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Signal Processing Magazine, IEEE

Issue 5 • Date Sept. 2004

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Displaying Results 1 - 25 of 29
  • From frequency to quefrency: a history of the cepstrum

    Page(s): 95 - 106
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    The idea of the log spectrum or cepstral averaging has been useful in many applications such as audio processing, speech processing, speech recognition, and echo detection for the estimation and compensation of convolutional distortions. To suggest what prompted the invention of the term cepstrum, this article narrates the historical and mathematical background that led to its discovery. The computations of earlier simple echo representations have shown that the spectrum representation domain results does not belong in the frequency or time domain. Bogert et al. (1963) chose to refer to it as quefrency domain and later termed the spectrum of the log of a time waveform as the cepstrum. The article also recounts the analysis of Al Oppenheim in relation to the cepstrum. It was in his theory for nonlinear signal processing, referred to as homomorphic systems, that the realization of the characteristic system of homomorphic convolution was reminiscent of the cepstrum. To retain both the relationship to the work of Bogart et al. and the distinction, the term power cepstrum was eventually applied to the nonlinear mapping in homomorphic deconvolution . While most of the terms in the glossary have faded into the background, the term cepstrum has survived and has become part of the digital signal processing lexicon. View full abstract»

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  • Dates ahead

    Page(s): 118
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (188 KB)  

    First Page of the Article
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  • Designing a mobile broadband wireless access network

    Page(s): 20 - 28
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (799 KB) |  | HTML iconHTML  

    In this paper, a new OFDM-based air interface technology for a mobile broadband wireless system is described. The technology leverages the standard Internet protocol (IP) network elements to build the system and deploys a new air interface technology based on OFDMA. Cross-layer optimization played a major role in the design where the choices made in the physical, MAC, and link layers are also driven by the goal of extending the Internet to the wireless space. A major physical layer benefit of this air interface comes from the orthogonality property that the results in the elimination of in-cell interference are averaged and a worst-case interferer does not limit the system performance. The physical layer features not only result in high capacity but also provide very fine granularity of allocating air link resources, which improves the MAC and link-layer efficiency. The MAC and link layer provide contention-free, fast control channels between the RAR and the WTs. These channels are used to ferry a variety of signaling such as assignments of traffic channel, acknowledgements, channel quality, and traffic request reports. This holistic approach allows for a scheduler that could not only achieve high spectral efficiency but also allow for a fine control over QoS attributes such as latency, reliability, and service differentiation. View full abstract»

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  • DNA computing from a signal processing viewpoint

    Page(s): 100 - 106
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    In this article, an analysis of Adleman's experiment and a review of DNA computing applications from a signal-processing point of view are provided. In addition, certain key parts of DNA computing are emphasized, such as the code word design, to which the application of signal processing theory and techniques can offer significant advantages. The goal of this article is to introduce to the signal processing community a new unexplored area of research. View full abstract»

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  • Signal processing in random access

    Page(s): 29 - 39
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    In this paper, a cross-layer view for roles of signal processing in random access network and vice versa is presented. The two cases where cross-layer design has a quantifiable impact on system performance are discussed. The first case is a small network (such as wireless LAN) where a few nodes with bursty arrivals communicate with an access point. The design objective is to achieve the highest throughput among users with variable rate and delay constraints. The impact of PHY layer design on MAC protocol is examined and illustrates a tradeoff between allocating resources to the PHY layer and to MAC layer. The second case, in contrast, deals with large-scale sensor networks where each node carries little information but is severely constrained by its computation and communication complexity and most importantly, battery power. This paper emphasizes that the design of signal processing algorithms must take into account the role of MAC and the nature of random arrivals and bursty transmissions. View full abstract»

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  • Medium access control - physical cross-layer design

    Page(s): 40 - 50
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    This article reviewed the various aspects of MAC-PHY cross-layer designs, with the goals of introducing pertinent queuing and stability analysis tools to the SP-oriented readership, and illustrating the advantages of such cross-layer designs using the recently introduced class of xNDMA protocols as an example. The results of queuing analysis show that a jointly designed MAC-PHY layer provides increased throughput and low delay characteristics over a wide range of offered loads. The throughput-delay benefits of xNDMA come at the expense of a moderate increase in receiver complexity and power consumption. View full abstract»

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  • Call admission control in wireless multimedia networks

    Page(s): 51 - 58
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    Call admission control (CAC) is a mechanism used in networks to administer quality of service (QoS). Whereas the CAC problem in time-division multiple access (TDMA)-based cellular networks is simply related to the number of physical channels available in the network, it is strongly related to the physical layer performance in code-division multiple access (CDMA) networks since the multi-access interference in them is a function of the number of users and is a limiting factor in ensuring QoS. In this article, the CAC issues in multimedia DS-CDMA systems are reviewed by illustrating the basic principles underlying various schemes that have been proposed progressively from the simplest to the complex. The article also introduces SIR as a measure of QoS and describes the relatively simple schemes to administer CAC. The expression for SIR resulting from linear minimum mean-squared error processing is also presented. This article illustrates how CAC for multiple class service can be casted into an optimality framework and then discuss the recent work addressing self-similar multiple access interference. View full abstract»

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  • Sharing knowledge and building communities in signal processing

    Page(s): 10 - 16
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (424 KB) |  | HTML iconHTML  

    There is a great need for information technologies for developing and delivering quality, up-to-date educational materials that convey to all learners that knowledge is a dynamic continuum that stretches across disciplines. To address this need, an experimental, open-source/open-content initiative, called the Connexions Project, was initiated. The Connexions Project offers an alternative to the way textbooks and other learning materials are created, maintained, and used. By design, Connexions greatly impacts current modes of teaching and learning, and the development and sharing of knowledge. In combination with powerful software tools which consist of an XML language, Connexions gives learner free access to educational materials that can be readily manipulated to suit their individual learning styles as they explore links among concepts. The free software tools also foster the development, manipulation, and continuous refinement of educational material by diverse communities of authors and instructor. An overview of the philosophy and progress of the project is presented, with a particular emphasis on its application to the area of signal processing. View full abstract»

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  • New products

    Page(s): 114 - 117
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    First Page of the Article
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  • Advertisers index

    Page(s): 120
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  • Direct digital synthesis: a tool for periodic wave generation (part 2)

    Page(s): 110 - 112
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    Direct digital synthesis (DDS) is a useful tool for generating periodic waveforms. In this two-part article, the basic idea of this synthesis technique is presented and then focused on the quality of the sinewave a DDS can create, introducing the SFDR quality parameter. Next effective methods to increase the SFDR are presented through sinewave approximations, hardware schemes such as dithering and noise shaping, and an extensive list of reference. When the desired output is a digital signal, the signal's characteristics can be accurately predicted using the formulas given in this article. When the desired output is an analog signal, the reader should keep in mind that the performance of the DDS is eventually limited by the performance of the digital-to-analog converter and the follow-on analog filter. Hoping that this article would incite engineers to use DDS either in integrated circuits DDS or software-implemented DDS. From the author's experience, this technique has proven valuable when frequency resolution is the challenge, particularly when using low-cost microcontrollers. View full abstract»

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  • Distributed source coding for sensor networks

    Page(s): 80 - 94
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    In recent years, sensor research has been undergoing a quiet revolution, promising to have a significant impact throughout society that could quite possibly dwarf previous milestones in the information revolution. Realizing the great promise of sensor networks requires more than a mere advance in individual technologies. It relies on many components working together in an efficient, unattended, comprehensible, and trustworthy manner. One of the enabling technologies in sensor networks is the distributed source coding (DSC), which refers to the compression of the multiple correlated sensor outputs that does not communicate with each other. DSC allows a many-to-one video coding paradigm that effectively swaps encoder-decoder complexity with respect to conventional video coding, thereby representing a fundamental concept shift in video processing. This article has presented an intensive discussion on two DSC techniques, namely Slepian-Wolf coding and Wyner-Ziv coding. The Slepian and Wolf coding have theoretically shown that separate encoding is as efficient as joint coding for lossless compression in channel coding. View full abstract»

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  • Signal processing challenges in active queue management

    Page(s): 69 - 79
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    The publication of Floyd and Jacobson's seminal paper "Random early detection gateways for congestion avoidance" (1993), marked a new direction in networking research and began what is perhaps the most investigated example of cross-layer optimization. While this paper has inspired an immense amount of work in research, many open problems in active queue management (AQM) still remain. This article seeks to frame these problems in terms accessible to the signal processing researchers. The basic idea of AQM has been provided as well as its objective and overviews of a sample of different approaches. The signal processing aspects of the AQM are discussed, specifically the problem of predicting congestion, approaches to detecting changes in network traffic, an estimation problem, dithering, and quantization. View full abstract»

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  • Cross-layer wireless resource allocation

    Page(s): 59 - 68
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    A fundamental problem in networking is the allocation of limited resources among the users of the network. In a traditional layered network architecture, the resource to be allocated at the medium access control (MAC) and network layers utilizes communication links, viewed as "bit pipes" that deliver data at a fixed rate with occasional random errors. Though this separation has many advantages, there is a growing awareness that this simple bit-pipe view is inadequate, particularly in the context of modern wireless data networks. In this article, several basic cross-layer resource allocation problems for wireless fading channels are considered. The article focuses on the characterization of fundamental performance limits while taking into account both network layer QoS and physical layer performance. View full abstract»

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  • IEEE Signal Processing

    Page(s): 0_1
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    Freely Available from IEEE
  • Table of contents

    Page(s): 1
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    Freely Available from IEEE
  • ICME 2005

    Page(s): 15
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    Freely Available from IEEE
  • Your foundation for technical innovation [advertisement]

    Page(s): 17
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    Freely Available from IEEE
  • ICASSP 2005 Philadelphia

    Page(s): 107
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    Freely Available from IEEE
  • Conference spotlight - ICIP'04 in the lion city-Singapore

    Page(s): 108 - 109
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    Freely Available from IEEE

Aims & Scope

IEEE Signal Processing Magazine publishes tutorial-style articles on signal processing research and applications, as well as columns and forums on issues of interest.

Full Aims & Scope

Meet Our Editors

Editor-in-Chief
Min Wu
University of Maryland, College Park
United States 

http://www/ece.umd.edu/~minwu/