Random Sequences

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In this paper, we present a new, computationally efficient simulator for time-varying multi-path (fast fading) vector channels that can be used to evaluate the performance of antenna array wireless receivers at the base station. The development of the simulator is based on the emulation of the spatio-temporal correlation properties of the vector channel. The channel is modeled as a single-input multi-output finite impulse response (FIR) system with time-varying coefficients which are obtained via the application of a space-time correlation shaping transformation on some independent random sequences. The various parts of the new simulator are detailed and channel simulation realizations are presented and commented.

This paper presents an optimized fault diagnosing procedure applicable in Built-in Self-Test environments. Instead of the known approach based on a simple bisection of patterns in pseudorandom test sequences, we propose a novel bisection procedure where the diagnostic weight of test patterns is taken into account. Another novelty is the sequential nature of the procedure which allows pruning the search space. Opposite to the classical approach which targets all failing patterns, in the proposed method not all failing patterns are needed to be fixed for diagnosis. This allows to tradeoff the speed of diagnosis with diagnostic resolution. The proposed method is compared with three known fault diagnosis methods: classical Binary Search, Doubling and Jumping. Experimental results demonstrate the advantages of the proposed method compared to the previous ones.

We describe Syskill & Webert, a software agent that learnsto rate pages on the World Wide Web (WWW), decidingwhat pages might interest a user. The user rates exploredpages on a three point scale, and Syskill & Webert learnsa user profile by analyzing the information on each page.The user profile can be used in two ways. First, it can beused to

Feedback with carry shift registers (FCSR) were introduced by Goresky and Klapper in [3]. They are very similar to classical linear feedback shift registers (LFSR) used in many pseudorandom generators. The main difference is the fact that the elementary additions are not additions modulo 2 but with propagation of carries. The mathematical models for LFSR are equivalently linear recurring sequences over GF (2) or rational series in the set GF (2)[[ ]]. For FCSR, the "good" model is the one of rational 2-adic numbers (cf. [5], [6]). It is well known, that the series generated by a LFSR can be synthesized by either the Berlekamp-Massey algorithm for binary linear recurring sequences or the extended Euclidean algorithm in the set GF (2)[ ] of binary polynomials (cf. [11], [13]). In [5], Goresky and Klapper give an algorithm for the FCSR synthesis. This algorithm is similar to those of Berlekamp-Massey and is based on De Weger and Mahler's rational approximation theory (cf. [10], [14]). In this correspondence, we prove that it is possible to synthesize the FCSR with the extended Euclidean algorithm in the ring of integers. This algorithm is clearly equivalent to the previous one, however, it is simpler to understand, to implement, and to prove. Our algorithm is still valid in the case of-adic integers where is a positive integer. We also give a near-adaptative version of this algorithm.

The universal real constant pi, the ratio of the circumference of any circle and its diameter, has no exact numerical representation in a finite number of digits in any number/radix system. It has conjured up tremendous interest in mathematicians and non-mathematicians alike, who spent countless hours over millennia to explore its beauty and varied applications in science and engineering. The article attempts to record the pi exploration over centuries including its successive computation to ever increasing number of digits and its remarkable usages, the list of which is not yet closed.

Current seismic codes specify design earthquake loads as single events. The structure, however, may experience multiple ground accelerations in a short period of time. The evidence from recent earthquakes confirms this scenario. For instance, the 2004 Niigata earthquake consisted of two acceleration sequences. An earthquake of repeated sequences can cause more damage to the structure than a single ordinary event due to accumulation of inelastic deformations. Meanwhile, information on repeated acceleration sequences is currently limited. This paper proposes a simple stochastic model for representing repeated acceleration sequences. Subsequently, the model is used in investigating the response of nonlinear SDOF structures to random earthquakes of repeated sequences. The ground acceleration is represented as a stationary Gaussian random process modulated by an envelope function of repeated character. The structural response is quantified in terms of the input and hysteretic energies, ductility demand, damage indices and failure probability.

The ability of Orthogonal Frequency Division
Multiplexing (OFDM) systems to achieve higher data rates and
facilitate bandwidth friendly communication [1]-[3] is impaired
by the presence of Carrier Frequency Offset (CFO) in the
OFDM communication system. CFO can be caused by Doppler
frequency shift, or by the differences of the transmitter and the
receiver local oscillator frequencies. We propose a new method
for CFO estimation for (OFDM) communication systems, with
experimental proof which was gathered in the process of real
world data transmission using the OFDM communication system
in a simulation environment (MATLAB)

This brief presents a CMOS burst-mode optical transmitter suitable for use in 1.25-Gb/s Ethernet passive optical network applications. Based on feedback from the monitoring photodiode, in order to control consecutive burst data the proposed transmitter in this brief uses a reset mechanism, which allows fast responses from the beginning of a high-speed input burst. The chip is fabricated in mixed-mode 0.18-m CMOS technology and measurements are implemented in a chip-on-board configuration using a pig-tailed type Fabry-Perot laser. Under burst-mode operation of 1.25-Gb/s pseudorandom binary sequences, measurements show about 1-dBm averaged transmitted optical power with an over 12-dB extinction ratio over a wide temperature range.

An integrated configuration is proposed to convert tunable slow light from signal to another frequency in a wide bandwidth by using a 70 m-long highly nonlinear photonic crystal fiber (HN-PCF). A 10 GHz RZ signal is delayed by a 10 Gbit/s 2 31 1 pseudo random bit sequence (PRBS) stimulated Brillouin scattering (SBS) pump, and the slow light is converted to another frequency in a broadband by four-wave mixing (FWM). By this way, not only the slow light is converted, but the idler power is enhanced greatly. In our experiment, all-optical controlled 37.5 ps delay time is converted in a 40 nm bandwidth flatly, and 4.7 dB idler power is enhanced simultaneously. The experimental results are in good agreement with those of the theory.

This paper introduces simulation of performance evaluation of 40 Gb/s optical fiber communication systems using directly modulated high-speed distributed feedback (DFB) lasers. Electrical signals of return to zero (RZ) and non-return to zero (NRZ) formats with 2 10 -1 pseudorandom bit sequences are used to modulate the laser. A standard single-mode fibers (SSMF) is used. The laser has a blue shift of the lasing frequency and frequency chirps of 65 and 78 GHz under RZ and NRZ formats, which limit the fiber length to 2.51 and 1.37 km. Comparison of the results with those obtained by using a positive non-zero dispersion-shifted fiber (+D-NZDSF) is presented.

Adaptive Random Testing (ART) is a method for improving the fault-finding effectiveness of random testing. Fixed-Size Candidate Set ART is the most studied variant of this approach. However, existing implementations of FSCS-ART have had substantial selection overhead, with n test cases requiring O n 2 time to generate. We describe the use of a geometric data structure known as the Voronoi Diagram to reduce this overhead to no worse than O(n √ n) and, with further optimization, O(n log n). We demonstrate experimentally that practical improvements in selection overhead can be gained using this improved implementation.

In this letter we consider optimum code structure for positive optical code division multiple-access (optical CDMA) systems. Positive systems are a class of systems that operate with positive real numbers only. We consider the effect of multipleaccess interference in our model and show that code design for both On-Off Keying (OOK) and Binary PPM optical CDMA systems results in the same solutions. Furthermore, we show that a class of codes known as optical orthogonal codes (OOCs) are the best possible positive codes. In obtaining the results we define normalized divergence based on signal-to-multipleaccess interference ratio (SIR) for a multiple-access system in a useful manner and use it as our criterion to maximize the multiple-access capability of the codes. Finally, we demonstrate that BPPM/OOC can be considered as the closest counterpart of ±1 pseudorandom sequence in radio CDMA communication systems.

This paper and its companion (Part II) are devoted to the analysis of the application of a chaotic piecewise-linear onedimensional (PL1D) map as random number generator (RNG). Piecewise linearity of the map enables us to mathematically find parameter values for which a generating partition is Markov and the RNG behaves as a Markov information source, and then to mathematically analyze the information generation process and the RNG. In the companion paper we discuss practical aspects of our chaos-based RNGs.

Part I of this paper defines the class of constructive unsupervised on-line learning simplified adaptive resonance theory (SART) clustering networks. Proposed instances of class SART are the symmetric Fuzzy ART (S-Fuzzy ART) and the Gaussian ART (GART) network. In Part II of our work, a third network belonging to class SART, termed fully self-organizing SART (FOSART), is presented and discussed. FOSART is a constructive, soft-to-hard competitive, topology-preserving, minimum-distance-to-means clustering algorithm capable of: 1) generating processing units and lateral connections on an example-driven basis and 2) removing processing units and lateral connections on a minibatch basis. FOSART is compared with Fuzzy ART, S-Fuzzy ART, GART and other well-known clustering techniques (e.g., neural gas and self-organizing map) in several unsupervised learning tasks, such as vector quantization, perceptual grouping and 3-D surface reconstruction. These experiments prove that when compared with other unsupervised learning networks, FOSART provides an interesting balance between easy user interaction, performance accuracy, efficiency, robustness, and flexibility. Index Terms-Absolute and relative membership function, adaptive resonance theory, clustering, Delaunay triangulation, soft-to-hard competitive learning, topology preserving mapping, Voroni partition.

This paper proposes a digital chaotic secure communication by introducing a concept of magnifying glass, which is used to enlarge and observe minor parameter mismatch so as to increase the sensitivity of the system. The encryption method is based on a one-time pad encryption scheme, where the random key sequence is replaced by a chaotic sequence generated via a Chua's circuit. In our system, we make use of an impulsive control strategy to synchronize two identical chaotic systems embedded in the encrypter and the decrypter, respectively. The lengths of impulsive intervals are piecewise constant and as a result, the security of the system is further improved. Moreover, with the given parameters of the chaotic system and the impulsive control law, an estimate of the synchronization time is derived. The proposed cryptosystem is shown to be very sensitive to parameter mismatch and hence the security of the chaotic secure communication system is greatly enhanced.

In this paper we propose a scheme for selforganizing sensor networks; the scheme allows a sensor network to adapt to topological changes, include new batches of sensors, and disregard the sensors that have depleted their power reserves, or have been compromised. The algorithm for self-organization allows the sensor network to carry out its mission, has built-in provisions for information assurance, and extends its lifetime by reducing the power consumption; it minimizes the number of collisions experienced by a sensor when it transmits and maximizes the time a sensor is either idle or dedicated to monitoring and/or internal data processing.

In this paper, we present a new mutation operator called the Systematic Mutation (SM) operator for enhancing the performance of Basic Particle Swarm Optimization (BPSO) algorithm. The SM operator unlike most of its contemporary mutation operators do not use the random probability distribution for perturbing the swarm population, but uses a quasi random Sobol sequence to find new solution vectors in the search domain. The comparison of SM-PSO is made with BPSO and some other variants of PSO. The empirical results show that SM operator significantly improves the performance of PSO.

Fault coverage and test length estimation in circuits under random test is the subject of this paper. Testing by a sequence of random input patterns is viewed as sequential sampling of faults from a given fault universe. Based on this model, the probability mass function @mf) of fault coverage and expressions for all its moments are derived. This provides a means for computing estimates of fault coverage as well as determining the accuracy of the estimates. Test length, viewed, as waiting time on fault coverage, is analyzed next. We derive expressions for its pmf and its probability generating function (pgf). This allows computation of all the higher order moments. In particular, expressions for mean and variance of test length for any specified fault coverage are derived. This is a considerable enhancement of the state of the art in techniques for predicting test length as a function of fault coverage. It is shown that any moment of test length requires knowledge of all the moments of fault coverage, and hence, its pmf. For this reason, expressions for approximating its expected value and variance, for user specified error bounds, are also given. A methodology based on these results is outlined. Experiments carried out on several circuits demonstrate that this technique is capable of providing excellent predictions of test length. Furthermore it is shown, as with fault coverage prediction, that estimates of variances can be used to bound average test length quite effectively.

Stream ciphering is an essential coding method for delay sensitive traffic such as voice and video. In this method the source sequence is combined with the output of a key stream generator using XOR. The strength and robustness of this ciphering method lays in complexity of the key stream generator. A well-known method for generating key stream is pseudo-random number generator, which is based on LFSR. Recently the anti-random sequence has attained attraction and shown to have better statistical properties compared to pseudo-random numbers, so it appears be suitable for stream ciphering. The existing methods for generating anti-random numbers are highly time and memory consuming. This paper presents an approximate method for generating anti-random sequence, which is very simple and does not need large capacity of memory, while preserves the properties of the sequence. Moreover, we show that our method presents enough statistical complexity to fulfill the required security for stream ciphering.

Stream ciphering is an essential coding method for delay sensitive traffic such as voice and video. In this method the source sequence is combined with the output of a key stream generator using XOR. The strength and robustness of this ciphering method lays in complexity of the key stream generator. A well-known method for generating key stream is pseudo-random number generator, which is based on LFSR. Recently the anti-random sequence has attained attraction and shown to have better statistical properties compared to pseudo-random numbers, so it appears be suitable for stream ciphering. The existing methods for generating anti-random numbers are highly time and memory consuming. This paper presents an approximate method for generating anti-random sequence, which is very simple and does not need large capacity of memory, while preserves the properties of the sequence. Moreover, we show that our method presents enough statistical complexity to fulfill the required security for stream ciphering.

Part I of this paper defines the class of constructive unsupervised on-line learning simplified adaptive resonance theory (SART) clustering networks. Proposed instances of class SART are the symmetric Fuzzy ART (S-Fuzzy ART) and the Gaussian ART (GART) network. In Part II of our work, a third network belonging to class SART, termed fully self-organizing SART (FOSART), is presented and discussed. FOSART is a constructive, soft-to-hard competitive, topology-preserving, minimum-distance-to-means clustering algorithm capable of: 1) generating processing units and lateral connections on an example-driven basis and 2) removing processing units and lateral connections on a minibatch basis. FOSART is compared with Fuzzy ART, S-Fuzzy ART, GART and other well-known clustering techniques (e.g., neural gas and self-organizing map) in several unsupervised learning tasks, such as vector quantization, perceptual grouping and 3-D surface reconstruction. These experiments prove that when compared with other unsupervised learning networks, FOSART provides an interesting balance between easy user interaction, performance accuracy, efficiency, robustness, and flexibility. Index Terms-Absolute and relative membership function, adaptive resonance theory, clustering, Delaunay triangulation, soft-to-hard competitive learning, topology preserving mapping, Voroni partition.

This paper addresses the problem of generating constant-envelope wideband (CEW) signals, for which applications are emerging both in telecommunications (as information carriers) and in digital/power electronics (to aid the synthesis of timing signals which favor electromagnetic compliance). A flexible generation technique consists in driving a frequency modulation (FM) modulator with random or chaotic sequences. Mathematical tools for predicting some spectral properties of random-FM and chaotic-FM CEW signals are herein introduced by commenting on recent results and presenting novel ones in a coherent framework.

Abstract| This paper o ers su cient conditions to prove global convergence of non{elitist evolutionary algorithms. If these conditions can be applied they yield bounds of the convergence rate as a by{product. This is demonstrated by an example that can be calculated exactly.

In this paper a fully automatic scheme for embedding visually recognizable watermark patterns to video objects is proposed. The architecture consists of 3 main modules. During the first module unsupervised video object extraction is performed, by analyzing stereoscopic pairs of frames. In the second module each video object is decomposed into three levels with ten subbands, using the Shape Adaptive Discrete Wavelet Transform (SA-DWT) and three pairs of subbands are formed (HL 3 , HL 2 ), (LH 3 , LH 2 ) and (HH 3 , HH 2 ). Next Qualified Significant Wavelet Trees (QSWTs) are estimated for the specific pair of subbands with the highest energy content. QSWTs are derived from the Embedded Zerotree Wavelet (EZW) algorithm and they are high-energy paths of wavelet coefficients. Finally during the third module, visually recognizable watermark patterns are redundantly embedded to the coefficients of the highest energy QSWTs and the inverse SA-DWT is applied to provide the watermarked video object. Performance of the proposed video object watermarking system is tested under various signal distortions such as JPEG lossy compression, sharpening, blurring and adding different types of noise. Furthermore the case of transmission losses for the watermarked video objects is also investigated. Experimental results on real life video objects indicate the efficiency and robustness of the proposed scheme.

Chaotic maps represent an effective method for generating random-like sequences that combines the benefits of relying on simple, causal models with good unpredictability. Regrettably, such positive features are counterbalanced by the fact that statistics of true-implemented chaotic maps are generally strongly dependent on implementation errors and external perturbations. Here we study the effect of an external, additive, map-independent noise perturbation in the map model, and present a technique to guarantee, for a quite large class of maps, independence of the first-order statistics of the noise features.

A bstruct-The theoretical advantages of two-dimensional quantization over univariate quantization have been studied in the literature. However, in many cases there is no known implementation for the two-dimensional quantizer that can operate in real time. A new approach to the design of two-dimensional quantizers is piiisented. This technique, called prequantization, is used to design two-dimensional quantizers that operate in real time. The importance of prequantization is demonstrated by the design of the optimum uniform two-dimensional (hexagonal) quantizer. Additional examples are given to illustrate the flexibility of this design approach.

Two adaptive FIR filter configurations are proposed for implementing the LMS algorithm with no along delay elements or multipliers. The first uses a linear feedback shift register (LFSR) to generate pseudorandom binary sequences for applications where white noise has been traditionally used. The binary signals are delayed by a shift register and multiplied by on/off switching so that the resulting structure is free of analog delay lines and multipliers. For applications where inputs are colored, the second configuration uses a E-A modulator as front-end for converting the adaptive filter's input into a binary sequence. Such a filter tends to adapt itself into a low-pass characteristic to remove the high frequency noise due to the modulator.

We present a method for testing sequential circuits using weighted random sequences. The weights are stored and a weighted random sequence generator is used to produce the required test sequences during testing rather than storing the actual test sequences themselves. The generation of required weights is based on the dynamic scan algorithm, DYNASTEE. Experimental results demonstrate new tradeo s in test application time and in tester memory requirements, while maintaining 100% fault coverage of all target faults.

We investigate a new approach in utilizing a given classification to cellular automata to search for a particular behavior cellular automaton with a genetic algorithm. This investigation leads to the formation of two new concepts. The first is creating a new method to measure randomness in finite binary sequences depending on iterations in patterns. The second is the sculpturing of the term Chromosomity. As defined in this paper, a property is said to be chromosomic (i.e. has chromosomity or shows a genetic behavior) if it can be searched for with a genetic algorithm.

In this paper, a new technique is proposed for blind estimation of carrier frequency offset (CFO) in wireless orthogonal frequency-division multiplexing (OFDM) systems with constant-modulus constellations. The proposed scheme is based on the assumption that the channel slowly changes in the time domain with respect to the OFDM symbol duration. As a consequence, the channel effect on a given subcarrier in two consecutive OFDM symbols is approximately the same. Based on this assumption, a cost function is derived such that the power difference between all subcarriers in two consecutive OFDM symbols is minimized. Using Monte Carlo simulation, we demonstrate that the proposed scheme has superior performance in both static and time-varying frequency-selective fading channels. The proposed system can rapidly and accurately estimate the CFO using only three trial values, given that the CFO is less than half of the subcarriers' frequency spacing.

Solutions to decentralized stochastic optimization problems lead to recursions in which the state space enlarges with the time-horizon, thus leading to non-tractability of classical dynamic programming. A common joint information state supplied to each of the agents leads to a tractable recursion, as is evident in the one-step-delayed information sharing structure case or when deterministic nestedness in information holds when there is a causality relationship as in the case of partially nested information structure. However, communication requirements for such conditions require exchange of very large data noiselessly, hence these assumptions are generally impractical. In this paper, we present a weaker notion of nestedness, which we term as stochastic nestedness, which is characterized by a sequence of Markov chain conditions. It is shown that if the information structure is stochastically nested, then an optimization problem is tractable, and in particular for LQG problems, the team optimal solution is linear, despite the lack of deterministic nestedness or partial nestedness. One other contribution of this paper is that, by regarding the multiple decision makers as a single decision maker and using Witsenhausen's equivalent model for discrete-stochastic control, it is shown that the common state required need not consist of observations and it suffices to share beliefs on the state and control actions; a pattern we refer to as -stage belief sharing pattern. We discuss the minimum amount of information exchange required to achieve such an information pattern for 0018-9286/$26.00 © 2009 IEEE Authorized licensed use limited to: Queens University. Downloaded on December 9, 2009 at 11:16 from IEEE Xplore. Restrictions apply.

The analysis of a wavelet-based watermarking algorithm is presented, in which the discrete wavelet transform (DWT) is used for watermark embedding and detection. In the image compression field, the relationship between DWT coefficients and the human visual system (HVS) is researched intensively to get better compression performance. Recently, this knowledge has been applied to watermarking algorithms based in the DWT domain. The watermarking algorithm analyzed is adaptive to image characteristics, such as texture and luminance content, and it is realized using pixel by pixel masking in the DWT domain to embed the watermark with maximum energy. The detection process consists of cross-correlation between the marked image and pseudorandom sequences, and, in this process, the original image is not required. Computer simulation results show the robustness and perceptual invisibility of the algorithm.

This paper presents an intermediate frequency (IF) stage of a swept time delayed cross-correlation (STDCC) channel sounder. The proposed topology employs the real-time sliding correlation technique of pseudo-random (PN) sequences, enabling amplitude and Doppler spectrum measurements and analysis of multipath components. It makes use of recent technologies, specifically in the generation and transmission of PN sequences, which allows for an easy adjustment of the main specifications of the sounder. The system presented here has been tested and validated by using a PN sequence at 1GHz chip rate, which allows for a time-delay resolution of consecutive multipath components of 2ns. The dynamic range at the IF stage's input was measured to be around 40 to 50 dB. The results presented are also compared with the VNA frequency sweep method.

This paper presents an intermediate frequency (IF) stage of a swept time delayed cross-correlation (STDCC) channel sounder. The proposed topology employs the real-time sliding correlation technique of pseudo-random (PN) sequences, enabling amplitude and Doppler spectrum measurements and analysis of multipath components. It makes use of recent technologies, specifically in the generation and transmission of PN sequences, which allows for an easy adjustment of the main specifications of the sounder. The system presented herein has been tested and validated by using a PN sequence at 1GHz chip rate, which allows for a time-delay resolution of consecutive multipath components of 2ns. The dynamic range at the input of the IF stage was measured to be better than 40dB.

Multi-carrier code division multiple access (MC-CDMA) systems are under intense investigation for high bit rate wireless communication systems. Their equalization is based on the fast Fourier transform, allowing for an efficient implementation. Iterative receivers with joint detection and decoding have been shown to achieve very good performance for direct sequence (DS)-CDMA systems. We apply this concept to MC-CDMA, the multiuser detector is implemented as parallel interference canceller with post-minimum mean squared error filtering. In this contribution a new pilot based channel estimation scheme based on random time domain sequences is developed. The presented simulation results for a multi path scenario show, that in a fully loaded system with 64 users the single user bound can be approached up to 1 dB. A bit error rate (BER) of 10 −3 is reached already at an Eb/N0 of 12 dB with a 4 state, rate 1/2 convolutional code.

Abstract In this work, a hardware implementation of Chaotic State Sequence Generator for Secure Communication is proposed. The state of the chaotic generator is quantized by a threshold detector and fed to the 16-bit shift register which stores states at sixteen different time instants. The state selection corresponding to any one of the 16 time instant is performed by a multiplexer in pseudo-random manner using a Finite State Machine. The designs were coded in VHDL, implemented on a FPGA device and successfully tested for ...

In this paper, two families of digital maps derived from the Sawtooth map and from the Tent map are analyzed in terms of suitability for pseudo-random bit generation. In particular, several solutions are investigated taking into account the numerical errors due to the approximation strategy used (truncation/rounding off). To evaluate the performance of the obtained pseudo-random sources a number of statistical parameters and tests that properly measure the characteristics of output bit sequences are considered. Results show that, under specific design conditions, the discretized Sawtooth and Tent maps are suitable for generating long-period bit sequences with an adequate randomness quality.

The development of exotic new materials, such as metamaterials, has created strong interest within the electromagnetics (EM) community for possible new phenomenologies and device applications, with particular attention to periodicity-induced phenomena, such as photonic bandgaps (PBG). Within this context, motivated by the fairly recent discovery in X-ray crystallography of "quasicrystals," whose diffraction patterns display unusual characteristics that are associated with "aperiodic order," we have undertaken a systematic study of how these exotic effects manifest themselves in the radiation properties of aperiodically-configured antenna arrays. The background for these studies, with promising example configurations, has been reported in a previous publication [V.

A synthesizer-free self-starting optoelectronic oscillating-pulsator based return-to-zero (RZ) carrier, clock, and data generator is demonstrated by using an integrated distributed feedback laser diode and electroabsorption modulator (DFBLD-EAM) link. The theoretical model of the self-pulsating EAM is numerically analyzed to optimize optical RZ carrier, providing the relatively short pulsewidth, highest ON/OFF extinction ratio, timing jitter, and frequency variation of 16.5 ps, 10.1 dB, 0.6 ps, and <220 kHz, respectively. Such a self-pulsating EAM pulsed carrier exhibits a chirp of-13.5 GHz with corresponding chirp parameter of-0.48, which reveals lower frequency chirp accompanied with higher chirp parameter at lower EAM bias. To trigger the pseudorandom binary-sequence (PRBS) data generator, the DFBLD-EAM based self-starting pulsator also delivers an OC-192 microwave clock with a carrier-to-noise ratio of 51.1 dB, a second-harmonics suppression ratio of 55 dB, and a single-side-band phase noise of −110 dBc/Hz at 10 kHz offset. The proposed system provides a synthesizer-free OC-192 RZ data generation with bit-error rate of 10 −9 under receiving power of −19.8 and −17.2 dBm at back-to-back and 25-km propagation. The receiving sensitivity is improved by 2 and 1.6 dB when comparing with that of a commercial synthesizer triggered RZ data generator. The reduced power penalty is attributed to the signal broadening induced by higher frequency chirp of the self-pulsating EAM. The signal-to-noise ratio of the generated RZ data plays more important role than the extinction ratio on obtaining a better Q-factor up to 6.6. Index Terms-Electroabsorption modulator (EAM), ON-OFF keying (OOK), optoelectronic oscillator (OEO), return-to-zero (RZ), self-pulsation, synthesizer-free. I. INTRODUCTION T HE GENERATION of pulsed return-to-zero (RZ) carrier with short duty cycle is a key to establish the highbit-rate optical time-division-multiplexing (OTDM) network,

A nonstationary finite-alphabet information source p is noiselessly encoded first by adaptive block to variable-length codes and then by codes of this kind that are finite-state. It is shown that if p belongs to a certain class of sources that includes those with finite-order Markov memory, then a stationary input-restricted channel exists such that the optimum encoding rate in the first case is equal to the largest conditional entropy for channel output given channel input, whereas in the second case it is the largest channel output entropy. A sufficient condition for the two rates to be equal is also given.

In this paper, we present a novel method of steganography system based on CDMA (Code Division Multiple Access) approach having regard to perceptibility of stego-image. Also additional extraction algorithms were designed due to enhancing of secret message decomposition. As it will be shown later, aptly imposed features of CDMA techniques are in consonance with imperatives claimed upon steganography systems.

An asynchronous binary DS-CDMA system using random spreading sequences is considered when communicating over various fading channels. New closed-form expressions are derived for the conditional Characteristic Function (CF) of the multiple access interference. A unified analysis is provided for calculating the exact average Bit Error Rate (BER) expressed in the form of a single numerical integration based on the CF approach. The numerical results obtained from our exact BER analysis are verified by our simulation results and are also compared to those obtained by the Standard Gaussian Approximation (SGA), confirming the accuracy of the SGA for most practical conditions, except for high Signal-to-Noise Ratios (SNR) and for a low number of interferers.

This paper discusses the linear complexity property of binary sequences generated using matrix recurrence relation defined over Z 4. Generally algorithm to generate random number is based on recursion with seed value/values. In this paper a linear recursion sequence of matrices or vectors over Z 4 is generated from which random binary sequence is obtained. It is shown that such sequences have large linear complexity.

# School of Electrical Engineering and Informatics Institut Teknologi Bandung, Jl. Ganesha 10 Bandung 40132, Indonesia 1Email: [email protected] 2Email: [email protected] 3Email: [email protected] ... Abstract— Block cipher can be considered as a ...