blind equalization and estimation of fir communications channels using fractional sampling we consider the problem of blind estimation and equalization of digital communication finite impulse response fir channels using fractionally spaced samples fractionally sampled data are cyclostationary rather than stationary the problem is cast into a mathematical framework of parameter estimation for a vector stationary process with single input information sequence and multiple outputs by using a time series representation of a cyclostationary process the channel parameters are estimated by first estimating various subchannels using the second and the fourth order cumulant function of the received data and then appropriately aligning and scaling them the estimated channel impulse response is then used to construct a linear equalizer two illustrative simulation examples using four and 16 qam signals are presented where effect of symbol timing phase offset is studied via simulations

finite identification of functions by teams with success ratio 1 2 and above abstract consider a scenario in which an algorithmic machine m is being fed the graph of a computable function m is said to finitely identify just in case after inspecting a finite portion of the graph of it emits its first conjecture which is a program for and it never abandons this conjecture thereafter a team of machines is a multiset of such machines a team is said to be successful just in case each member of some nonempty subset of predetermined size of the team is successful the ratio of the number of machines required to be successful to the size of the team is referred to as the success ratio of the team the present paper investigates the finite identification of computable functions by teams of learning machines the results presented complete the picture for teams with success ratio 1 2 and greater it is shown that at success ratio 1 2 introducing redundancy in the team can result in increased learning power in particular it is established that larger collections of functions can be learned by employing teams of 4 machines and requiring at least 2 to be successful than by employing teams of 2 machines and requiring at least 1 to be successful surprisingly it is also shown that introducing further redundancy at success ratio 1 2 does not yield any extra learning power in particular it is shown that the collections of functions that can be finitely identified by a team of 2m machines requiring at least m to be successful is the same as the collections of functions that can be finitely identified by a team of 4 machines requiring at least 2 to be successful if is even and the collections of functions that can be identified by a team of 2 machines requiring at least 1 to be successful if is odd these latter results require development of sophisticated simulation techniques

dc free coset codes a class of block coset codes with disparity and run length constraints are studied they are particularly well suited for high speed optical fiber links and similar channels where dc free pulse formats channel error control and low complexity encoder decoder implementations are required the codes are derived by partitioning linear block codes the encoder and decoder structures are the same as those of linear block codes with only slight modifications a special class of dc free coset block codes are derived from bch codes with specified bounds on minimum distance disparity and run length the codes have low disparity levels a small running digital sum and good error correcting capabilities

mixed h2 h sampled data output feedback control design for a semi linear parabolic pde in the sense of spatial l norm abstract this paper addresses distributed mixed h 2 h sampled data output feedback control design for a semi linear parabolic partial differential equation pde with external disturbances in the sense of spatial l norm under the assumption that a finite number of local piecewise measurements in space are available at sampling instants a static sampled data output feedback controller is suggested where the sampling interval in time is bounded the local piecewise measurements bring additional difficulty for the exponential stability and performance analysis since the existing poincare wirtinger inequality in 1d spatial domain is not applicable by constructing an appropriate lyapunov krasovskii functional candidate and employing wirtinger s inequalities a variant of poincare wirtinger inequality in 1d spatial domain as well as agmon s inequality it is shown that the suggested static sampled data output feedback controller not only guarantees the output exponential stability of the resulting closed loop pde in the spatial l norm but also ensures the mixed h 2 h performance index defined in the spatial l norm if the sufficient conditions presented in terms of standard linear matrix inequalities lmis are fulfilled the satisfactory and better performance of the suggested sampled data feedback controller is demonstrated by numerical simulation results of an illustrative example

iterative joint optimization of minimal transmit redundancy fir zero forcing precoder equalizer system for mimo isi channel an iterative joint finite impulse response fir zero forcing zf precoder equalizer optimization algorithm for multiple input multiple output intersymbol interference mimo isi channel is proposed the existing joint precoder equalizer design algorithms for mimo isi channels require a guard period which is longer than or equal to the channel order to avoid the interblock interference ibi this longer guard period is a kind of unnecessary redundancy consuming the valuable channel bandwidth based on space time modulated codes stmc this paper proposes the first algorithm for jointly optimizing the fir precoder and equalizer without the guard period constraint hence the precoder equalizer pairs obtained can achieve minimal transmit redundancy isi free communications for complex valued signals this greatly enhances the spectral efficiency for wide band communications the proposed algorithm is performed in an iterative basis sufficient conditions and convergence analysis of this algorithm are presented the resultant precoder and equalizer are proved to be a least square ls optimal solution for each other the simulation results show that substantial performance gain is obtained with the proposed joint optimization algorithm

filter design for mimo sampling and reconstruction we address the problem of finite impulse response fir filter design for uniform multiple input multiple output mimo sampling this scheme encompasses papoulis generalized sampling and several nonuniform sampling schemes as special cases the input signals are modeled as either continuous time or discrete time multiband input signals with different band structures we present conditions on the channel and the sampling rate that allow perfect inversion of the channel additionally we provide a stronger set of conditions under which the reconstruction filters can be chosen to have frequency responses that are continuous we also provide conditions for the existence of fir perfect reconstruction filters and when such do not exist we address the optimal approximation of the ideal filters using fir filters and a minmax l sub 2 end to end distortion criterion the design problem is then reduced to a standard semi infinite linear program an example design of fir reconstruction filters is given

minimum ber block based precoder design for zero forcing equalization an oblique projection framework this work devises a minimum bit error rate ber block based precoder used in block transmission systems with the proposed cascaded zero forcing zf equalizer the study framework is developed as follows for a block based precoder a received signal model is formulated for the two redundancy schemes viz trailing zeros tz and cyclic prefix cp by exploiting the property of oblique projection a cascaded equalizer for block transmission systems is proposed and implemented with a scheme in which the inter block interference ibi is completely eliminated by the oblique projection and followed by a matrix degree of freedom for inter symbol interference isi equalization with the available channel state information at the transmitter side the matrix for isi equalization of the cascaded equalizer is utilized to design an optimum block based precoder such that the ber is minimized subject to the isi free and the transmission power constraints accordingly the cascaded equalizer with the isi free constraint yields a cascaded zf equalizer theoretical derivations and simulation results confirm that the proposed framework not only retains identical ber performance to previous works for cases with sufficient redundancy but also allows their results to be extended to the cases of insufficient redundancy

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

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

fuzzy boundary control design for a class of nonlinear parabolic distributed parameter systems this paper deals with the problem of fuzzy boundary control design for a class of nonlinear distributed parameter systems which are described by semilinear parabolic partial differential equations pdes both distributed measurement form and collocated boundary measurement form are considered a takagi sugeno t s fuzzy pde model is first applied to accurately represent the semilinear parabolic pde system based on the t s fuzzy pde model two types of fuzzy boundary controllers which are easily implemented since only boundary actuators are used are proposed to ensure the exponential stability of the resulting closed loop system sufficient conditions of exponential stabilization are established by employing the lyapunov direct method and the vector valued wirtinger s inequality and presented in terms of standard linear matrix inequalities finally the advantages and effectiveness of the proposed control methodology are demonstrated by the simulation results of two examples

jointly optimized transmitter and receiver fir mimo filters in the presence of near end crosstalk a theory for jointly optimizing transmitter and receiver finite impulse response fir multiple input multiple output mimo filters is developed in the presence of near end crosstalk and additive channel noise independent of the original signal the transfer function of the channel is a known mimo transfer function with finite memory near end crosstalk is included through another mimo transfer function the channel input signal is assumed to be power constrained for a given channel with a maximum allowable average input power the transmitter and receiver fir mimo filters are jointly optimized such that the mean square error mse between the desired and reconstructed signal is minimized an iterative numerical optimization algorithm is proposed when compared to the methods available in the literature the proposed method yields better results due to the joint optimization of the transmitter receiver pair and is applicable to a more general scenario that may include correlated sources and near end crosstalk

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

identification of nonminimum phase systems using higher order statistics a method is presented for identification of linear time variant nonminimum phase systems when only output data are available the input sequence need not be independent but it must be non gaussian with some special properties described in the test the authors model a finite dimensional system as an arma autoregressive moving average rational function of known orders but the special cases of ar ma and all pass models are also considered to estimate the parameters of their model the authors utilize both second and higher order statistics of the output which may be contaminated by additive zero mean gaussian white noise of unknown variance the parameter estimators obtained are proved under mild conditions to be consistent simulations verify the performance of the proposed method in the case of relatively low signal to noise ratios and when there is a model order mismatch

equal diagonal qr decomposition and its application to precoder design for successive cancellation detection in multiple input multiple output mimo multiuser detection theory the qr decomposition of the channel matrix h can be used to form the back cancellation detector in this paper we propose an optimal qr decomposition which we call the equal diagonal qr decomposition or briefly the qrs decomposition we apply the decomposition to precoded successive cancellation detection where we assume that both the transmitter and the receiver have perfect channel knowledge we show that for any channel matrix h there exists a unitary precoder matrix s such that hs qr where the nonzero diagonal entries of the upper triangular matrix r in the qr decomposition of hs are all equal to each other the precoder and the resulting successive cancellation detector have the following properties a the minimum euclidean distance between two signal points at the channel output is equal to the minimum euclidean distance between two constellation points at the precoder input up to a multiplicative factor that equals the diagonal entry in the r factor b the superchannel hs naturally exhibits an optimally ordered column permutation i e the optimal detection order for the vertical bell labs layered space time v blast detector is the natural order c the precoder s minimizes the block error probability of the qr successive cancellation detector d a lower and an upper bound for the free distance at the channel output is expressible in terms of the diagonal entries of the r factor in the qr decomposition of a channel matrix e the precoder s maximizes the lower bound of the channel s free distance subject to a power constraint f for the optimal precoder s the performance of the qr detector is asymptotically at large signal to noise ratios snrs equivalent to that of the maximum likelihood detector mld that uses the same precoder further we consider two multiplexing schemes time division multiple access tdma and orthogonal frequency division multiplexing ofdm we d

cosets of convolutional codes with least possible maximum zero and one run lengths a communication or storage system may use a coset of a binary convolutional code for both symbol synchronization and error control to facilitate symbol synchronization the coset must have a short maximum zero run length l sub max general upper and lower bounds on l sub max were given previously by hole in this correspondence we use these bounds to identify which convolutional codes have cosets with short l sub max for such a code we then show how to determine a coset with the least possible l sub max among all cosets of the code exact expressions for the least possible l sub max of convolutional code cosets are given and examples of such cosets with large free distances are tabulated bounds on l sub max for cosets of block codes are also provided it is indicated how to tighten the bounds for block codes satisfying the one way chain condition we show that the cosets obtained from traditional high rate block code constructions have larger l sub max than cosets of convolutional codes with approximately the same rates in some systems the convolutional code cosets must have short maximum one run lengths as well as short maximum zero run lengths to avoid loss of symbol synchronization it is shown how to determine convolutional codes whose cosets with least possible maximum zero run lengths also have least possible maximum one run lengths

probabilistic inductive inference inductive inference machines construct programs for total recursive functions given only example values of the functions probabilistic inductive inference machines are defined and for various criteria of successful inference it is asked whether a probabilistic inductive inference machine can infer larger classes of functions if the inference criterion is relaxed to allow inference with probability at least p 0 p ex and bc it is shown that any class of functions that can be inferred from examples with probability exceeding 1 2 can be inferred deterministically and that for probabilities p 1 2 there is a discrete hierarchy of inferability parameterized by p the power of probabilistic inference strategies is characterized by equating the classes of probabilistically inferable functions with those classes that can be inferred by teams of inductive inference machines a parallel model of inference or by a third model called frequency inference

a general error correcting code construction for run length limited binary channels a general method is presented for constructing a single error correcting run length limited code for the class of input restricted binary symmetric channels described by the parameters d k where d is the minimum and k the maximum number of consecutive zeros in any allowable channel input sequence upper and lower bounds on the rates of these codes are derived

bezout space time precoders and equalizers for mimo channels the transmitter receiver diversities in p input q output multiple input multiple output mimo channels will play a key role in future high rate wireless communication the major challenge in mimo signal recovery is the mitigation of the inevitable intersymbol interference isi and interchannel interference ici in multipath mimo channels the bezout system theory provides a simple solution for isi ici cancellation and thus can serve as a powerful mathematical foundation for mimo systems if p q and the mimo system h d is left coprime the system is perfectly recoverable via a bezout precoder assuming the channel information is available at the transmitter for a robust channel design a quantitative analysis of signal to noise ratio snr of the optimal bezout equalizer precoder can be derived from the bezout null space compared with the alamouti see ieee j select areas commun vol 16 p 1451 58 oct 1998 space time coding the bezout precoder is shown to be more appealing in slowly time varying channels where the feedback of the channel information induces minor overhead the bezout system can work well jointly with the space time block coding stbc the stbc can be adopted to artificially construct a larger q spl times p q p virtual transfer function without the channel information a necessary and sufficient condition is provided for perfect recoverability pr for the stbc induced virtual mimo systems based on the virtual transfer function both channel independent and channel dependent precoding strategies are feasible via a singular value decomposition svd analysis the bezout precoder can be shown to outperform the orthogonal frequency division multiplexing ofdm precoder in bit error rate ber transmission rate and receiver implementation the interplay of the two design parameters n and spl rho is analyzed to provide a simple guideline for an optimal configuration the combined stbc and bezout equalization techniques offer a broader spectrum of transceiver system configuration to achieve optimal design tradeoff among ber transmission rate and implementation complexity

synchronizable codes for the optical oppm channel random overlapping pulse position modulation oppm sequences result in an unrecoverable error floor on both the probability of erroneous synchronization and the probability of symbol error when only chip synchronization is present it is known however that for a given sequence length m a subset of the set of all possible sequences is synchronizable in the sense that in the absence of noise the receiver can correctly symbol synchronize by observing m or more symbol intervals the authors design finite state machines and codes over a j ary alphabet which produce sequences with the property that every subsequence of length l is synchronizable some of the codes in addition to being synchronizable produce a coding gain for an optical poisson channel the authors introduce joint synchronization and detection algorithms that utilize the memory in the encoded sequences to produce joint estimates of timing and sequences their performance is analyzed through simulations and analytical results

improved coding techniques for preceded partial response channels a coset of a convolutional code may be used to generate a zero run length limited trellis code for a 1 d partial response channel the free squared euclidean distance d sub free sup 2 at the channel output is lower bounded by the free hamming distance of the convolutional code the lower bound suggests the use of a convolutional code with maximal free hamming distance d sub max r n for given rate r and number of decoder states n in this paper we present cosets of convolutional codes that generate trellis codes with d sub free sup 2 d sub max r n for rates 1 5 spl les r spl les 7 9 and d sub free sup 2 d sub max r n for r 13 16 29 32 61 64 the tabulated convolutional codes with r spl les 7 9 were not optimized for hamming distance instead a computer search was used to determine cosets of convolutional codes that exploit the memory of the 1 d channel to increase d sub free sup 2 at the channel output the search was limited by only considering cosets with certain structural properties the r spl ges 13 16 codes were obtained using a new construction technique for convolutional codes with free hamming distance 4 newly developed bounds on the maximum zero run lengths of cosets were used to ensure a short maximum run length at the 1 d channel output

bounds on the symmetric binary cutoff rate for dispersive gaussian channels bounds on the symmetric binary cutoff rate for a pulse amplitude modulated pam signaling over dispersive gaussian channels are evaluated and discussed these easily calculable bounds can be used to estimate the reliable rate of information transmission and the error exponent behavior for binary two level pam schemes operating through a prefiltered additive white gaussian channel the memory of which is long enough to make the exact evaluation of the cutoff rate formidable the core of the bounding technique relies on a probabilistic interpretation of a fundamental theorem in matrix theory regarding the logarithm of the largest eigenvalue of a nonnegative primitive matrix commonly applied in large deviation problems these bounds are calculated for some examples and their respective tightness is considered further potential applications of the proposed bounding technique are pointed out

concatenated codes for class iv partial response channels we present the design and analysis of parallel and serial concatenated codes with iterative decoding for class iv partial response pr4 signaling code rates of the form k sub 0 k sub 0 1 for k sub 0 4 8 16 32 and 64 are considered we show that the 1 1 spl oplus d sup 2 tomlinson precoder first proposed by wolf and ungerboeck 1991 for trellis coded pr4 channels is effective for both parallel and serial concatenations but the error rate floor is relatively high for the serial case this leads to new interleaver and precoder designs for serial concatenations the latter involving an examination of the conditional distance enumerator of each precoded pr4 channel the new precoders substantially reduce the floors of the serial concatenated codes but degrade the performance of the parallel concatenated codes for a bit error rate of 10 sup 5 the best parallel and serial concatenated codes come within 1 7 db of a lower bound on the capacity limit for pr4 signaling on an additive white gaussian noise channel

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

design and analysis of linear precoders under a mean square error criterion part i foundations and worst case designs much debate surrounds the pros and cons of linear precoders in wireless communication systems this two part paper contributes to the debate by formulating the precoder design problem as an optimisation problem and studying the optimal solutions thereby gaining a better understanding of how precoders work and what they can do part i builds a mathematical foundation for the study of linear precoders it is shown that under a mean square error criterion a natural convex geometry arises this geometry facilitates the derivation of a necessary and sufficient condition for a linear precoder to be maximally robust meaning the precoder s worst case performance is no worse than that of any other linear precoder part ii studies precoders having the lowest average mean square error deriving closed form solutions in special cases and developing a stochastic optimisation algorithm for computing optimal precoders in general

comparison of identification criteria for machine inductive inference abstract a natural pl 1 hierarchy of successively more general criteria of success for inductive inference machines is described based on the size of sets of anomalies in programs synthesized by such machines these criteria are compared to others in the literature some of our results are interpreted as tradeoff results or as showing the inherent relative computational complexity of certain processes and others are interpreted from a positivistic mechanistic philosophical stance as theorems in philosophy of science the techniques of recursive function theory are employed including ordinary and infinitary recursion theorems

minimum ber block precoders for zero forcing equalization we determine the linear precoder that minimizes the bit error rate ber at moderate to high signal to noise ratios snrs for block transmission systems with zero forcing zf equalization and threshold detection the design is developed for the two standard schemes for eliminating inter block interference viz zero padding zp and cyclic prefix cp we show that both the zp minimum ber precoder and the cp minimum ber precoder provide substantially lower error rates than standard block transmission schemes such as orthogonal frequency division multiplexing ofdm the corresponding snr gains can be on the order of several decibels we also show that the cp minimum ber precoder can be obtained by a two stage modification of the water filling discrete multitone modulation dmt scheme in which the diagonal water filling power loading is replaced by a full matrix consisting of a diagonal minimum mean square error power loading matrix post multiplied by a discrete fourier transform dft matrix

analysis of zero padded optimal transceivers this paper analyzes both the mean square error mse and the mutual information in block based transceivers that employ zero padding we consider both linear transceivers and decision feedback equalizers dfe that minimize the mse of symbols these systems may enjoy the zero forcing property or not and may use unitary precoder or not we demonstrate mathematically that the mse mutual information related to these transceivers are i monotone increasing decreasing functions of the number of transmitted symbols per block ii monotone decreasing increasing functions of the number of redundant data used in the equalization process of a block and iii increased decreased whenever non minimum phase channels are utilized instead of their minimum phase counterparts assuming that one does not use the whole received data block to estimate the transmitted signal as consequence of the former results we also prove that for both dfe and minimum error probability systems the average error probability of symbols maintains the same monotonic behavior as the average mse of symbols the theoretical results do not include pure minimum mse based systems

static collocated piecewise fuzzy control design of quasi linear parabolic pde systems subject to periodic boundary conditions this paper presents a lyapunov and partial differential equation pde based methodology to solve static collocated piecewise fuzzy control design of quasi linear parabolic pde systems subject to periodic boundary conditions two types of piecewise control i e globally piecewise control and locally piecewise control are considered respectively a takagi sugeno t s fuzzy pde model that is constructed via local sector nonlinearity method is first employed to accurately describe spatiotemporal dynamics of quasi linear pdes based on the t s fuzzy pde model a static collocated piecewise fuzzy feedback controller is constructed to guarantee the locally exponential stability of the resulting closed loop system sufficient conditions for the existence of such fuzzy controller are developed by applying vector valued poincare wirtinger inequality and its variants and a linear matrix inequality lmi relaxation technique these sufficient conditions are presented in terms of standard lmis finally the performance of the suggested fuzzy controller is illustrated by numerical simulation results of a nonlinear pde system described by quasi linear fitzhugh nagumo equation with periodic boundary conditions

a new description of trellis codes a trellis code is a sliding window method of encoding a binary data stream as a sequence of real or complex numbers that are input to a noisy transmission channel ungerboeck has constructed simple trellis codes that provide the same noise immunity as is given by increasing the power of uncoded transmission by factors ranging from two to four his method is to specify an underlying convolutional code and a rule mapping by set partitioning that maps the output of this code onto a fixed signal constallation a new description of a trellis code is given that combines these two steps into one the new description is analytic rather than graphical many practical codes can be described very simply and strict bounds on performance can be obtained a method for differential encoding trellis codes is presented that was suggested by the authors representation

on codes with spectral nulls at rational submultiples of the symbol frequency in digital data transmission respectively storage systems line codes respectively recording codes are used to tailor the spectrum of the encoded sequences to satisfy constraints imposed by the channel transfer characteristics or other system requirements for instance pilot tone insertion requires codes with zero mean and zero spectral density at tone frequencies embedded tracking focus servo signals produce similar needs codes are studied with spectral nulls at frequencies f kf s n where f is the symbol frequency and k n are relatively prime integers with k leq n in other words nulls at rational submultiples of the symbol frequency a necessary and sufficient condition is given for a null at f in the form of a finite discrete fourier transform dft running sum condition a corollary of the result is the algebraic characterization of spectral nulls which can be simultaneously realized specializing to binary sequences we describe canonical mealy type state diagrams directed graphs with edges labeled by binary symbols for each set of realizable spectral nulls using the canonical diagrams we obtain a frequency domain characterization of the spectral null systems obtained by the technique of time domain interleaving

a least squares approach to blind channel identification conventional blind channel identification algorithms are based on channel outputs and knowledge of the probabilistic model of channel input in some practical applications however the input statistical model may not be known or there may not be sufficient data to obtain accurate enough estimates of certain statistics in this paper we consider the system input to be an unknown deterministic signal and study the problem of blind identification of multichannel fir systems without requiring the knowledge of the input statistical model a new blind identification algorithm based solely on the system outputs is proposed necessary and sufficient identifiability conditions in terms of the multichannel systems and the deterministic input signal are also presented

precoded and vector ofdm robust to channel spectral nulls and with reduced cyclic prefix length in single transmit antenna systems the performance of orthogonal frequency division multiplexing ofdm systems may be degraded when intersymbol interference isi channels have spectral nulls also when isi channels have many taps the data rate overhead due to the insertion of the cyclic prefix is high we first propose a precoded ofdm system that may improve the performance of the ofdm systems for spectral null channels we also propose size k spl times x1 vector ofdm vofdm systems that reduce the cyclic prefix length by k times compared to the conventional ofdm systems the precoding scheme is simply to insert one or more zeros between each two sets of k consecutive information symbols although it can be generalized to a general form this precoding scheme may be able to remove the spectral nulls of an isi channel without knowing the isi channel when no zero is inserted between each two sets of k consecutive information symbols and only each k consecutive symbols are blocked together we obtain vofdm systems both theoretical performance analysis and simulation results are presented finally we compare the combination of the vofdm systems and the unitary matrix modulation with the conventional ofdm systems and the phase shift keying modulation where both differential noncoherent and coherent modulations and demodulations are considered

brief paper an lmi approach to h boundary control of semilinear parabolic and hyperbolic systems exponential stability analysis and l 2 gain analysis are developed for scalar uncertain distributed parameter systems governed by semilinear partial differential equations of parabolic and hyperbolic types sufficient exponential stability conditions with a given decay rate are derived in the form of linear matrix inequalities lmis for both systems these conditions are then utilized to synthesize h static output feedback boundary controllers of the systems in question

brief paper sliding mode boundary control of a parabolic pde system with parameter variations and boundary uncertainties this paper considers the stabilization problem of a one dimensional unstable heat conduction system rod modeled by a parabolic partial differential equation pde powered with a dirichlet type actuator from one of the boundaries by applying the volterra integral transformation a stabilizing boundary control law is obtained to achieve exponential stability in the ideal situation when there are no system uncertainties the associated lyapunov function is used for designing an infinite dimensional sliding manifold on which the system exhibits the same type of stability and robustness against certain types of parameter variations and boundary disturbances it is observed that the relative degree of the chosen sliding function with respect to the boundary control input is zero a continuous control law satisfying the reaching condition is obtained by passing a discontinuous signum signal through an integrator

on codes satisfying mth order running digital sum constraints multi level sequences with a spectral null of order m at frequency f meaning that the power spectral density and its first 2m 1 derivatives vanish at f are characterized by finite state transition diagrams fstds whose edge labels satisfy bounds on the variation of the mth order running digital sum rds necessary and sufficient conditions for fstds with higher order null constraints at dc and at an arbitrary submultiple of the symbol frequency are derived analytical results are given concerning the performance of codes satisfying an mth order rds constraint on partial response channels specific code designs for quaternary channel inputs are presented the euclidean distance properties of this new class of codes aside from their spectral shaping properties are demonstrated

punctured convolutional codes for the 1 d partial response channel a coded 1 d system containing a punctured convolutional encoder is analyzed in general a punctured encoder with 2 sup v states results in a decoder trellis with 2 sup v 1 states and a periodically time varying branch structure a class c of punctured convolutional encoders for which the decoder trellis has a fixed branch structure with 2 sup v states is described an encoder in this class can be combined with a precoder to form a new punctured convolutional encoder that generates the output from the precoder the author determines the set of good variable rate trellis codes for selectable rate encoding and viterbi decoding a set of variable rate trellis codes is generated by a variable rate punctured convolutional encoder in c the author also determines punctured convolutional encoders in c that generate a single good high rate trellis code

fractional biorthogonal partners in channel equalization and signal interpolation the concept of biorthogonal partners has been introduced recently by the authors the work presented here is an extension of some of these results to the case where the upsampling and downsampling ratios are not integers but rational numbers hence the name fractional biorthogonal partners the conditions for the existence of stable and of finite impulse response fir fractional biorthogonal partners are derived it is also shown that the fir solutions when they exist are not unique this property is further explored in one of the applications of fractional biorthogonal partners namely the fractionally spaced equalization in digital communications the goal is to construct zero forcing equalizers zfes that also combat the channel noise the performance of these equalizers is assessed through computer simulations another application considered is the all fir interpolation technique with the minimum amount of oversampling required in the input signal we also consider the extension of the least squares approximation problem to the setting of fractional biorthogonal partners

vector coding for partial response channels a linear technique for combining equalization and coset codes on partial response channels with additive white gaussian noise is developed the technique vector coding uses a set of transmit filters or vectors to partition the channel into an independent set of parallel intersymbol interference isi free channels for any given finite or infinite block length the optimal transmit vectors for such channel partitioning are shown to be the eigenvectors of the channel covariance matrix for the specified block length and the gains of the individual channels are the eigenvalues an optimal bit allocation and energy distribution are derived for the set of parallel channels under an accurate extension of the continuous approximation for power in optimal multidimensional signal sets for constellations with unequal signal spacing in different dimensions examples are presented that demonstrate performance advantages with respect to zero forcing decision feedback methods that use the same coset code on the same partial response channel only resampling the channel at an optimal rate and assuming no errors in the feedback path will bring the performance of the decision feedback methods up to the level of the vector coded system

binary convolutional codes with application to magnetic recording calderbank heegard and ozarow 1 have suggested a method of designing codes for channels with intersymbol interference such as the magnetic recording channel these codes are designed to exploit intersymbol interference the standard method is to minimize intersymbol interference by constraining the input to the channel using run length limited sequences calderbank heegard and ozarow considered an idealized model of an intersymbol interference channel that leads to the problem of designing codes for a partial response channel with transfer function 1 d n 2 where the channel inputs are constrained to be pm 1 this problem is considered here channel inputs are generated using a nontrivial coset of a binary convolutional code the coset is chosen to limit the zero run length of the output of the channel and so maintain clock synchronization the minimum squared euclidean distance between outputs corresponding to distinct inputs is bounded below by the free distance of a second convolutional code which we call the magnitude code an interesting feature of the analysis is that magnitude codes that are catastrophic may perform better than those that are noncatastrophic

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

fuzzy state space modeling and robust observer based control design for nonlinear partial differential systems in this paper a robust fuzzy control design is proposed for the stabilization of nonlinear partial differential systems npdss based on galerkin s method a takagi sugeno t s fuzzy pds is first proposed to model an npds then the t s fuzzy pds can be represented by a finite dimensional t s fuzzy subsystem in controlled mode and a coupled infinite dimensional t s fuzzy subsystem in residual mode therefore the npds can be partitioned into a finite dimensional t s fuzzy slow state space subsystem to be controlled and a coupled infinite dimensional fast residual subsystem to be tolerated based on the small gain theorem a robust fuzzy observer based controller is developed to tolerate the coupled residual subsystem to asymptotically stabilize the npds furthermore based on the dissipative theory an hinfin control design is proposed to attenuate the effects of external disturbances and measurement noises on the robust stabilization of npdss the matlab linear matrix inequality toolbox can be employed to efficiently solve the optimal hinfin fuzzy observer based control design problem of npdss finally a simulation example is given to illustrate the design procedure and confirm the performance of the proposed robust fuzzy observer based control method for the perturbative npdss

design and analysis of linear precoders under a mean square error criterion part ii mmse designs and conclusions part i of this two part paper formulated the precoder design problem as an optimisation problem and solved it with respect to a worst case criterion part ii studies a similar optimisation problem but with respect to a criterion measuring average performance a stochastic optimisation algorithm is proposed for solving this problem for special cases closed form solutions are also given these results indicate linear precoders reduce the effects of frequency distortion caused by multipath channels but are powerless to counteract additive white gaussian noise the conclusion is linear precoders should introduce only a small amount of redundancy and be used in conjunction with an error correcting code capable of combatting additive noise

error pattern correcting cyclic codes tailored to a prescribed set of error cluster patterns a new class of cyclic codes is discussed which is highly tailored to a prescribed set of dominant error cluster patterns the cyclic code construction is based on a generator polynomial that produces a distinct syndrome set for each error pattern in the target set by tailoring the generator polynomial specifically to the set of dominant error patterns the code becomes highly effective in handling single and multiple occurrences of dominant error patterns at a very high code rate a list decoding strategy based on a set of test word error events is developed for the proposed codes which efficiently utilizes both the algebraic information from the captured syndrome and the reliability measures provided by the local correlators matched to the dominant error patterns by forcing a decoder to correct a single pattern event for each test input word multiple decoders running in parallel on the list of test words can effectively correct multiple error pattern occurrences within the channel detector output word

new criteria for blind deconvolution of nonminimum phase systems channels a necessary and sufficient condition for blind deconvolution without observing the input of nonminimum phase linear time invariant systems channels is derived based on this condition several optimization criteria are proposed and their solution is shown to correspond to the desired response these criteria involve the computation only of second and fourth order moments implying a simple tap update procedure the proposed methods are universal in the sense that they do not impose any restrictions on the probability distribution of the unobserved input sequence it is shown that in several important cases e g when the additive noise is gaussian the proposed criteria are essentially unaffected

partial spectrum reconstruction using digital filter banks the problem of reconstructing a part of the spectrum is reduced to designing the filter bank to satisfy a set of conditions for the case considered here these conditions cannot be satisfied simultaneously so perfect reconstruction is not possible the necessary and sufficient conditions on the filters so that the resulting filter bank cancels most alias components are found such filter banks are called partial alias cancellation filter banks the product of the polyphase transfer matrices of these filter banks must be a block pseudocirculant matrix an algorithm design procedure is discussed and examples are given to demonstrate the theory

matched information rate codes for partial response channels in this paper we design capacity approaching codes for partial response channels the codes are constructed as concatenations of inner trellis codes and outer low density parity check ldpc codes unlike previous constructions of trellis codes for partial response channels we disregard any algebraic properties e g the minimum distance or the run length limit in our design of the trellis code our design is purely probabilistic in that we construct the inner trellis code to mimic the transition probabilities of a markov process that achieves a high capacity approaching information rate hence we name it a matched information rate mir design we provide a set of five design rules for constructions of capacity approaching mir inner trellis codes we optimize the outer ldpc code using density evolution tools specially modified to fit the superchannel consisting of the inner mir trellis code concatenated with the partial response channel using this strategy we design degree sequences of irregular ldpc codes whose noise tolerance thresholds are only fractions of a decibel away from the capacity examples of code constructions are shown for channels both with and without spectral nulls

filterbank transceivers optimizing information rate in block transmissions over dispersive channels optimal finite impulse response fir transmit and receive filterbanks are derived for block based data transmissions over frequency selective additive gaussian noise agn channels by maximizing mutual information subject to a fixed transmit power constraint both fir and pole zero channels are considered the inherent flexibility of the proposed transceivers is exploited to derive as special cases zero forcing zf and minimum mean square error receive filterbanks the transmit filterbank converts transmission over a frequency selective fading channel affected by additive colored noise into a set of independent flat fading subchannels with uncorrelated noise samples two loading algorithms are also developed to distribute transmit power and number of bits across the usable subchannels while adhering to an upper bound on the bit error rate ber reduction of the signal to noise ratio snr margin required to satisfy the prescribed ber is achieved by coding each subchannel s bit stream the potential of the proposed transceivers is illustrated and compared to discrete multitone dmt with simulated examples

robust fuzzy h_ infty estimator based stabilization design for nonlinear parabolic partial differential systems with different boundary conditions in this paper a new robust fuzzy h infty estimator based stabilization design for a class of n dimensional nonlinear parabolic partial differential systems pdss with either the dirichlet or neumann boundary conditions is proposed first an n dimensional parabolic takagi sugeno t s fuzzy pds is used to approximate the n dimensional nonlinear parabolic pds via the knowledge based t s fuzzy system technique second based on the n dimensional parabolic t s fuzzy pds a robust fuzzy estimator based controller is employed not only to stabilize the pds but also to attenuate the effects of external and measurement noises on the pds in the spatiotemporal domain below a prescribed attenuation level the robust fuzzy h infty estimator based stabilization design problem can be formulated as a diffusion matrix inequality dmi problem to solve dmis via the traditional algebraic matrix techniques we utilize the divergence theorem and the poincare inequality to transform the dmis into bilinear matrix inequalities with a poincare constant defined according to the spatial domain of the corresponding pds finally the robust fuzzy h infty estimator based stabilization design problem can be effectively solved by a set of linear matrix inequalities instead of the bmis with the help of the proposed decoupled method additionally an optimal robust fuzzy h infty estimator based stabilization design can be realized via minimizing the noise attenuation level a simulation example is provided to illustrate the design procedure and verify the performance of the proposed optimal design

the algebraic structure of frequency selective mimo channels the theory of homogenous matrix polynomials provides a clear and powerful framework for the characterization of frequency selective multiple input multiple output mimo channels the concept proposed in this paper is a natural unification of methods known from flat fading mimo channels and frequency selective single input single output siso channels from the kronecker canonical form of the channel equation several subchannels can be identified each of them is related to an elementary divisor or minimal index of the channel the elementary divisors are equivalent to the roots of the characteristic polynomial for siso channels whereas the minimal indices characterize the possible transmit or receive diversity in such channels the knowledge of these values allows us to determine the necessary filter order the minimal redundancy and the conditions on the precoder such that a finite impulse response filter can suppress all intersymbol and interchannel interference completely