Localization is very important for self-organizing wireless networks. The localization process involves two main steps: ranging, i.e., estimating the distance between an unlocalized node and the anchor nodes within its range, and the localization algorithm to compute the location of the unlocalized nodes using the anchor coordinates and the estimated ranges. To be able to estimate the distance, the receiver needs to detect the arrival time of the received signals precisely. Thus, the first part of this research is related to time synchronization. We propose two new symbol timing offset estimation (STO) algorithms that can detect the start of an orthogonal frequency division multiplexing (OFDM) symbol more accurately than others in a Rayleigh fading channel. OFDM is used to perform timing synchronization because it is incorporated inmany current and future wireless systems such as 802.11, WiMAX, wireless USB, and WiMedia. The first proposed algorithm uses a metric that is calculated recursively. Two estimation methods are considered: one using the average of the metric results, and the other using the median. The second approach uses a preamble designed to have a maximum timing metric for the correct location and very small values otherwise. These algorithms are shown to outperform recent algorithms in the literature. In the second part of this dissertation we explore the second step of the localization problem. There are two kinds of localization: range-free and range-based. A new distributed range-free localization algorithm is proposed where every unlocalized node forms two sets of anchors. The first set contains one-hop anchors from the unlocalized node. The second set contains two-hop and three-hop anchors away from the unlocalized node. Each unlocalized node uses the intersections between the ranging radii of these anchors to estimate its position. Four different range-based localization algorithms are proposed. These algorithms use techniques from data mining to process the intersection points between an unlocalized node and nearby anchors. The first proposed scheme is based on decision tree classification to select a group of intersection points. The second is based on the decision tree classification and K-means clustering algorithms applied to the selected intersection points by the decision trees. The third is based on decision tree classification and the density-based spatial clustering of applications with noise (DBSCAN) algorithm applied to the intersection points selected by decision trees. The last approach uses the density-based outlier detection (DBOD) algorithm. DBOD assigns density values to each point being used in the location estimation. The mean of these densities is calculated and those points having a density larger than the mean are kept as candidate points. These proposed approaches are shown to outperform recent algorithms in the literature. / Graduate

Synchronization is a problem of fundamental importance for a wide range of practical communication systems including reading media, multi-user optical channels, synchronous digital communication systems, packet-switched communication networks, distributed computing systems, etc. In this thesis I study various aspects of communication over channels with symbol synchronization errors. Symbol synchronization errors are harder to model than erasures or substitution errors caused by additive noise because they introduce uncertainties in timing. Consequently, the capacity of channels subjected to synchronization errors is a very challenging problem, even when considering the simplest channels for which only deletion errors occur. I improve on the best existing lower and upper bounds for the capacity of the deletion channel using convex and stochastic optimization techniques. I also show that simply finding closed-form expressions for the number of subsequences when deleting symbols from a string is computationally prohibitive. Constructing efficient synchronization error-correcting codes is also a challenging task. The main result of the thesis is the design of a new family of codes able to correct several types of synchronization errors. The codes use trellis and modified versions of the Viterbi decoding algorithm, and therefore have very low encoding and decoding complexities. They also have high data rates and work for reasonably noisy channels, which makes them one of the first synchronization-correcting codes that have any chance of being used in practical systems. In the last part of the thesis, I show that a synchronization approach can solve the opportunistic spectrum access problem in cognitive radio, where cognitive users want to communicate in presence of legacy users to whom the bandwidth has been licensed. I also consider the amount of communication required to solve a large class of distributed problems where synchronization errors can occur. More precisely, I study how allowing the parties to solve the problems incorrectly with small probability can reduce the total amount of communication or the number of messages that need to be exchanged.

Thesis (M.A.)--Ohio State University, 2009. / Title from first page of PDF file. Includes vita. Includes bibliographical references (p. 22-23).

Thesis (M.S.)--Purdue University, 2004. / Includes bibliographical references (leaves 56-59). Also available online (PDF file) by a subscription to the set or by purchasing the individual file.

Thesis (M.S.)--Purdue University, 2004. / Includes bibliographical references (leaves 56-59).

Thesis (M.S. in electrical engineering)--Washington State University, August 2007. / Includes bibliographical references (p. 49-51).

Thesis (M.S.) -- Carnegie-Mellon University, 1979. / Bibliography : leaves 69-71.

No description available.

Class of 2015 Abstract / Objectives: Our specific aim is to assess the changes in patient adherence in response to medication synchronization. Our working hypothesis is that medication synchronization will have a positive impact on patient adherence. Methods: This retrospective pre-post cohort study assessed medication adherence 365 days before and 365 days after enrollment into a prescription synchronization program. There were 5,994 patients included in the study. Seven medication classes and three demographic groups were chosen to assess for adherence. Adherence was determined by calculating mean proportion of days covered. A paired t-test was used to determine statistical significance for each drug class and demographic group. Exploratory analyses were done at 90 days and 180 days before and after the sync date to determine differences in terms of time. An alpha a-priori was set at 0.05 before analysis was started. Results: Current Fry’s Pharmacy patients greater than 18 years old that met the Centers for Medicare and Medicaid Services (CMS) for STARs rating criteria were included in the study. Results at 365 days showed a statistically significant decrease in PDC (p<0.0001), and was not affected by demographics. Conclusions: One year after the implementation of medication synchronization program at Fry’s Pharmacy, a statistically significance decrease in PDC is seen across all categories of chronic medications: statins, ACE-I/ARBs, beta-blockers, CCBs, metformin, thiazides, loop-diuretics, and inhaled corticosteroids. As such, medication synchronization may decrease patient adherence to the maintenance medications evaluated.

Ph.D. (Electrical & Electronic Engineering) / In the ideal communication system no noise is present and error free communication is possible. In practice, however, several factors influence the correctness of· the communication. One of the most important of these factors is the synchronization of the message. Synchronization techniques form an integral part of data communication systems and without synchronization no comprehensible message can be received. An example of a communication system in which synchronization errors occur is the plesiochronous communication network which is used in many telephone networks [49,50]. A common problem with the use of the multiplexers in such a network is that output pulses may occur that do not contain valid data, due to minor discrepancies in the clock frequencies of the incoming signals. These inserted bits are termed ''justification bits" and their presence is signaled over the link by the justification control bits or stuffing control bits, which are included in the frame [49 and 50]. Synchronization of the network is dependent, among other factors, on the correct decoding of the stuffing control bits. Synchronization at the receiver can also be lost when the frame markers are not recognizable due to errors on the channel...