J. Arputha Vijaya Selvi

Comparison of Different Models for Ground-Level Atmospheric Attenuation Prediction with New Models According to Local Weather Data for FSO Applications

A dedicated Free Space Optical Link (FSOL) for the range of 0.5 km at an altitude of 15.25 m is established and explained. The power levels of the received signal with meteorological parameters are continuously measured using the opto-electronic assembly and developed weather station respectively and stored in a computer. The existing models selected for comparative analysis are briefed. Measured meteorological parameters and optical attenuation of size [2000 4] are used for linear regression analysis as well as to design the mathematical models more suitable at the test field. In addition, the prediction accuracy of the proposed and selected models during different seasons in one-year period are investigated and validated in terms of RMSE. The average Root Mean Square Error (RMSE) of 0.041 dB/km for the optical attenuation is achieved in the longer range dynamic of meteorological parameters during different local seasons.

A direct and neural controller performance study with beam wandering mitigation control in free space optical link

The beam wander on the detector plane is one of the main causes for major power loss which severely degrades the performance of Free Space Optical (FSO) link. Designing a suitable controller to correct the beam motion at a faster rate to increase the beam stability becomes significant. This paper presents an investigation on the performance of two types of controller designed for aiming a laser beam to be at a particular point under dynamic disturbances. The first design is based on the Taguchi’s method (direct controller) while the second is the Artificial Neural Network (ANN) method (neural-controller). These controllers process the beam location information and generate the necessary outputs to mitigate the beam wandering. The pipelined-parallel architecture for both controllers are developed in a Field Programmable Gate Array (FPGA) and installed at the receiver station. Evidence of the suitability and the effectiveness of the proposed controller in terms of prediction exactness, prediction error, reduction of focal point wander, response to impulse and scintillation are provided through experimental results from the FSO link established for the horizontal range of 0.5 km at an altitude of 15.25 m.

2-DWT and AES: Secure Authentication Management for Polar Iris Templates Using Visual Cryptography

Biometrics deals with authenticating a persons identity based on the physiological or behavioral characteristics. Visual cryptography (VC) is a promising information security technique that allows the secret sharing of images without any cryptographic computations. Various existing schemes were introduced for securing the raw biometric data and template in the database using the VC technique. The complexity of encryption plays a vital role in security improvement. In order to overwhelm the above limitations, a secure authentication management for polar iris templates is presented using VC technique. The collaborative splitting of pixels in all directions presented in this paper was done in order to improve security. At first, the input image was segmented using the Canny edge detection and Hough transform. Subsequently, the normalization module transformed the iris texture from the Cartesian to polar-coordinates. The polar iris image was further separated into two shares, namely, share 1 and share 2, using VC technique. To accomplish more security than the existing methods, both 2-discrete wavelet transform (DWT) and advanced encryption standard (AES) shifting techniques were introduced in VC, termed as transform based AES (TAES). After receiving the encrypted image, the feature extraction is carried out by multi-scale local binary pattern (MLBP). The share 1 images are stored in the user database, whereas the share 2 images are stored in the server database. K-NN classifier is employed to recognize and retrieve the share 2 from the user database on the basis of features. Finally, reconstruction was performed from recognized share 1 and share 2 images by using the inverse process of TAES. The experimental results exhibit better peak signal to noise ratio (PSNR), mean square error (MSE) and normalized correlation (NC), false acceptance rate (FAR), false rejection rate (FRR), and equal error rate (EER) than the other existing methods.

Parametric analysis of a novel reconfigurable Wireless Sensor Network architecture

Wireless Sensor Networks (WSN) plays a vital role in the modern communication mechanism. These are more vulnerable to attacks due to their basic limitations such as communication distance, memory, processing, throughput and power. In this paper we analyze communication delay and energy consumption of a WSN. We propose a Novel Dynamic Reconfigurable Network Monitoring Node (DRNMN), which controls the data transactions in a WSN and reduces the delay incurred and improves the performance with energy optimization. This paper focuses using analysis of DRNMN model with LEACH protocol using NS2 simulator considering the delay, energy, throughput and performance parameters.

Terrestrial free space line of sight optical communication (TFSLSOC) using adaptive control steering system with laser beam Tracking, Aligning and Positioning (ATP)

Free Space Optical Communication (FSOC) is the most promising approach for addressing the emerging broadband access network. Quick link setup, high transmission security, large bandwidth and light weight are some of the important features of this system. However, the laser power attenuation due to adverse weather conditions and scattering due to turbulence are to be mitigated. In this paper, a Position Sensing Detector (PSD) and Stochastic Parallel Gradient Descent Algorithm (SPGDA) based control system using Field Programmable Gate Array (FPGA) in a Closed Loop Control Configuration (CLCC) are developed and presented for Aligning, Tracking and Positioning (ATP) the laser beam to improve the performance of the FSOC.

Real-time implementation of three phase 27-level multilevel inverter with DC carrier PWM technique

Nowadays the asymmetrical cascaded Multi-Level Inverter (MLI) concepts are predominantly investigated. This paper deals with the multi constant dc carrier modulation strategy for 3Φ 27 level Trinary Hybrid MLI (THMLI). The suitability and qualities of the modulation strategy is investigated by simulation using MATLAB/Simulink and also implemented in real time using dSPACE real time interface controller. The proposed task focuses on the reduction of harmonics content in output phase voltages and line voltages of the 3Φ THMLI. The viability of the multi constant dc carrier technique on the MLI has also been presented.

Finite state Markovian model for trustworthy reliable communication in dynamic reconfigurable Wireless Sensor Network architecture

Wireless Sensor Networks (WSNs) are constrained by a limited energy sources. Trust in a WSN is defined as the amount of confidence obtained from the individual node with respect to its data collecting, composing and communication (C3) probability with other peered nodes. Trustworthiness and energy optimization of Wireless Sensor Networks (WSNs) is an active research topic. Trustworthiness of a WSN majorly influenced by security, reliability, mobility and communication models. As the topology of the network alters according to mobility of the node, getting trustworthiest system is very difficult. Reconfigurable techniques modify the system in a controlled manner, and provides adaptability, proposed a Reconfigurable Wireless Sensor Network Architecture (RWSNA) using Markovian chain model for the enhancement of the trustworthiness of the WSN system for reliable communication at runtime with energy optimization. The trust values have been simulated based on the Markovian model based Finite State Machine (FSM) logic of our proposed RWSNA system has been simulated using MATLAB and Simulink and corresponding waveforms of the WSN has been captured and presented.

Mitigation of low-order atmospheric turbulent effects using sensorless adaptive optics in terrestrial free space optical communication

Tip-Tilt and wavefront distortion in the Free Space Optical Communication (FSOC) can be mitigated with Conventional Adaptive Optics (AO) which is widely used in many optical systems to improve the quality of an optical system by manipulating the optical wavefronts using suitable techniques thereby improving BER. This paper describes Sensorless Adaptive optics (SLAO) technique which replaces the high cost wavefront sensor and corrects aberrated optical wavefront by comparing a test wavefront to a perfect, reference wavefront, and then modifying the test wavefront in order to reach the reference wavefront. Artificial Neural Networks (ANN) based reconstruction technique is proposed. The neural network is designed to use the information of tilt in the wave-front acquired by the science camera by extracting the parameters as inputs and estimate the turbulence in terms of Zernike coefficients. Multi-Layer feed forward Neural Network is used to train the inputs and to find actuator control voltages which are applied to DM. In this paper we present a practical implementation of Adaptive Optics system at 850 nm based on a wave-front sensorless architecture. Proposed experimental set-up reduces the complexity and the cost of the conventional adaptive optics system. SLAO provides fast and effective wave-front correction. When compared with the conventional AO systems, the sensorless technique offers the advantage of not requiring the high cost wavefront sensor.

Comparative performance analysis of forward error correcting codes for Free Space Optical communication

Free Space Optical communication system communicates datas which are interleaved with errors during the transmission. These errors occur because of various atmospheric turbulence conditions. The Bit Error Rate (BER) is an important measurement in laser communication link to estimate the quality of the data link connection. Forward Error Correction (FEC) codes are used to detect and correct the errors, so that the original data can be recovered at the receiving end. The performance of Hamming code, Low Density Parity Check (LDPC) code and Turbo code are compared based on Bit Error Rate. Simulation is done using MATLAB and it is observed that LDPC code exhibits low bit error rate compared to other two codes.

Harmonic Analysis of Multilevel Multiphase Space Vector Pulse Width Modulator for Over Modulation Region

In the recent years, the multi-level converter technology has increased due to the achievement of high power ratings. Also multi-phase converter technology permits more than three phases in drive applications. Multi-level multi-phase combined technology gives the benefits of both technologies. In this paper, analyses the multi-level multi-phase Space Vector Pulse Width Modulator (SVPWM) modulator for over modulation region of operation. The space vector pulse width modulation technique assures linearity till an output of 90.7% of the installed inverter capacity. Over modulation is a non-linear process and it necessitates two modes of operation depending on modulation index (MI). Mode-I for compensating the voltage vector to be applied while mode-II uses the concept of continuous application of a specific voltage vector in order to achieve the desired average voltage vector and hence angular velocity. In this paper, mode-I operation of over modulation is extended beyond usual modulation index thus far reported 0.9535 in the literature survey, thus stretching the arrival of Mode-II further towards six steps. This delay in the arrival of over modulation Mode-II decreases the non linearity effect as the lower order harmonics are reduced, thereby improving the controllability of the angular velocity. This helps in compensating the current and torque ripples in the motor. The acceptable operation of the extensive range of mode-I and the smooth transition into mode-II and six steps is verified using simulation results. The simulation results discussed about the odd harmonics with and without over modulation region.