constrained capacities for faster than nyquist signaling this paper deals with capacity computations of faster than nyquist ftn signaling it shows that the capacity of ftn is higher than the orthogonal pulse linear modulation capacity for all pulse shapes except the sinc ftn signals can in fact achieve the ultimate capacity for the signal power spectral density psd the paper lower and upper bounds the ftn capacity under the constraint of finite input alphabet it is often higher than the capacity for comparable orthogonal pulse systems sometimes it is superior to all forms of orthogonal signaling with the same psd

performance analysis of coded modulation with generalized selection combining in rayleigh fading we consider coded modulation with generalized selection combining gsc for bandwidth efficient coded modulation over rayleigh fading channels our results show that reception diversity with generalized selection combining can conveniently trade off system complexity versus performance we provide a number of new results by calculating the cutoff rate and by deriving analytical upper bounds on symbol interleaved trellis coded modulation tcm and bit interleaved coded modulation bicm with gsc all are verified by simulation we show that our new bounds on tcm with gsc which includes maximum ratio combining and selection combining as special cases are tighter than the previously derived bounds a new asymptotic analysis on the pairwise error probability which can be used as a guideline for designing coded modulation over gsc channels is also given finally we show that bicm with iterative decoding bicm id can achieve significant coding gain over conventional coded modulation in a multiple receiving antenna channel

information field dynamics for simulation scheme construction information field dynamics ifd is introduced here as a framework to derive numerical schemes for the simulation of physical and other fields without assuming a particular subgrid structure as many schemes do ifd constructs an ensemble of nonparametric subgrid field configurations from the combination of the data in computer memory representing constraints on possible field configurations and prior assumptions on the subgrid field statistics each of these field configurations can formally be evolved to a later moment since any differential operator of the dynamics can act on fields living in continuous space however these virtually evolved fields need again a representation by data in computer memory the maximum entropy principle of information theory guides the construction of updated data sets via entropic matching optimally representing these field configurations at the later time the field dynamics thereby become represented by a finite set of evolution equations for the data that can be solved numerically the subgrid dynamics is thereby treated within auxiliary analytic considerations the resulting scheme acts solely on the data space it should provide a more accurate description of the physical field dynamics than simulation schemes constructed ad hoc due to the more rigorous accounting of subgrid physics and the space discretization process assimilation of measurement data into an ifd simulation is conceptually straightforward since measurement and simulation data can just be merged the ifd approach is illustrated using the example of a coarsely discretized representation of a thermally excited classical klein gordon field this should pave the way towards the construction of schemes for more complex systems like turbulent hydrodynamics

an efficient algorithm for soft decision decoding of the 24 12 extended golay code an efficient algorithm for soft decision decoding of the 24 12 extended golay code is described results obtained for white gaussian noise are presented which show that performance is only a few tenths of a decibel away from that of an ideal correlator

reduced complexity sequence estimation using state partitioning a reduced state sequence estimator rsse for linear dispersive channels is described the technique is based on partitioning the set of all channel states in a way that defines a trellis with fewer states the new technique generalizes trellises that were previously obtained by duel hallen and heegard 1989 and eyouboglu and qureshi 1988 while the approach followed by duel hallen results in powers of two state trellises the new technique generates trellises with an arbitrary number of states using the state partitioning approach one could also generalize the trellises obtained by eyouboglu therefore the approach described in this paper provides a better performance complexity tradeoff

optimization of integer wavelet transforms based on difference correlation structures in this paper a novel lifting integer wavelet transform based on difference correlation structure dccs liwt is proposed first we establish a relationship between the performance of a linear predictor and the difference correlations of an image the obtained results provide a theoretical foundation for the following construction of the optimal lifting filters then the optimal prediction lifting coefficients in the sense of least square prediction error are derived dccs liwt puts heavy emphasis on image inherent dependence a distinct feature of this method is the use of the variance normalized autocorrelation function of the difference image to construct a linear predictor and adapt the predictor to varying image sources the proposed scheme also allows respective calculations of the lifting filters for the horizontal and vertical orientations experimental evaluation shows that the proposed method produces better results than the other well known integer transforms for the lossless image compression

an mgf based performance analysis of generalized selection combining over rayleigh fading channels using the notion of the spacing between ordered exponential random variables a performance analysis of the generalized selection combining gsc diversity scheme over rayleigh fading channels is presented and compared with that of the conventional maximal ratio combining and selection combining schemes starting with the moment generating function mgf of the gsc output signal to noise ratio snr we derive closed form expressions for the average combined snr outage probability and average error probability of a wide variety of modulation schemes operating over independently identically distributed i i d diversity paths because of their simple form these expressions readily allow numerical evaluation for cases of practical interest the results are also extended to the case of non i i d diversity paths

performance analysis of generalized sort switch and examine combining examples of low complexity diversity combining schemes are among others the generalized selection combining gsc scheme and the generalized switch and examine combining gsec in this paper we propose a new low complexity combining scheme termed generalized sort switch and examine combining gssec that in a sense can be considered as a hybrid gsc gsec scheme a generic expression for the moment generating function of the gssec output snr in general independent identically distributed fading channels is derived and is then applied to the analysis of its error performance

sequential sequence estimation for multiple channel systems with intersymbol and interchannel interference a vector sequential sequence estimator is proposed for multiple channel systems with both intersymbol interference isi and interchannel interference ici both finite isi ici and infinite isi ici are considered the estimator consists of a multiple dimensional whitened matched filter and a vector sequential decoder the metric of the sequential algorithm is derived and the algorithm s performance is analyzed computer simulation results for a two dimensional finite isi ici channel and a two dimensional infinite isi ici channel are presented analysis and simulation show that the symbol error probability of the vector sequential algorithm is essentially the same as for maximum likelihood sequence estimation using the vector viterbi algorithm while its average computational complexity is much less although computation per symbol is a random variable with the pareto distribution there exists a signal to noise ratio above which the ensemble average computation is bounded an upper bound on this ratio is found

m ary ncfsk with s n selection combining in rician fading the performances of general m ary and binary orthogonal noncoherent frequency shift keying signal plus noise s n receiver structures in slow flat rician fading channels are examined the fading on the diversity branches is assumed to be independent but not necessarily identically distributed for each receiver a symbol error probability expression is derived as a single integral with finite integration limits extensive monte carlo simulation results are presented to validate the analytical expressions the results indicate that unlike previously published results the performance of s n selection combining sc is not always superior to that of classical sc in fading and is dependent on the value of the signal to noise ratio snr the modulation order the diversity order the multipath intensity profile and the fading parameter it is further shown that increasing the number of diversity branches in a s n sc receiver does not necessarily decrease the probability of error if the system is operating in the low snr region the performances of s n sc schemes are also compared with the performances of equal gain combining and square law combining receivers

distributed detection for diversity reception of fading signals in noise a multiple antenna diversity scheme is investigated for digital communications antenna observations are immediately quantized and sent to a fusion center at the fusion center the quantized observations are combined to form a final decision on which symbol was transmitted the optimum reception scheme is described for the case where frequency shift keying is employed and where slow rayleigh fading and gaussian additive noise are present two cases are studied in the first case an accurate estimate of the signal to noise ratio is available at each receiver in the second case estimates are not available results indicate that two or three bit quantizations may be most appropriate further if binary decisions are made at each antenna the performance may not improve if an estimate of the signal to noise ratio is available at each antenna or if two antennas are used instead of one

computational complexity of sequential sequence estimation for intersymbol interference channels the computational complexity of a sequential algorithm sa developed for intersymbol interference isi channels is analyzed to determine the computational complexity the finite state machine that models the channel and white matched filter system of which the sa is a part is interpreted as a special convolutional encoder followed by a binary symbol to q ary symbol mapping it follows that the computational distribution is pareto and that there exists a computational cutoff rate r sub comp for the uncoded data considered the rate is fixed and the r sub comp criterion translates into a signal to noise ratio snr criterion an upper bound on snr sub comp is found analytically by assuming a uniform input distribution iteration equations developed by s arimoto 1976 are adapted to find the true snr sub comp numerically

sequential sequence estimation for channels with intersymbol interference of finite or infinite length a sequential sequence estimator for channels with finite or infinite intersymbol interference isi is proposed it consists of a whitened matched filter followed by a sequential algorithm a key component of a sequential estimator is a suitable metric that accounts for the unequal search depth this metric is derived for the isi channel computer simulations for three different channels show that the sequential sequence estimator has considerably less computational complexity than a maximum likelihood sequence estimator using the viterbi algorithm mlse va while still maintaining the optimum estimation performance of the mlse va a performance not achievable with any reduced state viterbi algorithm

delayed decision feedback sequence estimation the authors delayed decision feedback sequence estimation ddfse for uncoded pam signals is considered estimates on the performance of the algorithm are given and simulation results are provided for several examples a more general form of ddfse applicable to coded modulation systems is also presented as an example detection of trellis coded qpsk quadrature phase shift keyed signals over intersymbol interference channels is discussed

efficient soft input soft output tree detection via an improved path metric tree detection techniques are often used to reduce the complexity of a posteriori probability app detection in multiantenna wireless communication systems in this paper we introduce an efficient soft input soft output tree detection algorithm that employs a new type of look ahead path metric in the process of branch pruning or sorting while conventional path metrics depend only on symbols on a visited path the new path metric accounts for unvisited parts of the tree in advance through an unconstrained linear estimator and adds a bias term that reflects the contribution of as yet undecided symbols by applying the linear estimate based look ahead path metric to an algorithm that selects the best paths for each level of the tree we develop a new soft input soft output tree detector called an improved soft input soft output algorithm iss ma based on an analysis of the probability of correct path loss we show that the improved path metric offers substantial performance gain over the conventional path metric we also demonstrate through simulations that the proposed iss ma can be a promising candidate for soft input soft output detection in high dimensional systems

on the snr penalty of mpsk with hybrid selection maximal ratio combining over i i d rayleigh fading channels closed form expressions that lower and upper bound the penalty of hybrid selection maximal ratio combining relative to maximal ratio combining mrc for m ary phase shift keying mpsk modulation are proved the bounds offer simple to evaluate explicit expressions and are typically within 0 6 db for hybrid systems with diversity order up to eight that use at least two branches yet are independent of signal to noise ratio snr contrary to conclusions conjectured in a previously published paper it is proved that the snr penalty is not a constant independent of snr it is also shown that previous estimates of the performance losses of selection diversity relative to mrc underestimate or lower bound the losses for mpsk modulation systems and that the true loss can be significantly larger than previously believed an upper bound to this loss is also obtained

dimensional reduction of the master equation for stochastic chemical networks the reduced multiplane method chemical reaction networks which exhibit strong fluctuations are common in microscopic systems in which reactants appear in low copy numbers the analysis of these networks requires stochastic methods which come in two forms direct integration of the master equation and monte carlo simulations the master equation becomes infeasible for large networks because the number of equations increases exponentially with the number of reactive species monte carlo methods which are more efficient in integrating over the exponentially large phase space also become impractical due to the large amounts of noisy data that need to be stored and analyzed the recently introduced multiplane method a lipshtat and o biham phys rev lett 93 170601 2004 is an efficient framework for the stochastic analysis of large reaction networks it is a dimensional reduction method based on the master equation which provides a dramatic reduction in the number of equations without compromising the accuracy of the results the reduction is achieved by breaking the network into a set of maximal fully connected subnetworks maximal cliques a separate master equation is written for the reduced probability distribution associated with each clique with suitable coupling terms between them this method is highly efficient in the case of sparse networks in which the maximal cliques tend to be small however in dense networks some of the cliques may be rather large and the dimensional reduction is not as effective furthermore the derivation of the multiplane equations from the master equation is tedious and difficult here we present the reduced multiplane method in which the maximal cliques are broken down to the fundamental two vertex cliques the number of equations is further reduced making the method highly efficient even for dense networks moreover the equations take a simpler form which can be easily constructed using a diagrammatic procedure for any desired network architecture it is shown that the method provides accurate results for the population sizes of the reactive species and their reaction rates

bandwidth efficient coded modulation with optimized linear partial response signals we study the design of optimal signals for bandwidth efficient linear coded modulation previous results show that for linear channels with intersymbol interference isi reduced search decoding algorithms have near maximum likelihood error performance but with much smaller complexity than the viterbi decoder consequently the controlled isi introduced by a lowpass filter can be practically used for bandwidth reduction such spectrum shaping filters comprise an explicit coded modulation for which we seek the optimal design we simultaneously constrain the bandwidth and maximize the minimum euclidean distance between signals we show that under quite general assumptions the problem can be formulated as a linear program and solved with well known efficient optimization techniques numerical results are presented and the performance of the optimal signals measured by their combined bandwidth and noise immunity is analyzed the new codes are comparable to set partition tcm trellis codes tests of an m algorithm decoder confirm this and show that the performance occurs at small detection complexity

soft decoding techniques for codes and lattices including the golay code and the leech lattice two kinds of algorithms are considered 1 if is a binary code of length n a soft decision decoding algorithm for changes an arbitrary point of r n into a nearest codeword nearest in euclidean distance 2 similarly a decoding algorithm for a lattice lambda in r n changes an arbitrary point of r n into a closest lattice point some general methods are given for constructing such algorithms ami are used to obtain new and faster decoding algorithms for the gosset lattice e 8 the golay code the leech lattice

further results on selection combining of binary ncfsk signals in rayleigh fading channels in this paper we provide an analytical performance comparison of various selection combining sc schemes for binary noncoherent frequency shift keying ncfsk signals operating on independent and nonidentically distributed i n d rayleigh fading channels with this motivation we first derive the receiver structure for the optimum sc scheme which combines one out of the available l diversity branches so as to minimize the probability of bit error we show that the optimum sc scheme chooses the diversity branch having the largest magnitude of the logarithm of the a posteriori probability ratio lappr of the transmitted information bit we also show that 1 the optimum noncoherent diversity receiver for binary ncfsk signals is equivalent to combining the lapprs of all the diversity branches 2 the sc scheme proposed by neasmith and beaulieu is a special case of the optimum sc scheme for independent and identically distributed i i d rayleigh fading and 3 for i n d fading with dual diversity i e l 2 the performance of the optimum sc scheme is the same as that of the optimum noncoherent diversity receiver whereas the neasmith and beaulieu sc scheme gives the performance of the suboptimum equal gain combining receiver bit error rate ber results show that at 10 sup 4 ber for i i d rayleigh fading the proposed optimum sc scheme performs better than the existing sc schemes by 0 5 0 9 db for l 3 and by 0 8 1 5 db for l 5 and performs within 0 3 db of the optimum noncoherent diversity receiver for l 3 5 and for i n d rayleigh fading with l 5 the optimum sc scheme gives an additional gain of about 2 0 db over the pierce sc scheme further for i i d rayleigh fading we derive the bit error probability expression for a 3 l selection scheme which combines three branches whose lappr magnitudes are the largest among the available l branches numerical results for this 3 l selection scheme show that for l 5 at a ber of 10 sup 4 combining the three branches with the largest lappr magnitudes yields almost the full performance of the optimum noncoherent diversity receiver whereas for l 7 it is just about 0 2 db away from the latter

virtual branch analysis of symbol error probability for hybrid selection maximal ratio combining in rayleigh fading we derive analytical expressions for the symbol error probability sep for a hybrid selection maximal ratio combining h s mrc diversity system in multipath fading wireless environments with h s mrc l out of n diversity branches are selected and combined using maximal ratio combining mrc we consider coherent detection of m ary phase shift keying mpsk and quadrature amplitude modulation mqam using h s mrc for the case of independent rayleigh fading with equal signal to noise ratio averaged over the fading the proposed problem is made analytically tractable by transforming the ordered physical diversity branches which are correlated into independent and identically distributed i i d virtual branches which results in a simple derivation of the sep for arbitrary l and n we further obtain a canonical structure for the sep of h s mrc as a weighted sum of the elementary seps which are the seps using mrc with i i d diversity branches in rayleigh fading or equivalently the seps of the nondiversity single branch system in nakagami fading whose closed form expressions are well known we present numerical examples illustrating that h s mrc even with l spl lt n can achieve a performance close to that of n branch mrc

generalization of chase algorithms for soft decision decoding of binary linear codes soft decision decoding of binary linear block codes transmitted over the additive white gaussian channel awgn using antipodal signaling is considered a set of decoding algorithms called generalized chase algorithms is proposed in contrast to chase algorithms which require a lfloor d 1 2 rfloor binary error correcting decoder for decoding a binary linear block code of minimum distance d the generalized chase algorithms can use a binary decoder that can correct less than lfloor d 1 2 rfloor hard errors the chase algorithms are particular cases of the generalized chase algorithms the performance of all proposed algorithms is asymptotically optimum for high signal to noise ratio snr simulation results for the 47 23 quadratic residue code indicate that even for low snr the performance level of a maximum likelihood decoder can be approached by a relatively simple decoding procedure

snr of generalized diversity selection combining with nonidentical rayleigh fading statistics a closed form expression for the average signal to noise ratio snr of generalized diversity selection combining using the m largest in instantaneous snr diversity signals for arbitrary m assuming that the rayleigh fading statistics on each diversity branch are identically independently distributed i i d already exists in the literature in this paper a similar closed form expression but for nonidentically distributed statistics is derived this expression specializes to known results such as the average snrs of maximal ratio combining with either i i d or non i i d diversity statistics and that of conventional selection combining csc with i i d diversity statistics in addition it provides for the first time a simple closed form solution to the combined snr of csc with non i i d diversity statistics further the closed form solution for the snr of selecting the m largest diversity signals has negligible computational complexity

on the minimum length error event of minimum euclidean weight let eta denote the length of the shortest error event achieving the minimum detection distance of maximum likelihood signal detection for an impulse response having memory v a family of impulse responses where eta is of order v sup 2 is exhibited this in turn shows that some difficulty can arise in computing the minimum detection distance

joint statistics of partial sums of ordered exponential variates and performance of gsc rake receivers over rayleigh fading channel spread spectrum receivers with generalized selection combining gsc rake reception were proposed and have been studied as alternatives to the classical two fundamental schemes maximal ratio combining and selection combining because the number of diversity paths increases with the transmission bandwidth previous work on performance analyses of gsc rake receivers based on the signal to noise ratio focused on the development of methodologies to derive exact closed form expressions for various performance measures however some open problems related to the performance evaluation of gsc rake receivers still remain to be solved such as the exact performance analysis of the capture probability and an exact assessment of the impact of self interference on gsc rake receivers the major difficulty in these problems is to derive some joint statistics of ordered exponential variates with this motivation in mind we capitalize in this paper on some new order statistics results to derive exact closed form expressions for the capture probability and outage probability of gsc rake receivers subject to self interference over independent and identically distributed rayleigh fading channels and compare it to that of partial rake receivers

inference with minimal gibbs free energy in information field theory non linear and non gaussian signal inference problems are difficult to tackle renormalization techniques permit us to construct good estimators for the posterior signal mean within information field theory ift but the approximations and assumptions made are not very obvious here we introduce the simple concept of minimal gibbs free energy to ift and show that previous renormalization results emerge naturally they can be understood as being the gaussian approximation to the full posterior probability which has maximal cross information with it we derive optimized estimators for three applications to illustrate the usage of the framework i reconstruction of a log normal signal from poissonian data with background counts and point spread function as it is needed for gamma ray astronomy and for cosmography using photometric galaxy redshifts ii inference of a gaussian signal with unknown spectrum and iii inference of a poissonian log normal signal with unknown spectrum the combination of i and ii finally we explain how gaussian knowledge states constructed by the minimal gibbs free energy principle at different temperatures can be combined into a more accurate surrogate of the non gaussian posterior

sequential decoding of convolutional codes in channels with intersymbol interference sequential sequence estimation for communications channels with convolutionally coded input sequences and intersymbol interference isi is proposed the receiver consists of a whitened matched filter wmf and a vector sequential decoder the metric of the vector sequential algorithm sa is derived analytical results for error probability and computational complexity of the sequential decoder are presented the error probability is found to be dominated by the minimum euclidean distance between the possible output sequences and the computational distribution is pareto typical of a sequential decoder the computational cut off code rate r sub comp and its lower bound r sub comp are also derived numerical simulation results of the error probability and the computational complexity are presented comparing with the viterbi algorithm va reveals that the sa essentially has the same error performance as that of the va while its average computational complexity is one to two orders of magnitude less than that of the va

on the symbol error probability of maximum selection diversity reception schemes over a rayleigh fading channel the symbol error probability of two selection schemes namely maximum signal to noise ratio m gamma selection and maximum output mo selection for m ary multidiversity reception over a rayleigh fading channel are discussed the symbol error probability of the mo scheme is lower than that of the m gamma scheme the more diversity receptions that are used the larger is the difference a simple expression of crossover average signal to noise ratio per bit is presented as a guideline for increasing the number of diversity receptions

microdiversity reception of spread spectrum signals on nakagami fading channels an analytical framework to evaluate the performance of different predetection diversity techniques in various mobile radio environments is developed the average bit error rate analysis applies to phase coded spread spectrum systems over nakagami multipath fading channels a simple and practical selection combining rule is considered our numerical results reveal that this new low complexity receiver structure exhibits comparable performance to that of an optimum linear diversity combiner when the channel does not experience severe fading and for small diversity orders conditioned on the situation that all the diversity branches have identical mean signal strengths in this study we also investigate the effect of variations in the mean signal and noise power levels on each of the independent diversity branches this is an important consideration because in practice equal mean signal strengths rarely occur which results in loss of diversity gain we found that the signal plus noise and interference selection model outperforms the traditional signal to interference plus noise ratio selection scheme if the discrepancy between the mean signal strengths are small owing to the statistical nature of the multiple access interference

on computing the minimum distance for faster than nyquist signaling the degradation suffered when pulses satisfying the nyquist criterion are used to transmit binary data at a rate faster than the nyquist rate over the ideal band limited brick wall channel is studied the minimum distance between received signals is used as a performance criterion it is well known that when nyquist pulses i e pulses satisfying the nyquist criterion are sent at the nyquist rate the minimum distance between signal points is the same as the pulse energy the main result is to show that the minimum distance between received signals is the same as the pulse energy for rates of transmission about 25 beyond the nyquist rate which is the best possible result in fact one can even identify the precise error event and signaling rate that causes the minimum distance to be no longer equal to the pulse energy the mathematical formulation of the problem is analyzed

asymptotic performance of hybrid selection maximal ratio combining over fading channels in this letter we study the asymptotic performance of hybrid selection maximal ratio combining hs mrc and postdetection hs equal gain combining hs egc over generalized fading channels for large average signal to noise ratios asnrs by evaluating the asymptotic moment generating function of the hs mrc output snr at high asnr we derive the diversity and coding gains for hs mrc for a large class of modulation formats and versatile fading conditions including different types of fading channels and nonidentical snr statistics across diversity branches our analytical results reveal that the diversity gains of hs mrc and hs egc are equivalent to that of mrc and the difference in the coding gains for different modulation formats is manifested in terms of a modulation factor defined in this letter some new analytical results about effects of the number of combined branches for hs mrc and noncoherent combining loss of hs egc are also provided

correction to comparison of diversity combining techniques for rayleigh fading channels the authors comment that the probability density function pdf of the signal to noise ratio snr for third order selection combining sc3 given by eng kong and milstein see ibid vol 44 p 1117 29 1996 is incorrect a correction is given by presenting a more efficient method of deriving the generalized pdf of the snr essential in the analysis of nth order selection combining

trellis coding for partial response channels we consider trellis coding techniques for improving the reliability of digital transmission over noisy partial response channels such channels are commonly encountered in digital communication systems and also play a role in devices for data recording concentrating on the channels with characteristics 1 mp d we study methods to obtain codes which increase free euclidean distance between permitted sequences of channel outputs and avoid the occurrence of unlimited runs of identical outputs at the expense of some loss in data rate one technique employs the concept of set partitioning the other is based on using convolutional codes designed for maximum free hamming distance in conjunction with a precoder both methods lead to essentially equivalent codes

the intersymbol interference channel lower bounds on capacity and channel precoding loss the discrete time additive gaussian intersymbol interference isi channel with i i d not necessarily gaussian input signals is considered several new and old lower bounds on the capacity are derived in a unified manner by assuming different front end receiver filters in particular the sampled whitened matched filter swmf and the minimum mean squared error decision feedback equalizer mmse dfe filter the features of the bounds are demonstrated and compared in several examples with binary and quaternary input signals it is also shown that the effect of an ideal post cursor or tail cancellation in an information preserving context depends primarily on the front end filter while as is well known ideal post cursor cancellation at the output of the swmf decreases the information the opposite trend is seen when an mmse dfe front filter is considered this observation reflects the basic theoretical obstacles in precoding i e ideal post cursor cancellation in the presence of a pre cursor it is used to assess the inherent loss in terms of information rates as compared to the rates achievable with the hypothetical ideal post cursor cancellation associated with any post cursor cancellation technique such as precoding dfe or other variants when operating in synergy with the mmse dfe front end filter the effect of the front end filter on an ideally interleaved precoded coded modulation system is also addressed

asymptotic error performance of modulation codes in the presence of severe intersymbol interference the minimum distance and hence the asymptotic error probability of trellis modulation codes that have been subjected to severe channel filtering are evaluated a general algorithm is proposed for this purpose and applied to one class of coded modulations using a frequency domain interpretation of the euclidean distance it is shown that under extreme channel band limitations the error event that causes the minimum distance is characterized by a spectral null at dc numerical results show that for filtered continuous phase modulation codes decreasing the modulation index or smoothing the frequency pulse does not improve the error performance for some of these modulations channel filtering can actually improve the minimum distance bandpass and low pass filtering are contrasted the numerical results are explained by power spectrum considerations

comparison of diversity combining techniques for rayleigh fading channels several methods of diversity combining for a rayleigh faded channel are evaluated and compared the methods considered are for coherent reception maximal ratio combining mrc selection combining sc and a generalization of sc whereby the two three signals with the two three largest amplitudes are coherently combined we will call this method second third order sc and denote it sc2 sc3 similar techniques are also investigated for noncoherent reception with equal gain combining egc replacing mrc and noncoherent versions of sc2 and sc3 numerical results indicate that sc2 and sc3 significantly enhances the bit error rate ber performance relative to that achievable with sc and under certain conditions approaches the performance achieved by mrc or egg the performance enhancement of sc2 and sc3 is especially noticable for noncoherent reception where egc is seen to provide the best performance only for low ber values in fact when the ber is 10 sup 3 or greater sc2 and sc3 performed comparably to egg and in some cases performed better than egc

optimum selection combining for m ary signals in frequency nonselective fading channels we present the optimum selection combining sc rule for m ary signals based on the log likelihood ratio llr in frequency nonselective independent and nonidentically distributed fading channels the motivation for using the llr in selecting the diversity branch is that it provides the reliability information of the maximum a posteriori probability decision which minimizes the probability of symbol error we present coherent and noncoherent optimum sc rules with and without fading information that minimize the probability of symbol error it is shown that the optimum sc rule provides a significant power gain over the conventional signal to noise ratio based sc rule and the power gain increases with an increasing number of available diversity branches and decreasing alphabet size we also present suboptimum sc rules that require less computation but provide a power gain close to that provided by the optimum sc rule

optimized selection diversity for rayleigh fading channels this paper considers the choice of the number of diversity branches for minimizing the bit error rate of a selection diversity system using noncoherent binary frequency shift keying modulation for transmission over a rayleigh fading gaussian channel an exact expression for the optimum number of branches l sel ast is given the resulting probability of bit error decreases exponentially with the square root of the energy per bit

receive antenna selection for mimo spatial multiplexing theory and algorithms this paper discusses the problem of receive antenna subset selection in multiple input multiple output spatial multiplexing mimo sm systems we develop selection algorithms for maximizing the channel capacity one algorithm in particular allows tractable statistical analysis of performance we leverage this to prove that the capacity of the system through receive antenna selection is statistically lower bounded by the capacity of a set of parallel independent single input multiple output simo channels each with selection diversity this provides the crucial step in proving the next main result the diversity order achievable through antenna selection is the same as that of the full system the result sets up strong motivation for introducing receive selection in mimo sm systems the remainder of the paper discusses selection algorithms for two popular mimo sm systems namely ordered successive interference cancellation with independently encoded layers and minimum mean square error mmse receiver with joint encoding of data streams extensive monte carlo simulations are presented to validate and demonstrate performance

trellis based scalar vector quantization of sources with memory the trellis based scalar vector quantizer tb svq can achieve the rate distortion performance bound for memoryless sources this paper extends the scope of this quantizer to coding of sources with memory first considered is a simple extension called the predictive tb svq which applies a closed loop predictive coding operation in each survivor path of the viterbi codebook search algorithm although the predictive tb svq outperforms all other known structured fixed rate vector quantizers due to practical reasons it may not approach the rate distortion limit a new quantization scheme motivated by the precoding idea of laroia et al 1993 called the precoded tb svq is also considered the granular gain is realized by the underlying trellis code while the combination of the precoder and the svq structure provides the boundary gain this new quantization scheme is asymptotically optimal and can in principle approach the rate distortion bound for markov sources

new results on selection diversity the performances of selection diversity receiver structures in a slow flat rayleigh fading environment are assessed a number of new and interesting results are obtained binary digital signaling using noncoherent frequency shift keying ncfsk differential phase shift keying dpsk coherent phase shift keying cpsk and coherent frequency shift keying cfsk is considered the traditional analysis the traditional selection diversity model of a selection diversity system is based on choosing the branch with the largest signal to noise snr power ratio while assuming that the noise power is constant across all branches however many practical selection systems choose the branch based on a largest signal plus noise s n selection sample of a filter output this paper comprises accurate analyses of such s n selection systems results show that s n selection systems perform better than predicted by the traditional selection diversity model this is because the former includes the statistical nature of the noise whereas the latter does not the performance difference between the two models increases as the number of diversity branches increases for each of dpsk and cpsk the dual diversity equal gain eg combining and s n selection systems perform identically for each of ncfsk and cfsk receiver structures which are equivalent when there is no diversity perform differently in a diversity environment certain dual diversity s n selection systems give the same performances as eg combining or square law combining the results are contingent upon perfect cophasing for the eg combining in systems where estimates of the combining carrier phases contain noise s n selection outperforms eg combining for dual diversity

analysis of hybrid selection maximal ratio combining in correlated nakagami fading we present an analysis of a hybrid selection maximal ratio combining diversity system over an evenly correlated slow frequency nonselective nakagami fading channel where the correlation coefficient between any pair of the diversity branch gain amplitudes is the same and all average branch signal to noise ratios snrs are equal in this system the l branches with the largest instantaneous snr out of n available branches are selected and combined using maximal ratio combining from the joint characteristic function cf of the instantaneous branch snrs we obtain an expression for the cf of the combiner output snr as a series of elementary cfs the expression can be conveniently used to obtain the symbol error probability of coherent detection of different m ary modulation schemes we illustrate our methodology using m ary phase shift keying as an example

on the minimum distance problem for faster than nyquist signaling the authors reconsider the problem of determining the minimum distance between output sequences of an ideal band limiting channel that are generated by uncoded binary sequences transmitted at a rate exceeding the nyquist rate for signaling rates up to about 25 faster than the nyquist rate it is shown that the minimum distance does not drop below the value which it would have in the ideal case wherein there is not intersymbol interference mathematically the problem is to decide if the best l sup 2 fourier approximation to the constant 1 on the interval sigma pi sigma pi 0 0 with coefficients restricted to be 1 or 0 occurs when all coefficients are zero this is shown to be optimal for 0 802

new precoding for intersymbol interference cancellation using nonmaximally decimated multirate filterbanks with ideal fir equalizers in this paper we propose a new precoding method for intersymbol interference isi cancellation by using non maximally decimated multirate filterbanks unlike the existing preceding methods such as the th and trellis precodings the new preceding i may be independent of the isi channel ii is linear and does not have to implement any modulo operation iii gives the ideal fir equalization at the receiver for any fir isi channel including spectral null channels iv expands the transmission bandwidth in a minimum amount the precoding is built on non maximally decimated multirate filterbanks based on multirate filterbank theory we present a necessary and sufficient condition on an fir isi transfer function in terms of its zero set such that there is a linear fir n spl times m precoder so that an ideal fir equalizer exists where the integers k and n are arbitrarily fixed the condition is easy to check as a consequence of the condition for any given fir isi transfer function not identically 0 there always exist such linear fir precoders moreover for almost all given fir isi transfer functions there exist linear fir precoders with size n spl times n 1 i e the bandwidth is expanded by 1 n in addition to the conditions on the isi transfer functions a method for the design of the linear fir precoders and the ideal fir equalizers is also given numerical examples are presented to illustrate the theory

on symbol error probability bounds for isi like channels some issues with forney s upper and lower bounds 1972 for the symbol error probability in systems with memory e g intersymbol interference channels have been pointed out in the literature we expound on these issues for the upper bound we show that although the most commonly cited proofs are not logically consistent the bound is true for more general conditions the reasoning leading to the lower bound is shown to be flawed and in general to lead to invalid lower bounds we suggest a lower bound based on mazo s bound 1975 as an alternative

mmse diversity combining for wide band digital cellular radio a study of minimum mean square error mmse diversity combining for wide band digital cellular radio designed to combat intersymbol interference isi caused by frequency selective fading is outlined the systems analyzed use binary phase shift keying bpsk quarternary phase shift keying qpsk or 16 level quadrature amplitude modulation 16 qam with cosine rolloff spectral shaping and space diversity with selection maximal ratio or mmse combining a set of performance curves is presented for selected combining schemes showing the influence of the following system parameters the diversity order 1 to 4 the cosine rolloff factor the power delay spectrum with its associated delay spread the signal to interference ratio and the number of modulation levels 2 4 and 16

simulation of stochastic network dynamics via entropic matching the simulation of complex stochastic network dynamics arising for instance from models of coupled biomolecular processes remains computationally challenging often the necessity to scan a model s dynamics over a large parameter space renders full fledged stochastic simulations impractical motivating approximation schemes here we propose an approximation scheme which improves upon the standard linear noise approximation while retaining similar computational complexity the underlying idea is to minimize at each time step the kullback leibler divergence between the true time evolved probability distribution and a gaussian approximation entropic matching this condition leads to ordinary differential equations for the mean and the covariance matrix of the gaussian for cases of weak nonlinearity the method is more accurate than the linear method when both are compared to stochastic simulations

stochastic analysis of complex reaction networks using binomial moment equations the stochastic analysis of complex reaction networks is a difficult problem because the number of microscopic states in such systems increases exponentially with the number of reactive species direct integration of the master equation is thus infeasible and is most often replaced by monte carlo simulations while monte carlo simulations are a highly effective tool equation based formulations are more amenable to analytical treatment and may provide deeper insight into the dynamics of the network here we present a highly efficient equation based method for the analysis of stochastic reaction networks the method is based on the recently introduced binomial moment equations barzel and biham phys rev lett 106 150602 2011 the binomial moments are linear combinations of the ordinary moments of the probability distribution function of the population sizes of the interacting species they capture the essential combinatorics of the reaction processes reflecting their stoichiometric structure this leads to a simple and transparent form of the equations and allows a highly efficient and surprisingly simple truncation scheme unlike ordinary moment equations in which the inclusion of high order moments is prohibitively complicated the binomial moment equations can be easily constructed up to any desired order the result is a set of equations that enables the stochastic analysis of complex reaction networks under a broad range of conditions the number of equations is dramatically reduced from the exponential proliferation of the master equation to a polynomial and often quadratic dependence on the number of reactive species in the binomial moment equations the aim of this paper is twofold to present a complete derivation of the binomial moment equations to demonstrate the applicability of the moment equations for a representative set of example networks in which stochastic effects play an important role

constrained designs for maximum likelihood soft decoding of rm 2 m and the extended golay codes we present algorithms for maximum likelihood soft decoding of the second order reed muller codes rm 2 m and the extended 24 12 8 golay code the decoding procedures are based on a concise representation of appropriately selected cosets of a subcode of the code considered such representation enables application of certain elimination rules a structure called constrained design is established to support the elimination procedures remarkably efficient algorithms are obtainable by this approach the method of elimination is applicable also in combination with existing coset decoding schemes

on optimal shaping of multidimensional constellations a scheme for the optimal shaping of multidimensional constellations is proposed this scheme is motivated by a type of structured vector quantizer for memoryless sources and results in n sphere shaping of n dimensional cubic lattice based constellations because n sphere shaping is optimal in n dimensions shaping gains higher than those of n dimensional voronoi constellations can be realized while optimal shaping for a large n can realize most of the 1 53 db total shaping gain it has the undesirable effect of increasing the size and the peak to average power ratio of the constituent 2d constellation this limits its usefulness for many real world channels which have nonlinearities the proposed scheme alleviates this problem by achieving optimal constellation shapes for a given limit on the constellation expansion ratio or the peak to average power ratio of the constituent 2d constellation results of calderbank and ozarow 1990 on nonequiprobable signaling are used to reduce the complexity of this scheme and make it independent of the data rate with essentially no effect on the shaping gain comparisons with forney s 1989 trellis shaping scheme are also provided

on the complexity of bounded distance decoding for the awgn channel earlier work has derived the storage complexity of the bounded distance decoder bdd for binary channel convolutional codes we extend this work to the gaussian noise channel and to partial response codes we show that the storage requirement spl sim 2 sup 1 r 1 sup t paths for rate r convolutional codes over the binary channel becomes spl sim 2 sup 2rt over the gaussian channel where the decoder must correct t errors thus convolutional coding over the gaussian channel is not only 3 db more energy efficient but its decoding is simpler as well next we estimate the path storage for partial response codes i e real number convolutional codes over the gaussian channel the growth rate depends primarily on the bandwidth of the code a new optimization procedure is devised to measure the maximum storage requirement in gaussian noise for these two code types an analysis based on difference equations predicts the asymptotic storage growth for partial response codes

trellis coded modulation with multidimensional constellations trellis coded modulation schemes using four eight or 16 dimensional constellations have a number of potential advantages over the usual two dimensional schemes a smaller constituent two dimensional constellation easier tolerance to phase ambiguities and a better trade off between complexity and coding gain a number of such schemes are presented and evaluated starting with a variety of multidimensional lattices we show how to select multidimensional constellations how to partition them into subsets how to construct trellis codes using those subsets and how to map hits to constellation points simplifications of the viterbi decoding algorithm are presented we conclude that there are multidimensional trellis coded modulation schemes that perform better for the same complexity than do two dimensional schemes

maximum likelihood sequence detection for intersymbol interference channels a new upper bound on error probability maximum likelihood sequence detection of digital signaling subject to intersymbol interference and additive white gaussian noise is considered a new approach to the error probability analysis results in an upper bound which is tighter than the forney bound in addition in the case of infinite length intersymbol interference a locally convergent bound is shown to hold under fairly general assumptions on the signal autocorrelation

optimum selection combining using the maximum energy criterion for m ary ncfsk in rician fading channels optimum selection combining using the maximum energy osc me criterion for m ary noncoherent frequency shift keying signaling in independent and nonidentically distributed fading channels is examined a weighted maximum energy selection combining wmesc scheme is proposed and found to provide virtually the same symbol error probability as osc me in rician fading channels the wmesc always provides power gain over the classical selection combining regardless of diversity order and signal to noise ratio

binary symbol recovery via ell_ infty minimization in faster than nyquist signaling systems the issue of binary symbol detection in faster than nyquist signaling systems also known as overcomplete frame modulated digital transmission systems is addressed in this paper through convex relaxation the original combinatorial optimization problem is transformed to an l minimization problem following this idea we further propose lp approximation algorithms to efficiently tackle such a convex optimization problem for noiseless case the recoverability of l minimization is analyzed it is shown that the binary symbol vector b can be completely recovered via l minimization if and only if there is a vector in the row space of the transmission matrix located in the same quadrant as b otherwise complete reconstruction via l minimization is hopeless at the same time we give an upper bound to the reconstruction probability for noisy case the reconstruction probability is analyzed via the probability distribution function of indefinite quadratic form in gaussian vectors numerical results are provided to study the detection performance of l minimization it is shown that compared with semidefinite programming algorithm and linear minimum mean squared error lmmse method the proposed l minimization detection achieves a better performance complexity trade off

spectral theory of metastability and extinction in a branching annihilation reaction we apply the spectral method recently developed by the authors to calculate the statistics of a reaction limited multistep birth death process or chemical reaction that includes as elementary steps branching a 2a and annihilation 2a 0 the spectral method employs the generating function technique in conjunction with the sturm liouville theory of linear differential operators we focus on the limit when the branching rate is much higher than the annihilation rate and obtain accurate analytical results for the complete probability distribution including large deviations of the metastable long lived state and for the extinction time statistics the analytical results are in very good agreement with numerical calculations furthermore we use this example to settle the issue of the lacking boundary condition in the spectral formulation

trellis shaping the author discusses trellis shaping a method of selecting a minimum weight sequence from an equivalence class of possible transmitted sequences by a search through the trellis diagram of a shaping convolutional code c sub s shaping gains on the order of 1 db may be obtained with simple four state shaping codes and with moderate constellation expansion the shaping gains obtained with more complicated codes approach the ultimate shaping gain of 1 53 db with a feedback free syndrome former for c sub s transmitted data can be recovered without catastrophic error propagation constellation expansion and peak to average energy ratio may be effectively limited by peak constraints with lattice theoretic constellations the shaping operation may be characterized as a decoding of an initial sequence in a channel trellis code by a minimum distance decoder for a shaping trellis code based on the shaping convolutional code and the set of possible transmitted sequences is then the set of code sequences in the channel trellis code that lie in the voronoi region of the trellis shaping code

stochastic analysis of dimerization systems the process of dimerization in which two monomers bind to each other and form a dimer is common in nature this process can be modeled using rate equations from which the average copy numbers of the reacting monomers and of the product dimers can then be obtained however the rate equations apply only when these copy numbers are large in the limit of small copy numbers the system becomes dominated by fluctuations which are not accounted for by the rate equations in this limit one must use stochastic methods such as direct integration of the master equation or monte carlo simulations these methods are computationally intensive and rarely succumb to analytical solutions here we use the recently introduced moment equations which provide a highly simplified stochastic treatment of the dimerization process using this approach we obtain an analytical solution for the copy numbers and reaction rates both under steady state conditions and in the time dependent case we analyze three different dimerization processes dimerization without dissociation dimerization with dissociation and heterodimer formation to validate the results we compare them with the results obtained from the master equation in the stochastic limit and with those obtained from the rate equations in the deterministic limit potential applications of the results in different physical contexts are discussed

generalized selection combining based on the log likelihood ratio we propose a generalized selection combining gsc scheme for binary signaling in which a subset of diversity branches providing the largest magnitude of log likelihood ratio llr are selected and combined it is shown that the bit error probability with maximum ratio combining mrc or square law combining of l branches is identical to that with llr based gsc of l 2 branches we also propose a simple but suboptimal gsc based on a noncoherent envelope detection and discuss its potential advantages over the conventional signal to noise ratio based gsc and mrc

chase type and gmd coset decodings in this letter chase decoding algorithms are generalized into a family of bounded distance decoding algorithms so that the conventional chase algorithm 2 and chase algorithm 3 become the two extremes of this family consequently more flexibility in the tradeoffs between error performance and decoding complexity is provided by this generalization especially for codes with large minimum distance finally this approach is extended to decoding with erasures

a unified method for evaluating the error correction radius of reliability based soft decision algorithms for linear block codes this paper presents a unified method for evaluating the error correction radii of many reliability based soft decision decoding algorithms for binary linear block codes based on this unified method these decoding algorithms as well as their potential improvements can be compared directly the error correction radius for each of these decoding algorithms is determined by finding the closest point on the boundary of the decision region of the soft decision decoder to the transmitted signal sequence it is shown that this problem can be formulated as a constrained optimization problem although no general closed form expression is possible a simple algorithm that always converges to the optimum solution of this optimization problem is presented based on these results the error correction radii of some well known reliability based soft decision decoding algorithms are revisited and compared

semi infinite programming theory methods and applications starting from a number of motivating and abundant applications in 2 including control of robots eigenvalue computations mechanical stress of materials and statistical design the authors describe a class of optimization problems which are referred to as semi infinite because their constraints bound functions of a finite number of variables on a whole region in 3 5 first and second order optimality conditions are derived for general nonlinear problems as well as a procedure for reducing the problem locally to one with only finitely many constraints another main effort for achieving simplification is through duality in 6 there algebraic properties of finite linear programming are brought to bear on duality theory in semi infinite programming section 7 treats numerical methods based on either discretization or local reduction with the emphasis on the design of superlinearly convergent sqp type methods taking this differentiable point of view this paper can be considered to be complementar

optimal partial decision combining in diversity systems the optimal partial decision combiner is derived and its performance is analyzed and compared to majority voting and selection diversity using binary noncoherent frequency shift keying on a rayleigh faded additive white gaussian noise channel the degradation in the probability of bit error is evaluated when the channel state estimate is imperfect due to parameter quantization awgn and cochannel interference it is demonstrated that the optimal partial decision combiner can provide a simple means for improving performance on channels with limited cochannel interference

a simple and effective precoding scheme for noise whitening on intersymbol interference channels a precoding scheme for noise whitening on intersymbol interference isi channels is presented this scheme is compatible with trellis coded modulation and unlike tomlinson precoding allows constellation shaping it can be used with almost any shaping scheme including the optimal svq shaping as opposed to trellis precoding which can only be used with trellis shaping the implementation complexity of this scheme is minimal only three times that of the noise prediction filter hence effective noise whitening can be achieved by using a high order predictor

average level crossing rate and average outage duration of generalized selection combining the paper presents an analytical methodology for the evaluation of the average level crossing rate and the average outage duration of generalized selection combining more specifically it presents a general approach when this scheme is employed over independent but not necessarily identically distributed fading channels the general approach is then specialized to independent identically distributed rayleigh fading paths selected numerical examples and plots are also provided and discussed

signal codes convolutional lattice codes the coded modulation scheme proposed in this paper has a simple construction an integer sequence representing the information is convolved with a fixed continuous valued finite impulse response fir filter to generate the codeword a lattice point due to power constraints the code construction includes a shaping mechanism inspired by precoding techniques such as the tomlinson harashima filter we naturally term these codes convolutional lattice codes or alternatively signal codes due to the signal processing interpretation of the code construction surprisingly properly chosen short fir filters can generate good codes with large minimal distance decoding can be done efficiently by sequential decoding or for better performance by bidirectional sequential decoding error analysis and simulation results indicate that for the additive white gaussian noise awgn channel convolutional lattice codes with computationally reasonable decoders can achieve low error rate close to the channel capacity

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

an extension of the simplex algorithm for semi infinite linear programming we present a primal method for the solution of the semi infinite linear programming problem with constraint index sets we begin with a detailed treatment of the case whens is a closed line interval in a characterization of the extreme points of the feasible set is given together with a purification algorithm which constructs an extreme point from any initial feasible solution the set of points ins where the constraints are active is crucial to the development we give in the non degenerate case the descent step for the new algorithm takes one of two forms either an active point is dropped or an active point is perturbed to the left or right we also discuss the form of the algorithm when the extreme point solution is degenerate and in the general case when the constraint index set lies in p the method has associated with it some numerical difficulties which are at present unresolved hence it is primarily of interest in the theoretical context of infinite dimensional extensions of the simplex algorithm

binomial moment equations for stochastic reaction systems a highly efficient formulation of moment equations for stochastic reaction networks is introduced it is based on a set of binomial moments that capture the combinatorics of the reaction processes the resulting set of equations can be easily truncated to include moments up to any desired order the number of equations is dramatically reduced compared to the master equation this formulation enables the simulation of complex reaction networks involving a large number of reactive species much beyond the feasibility limit of any existing method it provides an equation based paradigm to the analysis of stochastic networks complementing the commonly used monte carlo simulations

ser and outage of threshold based hybrid selection maximal ratio combining over generalized fading channels the average symbol error rate and outage probability of threshold based hybrid selection maximal ratio combining t hs mrc in generalized fading environments are analyzed a t hs mrc combiner chooses the combined branches according to a predetermined normalized threshold and the strength of the instantaneous signal to noise ratio snr of each branch therefore the number of combined branches is a random variable rather than a fixed number as in conventional hybrid selection maximal ratio combining h s mrc using the moment generating function method a unified analysis of t hs mrc over various slow and frequency nonselective fading channels is presented both independent identically distributed and independent nonidentically distributed diversity branches are considered the derivation allows different m ary linear modulation schemes the theory is illustrated using coherent m ary phase shift keying in nakagami m fading as an example it is shown that previous published results are incorrect

performance limits of m fsk with reed solomon coding and diversity combining this paper examines the asymptotic m spl rarr spl infin performance of m ary frequency shift keying m fsk in multi channels or multiple frequency nonselective slowly fading channels with coding side information and diversity reception in particular reed solomon rs coding is considered in conjunction with the ratio threshold test rtt which generates side information regarding the reliability of received symbols the asymptotic performance of orthogonal signaling in multichannels with maximal ratio combining mrc postdetection equal gain combining egc hybrid selection combining h sc and selection combining sc is derived for an arbitrary statistical fading model and diversity order the derivations reveal that coherent and noncoherent implementations of diversity combining schemes yield the same performance asymptotically in addition the asymptotic results are evaluated assuming a nakagami m fading model and the effect of fading severity diversity order code rate and side information upon the performance of the various diversity combiners is investigated the minimum signal to noise ratio snr required to achieve arbitrarily reliable or error free communication as well as the associated optimal rs code rate are determined for various cases

an efficient dfe a ml suboptimum receiver for data transmission over dispersive channels using two dimensional signal constellations the dfe ml receiver is presented for data transmission systems using qam modulation a substantial improvement in performance results as compared to other one or two stage receiver structures at relatively low computational complexity

evaluation of the multiplane method for efficient simulations of reaction networks reaction networks in the bulk and on surfaces are widespread in physical chemical and biological systems in macroscopic systems which include large populations of reactive species stochastic fluctuations are negligible and the reaction rates can be evaluated using rate equations however many physical systems are partitioned into microscopic domains where the number of molecules in each domain is small and fluctuations are strong under these conditions the simulation of reaction networks requires stochastic methods such as direct integration of the master equation however direct integration of the master equation is infeasible for complex networks because the number of equations proliferates as the number of reactive species increases recently the multiplane method which provides a dramatic reduction in the number of equations was introduced lipshtat and biham phys rev lett 93 170601 2004 the reduction is achieved by breaking the network into a set of maximal fully connected subnetworks maximal cliques lower dimensional master equations are constructed for the marginal probability distributions associated with the cliques with suitable couplings between them in this paper we test the multiplane method and examine its applicability we show that the method is accurate in the limit of small domains where fluctuations are strong it thus provides an efficient framework for the stochastic simulation of complex reaction networks with strong fluctuations for which rate equations fail and direct integration of the master equation is infeasible the method also applies in the case of large domains where it converges to the rate equation results

exploiting faster than nyquist signaling faster than nyquist signaling introduces intersymbol interference but increases the bit rate while preserving the signaling bandwidth for sinc pulses it has been established that with a small increase in the signaling rate beyond the nyquist rate there is no reduction in the minimum euclidean distance for binary signaling we generalize these observations to the family of raised cosine pulses the structure of the error events that reduce the minimum distance is examined and constrained coding ideas are suggested that theoretically allow even faster signaling then we propose ways of achieving these gains practically by designing appropriate constrained codes and through equalization and iterative joint equalization and decoding turbo equalization

practically realizable digital transmission significantly below the nyquist bandwidth proposes a practically realizable digital signaling scheme that requires a bandwidth significantly below the nyquist limit and at the same time achieves the same asymptotic performance as memoryless pam a five step iterative procedure for constructing such schemes is presented and examples that occupy down to about 60 percent of the nyquist bandwidth are demonstrated using this simple procedure practical receiver structures are also briefly discussed

error performance of binary ncfsk in the presence of multiple tone interference and system noise this paper presents a general solution to the problem of calculating the error performance of binary ncfsk systems in the presence of multiple tone interference and system noise the development uses the concepts of circularly symmetric signals and expresses the results in terms of a bessel integral this integral is then evaluated using a rapidly converging fourier bessel series the error in this approximation to the integral is controlled by two parameters which may be adjusted so that the desired accuracy is attained it is determined that in the useful probability of error range and when the total tone power is constrained the error rate increases for an increase in the number of interfering tones in addition for equal amplitude tones the performance is independent of the distribution of the tones within the channel the technique used is also applicable to other detection problems where the threshold is a random variable

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

multistream faster than nyquist signaling we extend mazo s concept of faster than nyquist ftn signaling to pulse trains that modulate a bank of subcarriers a method called two dimensional ftn signaling the signal processing is similar to orthogonal frequency division multiplex ofdm transmission but the subchannels are not orthogonal despite nonorthogonal pulses and subcarriers the method achieves the isolated pulse error performance it does so in as little as half the bandwidth of ordinary ofdm euclidean distance properties are investigated for schemes based on several basic pulses the best have gaussian shape an efficient distance calculation is given concatenations of ordinary codes and ftn are introduced the combination achieves the outer code gain in as little as half the bandwidth receivers must work in two dimensions and several iterative designs are proposed for ftn with outer convolutional coding

non binary and precoded faster than nyquist signaling faster than nyquist ftn signaling is an important method of narrowband coding the concept is extended here to non binary signal constellations these are much more bandwidth efficient than binary ones a powerful method of finding the minimum distance for binary and non binary ftn is presented preceding ftn transmissions with short linear filters proves to be an effective way to gain distance a shannon limit to bit error rate is derived that applies for ftn tests of an m algorithm receiver are performed and compared to this limit