Adaptive Beamforming for Antenna Arrays in Cellular Systems Based on a Duality Between Uplink and Downlink Channels

Ciro A. Pitz, Marcelo G. Vanti, Orlando J. Tobias, Rui Seara

DOI: 10.14209/sbrt.2010.23

Keywords: Adaptive antenna arrays beamforming algorithm duality approach LMS-based algorithm

Abstract

This paper presents a beamforming algorithm for antenna arrays attending to both power and signal-tointerference-plus-noise (SNIR) ratio constraints. The proposed adaptive approach makes use of the least-mean-square (LMS) algorithm as well as exploits the duality idea between uplink and downlink channels. Since a reference signal is used, the proposed approach does not require any direction-of-arrival (DoA) algorithms for estimating the angle-of-arrival (AoA) of the signals. The proposed algorithm exhibits both low computational complexity and very good stability conditions. Through numerical simulations the performance of the proposed algorithm is verified.

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Non-Parametric VSS-NLMS Algorithm With Control Parameter Based on the Error Correlation

José Gil F. Zipf, Orlando J. Tobias, Rui Seara

DOI: 10.14209/sbrt.2010.108

Keywords: adaptive filters adaptive signal processing variable step-size least-mean-square (VSSLMS) algorithm

Abstract

The behavior of variable step-size least-mean-square (VSSLMS) algorithms is strongly affected by measurement noise. Thereby, aiming to maintain an adequate performance of these algorithms, their parameters must be adjusted whenever changes occur in the signal-to-noise ratio (SNR) of the adaptive system. A well-known VSSLMS algorithm based on error correlation provides a performance enhancement for low SNR environment; however, its immunity to measurement noise changes is still poor. This paper presents a new nonparametric variable step-size normalized LMS (VSS-NLMS) algorithm with control parameter based on error correlation. This approach is very robust to measurement noise changes, not requiring any manual adjustment of algorithm parameters. Numerical simulation results confirm the effectiveness of the proposed algorithm, considering a system identification problem.

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On the Use of Precoding in FBMC/OQAM Systems

Bruno S. Chang, Carlos A. F. da Rocha, Didier Le Ruyet, Daniel Roviras

DOI: 10.14209/sbrt.2010.109

Keywords:

Abstract

Linear precoding can be applied to multicarrier systems to minimize the effect that a deep fade in one of the subchannels can have on the overall bit error ratio when the transmitter does not have channel state information (CSI). But for filterbank multicarrier (FBMC) systems, which were proposed to overcome the poor spectral characteristics and bandwidth/energy waste caused by the use of the cyclic prefix, there are very few proposals of precoded systems in the literature. This paper proposes a precoded SISO (single-input single-output) filterbank multicarrier system with zero-forcing (ZF) and minimum mean square error (MMSE) equalization. Results show that in a well-equalized system, the Monte Carlo simulation results match the ones provided by the BER approximation presented in this paper. However, in systems with residual interference, the Monte Carlo results drift from the approximation at high SNR values, with the error performance from precoded FBMC systems being more affected by the unequalized interference.

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Detection of Panoramic Takes in Soccer Videos Using Phase Correlation and Boosting

Luiz G. L. B. M. de Vasconcelos, Sergio L. Netto, Eduardo A. B. da Silva

DOI: 10.14209/sbrt.2010.31

Keywords:

Abstract

We propose an automatic engine for panoramic-take detection which relies on an algorithm based on phase correlation and boosting. The motion between two sequential video frames is first estimated through a phase correlation. Then, we are able to extract motion parameters and apply post-processing operations on these parameters in order to feed an AdaBoost-based classifier. The proposed algorithm has been validated over 5 segments of videos of 10000 frames each. Panoramic frame detection achieved around 85% recall and 76% accuracy on a validation set of videos not belonging to the training set.

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Modelling Power Consumption in IEEE 802.16e WiMAX Mobile Nodes

N´ıbia S. Bezerra, Fuad M. Abinader Jr., Vicente A. de Sousa Jr., Gino Lozada, Pekko Orava

DOI: 10.14209/sbrt.2010.32

Keywords:

Abstract

Energy availability is the main delimiter for usage time of mobile devices. As wireless network interfaces are usually the most power-demanding subsystem in a mobile device, mechanisms for their power consumption optimization are extensively researched. However, determining the power saving gains from using such optimizations is not an easy task, specially for simulation-based analysis. This work presents an extended power consumption model for the WiMAX interface in Mobile Nodes (MN), capable of capturing minimal contributions such as signalling overhead or burst allocation geometry. Simulation results show an effectiveness comparison of discussed power consumption models.

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A Low-Cost Implementation of High-Order Square M-QAM Detection/Demodulation in a FPGA Device

Gléverson Fabner Condé Lemos, Marcos Vinícius Silva Oliveira, Fabrício P. V. de Campos Luciano Manhães de Andrade Filho, Moisés Vidal Ribeiro

DOI: 10.14209/sbrt.2010.33

Keywords:

Abstract

This paper outlines a low-cost technique for detection/demodulation of high-order square M-ary quadrature amplitude modulation (M-QAM), M = 4, 16, 64, 256, 1024, and 4096, in a field programmable gate array (FPGA) device. Hence, it is very interesting for advancing high-speed power line communication technology. The proposed technique is based on a so-called heuristic decision region approach combined with a nonlinear function that allows to simplify the hardware implementation of detection and demodulation for a high-order square M-QAM symbols. The performance evaluation of the proposed technique is carried out when the channel is additive white Gaussian noise (AWGN) and additive impulsive Gaussian noise (AIGN). The attained results, in terms of bit error rate vs. energy per bit to noise power spectral density ratio (Eb/N0), indicate that the use of the proposed technique offers reduced performance losses. Also, its implementation in a FPGA device demands the lowest hardware resource and latency.

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Hardware-Friendly Implementation of Soft Information Set Decoders

A. Gortan, R. P. Jasinski, W. Godoy Jr., V. A. Pedroni

DOI: 10.14209/sbrt.2010.34

Keywords: soft-decision information set decoding Dorsch algorithm hardware implementation FPGA VHDL

Abstract

This article has two main purposes: (i) to introduce and evaluate a modified version of the Dorsch soft decoding algorithm for block codes, based on information sets, and (ii) to examine the complexity of implementing this kind of decoder in hardware (more specifically, in FPGA devices). The modifications introduced in the algorithm lead to an optimized circuit size when the algorithm is implemented in hardware. Indeed, the physical implementation and its detailed analysis represent a major departure from traditional decoder analysis, increasingly important as more frequently such specialized functions are embedded into the hardware, in top-performance systems. It is demonstrated that, in the worst case, n – dmin + 1 iterations suffice to find the most reliable information set, from which only a very small fraction of all 2k possible candidate codewords needs to be tested to achieve near maximum likelihood decoding (MLD) performance. These conclusions are confirmed by simulations on a C(48, 24, 12) block code, then used as guidelines in the physical implementations of several decoders, in order to test their real-time operation. A detailed circuit diagram is presented, along with experimental results indicating the number of logic cells and registers needed to implement the decoder in a high-end FPGA, for various code sizes.

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A Contribution for Spectrum Sensing in Power Line Communication Systems

Laryssa R. Amado, Thiago R. Oliveira, Moisés V. Ribeiro

DOI: 10.14209/sbrt.2010.35

Keywords:

Abstract

In Brazil, the introduction of telecommunication and electric energy regulations for power line communications (PLC) is pushing forward R&D efforts towards the development of this technology. Therefore, the will to improve the usage of the regulated spectrum and its further increase, combined to the necessity of PLC system coexistence with other users of the regulated bandwidth made spectrum sensing an important matter to be addressed. To do so, it is needed to determine the best way to acquire information of the surrounding spectrum: using an antenna or measuring the interference on the power line cable. To offer subsidy to this discussion, measured data for spectrum sensing, which were acquired in Brazil, are presented and analyzed. Also, the performance of energy-detection technique for PLC spectrum sensing is evaluated with this measured data. Based on the qualitative and quantitative analysis, this contribution indicates that an antenna can be a very interesting sensor for cognitive PLC systems.

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A Linearly Constrained IQRD-RLS Algorithm for Blind Multiuser Detection in CDMA Systems

César A. Medina, Raimundo Sampaio-Neto

DOI: 10.14209/sbrt.2010.104

Keywords: CDMA blind receiver estimation linearly constrained minimum variance IQRD-RLS filtering constrained RLS

Abstract

In this paper we propose an inverse QR decomposition based recursive least squares algorithm (IQRD-RLS) for the linearly constrained minimum variance (LCMV) receiver for CDMA transmission systems. The proposed algorithm is numerically stable in finite precision environments and it is suitable for implementation in systolic arrays or DSP vector architectures. It is shown through computer simulations that the proposed algorithm outperforms, in terms of bit error rate, previously proposed IQRD-RLS based blind detection algorithms.

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Speaker Recognition Using Dynamic Features and The Null Space Combination of Classifiers in The Sub-band Domain

Eduardo Esteves Vale, Abraham Alcaim, Rosângela Coelho

DOI: 10.14209/sbrt.2010.36

Keywords: Delta features delta-delta features multiple subband-classifiers speaker recognition

Abstract

This paper investigates the inclusion of dynamic features in the input vectors used by the multiple classification scheme which employ the null space to combine the likelihoods. Speaker identification experiments were performed considering four ambient noise and also different mismatched conditions. The results show that this strategy can contribute to increase the recognition accuracy.

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