Marcelino S. da Silva

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.

A feasibility study of powerline communication technology for digital inclusion in Brazilian Amazon

In the current national scene, many actions point at projects of digital inclusion and citizenship. In this context, providing access technologies as a requisite for the implementation of these actions is primordial. In this way, many innovative experiences have been presented in the past few years. This paper presents a study on the Powerline Communication- PLC technology; as a proposal for a feasible access network for Brazilian Amazon. First, the characteristics of the PLC technology are studied from an implanted indoor prototype at Federal University of Para. The measures used in this prototype serve as input for a created model, from which it is intended to study the system more widely, considering factors such as: scalability, reliability and the physical characteristics.

Performance evaluation of IPTV traffic over pDSL

The increasing trend of triple play traffic transmission (voice, video and data) over internet is a worldwide phenomenon. However, to get a satisfactory communication, we need study the process on end-the-end way. Into regions with little infrastructure of telecommunications, one of the concerns is about used technologies of access. This work presents an analysis based on an IPTV (Television Internet Protocol) transmission generated on two combined technologies of access, PLC (PowerLine Communications) and ADSL2+ (Asymmetric Digital Subscriber Line), using a combination of electric network and telephony infrastructure, called of pDSL. This technology is a viable combination for regions with poor infrastructure of telecommunications. The results are evaluated with intention to present the viability of this kind of the telecommunication environment and with a simulation for extrapolation study.

A feasibility study of PLC technology for digital inclusion

In the current national scene, many actions point at projects of digital inclusion and citizenship. In this context, providing access technologies as a requisite for the implementation of these actions is primordial. In this way, many innovative experiences have been presented in the past few years. This paper presents a study on the powerline communication - PLC technology; as a proposal for a feasible access network for Brazilian Amazon. First, the characteristics of the PLC technology are studied from an implanted indoor prototype at Federal University of Para. The measures used in this prototype serve as input for a created model, from which it is intended to study the system more widely, considering factors such as: scalability, reliability and the physical characteristics.

Comparative Analyses of Computational Intelligence Models for Load Forecasting: A Case Study in the Brazilian Amazon Power Suppliers

One of the most desired aspects for power suppliers is the acquisition/sale of energy for a future demand. However, power consumption forecast is characterized not only by the variable of the power system itself, but also related to socio-economic and climatic factors. Hence, it is imperative for the power suppliers to design and correlate these parameters. This paper presents a study of power load forecast for power suppliers, comparing application of techniques of wavelets, time series analysis methods and neural networks, considering long term forecasts; thus defining the future power consumption of a given region. The results obtained proved to be much more effective when compared to those projected by the power suppliers based on specialist information, thus contributing to the decision making for acquisition/sale of energy at a future demand.

Multimedia Transmission over Optic, DSL and PLC Systems

This work presents an analysis based on an multimedia transmission generated on optical fiber backbone and two combined access technologies, PLC (Power Line Communications) and ADSL2+ (Asymmetric Digital Subscriber Line), called of pDSL. This paper points a case study of multimedia traffic using pDSL combination with intention to present measured and simulated results that prove the proposal solution viability.

Triple play service under the impact of nonstationary noise in a DSL system: an Amazon approach

The Brazilian Amazon has sui generis characteristics that affect strongly the communication technologies, such as high humidity and temperature. These characteristics cause impact in the existent infrastructure, especially in twisted-pair copper lines. At the moment, new services are based on multimedia applications, as voice over internet protocol (VoIP), video on demand (VoD), and internet protocol television (IPTV). Such services use digital broadband networks such as ADSL2+ (Asymmetric Digital Subscriber Line) to transmit the data. Broadband services require data rates which can only be achieved by using relatively high spectrum frequencies. At high frequencies the DSL signal is more susceptible to external noise sources, such as radio frequency interference and impulsive noise. For this purpose, an experimental setup has been built at UFPA that consists of noise generator, traffic generator, real cables, modems and DSLAM (digital subscriber line access multiplexer). This paper aims at characterizing how the noise impacts on triple play services for a broadband system using a DSL loop on Amazon environment. The objective of the noise impact experimentation is to observe the behavior of a DSL system under more realistic but controlled line conditions. Metrics as lost packet, jitter, latency, and throughput are used to characterize the triple play service in a DSL loop under the noise impact. Through the real experiments and controlled loop conditions, this paper allow identify, from application level point of view, how robust DSL system is in respect to noise occurrence. Additionally, it is described a methodology for noise impact measurements using a DSL system.

Clustering techniques for data network planning in Smart Grids

Smart Grid, a modern approach to electricity distribution, requires innovation on various fronts. Communication is a key component of Smart Grid applicability. To satisfy Quality of Service (QoS) needs when deciding on network structure and topology, especially in urban areas, artificial intelligence techniques may be applied. Techniques such as clustering methods or genetic algorithms are useful to resolve this optimization problem. Choice of network topology for a specific electrical grid is also important. This choice influences the resulting QoS and network implementation price. This paper uses graph theory formulation to create a model. This model is designed to optimize topology of data network while accounting for delay constrains. Since this problem belongs to class NP-hard, this paper indicates appropriate clustering methods that best suit a given Smart Grid scenario in terms of QoS. A typical wireless network planning scenario of electric energy distribution is used as a case study. Each resulting cluster will contain a base station to attend the needs of Smart Grid Intelligent electronic devices in its cluster area. The algorithms K-medoids and K-means had the best performance with K-medoids bringing financial benefits regarding base station deployment.

QUÃO ACURADAS SÃO AS PROJEÇÕES FINANCEIRAS E ATUARIAIS DO REGIME GERAL DA PREVIDÊNCIA SOCIAL

O presente artigo procura aferir o grau de confiabilidade das previsoes fiscais e atuariais de deficit no Regime Geral de Previdencia Social (RGPS) realizadas pelo governo federal, comparando os dados da Lei de Diretrizes Orcamentarias dos anos de 2002 a 2015 com os resultados efetivamente realizados nas estatisticas oficiais. A pesquisa constata erros de elevada magnitude entre os valores previstos e realizados para a receita, despesa e deficit do sistema previdenciario, para a maioria dos anos, tornando as previsoes realizadas sem qualquer significado. A investigacao sobre as causas dos erros das projecoes levaram a conclusao de que o modelo atuarial do governo federal apoia-se em metodologia impotente para produzir resultados confiaveis. As razoes detectadas vao desde o congelamento, nos valores do ano de 2009, das variaveis do mercado de trabalho ao longo de quatro decadas, ate a inusitada taxa de reajuste do salario minimo acima do PIB e da inflacao. O artigo conclui que o modelo atuarial que pautou a proposta de reforma da previdencia de 2016 foi desenhado para subestimar receitas e superestimar gastos com beneficios, pois esta apoiado em metodo que, apesar de simular infalibilidade, apresenta lacunas logicas. Palavras-chave: Seguridade Social. Modelo atuarial. Reforma da Previdencia

Financial forecasts accuracy in Brazil’s social security system

Long-term social security statistical forecasts produced and disseminated by the Brazilian government aim to provide accurate results that would serve as background information for optimal policy decisions. These forecasts are being used as support for the government’s proposed pension reform that plans to radically change the Brazilian Constitution insofar as Social Security is concerned. However, the reliability of official results is uncertain since no systematic evaluation of these forecasts has ever been published by the Brazilian government or anyone else. This paper aims to present a study of the accuracy and methodology of the instruments used by the Brazilian government to carry out long-term actuarial forecasts. We base our research on an empirical and probabilistic analysis of the official models. Our empirical analysis shows that the long-term Social Security forecasts are systematically biased in the short term and have significant errors that render them meaningless in the long run. Moreover, the low level of transparency in the methods impaired the replication of results published by the Brazilian Government and the use of outdated data compromises forecast results. In the theoretical analysis, based on a mathematical modeling approach, we discuss the complexity and limitations of the macroeconomic forecast through the computation of confidence intervals. We demonstrate the problems related to error measurement inherent to any forecasting process. We then extend this exercise to the computation of confidence intervals for Social Security forecasts. This mathematical exercise raises questions about the degree of reliability of the Social Security forecasts.