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Software Approach to Access UWB Interference on GPS Receivers
Get PDFEver since the FCC approved the use of UWB devices in commercial and federal bands, various agencies whose operations and/or products rely on the integrity of signals within certain â restrictedâ radio frequency hands have voiced concerns over the potential impact of the UWB interference. GPS signals are among these â restrictedâ bands. Several groups in the GPS community have conducted experimental studies concerning the impact of UWB interference on the performance of various grades of commercial and aviation GPS receivers. In this paper, we present a software approach to simulate and evaluate UWB interference on GPS receivers. The software approach provides greater flexibility in the design of testing scenarios, such as the inclusion of a large number of aggregated UWB devices, the generation of new UWB signals and modulation schemes, and the possibility of extending the study to new GPS signals. The paper will discuss a general framework for developing algorithms to evaluate UWB and GPS interference under a wide variety of hardware and software conditions. This framework consists of three classes of components: Input, Processing, and Analysis. The input components are responsible for the generation of UWB signal waveforms and modulation schemes, and GPS signals. The processing components include a simulated model of GPS RF front end and software implementation of GPS processing blocks, such as acquisition, tracking, and post-processing. The Analysis components focus on the study of specsic receiver processing component outputs. Both real and simulated UWB signals can he used in the study. The real UWB signals are primarily used to validate the simulation procedure, whereas the simulated UWB signals are used to allow the immediate incorporation of new UWB waveforms and modulations in the evaluations. This paper will present details of the software components developed and the preliminary results achieve
Images of Ohio Centenarians : An Exploratory Study
Get PDFThis research report presents findings from face-to-face qualitative interviews with 16 centenarians residing in southwest, central, and northeast Ohio. Our research focused on the following questions: How do centenarians adapt to remain in control of their physical and social environments? How do they sustain morale and motivation in the face of waning energy and declining physical abilities? How do they view the world from their vantage point? How do they interpret the past in light of the many drastic, if not revolutionary changes, they have witnessed in the course of their long lives? How do they go about making meaning of their experience? How do they tell their life stories
GPS Civil Signal Self-Interference Mitigation During Weak signal Acquisition
Get PDFCurrent global positioning system receivers can acquire weak satellite signals with = 15 dB/Hz if there is no self-interference from other strong satellite signals. This correspondence presents a computational efficient partitioned subspace projection method to mitigate the self-interference. The method is evaluated using simulated signals and a block-based weak signal acquisition algorith
Ohio Residential Care Facility Resident Satisfaction Survey : Instrument Refinements [2007]
Get PDFThis report describes psychometric testing and other evaluations of the 2007 Ohio Residential Care Resident Satisfaction Survey. Recommendations include removal of items to shorten the survey and refinement of other items
Mitigation of GPS Multipath Using Polarization and Spatial Diversities
Get PDFThis paper presents a GPS multipath mitigation method using a dual circularly polarized antenna array and a multi-channel receiver. The method is based on the exploitation of both polarization and spatial diversity associated with a GPS signal and its multipath signals available at the receiver input. Conventional GPS antennas are right-hand circularly polarized (RHCP) to suppress multipath contributions to the input. This polarization-based discrimination of multipath signal cannot completely eliminate multipath induced GPS range measurement errors. We present an algorithm that performs spatial processing on the input from the left-hand circular polarized (LHCP) array with an increased relative strength of the multipath signal, thereby providing improved multipath angle of arrival (AOA) estimation. With the known multipath AOA and direct signal AOA (which can be obtained from almanac/ephemeris together with the antenna attitude or estimated in a separate process), we can then take advantage of the spatial diversity of the direct signal and multipath by applying null-steering to the RHCP array input. The paper presents the algorithm and simulation results for a uniform linear array receiving one direct signal and one multipath. Our preliminary studies showed that the multipath AOA estimator produces negligible error if the direct signal and multipath AOA are not close to each other (more than 5 degrees apart) and that the direct signal is not at low elevation. The results also suggested that longer time delay between the direct and multipath signal will increase multipath AOA estimation error but this increase is tolerable. Furthermore, we demonstrated that the multipath estimation improves with increasing spatial diversity for multipath and direct GPS signals even if the signal arrivals are close in time. Finally, we demonstrated that the multipath mitigation technique does produce an improved receiver correlator function which directly impacts the GPS code range measurement accurac
Gravity Wave Propagation in a Nonisothermal Atmosphere with height Varying Background Wind
Get PDFWe derive a gravity wave propagation equation for a compressible and non-isothermal atmosphere with a variable background wind profile. Impact of all the gradient terms on the vertical wavenumber depends only on the intrinsic horizontal phase velocity and the background atmosphere. For the background wind variation, any one of the linear first order derivative, second order derivative and the square of the first order derivative terms can be the dominant term under different conditions. For temperature variation, only the linear first order derivative is important for waves having a slow intrinsic horizontal phase velocity. Our equation indicates that the effect of wind shear on the vertical wavenumber is opposite to that predicted by the Taylor-Goldstein equation, which assumes an incompressible fluid. We also derive an expression for the amplitude of the vertical wind perturbation. Citation: Zhou, Q., and Y. T. Morton (2007), Gravity wave propagation in a nonisothermal atmosphere with height varying background wind, Geophys. Res. Lett., 34, L23803, doi:10.1029/2007GL031061
Enhancing the Performance of Local Long-Term Care Ombudsman Programs in Ohio: Chartbook
Get PDFThis is a state-level case-study of the performance of local Long-Term Care Ombudsman Programs in Ohio. In surveying all of the local program directors in Ohio, along with a group of key informants, we identify major strengths and challenges the program is likely to face in the future. Funding and staffing emerge as prominent issues, particularly in determining the longer-term educational and advocay roles these programs ideally fulfill
A Floating Vertical TEC Ionosphere Delay Correction Algorithm for Single Frequency GPS Receivers
Get PDFThis paper presents an innovative method to mitigate ionosphere delay error for single frequency receivers. Traditional approach to ionosphere delay correction is carried out through modeling the total electron content (TEC) along each satellite signal path. Because of the large deviation of the TEC during different times of the day, season, and solar cycle from any mean measurements, the ionosphere delay error has always been the dominant error factor in signal frequency receivers. In our method, we allow a reference vertical TEC to â floatâ or to remain as an unknown in the range equation. The TEC along each satellite signal path is modeled as having its own vertical TEC whose major component is the reference vertical TEC with additional contributions from the TEC spatial derivatives. The TEC spatial derivatives can be modeled using existing ionosphere models, services that provide ionosphere measurements, or even better, the ionosphere correction algorithm (ICA) coefficients which are part of the navigation message. By having the reference vertical TEC as an additional unknown in the range equations, a minimum of five satellites is required to obtain the receiver position. As a byproduct of the range equation solution, we also solve for the reference vertical TEC which can be a convenient and inexpensive way to provide information on the ionosphere. The paper describes the detailed algorithm and simulation studies that demonstrate order of magnitude improvement in ionosphere error correction using this method over the conventional method
Case Study of Mesospheric Gravity Wave Momentum Flux and Dynamical Instability Using the Arecibo Dual Beam Incoherent Scatter Radar
Get PDFWe report the first observation of gravity wave momentum flux in the mesosphere using the dual-beam Arecibo incoherent scatter radar (ISR). Quasimonochromatic waves were observed throughout the daytime of July 28, 2001 in the altitude range of 65â 85 km. The largest wave speed was about 100 m/s and the dominant period was about 15 min. Instability, as indicated by the Richardson number, occurred at several altitudes, most dramatically at 77 and 81 kilometers. The zonal momentum flux is found to change sign at altitudes where dynamical instability occurs. No significant gravity waves were observed in the region having an eastward background wind, while they were ubiquitous when the background wind was westward. Citation: Zhou, Q., and Y. T. Morton (2006), A case study of mesospheric gravity wave momentum flux and dynamical instability using the Arecibo dual beam incoherent scatter radar, Geophys. Res. Lett., 33, L10802, doi:10.1029/ 2005GL025608