This document proposes a new two-dwell acquisition method for optical code division multiple access (OCDMA) systems using unipolar optical orthogonal codes (OOCs).
It presents a two-step acquisition procedure where the first dwell examines only the first portion of the OOC code to test cells, and the second dwell fully examines cells that pass the first test. Closed-form expressions are derived to analyze the false alarm and detection probabilities of this method using GQ functions, showing it can achieve the same performance as the existing Multiple Shift algorithm with lower complexity. Numerical results validate the model and show the two-dwell method matches the performance of the Multiple Shift algorithm.
Improvement of chaotic secure communication scheme based on steganographic me...Massoud Khodadadzadeh
1) The document proposes a novel method for improving chaotic secure communication using steganography and multimodal chaotic maps.
2) It hides a message signal in an image by modifying pixel grey levels, and sends the stego image using chaotic parameter modulation.
3) At the receiver, synchronization is used to estimate system parameters and determine the map set in order to retrieve the hidden message signal.
Particle Swarm Optimization for Nano-Particles Extraction from Supporting Mat...CSCJournals
This document summarizes a study that uses Particle Swarm Optimization (PSO) for automatic segmentation of nano-particles in Transmission Electron Microscopy (TEM) images. PSO is applied to specify local and global thresholds for segmentation by treating image entropy as a minimization problem. Results show the PSO method improves over previous techniques by reducing incorrect characterization of nano-particles in images affected by liquid concentrations or supporting materials, with up to a 27% reduction in errors. Compared to manual characterization, PSO provides comparable particle counting with higher computational efficiency suitable for real-time analysis.
OPTIMIZATION OF HEURISTIC ALGORITHMS FOR IMPROVING BER OF ADAPTIVE TURBO CODESIAEME Publication
The third component introduced in the turbo codes improved the code
performance by providing very low error rates for a very wide range of block lengths
and coding rates. But this increased the complexity and the parameters such as
permeability and permittivity rates were constant and they could not perform well
under noisy environments. This drawback was addressed in [1] by proposing A3DTC.
The bit error rate was minimized by generating parameters based on noise and
signal strengths. A performance comparison is done between the two heuristic
algorithms i.e., Genetic Algorithm and Particle Swarm Optimization Algorithm [2]
where a knowledge source using the two algorithms is generated. Under various noisy
environments the experimental results compare the performance of the two
algorithms. In this paper their performance is analyzed and optimization is done. The
results show that genetic algorithm is able to give better performance when compared
to particle swarm optimization algorithm
This document describes a method for separating source signals from interfering signals using an adaptive AMUSE algorithm. It begins with background on blind source separation and the AMUSE algorithm. The proposed method applies the adaptive AMUSE algorithm to signals obtained from nodes in an analog resistor-capacitor circuit, where one input signal is known. The algorithm estimates the source signals by reconstructing the signals using an extended Kalman smoother. The method is experimentally tested on a simulated resistor-capacitor circuit with three input signals and signals measured at random nodes.
RELIABILITY ASSESSMENT OF EMBEDDED SYSTEMS USING STOPWATCH PETRI NETSIJCSEA Journal
In this paper, we propose a reliability approach in which feared events define reliability requirements and
taking them into account allows to design systems which will be able to avoid the drift towards a feared
state. The description of feared scenarios since the system design phase enables us to understand the
reasons of the feared behavior in order to envisage the necessary reconfigurations and choose safe
architectures. In order to face the increasing complexity of embedded systems and to represent the
suspension and resumption of task execution we propose to extract directly feared scenarios from
Stopwatch Petri net model avoiding the generation of the associated reachability graph and the eternal
combinative explosion problem.
The document proposes two stochastic variants of an existing deterministic pedestrian motion model called the Linear Trajectory Avoidance (LTA) model. The first approach is based on a particle filter algorithm, but has limitations that make it computationally expensive. The second approach approximates the pedestrian position and velocity probability density function with a mixture of Gaussians, using the LTA model's energy function to determine the mixture parameters. Both stochastic models were implemented and tested on real-world data, showing improvements over the deterministic LTA model in situations where it has significant prediction errors.
Report AdvancedCodingFinal - Pietro SantoroPietro Santoro
The document provides a summary of a student's laboratory sessions on advanced wireless communications. It includes:
1) Implementation of a C++ class for a sliding window soft-input soft-output decoder with binary log-likelihood ratios as input and output.
2) Simulation of a binary convolutional coded system using the SISO decoder, 2-PAM modulation over an AWGN channel. Bit error rates are computed at the input and output of the SISO decoder.
3) Comments on the SISO decoder class and simulation results for convolutional codes with rates of 1/2, 1/4, and 1/8, reporting the four bit error rates versus Eb/N0.
ARTIFICIAL NEURAL NETWORK APPROACH TO MODELING OF POLYPROPYLENE REACTORijac123
This paper shows modeling of highly nonlinear polymerization process using the artificial neural network approach for the model predictive purposes. Polymerization occurs in a fluidized bed polypropylene reactor using Ziegler - Natta catalyst and the main objective was modeling of the reactor production rate.
The data set used for an identification of the model is a real process data received from an existing polypropylene plant and the identified model is a nonlinear autoregressive neural network with the exogenous input. Performance of a trained network has been verified using the real process data and the
ability of the production rate prediction is shown in the conclusion.
Improvement of chaotic secure communication scheme based on steganographic me...Massoud Khodadadzadeh
1) The document proposes a novel method for improving chaotic secure communication using steganography and multimodal chaotic maps.
2) It hides a message signal in an image by modifying pixel grey levels, and sends the stego image using chaotic parameter modulation.
3) At the receiver, synchronization is used to estimate system parameters and determine the map set in order to retrieve the hidden message signal.
Particle Swarm Optimization for Nano-Particles Extraction from Supporting Mat...CSCJournals
This document summarizes a study that uses Particle Swarm Optimization (PSO) for automatic segmentation of nano-particles in Transmission Electron Microscopy (TEM) images. PSO is applied to specify local and global thresholds for segmentation by treating image entropy as a minimization problem. Results show the PSO method improves over previous techniques by reducing incorrect characterization of nano-particles in images affected by liquid concentrations or supporting materials, with up to a 27% reduction in errors. Compared to manual characterization, PSO provides comparable particle counting with higher computational efficiency suitable for real-time analysis.
OPTIMIZATION OF HEURISTIC ALGORITHMS FOR IMPROVING BER OF ADAPTIVE TURBO CODESIAEME Publication
The third component introduced in the turbo codes improved the code
performance by providing very low error rates for a very wide range of block lengths
and coding rates. But this increased the complexity and the parameters such as
permeability and permittivity rates were constant and they could not perform well
under noisy environments. This drawback was addressed in [1] by proposing A3DTC.
The bit error rate was minimized by generating parameters based on noise and
signal strengths. A performance comparison is done between the two heuristic
algorithms i.e., Genetic Algorithm and Particle Swarm Optimization Algorithm [2]
where a knowledge source using the two algorithms is generated. Under various noisy
environments the experimental results compare the performance of the two
algorithms. In this paper their performance is analyzed and optimization is done. The
results show that genetic algorithm is able to give better performance when compared
to particle swarm optimization algorithm
This document describes a method for separating source signals from interfering signals using an adaptive AMUSE algorithm. It begins with background on blind source separation and the AMUSE algorithm. The proposed method applies the adaptive AMUSE algorithm to signals obtained from nodes in an analog resistor-capacitor circuit, where one input signal is known. The algorithm estimates the source signals by reconstructing the signals using an extended Kalman smoother. The method is experimentally tested on a simulated resistor-capacitor circuit with three input signals and signals measured at random nodes.
RELIABILITY ASSESSMENT OF EMBEDDED SYSTEMS USING STOPWATCH PETRI NETSIJCSEA Journal
In this paper, we propose a reliability approach in which feared events define reliability requirements and
taking them into account allows to design systems which will be able to avoid the drift towards a feared
state. The description of feared scenarios since the system design phase enables us to understand the
reasons of the feared behavior in order to envisage the necessary reconfigurations and choose safe
architectures. In order to face the increasing complexity of embedded systems and to represent the
suspension and resumption of task execution we propose to extract directly feared scenarios from
Stopwatch Petri net model avoiding the generation of the associated reachability graph and the eternal
combinative explosion problem.
The document proposes two stochastic variants of an existing deterministic pedestrian motion model called the Linear Trajectory Avoidance (LTA) model. The first approach is based on a particle filter algorithm, but has limitations that make it computationally expensive. The second approach approximates the pedestrian position and velocity probability density function with a mixture of Gaussians, using the LTA model's energy function to determine the mixture parameters. Both stochastic models were implemented and tested on real-world data, showing improvements over the deterministic LTA model in situations where it has significant prediction errors.
Report AdvancedCodingFinal - Pietro SantoroPietro Santoro
The document provides a summary of a student's laboratory sessions on advanced wireless communications. It includes:
1) Implementation of a C++ class for a sliding window soft-input soft-output decoder with binary log-likelihood ratios as input and output.
2) Simulation of a binary convolutional coded system using the SISO decoder, 2-PAM modulation over an AWGN channel. Bit error rates are computed at the input and output of the SISO decoder.
3) Comments on the SISO decoder class and simulation results for convolutional codes with rates of 1/2, 1/4, and 1/8, reporting the four bit error rates versus Eb/N0.
ARTIFICIAL NEURAL NETWORK APPROACH TO MODELING OF POLYPROPYLENE REACTORijac123
This paper shows modeling of highly nonlinear polymerization process using the artificial neural network approach for the model predictive purposes. Polymerization occurs in a fluidized bed polypropylene reactor using Ziegler - Natta catalyst and the main objective was modeling of the reactor production rate.
The data set used for an identification of the model is a real process data received from an existing polypropylene plant and the identified model is a nonlinear autoregressive neural network with the exogenous input. Performance of a trained network has been verified using the real process data and the
ability of the production rate prediction is shown in the conclusion.
IJERD (www.ijerd.com) International Journal of Engineering Research and Devel...IJERD Editor
This document summarizes a study on reducing four-wave mixing (FWM) effect in a hybrid optical CDMA/WDMA system through simulation. FWM is a nonlinear optical phenomenon that generates new frequency components and causes crosstalk between channels in wavelength division multiplexing (WDM) systems. The study presents a frequency allocation technique using unequal channel spacing to minimize FWM crosstalk. It simulates the FWM effect in a system and compares the output with and without the proposed frequency allocation. The results demonstrate that the technique eliminates superimposition of FWM products on the transmitted channels, reducing crosstalk at the cost of increased bandwidth usage.
Performance evaluation of family of prime sequence codes in an ocdma systemIAEME Publication
This document analyzes and compares the performance of different families of prime sequence codes for optical code division multiple access (OCDMA) systems. It describes prime codes, modified prime codes, new modified prime codes, double padded modified prime codes, and evaluates them based on code length and code weight. Longer codes with higher code weights are found to have better correlation properties and lower bit error rates, allowing more users to be supported in the OCDMA system.
Performance Analysis of M-ary Optical CDMA in Presence of Chromatic DispersionIDES Editor
The performance of M-ary optical code division
multiple access (OCDMA) is analytically investigated in
presence of chromatic dispersion. The study is carried out for
single mode dispersion shifted and non dispersion shifted
fibers. Walsh code is used as user address. The p-i-n
photodetector is used for optoelectronic conversion process.
In our proposed model 16 different symbols are modulated
with different intensity levels and detected by direct detection
technique. The numerical results show that, the reconstruction
of the transmitted symbol is strongly dependent on the received
symbols magnitude which is reduced by fiber length and
symbol rate. It is found that the proposed OCDMA system
shows better performance when dispersion shifted fiber is
used as a communication medium.
This document summarizes a research paper that analyzes the performance of various digital filters in an OCDMA (Optical Code Division Multiple Access) multi-user environment using 3D codes. The document describes a simulation of a 24-user OCDMA system using different parameters like BER (Bit Error Rate), Q-factor, and eye patterns with filters including Raised Cosine, Gaussian, Fabry Perot, Trapezoidal, and Lorentzian. The analysis found that the system using a Fabry Perot filter had the minimum distortion while maintaining a low BER of 6.81×e-20 for correctly decoded signals.
The document describes a simulation model for analyzing the performance of spectral amplitude encoding (SAE) optical code division multiplexing (OCDM) systems over linear dispersive channels. The simulation model implements a SAE/OCDM system with 3 active users out of a total of 8 users. The simulation results match well with theoretical analyses and can therefore be used to model more complex OCDM systems and analyze the impact of different parameters and fiber dispersive effects.
Coherent Optical Code Division Multiple Access (OCDMA) Systems Pedro BertariniCPqD
This document discusses research being conducted at the University of São Paulo's Engineering School of São Carlos, Department of Electrical Engineering on Coherent Optical Code Division Multiple Access (OCDMA) Systems. The research group is led by Postdoctoral Researcher Pedro Luiz Lima Bertarini and includes PhD and Masters candidates. The research focuses on OCDMA encoding technologies like Spectral Phase-Coding Time Spreading, system performance analysis, optimal code-set selection, and applications to antennas and biosensors. Results show code-set selection is necessary to implement optical networks based on OCDMA with satisfactory bit error rates and to maximize the number of simultaneous users. Future work will examine security, robustness and scalability of coherent OCDMA
SIR Analysis of Overloaded CDMA System Using Orthogonal Gold CodesIDES Editor
This document summarizes a research paper that proposes a technique for overloaded CDMA systems using orthogonal gold codes.
1) The technique assigns one set of orthogonal gold codes to the first N users and another set to additional users, but overlays them with different PN sequences. Detection is done iteratively in two steps to detect signals from each user set.
2) A multistage conventional and weighted linear parallel interference cancellation approach is used to cancel interference between the two user sets. Expressions for the signal to interference ratio at the output of the second and third cancellation stages are derived.
3) Simulation results show that the proposed technique can accommodate N users without interference and additional users at the cost of a small
The document is a seminar report on secure communication over fiber optic networks submitted by Fiona Rozario. It discusses optical networks and various security issues in optical networks including issues in network transmission, optical amplifiers, and optical cross-connects. It then covers different encryption systems that can provide security in optical networks such as optical CDMA, quantum cryptography, chaos-based encryption, and optical steganography.
Numerical suppression of linear effects in a opticaliaemedu
This document discusses numerical suppression of linear effects in optical CDMA transmission. It begins by introducing OCDMA and describing the impact of chromatic dispersion as a linear effect that causes temporal spreading of signals. It then proposes a model using Fractional Step Methods to estimate the signal distortion from the fiber and eliminate the estimated linear effects before detection. Simulation results are presented analyzing dispersion's impact on a single Gaussian pulse, perfectly synchronized Gaussian signals for OCDMA, and asynchronous Gaussian signals.
Optical code division multiple access using carbon nanotubes systemIAEME Publication
This document discusses using carbon nanotubes for optical code division multiple access (OCDMA) systems. It first provides background on carbon nanotubes, including their unique electronic and optical properties. It then describes the basic architecture and working principle of OCDMA systems. The document focuses on analyzing how using carbon nanotubes can improve key communication parameters like data rate, bit error rate, and signal-to-noise ratio in OCDMA systems compared to silicon-based optical devices. It presents results showing carbon nanotubes enable ultra-high speed networks with terabits per second data rates and exceptional error rate performance.
OPTICAL SWITCHING CONTROLLER USING FPGA AS A CONTROLLER FOR OCDMA ENCODER SYSTEMEditor IJCATR
This paper proposed a design of optical switching controller using FPGA for OCDMA encoder system. The encoder is one
of the new technologies that use to transmit the coded data in the optical communication system by using FPGA and optical switches.
It is providing a high security for data transmission due to all data will be transmitting in binary code form. The output signals from
FPGA are coded with a binary code that given to an optical switch before it signal modulate with the carrier and transmit to the
receiver. In this paper, AA and 55 data were used for source 1 and source 2. It is generated sample data and sent packet data to the
FPGA and stored it into RAM. The simulation results have done by using software Verilog Spartan 2 programming to simulate. After
that the output will produces at waveform to display the output. The main function of FPGA controlling unit is producing single pulse
and configuring optical switching system.
Effect of fiber distance on various sac ocdma detection techniqueseSAT Journals
Abstract Optical code division multiple access system (OCDMA) has been gaining importance with increasing demands of high speed and large capacity for communication in optical networks. OCDMA system is totally asynchronous, that does not require any clock signals for synchronization in the network. Therefore, OCDMA provide a network that is simpler and offers the potential for scalability to higher levels of connectivity. OCDMA encoding /decoding process also provides a level of security directly implemented in the physical layer. Using OCDMA technique high spectral efficiency is achieved, hence fiber bandwidth is used very efficiently with throughput in excess of Tbit/s. Among several kinds of OCDMA systems, spectra amplitude coding (SAC) scheme attracts increasing interest because multiple access interference (MAI) can be eliminated and preserve the orthogonality between users in the system. This paper presents comparison of three important SAC-OCDMA detection techniques, namely - Direct detection, Complementary subtraction and AND subtraction. The design of encoder and decoder modules for SAC-OCDMA system used in this paper is based on Fiber Bragg Gratings (FBGs). Here conventional single mode fiber (SMF) is used as the transmission link and the performance metric studied is Quality factor (Q) in multiple access environments of various user systems for these three detection techniques. Finally Effect of increasing number of fiber distance on the direct detection technique using NRZ and RZ data formats have been studied. Simulated results show that AND subtraction technique gives better Quality-factor (Q) than the complementary subtraction and direct detection techniques for the signal with same power. Index Terms: OCDMA (optical CDMA), BER (bit error rate), MAI (multiple access interference), DW (double weight code), SAC (spectral amplitude coding) and Q (quality factor)
This document summarizes a seminar presentation on Optical Code Division Multiple Access (OCDMA). OCDMA allows multiple users to transmit simultaneously over the same bandwidth using unique optical codes. It provides advantages over TDMA and FDMA such as supporting more users and asynchronous transmission without packet collisions. The presentation describes OCDMA network implementation using optical orthogonal codes assigned to transmitters and receivers for communication. It also discusses enhanced security provided by OCDMA through increasing the signal-to-noise ratio required for eavesdropping.
This document discusses security issues in fiber optic networks and various encryption techniques used to secure communication over these networks. It first provides background on optical fibers and fiber optic communication systems. It then outlines some common security issues like network attacks that disrupt service or allow tapping of data. Various encryption schemes are discussed like optical CDMA, quantum cryptography, chaos-based encryption, and steganography. Each technique has advantages but also limitations in terms of things like synchronization requirements, vulnerability to jamming, or limited transmission range.
Improving The Performance of Viterbi Decoder using Window System IJECEIAES
An efficient Viterbi decoder is introduced in this paper; it is called Viterbi decoder with window system. The simulation results, over Gaussian channels, are performed from rate 1/2, 1/3 and 2/3 joined to TCM encoder with memory in order of 2, 3. These results show that the proposed scheme outperforms the classical Viterbi by a gain of 1 dB. On the other hand, we propose a function called RSCPOLY2TRELLIS, for recursive systematic convolutional (RSC) encoder which creates the trellis structure of a recursive systematic convolutional encoder from the matrix “H”. Moreover, we present a comparison between the decoding algorithms of the TCM encoder like Viterbi soft and hard, and the variants of the MAP decoder known as BCJR or forward-backward algorithm which is very performant in decoding TCM, but depends on the size of the code, the memory, and the CPU requirements of the application.
This document discusses two schemes for implementing multirate transmission in fiber-optic code-division multiple access (CDMA) networks: the parallel scheme and the serial mapping scheme. The parallel scheme assigns each user multiple addresses based on their data rate and encodes bits in parallel. The serial mapping scheme encodes bits serially using optical orthogonal codes (OOCs) constructed from frequency hop codes. Analysis shows the parallel scheme can support error correction coding to increase network capacity, while the serial mapping performs well even without coding. Both schemes allow accommodating high numbers of multirate users without increasing optical processing complexity.
This document provides contact information for VENSOFT Technologies and describes 25 MATLAB projects for the 2013-2014 academic year related to signal processing topics such as phase noise estimation in MIMO systems, distributed averaging algorithms, channel estimation, computation of the moment generating function for lognormal distributions, compressed sensing of EEG data, and compressed sensing for wireless monitoring of fetal ECG signals. The contact for projects is provided as VENSOFT Technologies, their website, and a phone number.
ANALYSIS OF ELEMENTARY CELLULAR AUTOMATA CHAOTIC RULES BEHAVIORijsptm
We present detailed and in depth analysis of Elementary Cellular Automata (ECA) with periodic
cylindrical configuration. The focus is to determine whether Cellular Automata (CA) is suitable for the
generation of pseudo random number sequences (PRNs) of cryptographic strength. Additionally, we
identify the rules that are most suitable for such applications. It is found that only two sub-clusters of the
chaotic rule space are actually capable of producing viable PRNs. Furthermore, these two sub-clusters
consist of two majorly non-linear rules. Each sub-cluster of rules is derived from a cluster leader rule by
reflection or negation or the combined two transformations. It is shown that the members of each subcluster
share the same dynamical behavior. Results of testing the ECA running under these rules for
comprehensively large number of lattice lengths using the Diehard Test suite have shown that apart from
some anomaly, the whole output sequence can be potentially utilized for cryptographic strength pseudo
random sequence generation with sufficiently large number of p-values pass rates.
The Quality of the New Generator Sequence Improvent to Spread the Color Syste...TELKOMNIKA JOURNAL
This paper shows a new technic applicable for the digital devices that are the result of the finite’s
effect precision in the chaotic dynamics used in the coupled technic and the chaotic map’s perturbation
technics used for the generation of a Pseudo-Random Number Generator (PRNGs).The use of the
pseudo- chaotic sequences coupled to the orbit perturbation method in the chaotic logistic map and the
NewPiece-Wise Linear Chaotic Map (NPWLCM). The pseudo random number generator’s originality
proposed from the perturbation of the chaotic recurrence. Furthermore the outputs of the binary sequences
with NPWLCM are reconstructed conventionally with the Bernoulli’s sequences shifts map to change the
shapes with the bitwise permetation then the results in simulation are shown in progress.After being
perturbed, the chaotic system can generate the chaotic binary sequences in uniform distribution and the
statistical properties invulnerable analysis. This generator also has many advantages in the possible useful
applications of spread spectrum digitalimages, such as sensitive secret keys, random uniform distribution
of pixels in Crypto system in secure and synchronize communication.
A Novel Alamouti STBC Technique for MIMO System Using 16- QAM Modulation and ...IJERA Editor
The wireless communication is the emerging field of research among communication researchers and they are
continuously working towards the reduction if error occurred in the signal during transmission through wireless
media. In this paper the wireless system is simulated with the application of Alamouti space time block codes
(STBC) with MIMO and MISO configurations to compare the results. The modulation technique used here is
16-QAM which is giving better results than other counterparts and to enhance the performance of the system i.e.
to reduce the effect of errors on data we have applied a moving average filter(MAF). The performance of the
system is shown with the simulation results with variable data sizes and found that the proposed approach is
better for the system.
Prediction of a reliable code for wireless communication systemsIAEME Publication
This document discusses the development of super-orthogonal space-time trellis codes (SOSTTCs) using differential modulation for noncoherent wireless communication systems without channel state information. SOSTTCs are designed using binary phase-shift keying (BPSK), quadriphase shift keying (QPSK), and eight-phase shift keying (8PSK). A new decoding algorithm is proposed with reduced complexity compared to traditional decoding, while maintaining the same performance. Computer simulations using a geometric two-ring channel model evaluate the performance of the SOSTTCs under different channel and transmission scenarios. The performance of coherent and noncoherent schemes is compared, with coherent achieving approximately 3 dB better than differential at the cost of
IJERD (www.ijerd.com) International Journal of Engineering Research and Devel...IJERD Editor
This document summarizes a study on reducing four-wave mixing (FWM) effect in a hybrid optical CDMA/WDMA system through simulation. FWM is a nonlinear optical phenomenon that generates new frequency components and causes crosstalk between channels in wavelength division multiplexing (WDM) systems. The study presents a frequency allocation technique using unequal channel spacing to minimize FWM crosstalk. It simulates the FWM effect in a system and compares the output with and without the proposed frequency allocation. The results demonstrate that the technique eliminates superimposition of FWM products on the transmitted channels, reducing crosstalk at the cost of increased bandwidth usage.
Performance evaluation of family of prime sequence codes in an ocdma systemIAEME Publication
This document analyzes and compares the performance of different families of prime sequence codes for optical code division multiple access (OCDMA) systems. It describes prime codes, modified prime codes, new modified prime codes, double padded modified prime codes, and evaluates them based on code length and code weight. Longer codes with higher code weights are found to have better correlation properties and lower bit error rates, allowing more users to be supported in the OCDMA system.
Performance Analysis of M-ary Optical CDMA in Presence of Chromatic DispersionIDES Editor
The performance of M-ary optical code division
multiple access (OCDMA) is analytically investigated in
presence of chromatic dispersion. The study is carried out for
single mode dispersion shifted and non dispersion shifted
fibers. Walsh code is used as user address. The p-i-n
photodetector is used for optoelectronic conversion process.
In our proposed model 16 different symbols are modulated
with different intensity levels and detected by direct detection
technique. The numerical results show that, the reconstruction
of the transmitted symbol is strongly dependent on the received
symbols magnitude which is reduced by fiber length and
symbol rate. It is found that the proposed OCDMA system
shows better performance when dispersion shifted fiber is
used as a communication medium.
This document summarizes a research paper that analyzes the performance of various digital filters in an OCDMA (Optical Code Division Multiple Access) multi-user environment using 3D codes. The document describes a simulation of a 24-user OCDMA system using different parameters like BER (Bit Error Rate), Q-factor, and eye patterns with filters including Raised Cosine, Gaussian, Fabry Perot, Trapezoidal, and Lorentzian. The analysis found that the system using a Fabry Perot filter had the minimum distortion while maintaining a low BER of 6.81×e-20 for correctly decoded signals.
The document describes a simulation model for analyzing the performance of spectral amplitude encoding (SAE) optical code division multiplexing (OCDM) systems over linear dispersive channels. The simulation model implements a SAE/OCDM system with 3 active users out of a total of 8 users. The simulation results match well with theoretical analyses and can therefore be used to model more complex OCDM systems and analyze the impact of different parameters and fiber dispersive effects.
Coherent Optical Code Division Multiple Access (OCDMA) Systems Pedro BertariniCPqD
This document discusses research being conducted at the University of São Paulo's Engineering School of São Carlos, Department of Electrical Engineering on Coherent Optical Code Division Multiple Access (OCDMA) Systems. The research group is led by Postdoctoral Researcher Pedro Luiz Lima Bertarini and includes PhD and Masters candidates. The research focuses on OCDMA encoding technologies like Spectral Phase-Coding Time Spreading, system performance analysis, optimal code-set selection, and applications to antennas and biosensors. Results show code-set selection is necessary to implement optical networks based on OCDMA with satisfactory bit error rates and to maximize the number of simultaneous users. Future work will examine security, robustness and scalability of coherent OCDMA
SIR Analysis of Overloaded CDMA System Using Orthogonal Gold CodesIDES Editor
This document summarizes a research paper that proposes a technique for overloaded CDMA systems using orthogonal gold codes.
1) The technique assigns one set of orthogonal gold codes to the first N users and another set to additional users, but overlays them with different PN sequences. Detection is done iteratively in two steps to detect signals from each user set.
2) A multistage conventional and weighted linear parallel interference cancellation approach is used to cancel interference between the two user sets. Expressions for the signal to interference ratio at the output of the second and third cancellation stages are derived.
3) Simulation results show that the proposed technique can accommodate N users without interference and additional users at the cost of a small
The document is a seminar report on secure communication over fiber optic networks submitted by Fiona Rozario. It discusses optical networks and various security issues in optical networks including issues in network transmission, optical amplifiers, and optical cross-connects. It then covers different encryption systems that can provide security in optical networks such as optical CDMA, quantum cryptography, chaos-based encryption, and optical steganography.
Numerical suppression of linear effects in a opticaliaemedu
This document discusses numerical suppression of linear effects in optical CDMA transmission. It begins by introducing OCDMA and describing the impact of chromatic dispersion as a linear effect that causes temporal spreading of signals. It then proposes a model using Fractional Step Methods to estimate the signal distortion from the fiber and eliminate the estimated linear effects before detection. Simulation results are presented analyzing dispersion's impact on a single Gaussian pulse, perfectly synchronized Gaussian signals for OCDMA, and asynchronous Gaussian signals.
Optical code division multiple access using carbon nanotubes systemIAEME Publication
This document discusses using carbon nanotubes for optical code division multiple access (OCDMA) systems. It first provides background on carbon nanotubes, including their unique electronic and optical properties. It then describes the basic architecture and working principle of OCDMA systems. The document focuses on analyzing how using carbon nanotubes can improve key communication parameters like data rate, bit error rate, and signal-to-noise ratio in OCDMA systems compared to silicon-based optical devices. It presents results showing carbon nanotubes enable ultra-high speed networks with terabits per second data rates and exceptional error rate performance.
OPTICAL SWITCHING CONTROLLER USING FPGA AS A CONTROLLER FOR OCDMA ENCODER SYSTEMEditor IJCATR
This paper proposed a design of optical switching controller using FPGA for OCDMA encoder system. The encoder is one
of the new technologies that use to transmit the coded data in the optical communication system by using FPGA and optical switches.
It is providing a high security for data transmission due to all data will be transmitting in binary code form. The output signals from
FPGA are coded with a binary code that given to an optical switch before it signal modulate with the carrier and transmit to the
receiver. In this paper, AA and 55 data were used for source 1 and source 2. It is generated sample data and sent packet data to the
FPGA and stored it into RAM. The simulation results have done by using software Verilog Spartan 2 programming to simulate. After
that the output will produces at waveform to display the output. The main function of FPGA controlling unit is producing single pulse
and configuring optical switching system.
Effect of fiber distance on various sac ocdma detection techniqueseSAT Journals
Abstract Optical code division multiple access system (OCDMA) has been gaining importance with increasing demands of high speed and large capacity for communication in optical networks. OCDMA system is totally asynchronous, that does not require any clock signals for synchronization in the network. Therefore, OCDMA provide a network that is simpler and offers the potential for scalability to higher levels of connectivity. OCDMA encoding /decoding process also provides a level of security directly implemented in the physical layer. Using OCDMA technique high spectral efficiency is achieved, hence fiber bandwidth is used very efficiently with throughput in excess of Tbit/s. Among several kinds of OCDMA systems, spectra amplitude coding (SAC) scheme attracts increasing interest because multiple access interference (MAI) can be eliminated and preserve the orthogonality between users in the system. This paper presents comparison of three important SAC-OCDMA detection techniques, namely - Direct detection, Complementary subtraction and AND subtraction. The design of encoder and decoder modules for SAC-OCDMA system used in this paper is based on Fiber Bragg Gratings (FBGs). Here conventional single mode fiber (SMF) is used as the transmission link and the performance metric studied is Quality factor (Q) in multiple access environments of various user systems for these three detection techniques. Finally Effect of increasing number of fiber distance on the direct detection technique using NRZ and RZ data formats have been studied. Simulated results show that AND subtraction technique gives better Quality-factor (Q) than the complementary subtraction and direct detection techniques for the signal with same power. Index Terms: OCDMA (optical CDMA), BER (bit error rate), MAI (multiple access interference), DW (double weight code), SAC (spectral amplitude coding) and Q (quality factor)
This document summarizes a seminar presentation on Optical Code Division Multiple Access (OCDMA). OCDMA allows multiple users to transmit simultaneously over the same bandwidth using unique optical codes. It provides advantages over TDMA and FDMA such as supporting more users and asynchronous transmission without packet collisions. The presentation describes OCDMA network implementation using optical orthogonal codes assigned to transmitters and receivers for communication. It also discusses enhanced security provided by OCDMA through increasing the signal-to-noise ratio required for eavesdropping.
This document discusses security issues in fiber optic networks and various encryption techniques used to secure communication over these networks. It first provides background on optical fibers and fiber optic communication systems. It then outlines some common security issues like network attacks that disrupt service or allow tapping of data. Various encryption schemes are discussed like optical CDMA, quantum cryptography, chaos-based encryption, and steganography. Each technique has advantages but also limitations in terms of things like synchronization requirements, vulnerability to jamming, or limited transmission range.
Improving The Performance of Viterbi Decoder using Window System IJECEIAES
An efficient Viterbi decoder is introduced in this paper; it is called Viterbi decoder with window system. The simulation results, over Gaussian channels, are performed from rate 1/2, 1/3 and 2/3 joined to TCM encoder with memory in order of 2, 3. These results show that the proposed scheme outperforms the classical Viterbi by a gain of 1 dB. On the other hand, we propose a function called RSCPOLY2TRELLIS, for recursive systematic convolutional (RSC) encoder which creates the trellis structure of a recursive systematic convolutional encoder from the matrix “H”. Moreover, we present a comparison between the decoding algorithms of the TCM encoder like Viterbi soft and hard, and the variants of the MAP decoder known as BCJR or forward-backward algorithm which is very performant in decoding TCM, but depends on the size of the code, the memory, and the CPU requirements of the application.
This document discusses two schemes for implementing multirate transmission in fiber-optic code-division multiple access (CDMA) networks: the parallel scheme and the serial mapping scheme. The parallel scheme assigns each user multiple addresses based on their data rate and encodes bits in parallel. The serial mapping scheme encodes bits serially using optical orthogonal codes (OOCs) constructed from frequency hop codes. Analysis shows the parallel scheme can support error correction coding to increase network capacity, while the serial mapping performs well even without coding. Both schemes allow accommodating high numbers of multirate users without increasing optical processing complexity.
This document provides contact information for VENSOFT Technologies and describes 25 MATLAB projects for the 2013-2014 academic year related to signal processing topics such as phase noise estimation in MIMO systems, distributed averaging algorithms, channel estimation, computation of the moment generating function for lognormal distributions, compressed sensing of EEG data, and compressed sensing for wireless monitoring of fetal ECG signals. The contact for projects is provided as VENSOFT Technologies, their website, and a phone number.
ANALYSIS OF ELEMENTARY CELLULAR AUTOMATA CHAOTIC RULES BEHAVIORijsptm
We present detailed and in depth analysis of Elementary Cellular Automata (ECA) with periodic
cylindrical configuration. The focus is to determine whether Cellular Automata (CA) is suitable for the
generation of pseudo random number sequences (PRNs) of cryptographic strength. Additionally, we
identify the rules that are most suitable for such applications. It is found that only two sub-clusters of the
chaotic rule space are actually capable of producing viable PRNs. Furthermore, these two sub-clusters
consist of two majorly non-linear rules. Each sub-cluster of rules is derived from a cluster leader rule by
reflection or negation or the combined two transformations. It is shown that the members of each subcluster
share the same dynamical behavior. Results of testing the ECA running under these rules for
comprehensively large number of lattice lengths using the Diehard Test suite have shown that apart from
some anomaly, the whole output sequence can be potentially utilized for cryptographic strength pseudo
random sequence generation with sufficiently large number of p-values pass rates.
The Quality of the New Generator Sequence Improvent to Spread the Color Syste...TELKOMNIKA JOURNAL
This paper shows a new technic applicable for the digital devices that are the result of the finite’s
effect precision in the chaotic dynamics used in the coupled technic and the chaotic map’s perturbation
technics used for the generation of a Pseudo-Random Number Generator (PRNGs).The use of the
pseudo- chaotic sequences coupled to the orbit perturbation method in the chaotic logistic map and the
NewPiece-Wise Linear Chaotic Map (NPWLCM). The pseudo random number generator’s originality
proposed from the perturbation of the chaotic recurrence. Furthermore the outputs of the binary sequences
with NPWLCM are reconstructed conventionally with the Bernoulli’s sequences shifts map to change the
shapes with the bitwise permetation then the results in simulation are shown in progress.After being
perturbed, the chaotic system can generate the chaotic binary sequences in uniform distribution and the
statistical properties invulnerable analysis. This generator also has many advantages in the possible useful
applications of spread spectrum digitalimages, such as sensitive secret keys, random uniform distribution
of pixels in Crypto system in secure and synchronize communication.
A Novel Alamouti STBC Technique for MIMO System Using 16- QAM Modulation and ...IJERA Editor
The wireless communication is the emerging field of research among communication researchers and they are
continuously working towards the reduction if error occurred in the signal during transmission through wireless
media. In this paper the wireless system is simulated with the application of Alamouti space time block codes
(STBC) with MIMO and MISO configurations to compare the results. The modulation technique used here is
16-QAM which is giving better results than other counterparts and to enhance the performance of the system i.e.
to reduce the effect of errors on data we have applied a moving average filter(MAF). The performance of the
system is shown with the simulation results with variable data sizes and found that the proposed approach is
better for the system.
Prediction of a reliable code for wireless communication systemsIAEME Publication
This document discusses the development of super-orthogonal space-time trellis codes (SOSTTCs) using differential modulation for noncoherent wireless communication systems without channel state information. SOSTTCs are designed using binary phase-shift keying (BPSK), quadriphase shift keying (QPSK), and eight-phase shift keying (8PSK). A new decoding algorithm is proposed with reduced complexity compared to traditional decoding, while maintaining the same performance. Computer simulations using a geometric two-ring channel model evaluate the performance of the SOSTTCs under different channel and transmission scenarios. The performance of coherent and noncoherent schemes is compared, with coherent achieving approximately 3 dB better than differential at the cost of
Prediction of a reliable code for wireless communication systemsiaemedu
1) The document proposes super-orthogonal space-time trellis codes (SOSTTCs) using differential binary phase-shift keying (BPSK), quadriphase shift keying (QPSK) and eight-phase shift keying (8PSK) for noncoherent wireless communication systems without channel state information.
2) A new decoding algorithm is proposed with reduced complexity compared to traditional decoding, but with the same performance. Computer simulations using a geometric two-ring channel model show the performance of the SOSTTCs under different conditions.
3) The performance of the differential SOSTTCs is approximately 3 dB worse than coherent SOSTTCs which have channel state information, but differential encoding has
Prediction of a reliable code for wireless communication systemsiaemedu
This document discusses the development of super-orthogonal space-time trellis codes (SOSTTCs) using differential modulation for noncoherent wireless communication systems without channel state information. SOSTTCs are designed using binary phase-shift keying (BPSK), quadriphase shift keying (QPSK), and eight-phase shift keying (8PSK). A new decoding algorithm is proposed with reduced complexity compared to traditional decoding, while maintaining the same performance. Computer simulations using a geometric two-ring channel model evaluate the performance of the SOSTTCs under different channel and transmission scenarios. The SOSTTCs using differential encoding are shown to perform approximately 3 dB worse than those using coherent encoding, as expected from
Energy-Efficient Target Coverage in Wireless Sensor Networks Based on Modifie...ijasuc
One of the major issues in Target-coverage problem of wireless sensor network is to increase the network
lifetime. This can be solved by selecting minimum working nodes that will cover all the targets. This
paper proposes a completely new method, in which minimum working node is selected by modified Ant
colony Algorithm. Experimental results show that the lever of algorithmic complication is depressed and
the searching time is reduced, and the proposed algorithm outperforms the other algorithm in terms.
Energy-Efficient Target Coverage in Wireless Sensor Networks Based on Modifie...ijasuc
One of the major issues in Target-coverage problem of wireless sensor network is to increase the network
lifetime. This can be solved by selecting minimum working nodes that will cover all the targets. This
paper proposes a completely new method, in which minimum working node is selected by modified Ant
colony Algorithm. Experimental results show that the lever of algorithmic complication is depressed and
the searching time is reduced, and the proposed algorithm outperforms the other algorithm in terms.
Energy-Efficient Target Coverage in Wireless Sensor Networks Based on Modifie...ijasuc
One of the major issues in Target-coverage problem of wireless sensor network is to increase the network
lifetime. This can be solved by selecting minimum working nodes that will cover all the targets. This
paper proposes a completely new method, in which minimum working node is selected by modified Ant
colony Algorithm. Experimental results show that the lever of algorithmic complication is depressed and
the searching time is reduced, and the proposed algorithm outperforms the other algorithm in terms.
This document summarizes a student's research project on using hypergraph states for quantum computation. The student investigates an entanglement purification protocol to purify noisy three-qubit states to hypergraph states. The protocol is tested under different noise models and its performance is optimized by varying the order and number of iterations. The optimal protocol achieves fidelities greater than 0.73, 0.64, and 0.65 for dephasing, depolarizing, and global white noise respectively, outperforming previous protocols for purifying to three-qubit hypergraph states.
This document describes a simulation program that models and analyzes the performance of local area networks (LANs) using different topologies, including ring, star, double ring, and standby ring. The simulation uses a technique called register insertion to model message transmission between stations on the network. It tracks various statistical metrics like message throughput, errors, and delays. The goal is to evaluate which topology performs best under different traffic loads and noise conditions. The simulation is implemented as a web application to allow users to configure and run trials of the model.
NON-STATISTICAL EUCLIDEAN-DISTANCE SISO DECODING OF ERROR-CORRECTING CODES OV...IJCSEA Journal
In this paper we describe novel non-statistical Euclidean distance soft-input, soft-output (SISO) decoding algorithms for the three currently most important error-correcting codes: the low-density parity-check (LDPC), turbo and polar codes. The metric is squared Euclidean distance, and the decoders operate using an antilog-log (AL) process. We have investigated the simulated bit-error rate (BER) performance of these non-statistical algorithms on three channel models: the additive White Gaussian noise (AWGN), the Rayleigh fading and Middleton’s Class-A impulsive noise channels, and compare them with the BER performances of the corresponding statistical decoding algorithms for the three codes and channels. In all cases the performance over the AWGN channel of the non-statistical algorithms is almost the same or slightly better than that of the statistical algorithms. In some cases the performance over the two nonGaussian channels of the non-statistical algorithms is worse than that of the statistical algorithms, but the use of a simple signal amplitude limiter placed before the decoder input significantly improves the actual and relative performances of the algorithms. Thus there is no performance loss, and sometimes a significant performance gain, for the proposed decoding algorithms. A major advantage of our algorithms is that estimation of the channel signal-to-noise ratio is not required, which in practice simplifies system implementation. In addition, we have found that the processing complexity of the non-statistical algorithms is similar or slightly less than that of the corresponding statistical algorithms, and is significantly less for the LDPC codes over all of the channels.
Mobile Networking and Mobile Ad Hoc Routing Protocol ModelingIOSR Journals
This document summarizes a research paper about modeling mobile ad hoc networks and routing protocols. It discusses modeling the network topology and connectivity between nodes. It also describes modeling the routing protocol instances running on each node. The document outlines different approaches to modeling the network, including explicitly modeling topology and transitions, parameterizing based on network properties, and developing a universal quantification model. It discusses techniques for coping with state explosion when modeling mobile ad hoc networks, such as symbolic representation, partial order reduction, and abstraction.
CHANNEL ESTIMATION AND MULTIUSER DETECTION IN ASYNCHRONOUS SATELLITE COMMUNIC...ijwmn
In this paper, we propose a new method of channel estimation for asynchronous additive white Gaussian noise channels in satellite communications. This method is based on signals correlation and multiuser interference cancellation which adopts a successive structure. Propagation delays and signals amplitudes are jointly estimated in order to be used for data detection at the receiver. As, a multiuser detector, a single stage successive interference cancellation (SIC) architecture is analyzed and integrated to the channel estimation technique and the whole system is evaluated. The satellite access method adopted is the direct sequence code division multiple access (DS CDMA) one. To evaluate the channel estimation and the detection technique, we have simulated a satellite uplink with an asynchronous multiuser access.
NON-STATISTICAL EUCLIDEAN-DISTANCE SISO DECODING OF ERROR-CORRECTING CODES OV...IJCSEA Journal
In this paper we describe novel non-statistical Euclidean distance soft-input, soft-output (SISO) decoding
algorithms for the three currently most important error-correcting codes: the low-density parity-check
(LDPC), turbo and polar codes. The metric is squared Euclidean distance, and the decoders operate using
an antilog-log (AL) process. We have investigated the simulated bit-error rate (BER) performance of these
non-statistical algorithms on three channel models: the additive White Gaussian noise (AWGN), the
Rayleigh fading and Middleton’s Class-A impulsive noise channels, and compare them with the BER
performances of the corresponding statistical decoding algorithms for the three codes and channels. In all
cases the performance over the AWGN channel of the non-statistical algorithms is almost the same or
slightly better than that of the statistical algorithms. In some cases the performance over the two nonGaussian channels of the non-statistical algorithms is worse than that of the statistical algorithms, but the
use of a simple signal amplitude limiter placed before the decoder input significantly improves the actual
and relative performances of the algorithms. Thus there is no performance loss, and sometimes a
significant performance gain, for the proposed decoding algorithms. A major advantage of our algorithms
is that estimation of the channel signal-to-noise ratio is not required, which in practice simplifies system
implementation. In addition, we have found that the processing complexity of the non-statistical algorithms
is similar or slightly less than that of the corresponding statistical algorithms, and is significantly less for
the LDPC codes over all of the channels.
NON-STATISTICAL EUCLIDEAN-DISTANCE SISO DECODING OF ERROR-CORRECTING CODES OV...IJCSEA Journal
In this paper we describe novel non-statistical Euclidean distance soft-input, soft-output (SISO) decoding
algorithms for the three currently most important error-correcting codes: the low-density parity-check
(LDPC), turbo and polar codes. The metric is squared Euclidean distance, and the decoders operate using
an antilog-log (AL) process. We have investigated the simulated bit-error rate (BER) performance of these
non-statistical algorithms on three channel models: the additive White Gaussian noise (AWGN), the
Rayleigh fading and Middleton’s Class-A impulsive noise channels, and compare them with the BER
performances of the corresponding statistical decoding algorithms for the three codes and channels. In all
cases the performance over the AWGN channel of the non-statistical algorithms is almost the same or
slightly better than that of the statistical algorithms. In some cases the performance over the two nonGaussian channels of the non-statistical algorithms is worse than that of the statistical algorithms, but the
use of a simple signal amplitude limiter placed before the decoder input significantly improves the actual
and relative performances of the algorithms. Thus there is no performance loss, and sometimes a
significant performance gain, for the proposed decoding algorithms. A major advantage of our algorithms
is that estimation of the channel signal-to-noise ratio is not required, which in practice simplifies system
implementation. In addition, we have found that the processing complexity of the non-statistical algorithms
is similar or slightly less than that of the corresponding statistical algorithms, and is significantly less for
the LDPC codes over all of the channels
NON-STATISTICAL EUCLIDEAN-DISTANCE SISO DECODING OF ERROR-CORRECTING CODES OV...IJCSEA Journal
This document describes novel non-statistical soft-input, soft-output (SISO) decoding algorithms for low-density parity-check (LDPC), turbo, and polar codes. These algorithms use squared Euclidean distance as the decoding metric rather than a statistical metric. They also use an "antilog-log" process to combine metrics without requiring knowledge of channel noise variance. Simulation results show the non-statistical algorithms achieve similar or better performance than statistical algorithms over additive white Gaussian noise channels. Over some non-Gaussian channels, performance is comparable after using a simple input limiter. A key advantage is these algorithms do not require estimating the channel signal-to-noise ratio.
Electric vehicle and photovoltaic advanced roles in enhancing the financial p...IJECEIAES
Climate change's impact on the planet forced the United Nations and governments to promote green energies and electric transportation. The deployments of photovoltaic (PV) and electric vehicle (EV) systems gained stronger momentum due to their numerous advantages over fossil fuel types. The advantages go beyond sustainability to reach financial support and stability. The work in this paper introduces the hybrid system between PV and EV to support industrial and commercial plants. This paper covers the theoretical framework of the proposed hybrid system including the required equation to complete the cost analysis when PV and EV are present. In addition, the proposed design diagram which sets the priorities and requirements of the system is presented. The proposed approach allows setup to advance their power stability, especially during power outages. The presented information supports researchers and plant owners to complete the necessary analysis while promoting the deployment of clean energy. The result of a case study that represents a dairy milk farmer supports the theoretical works and highlights its advanced benefits to existing plants. The short return on investment of the proposed approach supports the paper's novelty approach for the sustainable electrical system. In addition, the proposed system allows for an isolated power setup without the need for a transmission line which enhances the safety of the electrical network
Advanced control scheme of doubly fed induction generator for wind turbine us...IJECEIAES
This paper describes a speed control device for generating electrical energy on an electricity network based on the doubly fed induction generator (DFIG) used for wind power conversion systems. At first, a double-fed induction generator model was constructed. A control law is formulated to govern the flow of energy between the stator of a DFIG and the energy network using three types of controllers: proportional integral (PI), sliding mode controller (SMC) and second order sliding mode controller (SOSMC). Their different results in terms of power reference tracking, reaction to unexpected speed fluctuations, sensitivity to perturbations, and resilience against machine parameter alterations are compared. MATLAB/Simulink was used to conduct the simulations for the preceding study. Multiple simulations have shown very satisfying results, and the investigations demonstrate the efficacy and power-enhancing capabilities of the suggested control system.
Optimizing Gradle Builds - Gradle DPE Tour Berlin 2024Sinan KOZAK
Sinan from the Delivery Hero mobile infrastructure engineering team shares a deep dive into performance acceleration with Gradle build cache optimizations. Sinan shares their journey into solving complex build-cache problems that affect Gradle builds. By understanding the challenges and solutions found in our journey, we aim to demonstrate the possibilities for faster builds. The case study reveals how overlapping outputs and cache misconfigurations led to significant increases in build times, especially as the project scaled up with numerous modules using Paparazzi tests. The journey from diagnosing to defeating cache issues offers invaluable lessons on maintaining cache integrity without sacrificing functionality.
ACEP Magazine edition 4th launched on 05.06.2024Rahul
This document provides information about the third edition of the magazine "Sthapatya" published by the Association of Civil Engineers (Practicing) Aurangabad. It includes messages from current and past presidents of ACEP, memories and photos from past ACEP events, information on life time achievement awards given by ACEP, and a technical article on concrete maintenance, repairs and strengthening. The document highlights activities of ACEP and provides a technical educational article for members.
Understanding Inductive Bias in Machine LearningSUTEJAS
This presentation explores the concept of inductive bias in machine learning. It explains how algorithms come with built-in assumptions and preferences that guide the learning process. You'll learn about the different types of inductive bias and how they can impact the performance and generalizability of machine learning models.
The presentation also covers the positive and negative aspects of inductive bias, along with strategies for mitigating potential drawbacks. We'll explore examples of how bias manifests in algorithms like neural networks and decision trees.
By understanding inductive bias, you can gain valuable insights into how machine learning models work and make informed decisions when building and deploying them.
Introduction to AI Safety (public presentation).pptx
Cdma
1. 438 IEEE TRANSACTIONS ON COMMUNICATIONS, VOL. 58, NO. 2, FEBRUARY 2010
On Efficient Code Acquisition of
Optical Orthogonal Codes in Optical CDMA Systems
Francesco Benedetto, Member, IEEE, and Gaetano Giunta, Member, IEEE
Abstract—This letter presents an efficient method for optical
code division multiple access (OCDMA) code acquisition based
on unipolar optical orthogonal codes. We propose a two-dwell
acquisition procedure and provide closed form expressions to
analyze the system’s error probabilities. Our results match
the Multiple Shift (MS) algorithm, recently introduced in the
literature, and show that our procedure can achieve the same
system performance with a lower computational complexity.
Index Terms—Code acquisition and synchronization, code-
division multiple access (CDMA), optical CDMA, optical orthog-
onal codes (OOCs).
I. INTRODUCTION
IN recent years, there has been an explosive growth in the
use of spread spectrum optical communication systems due
to the high speed, large capacity and high reliability of the use
of the broadband of the fiber optic. The operating principles
of optical networks are well depicted in the fundamental
works of Salehi, et al. [1]–[3]. Optical code acquisition and
synchronization plays a crucial role because the degradation
in the performance of the system will be dramatic when the
synchronization between receiver and transmitter is not ideal
[1]. In the seminal work by Keshavarzian and Salehi, [2], a
new synchronization procedure is proposed, namely multiple
shift (MS) algorithm, which greatly improves the performance
of synchronization process based on optical orthogonal codes
(OOCs). Authors in [2] address the synchronization problem
of an optical network using OOC codes of length 𝐹. The
MS algorithm has two modes and an initializing part: first, 𝐹
different shifts (or cells) in the search space are partitioned
into equal-sized groups each containing 𝑀 different shifts. In
the first mode, the algorithm examines the cells in a group all
at the same time and, when the decision variable exceeds the
threshold, the algorithm enters the second mode to find the
correct shift examining separately each of the 𝑀 shifts [2].
In this letter, we match the MS algorithm proposing a new
code acquisition scheme for OCDMA communications based
on OOCs. We present a two-dwell acquisition procedure stud-
ied for the first time in [6], and whose idea was originally pro-
posed in [4] for spread-spectrum (SS) communications, here
extended and applied to the case of optical code acquisition.
In particular, we provide a closed form to analytically express
the system’s false alarm and detection probabilities in terms of
the 𝐺𝑄 functions, [4], and show that our procedure can obtain
Paper approved by W. C. Kwong, the Editor for Optical Networks of the
IEEE Communications Society. Manuscript received April 18, 2008; revised
July 18, 2008.
The authors are with the Digital Signal Processing and Multimedia Com-
munications Lab, Dept. of Applied Electronics, University of ROMA TRE,
via della Vasca Navale 84, 00146 Rome, Italy (e-mail: fbenedetto@ieee.org;
giunta@ieee.org).
Digital Object Identifier 10.1109/TCOMM.2010.02.080043
(a)
(b)
Fig. 1. a) Block scheme of the OCDMA receiver with OOC codes; b) two
dwell acquisition algorithm.
the same system performances as the MS algorithm but with
lower computational complexity. The remainder of this work
is organized as follows. In Section II, we present the two-
dwell acquisition method expressing its performance in terms
of the 𝐺𝑄 functions. Section III shows the numerical results
matching the MS algorithm and highlights the advantages of
the new scheme while Section IV briefly concludes the work.
II. TWO DWELL ACQUISITION METHOD
The typical block scheme of a conventional incoherent
receiver with unipolar OOC is shown here in Fig. 1 (a).
Each receiver first starts the code acquisition process until
it finds an acceptable estimate of 𝜏 𝑛, i.e. the time offset of
the user’s signal from a selected time origin [2]. Then, data
recovery can start while at the same time the tracking system
is continuously running and updating the value of 𝜏 𝑛 to ensure
that the correct shift of the code is used in the decoding
process. The uncertainty region for 𝜏 𝑛 is [0, 𝑇 𝑏), with 𝑇 𝑏 the
bit period. It is divided into fragments (which are also called
cells), each having a duration of 𝑇 𝑐, with 𝑇 𝑐 the chip period.
Then the system searches these possible cells to find the one
within which the actual value of 𝜏 𝑛 is located. To check each
cell, a simple test is adopted as shown in Fig. 1(a) while Fig.
1(b) shows in detail the two dwell algorithm we propose.
0090-6778/10$25.00 c⃝ 2010 IEEE
Authorized licensed use limited to: Jeppiaar Engineering College. Downloaded on May 01,2010 at 04:06:56 UTC from IEEE Xplore. Restrictions apply.
2. BENEDETTO and GIUNTA: ON EFFICIENT CODE ACQUISITION OF OPTICAL ORTHOGONAL CODES IN OPTICAL CDMA SYSTEMS 439
Following the same system model adopted in the seminal
work by Keshavarzian and Salehi [2], the received signal
𝑟(𝑡) is first multiplied with a locally generated replica of
the OOC code, then photo-detected and finally its integral
is computed over one bit period, 𝑇 𝑏, to form a decision
variable. This decision variable is passed to the acquisition
device (i.e. a threshold comparator) in order to implement the
decoding process. The threshold is properly pre-determined,
at least equal to the code weight 𝑊 (i.e. number of chips
taking value of “1”), in order to obtain detection probabilities
equal to one [2]. The working principles of the two-dwell
acquisition algorithm are as follows. In the first mode, the
algorithm realizes a simple serial search analyzing only the
first 𝑁 𝑐 = 𝐹/𝑀 chips of the OOC code, where 𝐹 is the code
length, 𝑀 is the same as in [2] and 𝑁 𝑐 is the upper closest
integer to the ratio 𝐹/𝑀. In this way, we can test one cell
examining only a fraction of the chips of the code. Then, if
the test doesn’t reject the current cell, the algorithm enters the
second mode examining the rest of the chips, i.e. (𝐹 − 𝐹/𝑀)
chips, to find the correct shift (see Fig. 1(b)). Otherwise, if
the cell is rejected, the algorithm moves to the next cell.
It can be possible that, for the effect of the multi-access
interference (MAI) and other noise sources, some false alarms
can happen in both the first and second mode. It is the task
of the verification mode to detect false alarms in the second
mode [2]. Following the same notation as in [2], we denote
with 𝑃 𝑓 𝑎 and 𝑃 𝑑 the false alarm and detection probability,
respectively, of the first mode of the algorithm, with 𝑃 𝐹 𝐴
and 𝑃 𝐷 the probabilities of the second mode. According to
[5], considering an ideal optical fiber CDMA system, only
the interference effect should be taken into account while the
shot and thermal noise are assumed to be zero. In this way, the
mean and variance of the MAI, for a number 𝑁 of interfering
users, can be expressed as:
𝑚 = 𝑊 + (𝑁 − 1)
𝑊2
2𝐹
and
𝜎2
= (𝑁 − 1)
𝑊2
2𝐹
(
1 −
𝑊2
2𝐹
)
𝑀2
(1)
In the case of our interest, since in the first dwell we
investigate only the first 𝑁 𝑐 chips of the code the code weight
𝑊 is represented the number of chips “1” in 𝐹/𝑀 chips while
the code length 𝐹 is 𝑁 𝑐; in the second dwell, the code weight
is 𝑊, since we are analyzing codes of 𝐹 chips. In this way,
using the 𝐺𝑄 functions defined in [4], we now can analytically
express in a closed form the error probabilities, due to the
MAI, as follows for the first mode:
𝑃 𝑑 = 𝐺𝑄1
(
𝜎2
1; 𝑉1; 𝑚1
)
= 𝑒−( 𝑚2
1 𝜎2
1 /2)
⋅
+∞∑
𝑘=0
𝑚2𝑘
1 ⋅ 𝜎2𝑘
1
2 𝑘 ⋅ 𝑘!
⋅ Γ1
(
𝑉 2
1
2𝜎2
1
; 𝐾 + 1
)
(2)
𝑃 𝑓 𝑎 = 𝐺𝑄1
(
𝜎2
1; 𝑉1; 0
)
= Γ1
(
𝑉 2
1
2𝜎2
1
; 1
)
= exp
(
−
𝑉 2
1
2𝜎2
1
)
(3)
and as follows for the second mode of the algorithm:
𝑃 𝐷 = 𝐺𝑄2
(
𝜎2
1; 𝜎2
2; 𝑉1; 𝑉2; 𝑚2
)
== 𝑒−( 𝑚2
2( 𝜎2
1 +𝜎2
2 )/2)
⋅
+∞∑
𝑘=0
+∞∑
𝑛=0
(𝑘 + 𝑛)!𝜎2 𝑛
2 𝑚2 𝑛
2
𝑘! (𝑛!)2
2 𝑛
(
1 +
𝜎2
1
𝜎2
2
) (
1 +
𝜎2
2
𝜎2
1
) 𝑘
(4)
𝑃 𝐹 𝐴 = 𝐺𝑄2
(
𝜎2
1; 𝜎2
2; 𝑉1; 𝑉2; 0
)
=
=
+∞∑
𝑘=0
Γ1
[
𝑉 2
1 ( 𝜎2
1 +𝜎2
2 )
2𝜎2
1 +𝜎2
2
, 𝑘 + 1
]
⋅ Γ1
(
𝑉 2
2
2𝜎2
2
, 𝑘 + 1
)
(
1 +
𝜎2
1
𝜎2
2
) (
1 +
𝜎2
2
𝜎2
1
) 𝑘
(5)
where 𝑉1 and 𝑉2 are the threshold values for the first and
second mode, respectively, while (𝑚1, 𝑚2, 𝜎1, 𝜎2) are the
mean values and variances for the two modes and Γ1(∙, ∙)
is the well-known incomplete gamma function [4].
It has to be noted that the proposed scheme performs a
partial correlation for each dwell, and thus, the threshold
should be less than the weight of the code. In fact, for PN
sequences which are used in wireless systems the threshold is
fixed with the criterion of CFAR (constant false alarm rate) [7].
In particular, the CFAR test is accomplished in two successive
parts: first, a threshold is determined to limit the false-alarm
probability at a given reduced value (size of the test); second,
the probability of detection (power of the test) is evaluated
for the threshold previously determined. The probability of
false alarm must be tuned to guarantee a very low number
of possible false alarms, which eventually imply a relevant
penalty time to the acquisition device. Large probabilities of
detection (up to 100%) are typical of well-performing testing
variables.
However, here in order to match the results of the MS
algorithm and as detailed in the next Section, we use threshold
values equal to 𝑊 for the first and second dwell, to obtain
at the end of the acquisition process a detection probability
equal to one [2].
III. NUMERICAL RESULTS
In this section, we devise the validity of the GQ functions to
model the MAI effect, and then we evaluate the performance
of the two-dwell method matching the MS algorithm. Finally,
we highlight the advantages of the new approach versus the
MS in terms of computational complexity. In all the following
graphs we have used according to [2], OOC codes of length
𝐹 = 200, weight 𝑊 = 5, and threshold values equal to 𝑊.
Fig. 2 shows here the performance of the MS algorithm
evaluated for different users, varying 𝑀. Dotted lines represent
simulation results, while solid lines stand for theoretical results
obtained with the GQ functions (red lines) and the binomial
functions (black lines) used in [2]. As it can be easily
seen, simulation results perfectly match the theoretical ones
confirming the validity of the GQ approach in modeling the
MAI effect.
Fig. 3 illustrates the comparison between the receiver op-
erating characteristics (ROC) of the two methods for various
𝑀 and different users (Fig. 3(a) for 𝑁 = 5, Fig. 3(b) for
𝑁 = 8). As we can see, the performance of the two-dwell
approach is almost the same of the MS procedure and again
Authorized licensed use limited to: Jeppiaar Engineering College. Downloaded on May 01,2010 at 04:06:56 UTC from IEEE Xplore. Restrictions apply.
3. 440 IEEE TRANSACTIONS ON COMMUNICATIONS, VOL. 58, NO. 2, FEBRUARY 2010
Fig. 2. 𝑃 𝑓 𝑎 of the multiple shift versus the number of shift (M) for different
users (N). Solid lines = theor. (black for binomial, gray for GQ), dotted lines
= sim.
(a)
(b)
Fig. 3. Performance comparison between the two methods versus different
shift for: a) 𝑁 = 5 users, b) 𝑁 = 8 users. Solid lines = theor. (black for MS,
gray for Two-Dwell), dotted lines = sim. (black for MS, gray for Two-Dwell).
the simulations well match the theoretical results. It has to be
noted that, the number of curves for the two-dwell approach
is limited to analyze an integer number of 𝑁 𝑐 chips in the first
mode. It has to be underlined that the OOC is a sparse code.
In other word the density of ON pulses is low. So when we
search on only 𝐹/𝑀 chips in the first step, this is probable
that no ON chip exists in the search area. This phenomenon
makes more sense when code weight is low e.g. 𝑊 = 5 as
considered in this work. When 𝑀 increases, this probability
increases and consequently probability of detection decreases.
On the other hand, the probability of false alarm increases
too because, if the algorithm works on the intensity of one
single impulse, there are different noise sources that cannot
be avoided and must be now considered (e.g. shot noise and
Fig. 4. MAT performances of the system versus different values of the
parameter 𝑀 and different numbers (N) of users, (circles for MS scheme,
diamonds for proposed approach).
dark currents). This means that the algorithm always enters
the second dwell for a verification task and, at the end of the
second mode, we have always a true detection. In this case,
the first dwell is performed with the lowest computational
complexity (i.e. it analyzes only one chip) and hence the
system performances (in terms of mean acquisition time) are
the same of the MS algorithm. However in PN sequences
which are used in wireless systems we do not have this effect
since the codes are bipolar. Also in the multiple-shift algorithm
the choice of the parameter 𝑀 could have two different effects
on the performance of the synchronization system [2]. As
𝑀 increases the number of shifts examined simultaneously
increases and, therefore, the search space will be covered in
fewer tries. On the other hand, with the increase of 𝑀, the
number of dwell times required to find the correct shift among
the shifts in the second stage will increase. Another effect of
increasing 𝑀 is that the probability of false alarm of the first
stage will increase since with the use of a larger value for
parameter 𝑀, more interference is introduced in the checking
process.
It is, therefore, expected that an optimum value for 𝑀 exists
for which the performance of the synchronization system is
optimum, or equivalently the synchronization time is min-
imum, as represented in the following Fig. 4. Considering
that the most important performance measure is the mean
acquisition time (MAT) for acquisition process, Fig. 4 shows
here the performance of the two algorithms (the MS and the
double dwell) in terms of needed number of bits for acquisition
purposes (MAT) varying the system performance such as 𝑀
and 𝑁. The curves are obtained with a detection probability
equal to one and for a different number of users (from 2 to 8).
From the graph, we can easily see that the curves referring
to both the algorithms show the same behavior, confirming
that the two acquisition techniques have the same system
performances. Moreover, it has to be noted that increasing
the value of 𝑀, for a fixed detection probability, makes the
two algorithms converge to the same performances (i.e. same
MAT), confirming the assumptions we made before.
It is not be surprisingly that the two acquisition techniques
have the same system performances. This is a consequence
of the fact that both the proposed and MS scheme perform
Authorized licensed use limited to: Jeppiaar Engineering College. Downloaded on May 01,2010 at 04:06:56 UTC from IEEE Xplore. Restrictions apply.
4. BENEDETTO and GIUNTA: ON EFFICIENT CODE ACQUISITION OF OPTICAL ORTHOGONAL CODES IN OPTICAL CDMA SYSTEMS 441
the same operations (correlation and threshold comparison)
on the same codes but using a different amount of chips. In
fact, while the MS algorithm performs 𝑀 correlations of 𝐹
chips (parallel search), the proposed scheme realizes only one
correlation on 𝐹/𝑀 chips (serial search), in the first dwell.
Then, in the second dwell while the MS searches the correct
shift analyzing the 𝑀 correlations of 𝐹chips one after the
other, the proposed approach realizes the correlation only on
the remaining (𝐹 − 𝐹/𝑀) chips. The advantages of using
the two-dwell approach lie in the fact that it presents a lower
complexity than the MS algorithm. In fact, we can define two
(lower and upper) bounds of the acquisition performance: best
case if the correct shift is the first on 𝐹 chips; 𝑤𝑜𝑟𝑠𝑡 case if
the correct shift is the last chip on 𝐹 chips. We can evaluate
the total number of needed operations as follows:
- Best case: in this case, the correct shift is represented
by the first chip of the first code (on 𝑀) in the search area.
In particular, the multiple shift algorithm must analyze 𝑀
different shifts at the same time in the first dwell, and then
find the correct shift in the second dwell analyzing each shift
separately. This means that during the first dwell the MS
algorithm must perform 𝑀 correlations of codes made of 𝐹
chips, for a total number of operations (sums and products)
of 2∗
𝑀∗
𝐹, while in the second dwell it will find the correct
chip analyzing only the first shift of the first code of 𝐹 chips,
for a total number of operations (sums and products) of 2∗
𝐹.
Hence the total number of operation performed by the MS
algorithm (in the first and second dwell) for the best case is
2𝐹∗
(𝑀 +1). In the first dwell, the proposed method performs
a total number of operations (sums and products) of only
2∗
𝐹/𝑀, because it performs a serial search on 𝐹/𝑀 chips
of the same code. Then in the second dwell, it performs the
correlation on the remaining chips. Hence the total number of
operations performed by the proposed algorithm (in the first
and second dwell) is 2 𝐹.
- Worst case: in this case, the correct shift is represented
by the last chip of the last code (on 𝑀) in the search area.
In particular, the multiple shift must perform 𝑀 correlations
of codes made of 𝐹 chips, for a total number of operations
(sums and products) of 2∗
𝑀∗
𝐹, while in the second dwell it
will find the correct chip analyzing all the 𝐹 chips of all the
𝑀 shifts (the correct chip is the last one of the 𝑀-th code
of length 𝐹). Hence the total number of operations performed
by the MS algorithm (in the first and second dwell) for the
worst case is 2𝐹∗
(𝐹 + 𝑀). On the other hand, the proposed
method performs a serial search on all the 𝐹/𝑀 chips for 𝑀
codes (2∗
𝐹 operations) and then passes to the second dwell,
performing the correlation on the remaining chips of the last
code only, 2∗
(𝐹 − 𝐹/𝑀) operations. Hence, the total number
of operation performed by the proposed algorithm (in the first
and second dwell) is 2𝐹∗
(2𝑀 − 1)/𝑀.
In conclusion, the number of operations required by the two
acquisition methods, in terms of total sums and products, is
as follows:
- MS: best case = 2∗
𝐹∗
(𝑀 +1) operations; worst case
= 2∗
𝐹∗
(𝑀 + 𝐹) operations.
- Two-dwell: best case = 2∗
𝐹 operations; worst case
= 2∗
𝐹∗
(2∗
𝑀 − 1)/𝑀 operations.
We can conclude that with the new algorithm we obtain the
same systems performances of the MS, but saving a number
of operations 𝐺 𝑏 = (𝑀 + 1) in the best operating case and a
number of operations equal to 𝐺 𝑤 = 𝑀∗
(𝑀 + 𝐹)/(2∗
𝑀 −
1) ≈ (𝑀 + 𝐹)/2 in the worst case, that rapidly increases with
𝑀.
IV. CONCLUSIONS
This paper has devised a two-dwell acquisition scheme
for OCDMA communications based on OOCs. We have
provided a closed form to analytically express the system’s
error probabilities and showed that our procedure can obtain
the same system performance as the MS approach but with
lower computational complexity.
REFERENCES
[1] A. Keshavarzian and J. A. Salehi, “Optical orthogonal code acquisition
in fiber-optic CDMA systems via the simple serial-search method,” IEEE
Trans. Commun., vol. 50, no. 3, pp. 473–483, Mar. 2002.
[2] A. Keshavarzian and J. A. Salehi, “Multiple-shift code acquisition of opti-
cal orthogonal codes in optical CDMA systems,” IEEE Trans. Commun.,
vol. 53, no. 4, pp. 687–697, Apr. 2005.
[3] J. A. Salehi, “Code division multiple-access techniques in optical fiber
networks—I: fundamental principles,” IEEE Trans. Commun., vol. 37,
no. 8, pp. 824–833, Aug. 1989.
[4] G. Giunta, “Generalized Q-functions for application to noncoherent serial
detection of spread-spectrum communication signals,” IEEE Trans. Signal
Process., vol. 48, no. 5, pp. 1506–1513, May 2000.
[5] J. A. Salehi and C. A. Brackett, “Code division multiple-access techniques
in optical fiber networks—II: systems performance analysis,” IEEE Trans.
Commun., vol. 37, no. 8, pp. 834–842, Aug. 1989.
[6] D. DiCarlo and C. Weber, “Multiple dwell serial search: performance and
application to direct sequence code acquisition,” IEEE Trans. Commun.,
vol. 31, no. 5, pp. 650–659, May 1983.
[7] H. L. Van Trees, Detection, Estimation, and Modulation Theory. New
York: Wiley, 1971.
Authorized licensed use limited to: Jeppiaar Engineering College. Downloaded on May 01,2010 at 04:06:56 UTC from IEEE Xplore. Restrictions apply.