João C. W. A. Costa

Automatic modulation classification for cognitive radio systems: Results for the symbol and waveform domains

This work presents two approaches to the problem of automatic modulation classification in cognitive radios. The first approach deals with classifying distinct QAM modulations. The proposed solution consists of a SVM classifier that uses as input parameters the distance between the received symbol and its nearest neighbor in each constellation. The results obtained by the proposed classifier is compared to a state-of-art technique. The comparison show a good performance for the 16-QAM, 32-QAM and 64-QAM modulation schemes. In the second approach, the cyclic spectral analysis is adopted as the method for extracting the signals features, and the SVM classifier is used for the pattern recognition stage. The proposed method achieved excellent results for the AM, BPSK, QPSK and BFSK modulation schemes. In both approaches, different scenarios are evaluated which may serve as a starting point for researchers who want to compare results systematically.

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.

Fiber Bragg optimization using parallel processing and genetic algorithm

In this work are presented two designs of fiber Bragg gratings optimized by using genetic algorithm and parallel processing. The results achieved show the robustness of that technique when applied to complex search spaces. Besides, it is shown that the use of the parallel processing improves the performance of genetic algorithm.

Remote curvature fiber sensors using core mismatch structures and OTDR based interrogation

In this work, a remote curvature sensor using a standard OTDR as the interrogation system is presented. This approach uses a core diameter mismatch sensor which is formed by a short section of a multimode fiber, with a length of 3 mm, sandwiched between two singlemode fibers. In this case, the attenuation of the optical signal will vary as the fiber is bent allowing interrogating the sensor with OTDR technology. Preliminary results indicate a resolution range of ~0.0003 cm- 1, sensitivity in the range of ~-208.46 dB/cm-1 and a variation of 2.67 dB in the OTDR trace within the bend radius range.

Markovian Approach to Time Transition Inference on Bayesian Networks

Also known in literature as belief networks, causal networks or probabilistic networks, Bayesian networks (BN) can be seen as models that codify the probabilistic relationships between the variables that represent a given domain (Chen, 2001); being one of the most prominent when considering the easiness of knowledge interpretation achieved. These models possess as components a qualitative (representing the dependencies between the nodes) and a quantitative (conditional probability tables of these nodes) structure, evaluating, in probabilistic terms, these dependencies (Pearl, 1988). Together, these components provide an efficient representation of the joint probability distribution of the variables of a given domain (Russel and Norvig, 2003).

New Applications Using PLCs in Access Networks

Access Networks in telecommunications, such as digital subscriber lines (DSL) and wireless broadband networks (WBN) have become so popular that these systems are now found in almost all regions. The widespread use of these systems has brought about the need for research into new ways of resolving, or at the very least, minimizing the impact of problems that affect the performance of these systems. In terms of DSL systems, crosstalk is one of the main performance limiting factors, principally when operating at high frequencies, as is the case with VDSL (very-high-bit-rate DSL) networks. Consequently, the required high data rates of VDSL systems may not be achievable if crosstalk levels are excessive. Across WBN systems, the existence of co-channel interference increases the systems noise levels and also degrades the networks overall performance. It may be impossible therefore, depending on the noise level, to get even minimum system access. It is therefore necessary to plan a way of controlling these noise levels across both access networks. Programmable logic controllers (PLCs) are the main types of controllers used within the industry. One of their characteristics is the fact that they can operate within aggressive environments (for example, at high temperatures or within high humidity levels) as well as having high operational speeds in comparison with corresponding electro-mechanic control systems; the PLC becoming a highly efficient control device with multiple usage possibilities. Hence, the use of PLCs across access networks opens up additional fields of application for this type of device, especially due to the fact that up until now, the PLC’s widest form of use has been in the industrial sector. Additionally, the robustness, flexibility and speed of the PLC allows it to be used across access networks without any additional need for major configuration changes to already installed equipment, i.e.; the implementation of a PLC into a system does not generate excessive costs or require excessively specialized configurations. PLC application will focus on automated configurations in order to reduce system noise on access networks (DSL and WBN) with the intention of making sure the performance levels of these systems are not degraded in any way and are also able to operate within the expected performance parameters. In this chapter, we propose alternative PLC applications on two types of broadband networks. Basic concepts about DSL networks and wireless broadband networks are presented in section 2. In section 3 the application of PLC on broadband networks is discussed. Final comments are presented in section 4.

Performance evaluation of load forecasting models for energy purchase of power suppliers in the Amazonian region

One of the most desired aspects for power suppliers is the acquisition/sell of energy in a future time. This paper presents a study of load forecasting for power suppliers, presenting a comparative application of the techniques of wavelets, time series methods and neural networks, considering short and long term forecast; both of great importance for power suppliers in order to define the future power consumption of a given region.