Gervásio P. S. Cavalcante

Comparison between known propagation models using least squares tuning algorithm on 5.8 GHz in Amazon region cities

This paper presents a performance comparison between known propagation Models through least squares tuning algorithm for 5.8 GHz frequency band. The studied environment is based on the 12 cities located in Amazon Region. After adjustments and simulations, SUI Model showed the smaller RMS error and standard deviation when compared with COST231-Hata and ECC-33 models.

A New Parallel Approach for 3D Ray-Tracing Techniques in the Radio Propagation Prediction

A new computational parallel model based on 3D ray-tracing for radio propagation prediction is presented. This approach considers that the main tasks in a 3D ray-tracing technique can be evaluated in an independent and/or parallel way. The workload distribution among the participant nodes of the parallel architecture (cluster of PCs) is performed through a random assignment of the initial rays and the field points for them. Simulations are realized in order to validate and evaluate the performance of the proposed model. The presented results show that the scalability of the model is obtained naturally due to independence of the involved processes. The efficiency of the model presents behavior above the ideal for cases with ostensible processing of rays. These characteristics favor to the increase of the prediction precision through the increase of the density of launched rays and the possibility of incorporation of new propagation mechanisms.

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.

Methodology for analysis of the coverage probability of WLAN using the padé approximant

This paper proposes a methodology for analysis of the signal reception probability in a 2.4GHz Wireless Local Area Network (WLAN). For validating this methodology a measurement campaign was carried out in an indoor environment using an access point as signal transmitter, and a notebook computer, equipped with a wireless board, as receiver. Twenty five average power received values were collected in this environment. Considering that the number of samples was insufficient for statistically characterize the environment, the colleted data was expanded using an Artificial Neural Network (ANN). The propagation loss was calculated using the expanded data in an adapted Pade Approximant model. It was included also, in the model, the number of obstacles intersected by the signal, as well as the loss due to each kind of obstacles. The obtained results were compared to a classical literature model.

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.

Computational parallelization strategy applied in full 3D ray-tracing wireless channel modeling

This paper presents a computational parallelization strategy applied in propagation models based on 3D ray-tracing techniques. This approach considers that the rays are independent from each other, what allows a uniform division of the tasks by equal and random distribution of rays among the parallel computer nodes. The strategy efficiency is proved by simulation where the results are discussed.

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.

Impact of non-stationary noise on xDSL systems : an experimental analysis

Broadband services require data rates that can only be achieved by using relatively high spectrum frequencies. At such high frequencies, the DSL (Digital Subscriber Line) signal is more susceptible to external noise sources, such as radio frequency interference and impulsive noise. This paper aims to characterize how the impulsive noise impacts on services and applications for a broadband system using an ADSL2+ loop. The first approach was to use the impulsive noise defined in the standards G.996.1 (Test Procedures for DSL Transceivers) from ITU-T and TR-048 (ADSL Interoperability Test Plan) from DSL Forum. In this approach we have also used a HDSL (High Bit Rate DSL) and white noise disturbers on the line. The impulsive noises c1 and c2 (defined in G.996.1) are injected into the circuit at the CO (Central Office) end and CPE (Customer Premises Equipment) end of the loop simulator. Additionally, it was analyzed the spikes of noises impact on the ADSL2+ line. In this case, pre-defined models of NEXT (Near-end crosstalk) and white noise are injected on CO and CPE side, simultaneously. Metrics like packet rate, lost packet count, bandwidth, short-term average transfer delay, and errored seconds are used to characterize the DSL loop under the noise impairments.

3D ray-tracing parallel model for radio-propagation prediction

A computational parallel model based on 3D ray- tracing for radio-propagation prediction is presented. This approach considers that the main tasks in a 3D ray-tracing technique can be evaluated in an independent and/or parallel way. The workload distribution among the participant nodes of the parallel architecture (cluster of PCs), is performed through a random assignment of the initial rays and the field points for them. Simulations are realized in order to validate and evaluate the performance of the proposed model.