Frequency-Domain Blind Source Separation employing a Non-Uniform DFT

Diego B. Haddad, Mariane R. Petraglia, Paulo Bulkool Batalheiro

DOI: 10.14209/sbrt.2010.52

Keywords:

Abstract

Blind source separation (BSS) techniques have been extensively investigated in the last years, due to their large number of applications. There are two main approaches employed for such techniques: in the time-domain and in the frequencydomain. In this paper, we propose the use of a non-uniform DFT transform as a strategy for improving the behavior of two frequency-domain BSS algorithms.

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An Innovation-Based Algorithm for Energy Conservation in Multihop Wireless Sensor Networks

Felipe da Rocha Henriques, Lisandro Lovisolo, Marcelo Gonçalves Rubinstein

DOI: 10.14209/sbrt.2010.53

Keywords: Wireless Sensor Networks Innovation Energy Multihop Reconstruction

Abstract

We propose an energy-efficient algorithm for sensing a process f(x,y,t) using a multihop Wireless Sensor Network (WSN). The innovation-based algorithm aims at saving node energy by managing the transmission necessity. The nodes can also switch to an inactivity state, between innovative transmissions. When a node needs to send data, it transmits its inactivity period attached within the packet. Then, forwarding nodes (in the route path) can sleep without affecting the communication process. Results show that a gain up to twenty times was obtained in the network lifetime, with a significant decrease in the amount of transmission by sensors, as compared to a network without any kind of node energy management strategy.

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Enhancement of Data Rate for User Cooperation

Mitchell Omar Calderon Inga, Gustavo Fraidenraich

DOI: 10.14209/sbrt.2010.117

Keywords: user cooperation virtual MIMO bit error probability

Abstract

In this paper, we propose a different scheme based on user cooperation diversity, in which we obtain an increase in the data rate. In particular, we present performance analysis using conventional CDMA (code division multiple access) implementation for two users. Cooperation among users has been shown to achieve significant gains as compared to a non-cooperative system. The results presented here show that the new scheme of cooperation achieves substantial increase of data rate, keeping the average bit error probability close to values obtained in [3]. Regarding the number of spreading codes, there are costs associated with our cooperative scheme, but even so our proposed strategy leads not only to an increase in throughput but also to a simpler system.

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Performance comparison between single-carrier and OFDM using the cutoff rate

Amanda de Paula, Cristiano Panazio

DOI: 10.14209/sbrt.2010.54

Keywords: OFDM frequency domain equalization singlecarrier DFE cutoff rate channel coding

Abstract

This article aims to establish a performance comparison between the Single Carrier with Cyclic Prefix (SCCP) and the Orthogonal Frequency Division Multiplexing (OFDM) systems in terms of the cutoff rate. We consider both linearly equalized SCCP (LE-SCCP) and the SCCP equalized with a decision feedback equalizer (DFE-SCCP). A theoretical approach to the problem is proposed and simulation results showing the cutoff rate for several coding rates are also presented. Still, the systems BLER are evaluated and its dependency on the coding rate are analyzed and compared to the behavior shown by the cutoff rate analysis.

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Traffic Influence in Distributed Networks Using Cooperation and Set-Membership Filtering

Marco Fernandes S. Xaud. Diego A. Zanon, Ana Luiza Dallora

DOI: 10.14209/sbrt.2010.55

Keywords: sensor networks adaptive filters cooperation setmembership adaptive filtering

Abstract

This paper investigates the influence of data loss in the performance of cooperative adaptive filters in distributed networks. The algorithms analyzed are those with and without data selection based on innovation. Our simulation results indicate that set-membership adaptation algorithms, which perform some form of innovation check prior to transmission of data to the neighbors, have better performance than their counterparts which flood the network with data at every iteration. Therefore the space-time data selection of set-membership adaptive filters reduces computational complexity and energy consumption, and also improves convergence performance in case of data loss during transmission.

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Evaluation of the Effects of Co-Channel Interference on the Bit Error Rate for QPSK and M-QAM Modulations

Edgar Benítez, Gina Quelal, Diana Moya, Daniel Altamirano, Celso de Almeida

DOI: 10.14209/sbrt.2010.44

Keywords: M-PAM Q-PSK M-QAM Co-Channel Interference SIR BER

Abstract

In this paper, a performance analysis for QPSK, 16- QAM and 64-QAM, modulations in the presence of co-channel interference is made. At first, an expression of the bit error rate (BER) for M-PAM as a function of the Eb=N0 ratio in the presence of K interferers is obtained. The formula from the BER gotten earlier is used to derive a simplified expression for the BER of M-QAM modulations. For each modulation scheme, it is shown that there is a minimum signal to interference ratio (SIR) for the system does not present a BER floor. The results obtained show that modulations with higher order alphabets need high SIR in order to maintain the BER at satisfactory levels. This analysis can be applied in the performance evaluation of cellular radio networks, as WiMAX and LTE.

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A speech database for the study of Lombard effect in Brazilian Portuguese

David Daniel e Silva, Carlos Alberto Ynoguti, Marcelo Ricardo Stemmer

DOI: 10.14209/sbrt.2010.56

Keywords: Automatic speech recognition Lombard effect speech database

Abstract

The Lombard effect is related to the change in the way people speak in noisy environments in order to compensate the degradation of the audio signal. There are significant changes in the duration of some types of phones and in the formant positions that can vary from a language to another. The construction of a speech database that isolates the Lombard effect is a challenging task because its necessary to record only the speech signal, without the environment noise. In this paper a methodology to construct such databases is described and a database for the Brazilian Portuguese was produced using this procedure

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Improving EGPRS Capacity using Orthogonal Sub Channels (OSC)

F. M. L Tavares, R. F. Iida, R. D. Vieira, R. C. D. Paiva

DOI: 10.14209/sbrt.2010.118

Keywords: GERAN Evolution EGPRS OSC Capacity

Abstract

Due to the increasing demand for data services in mobile networks, operators are observing the quality of data services to degrade as their packed switched (PS) resources become insufficient. Even though there are newer 3/4G technologies available, EGPRS is still a good solution for data services due to ubiquitous coverage, the availability of low cost user terminals and its low deployment costs. Hence, alternative solutions are needed to deal with this increased data traffic without affecting the voice services, which play an important role in GSM networks. This paper presents a study on the usage of the Orthogonal Sub Channels (OSC) for improving voice capacity in order to increase the available resources for PS data services in a GSM/EGPRS network, showing that along with OSC it is possible to increase the number of EGPRS subscribers without extensive capital expenditure, such as increasing the number of radios or acquiring further spectrum resources.

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User Cooperation Using Multiple Antennas

Carmen Lúcia Avelar Lessa, Gustavo Fraidenraich

DOI: 10.14209/sbrt.2010.57

Keywords: User cooperation multiple-input multiple-output (MIMO) systems multiuser channel decorrelator SVD

Abstract

This paper proposes user cooperation strategy using multiple antennas technology (MIMO). In a first model we used a Code Division Multiple Access (CDMA) system and in a second model we apply the techniques of the decorrelator and Singular Value Decomposition (SVD) to allow cooperation. We show how cooperation using different numbers of antennas can be accomplished. It was considered a cooperation scheme for MIMO MAC channel with two users having single antenna and the receiver with two antennas. The results show that user cooperation with multiple antennas reduces the bit error probability.

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Distributed Autonomic Inference Machine for Wireless Sensor Networks

Nídia Glória da Silva Campos, Danielo G. Gomes, José Neuman de Souza

DOI: 10.14209/sbrt.2010.58

Keywords: WSN Fuzzy Logic Self-Configuration

Abstract

Wireless Sensor Networks (WSNs) offer data to Intelligence Ambient system, but, due the big number of sensor nodes and data heterogeneity, it can be overload by them. This paper proposes MIAD, a distributed autonomic inference machine which uses fuzzy logic to make ambient context and to self-configure sensing and dissemination rates and minimize redundant context of WSN. Tests with Crossbow micaz motes and temperature and relative humidity sensors show that MIAD sends more relevant risk fire context messages to final system while it saves WSN energy. It presents better results than distributed WSN application without self-configuration and an autonomic engine based on crisp rules.

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