Volume 9, Issue 1, June 2011

A Novel Classification Method for Underwater Acoustic Communication [Full Text]

Nouha Alyaoui, Abdennaceur Kachouri, Mounir Samet

Underwater acoustic communications are a rapidly growing field of research and engineering due to both civilian and military applications. Such applications require networks and wireless aquatic communication systems that can use the digital modulations FSK (Frequency Shift Keying), PSK (Phase Shift Keying), QAM (Quadrature Amplitude Modulation) and OFDM (orthogonal frequency-division multiplexing). This paper outlines a method to classify automatically these digital modulations. We first present the fundamental physics of the underwater channel; then we review the signal model. Secondly,
we will review three algorithms considered for the automatic modulation classification. The last part is an evaluation of the performance in term of probability of correct classification.


Design of an S-Band Circular Microstrip Patch Antenna
[Full Text]

Akande D.O, Odeyemi K.O, and Ogunti E.O

This paper present the design of an S-band circular microstrip patch antenna using a conventional coaxial probe feed technique. The antenna is designed to function within the frequency range of 2.0 GHz - 2.5 GHz, S-band. The antenna exhibited a return loss of -16dB and a directivity of 6.07dB. The microstrip patch antenna is designed on FR4 epoxy substrate and is to be feed with a 50Ω coaxial cable. The design of the antenna is done using MATLAB software and SonnetLite software for the electromagnetic simulation.


Comparative Study of High Density Impulse Noise Removal Spatial Domain Methods used in Image Processing
[Full Text]

Shrawan Kumar, Saurabh Srivastava, Chakresh Kumar and Ghanendra Kumar

In this paper we have done comparative study of various high density impulse noise removal methods. Different noise densities from 10% to 98% were removed by using eight types of spatial domain filters viz. Arithmetic Mean Filter (AMF), Geometric Mean Filter (GMF), Harmonic Mean Filter (HMF), Contra-harmonic Mean Filter (CHMF), Median Filter (MF), Max Filter, Min Filter, Adaptive Median Filter (AdMF). The comparative study is based on the three performance parameters which are: Mean Absolute Error (MAE), Mean Square Error (MSE), and Peak Signal to Noise ratio (PSNR). The mean absolute error is a quantity used to measure how close forecasts or predictions are to the eventual outcomes. The mean square error of an estimator is one of many ways to quantify the difference between an estimator and the true value of quantity being estimated. MSE is a risk function, corresponding to the expected value of the squared error loss or quadratic loss. MSE measures the average of the square of the "error." The error is the amount by which the estimator differs from the quantity to be estimated. The phrase peak signal-to-noise ratio, often abbreviated PSNR, is an engineering term for the ratio between the maximum possible power of a signal and the power of corrupting noise that affects the fidelity of its representation. Because many signals have a very wide dynamic range, PSNR is usually expressed in terms of the logarithmic decibel scale. Our quantitative results with the help of MATLAB simulations show that for lower noise densities to medium-high noise densities ( 10 to 80%) , Max filter gives the optimum performance followed by adaptive median and median filters. For noise densities from 80% to 90%, Min filter showed best results, followed by Max and Adaptive median filters respectively. For more values of noise density (> 90%) the Min Filter showed best results followed by Adaptive median and Median Filters respectively.


Efficient Scheduling of Advanced Reservations With Traffic Grooming Using Varying Transmission Rates in WDM Optical Networks [Full Text]

Dipak Pawar, Sandeep Shinde, Alankar Dasare, Karthick Subramanian

Allocating the light path in grid environment is essential to reduce blocking probability, wavelength fragmentation and to improve network utilization. In this paper, we have evaluated and compared several algorithms for dynamic scheduling of light paths using a flexible advance reservation model with varying transmission rates and traffic grooming. Our objective is to find best scheduling policy for dynamic network resource manager (DNRM). The scheduling of light paths involves both routing and wavelength assignment. We determine the link cost by current and future utilization of the link. Our simulation results show that load balancing switch path first with traffic grooming (LBSPFTG) and load balancing slide window first with traffic grooming (LBSWFTG) techniques have minimum blocking. Best fit (BF) wavelength assignment scheme is better than other wavelength assignment techniques whereas performance of average bandwidth allocation techniques is better than other bandwidth allocation techniques.