Murilo Loiola

Bio: Murilo Loiola is an academic researcher from Universidade Federal do ABC. The author has contributed to research in topics: Communication channel & MIMO. The author has an hindex of 6, co-authored 35 publications receiving 116 citations. Previous affiliations of Murilo Loiola include Ericsson & State University of Campinas.

Modified Kalman Filters for Channel Estimation in Orthogonal Space-Time Coded Systems

Abstract: We derive and analyze two modified Kalman channel estimators (KCE) for time-varying, flat, spatially correlated MIMO channels in systems employing orthogonal space-time block codes: the steady-state KCE, which is less complex than the KCE, and the fading memory KCE, which is more robust to model mismatch.

Blind search for optimal Wiener equalizers using an artificial immune network model

Abstract: This work proposes a framework to determine the optimal Wiener equalizer by using an artificial immune network model together with the constant modulus (CM) cost function. This study was primarily motivated by recent theoretical results concerning the CM criterion and its relation to the Wiener approach. The proposed immune-based technique was tested under different channel models and filter orders, and benchmarked against a procedure using a genetic algorithm with niching. The results demonstrated that the proposed strategy has a clear superiority when compared with the more traditional technique. The proposed algorithm presents interesting features from the perspective of multimodal search, being capable of determining the optimal Wiener equalizer in most runs for all tested channels.

Measurement and modeling of short copper cables for ultra-wideband communication

Abstract: High-speed communication using the copper network, originally installed for telephony, is one of the dominant Internet access techniques. Several variants of a technology referred to as digital subscriber line (DSL) have been developed, standardized and installed during the last two decades. Essentially, DSL achieves high rates by exploiting wide bands of the copper cable channel. The shorter the cable, the wider the band that can be used efficiently for communication. Current DSL standards foresee the use of bands up to 30MHz. Cable properties have been studied by means of measurements, characterization and modeling up to frequencies of 30MHz. Recent investigations have shown that it is feasible both from technical and from economical point of view to exploit very short cables (up to 200m) even further and use bands above 30MHz. A prerequisite for further evaluation and the design of such ultra-wideband copper (UWBC) systems is the extension of existing cable models to higher frequencies. This paper presents wideband measurement results of insertion loss and crosstalk coupling in a 10-pair cable of various length values for frequencies up to 200MHz. We compare the results with extrapolations of cable models that are established in the 30MHz-range.

A turbo equalizer using fuzzy filters

Abstract: Turbo equalization is a receiver scheme intended to combat the detrimental effects of intersymbol interference (ISI) in digital transmissions protected by error-control codes (ECC) Traditionally, these equalizers are implemented with the optimal MAP (maximum a posteriori probability), or Bayesian algorithm Thus, considering the close relationship between the fuzzy and Bayesian equalizers, this paper introduces a turbo-fuzzy equalization (TFEQ) approach to cope with ISI and high-power impulse noise effects in broadband digital communication channels Simulation results for power line communication (PLC) channels evidence the applicability of our scheme to overcome the aforementioned impairments when high-rate transmission is considered

Space-Time Block Coding for Wireless Communications

Abstract: II

Coded Communication over Fading Channels

Abstract: In studying the performance of coded communications over memoryless channels (with or without fading), the results are given as upper bounds on the average bit error probability (BEP). In principle, there are three different approaches to arriving at these bounds, all of which employ obtaining the so-called pairwise error probability , or the probability of choosing one symbol sequence over another for a given pair of possible transmitted symbol sequences, followed by a weighted summation over all pairwise events. In this chapter, we will focus on the results obtained from the third approach since these provide the tightest upper bounds on the true performance. The first emphasis will be placed on evaluating the pairwise error probability with and without CSI, following which we shall discuss how the results of these evaluations can be used via the transfer bound approach to evaluate average BEP of coded modulation transmitted over the fading channel.

Intelligent Particle Filter and Its Application to Fault Detection of Nonlinear System

Abstract: The particle filter (PF) provides a kind of novel technique for estimating the hidden states of the nonlinear and/or non-Gaussian systems. However, the general PF always suffers from the particle impoverishment problem, which can lead to the misleading state estimation results. To cope with this problem, a modified particle filter, i.e., intelligent particle filter (IPF), is proposed in this paper. It is inspired from the genetic algorithm. The particle impoverishment in general PF mainly results from the poverty of particle diversity. In IPF, the genetic-operators-based strategy is designed to further improve the particle diversity. It should be pointed out that the general PF is a special case of the proposed IPF with the specified parameters. Two experiment examples show that IPF mitigates particle impoverishment and provides more accurate state estimation results compared with the general PF. Finally, the proposed IPF is implemented for real-time fault detection on a three-tank system, and the results are satisfactory.