymatroid capacity region for a wide class of multiuser systems a subset of capacity region which includes the corner points and the sum capacity facet has a special structure known as polymatroid multiple access channels with fixed input distributions and multiple antenna broadcast channels are examples of such systems any interior point of the sum capacity facet can be achieved by time sharing among corner points or by an alternative method known as rate splitting the main purpose of this paper is to find a point on the sum capacity facet which satisfies a notion of fairness among the active users this problem is addressed in two cases i where the complexity of achieving interior points is not feasible and ii where the complexity of achieving interior points is feasible for the first case the corner point for which the minimum rate of the active users is maximized is desired a simple greedy algorithm is introduced to find such an optimum corner point in addition it is shown for single antenna gaussian multiple access channels the resulting corner point is leximin maximal with respect to the set of the corner points for the second case the properties of the unique leximin maximal rate vector with respect to the polymatroid are reviewed it is shown that the problems of deriving the time sharing coefficients or rate splitting scheme to attain the leximin maximal vector can be solved by decomposing the problem into some lower dimensional subproblems in addition a fast algorithm to compute the time sharing coefficients to attain a general point on the sum capacity facet is presented

on multiple descriptions and team guessing witsenhausen s hyperbola bound for the multiple description problem without excess rate in case of a binary source is not tight for exact joint reproductions however this bound is tight for almost exact joint reproductions theorem 1 conjectured by witsenhausen the proof is based on an em approximative form of the team guessing lemma for em sequences of random variables this result may be of interest also for team guessing the hyperbola bound is also tight for exact joint reproductions and arbitrarily small but positive excess rate theorem 2 the proof of this result uses our covering lemma

achieving the uniform rate region of general multiple access channels by polar coding we consider the problem of polar coding for transmission over m user multiple access channels in the proposed scheme all users encode their messages using a polar encoder while a multiuser successive cancellation decoder is deployed at the receiver the encoding is done separately across the users and is independent of the target achievable rate for the code construction the positions of information bits and frozen bits for each of the users are decided jointly this is done by treating the polar transformations across all the m users as a single polar transformation with a certain polarization base we characterize the resolution of achievable rates on the dominant face of the uniform rate region in terms of the number of users m and the length of the polarization base l in particular we prove that for any target rate on the dominant face there exists an achievable rate also on the dominant face within the distance at most frac m 1 sqrt m l from the target rate we then prove that the proposed mac polar coding scheme achieves the whole uniform rate region with fine enough resolution by changing the decoding order in the multiuser successive cancellation decoder as l and the code block length n grow large the encoding and decoding complexities are o n log n and the asymptotic block error probability of o 2 n 0 5 epsilon is guaranteed examples of achievable rates for the 3 user multiple access channel are provided

multiple description quantization via gram schmidt orthogonalization the multiple description md problem has received considerable attention as a model of information transmission over unreliable channels a general framework for designing efficient md quantization schemes is proposed in this paper we provide a systematic treatment of the el gamal cover egc achievable md rate distortion region and show it can be decomposed into a simplified egc segc region and a superimposed refinement operation furthermore any point in the segc region can be achieved via a successive quantization scheme along with quantization splitting for the quadratic gaussian case the proposed scheme has an intrinsic connection with the gram schmidt orthogonalization which implies that the whole gaussian md rate distortion region is achievable with a sequential dithered lattice based quantization scheme as the dimension of the optimal lattice quantizers becomes large moreover this scheme is shown to be universal for all independent and identically distributed i i d smooth sources with performance no worse than that for an i i d gaussian source with the same variance and asymptotically optimal at high resolution a class of md scalar quantizers in the proposed general framework is also constructed and is illustrated geometrically the performance is analyzed in the high resolution regime which exhibits a noticeable improvement over the existing md scalar quantization schemes

the painleve property for partial differential equations ii backlund transformation lax pairs and the schwarzian derivative in this paper we investigate the painleve property for partial differential equations by application to several well known partial differential equations burgers kdv mkdv bousinesq higher order kdv and kp equations it is shown that consideration of the singular manifold leads to a formulation of these equations in terms of the schwarzian derivative this formulation is invariant under the moebius group acting on dependent variables and is shown to obtain the appropriate lax pair linearization for the underlying nonlinear pde

analytic structure of the henon heiles hamiltonian in integrable and nonintegrable regimes the solutions of the henon heiles hamiltonian are investigated in the complex time plane the use of the painleve property i e the property that the only movable singularities exhibited by the solution are poles enables successful prediction of the values of the nonlinear coupling parameter for which the system is integrable special attention is paid to the structure of the natural boundaries that are found in some of the nonintegrable regimes these boundaries have a remarkable self similar structure whose form changes as a function of the nonlinear coupling

tests for differences in tumor incidence based on animal carcinogenesis experiments abstract in animal carcinogenesis studies statistical methods that compare the production of occult tumors should compare tumor incidence rates in general the incidence rate cannot be identified even approximately without both survival and sacrifice information if information from frequent sacrifices is available however a function that approximates the incidence rate can be identified without assumptions about the relationship between tumor incidence and death some earlier proposals that based comparisons on tumor prevalence rates and other functions also compared tumor incidence rates under special conditions but these tests can be biased when the conditions are violated tests that compare functions approximating tumor incidence rates can be developed using survival sacrifice information but these tests may be seriously inefficient in special cases in which sacrifices are not necessary to identify the tumor incidence rate

analytic solutions of carrier flow equations via the painleve analysis approach the authors use the painleve approach to analyse a system of partial differential equations governing the carrier flow in semiconductor devices and obtain its auto backlund transformations moreover they obtain some analytic solutions directly from the painleve backlund equations by introducing two elementary homographic invariants

quickest sequence phase detection a phase detection sequence is a length n cyclic sequence such that the location of any length k contiguous subsequence can be determined from a noisy observation of that subsequence in this paper we derive bounds on the minimal possible k in the limit of n to infty and describe some sequence constructions we further consider multiple phase detection sequences where the location of any length k contiguous subsequence of each sequence can be determined simultaneously from a noisy mixture of those subsequences we study the optimal trade offs between the lengths of the sequences and describe some sequence constructions we compare these phase detection problems to their natural channel coding counterparts and show a strict separation between the fundamental limits in the multiple sequence case both adversarial and probabilistic noise models are addressed

coset codes for compound multiple access channels with common information code construction is considered for arbitrary discrete memoryless compound multiple access channels macs with common information this class of channels includes macs with without common messages or with partially cooperating encoders a construction method of code ensembles based on coset codes is proposed for these channels assuming joint maximum likelihood decoding the performance of the proposed code ensemble is analyzed by deriving a lower bound on error exponents a condition assuring that codes achieve the capacity region on average is given it is seen that an elaborate combination of good linear codes gives capacity achieving codes for compound macs with common messages or with partially cooperating encoders the use of restricted ensembles with low density parity check ldpc codes as component codes is also discussed it is shown that a coset code ensemble based on nonbinary regular ldpc codes approaches the random coding exponent and thus is capacity achieving

exact random coding error exponents of optimal bin index decoding we consider ensembles of channel codes that are partitioned into bins and focus on analysis of exact random coding error exponents associated with optimum decoding of the index of the bin to which the transmitted codeword belongs two main conclusions arise from this analysis i for independent random selection of codewords within a given type class the random coding exponent of optimal bin index decoding is given by the ordinary random coding exponent function computed at the rate of the entire code independently of the exponential rate of the size of the bin ii for this ensemble of codes sub optimal bin index decoding that is based on ordinary maximum likelihood ml decoding is as good as the optimal bin index decoding in terms of the random coding error exponent achieved finally for the sake of completeness we also outline how our analysis of exact random coding exponents extends to the hierarchical ensemble that correspond to superposition coding and optimal decoding where for each bin first a cloud center is drawn at random and then the codewords of this bin are drawn conditionally independently given the cloud center for this ensemble conclusions i and ii mentioned above no longer hold necessarily in general

low complexity approaches to slepian wolf near lossless distributed data compression this paper discusses the slepian wolf problem of distributed near lossless compression of correlated sources we introduce practical new tools for communicating at all rates in the achievable region the technique employs a simple source splitting strategy that does not require common sources of randomness at the encoders and decoders this approach allows for pipelined encoding and decoding so that the system operates with the complexity of a single user encoder and decoder moreover when this splitting approach is used in conjunction with iterative decoding methods it produces a significant simplification of the decoding process we demonstrate this approach for synthetically generated data finally we consider the slepian wolf problem when linear codes are used as syndrome formers and consider a linear programming relaxation to maximum likelihood ml sequence decoding we note that the fractional vertices of the relaxed polytope compete with the optimal solution in a manner analogous to that observed when the min sum iterative decoding algorithm is applied this relaxation exhibits the ml certificate property if an integral solution is found it is the ml solution for symmetric binary joint distributions we show that selecting easily constructable expander style low density parity check codes ldpcs as syndrome formers admits a positive error exponent and therefore provably good performance

writing on dirty paper corresp a channel with output y x s z is examined the state s sim n 0 qi and the noise z sim n 0 ni are multivariate gaussian random variables i is the identity matrix the input x in r n satisfies the power constraint l n sum i 1 n x i 2 leq p if s is unknown to both transmitter and receiver then the capacity is frac 1 2 ln 1 p n q nats per channel use however if the state s is known to the encoder the capacity is shown to be c ast frac 1 2 ln 1 p n independent of q this is also the capacity of a standard gaussian channel with signal to noise power ratio p n therefore the state s does not affect the capacity of the channel even though s is unknown to the receiver it is shown that the optimal transmitter adapts its signal to the state s rather than attempting to cancel it

the capacity region of the totally asynchronous multiple access channel it is shown that the capacity region of the asynchronous multiple access channel differs from that of the synchronous channel only by the lack of a convex hull operation

totally asynchronous slepian wolf data compression it is proved that the slepian wolf data compression theorem still holds when both encoders are operating totally asynchronously in addition it is shown that in this case the wyner ahlswede korner source coding theorem holds

on the structure of the capacity region of asynchronous memoryless multiple access channels the asynchronous capacity region of memoryless multiple access channels is the union of certain polytopes it is well known that vertices of such polytopes may be approached via a technique called successive decoding it is also known that an extension of successive decoding applies to the dominant face of such polytopes the extension consists of forming groups of users in such a way that users within a group are decoded jointly whereas groups are decoded successively this paper goes one step further it is shown that successive decoding extends to every face of the aforementioned polytopes the group composition as well as the decoding order for all rates on a face of interest is obtained from a label assigned to that face from the label one can extract a number of structural properties such as the dimension of the corresponding face and whether or not two faces intersect expressions for the number of faces of any given dimension are also derived from the labels

using historical controls in the analysis of developmental toxicity data historical control data can often aid in the interpretation of the results from laboratory dose response experiments for example formal statistical methods for using historical data are well established for carcinogenicity studies in that case a score test derived from a beta binomial model yields a simple modification of the standard cochran armitage test for trend however this test cannot be used for developmental toxicity studies since it does not allow for the additional correlation structure induced by the presence of litter effects in this paper quasi likelihood methods are used to incorporate historical control information into a trend test for the types of correlated binary outcomes that typically arise in developmental toxicity studies the proposed test is asymptotically equivalent to the beta binomial score test in the special case when all the litter sizes are equal to 1 malformation data from a series of developmental toxicity studies illustrate the results

new coding schemes for the symmetric k description problem we propose novel coding schemes for the k description problem with symmetric rates and symmetric distortion constraints there are two main new ingredients in these schemes the first one is akin to the method seen in the well known butterfly network of network coding literature and systematic erasure channel codes are applied on certain carefully chosen source coding component the second approach is built on the quantization splitting technique which was previously proven useful in the gaussian ceo problem we first focus on a special case of the three description problem where any two descriptions are rate distortion optimal jointly referred to as the no two description excess rate case for this special case and the quadratic gaussian source we show that the two aforementioned approaches lead to rate distortion points outside the achievable region based on the source channel erasure codes previously proposed by pradhan puri and ramchandran interestingly though only the symmetric problem is considered in our work the proposed schemes in fact benefit from time sharing several asymmetric rate distortion points the insights gained through the no two description excess rate case lead to strategic combination of the new ingredients with the existing coding scheme yielding new coding schemes for the symmetric k description problem

on multistage successive refinement for wyner ziv source coding with degraded side informations in this correspondence we provide a complete characterization of the rate distortion region for the multistage successive refinement of the wyner ziv source coding problem with degraded side informations at the decoder necessary and sufficient conditions for a source to be successively refinable along a distortion vector are subsequently derived a source channel separation theorem is provided when the descriptions are sent over independent channels for the multistage case furthermore the notion of generalized successive refinability with multiple degraded side informations is introduced this notion captures whether progressive encoding to satisfy multiple distortion constraints for different side informations is as good as encoding without progressive requirement necessary and sufficient conditions for generalized successive refinability are given it is shown that the following two sources are generalized successively refinable 1 the gaussian source with degraded gaussian side informations and 2 the doubly symmetric binary source when the worse side information is a constant thus for both cases the failure of being successively refinable is only due to the inherent uncertainty on which side information will occur at the decoder but not the progressive encoding requirement

rate splitting multiple access for discrete memoryless channels it is shown that the encoding decoding problem for any asynchronous m user discrete memoryless multiple access channel can be reduced to corresponding problems for at most 2m 1 single user discrete memoryless channels this result which extends a similar result for gaussian channels reduces the seemingly hard task of finding good multiple access codes to the much better understood task of finding good codes for single user channels as a by product some interesting properties of the capacity region of m user asynchronous discrete memoryless channels are derived

achieving 1 2 log 1 snr on the awgn channel with lattice encoding and decoding we address an open question regarding whether a lattice code with lattice decoding as opposed to maximum likelihood ml decoding can achieve the additive white gaussian noise awgn channel capacity we first demonstrate how minimum mean square error mmse scaling along with dithering lattice randomization techniques can transform the power constrained awgn channel into a modulo lattice additive noise channel whose effective noise is reduced by a factor of spl radic 1 snr snr for the resulting channel a uniform input maximizes mutual information which in the limit of large lattice dimension becomes 1 2 log 1 snr i e the full capacity of the original power constrained awgn channel we then show that capacity may also be achieved using nested lattice codes the coarse lattice serving for shaping via the modulo lattice transformation the fine lattice for channel coding we show that such pairs exist for any desired nesting ratio i e for any signal to noise ratio snr furthermore for the modulo lattice additive noise channel lattice decoding is optimal finally we show that the error exponent of the proposed scheme is lower bounded by the poltyrev exponent

the use of historical control information in testing for a trend in proportions a problem commonly faced in biometric applications is to test for a trend in proportions in a 2 x k contingency table in which the k columns have a natural ordering for example a test compound may be administered at increasing dose levels to groups of test animals to determine if the proportion of animals developing a tumor increases with increasing dose level cochran 1954 and armitage 1955 proposed a chi square statistic for testing for a trend in proportions for problems with a large amount of historical data a test for trend incorporating the historical data would be useful this paper develops such a test based on a statistic which is closely related to that of cochran and armitage this method for binomial proportions is analogous to the method derived by pocock 1976 for normallydistributed data the problem will be developed in the context of an animal carcinogenesis experiment consider an experiment involving r 1 groups of test animals one group serves as a control group and the remaining r groups are given a test compound at increasing dose levels dld2 dr the animals are followed for a fixed period of time and the number of animals which develop a tumor at a particular organ is recorded for each group let ni denote the number of animals in the ith group and let the number of these animals which develop a tumor during the course of the experiment be denoted by xi i 0 1 r the results of this experiment can be summarized in a 2 x r 1 table such as table 1 to test for ap increase in the proportions pi xjni with increasing dose level cochran and armitage suggested the test statistic

n channel symmetric multiple descriptions part i n k source channel erasure codes in this two part paper we present a new achievable rate region for the general n channel symmetric multiple descriptions problem in part i inspired by the concept of maximum distance separable mds erasure channel codes we consider a special case of this rate region where the source is encoded into n descriptions each with rate r these descriptions are transmitted over n bandwidth constrained and errorless channels during transmission a subset of these channels can break down thus erasing the corresponding descriptions the decoder is interested in recovering the source with the reception of at least k descriptions thus the encoder is allowed to sample only one realization of this breakdown process during the entire transmission for gaussian sources we have the following interesting result when any k descriptions arrive the achievable distortion exactly matches the optimal distortion rate performance corresponding to a source rate of kr bits with the reception of any m k descriptions the source reconstruction quality is strictly better the improvement being nearly linear in the number of descriptions received

successive wyner ziv coding scheme and its application to the quadratic gaussian ceo problem in this paper we introduce a distributed source coding scheme called successive wyner ziv coding we show that every point in the rate region of the quadratic gaussian ceo problem can be achieved via successive wyner ziv coding the concept of successive refinement in single source coding is generalized to the distributed source coding scenario which we refer to as distributed successive refinement for the quadratic gaussian ceo problem we establish a necessary and sufficient condition for distributed successive refinement where the successive wyner ziv coding scheme plays an important role

finding the observed information matrix when using the em algorithm a procedure is derived for extracting the observed information matrix when the em algorithm is used to find maximum likelihood estimates in incomplete data problems the technique requires computation of a complete data gradient vector or second derivative matrix but not those associated with the incomplete data likelihood in addition a method useful in speeding up the convergence of the em algorithm is developed two examples are presented

multiple access channels with memory with and without frame synchronism the capacity region of frame synchronous and frame asynchronous discrete two user multiple access channels with finite memory is obtained frame synchronism refers to the ability of the transmitters to send their code words in unison the absence of frame synchronism in memoryless multiple access channels is known to result in the removal of the convex hull operation from the expression of the capacity region it is shown that when the channel has memory frame asynchronism rules out nonstationary inputs to achieve any point in the capacity region thereby allowing only coding strategies that involve cooperation in the frequency domain but not in the time domain this restriction drastically reduces the capacity region of some multiple access channels with memory and in particular the total capacity of the channel which is invariant to frame asynchronism for memoryless channels

on the use of historical control data to estimate dose response trends in quantal bioassay new tests for trend in proportions in the presence of historical control data are proposed one such test is a simple score statistic based on a binomial likelihood for the current study and beta binomial likelihoods for each historical control series a closely related trend statistic based on estimating equations is also proposed trend statistics that allow overdispersed proportions in the current study are also developed including a version of tarone s 1982 biometrics 38 215 220 test that acknowledges sampling variation in the beta distribution parameters and a trend statistic based on estimating equations each such trend test is evaluated with respect to size and power under both binomial and beta binomial sampling conditions for the current study and illustrations are provided

capacity region of the asynchronous gaussian vector multiple access channel in this paper we derive explicit expressions for the capacity region of the two user symbol asynchronous gaussian vector multiple access channel verdu considered the case where each user linearly modulates a fixed waveform in each symbol period where the symbol periods for the users are not perfectly aligned at the receiver he derived explicit capacity region expressions for the case where the transmitters have knowledge of the mutual offset and also for the case where the transmitters have no knowledge of the mutual offset in this paper we extend verdu s results to allow each user to linearly modulate a set of orthonormal waveforms instead of a single waveform in each symbol period and with no restrictions imposed on the waveforms we consider group power constraints which include individual sum power constraints as orthonormal waveforms assigned to each user may come from different frequency bands with different power constraints similar to the case where each user is allowed to linearly modulate only a single waveform our results hold regardless of whether or not the transmitters are frame synchronous in addition we present some results that are necessary to numerically compute the capacity region expressions with general purpose convex optimization algorithms next we simplify the capacity region expression when there are only individual sum power constraints and when the transmitters know the mutual offset we also prove a sufficient condition for a similar simplification to hold when the transmitters have no knowledge of the mutual offset finally we consider a specialized algorithm to numerically compute the simplified capacity region expression when the transmitters know the mutual offset