Binary Signature Research Articles

Estimated bit-error probability of DS-SSMA/MPSK with coherent detector on satellite mobile channel

In this paper we estimate the average bit-error probability of a direct-sequence spread-spectrum multiple-access (DS-SSMA) system using MPSK and a linear coherent detector on the satellite mobile channel (SMC). The formulas derived in this paper are suitable for various types of signature sequences and chip waveforms. The numerical results are presented for DS-SSMA using BPSK and QPSK with random signature sequences and three different chip waveforms: the rectangular, the cosine, and the root Nyquist filter (RNF) with rolloff rate, /spl beta/=0.4. The results show that the performance of a DS-SSMA system with complex random signature sequences is superior to a system using binary random signature sequences on Gaussian and Rician (K=10) channels, while on flat fading Rayleigh channels the performance for both systems is similar. In DS-SSMA, the RNF has the highest bandwidth efficiency of the three chip waveforms. The performance of DS-SSMA is also analyzed on the SMC using the Gaussian approximation (GA) method. Compared to the estimated results, GA gives a pessimistic approximation for binary random signature sequences on Gaussian and Rician channels.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Performances of acquisition schemes for CDMA systems with complex signature sequences

This paper investigates the acquisition performance of code-division multiple-access communication systems using deterministic complex signature sequences. Unlike most earlier studies, performances are obtained in the presence of multiple user interference, and the results can be applied to complex as well as binary signature sequences. Two serial search acquisition schemes are considered. The first scheme assumes that there is no data in the reference user's signal until the acquisition is achieved. The second scheme allows data modulation in the reference user's signal during the acquisition process. Probability of detection and probability of false alarm of both schemes are obtained without using the Gaussian approximation. Instead, a discrete approximation of the probability density function of the MUI is used in performance evaluations. Numerical results are presented for example sets of Gold, 4-phase, and FZC sequences. They show that complex and binary sequences have comparable acquisition performances. Results also show significant degradation of acquisition performances as the number of users increases.

OFF-LINE VERIFICATION OF JAPANESE SIGNATURES AFTER ELIMINATION OF BACKGROUND PATTERNS

A system of off-line signature verification composed of a preprocessing stage and a verification stage is proposed in this paper. It is assumed that each signature is written on a surface with a background pattern and a sample of the background pattern is available. The preprocessing stage to eliminate the background pattern from a signature image consists of 5 steps: the position adjustment between a signature image and a background image, the filtering of the background pattern by local maximization, the clipping of random noises from the background pattern, the background elimination by transformation of the multilevel signature image to a binary signature image through subtraction and thresholding, and the smoothing for defects recovery and isolated noise elimination. The effect of the preprocessing operation is illustrated in figures. The verification stage following the preprocessing stage is based on the Arc Pattern Method proposed in Ref. 7. An experiment is performed to examine the performance of the proposed system. Twenty Japanese autographs, for which 20 authentic signatures, 10 genuine counter signatures and 10 forged counter signatures are provided, are used in the experiment. The experiment achieved an error rate of as low as approximately 14%.

A chaotic direct-sequence spread-spectrum communication system

The use of chaotic sequences as spectral spreading sequences in direct-sequence spread-spectrum (DS/SS) communication systems is proposed. The error probabilities of such systems are investigated and shown to be, for all practical purposes, identical to the conventional DS/SS systems which use binary signature sequences. Among the advantages of the use of chaotic sequences in DS/SS are the availability of a great number of them, the ease of their generation, as well as their inherent improvement in the security of transmission. >

ODS: ordering DNA sequences--a physical mapping algorithm based on simulated annealing.

In the program ODS we provide a methodology for quickly ordering random clones into a physical map. The process of ordering individual clones with respect to their position along a chromosome is based on the similarity of binary signatures assigned to each clone. This binary signature is obtained by hybridizing each clone to a panel of oligonucleotide probes. By using the fact that the amount of overlap between any two clones is reflected in the similarity of their binary signatures, it is possible to reconstruct a chromosome by minimizing the sum of linking distances between an ordered sequence of clones. Unlike other programs for physical mapping, ODS is very general in the types of data that can be utilized for chromosome reconstruction. Any trait that can be scored in a presence--absence manner, such as hybridized synthetic oligonucleotides, restriction endonuclease recognition sites or single copy landmarks, can be used for analysis. Furthermore, the computational requirements for the construction of large physical maps can be measured in a matter of hours on work-stations such as the VAX2000.

Performance bounds for DS/SSMA communications with complex signature sequences

A unified performance analysis of direct-sequence spread-spectrum multiple-access (DS/SSMA) communications with deterministic complex signature sequences is presented. The probability density function (PDF) of the multiple-user interference is determined. Using a round-down and round-up procedure on the PDF, arbitrarily tight lower and upper bounds on the probability of bit error (PBE) are obtained. Results based on the Gaussian approximation method are also presented. It is shown that complex sequences can yield better PBE performance than binary sequences. Using complex sequences, the number of signature sequences that have good auto- and cross-correlation properties is greatly enlarged. New users employing complex or binary signature sequences can be added to existing systems with graceful performance degradation. >

Equilibrium and non-equilibrium complex fragment emission in 50–100 MeV/u 139La + 12C reactions

Abstract Complex fragment emission ( Z > 2) has been studied in the reactions of 50, 80, and 100 MeV/u 139 La + 12 C. Charge, angle, and energy distributions were measured inclusively and in coincidence with other complex fragments, and were used to extract source rapidities, velocity distributions, and cross sections. The binary signature of the coincidence events and the sharpness of the velocity distributions illustrate the primarily 2-body nature of these reactions. Calculations based on statistical compound nucleus decay have been compared with the experimental data. The emission velocities, angular distributions, and absolute cross sections of fragments of 20 ⩽ Z ⩽ 35 at 50 MeV/u, 19 ⩽ Z ⩽ 28 at 80 MeV/u, and 17 ⩽ Z ⩽ 21 at 100 MeV/u are consistent with the binary decay of compound nuclei formed in incomplete fusion reactions in which the 139 La projectile picks up about one-half of the 12 C target. At 80 and 100 MeV/u, statistical model calculations are also able to reproduce the isotropic portion of the cross section for lighter and heavier fragments. However, a significant fraction of the total cross section for these fragments is due to non-equilibrium emission. Although the emission process is still mainly binary, and the relative velocity between the fragments is determined by their mutual Coulomb repulsion, the anisotropic angular distributions and the magnitudes of the absolute yields are incompatible with standard compound-nucleus statistical decay.

Range image acquisition with a single binary-encoded light pattern

The problem of strike identification in range image acquisition systems based on triangulation with periodically structured illumination is discussed. A coding scheme is presented based on a single fixed binary encoded illumination pattern, which contains all the information required to identify the individual strikes visible in the camera image. Every sample point indicated by the light pattern is made identifiable by means of a binary signature, which is locally shared among its closest neighbors. The applied code is derived from pseudonoise sequences, and it is optimized so that it can make the identification fault-tolerant to the largest extent. A prototype measurement system based on this coding principle is presented. Experimental results obtained with the measurement system are also presented. >

Similarity search for a 1H-NMR spectroscopic data base

A similarity-search system is described for proton-NMR spectroscopy. In order to achieve fast retrieval of reference compounds, the 1H-NMR spectra of the data base and of the unknown are encoded in a bitsring. The individual bits of the binary signature describe different features of the spectra. Part of the coupling information is coded in such a way that effects of magnetic field strength are taken into account. The encoding thus permits a fast search for identical and structurally similar reference compounds in the data base even when the spectra were recorded at different magnetic field strengths. Because the search consists of weighted comparison of bits, each of them describing different spectral features, a choice of different kinds of searches is possible with the same signature by selecting appropriate weight vectors. Thus specific spectroscopic features can be selected for the search. Such a context-sensitive similarity-search system allows, for example, a search for compounds having similar multiplicities or similar subspectra in a given (e.g., aromatic) region of the spectrum. Furthermore, by adjusting two “software knobs” which influence the normalization of the search results, the user can choose between the two extremes of forward and reverse search, and between an identity search, similarity search or classification search. The results were tested on a small library containing 550 spectra including some mixtures and duplicates recorded under different experimental conditions at 250 and 400 MHz.