Taufik Abrao

Publications (74) View all

• Conference Proceeding: Fourier and wavelet spectral analysis of EMG signals in isometric and dynamic maximal effort exercise

  J.L. Dantas, T.V. Camata, M.A.O.C. Brunetto, A.C. Moraes, T. Abrao, L.R. Altimari
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  ABSTRACT: Frequency domain analyses of changes in electromyographic (EMG) signals over time are frequently used to assess muscle fatigue. Fourier based approaches are typically used in these analyses, yet Fourier analysis assumes signal stationarity, which is unlikely during dynamic contractions. Wavelet based methods of signal analysis do not assume stationarity and may be more appropriate for joint time-frequency domain analysis. The purpose of this study was to compare Short-Time Fourier Transform (STFT) and Continuous Wavelet Transform (CWT) in assessing muscle fatigue in isometric and dynamic exercise. The results of this study indicate that CWT and STFT analyses give similar fatigue estimates (slope of median frequency) in isometric and dynamic exercise (P<;;003E;0.05). However, the results of the variance was lower for both types of exercise in CWT compared to STFT (P<;;0.05) indicating more variability in the EMG signal analysis using STFT. Thus, the stationarity assumption may not be the sole factor responsible for affecting the Fourier based estimates.
  Engineering in Medicine and Biology Society (EMBC), 2010 Annual International Conference of the IEEE; 10/2010
• Source

  Available from: uel.br

  Conference Proceeding: Reduced tree-search, heuristic and linear decoupler low-complexity MIMO detectors

  I. Suzuki, F. Ciriaco, T. Abrao, L.D. de Oliveira
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  ABSTRACT: Since the optimal detector for coded and even uncoded multiple-input-multiple-output (MIMO) antenna systems results too complex when the number of antennas and/or the modulation order index increases, strictly low-complexity detection schemes are considered, aiming to achieve promising performance times complexity trade-off. Under the same throughput basis, this work analyzes some capacity-approaching heuristic and reduced tree-search MIMO detection algorithms, combining simple linear decouplers, local search detectors, particle swarm intelligence (PSO) concepts and parallel short low density parity check codes (LDPC), suitable to uncoded as well to MIMO channel coding. For uncoded MIMO systems, low-complexity PSO approach showed to reach efficiently MIMO near-capacity for any number of transmit and receive antennas configuration, while simple linear decoupler detectors for QPSK modulation with short LDPC coding achieve reasonable performance only for n_R ges n_T condition.
  Wireless Communication and Sensor Networks, 2008. WCSN 2008. Fourth International Conference on; 01/2009
• Source

  Available from: upc.edu

  Conference Proceeding: GA, SA, and TS near-optimum multiuser detectors for s/MIMO MC-CDMA systems

  T. Abrao, F. Ciriaco, L.D. Oliveira, B.A. Angelico, P. Jeszensky, F. Casadevall
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  ABSTRACT: This paper analyzes the performance and complexity of four heuristic approaches applied to a synchronous multicarrier multiuser detection (MuD) of single/multiple transmit antennas and multiple receive antennas code division multiple access (S/MIMO MC-CDMA) system. The genetic algorithm (GA), simulation annealing (SA) and Tabu search (TS) heuristic algorithms (HA) in a single-objective optimization form were considered. Monte-Carlo simulations showed that the performances, after convergence, achieved by the four near-optimum HA-MuD S/MIMO MC-CDMA are identical. However, their computational complexities differ depending on the operation system conditions. Therefore, the HA-MuD complexities were carefully analyzed in order to determine which one has the best trade-off between bit error rate (BER) performance and implementation complexity aspects.
  Wireless Communication and Sensor Networks, 2008. WCSN 2008. Fourth International Conference on; 01/2009
• Conference Proceeding: Channel reliability in turbo-coded DS/CDMA systems under Rayleigh fading channels

  W. Okano, F. Ciriaco, T. Abrao
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  ABSTRACT: This work proposes a general equation for the channel reliability (L_c) of DS/CDMA turbo coding systems under fading Rayleigh channels and multiple access interference. The proposed reliability equation is suitable for low, medium as well as high signal-noise ratio (SNR) system operation conditions. The L_c equation is established as a function of the ratio of active users and the processing gain (loading system, Q) and SNR from fitting of Monte-Carlo simulation (MCS) performance results. The suggested L_c equation propitiated a lower error rate performance over all SNR operation regions when compared with the previous literature results, considering different loading and coding rate conditions.
  Signal Processing and Communication Systems, 2008. ICSPCS 2008. 2nd International Conference on; 01/2009
• Source

  Available from: uel.br

  Conference Proceeding: Simplified local search multiuser detection for QPSK S/MIMO MC-CDMA systems

  L.D. Oliveira, B.A. Angelico, P.J.E. Jeszensky, T. Abrao, F. Casadevall
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  ABSTRACT: Promising results obtained for a simplified 1-optimum local search multiuser detection (1-opt s-LS-MUD), are extended in this paper to a new scenario, considering quadrature phase shift keying (QPSK) modulation and single/multiple-input multiple-output (S/MIMO) in a multi-carrier code division multiple access (MC-CDMA) system. Furthermore, so as to avoid the complex-valued computation in QPSK formats, the optimization is reformulated as a real-valued problem (also feasible for high-order modulations). Performance is evaluated considering the bit error rate (BER) criterium in order to assure that the proposed algorithm is efficient in accomplishing a good sub-optimum performance, with a relatively low computational complexity. A detailed computational complexity analysis is taken into account, aspiring future implementations.
  Signal Processing and Communication Systems, 2008. ICSPCS 2008. 2nd International Conference on; 01/2009