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

Making sense: talking data management with researchers

Incremental is one of eight projects in the JISC Managing Research Data programme funded to identify institutional requirements for digital research data management and pilot relevant infrastructure. Our findings concur with those of other Managing Research Data projects, as well as with several previous studies. We found that many researchers: (i) organise their data in an ad hoc fashion, posing difficulties with retrieval and re-use; (ii) store their data on all kinds of media without always considering security and back-up; (iii) are positive about data sharing in principle though reluctant in practice; (iv) believe back-up is equivalent to preservation. <br></br><br></br> The key difference between our approach and that of other Managing Research Data projects is the type of infrastructure we are piloting. While the majority of these projects focus on developing technical solutions, we are focusing on the need for ‘soft’ infrastructure, such as one-to-one tailored support, training, and easy-to-find, concise guidance that breaks down some of the barriers information professionals have unintentionally built with their use of specialist terminology. <br></br><br></br> We are employing a bottom-up approach as we feel that to support the step-by-step development of sound research data management practices, you must first understand researchers’ needs and perspectives. Over the life of the project, Incremental staff will act as mediators, assisting researchers and local support staff to understand the data management requirements within which they are expect to work, and will determine how these can be addressed within research workflows and the existing technical infrastructure. <br></br> <br></br> Our primary goal is to build data management capacity within the Universities of Cambridge and Glasgow by raising awareness of basic principles so everyone can manage their data to a certain extent. We will ensure our lessons can be picked up and used by other institutions. Our affiliation with the Digital Curation Centre and Digital Preservation Coalition will assist in this and all outputs will be released under a Creative Commons licence. The key difference between our approach and that of other MRD projects is the type of ‘infrastructure’ we are piloting. While the majority of these projects focus on developing technical solutions, we are focusing on the need for ‘soft’ infrastructure, such as one-to-one tailored support, training, and easy-to-find, concise guidance that breaks down some of the barriers information professionals have unintentionally built with their use of specialist terminology. We are employing a bottom-up approach as we feel that to support the step-by-step development of sound research data management practices, you must first understand researchers’ needs and perspectives. Over the life of the project, Incremental staff will act as mediators, assisting researchers and local support staff to understand the data management requirements within which they are expect to work, and will determine how these can be addressed within research workflows and the existing technical infrastructure. Our primary goal is to build data management capacity within the Universities of Cambridge and Glasgow by raising awareness of basic principles so everyone can manage their data to a certain extent. We’re achieving this by: - re-positioning existing guidance so researchers can locate the advice they need; - connecting researchers with one-to-one advice, support and partnering; - offering practical training and a seminar series to address key data management topics. We will ensure our lessons can be picked up and used by other institutions. Our affiliation with the Digital Curation Centre and Digital Preservation Coalition will assist in this and all outputs will be released under a Creative Commons licence

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

Incremental scoping study and implementation plan

This report is one of the first deliverables from the Incremental project, which seeks to investigate and improve the research data management infrastructure at the universities of Glasgow and Cambridge and to learn lessons and develop resources of value to other institutions. Coming at the end of the project’s scoping study, this report identifies the key themes and issues that emerged and proposes a set of activities to address those needs. As its name suggests, Incremental deliberately adopts a stepped, pragmatic approach to supporting research data management. It recognises that solutions will vary across different departmental and institutional contexts; and that top-down, policy-driven or centralised solutions are unlikely to prove as effective as practical support delivered in a clear and timely manner where the benefits can be clearly understood and will justify any effort or resources required. The findings of the scoping study have confirmed the value of this approach and the main recommendations of this report are concerned with the development and delivery of suitable resources. Although some differences were observed between disciplines, these seemed to be as much a feature of different organisational cultures as the nature of the research being undertaken. Our study found that there were many common issues across the groups and that the responses to these issues need not be highly technical or expensive to implement. What is required is that these resources employ jargon-free language and use examples of relevance to researchers and that they can be accessed easily at the point of need. There are resources already available (institutionally and externally) that can address researchers’ data management needs but these are not being fully exploited. So in many cases Incremental will be enabling efficient and contextualised access, or tailoring resources to specific environments, rather than developing resources from scratch. While Incremental will concentrate on developing, repurposing and leveraging practical resources to support researchers in their management of data, it recognises that this will be best achieved within a supportive institutional context (both in terms of policy and provision). The need for institutional support is especially evident when long-term preservation and data sharing are considered – these activities are clearly more effective and sustainable if addressed at more aggregated levels (e.g. repositories) rather than left to individual researchers or groups. So in addition to its work in developing resources, the Incremental project will seek to inform the development of a more comprehensive data management infrastructure at each institution. In Cambridge, this will be connected with the library’s CUPID project (Cambridge University Preservation Development) and at Glasgow in conjunction with the Digital Preservation Advisory Board

Invasive Wild pigs as primary nest predators for Wild turkeys

Depredation of wild turkey (Meleagris gallopavo) nests is a leading cause of reduced recruitment for the recovering and iconic game species. invasive wild pigs (Sus scrofa) are known to depredate nests, and have been expanding throughout the distributed range of wild turkeys in north America. We sought to gain better insight on the magnitude of wild pigs depredating wild turkey nests. We constructed simulated wild turkey nests throughout the home ranges of 20 GPS-collared wild pigs to evaluate nest depredation relative to three periods within the nesting season (i.e., early, peak, and late) and two nest densities (moderate = 12.5-25 nests/km2, high = 25-50 nests/km2) in south-central Texas, USA during March–June 2016. Overall, the estimated probability of nest depredation by wild pigs was 0.3, equivalent to native species of nest predators in the study area (e.g., gray fox [Urocyon cinereoargenteus], raccoon [Procyon lotor], and coyote [Canis latrans]). female wild pigs exhibited a constant rate of depredation regardless of nesting period or density of nests. However, male wild pigs increased their rate of depredation in areas with higher nest densities. Management efforts should remove wild pigs to reduce nest failure in wild turkey populations especially where recruitment is low

A new search for interstellar C3

A new, very sensitive search for interstellar triatomic carbon has resulted in upper limits for a few diffuse clouds of order 1010 cm – 2, or about 10 – 11 with respect to hydrogen. These limits are consistent with recent cold diffuse cloud chemistry models, but may be in conflict with shocked cloud models such as those invoked to explain CH + abundances. Our results may also be argue against linear carbon-chain molecules as carriers of the diffuse interstellar bands

Predicting peculiar interstellar extinction from gaseous abundances

Molecular and atomic abundances are examined for 19 lines of sight through dense clouds, each with a peculiar selective extinction curve. The interstellar clouds in the present study appear to fall into two distinct categories: CN-rich, with relatively small amounts of neutral iron, or CN-poor, with large amounts of neutral iron. Lines of sight, having a CN/(Fe i) abundance ratio about two (~ 0.3 dex) or greater, are found to have a shallow (2.57 ± 0.55 mag) 2175 Å feature relative to the underlying extinction, while the strength of the bump is 3.60 ± 0.36 for the other dense clouds in the present study. The difference in the strength of the extinction bump between these two ensembles is 1.03 ± 0.23. Several atomic abundances are examined as potential indicators of peculiar extinction. Mn i abundances in particular are sought at 10 times greater sensitivity than previous studies because of a possible empirical connection between a small (Mn ii)/(Fe ii) abundance ratio and a weak 2175 Å bump reported in the literature. Unfortunately, the abundances of the neutral atoms do not appear to scale with the abundance of CN, reducing the effectiveness of Mn i as a diagnostic tool. Nevertheless, the Mn i upper limits in the present study support Mn being preferentially depleted. Fe i is underabundant relative to K i by 0.7 (dex) in the large (CN)/(Fe i) compared to the small (CN)/(Fe i) lines of sight. In addition, the data suggest that potassium is substantially depleted in both types of dense cloud