Sarhan M. Musa

Application of the finite element method in calculating the capacitance and inductance of multiconductor transmission lines

Multiconductor transmission lines in multilayered circuit are used to reduce dimensions and minimal pulse distortion and crosstalk for high-speed and high- density digital applications. In this paper we present modeling of the capacitance and inductance of two conductors in two different dielectric layers, two conductors in the same dielectric layers, and three conductors in three different dielectric layers. The modeling and simulation is illustrated using the finite element method (FEM).

Performance Analysis of Computer Networks

This book covers performance analysis of computer networks, and begins by providing the necessary background in probability theory, random variables, and stochastic processes. Queuing theory and simulation are introduced as the major tools analysts have access to. It presents performance analysis on local, metropolitan, and wide area networks, as well as on wireless networks. It concludes with a brief introduction to self-similarity. Designed for a one-semester course for senior-year undergraduates and graduate engineering students, it may also serve as a fingertip reference for engineers developing communication networks, managers involved in systems planning, and researchers and instructors of computer communication networks.

Analysis of Rectangular Coaxial Lines

This paper proposes a numerical analysis for calculating the capacitance of rectangular coaxial lines. We illustrate how to model and simulate the capacitance of rectangular coaxial lines using COMSOL, a finite element software. The goal is to use COMSOL to determine the capacitance per unit length of rectangular coaxial lines. We compared the results with those obtained by other methods and found them to be very close.

Secured Mobile Device Software Update over IP Networks

One of the major difficulties in managing mobile device maintenance is to perform software updates over the open network. Mobile devices are demanding more complex operation software. The manufacturer may need for some reason to update the operation software or even add new functionalities from time to time. The manufacturer may also want to sell selectively a new application to some interested mobile device owners. This operation could be performed over the open network. However both device owner and manufacturer should develop a mutual authentication and secured software download. The manufacturer would not like to reveal the software code for security and commercial reasons, at the same time the owner would like to be sure that the manufacturer is the one who is offering the code to be able to let the manufacturer take the responsibility for later device operation. This is a very old and common problem equivalent to software Intellectual Property Right (IPR) protection. A particular software download scenario is presented for mobile device environment and a secured protocol scenario is proposed. The solution includes mainly secret-key mechanisms together with special hardware architecture, which gives the whole process secure and less complex implementation in a mobile environment with low computational power requirements.

Chaos-based detection of LDoS attacks

A low-rate denial of service (LDoS) attack behaves as a small signal in periodic pulses with low average rate, which hides in normal TCP traffic stealthily. LDoS attacks reduce link throughput and degrade QoS of a target. An approach of detecting LDoS attacks is proposed based on Duffing oscillator in chaos systems. The approach detects LDoS attacks by adopting the technology of digital signal processing (DSP), which takes an LDoS attack as a small signal and normal TCP traffic as background noise. Duffing oscillator is used to detect LDoS attacks in normal TCP traffic. Simulations show that the LDoS attacks can be detected through diagram of the chaotic state, and the period and pulse width of LDoS attacks can be estimated.

A Fixed Random Walk Method of potential computation in a conducting spherical shell

The Monte Carlo Methods have been applied with great success to the solution of electromagnetic problems in Cartesian and cylindrical coordinates systems, but have not been widely used in tspherical coordinates system. In this paper, we briefly show the use of a Fixed Random Walk Monte Carlo Method to compute potential distribution in a conducting spherical shell. The results obtained perfectly agreed with those obtained using explicit finite difference method. Also, the approach adopted to overcome singularities encountered in the co-latitude coordinates of the spherical system was highlighted.

Low complexity image authentication for mobile applications

Summary form only given. This paper presents a general technique to simplify processing modular arithmetic in environments having low computational capability such as mobile equipments. We proposed a technique for fast public-key image authentication using fuzzy-computations for El-Gamal authentication technique. The fuzzy operations are embedded carefully in the signature computations to authenticate real time images without performing any real time exponentiations. This results with highly simplified processing at the mobile equipment site allowing relatively high-speed authentication for low-power mobile environment. The technique is rather general and can be deployed similarly for other security mechanisms requiring shifting computation complexity from one particular weak system units to another computationally powerful unit. The fact that power consumption/speed would be an essential issue in hand-held devices makes this technique attractive for many future applications.

Comparison of approximate formulas for the capacitance of microstrip line

In the development of CAD routines at rf or microwave frequencies, closed form models for the capacitance per unit length of microstrip interconnects are easily incorporated. Numerous formulas have been proposed based on analytical, numerical, and empirical approaches. When there are a host of formulas found in the literature, knowledge of their accuracy against measured values and a case study of comparison is all the more vital in the design practice. This paper considers 12 such closed form models published over the past four decades and makes a critical comparison and seeks a way of improving the accuracy. While new formulas are proposed that give rise to less % error compared to few others taken as reference, it is found that composite formulas inherit combined goodness from which they are derived. Our case study provides some interesting results.

A fixed random walk Monte Carlo computation of potential inside two Conducting oblate spheroidal shells

This paper presents a fixed random walk Monte Carlo method for computing potential distribution within two conducting oblate spheroidal shells at different potential. An explicit finite difference method for solving Laplaces equation in oblate spheroidal coordinates systems for an axially symmetric geometry has been developed. This was used to determine the transition probabilities for the fixed random walk Monte Carlo method used. An ingenious strategy was created to overcome the singularity problems encountered in the oblate spheroid pole regions. The potential computation results obtained did fall in the same range with those obtained using finite difference method and exact solution.

Analysis of time-dependent problems using the Exodus method

The Monte Carlo method is well known for solving static problems such as Laplaces or Poisson s equation. In this paper, we extend the applicability of the conventional Monte Carlo method to solve time-dependent (heat) problems. We apply the Exodus method to these problems, which is not subject to randomness, as are the classical Monte Carlo methods. We present results in one- dimensional (1-D) and two-dimensional (2-D) that agree with the exact solutions.