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Degree-constrained Minimum Latency Trees are APX-Hard
Get PDFWhen transmitting data from a single source to many recipients, it is often desirable to use some recipients of the stream to re-broadcast the stream to other users. In such multicast systems each client may be used as a server, serving up to B other clients. Formally, we will take a set X of clients, along with a distance function d that specifies the latency (in the host network) between each pair of clients in X. Our goal will be to produce a directed spanning tree of X, rooted at some specified root 2 X, with out-degree bounded by B, and minimizing the sum of the latencies from root to every point in X. In addition to being motivated by current experimental algorithms work, the problem also interpolates naturally between the traveling repairman problem (when B = 1) and single source shortest paths (when B = n − 1). The former problem is APX-complete (in metric spaces) and the latter is in P. We explore the hardness of the problem for other values of B. In particular, we show that the problem remains APX-Hard at least up to B = Cpn for some universal constant C when the host space is a general semi-metric
Interference Cancellation Using Power Minimization and Self-coherence Properties of GPS Signals
Get PDFThis paper presents the performance analysis of two digital beam forming techniques used in conjunction with a software GPS receiver to mitigate interference to GPS signals in interference environment. The first method is the constrained minimum power (MOP) method. The second method is the so-called self-coherence restoral (SCORE) method. Both experimental and simulation data are used in the study. The study was performed using experiment data collected in an anechoic chamber to obtain GPS and interference signals. A two by two GPS antenna array and a four channel radio frequency front end were used to collect simulated GPS data generated using hardwarebased simulator in controlled interference environment. Three types of interference signals are deployed in the experiments: FM chirp, binary phase shift key, and broadband. The interference power levels used were +20, +30, and +40 dB above GPS signal power. A software GPS receiver was used to perform acquisition of GPS signals to evaluate the performance of the beam forming algorithms. The preliminary result showed that the MOP method can effectively mitigate all three types of interference at all power levels if a single interference source is present. Experiments using multiple broadband interference sources were also analyzed and our results shown that the effectiveness of the MOP method diminishes as the interference signal power increases and ceases to function at the +40 dB level. The SCORE method does not exhibit consistent performance for the experimental data. This is consistent with our simulation results which show that for the SCORE algorithm to generate satisfactory results, sufficient number of antenna elements is necessary even if there is no interference source present. The number of antenna element is determined by the number of satellites available, as well as the number of interference sources. The experimental and simulation results are discussed in this paper
Developing Specifications for the Competitive Bidding of Intake, Assessment & Case Management Services
Get PDFThis report provides information about the elements of case management, intake, and assessment programs that are often specified in current standards or bid specifications. Observation of current practices, a literature review, and key informant interviews were used to develop recommendations for the Council on Aging of Southwestern Ohio to develop bid specifications for the Butler County ESP
An ANOVA-Based GPS Multipath Detection Algorithm Using Multi-Channel Software Receivers
Get PDFWe present a statistical detection test for GPS multipath based on the one-way ANOVA method. Given an antenna array with a GPS software receiver in tracking mode, the signal from each channel is correlated with a reference signal in blocks of one CA code period. When the relative phase delay for the direct GPS signal is stripped off from each channel, the expected values of the correlates is the same for all of the channels only if no multipath is present. A one-way ANOVA test can then used to determine if multipath is present. An analysis of this method is presented which shows that the parameters affecting its detection performance can be grouped into three classes: the array size, the signal AOAs, and the processed multipath SNR. Receiver operating characteristic curves are given as a function of the processed multipath SNR for fixed array sizes. They show that good detection performance can be achieved under most operating conditions with less than 10 CA code periods of data. It is also shown that the detection performance of this method improves as the multipath time delay decreases. This suggests this method could be a useful tool in aiding multipath mitigation techniques whose ability to detect multipath typically degrades as the multipath time delay decreases
Neural Network Development for the Forecasting of Upper Atmosphere Parameter Distributions
Get PDFThis paper presents a neural network modeling approach to forecast electron concentration distributions in the 150â 600 km altitude range above Arecibo, Puerto Rico. The neural network was trained using incoherent scatter radar data collected at the Arecibo Observatory during the past two decades, as well as the Kp geomagnetic index provided by the National Space Science Data Center. The data set covered nearly two solar cycles, allowing the neural network to model daily, seasonal, and solar cycle variations of upper atmospheric parameter distributions. Two types of neural network architectures, feedforward and Elman recurrent, are used in this study. Topics discussed include the network design, training strategy, data analysis, as well as preliminary testing results of the networks on electron concentration distributions
Miami University Technical Report: Dynamic Resource Allocation in Integrated Optical Wireless Access Architectures (Version 1, October 2008)
Get PDFWe consider integrated optical-wireless access network architectures. We propose and evaluate dynamic resource allocation algorithms for such architectures with an explicit incorporation of the reconfiguration delays. Algorithmic complexity results are also presented
Livable Communities : Helping Older Ohioans Live Independent and Fulfilling Lives
Get PDFThis report defines the concept and components of livable communities and several variations, including universal design and green spaces
On Co-Existence of In-Band UWB-OFDM and GPS Signals: Tracking Performance Analysis
Get PDFThe problem of in-band co-existence between GPS and other potential interfering signals is viewed from the following angle in this paper: Is there a coding or modulation technique which would permit simultaneous use of GPS and other RF services occupying same bandwidth? Very low interference between the UWB radar and GPS signals can be achieved by shaping radar pulses using orthogonal frequency division multiplexing (OFDM) coding, which is a multi-carrier modulation technique targeted for commercial UWB communications. The paper shows that we can, in fact, expect a very good degree of interoperability of a system used for GPS reception and UWB-OFDM radar purposes. The benefits of using UWB sensor in conjunction with GPS can be for example, to supplement positioning algorithms with radar-collected data, as well as to perform general reconnaissance of the surrounding area. The paper includes detailed analysis of the proposed multiple-use UWB-OFDM radar/GPS receiver concept, the effect of co-existing UWB-OFDM signals on GPS receiver tracking loop carrier noise level, and the impact on the quality of GPS solution in weak GPS signal environment. A brief discussion of MATLAB implementation of the modeled scenarios is presented as well
Disability in Ohio : Current and Future Demand for Services
Get PDFIn an effort to project the size of Ohio s Medicaid long-term care expenditures between now and the year 2020, this report first projected the size of the population with severe physical and/or cognitive, intellectual and/or developmental, and mental illness disabilities. Then, assuming different rates of medical and long-term care inflations the author projected both the total Medicaid and Medicaid long-term care expenditures
Ohio's Aging Workforce : Opportunities & Challenges for Ohio's Employers
Get PDFThis report focuses on anticipated age-related changes in Ohio's workforce and the effect those changes might have on employers, employees, and society. In addition to a literature review, Ohioans and their reasons for continuing to work are featured