Showing papers in "IEEE Signal Processing Magazine in 2007"

Compressive Sensing [Lecture Notes]

Abstract: This lecture note presents a new method to capture and represent compressible signals at a rate significantly below the Nyquist rate. This method, called compressive sensing, employs nonadaptive linear projections that preserve the structure of the signal; the signal is then reconstructed from these projections using an optimization process.

A Survey of Dynamic Spectrum Access

Abstract: Compounding the confusion is the use of the broad term cognitive radio as a synonym for dynamic spectrum access. As an initial attempt at unifying the terminology, the taxonomy of dynamic spectrum access is provided. In this article, an overview of challenges and recent developments in both technological and regulatory aspects of opportunistic spectrum access (OSA). The three basic components of OSA are discussed. Spectrum opportunity identification is crucial to OSA in order to achieve nonintrusive communication. The basic functions of the opportunity identification module are identified

MIMO Radar with Colocated Antennas

Abstract: We have provided a review of some recent results on the emerging technology of MIMO radar with colocated antennas. We have shown that the waveform diversity offered by such a MIMO radar system enables significant superiority over its phased-array counterpart, including much improved parameter identifiability, direct applicability of adaptive techniques for parameter estimation, as well as superior flexibility of transmit beampattern designs. We hope that this overview of our recent results on the MIMO radar, along with the related results obtained by our colleagues, will stimulate the interest deserved by this topic in both academia and government agencies as well as industry.

Shifting the MIMO Paradigm

Abstract: Multi-user MIMO (MU-MIMO) networks reveal the unique opportunities arising from a joint optimization of antenna combining techniques with resource allocation protocols. Furthermore, it brings robustness with respect to multipath richness, allowing for compact antenna spacing at the BS and, crucially, yielding the diversity and multiplexing gains without the need for multiple antenna user terminals. To realize these gains, however, the BS should be informed with the user's channel coefficients, which may limit practical application to TDD or low-mobility settings. To circumvent this problem and reduce feedback load, combining MU-MIMO with opportunistic scheduling seems a promising direction. The success for this type of scheduler is strongly traffic and QoS-dependent, however.

Cooperative Communications in Resource-Constrained Wireless Networks

Abstract: Cooperative communications have been proposed to exploit the spatial diversity gains inherent in multiuser wireless systems without the need of multiple antennas at each node. This is achieved by having the users relay each others messages and thus forming multiple transmission paths to the destination. In resource constrained networks, such as wireless sensor networks, the advantages of cooperation can be further exploited by optimally allocating the energy and bandwidth resources among users based on the available channel state information (CSI) at each node. In the first part of this article, we provide a tutorial survey on various power allocation strategies for cooperative networks based on different cooperation strategies, optimizing criteria, and CSI assumptions. In the second part, we identify the similarities between cooperative networks and several sensor network applications that utilize collaboration among distributed sensors to achieve the system goal. These applications include decentralized detection/estimation and data gathering. The techniques developed in cooperative communications can be used to solve many sensor network problems

MIMO Wireless Linear Precoding

Abstract: This article provides a tutorial of linear precoding for a frequency- flat, single-user MIMO wireless system, examining both theoretical foundations and practical issues The article first discusses principles for CSIT (channel-side information at the transmitter) acquisition and develops a dynamic CSIT model, which spans perfectly to statistical CSIT, taking into account channel temporal variation It then presents the capacity benefits of CSIT and information theoretic arguments for exploiting the CSIT by linear precoding A precoded system structure is then described, involving an encoder and a linear precoder Criteria for designing the precoder are then discussed, followed by specific designs for different CSIT scenarios

Life Beyond Bases: The Advent of Frames (Part II)

Abstract: Coming to the end of Part 1, we hope you have a different picture of a frame in your mind from a "picture frame." While necessarily colored by our personal bias, we intended this tutorial as a basic introduction to frames, geared primarily toward engineering students and those without extensive mathematical training. Frames are here to stay; as wavelet bases before them, they are becoming a standard tool in the signal processing toolbox, spurred by a host of recent applications requiring some level of redundancy.

Multiview Imaging and 3DTV

Abstract: The eight articles in this special section are devoted to multi-view imaging and three dimensional television displays.

Energy-Efficient Resource Allocation in Wireless Networks

Abstract: This paper shows that game theory can be used as a unifying framework to study radio resource management in a variety of wireless networks with different service criteria It focuses on infrastructure networks where users transmit to a common concentration point such as a base station in a cellular network or an access point Since most of the terminals in a wireless network are battery-powered, energy efficiency is crucial to prolonging the life of the terminals Also, in most practical scenarios, distributed algorithms are preferred over centralized ones Throughout this article it focuses on distributed algorithms with emphasis on energy efficiency A family of power control games is presented for energy-efficient resource allocation in wireless code-division multiple-access (CDMA) networks and give discussions and conclusions

Network Coding for the Internet and Wireless Networks

Abstract: In today's practical communication networks such as the Internet, information delivery is performed by routing. A promising generalization of routing is network coding. The potential advantages of network coding over routing include resource (e.g., bandwidth and power) efficiency, computational efficiency, and robustness to network dynamics. This tutorial article provides an overview of the theory, practice, and applications of network coding.

Wireless Sensors in Distributed Detection Applications

Abstract: Detection problems provide a productive starting point for the study of more general statistical inference problems in sensor networks. In this article, the classical framework for decentralized detection is reviewed and argued that, while this framework provides a useful basis for developing a theory for detection in sensor networks, it has serious limitations. The classical framework does not adequately take into account important features of sensor technology and of the communication link between the sensors and the fusion center. An alternative framework for detection in sensor networks that has emerged over the last few years is discussed. Several design and optimization strategies may be gleaned from this new framework

Bootstrap for Empirical Multifractal Analysis

Abstract: Multifractal analysis is becoming a standard statistical analysis technique. In signal processing, it mostly consists of estimating scaling exponents characterizing scale invariance properties. For practical purposes, confidence intervals in estimation and p values in hypothesis testing are of primary importance. In empirical multifractal analysis, the statistical performance of estimation or test procedures remain beyond analytical derivation because of the theoretically involved nature of multifractal processes. Therefore, the goal of this article is to show how non-parametric bootstrap approaches circumvent such limitations and yield procedures that exhibit satisfactory statistical performance and can hence be practically used on real-life data. Such tools are illustrated at work on the analysis of the multifractal properties of empirical hydrodynamic turbulence data.

Fast, Accurate Frequency Estimators [DSP Tips & Tricks]

Abstract: This article presents computationally simple algorithms that provide substantial refinement of the frequency estimation of tones based on DFT samples without the need for increasing the DFT size. When estimating the frequency of a tone, the idea is to estimate the frequency of the spectral peak based on three DFT samples is discussed

Image-Based Rendering and Synthesis

Abstract: One of the most important applications in multiview imaging (MVI) is the development of advanced immersive viewing or visualization systems using, for instance, 3DTV. With the introduction of multiview TVs, it is expected that a new age of 3DTV systems will arrive in the near future. Image-based rendering (IBR) refers to a collection of techniques and representations that allow 3-D scenes and objects to be visualized in a realistic way without full 3-D model reconstruction. IBR uses images as the primary substrate. The potential for photorealistic visualization has tremendous appeal, and it has been receiving increasing attention over the years. Applications such as video games, virtual travel, and E-commerce stand to benefit from this technology. This article serves as a tutorial introduction and brief review of this important technology. First the classification, principles, and key research issues of IBR are discussed. Then, an object-based IBR system to illustrate the techniques involved and its potential application in view synthesis and processing are explained. Stereo matching, which is an important technique for depth estimation and view synthesis, is briefly explained and some of the top-ranked methods are highlighted. Finally, the challenging problem of interactive IBR is explained. Possible solutions and some state-of-the-art systems are also reviewed.

Multitarget Tracking in Distributed Sensor Networks

Abstract: In this article, a survey of techniques for tracking multiple targets in distributed sensor networks is provided and introduce some recent developments. The single target tracking in distributed sensor networks is reviewed. The tracking and resource management issues can be readily extended to MTT. The MTT problem is also briefly reviewed and describe the traditional approaches in centralized systems. Then focus on MTT in resource-constrained sensor networks and present two distinct example methods demonstrating how limited resources can be utilized in MTT applications. Finally, the most important remaining problems are discussed and suggest future directions

Bio-Inspired Sensor Network Design

Abstract: The goal of this article is to show how a simple self-synchronization mechanism, borrowed from biological systems, can form the basic tool for achieving globally optimal distributed decisions in a wireless sensor network with no need for a fusion center. After describing the basic interaction mechanism among the network nodes, the conditions are illustrated guaranteeing the convergence of each node to a global (or local) consensus coinciding with the globally (locally) optimal decision statistics. The interaction mechanism takes into account the physical channel parameters, such as fading coefficients and propagation delays. Then the results are illustrated through examples of distributed estimation and multiple hypothesis testing. The energy consumption issues are addressed and discuss some possible implementations

Distributed Monoview and Multiview Video Coding

Abstract: Growing percentage of the world population now uses image and video coding technologies on a regular basis. These technologies are behind the success and quick deployment of services and products such as digital pictures, digital television, DVDs, and Internet video communications. Today's digital video coding paradigm represented by the ITU-T and MPEG standards mainly relies on a hybrid of block- based transform and interframe predictive coding approaches. In this coding framework, the encoder architecture has the task to exploit both the temporal and spatial redundancies present in the video sequence, which is a rather complex exercise. As a consequence, all standard video encoders have a much higher computational complexity than the decoder (typically five to ten times more complex), mainly due to the temporal correlation exploitation tools, notably the motion estimation process. This type of architecture is well-suited for applications where the video is encoded once and decoded many times, i.e., one-to-many topologies, such as broadcasting or video-on-demand, where the cost of the decoder is more critical than the cost of the encoder.

Bootstrap - Inspired Techniques in Computation Intelligence

Abstract: This article is about the success story of a seemingly simple yet extremely powerful approach that has recently reached a celebrity status in statistical and engineering sciences. The hero of this story - bootstrap resampling - is relatively young, but the story itself is a familiar one within the scientific community: a mathematician or a statistician conceives and formulates a theory that is first developed by fellow mathematicians and then brought to fame by other professionals, typically engineers, who point to many applications that can benefit from just such an approach. Signal processing boasts some of the finest examples of such stories, such as the classic story of Fourier transforms or the more contemporary tale of wavelet transforms.

3-D Displays and Signal Processing

Abstract: In this article, main electronic 3-D display technologies from a signal processing perspective are overviewed. And the underlying physics, benefits, deficiencies of various displays are described. The general role of signal processing and provide specific examples of signal processing helping address certain display deficiencies are discussed. Challenges awaiting signal processing in quest of the ultimate 3-D experience is highlighted.

Multiview Video Compression

Abstract: Due to the vast raw bit rate of multiview video, efficient compression techniques are essential for 3D scene communication. As the video data originate from the same scene, the inherent similarities of the multiview imagery are exploited for efficient compression. These similarities can be classified into two types, inter-view similarity between adjacent camera views and temporal similarity between temporally successive images of each video.

Social Signal Processing [Exploratory DSP]

Abstract: Face-to-face communication conveys social context as well as words. It is this social signaling that allows new information to be smoothly integrated into a shared, group-wide understanding. Social signaling includes signals of interest, determination, friendliness, boredom, and other "attitudes" toward a social situation. Psychologists speculate that social signaling may have evolved as a way to establish hierarchy and group cohesion because social signaling functions as a subconscious discussion about relationships, resources, risks, and rewards. In many situations the nonlinguistic signals that serve as the basis for this social discussion are just as important as conscious content for determining human behavior. In what follows we discuss challenges in exploratory processing of social signals and tools that allow us to predict human behavior and sometimes exceed even expert human capabilities. These tools potentially permit computer and communications systems to support social and organizational roles instead of viewing the individual as an isolated entity. Example applications include automatically patching people into socially important conversations, instigating conversations among people in order to build a more solid social network, and reinforcing family ties.

Corpus-Based Concatenative Synthesis

Abstract: Corpus-based concatenative methods for musical sound synthesis have attracted much attention recently. They make use of a variety of sound snippets in a database to assemble a desired sound or phrase according to a target specification given in sound descriptors or by an example sound. With ever-larger sound databases easily available, together with a pertinent description of their contents, they are increasingly used for composition, high-level instrument synthesis, and interactive exploration of a sound corpus. This article gives an overview of the components needed for corpus-based concatenative synthesis and details of some realizations. Signal processing methods are crucial for all parts of analysis, (segmentation; and descriptor analysis), for synthesis, and can intervene in the selection part, e.g., for spectral matching

Bootstrap Particle Filtering

Abstract: This article provides an overview of nonlinear statistical signal processing based on the Bayesian paradigm. The next-generation processors are well founded on MC simulation-based sampling techniques. The development of the sequential Bayesian processor is reviewed using the state-space models. The popular bootstrap algorithm was outlined and applied to an ocean acoustic synthetic aperture towed array target tracking problem to test the performance of a particle filtering technique.

Bootstrap Methods and Applications

Abstract: Given the wealth of literature on the topic supported by solutions to practical problems, we would expect the bootstrap to be an off-the-shelf tool for signal processing problems as are maximum likelihood and least-squares methods. This is not the case, and we wonder why a signal processing practitioner would not resort to the bootstrap for inferential problems. We may attribute the situation to some confusion when the engineer attempts to discover the bootstrap paradigm in an overwhelming body of statistical literature. Our aim is to give a short tutorial of bootstrap methods supported by real-life applications. This pragmatic approach is to serve as a practical guide rather than a comprehensive treatment, which can be found elsewhere. However, for the bootstrap to be successful, we need to identify which resampling scheme is most appropriate.

Synthesis of the Singing Voice by Performance Sampling and Spectral Models

Abstract: This paper introduces the concept of synthesis based on performance sampling. It explains that although sampling has been considered a way to capture and reproduce the sound of an instrument, it should be better considered a way to model the sonic space produced by a performer with an instrument. The paper presents a singing voice synthesizer, pointing out the main issues and complexities emerging along its design. Although the current system is able to generate convincing results in certain situations, there is still much room for improvements, especially in the areas of expression, spectral modeling and sonic space design. However, computer singing is definitely coming close to becoming indistinguishable from human performances

Acoustic Modeling Using the Digital Waveguide Mesh

Abstract: The digital waveguide mesh has been an active area of music acoustics research for over ten years. Although founded in 1-D digital waveguide modeling, the principles on which it is based are not new to researchers grounded in numerical simulation, FDTD methods, electromagnetic simulation, etc. This article has attempted to provide a considerable review of how the DWM has been applied to acoustic modeling and sound synthesis problems, including new 2-D object synthesis and an overview of recent research activities in articulatory vocal tract modeling, RIR synthesis, and reverberation simulation. The extensive, although not by any means exhaustive, list of references indicates that though the DWM may have parallels in other disciplines, it still offers something new in the field of acoustic simulation and sound synthesis

The H.264/AVC Video Coding Standard [Standards in a Nutshell]

Abstract: This article provides a description of the structure, technology, performance, and resources of H.264/AVC, which is referred to formally as ITU-T Recommendation H.264 and ISO/IEC 14496-10 (MPEG-4 Part 10)

Multidimensional Signal, Image and Video Processing and Coding [Book Reviews]

Abstract: This new book covers the processing and coding of multidimensional signals, in particular, still images and video. The book is accompanied by a CD-ROM and a companion Web site. The book is well designed and its material is timely. The only drawback is its lack of depth in covering color. The book would work with an introductory graduate course on still-image processing and compression or for an advanced graduate course on video processing and compression. The fact that the book takes a signal processing, rather than computer vision, viewpoint to image manipulation will make it a valuable resource for both researchers and students alike.

Jackknifing Multitaper Spectrum Estimates

Abstract: This article discusses some examples of jackknifing multitaper estimates of spectra, coherences, and frequency estimates. Examples include barometric pressure data, where spectrum with an extremely large range plus many narrow-band processes are seen. Analysis of dropped-call rates in cellular phone systems and their coherence with solar radio data illustrates further uses of the jackknife and some of the complexities encountered in processes with many spectral lines. The third example is a reexamination of the 663-year record of Nile River levels, a process claimed to be long-memory. There are persistent terms, but not of the form usually classed as long-memory. We begin by explaining the terms in the title.

The Mobile Broadband WiMAX Standard [Standards in a Nutshell]

Abstract: Mobile worldwide interoperability for microwave access (WiMAX) is a wireless standard that introduces orthogonal frequency division multiple access (OFDMA) and other key features to enable mobile broadband services at a vehicular speed of up to 120 km/h. WiMAX complements the and competes with wireless local area networks (WLANs) and the third generation (3G) wireless standards on coverage and data rate. More specifically, WiMAX supports a much larger coverage area than WLAN, does not require line of sight for a connection, and is significantly less costly compared to the current 3G cellular standards. Although the WiMAX standard supports both fixed and mobile broadband data services, the latter have a much larger market. Therefore, this article will briefly present the Mobile WiMAX standard, the technologies deployed for the air interface and the network, and the development of the standards to support mobile multihop relays in a WiMAX network.