The topic of Wi-Fi networks (Wireless Fidelity) is widely discussed currently as there is a big boom of this technology. The Wi-Fi refers to a method of modern technology that enables wireless transmission of data between devices such as printers and mobile phones. The main objectives of the thesis are focused on the development proposal to build a modern data network for an ISP (Internet Service Provider) in the technical area. Another aim was to process and analyze the results of the newly formed economic entity and their subsequent evaluation in recent years, i.e for the years 2008 - 2011. Business plan was designed in Branišov, which is a village near Czech Budejovice in 2001. Initially, it was the agreement of two local residents who believed that the offer of an Internet connection is not ideal for this location and started to develop some "small" wireless network. At the beginning, any professional equipment was not used in this network. When connected with an increasing number of customers (about five inhabitants of Branišov), professional antennas and access points began to be used. The above mentioned five customers manage to cover all operating costs created by the network. In subsequent years, i.e. 2004 ? 2007, there was a boom of the project. The number of connected users was growing constantly, even though not conducted any marketing or promotional activities. By the end of 2006, individual users began to demand greater guarantee of a stable connection. At the same time, it also proved to be absolutely necessary to establish a specific person responsible for the network. This person was supposed to maintain the network, develop it and manage it. In 2007, the initial non-commercial network was transformed into a commercial network model and brand new commercial entity ? a limited liability company ? was created. Currently, there is a continual development of this network, which already covers a total of 30 villages around České Budějovice and Vodňany and the signal spread through 115 broadcasting Access Points.

ZigBee based Wireless Sensor Networks (WSN) and Wireless Local Area Networks (WLAN) utilize the same un-licensed 2.4GHz frequency band. In our research, it is noticed that ZigBee could suffer serious performance degradation due to the collocated WLAN interference. After going through the available literature and combining with a thorough statistical analysis of our experimental results, several important factors that severely impact the ZigBee packet transmission performance have been identified. Motivated by these findings, novel techniques are designed to improve the performance of ZigBee packet transmission under WLAN interference. ACK with Interference Detection (ACK-ID) technique is developed to improve the delivery rate of ACK packets, and consequently reduce the number of redundant retransmissions. In order to improve the energy efficiency, Adaptive Transmit Power Adjustment (ATPA) is proposed to adaptively adjust the optimal transmit power while maintaining the predefined Packet Loss Rate (PLR) requirement. Time Aware Backoff and Transmission (TABTx) technique controls the time spent on each packet transmission attempt so as to avoid the Transmit First In First Out Byte Register (TXFIFO) overflow. Adaptive Preamble Padding with Retransmission Control (APPRC) is proposed to improve the transmission efficiency while satisfying the PLR requirement by determining the appropriate number of protective preamble padding bytes and whether or not to adopt packet retransmission. All these novel techniques have been implemented in the Crossbow MICAz motes and evaluated through extensive experimental measurements in the testbed.

Hybrid Networks employing wireless communication technologies have nowadays brought closer the vision of communication “anywhere, any time with anyone”. Such communication technologies consist of various standards, protocols, architectures, characteristics, models, devices, modulation and coding techniques. All these different technologies naturally may share some common characteristics, but there are also many important differences. New advances in these technologies are emerging very rapidly, with the advent of new models, characteristics, protocols and architectures. This rapid evolution imposes many challenges and issues to be addressed, and of particular importance are the interoperability issues of the following wireless technologies: Wireless Fidelity (Wi-Fi) IEEE802.11, Worldwide Interoperability for Microwave Access (WiMAX) IEEE 802.16, Single Channel per Carrier (SCPC), Digital Video Broadcasting of Satellite (DVB-S/DVB-S2), and Digital Video Broadcasting Return Channel through Satellite (DVB-RCS). Due to the differences amongst wireless technologies, these technologies do not generally interoperate easily with each other because of various interoperability and Quality of Service (QoS) issues. The aim of this study is to assess and investigate end-to-end interoperability issues and QoS requirements, such as bandwidth, delays, jitter, latency, packet loss, throughput, TCP performance, UDP performance, unicast and multicast services and availability, on hybrid wireless communication networks (employing both satellite broadband and terrestrial wireless technologies). The thesis provides an introduction to wireless communication technologies followed by a review of previous research studies on Hybrid Networks (both satellite and terrestrial wireless technologies, particularly Wi-Fi, WiMAX, DVB-RCS, and SCPC). Previous studies have discussed Wi-Fi, WiMAX, DVB-RCS, SCPC and 3G technologies and their standards as well as their properties and characteristics, such as operating frequency, bandwidth, data rate, basic configuration, coverage, power, interference, social issues, security problems, physical and MAC layer design and development issues. Although some previous studies provide valuable contributions to this area of research, they are limited to link layer characteristics, TCP performance, delay, bandwidth, capacity, data rate, and throughput. None of the studies cover all aspects of end-to-end interoperability issues and QoS requirements; such as bandwidth, delay, jitter, latency, packet loss, link performance, TCP and UDP performance, unicast and multicast performance, at end-to-end level, on Hybrid wireless networks. Interoperability issues are discussed in detail and a comparison of the different technologies and protocols was done using appropriate testing tools, assessing various performance measures including: bandwidth, delay, jitter, latency, packet loss, throughput and availability testing. The standards, protocol suite/ models and architectures for Wi-Fi, WiMAX, DVB-RCS, SCPC, alongside with different platforms and applications, are discussed and compared. Using a robust approach, which includes a new testing methodology and a generic test plan, the testing was conducted using various realistic test scenarios on real networks, comprising variable numbers and types of nodes. The data, traces, packets, and files were captured from various live scenarios and sites. The test results were analysed in order to measure and compare the characteristics of wireless technologies, devices, protocols and applications. The motivation of this research is to study all the end-to-end interoperability issues and Quality of Service requirements for rapidly growing Hybrid Networks in a comprehensive and systematic way. The significance of this research is that it is based on a comprehensive and systematic investigation of issues and facts, instead of hypothetical ideas/scenarios or simulations, which informed the design of a test methodology for empirical data gathering by real network testing, suitable for the measurement of hybrid network single-link or end-to-end issues using proven test tools. This systematic investigation of the issues encompasses an extensive series of tests measuring delay, jitter, packet loss, bandwidth, throughput, availability, performance of audio and video session, multicast and unicast performance, and stress testing. This testing covers most common test scenarios in hybrid networks and gives recommendations in achieving good end-to-end interoperability and QoS in hybrid networks. Contributions of study include the identification of gaps in the research, a description of interoperability issues, a comparison of most common test tools, the development of a generic test plan, a new testing process and methodology, analysis and network design recommendations for end-to-end interoperability issues and QoS requirements. This covers the complete cycle of this research. It is found that UDP is more suitable for hybrid wireless network as compared to TCP, particularly for the demanding applications considered, since TCP presents significant problems for multimedia and live traffic which requires strict QoS requirements on delay, jitter, packet loss and bandwidth. The main bottleneck for satellite communication is the delay of approximately 600 to 680 ms due to the long distance factor (and the finite speed of light) when communicating over geostationary satellites. The delay and packet loss can be controlled using various methods, such as traffic classification, traffic prioritization, congestion control, buffer management, using delay compensator, protocol compensator, developing automatic request technique, flow scheduling, and bandwidth allocation.

Human populations are at risk of exposure to constitutive androstane receptor (CAR) activators present in a range of substances, including pharmaceuticals, plasticizers and crop protection agents. What exposure to CAR activators means for human health is uncertain. Activation of CAR in rodents is associated with liver hyperplasia, increased proliferation and eventual hepatocarcinoma; however the effect in human hepatic cells is unclear. There are two methods by which a compound can achieve activation of CAR; directly or indirectly via cellular signalling pathways. Phenobarbital is a prototypical activator of CAR and does so in an indirect manner via suppression of epidermal growth factor receptor (EGFR) signalling. Direct activation of CAR in rodents also causes hepatocellular carcinoma but the human outcome is less clear. We have carried out microarray and miRNA analysis of CITCO (a potent and selective hCAR ligand) treated primary human hepatocytes. To mitigate the well documented effect of primary hepatocyte dedifferentiation primary hepatocytes were cultured in dynamic three dimensional culture in vitro. Gene expression changes indicate that direct activation of hCAR causes the promotion of a pro-proliferative and anti-apoptotic phenotype. The miRNA expression profile is crucially different to rodent data that is currently published. Despite the pro-proliferative phenotype shown there is no evidence that primary human hepatocytes proliferate in response to direct activation of CAR by CITCO. This leaves the possibility that a proliferative response may be observed in vivo or that the changes in gene expression are solely a human physiological adaptation to direct hCAR activation by CITCO and no proliferation would occur. The effect on human health and liver toxicity is unclear but this body of work has provided data that may be used to further understand the mechanistic effects of direct hCAR activation in human hepatocytes. A more complete understanding of this will help to inform the toxic potential of direct hCAR activation in vivo.

The beginning of the 21st century sees great development and demands on wireless communication technologies. Wireless technologies, either based on a cable replacement or on a networked environment, penetrate our daily life more rapidly than ever. Low operational power, low cost, small form factor, and function diversity are the crucial requirements for a successful wireless product. The receiver??s front-end circuits play an important role in faithfully recovering the information transmitted through the wireless channel. Bluetooth is a short-range cable replacement wireless technology. A Bluetooth receiver architecture was proposed and designed using a pure CMOS process. The front-end of the receiver consists of a low noise amplifier (LNA) and mixer. The intermediate frequency was chosen to be 2MHz to save battery power and alleviate the low frequency noise problem. A conventional LNA architecture was used for reliability. The mixer is a modified Gilbert-cell using the current bleeding technique to further reduce the low frequency noise. The front-end draws 10 mA current from a 3 V power supply, has a 8.5 dB noise figure, and a voltage gain of 25 dB and -9 dBm IIP3. A front-end for dual-mode receiver is also designed to explore the capability of a multi-standard application. The two standards are IEEE 802.11b and Bluetooth. They work together making the wireless experience more exciting. The front-end is designed using BiCMOS technology and incorporating a direct conversion receiver architecture. A number of circuit techniques are used in the front-end design to achieve optimal results. It consumes 13.6 mA from a 2.5 V power supply with a 5.5 dB noise figure, 33 dB voltage gain and -13 dBm IIP3. Besides the system level contributions, intensive studies were carried out on the development of quality LNA circuits. Based on the multi-gated LNA structure, a CMOS LNA structure using bipolar transistors to provide linearization is proposed. This LNA configuration can achieve comparable linearity to its CMOS multi-gated counterpart and work at a higher frequency with less power consumption. A LNA using an on-chip transformer source degeneration is proposed to realize input impedance matching. The possibility of a dual-band cellular application is studied. Finally, a study on ultra-wide band (UWB) LNA implementation is performed to explore the possibility and capability of CMOS technology on the latest UWB standard for multimedia applications.

The demand of Indoor Location Based Services LBS has increased over the past years as smart phone market expands. As a result, there's a growing interest in developing efficient and reliable indoor positioning systems for mobile devices. Wi-Fi signal strength fingerprint-based approaches attract more and more attention due to the wide deployment of Wi-Fi access points. Indoor positioning problem using Wi-Fi signal fingerprints can be viewed as a machine learning task to be solved mathematically. This thesis proposes an efficient and reliable Wi-Fi real-time indoor positioning system using machine learning algorithms. The proposed positioning system, together with a location server equipped with the same algorithms, are tested and evaluated in several indoor scenarios. Simulation and testing results show that the proposed system is a feasible LBS solution.

The demand of Indoor Location Based Services LBS has increased over the past years as smart phone market expands. As a result, there's a growing interest in developing efficient and reliable indoor positioning systems for mobile devices. Wi-Fi signal strength fingerprint-based approaches attract more and more attention due to the wide deployment of Wi-Fi access points. Indoor positioning problem using Wi-Fi signal fingerprints can be viewed as a machine learning task to be solved mathematically. This thesis proposes an efficient and reliable Wi-Fi real-time indoor positioning system using machine learning algorithms. The proposed positioning system, together with a location server equipped with the same algorithms, are tested and evaluated in several indoor scenarios. Simulation and testing results show that the proposed system is a feasible LBS solution.

Along with the huge growth of mobile devices in recent years we have seen a matching growth in interest for mobile applications, with location-aware applications experiencing rapid growth for mobile devices. Radiolocation from measurements of radio received signal strength has demonstrated excellent precision, although despite a decade of research there have been no wide-spread deployments of indoor location systems. The majority of the existing research has been focused towards producing improved precision at the cost of increased time requirements for system configuration and maintenance. This thesis proposes taking a step back from increasing complexity by giving up precision in exchange for simplicity and speed of deployment, while still providing sufficient accuracy for many indoor location tasks. This is accomplished by putting aside the standard x, y, z coordinate systems and by using a method based on defined areas. Carefully choosing the defined areas to include Wi-Fi access points and to have signal attenuating walls separating the area from the next, this work demonstrates locational accuracy of over 90% in most cases. While this method is not applicable to wide open areas that lack signal attenuating features, it is highly applicable to many indoor environments. / Graduate

Mobile phones are becoming a primary platform for information access. More and more people use their mobile devices as one of their major communication access tools. Commuters are increasingly carrying their mobile devices with them almost everywhere. Mobile devices fit perfectly into an ideal environment for realizing ubiquitous computing. A major aspect of ubiquitous computing is context-aware applications where the applications collect information about the environment that the user is in and use this information to achieve their goals or improve performance. The location of the device is one of the most important pieces of context information. Location awareness makes certain applications possible, e.g., recommending nearby businesses and tracking estimated routes, and greatly improves the performance of other applications, for example it can be associated with automobile navigation devices. A feature available to mobile applications in the Android platform makes it possible to determine a device's location without any additional hardware or sensor mechanisms, by simply using the native capability of the built-in wireless network card. Since the release of Android systems, there have been numerous applications developed to introduce new ways of tracking locations. Recently, there have been many papers on location estimation leveraging ubiquitous wireless networks. In this thesis, we develop an Android application to collect useful Wi-Fi information without registering a location listener with a network-based provider, such as Wi-Fi connections or data connections. Therefore it provides a passive, privacy-preserving, non-intrusive and power-saving way of achieving location awareness to Android mobile users. Accurate estimation of the location information can bring a more contextual experience to mobile users. We save the passively collected data of the IDs of Wi-Fi access points and the received signal strengths to a database in order to help us structure the data and analyse it. We employ some heuristics to infer the location information from the data. Our work presents a location tracking technique mainly based on Basic Service Set identification (BSSID) and/or Received Signal Strength Indicator (RSSI) using Wi-Fi information. It falls into one of the most active fields in mobile application development --location-based or location-aware applications.

Thesis (M.S.)--University of Wisconsin--Stevens Point, 2009 / Submitted in partial fulfillment of the requirements of the degree Master of Science in Natural Resources (Environmental Education and Interpretation), College of Natural Resources. Includes bibliographical references (leaves 148-150).