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Color coding has been experimentally demonstrated to be able to extend the depth of field (DoF) of an imaging system in single snapshot. A numerical model is adopted in this paper to quantitatively characterize its imaging properties (strehl ratio, point spread function and modulation transfer function). To improve the system’s performance under nonuniform spectrum, we proposed to introduce wavefront coding into the system. Numerical results show that wavefront coding acts as an average filter of the spectrum, so that it is able to get an almost invariant MTF across the focal line even under nonuniform spectrum, which is desirable in many applications. [ABSTRACT FROM AUTHOR]

This paper proposes novel Raptor-aware link adaptation (LA) when application layer Forward Error Correction (AL-FEC) with Raptor codes is used for live, high quality, video unicast over mobile broadband networks. The use of Raptor code AL-FEC is taken into account for the adaptation of the modulation and coding scheme (MCS) used in the physical layer. A cross-layer optimization approach is used to select the Raptor code parameters and the MCS mode jointly, in order to maximize transmission efficiency. The proposed methodology takes into consideration the channel resources required to accommodate the Raptor overheads. Simulation results show that packet loss is eliminated and the amount of radio resource required is reduced significantly. Automatic repeat request (ARQ) based unicast systems require up to 115.6 percent more channel resources, by comparison to the proposed Raptor-aware LA system without retransmissions. Furthermore, the Raptor-aware LA system can enhance the link budget by up to 4 dB, increasing coverage in LoS locations, and can improve total goodput by 46.7 percent compared to an ARQ-based system. [ABSTRACT FROM AUTHOR]

A safety evaluation of SMART adopting a fully passive safety system was performed for a small-break loss of coolant accident (SBLOCA) with various break locations and sizes using the MARS code. It is necessary for SMART, adopting a fully passive safety system composed of passive safety injection system (PSIS), automatic depressurization system (ADS), and passive residual heat removal system (PRHRS), to satisfy the passive safety performance requirements, i.e., the capability to maintain safe shutdown conditions for a minimum of 72 h without AC power supply or operator action in the case of a design basis accident. A number of SBLOCAs of different locations and sizes were analyzed using the MARS code. The results of the break spectrum analyses showed that the collapsed liquid level inside the core support barrel is maintained high enough above the top of the core owing to the sufficient passive safety injection flow from the core makeup tank (CMT) and safety injection tank (SIT). Therefore, the core is not uncovered for 72 h after the break without AC power supply or operator action, resulting in a continuous decrease of fuel cladding temperature throughout the transient. [ABSTRACT FROM AUTHOR]

Highlights: [•] Benchmark study performed for the neutronic calculations of TRIGA research reactors. [•] WIMSD-5B/CITATION is the utilized code system along with the WIMSD-IAEA-69 library. [•] The studied condensed spectra are five and seven energy groups spectra. [•] Analyzed: lattice parameters, reactivities, CR worth, flux and power distribution. [•] The lattice and neutronic parameters showed the accuracy of both condensed spectra. [Copyright &y& Elsevier]

Optical frequency combs are innovative tools for broadband spectroscopy because a series of comb modes can serve as frequency markers that are traceable to a microwave frequency standard. However, a mode distribution that is too discrete limits the spectral sampling interval to the mode frequency spacing even though individual mode linewidth is sufficiently narrow. Here, using a combination of a spectral interleaving and dual-comb spectroscopy in the terahertz (THz) region, we achieved a spectral sampling interval equal to the mode linewidth rather than the mode spacing. The spectrally interleaved THz comb was realized by sweeping the laser repetition frequency and interleaving additional frequency marks. In low-pressure gas spectroscopy, we achieved an improved spectral sampling density of 2.5 MHz and enhanced spectral accuracy of 8.39 × 10-7 in the THz region. The proposed method is a powerful tool for simultaneously achieving high resolution, high accuracy, and broad spectral coverage in THz spectroscopy. [ABSTRACT FROM AUTHOR]

Abstract: In this paper we propose a simple divided spectrum balanced detection (DSBD) for spectral amplitude coding (SAC) optical code division multiple access (OCDMA) systems. SAC OCDMA systems are limited by phase induced intensity noise (PIIN), which is a signal dependent source of noise. Our proposed technique reduces the PIIN by dividing the spectrum of the signal into two or more, and detecting each spectrum by a different photodiode. The DSBD scheme reduces the detected optical power at photodetection, thus resulting in a higher mitigation of the PIIN. Theoretical results show that DSBD demonstrate noticeable improvement over traditional balanced detection technique, for example an up to 33% increase in the number of active users can be achieved, and at least 1×10−3 b/sHz increase in the spectral efficiency is obtained. However, the SDBD is more complex and append more constrains on system components. [Copyright &y& Elsevier]

Context. The large amount of spectra obtained during the epoch of extensive spectroscopic surveys of Galactic stars needs the development of automatic procedures to derive their atmospheric parameters and individual element abundances. Aims. Starting from the widely-used code MOOG by C. Sneden, we have developed a new procedure to determine atmospheric parameters and abundances in a fully automatic way. The code FAMA (Fast Automatic MOOG Analysis) is presented describing its approach to derive atmospheric stellar parameters and element abundances. The code, freely distributed, is written in Perl and can be used on di erent platforms. Methods. The aim of FAMA is to render the computation of the atmospheric parameters and abundances of a large number of stars using measurements of equivalent widths (EWs) as automatic and as independent of any subjective approach as possible. It is based on the simultaneous search for three equilibria: excitation equilibrium, ionization balance, and the relationship between log n(Fe i) and the reduced EWs. FAMA also evaluates the statistical errors on individual element abundances and errors due to the uncertainties in the stellar parameters. The convergence criteria are not fixed "a priori" but are based on the quality of the spectra. Results. In this paper we present tests performed on the solar spectrum EWs that assess the method's dependency on the initial parameters and we analyze a sample of stars observed in Galactic open and globular clusters. [ABSTRACT FROM AUTHOR]

Abstract: We demonstrate that a previously proposed model opens the route for the inclusion of refined non-Voigt profiles in spectroscopic databases and atmospheric radiative transfer codes. Indeed, this model fulfills many essential requirements: (i) it takes both velocity changes and the speed dependences of the pressure-broadening and -shifting coefficients into account. (ii) It leads to accurate descriptions of the line shapes of very different molecular systems. Tests made for pure H2, CO2 and O2 and for H2O diluted in N2 show that residuals are down to of the peak absorption, (except for the untypical system of H2 where a maximum residual of ±3% is reached), thus fulfilling the precision requirements of the most demanding remote sensing experiments. (iii) It is based on a limited set of parameters for each absorption line that have known dependences on pressure and can thus be stored in databases. (iv) Its calculation requires very reasonable computer costs, only a few times higher than that of a usual Voigt profile. Its inclusion in radiative transfer codes will thus induce bearable CPU time increases. (v) It can be extended in order to take line-mixing effects into account, at least within the so-called first-order approximation. [Copyright &y& Elsevier]

A common algorithm for the computation of eigenvalues of real symmetric tridiagonal matrices is the iteration of certain special maps Fσ called shifted QR steps. Such maps preserve spectrum and a natural common domain is , the manifold of real symmetric tridiagonal matrices conjugate to the diagonal matrix Λ. More precisely, a (generic) shift defines a map . A strategy specifies the shift to be applied at T so that Fσ(T)=Fσ(T)(T). Good shift strategies should lead to fast deflation: some off-diagonal coordinate tends to zero, allowing for reduction of the problem to submatrices. For topological reasons, continuous shift strategies do not obtain fast deflation; many standard strategies are indeed discontinuous. Practical implementation only gives rise systematically to bottom deflation, convergence to zero of the lowest off-diagonal entry b(T). For most shift strategies, convergence to zero of b(T) is cubic, |b(Fσ(T))|=Θ(|b(T)|k) for k=3. The existence of arithmetic progressions in the spectrum of T sometimes implies instead quadratic convergence, k=2. The complete integrability of the Toda lattice and the dynamics at non-smooth points are central to our discussion. The text does not assume knowledge of numerical linear algebra. [ABSTRACT FROM PUBLISHER]

Highlights: [•] We have proposed a new Diagonal Eigenvalue Unity (DEU) code with ideal in-phase CC based on Jordan block. [•] Cross correlation is not larger than one. [•] Any positive integer number of weight can be used. [•] Numerical results compared to MQC, MFH and MDW codes show significant improvement when DEU code is used. [ABSTRACT FROM AUTHOR]

Chaotic dynamical systems are increasingly considered for use in coding and transmission systems. This stems from their parameter sensitivity and spectral characteristics. The latter are relevant for channel estimation methods. In particular, the logistic map fλ = λx(1 - x) has been employed in chaotic coding and spread spectrum transmission systems. For λ = 4, the statistical properties of sequences generated by f4 are considered as ideal drive signals for channel estimation schemes. This assumption is proven in the present paper. To this end, the higher order statistical moments and the autocorrelation of time series generated by f4 are derived. It is shown that for λ = 4 the zero mean time series is uncorrelated. The adaptation performance of finite impulse response (FIR) digital adaptive filters (DAF) used for channel estimation is analyzed. It is shown that using zero mean sequences of f4 leads to the maximal possible FIR DAF performance. An optimal value for the damping parameter in the LMS scheme is derived that leads to the maximal performance and ensures stability. The analytic considerations are confirmed by simulation results. [ABSTRACT FROM AUTHOR]

In cooperative spectrum sharing-based cognitive radio systems, the secondary user (SU) acts as a cooperator of the primary user (PU) to assist the PU's transmission and is allowed to simultaneously transmit at the same spectrum only if it is not harmful to the primary transmission. Here the authors studies a power minimising problem of the SU with real-time services for this system under constraints on the SU's quality-of-service requirement and guaranteeing the PU's instantaneous rate unchanged if the SU allocates part of its power for its own transmissions. Superposition coding (SC) is further employed by the SU to eliminate the interference caused by the PU. The problem is formulated as an optimisation problem. Owing to its high complexity, this problem is then converted into a single variable optimisation problem, and a greedy-based power minimisation method with low complexity is thus proposed. Numerical comparison shows that the proposed method can lead to reductions in the secondary transmission power of about 30 and 14% against for the non-SC one and the equal bit allocation-based one, respectively. [ABSTRACT FROM AUTHOR]

This study describes the construction of a dicode pulse-position modulation (PPM) system and presents, for the first time, the spectrum of dicode PPM obtained from a practical coder. Original theoretical and computer predicted results agree well with the experimental observations and this shows the accuracy of the method. [ABSTRACT FROM AUTHOR]

Abstract: We describe the implementation of K-shell core level spectroscopies (X-ray absorption (XAS), X-ray emission (XES), and X-ray photoemission (XPS)) in the real-space-grid-based Projector Augmented Wave (PAW) GPAW code. The implementation for XAS is based on the Haydock recursion method avoiding computation of unoccupied states. The absolute energy scale is computed with the Delta Kohn–Sham method which is possible using specific PAW setups for the core-hole states. We show computed spectra for selected test cases (gas phase H2O and bulk diamond) and discuss the dependence on grid spacing and box size. In the case of diamond we include vibrational effects by sampling spectra from the ground state vibrational distribution and discuss the importance of those effects for the experimentally observed features. We apply the method to XPS, XES and XAS of CO adsorbed on Ni(100) and compare to experimental data where possible. [Copyright &y& Elsevier]

This paper considers the high-rate performance of source coding for noisy discrete symmetric channels with random index assignment (IA). Accurate analytical models are developed to characterize the expected distortion performance of vector quantization (VQ) for a large class of distortion measures. It is shown that when the point density is continuous, the distortion can be approximated as the sum of the source quantization distortion and the channel-error induced distortion. Expressions are also derived for the continuous point density that minimizes the expected distortion. Next, for the case of mean squared error distortion, a more accurate analytical model for the distortion is derived by allowing the point density to have a singular component. The extent of the singularity is also characterized. These results provide analytical models for the expected distortion performance of both conventional VQ as well as for channel-optimized VQ. As a practical example, compression of the linear predictive coding parameters in the wideband speech spectrum is considered, with the log spectral distortion as performance metric. The theory is able to correctly predict the channel error rate that is permissible for operation at a particular level of distortion. [ABSTRACT FROM AUTHOR]

Neurons in the primary visual cortex, V1, are specialized for the processing of elemental features of the visual stimulus, such as orientation and spatial frequency. Recent fMRI evidence suggest that V1 neurons are also recruited in visual perceptual memory; a number of studies using multi-voxel pattern analysis have successfully decoded stimulus-specific information from V1 activity patterns during the delay phase in memory tasks. However, consistent fMRI signal modulations reflecting the memory process have not yet been demonstrated. Here, we report evidence, from three subjects, that the low V1 BOLD activity during retention of low-level visual features is caused by competing interactions between neural populations coding for different values along the spectrum of the dimension remembered. We applied a memory masking paradigm in which the memory representation of a masker stimulus interferes with a delayed spatial frequency discrimination task when its frequency differs from the discriminanda with ±1 octave and found that impaired behavioral performance due to masking is reflected in weaker V1 BOLD signals. This cross-channel inhibition in V1 only occurs with retinotopic overlap between the masker and the sample stimulus of the discrimination task. The results suggest that memory for spatial frequency is a local process in the retinotopically organized visual cortex. [ABSTRACT FROM AUTHOR]

Abstract: The HZETRN deterministic radiation code is one of several tools developed to analyze the effects of harmful galactic cosmic rays (GCR) and solar particle events on mission planning and shielding for astronauts and instrumentation. This paper is a comparison study involving the two Monte Carlo transport codes, HETC–HEDS and FLUKA and the deterministic transport code, HZETRN. Each code is used to transport an ion from the 1977 solar minimum GCR spectrum impinging upon a 20g/cm2 aluminum slab followed by a 30g/cm2 water slab. This research is part of a systematic effort of verification and validation to quantify the accuracy of HZETRN and determine areas where it can be improved. Comparisons of dose and dose equivalent values at various depths in the water slab are presented in this report. This is followed by a comparison of the proton and forward, backward and total neutron flux at various depths in the water slab. Comparisons of the secondary light ion 2H, 3H, 3He and 4He fluxes are also examined. [Copyright &y& Elsevier]

design is said to be super-simple if the intersection of any two blocks has at most two elements. A super-simple design $${\mathcal{D}}$$ with point set X, block set $${\mathcal{B}}$$ and index λ is called completely reducible super-simple (CRSS), if its block set $${\mathcal{B}}$$ can be written as $${\mathcal{B}=\bigcup_{i=1}^{\lambda} \mathcal{B}_i}$$, such that $${\mathcal{B}_i}$$ forms the block set of a design with index unity but having the same parameters as $${\mathcal{D}}$$ for each 1 ≤ i ≤ λ. It is easy to see, the existence of CRSS designs with index λ implies that of CRSS designs with index i for 1 ≤ i ≤ λ. CRSS designs are closely related to q-ary constant weight codes (CWCs). A ( v, 4, q)-CRSS design is just an optimal ( v, 6, 4) code. On the other hand, CRSS group divisible designs (CRSSGDDs) can be used to construct q-ary group divisible codes (GDCs), which have been proved useful in the constructions of q-ary CWCs. In this paper, we mainly investigate the existence of CRSS designs. Three neat results are obtained as follows. Firstly, we determine completely the spectrum for a ( v, 4, 3)-CRSS design. As a consequence, a class of new optimal ( v, 6, 4) codes is obtained. Secondly, we give a general construction for (4, 4)-CRSSGDDs with skew Room frames, and prove that the necessary conditions for the existence of a (4, 2)-CRSSGDD of type g are also sufficient except definitely for $${(g,u)\in \{(2,4),(3,4),(6,4)\}}$$. Finally, we consider the related optimal super-simple ( v, 4, 2)-packings and show that such designs exist for all v ≥ 4 except definitely for $${v\in \{4,5,6,9\}}$$. [ABSTRACT FROM AUTHOR]

The problem of guessing a random string is revisited. A close relation between guessing and compression is first established. Then it is shown that if the sequence of distributions of the information spectrum satisfies the large deviation property with a certain rate function, then the limiting guessing exponent exists and is a scalar multiple of the Legendre-Fenchel dual of the rate function. Other sufficient conditions related to certain continuity properties of the information spectrum are briefly discussed. This approach highlights the importance of the information spectrum in determining the limiting guessing exponent. All known prior results are then re-derived as example applications of our unifying approach. [ABSTRACT FROM AUTHOR]

The non-linear filtering is a commonly used time-domain technique for narrowband interference (NBI) suppression in the direct-sequence spread spectrum (DSSS) communication systems. In this study, the authors analyse how the decision feedback error of the spread spectrum (SS) signal influences the performance of the NBI prediction. A partial-code-aided scheme is proposed, which despreads partial chips in a spreading sequence and reconstructs the rest part by spreading the bit decision. This method utilises partial spreading gain to improve the decision accuracy of the SS signals while keeping similar time consumption and implementation complexity with the traditional scheme. It has been verified by simulation that with different NBI models and under different channel conditions, the proposed non-linear filtering method always outperforms the traditional one with chip-wise decision feedback. [ABSTRACT FROM AUTHOR]

Abstract: A common computation in visual cortex is the divisive normalization of responses by a pooled signal of the activity of cells within its neighborhood. From a geometrical point of view, normalization constraints the population response to high-contrast stimuli to lie on the surface of a high-dimensional sphere. Here we study the implications this constraint imposes on the representation of a circular variable, such as the orientation of a visual stimulus. New results are derived for the infinite dimensional case of a homogeneous populations of neurons with identical tuning curves but different orientation preferences. An important finding is that the ability of the population to discriminate between any two orientations depends exclusively on the Fourier amplitude spectrum of the orientation tuning curve. We also study the problem of encoding by a finite set of neurons. A central result is that, under normalization, optimal encoding can be achieved by a finite number of neurons with heterogeneous tuning curves. In other words, increasing the number of neurons in the population does not always allow for an improved population code. These results are used to estimate the number of neurons involved in the coding of orientation at one position in the visual field. If the cortex were to code orientation optimally, we find that a small number (∼4) of neurons should suffice. [ABSTRACT FROM AUTHOR]

Many spectral analysis and modification techniques require the separation of sinusoidal from nonsinusoidal signal components of a Fourier spectrum. Techniques exist for the estimation of the parameters of nonstationary sinusoids, and for discriminating these from other components, within a single Fourier frame. We present a comparative study of five methods for sinusoidal discrimination, considering their effectiveness and their computational cost. [ABSTRACT FROM AUTHOR]

Abstract  We introduce notions of local and interweight spectra of an arbitrary coloring of a Boolean cube, which generalize the notion of a weight spectrum. The main objects of our research are colorings that are called perfect. We establish an interrelation of local spectra of such a coloring in two orthogonal faces of a Boolean cube and study properties of the interweight spectrum. Based on this, we prove a new metric property of perfect colorings, namely, their strong distance invariance. As a consequence, we obtain an analogous property of an arbitrary completely regular code, which, together with his neighborhoods, forms a perfect coloring. [ABSTRACT FROM AUTHOR]

Objects vary not only in their shape but also in the material from which they are made. Knowledge of the material properties can contribute to object recognition as well as indicate properties of the object (e.g. ripeness of a fruit). We examined the coding of images of materials by single neurons of the macaque inferior temporal (IT) cortex, an area known to support object recognition and categorization. Stimuli were images of 12 real materials that were illuminated from three different directions. The material textures appeared within five different outline shapes. The majority of responsive IT neurons responded selectively to the material textures, and this selectivity was largely independent of their shape selectivity. The responses of the large majority of neurons were strongly affected by illumination direction. Despite the generally weak illumination-direction invariance of the responses, Support Vector Machines that used the neural responses as input were able to classify the materials across illumination direction better than by chance. A comparison between the responses to the original images and those to images with a random spectral phase, but matched power spectrum, indicated that the material texture selectivity did not depend merely on differences in the power spectrum but required phase information. [ABSTRACT FROM AUTHOR]

As a high-rate alternative of impulse radio (IR) ultra-wideband (UWB) communications, analog and digital multicarrier UWB radios with coherent detection have been introduced. In this paper, we investigate digital multicarrier differential (MCD) modulation and demodulation schemes for UWB communications. In our approach, the differential encoding and decoding are carried out across multiple digital carriers in the frequency do- main. Hence, channel estimation is bypassed by using neighboring carriers as reference carriers. Compared with the transmitted reference TR-UWB which relies on delaying and correlating the received signal segments in time domain, our MCD-UWB avoids the need for analog delay elements. In addition, our digital-carrier based approach does not incur any spectrum expansion. We also show that our approach enables variable data rates, and remains operational even in the presence of severe interframe interference (IFI). In addition, the small spacing between differentially encoded carriers ensures that the data rate is not limited by the channel coherence bandwidth. Furthermore, our schemes are flexible in providing variable-rate transmissions. Simulations are also carried out to corroborate our theoretical analysis. [ABSTRACT FROM AUTHOR]

Speech coding techniques capable of generating encoded representations which are robust against channel losses play an important role in enabling reliable voice communication over packet networks and mobile wireless systems. In this paper, we investigate the use ofmultiple description index assignments (MDIAs) for loss-tolerant transmission of line spectral frequency (LSF) coefficients, typically generated by state-of-the-art speech coders.We propose a simulated annealing-based approach for optimizing MDIAs for Markov-model-based decoders which exploit inter- and intraframe correlations in LSF coefficients to reconstruct the quantized LSFs from coded bit streams corrupted by channel losses. Experimental results are presented which compare the performance of a number of novel LSF transmission schemes. These results clearly demonstrate that Markov-model-based decoders, when used in conjunction with optimized MDIA, can yield average spectral distortion much lower than that produced by methods such as interleaving/interpolation, commonly used to combat the packet losses. [ABSTRACT FROM AUTHOR]

We investigate spectrum shaping based on cyclic filtering for coded single-carrier transmission over intersymbol interference (ISI) channels. An optimized precoder is derived for coded single-carrier systems using an iterative linear-minimum-mean-square-error (LMMSE) frequency-domain-equalization (FDE) receiver. Numerical results show that this precoder can provide considerable spectrum-shaping gain. [ABSTRACT FROM AUTHOR]

A new polarization-diversity configuration was pro- posed and demonstrated for all-optical, polarization-insensitive clock recovery using a mode-locked laser diode. The system was easily achieved only by adding an adequate length of polarization-maintaining fiber to a conventional polarization-dependent clock recovery setup. Stable clock recovery with small polarization dependence less than 0.5 dB was successfully achieved remaining at low timing jitter of less than 0.17 ps with no significant changes in the pulse characteristics. We also succeeded in the stable clock recovery for the input of polarization-scrambled data signals. [ABSTRACT FROM AUTHOR]

Abstract  In this paper we study the trace spectra of polynomial bases for $${\mathbb{F}}_{2^{n}}$$ over $${\mathbb{F}}_{2}$$ . Shparlinski showed that there exists a polynomial basis having O(log n) elements of trace one. Here we show that for every t ≤ n, there exists a polynomial basis having t O(log n) elements of trace one. We also study consequences of our results to the existence of irreducible polynomials of certain weights. [ABSTRACT FROM AUTHOR]

Real-time video applications require tight bounds on end-to-end delay. Hierarchical bidirectional prediction requires buffering frames in the encoder input buffer, thereby contributing to encoder input delay. Long-term frame prediction with pulsed quality requires buffering at the encoder output, increasing the output buffer delay. Both hierarchical B-pictures and pulsed-quality coders involve uneven bit-rate allocation. Both the encoder and decoder buffering requirements depend on the rate allocation. We derive an efficient rate allocation for hierarchical B-pictures using the power spectral density of a wide-sense stationary process. In addition, we discuss important aspects of hierarchical predictive coding, such as the effect of the temporal prediction distance and delay tradeoffs for prediction branch truncation. Finally, we investigate experimentally the tradeoff between delay and compression efficiency. [ABSTRACT FROM AUTHOR]

Transform-based lossy compression has a huge potential for hyperspectral data reduction. Hyperspectral data are 3-D, and the nature of their correlation is different in each dimension. This calls for a careful design of the 3-D transform to be used for compression. In this paper, we investigate the transform design and rate allocation stage for lossy compression of hyperspectral data. First, we select a set of 3-D transforms, obtained by combining in various ways wavelets, wavelet packets, the discrete cosine transform, and the Karhunen-Loève transform (KLT), and evaluate the coding efficiency of these combinations. Second, we propose a low-complexity version of the KLT, in which complexity and performance can be balanced in a scalable way, allowing one to design the transform that better matches a specific application. Third, we integrate this, as well as other existing transforms, in the framework of Part 2 of the Joint Photographic Experts Group (JPEG) 2000 standard, taking advantage of the high coding efficiency of JPEG 2000, and exploiting the interoperability of an international standard. We introduce an evaluation framework based on both reconstruction fidelity and impact on image exploitation, and evaluate the proposed algorithm by applying this framework to AVIRIS scenes. It is shown that the scheme based on the proposed low-complexity KLT significantly outperforms previous schemes as to rate-distortion performance. As for impact on exploitation, we consider multiclass hard classification, spectral unmixing, binary classification, and anomaly detection as benchmark applications. [ABSTRACT FROM AUTHOR]

The information-spectrum analysis made by Han for classical hypothesis testing for simple hypotheses is extended to a unifying framework including both classical and quantum hypothesis testing. The results are also applied to fixed-length source coding when loosening the normalizing condition for probability distributions and for quantum states. We establish general formulas for several quantities relating to the asymptotic optimality of tests/codes in terms of classical and quantum information spectra. [ABSTRACT FROM AUTHOR]

We evaluate the asymptotic normalized average distributions, of a class of combinatorial configurations in random, regular and irregular, binary low-density parity-check (LDPC) code ensembles. Among the configurations considered are trapping and stopping sets. These sets represent subsets of variable nodes in the Tanner graph of a code that play an important role in determining the height and point of onset of the error-floor in its performance curve. The techniques used for deriving the spectra include large deviations theory and statistical methods for enumerating binary matrices with prescribed row and column sums. These techniques can also be applied in a setting that involves more general structural entities such as subcodes and/or minimal codewords, that are known to characterize other important properties of soft-decision decoders of linear block codes. [ABSTRACT FROM AUTHOR]

Wyner-Ziv video coding (WZVC) has gained considerable interests in the research community. In this paper, we present a model to examine the WZVC performance and compare it with conventional motion-compensated prediction (MCP) based video coding. Theoretical results show that although WZVC can achieve as much as 6-dB gain over conventional video coding without motion search, it still falls 6 dB or more behind current best MCP-based INTER-frame video coding. We further study the use of subpixel and multireference motion search methods to improve WZVC efficiency. The analytical results are confirmed by simulations and experiments. [ABSTRACT FROM AUTHOR]

High-rate direct-sequence spread spectrum is a modulation technique in which most or all of the spreading is provided by nonbinary data modulation. For applications to mobile ad hoc wireless networks, the limited processing gain of high-rate direct-sequence spread spectrum gives only modest protection against multiple access or multipath interference, which limits the applicability of the modulation technique to fairly benign channels. In this paper, we explore the increased interference-rejection capability that can be obtained from convolutional coding with Viterbi decoding, Reed-Solomon coding with errors-and-erasures decoding, and block product coding with iterative decoding. For channels with multiple access or multipath interference, performance results are given for several soft-decision decoding metrics, the benefits of adaptive-rate coding are illustrated, and the accuracy and utility of the Gaussian approximation are described. We also show how to use the bit-error probability for a system without error-control coding to determine which modulation method will give the best packet-error probability in a system with error-control coding. [ABSTRACT FROM AUTHOR]

We propose an indoor wireless infrared downlink scheme for high-data-rate multiuser connectivity with diffuse channels. The scheme is based on synchronous code-division multiple access with unipolar Hadamard codes. The orthogonality of unipolar Hadamard codes enables multiuser operation with relatively short codes. Thus, practical downlink rates of tens of Mb/s for each user can be obtained. However, multipath reflections in diffuse channels cause strong multipath dispersion and, consequently, severe distortion. This distortion becomes even more severe in a multiuser environment, as the dispersed incoherent infrared radiation of all users aggregates together. To mitigate this distortion, we use a novel adaptive multilevel serial composite decision feedback and feedforward equalizer. We investigate the system's performance with the proposed equalizer, and compare it with the performance of the same system, both composite decision-feedback and feedforward equalizers, and with a conventional decision-feedback equalizer (DFE). Our results show that the proposed scheme enables a high-data-rate multiaccess link and eliminates most of the multiuser distortion. Furthermore, it improves system performance in a multiaccess environment, as compared with the other composite equalizers and DFE for the same complexity. We also compare other coding schemes, and show that Hadamard codes are on top of the other codes. [ABSTRACT FROM AUTHOR]

Space-time coding techniques can be used to achieve very high spectral efficiencies in highly scattering environments using multiple transmit and receive antennas. At the remote station, there is usually a more limited space allotted to the antenna array than at the base station. Since the spectral efficiency improves with the number of antennas, one is interested in how many antennas can be crammed into the limited space on the remote station. This paper (Part I of II) addresses some of the issues which affect the allowable density of antennas in the remote station. In particular, the mutual impedance between antenna elements in the remote array and the correlation between the signal and noise fields received by these elements are analyzed for their impact on the channel capacity achievable by such arrays. In particular, we assume the transmitter is radiating from nT elements of uncoupled half-wave dipoles and knows nothing of the channel. A formula is given for the maximum channel capacity to a receiving array of nR elements, coupled to each other in the presence of ambient noise or interference with a uniform angle of arrival distribution. This formula neglects amplifier noise in the receivers. It is shown that the channel capacity is already determined at the terminals of the receiving array, and can not be improved by internal coupling networks following the receiving array. When the propagation is by means of full three-dimensional scattering, the channel capacity is unaffected by mutual coupling in the receiving array. [ABSTRACT FROM AUTHOR]

Multimode coding is an efficient block coding technique that introduces control over sequence statistics by generating a number of alternatives to represent the source word in each encoding interval and then selecting the word that best meets the system constraints. The power spectral density (PSD) of the encoded signal is of particular interest with these codes. Standard techniques for evaluation of the PSD of block coded sequences cannot be directly applied to a wide variety of multimode codes in which encoder state probabilities do not reach a stationary distribution, or in which codeword selection is random when two or more alternatives satisfy system constraints. In the paper standard spectral analysis techniques are extended to enable evaluation of the PSD of signals generated by multimode codes with these characteristics. It is demonstrated that randomness in selection can result in suppression of discrete components in the encoded signal that may otherwise arise under adverse conditions. [ABSTRACT FROM AUTHOR]

Carlet and Charpin classified the set of cubic (n - 4)-resilient Boolean functions into four different types with respect to the Walsh spectrum and the dimension of the linear space. Based on the classification of RM(3,6)/RM(1,6), we have completed this classification of cubic (n - 4)-resilient Boolean functions by deriving the corresponding algebraic normal form (ANF) and autocorrelation spectrum for each of the four types. At the same time, we have solved an open problem by proving that all plateaued cubic (n - 4)-resilient Boolean functions have dimension of the linear space equal either to n - 5 or n - 6. [ABSTRACT FROM AUTHOR]

We investigate a data-driven approach to the analysis and transcription of polyphonic music, using a probabilistic model which is able to find sparse linear decompositions of a sequence of short-term Fourier spectra. The resulting system represents each input spectrum as a weighted sum of a small number of "atomic" spectra chosen from a larger dictionary; this dictionary is, in turn, learned from the data in such a way as to represent the given training set in an (information theoretically) efficient way. When exposed to examples of polyphonic music, most of the dictionary elements take on the spectral characteristics of individual notes in the music, so that the sparse decomposition can be used to identify the notes in a polyphonic mixture. Our approach differs from other methods of polyphonic analysis based on spectral decomposition by combining all of the following: a) a formulation in terms of an explicitly given probabilistic model, in which the process estimating which notes are present corresponds naturally with the inference of latent variables in the model; b) a particularly simple generative model, motivated by very general considerations about efficient coding, that makes very few assumptions about the musical origins of the signals being processed; and c) the ability to learn a dictionary of atomic spectra (most of which converge to harmonic spectral profiles associated with specific notes) from polyphonic examples alone-no separate training on monophonic examples is required. [ABSTRACT FROM AUTHOR]

Although widely used in many coding applications, the Modified Discrete Cosine Transform (MDCT) has the drawback of being sensitive to time shifts. With the popular choice of a sine window, we show that it is possible to compute an explicit formulation of this time dependency. Starting from the exact MDCT of a pure sine and a simple interpretation in terms of combined modulations, we propose a regularization method that computes a "pseudo-spectrum" for the set of MDCT coefficients. This pseudo-spectum is shown to provide, at a low computational cost, a good approximation of the local spectrum of the signal, with an improved behavior kith respect to frequency and phase than the classical MDCT spectrum, ie. the absolute value of the coefficients. Amongst other applications, this procedure can be used to reduce some of the artifacts that appear in MDCT-based audio coders at low bit-rates. [ABSTRACT FROM AUTHOR]

In orthogonal frequency division multiplexing (OPDM) systems, the subcarriers are generated by an inverse discrete Fourier transform. In the literature, the spectra of these subcarriers are often represented by a sequence of sinc functions of the same polarity. This is not Consistent with the intercarrier interference (ICI) cancellation properties of polynomial Cancellation coding (PCC) or similar self-ICI cancellation schemes in OFDM This paper shows the spectra of these subcarriers are more accurately represented by a sequence of sinc functions with alternating polarity. It is shown that the spectral rolloff of OFDM signals can be improved by PCC and the resultant OOB power is much reduced. [ABSTRACT FROM AUTHOR]

Because of widespread application in audio and image coding, subband structures are now well understood. Multirate subband implementations provide significant computational advantages while reducing distortion caused by sample rate changes. Some so-called perfect reconstruction systems can even eliminate all aliasing distortion caused by tandeming multirate spectral analysis and synthesis, as is the case in coding applications. Despite the widespread popularity in coding, the potential of multirate subband structures for general purpose spectral analysis seems to be largely overlooked. This paper reviews one such structure--the multirate filter bank--and demonstrates its utility as a spectrum analyzer of signals, with particular emphasis on passive sonar. The main advantage of the multirate filter bank is that it provides adjustable time-frequency resolution, and in fact, is shown to be a generalization of the Discrete Fourier Transform. Issues of aliasing, computation, and latency are discussed and passive sonar data sets are used for illustration. [ABSTRACT FROM AUTHOR]

Proposes a code-matched interleaver design for turbo codes in which a particular interleaver is constructed to match the code weight distribution. Concept of interleaving; Calculation of the distance spectrum of a particular turbo code; Estimation of the influence of different spectral lines on the bit error rate performance.

In this paper, we restudy the covering radius of block codes from an information theoretic point of view by ignoring the combinatorial formulation of the problem. In the new setting, the formula of the statistically defined minimum covering radius, for which the probability mass of uncovered space by M spheres can be made arbitrarily small, is reduced to a minimization of a statistically defined spectrum formula among codeword-selecting distributions. The advantage of the new view is that no assumptions need to be made on the code alphabet (such as finite, countable, etc.) and the distance measure (such as additive, symmetric, bounded, etc.) in the problem transformation, and hence the spectrum formula can be applied in most general situations. We next address a sufficient condition under which uniform codeword-selecting distribution minimizes the spectrum formula. With the condition, the asymptotic minimum covering radius for block codes under J-ary quantized channels and constant weight codes under Hamming distance measure are determined to display the usage of the spectrum formula. [ABSTRACT FROM AUTHOR]

Presents information on a study which examined the totally trellis-matched codes. Description of convolutionally coded partial-response systems; Tabulation of codes with regard to the distance spectrum criterion; Conclusion.

In this paper, a CELP speech coding scheme based on mel-generalized cepstral analysis is proposed. In this scheme, speech spectra can be represented by mel-generalized cepstra, the representation accuracy of the zero and poles of the spectra can be varied continuously from all-pole model to cepstral model, and perceptual characteristics of humans regarding the frequency resolution can be considered. The encoding and decoding processes of the proposed method are expected to be suitable for human perception since perceptual weighting and postfiltering operations can be performed through mel-generalized cepstral coefficients. The proposed scheme and the conventional CELP scheme based on linear prediction were compared subjectively for a bit rate of 4 kbit/s. The results showed that the proposed scheme outperforms the conventional method by about 2 dB for an equivalent Q value. © 2000 Scripta Technica, Electron Comm Jpn Pt 3, 83(5): 32-41 2000 [ABSTRACT FROM AUTHOR]