Performance Analysis and Enhancement of Multiband OFDM for UWB Communications

In this paper, we analyze the frequency-hopping orthogonal frequency-division multiplexing (OFDM) system known as Multiband OFDM for high-rate wireless personal area networks (WPANs) based on ultra-wideband (UWB) transmission. Besides considering the standard, we also propose and study system performance enhancements through the application of Turbo and Repeat-Accumulate (RA) codes, as well as OFDM bit-loading. Our methodology consists of (a) a study of the channel model developed under IEEE 802.15 for UWB from a frequency-domain perspective suited for OFDM transmission, (b) development and quantification of appropriate information-theoretic performance measures, (c) comparison of these measures with simulation results for the Multiband OFDM standard proposal as well as our proposed extensions, and (d) the consideration of the influence of practical, imperfect channel estimation on the performance. We find that the current Multiband OFDM standard sufficiently exploits the frequency selectivity of the UWB channel, and that the system performs in the vicinity of the channel cutoff rate. Turbo codes and a reduced-complexity clustered bit-loading algorithm improve the system power efficiency by over 6 dB at a data rate of 480 Mbps.Comment: 32 pages, 10 figures, 1 table. Submitted to the IEEE Transactions on Wireless Communications (Sep. 28, 2005). Minor revisions based on reviewers' comments (June 23, 2006

Error Rate Analysis for Coded Multicarrier Systems over Quasi-Static Fading Channels

This paper presents two methods for approximating the performance of coded multicarrier systems operating over frequency-selective, quasi-static fading channels with non-ideal interleaving. The first method is based on approximating the performance of the system over each realization of the channel, and is suitable for obtaining the outage performance of this type of system. The second method is based on knowledge of the correlation matrix of the frequency-domain channel gains and can be used to directly obtain the average performance. Both of the methods are applicable for convolutionally-coded interleaved systems employing Quadrature Amplitude Modulation (QAM). As examples, both methods are used to study the performance of the Multiband Orthogonal Frequency Division Multiplexing (OFDM) proposal for high data-rate Ultra-Wideband (UWB) communication.Comment: 5 pages, 3 figures, 2 tables. Submitted to Globecom 200

Evaluation of a computing and engineering outreach program for girls in grades 8–10

An outreach program of workshops and guided group activities for New Hampshire\u27s eighth, ninth and tenth grade girls was offered to stimulate the girls\u27 interest in computing and engineering coursework and careers. Attitude changes before and after participation were measured using a survey instrument adapted from one developed by the Georgia Tech\u27s Institute for Computing and Education. Eight attitudinal themes were surveyed. With suitable adjustments for simultaneous testing of multiple hypotheses, statistically significant changes with moderate effect sizes were detected for three of the themes: enjoyment of technology-related activities, motivation to succeed in technical problem solving, and intention to persist in computing and engineering courses and careers

Interstellar abundance determination using IUE data

Analysis of the silicon interstellar abundances was made for more heavily reddened lines of sight than were accessible to the Copernicus satellite. Silicon rarely had accurate column densities determined from Copernicus data because the available lines all lie on the flat portion of the curve of growth. With International Ultraviolet Explorer (IUE) it is possible to reach color excesses of E(B-V) approximately 0.5-0.7, and in addition obtain data on the weak SiII line at 1808 A, so that a wide range of oscillator strengths is available. The lower resolving power of the IUE causes difficulties in that several of the SiII lines are blended with strong lines of other species. Data on the lines of sight analyzed suggested that some of the absorption lines fall on the damped portion of the curve of growth, implying that silicon may not be as highly depleted as expected

Judicial Review in Expedited Removal Proceedings: Applying Sims v. Apfel to Assess the Role of Issue Exhaustion

For noncitizens in expedited removal proceedings, obtainingjudicial review of removal orders is an uphill battle. Somebarriers to judicial review are statutory: noncitizens must firstexhaust their administrative remedies, and they may seekreview only in a federal circuit court of appeals. Other barriersare judicial—i.e., imposed by courts, not statutes.A circuit split has emerged over one of these judiciallyimposed barriers to judicial review. Some courts have held thatexpedited removal proceedings do not accommodate legalchallenges to removal. In those circuits, noncitizens preserve theopportunity for judicial review even when they do not raise alegal challenge during those proceedings. Other courts haveheld that noncitizens must contest the legal grounds for theirremoval during expedited removal proceedings. This circuitsplit has fragmented the judicial review process for expeditedremoval orders, with detrimental effect.In Sims v. Apfel, the U.S. Supreme Court provided aframework for assessing the propriety of a judicially imposedissue-exhaustion requirement. Central to the Court’s analysiswas the degree to which administrative proceedings areinquisitorial rather than adversarial. But expedited removalproceedings are neither inquisitorial nor adversarial, and theyoffer far fewer procedural protections than full removalproceedings. This Note argues that, under Sims, requiring issueexhaustion is inappropriate in appeals from expedited removalproceedings. In the absence of a statutory mandate, circuitcourts should not construct an additional barrier to judicialreview by imposing an issue-exhaustion requirement

The Unconstitutional Prosecution of Controlled Substance Metabolites Under Utah Code § 41-6A-517

This Article achieves three main goals. First, it explains and explores Utah’s per se metabolite laws against the backdrop of the national landscape of metabolite laws. Second, this Article provides a concise explanation regarding the science of drug metabolites. Finally, this Article presents two constitutional challenges to Utah Code section 41-6a-517. The first challenge argues that the statute creates an impermissible status offense in violation of the Eighth Amendment to the U.S. Constitution. The second challenge argues that the statute violates Utah’s Uniform Operation of Laws Clause found in the Utah Constitution. This Article concludes by asking Utah state courts and state legislature to examine the validity of Utah Code section 41-6a-517 and ultimately to overturn the statute