Jasmine Araújo

The Influence of Interference Networks in QoS Parameters in a WLAN 802.11g : a Bayesian Approach

In spite of the significant increase of the use of Wireless Local Area Network (WLAN) experienced in the last years, design aspects and capacity planning of the network are still systematically neglected during the network implementation. For instance, to determine the location of the access point (AP), important factors of the environment are not considered in the project. These factors become more important when several APs are installed, sometimes without a frequency planning, to cover a unique building. Faults such as these can cause interference among the cells generated by each AP. Therefore, the network will not obtain the QoS patterns required for each service. This paper proposes a strategy to determine how much a given network can affect the QoS parameters of another network, by interference. In order to achieve this, a measurement campaign was carried out in two stages: firstly with a single AP and later with two APs using the same channel. A VoIP application was used in the experiment and a protocol analyzer collected the QoS metrics. In each stage 46 points were measured , that are insufficient for statistically characterize the environment. For expanding this data, an Artificial Neural Network (ANN) was used. After the measurement, an analysis of the results and a set of inferences were made by using Bayesian Networks, whose inputs were the experimental data, i.e., QoS metrics like throughput, delay, jitter, packet loss, PMOS and physical metrics like power and distance.

The influence of interference networks in QoS parameters in a WLAN 802.11g environment

This paper proposes a strategy to determine how much a given network can affect the QoS parameters of another, by interference. In order to achieve this, a measurement campaign was carried out in two stages: firstly with a single AP and later with two APs separated by a distance less than three meters, using the same channel. After the measurement, an analysis of the results and a set of inferences were made by using Bayesian Networks, whose inputs were the experimental data, i.e. QoS metrics such as: throughput, jitter, packet loss, PMOS and physical metrics like power and distance.

Empirical study of the QoS parameters behavior of a VoIP application in wi-fi networks

The use of wireless local area networks (WLANs), as well as the proliferation of the use of multimedia applications has grown fast in recent years. Some factors affect the quality of service(QoS) received by the user. The interference is an example. This work presents an empirical study of the QoS parameters of a VoIP application in the presence of an interference network, as well as the relevance in the design of wireless networks to determine the range of an access point, taking into account several parameters as power, jitter, packet loss, delay and PMOS.

A WLAN planning proposal through computational intelligence and genetic algorithms hybrid approach

This paper proposes a WLAN planning strategy through the use of computational intelligence and genetic algorithm. A measurement technique was used to collect data from a real WLAN network. Metrics like power, distance, delay, jitter, packet loss, throughput and PMOS were analysed through the use of bayesian networks. Finally, to optimize the QoS parameters a genetic algorithm was applied to find the best distance from the AP to support the QoS ITU-T recommendations.

A Visualization Tool for Analyzing the Design of Physical and Network Layers Parameters of a Wireless Network

The use of wireless networks (WLANs, femtocells, Wimax), as well as the increasing use of multimedia applications have grown fast in recent years. Some factors affect the quality of service (QoS) received by the user such as interference. This paper presents a novel data visualization tool for performance evaluation of wireless networks aiding analysis and design of their networks, considering relevant parameters from both physical and network layers (power, jitter, packet loss, delay and PMOS). The performance evaluation is achieved in three steps: measurement, computational intelligence approach through Bayesian networks and mathematical model. The measurement was done implementing an empirical study of the quality of services (QoS) parameters of a VoIP application in the presence of an interference network. Thus, this work is based on a hybrid approach that considers measuring and conditional probability tables, generated from a Bayesian Network, applied to wireless networks, considering QoS parameters. In this work an indoor environment was used to be analyzed but other wireless networks can make use of this visualization tool.

New strategies for planning and performance evaluation of wireless networks: case studies based on the cross-layer approach

The use of wireless local area networks, called WLANs, as well as the proliferation of the use of multimedia applications have grown rapidly in recent years. Some factors affect the quality of service (QoS) received by the user and interference is one of them. This work presents strategies for planning and performance evaluation through an empirical study of the QoS parameters of a voice over Internet Protocol (VoIP) application in an interference network, as well as the relevance in the design of wireless networks to determine the coverage area of an access point, taking into account several parameters such as power, jitter, packet loss, delay, and PMOS. Another strategy is based on a hybrid approach that considers measuring and Bayesian inference applied to wireless networks, taking into consideration QoS parameters. The models take into account a cross layer vision of networks, correlating aspects of the physical environment, on the signal propagation (power or distance) with aspects of VoIP applications (e.g., jitter and packet loss). Case studies were carried out for two indoor environments and two outdoor environments, one of them displaying main characteristics of the Amazon region (e.g., densely arboreous environments). This last test bed was carried out in a real system because the Government of the State of Para has a digital inclusion program called NAVEGAPARA.

The Femtocell as Return Channel: A Proposal for Brazilian Amazon Region Interactive Digital TV

This work analyses the feasibility of use Femtocells networks to provide return channel on Digital TV. The results were compared with a similar simulation using Wimax networks. The same numbers of users was used to create two scenarios, the first using only WiMAX networks, and the second using femtocell network. The results show that femtocell networking is a promising solution for the return channel of Brazilian interactive digital TV, especially at Amazon Region where there are great distances and lacking communication networks.

A metaheuristic hybrid optimization technique for designing broadband FSS

This work presents a metaheuristic hybrid optimization technique developed to synthesize frequency selective surface (FSS) structures, composed of triangular patch elements and printed on FR-4 dielectric substrates for microwave filtering applications. The optimization technique is based on the combination of genetic algorithm (GA) and Multilayer Perceptron (MLP) artificial neural network (ANN). The developed MLP model for FSS synthesis was performed for efficient evaluation of cost function in GA iterations. The advantages in the optimal design of FSS through the proposed GA-ANN technique are discussed in terms of convergence and computational cost. An optimized FSS prototypes were fabricated and measured. The accuracy of the proposed optimization technique was verified through the good agreement obtained by means of comparison between theoretical and experimental results.

Modeling electromagnetic wave propagation in the UHF range using the MoM to assess NIR exposure level

A computational method for predicting electromagnetic wave propagation in the UHF range using the method of moments (MoM) is proposed. National regulation represented by the resolution No. 303/2002 of the National Telecommunications Agency (ANATEL) joined the guidelines of the International Commission on Non-Ionizing Radiation Protection (ICNIRP) for limiting the human exposure to electromagnetic fields. There are several methods to assess the exposure level but the MoM is suitable for both far and near-field in an open topology through numerical simulation. The objective of this work is to evaluate the levels of non-ionizing radiation that the population, inhabiting adjacent areas of the antenna, will be submitted. This also estimates the protection zone from the frequency and feed power values. Most importantly, the method enables calculations to be performed using different antenna heights and different power levels. A brief discussion of the computational implementation of the propagation model is presented, followed by an example that demonstrates the diagram of the exposure level generated. Comparison with ITU-T 1546-4 propagation model and two ray model are also presented.

Influenceof polarization effects of the antennas in a WLAN coverage area

Electromagnetic waves are affected by different phenomena along their propagation. In addition to signal scattering, the polarization of the transmitting and receiving antennas should be considered because the effect of different polarizations causes loss of reception. Such polarization affects the parameters of quality of service (QoS). In this paper, a methodology for wireless local network (WLAN) project is presented. It is based on measurements of received power and QoS parameters. The obtained results were evaluated using a network qualifier which will be used to establish the access point coverage area.