Konstantinos B. Baltzis

A Simple 3-D Geometric Channel Model for Macrocell Mobile Communications

One of the fundamental research areas in wireless communications is the development of realistic models that can efficiently and accurately describe the wireless propagation channel. Most of the proposed models disregard the three dimensional character of the signal spread or use techniques with excessive computational complexity. In this paper, we develop a simple 3-D geometric scattering model for the uplink of a macrocell mobile environment that provides the statistics of Angle-of-Arrival (AoA) of the multipath components. The model extends the 2-D geometrical-based single bounce macrocell (GBSBM) model. Explicit closed-form expressions are derived for the statistics of the AoA of the multipaths in the azimuth and elevation planes. Analysis of the results exhibits the advantages of our proposal compared to 2-D and 3-D ones published in the literature. Comparisons with experimental data confirm its validity. Interesting conclusions for the effective evaluation of mobile communication systems have been derived. Moreover, an application of the model to mobile location estimation has been developed and evaluated.

The finite element method magnetics (FEMM) freeware package: May it serve as an educational tool in teaching electromagnetics?

Finite Element Method Magnetics (FEMM) is an open source finite element analysis software package for solving electromagnetic problems. The program addresses 2D planar and 3D axisymmetric linear and nonlinear harmonic low frequency magnetic and magnetostatic problems and linear electrostatic problems. It is a simple, accurate, and low computational cost freeware product, popular in science and engineering. However its educational value has been underestimated. Use of the package in education is quite rare. The aim of this paper is to explore the capability of FEMM to meet as a complementary tool the needs of teaching electromagnetics in higher education. In order to demonstrate its use and exhibit the aid it offers in the teaching of electromagnetics illustrative examples are given. Evaluations in both qualitative and quantitative data have also been conducted and presented. Useful conclusions about its usage and potential applications in the teaching of electromagnetics in higher education are finally drawn.

A Generalized Elliptical Scattering Model for the Spatial Characteristics of Mobile Channels

Geometrically based models are commonly used for the study, analysis and simulation of the wireless propagation channel. This paper presents a two-dimensional geometric scattering model for the description of the angle of arrival (AoA) distribution in mobile environments. In our approach, scatterers are uniformly distributed in hollow ellipses around each communication node. We derive closed-form expressions for the probability density function of the azimuth AoA of the incoming multipaths at each unit and investigate the impact of scatterer distribution on the angular spread of the received signal. Simulation results verify the accuracy of the model. Finally, we show that the proposed method is a generalization of popular geometric channel models.

Analytical and Closed-Form Expressions for the Distribution of Path Loss in Hexagonal Cellular Networks

The development of models that predict path loss in a wireless system is worthwhile since they offer valuable information without the need of expensive and time consuming measurements. In the modeling and simulation of cellular systems, a common assumption in path loss calculation is the circular shape of the cells. However, despite its simplicity, this approach has certain drawbacks. This paper proposes an alternative method that considers hexagonal-shaped cells. Exact analytical and approximate closed-form expressions for the path loss statistics are derived. The validity of the circular cell approximation is discussed. Simulated results and comparisons with measurement data in the literature validate the accuracy of the formulation. Finally, we investigate the impact of the size of the cells and the characteristics of the propagation medium on the path loss. The derived expressions simplify the analysis and system-level simulation of wireless networks. Compared to other methods, they give more accurate results in the calculation of path loss when hexagonal-shaped cells are employed.

A comparative study of common and self-adaptive differential evolution strategies on numerical benchmark problems

Abstract Differential Evolution (DE) is a population-based stochastic global optimization technique that requires the adjustment of a very few parameters in order to produce results. However, the control parameters involved in DE are highly dependent on the optimization problem; in practice, their fine-tuning is not always an easy task. The self-adaptive differential evolution (SADE) variants are those that do not require the pre-specified choice of control parameters. On the contrary, control parameters are selfadapted by using the previous learning experience. In this paper, we discuss and evaluate popular common and self-adaptive differential evolution (DE) algorithms. In particular, we present an empirical comparison between two self-adaptive DE variants and common DE methods. In order to assure a fair comparison, we test the methods by using a number of well-known unimodal and multimodal, separable and non-separable, benchmark optimization problems for different dimensions and population size. The results show that SADE variants outperform, or at least produce similar results, to common differential evolution algorithms in terms of solution accuracy and convergence speed. The advantage of using the self-adaptive methods is that the user does not need to adjust control parameters. Therefore, the total computational effort is significantly reduced.

A comparative study of Particle Swarm Optimization and Differential Evolution on Radar Absorbing Materials design for EMC applications

Radar Absorbing Materials (RAM) design for a desired frequency and angle range is presented. We evaluate the performance of Particle Swarm Optimization (PSO) and Differential Evolution (DE) regarding their applicability to absorber design. The results show that the DE algorithm outerperforms PSO variants.

A Geometric Method for Computing the Nodal Distance Distribution in Mobile Networks

This paper presents a geometrically based method for the calculation of the node-to-node distance distribution function in circular-shaped networks. In our approach, this function is obtained from the intersection volume of a sphere and an ellipsoid. The method is valid for both overlapping and non-overlapping networks. Simulation results and comparisons with methods in the literature demonstrate the e-cacy of the approach. The relation between networks geometric parameters and distance statistics is explored. As an application example, we model distance-dependent path loss and investigate the impact of channel characteristics and networks size on signal absorption. The aforementioned model is a useful and low- complexity tool for system-level modeling and simulation of mobile communication systems.

Cell-to-switch assignment in cellular networks using barebones particle swarm optimization

Cell assignment is an important issue in the area of resource management in cellular networks. The problem is an NP-hard one and requires efficient search techniques for its solution in real-time. In this letter, in order to minimize the cabling and handoff costs, we use two novel discrete particle swarm optimization (PSO) algorithms, the barebones (BB) and the exploiting barebones (BBExp) PSO variants. The impact of network and algorithm parameters on the solution accuracy and computational cost of the methods is investigated. Comparisons with optimization methods in the literature demonstrate the benefits of our proposal.

On the statistical description of the AoA of the uplink interfering signals in a cellular communication system

A common assumption in the analysis and modelling of co-channel interference (CCI) is the circular shape of the cells. However, despite its simplicity, this approach has certain drawbacks. In this paper, we propose an alternative approximate method which considers hexagonal-shaped cells. We develop a geometrical-based stochastic model and derive analytical expressions for the statistics of the angle-of-arrival of the uplink interfering signals in a cellular system. Simulations performed exhibit the characteristics of our proposal and evaluate both hexagonal and circular approximations. The impact of various parameters on the performance of a cellular system is also investigated. The derived expressions simplify the analysis of wireless networks and improve the accuracy of the simulations when hexagonal cells are employed. Copyright

A Geometrical-Based Model for Cochannel Interference Analysis and Capacity Estimation of CDMA Cellular Systems

A common assumption in cellular communications is the circular-cell approximation. In this paper, an alternative analysis based on the hexagonal shape of the cells is presented. A geometrical-based stochastic model is proposed to describe the angle of arrival of the interfering signals in the reverse link of a cellular system. Explicit closed form expressions are derived, and simulations performed exhibit the characteristics and validate the accuracy of the proposed model. Applications in the capacity estimation of WCDMA cellular networks are presented. Dependence of system capacity of the sectorization of the cells and the base station antenna radiation pattern is explored. Comparisons with data in literature validate the accuracy of the proposed model. The degree of error of the hexagonal and the circular-cell approaches has been investigated indicating the validity of the proposed model. Results have also shown that, in many cases, the two approaches give similar results when the radius of the circle equals to the hexagon inradius. A brief discussion on how the proposed technique may be applied to broadband access networks is finally made.