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Signal Processing Letters, IEEE

Issue 8 • Date Aug. 2009

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Displaying Results 1 - 25 of 34
  • [Front cover]

    Page(s): C1
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    Freely Available from IEEE
  • IEEE Signal Processing Letters publication information

    Page(s): C2
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    Freely Available from IEEE
  • Table of contents

    Page(s): 641 - 642
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    Freely Available from IEEE
  • Performance Analysis of Amplify-and- Forward Opportunistic Relaying in Rician Fading

    Page(s): 643 - 646
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (300 KB) |  | HTML iconHTML  

    This letter analyzes the performance of single relay selection cooperative wireless networks using amplify-and forward relaying. The network channels are modeled as independent, nonidentical, Rician distributed coefficients. We derive approximate formulas for the symbol error rate (SER) of the opportunistic relaying cooperative network. We first derive the PDF of the approximate value of the total SNR. Then, assuming M-PSK or M-QAM modulations, the PDF is used to determine the SER. For sufficiently large SNR, this letter derives the close-form average SER. The simplicity of the asymptotic results provides valuable insights into the performance of cooperative networks and suggests means of optimizing them. We also use simulation to verify the analytical results. Results show that the derived error rates are tight bounds particularly at medium and high SNR. View full abstract»

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  • Weighted Distance Based Sensor Selection for Target Tracking in Wireless Sensor Networks

    Page(s): 647 - 650
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (207 KB) |  | HTML iconHTML  

    A novel weighted distance based node selection method for bearings-only sensors in wireless sensor networks (WSN) is proposed. Weighted distance is involved as information utility in sensor management of WSN. Based on the probability distribution function of predicted target state and the bearing error of a sensor itself, the sensor with the minimum weighted distance is activated in the tracking mission. Compared with entropy based method, the proposed method saves much computational cost by avoiding the estimation of the posteriori distribution. Simulation results demonstrated that the proposed method can achieve competitive tracking accuracy comparing to the existing representative methods. View full abstract»

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  • Theoretical Characterization of Memory Polynomial Models With Gaussian Inputs

    Page(s): 651 - 654
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (137 KB) |  | HTML iconHTML  

    We consider distortion of a Gaussian signal by a memory polynomial system and prove a theorem about a linear representation of the output. As an application example, we analyze an OFDM system with a nonlinear high power amplifier at the transmitter. View full abstract»

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  • Cramer–Rao Bounds for Hybrid TOA/DOA-Based Location Estimation in Sensor Networks

    Page(s): 655 - 658
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (469 KB) |  | HTML iconHTML  

    This letter derives the Cramer-Rao bound (CRB) for source location estimation using joint time-/direction-of-arrival (TOA/DOA) measurements collected in a wireless sensor network setup. Each sensor is capable of measuring both TOA and DOA from a signal source, which enables it to estimate the source's location individually. Data fusion is then employed to reach a global position estimate. For both optimal measurement fusion and linear state fusion, we derive the CRBs to assess the attainable positioning accuracy, which shed light on the impact of network topology and sensor selection on localization accuracy. View full abstract»

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  • Region Incrementing Visual Cryptography

    Page(s): 659 - 662
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1033 KB) |  | HTML iconHTML  

    This letter presents a novel visual cryptography scheme, called region incrementing visual cryptography (RIVC), for sharing visual secrets with multiple secrecy levels in a single image. In the proposed n-level RIVC scheme, the content of an image S is designated to multiple regions associated with n secret levels, and encoded to n+1 shares with the following features: (a) each share cannot obtain any of the secrets in S, (b) any t (2lestlesn+1) shares can be used to reveal t-1 levels of secrets, (c) the number and locations of not-yet-revealed secrets are unknown to users, (d) all secrets in S can be disclosed when all of the n+1 shares are available, and (e) the secrets are recognized by visually inspecting correctly stacked shares without computation. The basis matrices for constructing the proposed n-level RIVC with small values of n=2, 3, 4 are introduced, and the results from two experiments are presented. View full abstract»

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  • Error Probability Bounds of Concatenated Channel Codes and Differential Space-Time Block Codes

    Page(s): 663 - 666
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (315 KB) |  | HTML iconHTML  

    In this letter, we analyze the performance of a class of multiple-antenna systems which concatenate channel codes, e.g., trellis coded modulation (TCM), and differential orthogonal space-time block codes (DOSTBC). Assuming no channel state information (CSI), tight performance bounds for bit and frame error rates are provided under block Rayleigh fading channel. Simulation results are also provided which confirm the accuracy of analytical findings. View full abstract»

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  • Soft-Output MMSE MIMO Detector Under ML Channel Estimation and Channel Correlation

    Page(s): 667 - 670
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (137 KB) |  | HTML iconHTML  

    As channel estimation errors are not taken into account by existing soft-output minimum mean square error (MMSE) multiple-input multiple-output (MIMO) detector, its performance can therefore be degraded under imperfect channel estimation. In this letter, we propose a novel soft-output MMSE MIMO detector under maximum likelihood (ML) channel estimation for a MIMO system with spatially correlated receiver and transmitter antennas. Our proposed detector takes both channel estimation errors and spatial correlation of antennas into account when constructing MMSE filter and computing log-likelihood ratio (LLR) of each coded bit. Simulation results show the proposed novel detector outperforms existing soft-output MMSE MIMO detector with considerable improvement. View full abstract»

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  • Sensing Performance of Energy Detector With Correlated Multiple Antennas

    Page(s): 671 - 674
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (182 KB) |  | HTML iconHTML  

    This paper describes the derivation of detection and false-alarm probabilities for energy detectors in cognitive radio networks when a sensing node of the secondary system has correlated multiple antennas. The sensing performance degradation due to the antenna correlation is then investigated based on the performance analysis. The conclusions of the analysis are verified by numerical simulation results. View full abstract»

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  • On the Impact of Bounded Rationality in Peer-to-Peer Networks

    Page(s): 675 - 678
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (262 KB) |  | HTML iconHTML  

    In this letter, we consider peer-to-peer (P2P) networks, where multiple peers are interested in sharing their content. In the considered P2P system, autonomous and self-interested peers use a Markov decision process (MDP) framework to determine their upload bandwidth allocations, which maximize their individual utilities. This framework enables the peers to make foresighted decisions on their bandwidth allocations, by considering the future impact of their decisions. In this letter, we focus on the impact of the peers' bounded rationality on their resource reciprocation strategies and ultimately, on their achievable utilities. Specifically, we consider peers who have only a limited ability to model the other peers' strategies for resource reciprocation, and study how this impacts their own decisions. View full abstract»

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  • Lagrangian Multiplier Based Joint Three-Layer Rate Control for H.264/AVC

    Page(s): 679 - 682
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (191 KB) |  | HTML iconHTML  

    Lagrangian multiplier (LM) based mode decision is one of the most important technologies in standard H.264/AVC encoder. Based on LM theory, this paper presents a joint three-layer (JTL) model for H.264/AVC rate control. At macroblock (MB) level, we dynamically revise LM for each of MBs by its estimated complexities, which is able to select a better coding mode than the current scheme with the constant LM adopted in H.264/AVC. At frame level, a more flexible and effective quantization parameter (QP) adjustment scheme is designed for I-frame to avoid buffer overflow or underflow. In addition, we also present a new target bits allocation scheme in group of picture (GOP) level. Experimental results show that our JTL model can not only significantly improve the video quality with the average PSNR gain up to 0.97 dB, but also provide a more stable buffer occupancy with respect to other existing rate control methods. View full abstract»

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  • Composite Common Spatial Pattern for Subject-to-Subject Transfer

    Page(s): 683 - 686
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (393 KB) |  | HTML iconHTML  

    Common spatial pattern (CSP) is a popular feature extraction method for electroencephalogram (EEG) classification. Most of existing CSP-based methods exploit covariance matrices on a subject-by-subject basis so that inter-subject information is neglected. In this paper we present modifications of CSP for subject-to-subject transfer, where we exploit a linear combination of covariance matrices of subjects in consideration. We develop two methods to determine a composite covariance matrix that is a weighted sum of covariance matrices involving subjects, leading to composite CSP. Numerical experiments on dataset IVa in BCI competition III confirm that our composite CSP methods improve classification performance over the standard CSP (on a subject-by-subject basis), especially in the case of subjects with fewer number of training samples. View full abstract»

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  • Automatic Robust Linear Receiver for Multi-Access Space-Time Block Coded MIMO Systems

    Page(s): 687 - 690
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (195 KB) |  | HTML iconHTML  

    In this letter, we develop a fully automatic robust linear receiver technique for joint space-time decoding and interference rejection in multi-access MIMO systems that use orthogonal space-time block codes and erroneous channel state information (CSI). The proposed receiver does not need any a priori knowledge of channel estimation errors and has a simple closed form. Numerical examples show that our method usually gives good performance in case of non-perfect CSI and/or low sample sizes when compared with other tested linear receivers. View full abstract»

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  • Stochastic Erasure-Only List Decoding Algorithms for Reed-Solomon Codes

    Page(s): 691 - 694
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (481 KB) |  | HTML iconHTML  

    We present a novel stochastic decoding algorithm for Reed-Solomon codes. We apply an iterative Monte Carlo based approach called the Cross-Entropy method to produce, in every iteration, a set of random error locator vectors, each indicates n-k possible erasure positions within a received word. We associate each error locator vector with a candidate codeword by erasures-only decoding the received word, using the error locator vector to locate the erasures. Each iteration results in a new elite set that contains the best E candidate codewords. To increase the search radius and enhance the decoder performance we use the randomly drawn samples to generate what we call virtual received words from which extra candidate codewords and thus candidate elite members can be obtained. The proposed algorithms offer both complexity and performance advantages over some existing algebraic decoding algorithms for high rate RS codes. View full abstract»

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  • Perceptually-Motivated All-Pole Modeling

    Page(s): 695 - 698
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (238 KB) |  | HTML iconHTML  

    A new speech analysis-synthesis approach that is based on a perceptually-motivated all-pole (PMAP) modeling is described. The main idea is to directly estimate the perceptually relevant pole locations using an auditory excitation pattern-matching method. The all-pole model is synthesized using the perceptual poles and produces improved spectral fitting. We show that the prediction residual obtained from the PMAP analysis has lower perceptual loudness relative to that of the conventional LP. View full abstract»

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  • A General Parameterization Quantifying Performance in Energy Detection

    Page(s): 699 - 702
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (285 KB) |  | HTML iconHTML  

    This letter presents a new look at the problem of energy detection with and without diversity schemes. The impact of channel fading and/or diversity scheme on the probability of missing detection is quantified and then the definition, sensing gain, is proposed based on the analytical result. The sensing gain proposed in this letter determines the slope of the probability of missing detection versus average signal-to-noise ratio (SNR) curve, at high SNR, in a log-log scale. Our result shows that the sensing gain just has a relationship with the type of channel fading and/or diversity scheme and is totally irrelevant with the false alarm probability which is preset. View full abstract»

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  • On Designing Sequences With Impulse-Like Periodic Correlation

    Page(s): 703 - 706
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (163 KB) |  | HTML iconHTML  

    Sequences with impulse-like correlations are at the core of several radar and communication applications. Two criteria that can be used to design such sequences, and which lead to rather different results in the aperiodic correlation case, are shown to be identical in the periodic case. Furthermore, two simplified versions of these two criteria, which similarly yield completely different sequences in the aperiodic case, are also shown to be equivalent. A corollary of these unexpected equivalences is that the periodic correlations of an arbitrary sequence must satisfy an intriguing identity, which is also presented in this letter. View full abstract»

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  • GLRT Versus MFLRT for Adaptive CFAR Radar Detection With Conic Uncertainty

    Page(s): 707 - 710
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (170 KB) |  | HTML iconHTML  

    In this paper, we consider the problem of detecting an unknown signal, belonging to a conic region, in the presence of complex Gaussian disturbance. We assume that the cone aperture parameter, which ranges in a pre-assigned interval, is unknown. Hence, we devise two decision rules which are respectively based on the Generalized Likelihood Ratio Test (GLRT) and on the Multifamily Likelihood Ratio Test (MFLRT). Both the receivers ensure the Constant False Alarm Rate (CFAR). At the analysis stage, we compare the performance of the two decision strategies in correspondence of different parameters for the useful signal component. View full abstract»

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  • Shape Orientation Pattern

    Page(s): 711 - 714
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (324 KB) |  | HTML iconHTML  

    Due to the variety of shapes as well as the diversity of applications there does not exist any single method for computing the shape orientation of all shapes. In this paper, we introduce a new shape orientation measure, shape orientation pattern, to find the crisp and fuzzy shape orientation as well as shape orientability from any shape. We also illustrate that the new shape orientation measure can be used as a RST invariant shape descriptor. View full abstract»

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  • Efficient Detection Ordering Scheme for MIMO Transmission Using Power Control

    Page(s): 715 - 718
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (191 KB) |  | HTML iconHTML  

    In this letter, an efficient ordering scheme for an ordered successive interference cancellation detector is determined under the bit error rate minimization criterion for multiple antenna systems using transmission power control. From the convexity of the Q -function, we derive the ordering strategy that makes the channel gains converge to their geometric mean. Based on this approach, the fixed ordering algorithm is first designed, for which the geometric mean is used for a constant threshold. To further improve the performance, the modified scheme employing adaptive thresholds is developed using the correlation among ordering results. Theoretical analysis and simulation results show that proposed ordering schemes using QR-decomposition not only require a reduced computational complexity compared to the conventional scheme, but result in improved error performance. View full abstract»

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  • Improvement on the Channel Estimation of Pilot Cyclic Prefixed Single Carrier (PCP-SC) System

    Page(s): 719 - 722
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (540 KB) |  | HTML iconHTML  

    The pilot cyclic prefixed single carrier (PCP-SC) system has the ability to achieve channel estimation in a fast-fading environment. It also enables symbol recovery even when the frequency domain of the channel has nulls. This letter proposes a simple but effective way of improving the performance of channel estimation. Regardless of the signal-to-noise ratio (SNR) and the pilot type, the receiver can achieve about a 1.72 dB performance gain for the mean squared error (MSE) of channel estimation if it implements the proposed method with slightly additional computational complexity. The proposed method can also be utilized in any type of pilot in PCP-SC and MIMO systems. View full abstract»

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  • Cyclic Spectral Analysis of UWB-IR Signals

    Page(s): 723 - 726
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (229 KB) |  | HTML iconHTML  

    A unified, matrix-based, stochastic method for cyclic spectral analysis of ultra-wideband impulse radio signals, based on their Markov chain representation, is proposed. Explicit expressions are obtained for the cyclic spectrum of pulse position modulation and pulse amplitude modulation with time-hopping and direct sequence coding, respectively. Some theoretical and graphed results for the spectral correlation characterization of these signals are presented, as well. View full abstract»

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  • Exact Relation Between Continuous and Discrete Linear Canonical Transforms

    Page(s): 727 - 730
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (116 KB) |  | HTML iconHTML  

    Linear canonical transforms (LCTs) are a family of integral transforms with wide application in optical, acoustical, electromagnetic, and other wave propagation problems. The Fourier and fractional Fourier transforms are special cases of LCTs. We present the exact relation between continuous and discrete LCTs (which generalizes the corresponding relation for Fourier transforms), and also express it in terms of a new definition of the discrete LCT (DLCT), which is independent of the sampling interval. This provides the foundation for approximately computing the samples of the LCT of a continuous signal with the DLCT. The DLCT in this letter is analogous to the DFT and approximates the continuous LCT in the same sense that the DFT approximates the continuous Fourier transform. We also define the bicanonical width product which is a generalization of the time-bandwidth product. View full abstract»

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The IEEE Signal Processing Letters is a monthly, archival publication designed to provide rapid dissemination of original, cutting-edge ideas and timely, significant contributions in signal, image, speech, language and audio processing.

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Editor-in-Chief
Peter Willett
University of Connecticut
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peter.willett@uconn.edu