Faculty publication: Ma, Cheng

November 7, 2011

Ma, R., & Cheng, S. (2011). The universality of generalized hamming code for multiple sources. [Article]. IEEE Transactions on Communications, 59(10), 2641-2647. doi: 10.1109/tcomm.2011.081711.100211

We consider zero-error Slepian-Wolf coding for a special kind of correlated sources known as Hamming sources. Moreover, we focus on the design of codes with minimum redundancy (i.e., perfect codes). As shown in a prior work by Koulgi et al., the design of a perfect code for a general source is very difficult and in fact is NP-hard. In our recent work, we introduce a subset of perfect codes for Hamming sources known as Hamming Codes for Multiple Sources (HCMSs). In this work, we extend HCMSs to generalized HCMSs, which can be proved to include all perfect codes for Hamming sources. To prove our main result, we first show that any perfect code for a Hamming source with two terminals is equivalent to a Hamming code for asymmetric Slepian Wolf coding (c.f. Lemma 2). We then show that any multi-terminal (of more than two terminals) perfect code can be transformed to a perfect code for two terminals (c.f. Lemma 3) and to a perfect code with an asymmetric form (c.f. Lemma 4). Equipped with these results, we prove that every perfect Slepian-Wolf code for Hamming sources is equivalent to a generalized HCMS. [ABSTRACT FROM PUBLISHER]

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Vaccines, Medicare, Minorities and More: New Reports From the National Academies Press

November 1, 2011

Check out these new titles and prepublications available from The National Academies Press (http://www.nap.edu/). All NAP titles can be read online or downloaded in PDF format free of charge! NAP publishes authoritative reports issued by the National Academy of Sciences, the National Academy of Engineering, the Institute of Medicine, and the National Research Council.

Adverse Effects of Vaccines: Evidence and Causality (prepublication), Board on Population Health and Public Health Practice, edited by Kathleen Stratton, Andrew Ford, Erin Rusch, and Ellen Wright Clayton

Early Childhood Obesity Prevention Policies (2011), Institute of Medicine, edited by Leann L. Birch, Lynn Parker, and Annina Burns

Expanding Underrepresented Minority Participation: America’s Science and Technology Talent at the Crossroads (2011), Committee on Science, Engineering, and Public Policy

Geographic Adjustment in Medicare Payment: Phase I: Improving Accuracy (prepublication), Second Edition, Board on Health Care Services

The Health of Lesbian, Gay, Bisexual, and Transgender People: Building a Foundation for Better Understanding (2011), Board on the Health of Select Populations

Help for Flood Victims

May 18, 2011

The MedlinePlus consumer health web site (medlineplus.gov) has created a page that links individuals to web sites providing high quality information on floods and flooding. You’ll find links to FEMA, CDC, EPA and Department of Homeland Security web sites to assist those needing information on topics such as flood disaster plans, cleanup, mold, air quality, power outages, water safety, repairing your flooded home and more.

Faculty publication: Wang, Cui, Cheng, Zhai, Yeary, Wu

April 28, 2011

Wang, S., Cui, L., Cheng, S., Zhai, Y., Yeary, M., & Wu, Q. (2011). Noise adaptive ldpc decoding using particle filtering. [Article]. IEEE Transactions on Communications, 59(4), 913-916. doi: 10.1109/tcomm.2011.011811.090309

Belief propagation (BP) is a powerful algorithm to decode low-density parity check (LDPC) codes over additive white Gaussian noise (AWGN) channels. However, the traditional BP algorithm cannot adapt efficiently to the statistical change of SNR in an AWGN channel. This paper proposes an adaptive scheme that incorporates a particle filtering (PF) algorithm into the BP based LDPC decoding process. The proposed scheme is capable to perform online estimation of time-varying SNR at the bit-level and enhance the BP decoding performance simultaneously.

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Faculty Publication: Ghosh, Verma

February 15, 2011

Ghosh, A. K., & Verma, P. (2011). Lyapunov exponent of chaos generated by acousto-optic modulators with feedback. [Article]. Optical Engineering: The Journal of the Society of Photo-Optical Instrumentation Engineers, 50(1), 017005-017005-017005.

Generation of chaos from acousto-optic modulators with an electronic feedback has been studied for several years. Such chaotic signals have an important application in providing secure encryption in free-space optical communication systems. Lyapunov exponent is an important parameter for analysis of chaos generated by a nonlinear system. The Lyapunov exponent of an acousto-optic system is determined and calculated in this paper to understand the dependence of the chaotic response on the system parameters such as bias, feedback gain, input intensity and initial condition exciting the cell. Analysis of chaos using Lyapunov exponent is consistent with bifurcation analysis and is useful in encrypting data signals.

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Faculty Publication: Zhang, Verma, Cheng

January 13, 2011

Zhang, F., Verma, P. K., & Cheng, S. (2011). Pricing, resource allocation and quality of service in multi-class networks with competitive market model. [Article]. IET Communications, 5(1), 51-60. doi: 10.1049/iet-com.2009.0694

This study considers a multi-class network resource in a competitive market where each user endowed with an initial budget will purchase bandwidth from each class of the network resource to maximise its utility function. The authors use revenue as the utility function for the service provider, and enhance Kelly’s utility function by including delay as the quality of service (QoS) parameter for users. A competitive equilibrium is reached when the total bandwidth is allocated, each user spends all its budget and the utility functions are independently and simultaneously maximised. The authors prove that such equilibriums always exist and, under fixed bandwidth supply for each class of service, the equilibrium is also unique. Furthermore, the authors discuss how to adjust the initial endowment of each user to meet his or her individual bandwidth constraint, either from constraint on the access network or the limitation of the user equipment. Under this bandwidth constraint condition, the proposed competitive equilibrium yields the price for each class of service, budget redistribution and bandwidth allocation among all users. The competitive market model presented provides a solution for pricing a multi-class network resource and allocating the resource that achieves both higher social utility and better individual satisfaction whereas maintaining the QoS of each class.

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Student and Faculty Publication: Tachwali, Basma, & Refai

November 4, 2010

Tachwali, Y., Basma, F., & Refai, H. (2010). Cognitive radio architecture for rapidly deployable heterogeneous wireless networks. [Article]. IEEE Transactions on Consumer Electronics, 56(3), 1426-1432. doi: 10.1109/tce.2010.5606279

Recent technological advances in cognitive radio based on software defined radio platforms have extended the capabilities of wireless communication systems. The unique ability to alter communication protocols to meet changing system demands makes cognitive radio suitable for wireless applications otherwise difficult to implement using conventional wireless terminals. One such wireless application is the rapid deployment of a heterogeneous wireless network for the purpose of establishing a communication infrastructure between an incompatible set of wireless consumer devices. This paper presents the design and implementation details of cognitive radio terminals used to build a rapidly deployable, frequency-agile, heterogeneous wireless network. Research findings assisted researchers in the development of a wireless transceiver capable of connecting a variety of wireless transceivers, detecting the presence of interference, and accordingly switching to available channels as allocated by its spectrum sensing capability. The focus of this paper is to propose an architecture for cognitive radio terminals that can be used to build rapidly deployable wireless network applications.

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