Location-based Services (LBSs) are important building blocks for a wide spectrum of context-aware applications. The Global Positioning System (GPS) has provided almost ubiquitous positioning services in outdoor environments and enabled many outdoor LBSs such as routing navigation, location check-in and field analysis. However, the indoor LBSs equivalents, e.g., routing the visually-impaired, are not yet pervasively available due to many unaddressed challenges in indoor positioning system deployments. The overarching goal of this project is to develop practical systems to address such challenges and finally build an Open Global Indoor Positioning System (OGIPS). OGIPS is a supplementation to GPS indoors and the combination of OGIPS and GPS is anticipated to provide truly global positioning services to virtually anyone. The Wi-Fi Positioning System (WPS) is a dominant enabling technology of OGIPS for its sheer prevalence in pervasiveness, reliability and performance. This doctoral study project identified three major challenges for building OGIPS based on WPSs and proposed corresponding solutions. The first challenge is how to deploy WPSs with zero cost. WPS deployment requires Radio Map calibration, which, in current industrial practice, relies on high-cost scene analysis. To reduce the deployment cost, it is possible to leverage the free Crowdsourced data. In fact, an enormous amount of Wi-Fi signal measurements could be collected by Implicit Crowdsourcing, that is, collecting unlabeled data in an unobtrusive manner during normal courses of the smartphone users, e.g., strolling around shopping malls. The challenges is then reformulated as how to perform Radio Map calibration via Implicit Crowdsourcing. This project formulates the targeted problem with a novel Hyper-Graph Matching framework, which lends various merits to the system in terms of scalability, extendability and robustness. The elegant problem formulation allows the system to exploit the accomplishments of Graph Matching researches in the past decades, especially in Computer vision. We designed, implemented the system, HyperLoc, and validated it with extensive experiments with both simulated and real-world data. Experimental results indicates that HyperLoc is able to construct zero-cost WPSs in real-world settings. The overall positioning performance of HyperLoc, a zero-cost system, is comparable to high-cost manually-calibrated WPSs . To our knowledge, HyperLoc is the first work to apply Graph Matching techniques to Radio Map calibrations and the first work that develops a practical and scalable zero-cost WPS implementation in real-world settings. The second challenge is how to maintain WPSs performance over time with zero cost. The Radio Map describes the signal environment in relation to the physical environment of a venue. However, the relation often changes substantially upon changes of radio propagation patterns, caused by many factors, e.g., change of the layout of the venue. To maintain consistent and reliable performance, Radio Maps must be versionized and re-calibrated. Here we arrive at the second challenge, that is, how to effectively manage Radio Map versioning with zero cost. This project proposed a novel Radio Map versioning control system, RAEDS, by detecting system anomalous events that degrade indoor positioning performance substantially. The system generalizes arbitrary Radio Map degrading factors as Radio Map anomalous events, which could be modeled and hence detected using state-of-the-art event detection techniques. We designed, implemented and evaluated RAEDS with both synthetic and real-world experiments. The results showed that RAEDS is able to detect anomalous events accurately with a low false alarm rate. To our knowledge, RAEDS is the first work to apply advanced event detection techniques in WPS health monitoring for system versioning control. The combination of HyperLoc and RAEDS is anticipated to enable a practical zero-cost WPS in real-world settings. However, many challenges still present. The OGIPS architecture shall be carefully designed to accommodate the domain-specific requirements of OGIPS in addition to the general requirements of highly-available and scalable systems. Hence the third challenge is how to architect OGIPS to meet the desired requirements. Practical design goals are discussed comprehensively and a proposed design of the architecture and implementations is described in details. Guidelines and recommendations in system implementations were made. More importantly, the proposed OGIPS design is orthogonal to HyperLoc and RAEDS. That means OGIPS is able to flexibly integrate other zero-cost WPSs implementations at high-level. This merit allows other researchers to reuse the proposed architecture with their proprietary zero-cost WPS implementations. The proposed solutions in this work are expected to pave the path towards building OGIPS in real-world settings. Future research efforts will be devoted to improving the adaptiveness and robustness of the proposed systems in terms of device heterogeneity, adaptiveness to user patterns and insufficient data. Finally, the findings of this thesis are expected to contribute to the research communities sharing the same conviction, that is, to make the indoor positioning service accessible to virtually anyone, anytime and anywhere.

Large numbers of installed medium or high voltage power cables are now of advanced age and have gradual insulation deterioration problems. On-line Partial Discharge (PD) measurement has inherent advantages over the conventional off-line measurement, but it also suffers from a very significant Electro-Magnetic Interference (EMI) problem due to the small PD signal levels being monitored. The large magnitude EMI signal often completely swamps the smaller magnitude PD signal, making it difficult to monitor anything but extremely large PD activity. To monitor cable condition and to be able to assess insulation degradation trends requires advanced techniques. In this thesis, the issues of sensor selection, digital filtering, software based on-line differential technique and wavelet Transform (WT) de-noising techniques are studied. Their applicability, advantages and limitations are discussed with the simulation and high voltage measurement results. The High Frequency Current Transformer (HFCT) type PD sensor is selected after being compared with other sensor in term of sensitivity, universal applicability, frequency response and the installation difficulty. The sinusoidal noise frequency identification and application of the conventional digital filtering are studied. The Least Mean Square (LMS) and Recursive Least Square (RLS) algorithm digital adaptive filters are compared in detail and RLS adaptive filter is selected. Wavelet transform de-noising technique for on-line PD measurement is carefully studied and the applications of noise reduction are developed. A novel WT threshold value selection algorithm is presented in this thesis. The new WT algorithm is compared with the existing wavelet techniques using numerical simulation and laboratory high voltage testing data on cables. The results show that this new fully automatic WT de-noising method has achieved great progress with the capability of detection 30 pC PD signal during on-site on-line measurement where typical noise level is ten times higher in magnitude. On the basis of traditional off-line differential or balanced detection circuit, a software based on-line differential technique is proposed in this thesis. The novel method developed has the capability to process one whole AC cycle of PD data. It enables traditional q-?? and n-?? distributions to be obtained as well as PD repetition rates and the usual integrated PD parameters. These techniques are developed for the on-site on-line PD measurement in power cables, but they are not limited to cables. They can also be applied to other high voltage equipment with minor or without modification in the data acquisition procedure.

Thesis (M.Eng.)--University of Louisville, 2007. / Title and description from thesis home page (viewed December 14, 2007). Department of Computer Engineering and Computer Science. "September 2007." Includes bibliographical references (p. 74-76).

<p>This thesis examines the possibility of installing a wireless communication system based on multiple antennas, on an Unmanned Aerial Vehicle (UAV). The communication system is based on MIMO technology. This technology uses the fact that we can make use of several antennas at the transmitter and the receiver to create independent signal path which in turn can increase the roboustness of the communication link. Advantages and disadvantages of this new system arediscussed. However, this report concludes that the benefits of MIMO outweights the disadvantages.</p><p>Furthermore a simulation environment for the MIMO system is designed and implemented, based on a specific scenario. Moreover, the results from the simulation also points to a benefit of the MIMO technology.</p>

<p>Quality of Service is a set of mechanisms created for differentiating users and data flows. Provisioning the QoS in service provider networks is always interesting for their business departments for they can offer and sell diverse services and to make more money. This thesis QoS for DSL subscribers of Pardis Online - the private ISP in Iran. The size of the network, the certain network connectivity limitations the ISP has in addition to the complexity of the services it provides, necessitate a comprehensive study to elucidate the different service types and requirements and then choosing a specific implementation of QoS in order to meet the ISP’s need. The internet bandwidth in the region that ISP operates is very expensive and the users suffer from the lack of bandwidth so the limited internet links are usually congested in the network. This document concludes with proposing a layered QoS that guarantees that the total bandwidth of an area in congested times is distributed to the users in that area proportionate to the subscribed band width. The resulting proposals are tested in the Lab and their performance under the simulated traffic is monitored and analyzed.</p>

<p>The up growing wireless communication field always need such a system which is simple but more reliable for multiple applications. To fulfill these demands the modern receiver RF frontend can play an important role. A successful design could be a better solution, not only simple but also modern receiver architecture topology is necessary.The main objective of this dissertation is to design a simple RF-Front end for both multi-band multi-systems Global Navigation Satellite System (GNSS i.e. GPS and Galileo) receiver which</p><p>will provide civil signals on multiple frequencies, similar to those currently available for only military purpose and finally implement and test the receiver front end. Different topologies have been investigated and finally the direct digitization RF front end receiver topology is chosen for simplicity, cost and performance. The entire RF front receiver consists of a broad band LNA, a broad band pass filter and a band stop filter. This kind of receiver needs a minimum feasible sampling frequency which is 434 MHz for designed methodology.A simple receiver RF front end for GNSS application is designed to demonstrate and it has been implemented and tested. The receiver is yield the minimum power consumption which is 26mA</p><p>current from 3V power supply.Although, there are no such a specifications for combined future GPS/Galileo receiver, the</p><p>simple design performance is satisfactory and it will be an interesting future work from commercial point of view.</p>

<p>Abstract</p><p>The rapid development within the field of measurement methods and techniques and software design that has taken place over the last years offers new possibilities for designers of measurement systems through the use of virtual instruments as building blocks. The concept of virtual instrumentation is developed within the interchangeable virtual instrument foundation. A closely related term is “synthetic instruments”, which is often used for essentially the same concept, but it is even more software oriented. Synthetic instruments as a research field are in an initial stage and a quick search on “Synthetic instruments” in Institute of Electrical and Electronics Engineers (IEEE) explorer match close to 30 documents. IEEE explorer is a database that provides full-text access to IEEE transactions, journals, magazines and conference proceedings, and all current IEEE Standards.</p><p>This Master Thesis is a theoretical work extracted from study material, IEEE documents and web-resources referenced. The work gives the reader an overview of the Synthetic Instruments and their functionality with respect to hardware and software. The papers were analyzed based upon the various trends in the research, development and productizing phases.</p><p>For this approach; kernel architecture of an ideal synthetic instrument has been introduced as a prototype around which current technologies and applications can be addressed. The major areas of focus in the architecture are the data conversion and signal conditioning; the knowledge of its working under current implemented technologies has been highlighted and discussed in regards to the software and hardware trends. The defense industry holds the major influence.</p><p>The work was aimed towards giving a state-of-the art introduction to synthetic instrument technology; also in order to provide the work an introductory nature, only one hardware & software example has been discussed.</p>

<p>Optical Packet Switching (OPS) has emerged as a promising candidate for the next-generation Wavelength Division Multiplexed (WDM) based alloptical network. By enabling packet switching in the optical domain, OPS networks can provide cost-efficient and transparent transport services to higher layers. However, a commercial deployment of OPS requires not only a maturation of several key enabling technologies, but also a thorough investigation of a number of networking challenges related to OPS, since OPS networks are fundamentally different from today’s store-and-forward networks. This thesis addresses the latter issue by considering the following three OPS networking issues:</p><p>· Quality of Service (QoS) differentiation at the WDM layer, with focus on packet loss rate (PLR) and delay-jitter differentiation.</p><p>· Teletraffic analysis of OPS networks.</p><p>· How to combat packet loss in OPS networks by using network layer packet redundancy.</p><p>First, a crucial issue in OPS networks is packet loss at the network layer due to contention. Contention occurs when a packet is destined for a wavelength currently occupied by another packet. Several approaches to combat such packet loss have been proposed in recent literature, e.g. by utilizing wavelength conversion, buffering, deflection routing or traffic shaping.</p><p>This thesis considers a novel approach to combat packet loss in OPS: The proposed Network Layer Packet Redundancy Scheme (NLPRS) allows redundancy packets to be injected into the OPS network, thus enabling reconstruction of lost data packets at the OPS egress node. Results show that the NLPRS is able to reduce the end-to-end data PLR several orders of magnitude in an asynchronous OPS ring network with and without wavelength conversion.</p><p>Another crucial issue in OPS networks is QoS differentiation at the WDM layer. Due to the lack of optical random access memory, existing QoS differentiation schemes suitable for today’s WDM point-to-point architecture are not feasible to use in OPS networks. Hence, new schemes that utilize the WDM layer to provide QoS differentiation are needed.</p><p>A preemption based QoS differentiation scheme, the Preemptive Drop Policy (PDP), has been proposed for asynchronous bufferless OPS. With the PDP, high priority arrivals are allowed to preempt and take over a busy wavelength currently occupied by a low priority packet in the case of contention. This results in a lower PLR for high priority traffic compared to low priority traffic. The PDP has been extended into the Adaptive PDP (APDP), which provides absolute guarantees to the PLR for high priority ivtraffic in OPS by using a measurement based preemption probability parameter adjustment.</p><p>An access-restriction based QoS differentiation scheme, the Wavelength Allocation algorithm (WA), has been studied. In the WA, which provides QoS differentiation in asynchronous bufferless OPS networks with full range output wavelength converters, a certain number of wavelengths at an output fibre are exclusively reserved for high priority traffic.</p><p>When QoS differentiation (with respect to the PLR) is introduced in asynchronous OPS, it has been shown that the average throughput decreases, often referred to as the throughput penalty of introducing QoS differentiation. The main cause for this throughput penalty is because network resources must be used in a non-optimal manner when employing QoS differentiation schemes that utilize the WDM layer to isolate the service classes. However, as shown in this thesis, the throughput penalty is only found in asynchronous OPS. For slotted OPS, the average throughput stays the same after the introduction of QoS differentiation.</p><p>An evaluation framework suitable for quantifying the throughput penalty when introducing QoS differentiation has been proposed. Using this framework, three fundamental different QoS differentiation schemes for asynchronous OPS, including the PDP and the WA, have been evaluated. It has been shown that preemptive techniques result in the lowest throughput penalty, followed by access-restriction and dropping based techniques. This is because, when using preemption, packets are dropped only when the output port is congested. With access-restriction, packets are dropped when the output port is highly strained, and with statistically packet dropping, packets are dropped independently of the state of the output port.</p><p>A QoS differentiation scheme for slotted OPS has been proposed and evaluated. The scheme isolates the service classes by ensuring that a certain number of high priority packets can be transmitted at an output port in a time-slot in the case of contention. Using the proposed scheme does not result in a reduced throughput when the service classes are isolated.</p><p>QoS differentiation schemes for asynchronous OPS with a share pernode (SPN) contention resolution pool architecture consisting of Tunable Wavelength Converters (TWCs) and Fibre Delay Lines (FDLs) have been proposed. In particular, it has been shown that the PLR and delay-jitter may be independently differentiated in this switch architecture.</p><p>Analytical models of some of the proposed QoS differentiation schemes have been derived, providing explicit results of the PLR. In addition, an analytical framework regarding packet arrivals to an output port in an optical packet switch has been derived for both asynchronous and slotted OPS. This framework is particularly useful for studying the effects of nonuniform traffic. Furthermore, it has been shown that both the Erlang and Engset traffic models are suitable to model packet arrivals to an output port in an asynchronous optical packet switch. Regarding the Engset traffic model, it has been shown how the blocking probability can be evaluated vusing either the Engset lost calls cleared (LCC) traffic model or the Engset overflow (OFL) traffic model. For all Engset based traffic models, the time-, call- and traffic congestion have been derived. A numerical evaluation of the presented traffic models reveals that there is a small, but non-negligible, deviation between the observed blocking probabilities, which depends on the number of input/output fibres and the system load.</p>

In recent years, high speed data communications over twisted pair cables has gained tremendous demand. Asymmetric Digital Subscriber Line (ADSL) was standardized for use over twisted pair cables. A critical component in ADSL system is the echo canceller which is intended to discriminate unwanted echo signals caused by twisted pair interface circuit called the hybrid. An echo signal is characterized by the hybrid and the line type the hybrid is connected to. Recently, there has been a great concern that the echo signal displays wide variations when the twisted pair cable is shared with a telephone. The amount of echo signal present in the receiver will directly influence the ADSL system performance. Hence, high performance echo canceller with good tracking capability is required. In this thesis, a new adaptation scheme called Modified Conjugate Gradient method is proposed and applied to ADSL echo canceller. It is shown that superior tracking capability is obtained compared to previously proposed echo canceller using Least Mean Square (LMS) method while compromising small amount of computational complexity. / Graduation date: 1999

Thesis (Ph.D.)--Hong Kong University of Science and Technology, 2007. / Includes bibliographical references (leaves 112-118). Also available in electronic version.