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Signals, Systems and Computers, 2004. Conference Record of the Thirty-Eighth Asilomar Conference on

Date 7-10 Nov. 2004

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  • Conference Record Thirty-Eighth Asilomar Conference on Signals, Systems and Computers 2004

    Page(s): 0_1
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  • Conference Record of The Thirty-Eighth Asilomar Conference on Signals, Systems and Computers - Title

    Page(s): i
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  • [Breaker page]

    Page(s): ii
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  • Conference Record of The Thirty-Eighth Asilomar Conference on Signals, Systems and Computers - Title2

    Page(s): iii
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  • Copyright

    Page(s): iv
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  • Table of contents

    Page(s): v - xxvii
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  • Student Paper Contest

    Page(s): xxviii
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  • Foreword

    Page(s): xxix
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  • [Breaker page]

    Page(s): xxx
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  • Session TP1 Sensor Array and Relay Networks

    Page(s): 1295 - 1296
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  • Group testing for sensor networks: the value of asking the right questions

    Page(s): 1297 - 1301 Vol.2
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (568 KB) |  | HTML iconHTML  

    Sharing of information is crucial in sensor networks to allow collective processing of observations made by distributed sensors. Our goal is to efficiently retrieve the distributed sensor measurements at a central processor or to share the information among all sensors. To achieve this goal with a minimum number of channel accesses, it naturally involves the compression of the distributed source data and an optimal scheduling of the transmissions to reduce the number of redundant transmissions. In this paper, we utilize a content-based group testing approach to derive a joint source coding and multiple access scheduling method without the initial knowledge of the statistics of the sensor field. The group testing multiple access (GTMA) scheme proposed in this paper is obtained by choosing groups through a tree splitting algorithm that adapts the branching of the tree according to the progressively estimated statistics of the sensor field. We show that this method overcomes the difficulty of applying the algebraic distributed source coding schemes to a large number of sensors and for arbitrary or unknown statistics of the sensor field. View full abstract»

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  • Networking by parallel relays: diversity, lifetime and routing overhead

    Page(s): 1302 - 1306 Vol.2
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (606 KB) |  | HTML iconHTML  

    For several decades, research activities in mobile ad hoc networking have predominantly relied on the notion of serial relays where a data packet hops from one node to another in a serial fashion. Recent research activities in signal processing and information theory suggest that parallel relays have a greater potential than serial relays. In this paper, a significant diversity gain of using parallel relays over serial relays is highlighted, the lifetimes of a single-path route of parallel relays and multi-path routes of serial relays are compared, and the routing overheads for each type of routes are also investigated. This study strongly supports that parallel relays have great advantages over serial relays in dense and mobile ad hoc networks. View full abstract»

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  • Cooperative diversity for wireless fading channels without channel state information

    Page(s): 1307 - 1312 Vol.2
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (635 KB) |  | HTML iconHTML  

    Relaying and cooperative diversity allow multiple wireless radios to effectively share their antennas and create a virtual antenna array, thereby leveraging the spatial diversity benefits of multiple-input, multiple-output (MIMO) antenna systems. This paper examines the benefits of cooperative diversity for scenarios in which the receivers cannot exploit accurate channel state information (CSI). In particular, noncoherent demodulation is explored for two classes of relay processing, namely, detect-and-forward and amplify-and-forward. A complete maximum likelihood (ML) framework for noncoherent demodulation is developed for detect-and-forward, and is shown to naturally extend the corresponding framework for coherent demodulation. By contrast, the intractability of ML demodulation for noncoherent amplify-and-forward is demonstrated, suggesting a disconnect from the well-developed framework for coherent demodulation. Simulation results exhibit the diversity benefits of the detect-and-forward algorithms. View full abstract»

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  • Distributed space-time processing in sensor networks

    Page(s): 1313 - 1317 Vol.2
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (546 KB) |  | HTML iconHTML  

    Given the power limitations of sensor networks, it is of interest to determine cooperative communication schemes for such networks which can exploit the inherent spatial diversity of nodes. This paper proposes a simple scheme based on maximal ratio combining and a distributed transmission protocol to effectively exploit temporal and spatial diversity in a sensor network. In contrast to cooperative communication schemes based on distributed space-time codes, the proposed distributed space-time processing (DSTP) method exploits diversity in a greedy manner and does not require the overhead of setting up clusters. DSTP is a suite of cross-layer (physical, media access control and network) distributed protocols designed for ease of implementation, robustness and scalability in large sensor networks. Two modes of DSTP are proposed to allow one-to-one or many-to-one distributed communication. The efficacy of the proposed scheme is evaluated by a diversity analysis as well as simulation results. The frame-error rate performance of DSTP is observed to be superior to simple relaying and a cluster-based distributed space-time method. View full abstract»

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  • On the capacity of broadband relay networks

    Page(s): 1318 - 1322 Vol.2
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (615 KB) |  | HTML iconHTML  

    This paper studies a broadband relay network model with multiple source nodes, multiple relay nodes and a single destination node. The capacities using different multiple access schemes (joint coding/decoding and OFDMA) under two relay schemes are derived, respectively. Numerical results are evaluated to compare the two multiple access schemes. View full abstract»

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  • Localization and tracking of multiple near-field sources using randomly distributed sensors

    Page(s): 1323 - 1327 Vol.2
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (632 KB) |  | HTML iconHTML  

    The performance of the maximum likelihood (ML) estimator using fast and adaptive simulated annealing methods has been investigated for near-field localization of multiple narrowband sources. The estimation results are found to be close to the Cramer-Rao lower bound (CRLB). The effect of unknown parameters such as the source frequency, amplitudes and path loss factors is studied. The performance is found to improve with the increase in the signal-to-noise ratio (SNR) and snapshots. It is observed that nonlinearly quantized received samples can be successfully used in the ML estimator with little compromise in localization performance. An increase in the number of sensors, beyond a certain threshold number of sensors located closer to the sources, is found to provide only a marginal improvement in location estimation performance. View full abstract»

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  • Acoustic source localization in distributed sensor networks

    Page(s): 1328 - 1332 Vol.2
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (882 KB) |  | HTML iconHTML  

    This paper studies the problem of sound source localization in a distributed wireless sensor network formed by mobile general purpose computing and communication devices with audio I/O capabilities. In contrast to well understood localization methods based on dedicated microphone arrays, in our setting sound localization is performed using a sparse array of arbitrary placed sensors (in a typical scenario, localization is performed by several laptops/PDAs co-located in a room). Therefore any far-field assumptions are no longer valid in this situation. Additionally, localization algorithm's performance is affected by uncertainties in sensor position and errors in A/D synchronization. The proposed source localization algorithm consists of two steps. In the first step, time differences of arrivals (TDOAs) are estimated for the microphone pairs, and in the second step the maximum likelihood (ML) estimation for the source position is performed. We evaluate the Cramer-Rao bound (CRB) on the variance of the location estimation and compare it with simulations and experimental results. We also discuss the effects of distributed array geometry and errors in sensor positions on the performance of the localization algorithm. The performances of the system are likely to be limited by errors in sensor locations and increase when the microphones have a large aperture with respect to the source. View full abstract»

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  • A throughput scaling law for a class of wireless relay networks

    Page(s): 1333 - 1337 Vol.2
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (787 KB) |  | HTML iconHTML  

    In this paper we study coherent relaying in multi-antenna ad-hoc wireless networks. We suggest a one-hop relaying scheme suitable for multi-antenna relays; we demonstrate the value of employing multi-antenna transceivers in such coherent networks by deriving a scaling law that explicitly accounts for the same. We show that the throughput of such a network under the one-hop relaying protocol scales as R = Φ(L√N), where N is the number of nodes in the network and L is the number of antennas at each node. We also study and quantify the effect of imperfect channel state information (CSI) on the throughput of such coherent networks that depend centrally on the availability of CSI. View full abstract»

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  • [Breaker page]

    Page(s): 1338 - 1340
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  • Functions approximable by E-fractions

    Page(s): 1341 - 1344 Vol.2
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (566 KB) |  | HTML iconHTML  

    After a brief reminder of Ercegovac's E-method, we introduce the notion of E-fraction (which is a fraction computable, in a given interval, by the E-method). We characterize the fractions that are E-fractiions and give an algorithm for checking whether a given function is approximable by an E-fraction. View full abstract»

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  • 35+ years of computer arithmetic: a view from the trenches

    Page(s): 1345 - 1349 Vol.2
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    This paper reviews the author's experience in the area of computer arithmetic considering hardware (including analog multipliers, digital multipliers, multi term multiplier-adders, etc.), application to special purpose systems (including sonar equalizers, adaptive filters, etc.) and experience in teaching arithmetic concepts to graduate students. View full abstract»

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  • High speed binary addition

    Page(s): 1350 - 1353 Vol.2
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (521 KB) |  | HTML iconHTML  

    Addition of two binary numbers is a fundamental operation in electronic circuits. Applications include arithmetic logic unit, floating-point operations and address generation. It is widely accepted that there is no single best adder implementation. Modern adder architectures utilize a hybrid scheme based on, among others, various parallel prefix, carry select and Ling architectures. The parallel prefix method implements logic functions which determine whether groups of bits will generate or propagate a carry. These functions are hierarchically combined to calculate the carry into any bit. Ling adders reduce delay by using a simplified version of the group generates. However, the method only reduces complexity at the first level; all subsequent combinations in the hierarchy have the same complexity as the parallel prefix method. In this article we present novel architectures, which have reduced complexity at all, levels. View full abstract»

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  • Circuit design based on majority gates for applications with quantum-dot cellular automata

    Page(s): 1354 - 1357 Vol.2
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (544 KB) |  | HTML iconHTML  

    Majority gate-based logic is not normally explored with standard CMOS technologies, primarily because of the hardware inefficiencies in creating majority gates. As a result, not much effort has been made towards the optimization of circuits based on majority gates. We are exploring one particular emerging technology, quantum-dot cellular automata (QCA), in which the majority gate is the fundamental logic primitive. We report a simple and intuitive method for reduction of three-variable Boolean functions into a simplified majority representation. The method is based on Karnaugh maps (K-maps), used for the simplification of Boolean functions. View full abstract»

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  • Logical effort of higher valency adders

    Page(s): 1358 - 1362 Vol.2
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    Higher valency parallel prefix adders reduce the number of logic levels at the expense of greater fan-in at each level. This paper uses the method of logical effort to evaluate the tradeoffs of higher valency for static and dynamic implementations of various adder architectures. View full abstract»

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  • A hybrid Ling carry-select adder

    Page(s): 1363 - 1367 Vol.2
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (583 KB) |  | HTML iconHTML  

    Hybrid adders, combining a sparse carry-lookahead tree and a carry-select output stage are a well-known implementation form of high-speed adders. In this paper, a hybrid Ling carry-select adder is presented. It is shown how a carry-select output stage can be used to eliminate the entire conversion of all pseudo-carries. The adder is implemented in enhanced multiple output domino logic (EMODL). A technique is presented to avoid false discharge paths, which present impairment to EMODL, in the sum selection multiplexer. View full abstract»

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