not available until OCRd / Master of Science

In recent years, the rapid growth in wireless data traffic has posed not only unique opportunities but also great challenges for the wireless industry. In order to meet the growing demand without excessive cost or energy consumption, one feasible option for the operators is to acquire more spectrum for wireless communication. Unlike the lengthy allocation process for exclusive spectrum licenses, secondary spectrum access is deemed as a flexible alternative to obtain additional spectrum at low cost. In particular, the VHF/UHF TV band, so called ’TV White Space’, is considered as the most promising candidate for secondary access thanks to its well defined primary usage and favorable propagation characteristic for building penetration and wide area coverage. Therefore, secondary access in the TV band has been extensively studied by both academic and industry. Most of the research have focused on the detection of ’spectrum holes’ with sensing technologies, while a few others have provided high level analysis of the potential of TV white space with simplistic secondary interference model for single secondary user. Only A limited number of studies have investigated aggregate interference from multiple secondary users, but even these studies have ignored the adjacent channel interference from secondary users close to the TV receivers. Thus, in this thesis we first concentrate on examining the effect of harmful interference on TV reception from short range devices transmitting on adjacent channels, and model the accumulative effect of multi-channel interferences observed in the measurement. Then the basic methodology for evaluating the potential of TV white space is developed in the second part of the thesis, where we propose a new analytical approach for regulating the secondary transmit power that significantly outperforms the existing method in the regulatory framework. Finally, we combine the aggregate interference model and the basic regulation methodology to extend the analysis from single user to multiple user case, first with only users transmitting on different adjacent TV channels and later also including users transmitting on co-channels. Our performance evaluation have shown that the effect of adjacent channel interference at close distance is far from negligible and the accumulative effect of multi-channel interferences has substantial impact on the scalability of a secondary system. In fact, the adjacent channel interference proves to be the primary limiting factor of the TV white space availability for low power short range systems. Nonetheless, because the proposed approach can adapt to varying environmental conditions and consequently utilize the spectrum reuse opportunity more efficiently than existing frameworks, we can still note considerable amount of TV white space available for short range secondary devices. / <p>QC 20121106</p> / QUASAR

Distributed control applications enabled by wireless networks are becoming more and more frequent. The advantages of wireless access are many, as control systems become mobile, autonomous and connected. Examples include platooning and automated factories. However, distributed control systems have stringent requirement on both reliability and timeliness, the latter in terms of deadlines. If the deadline is missed, the packet is considered useless, similarly to a lost or erroneous packet in a system without deadlines. In addition, wireless channels are, by nature, more exposed to noise and interference than their wired counterparts. Consequently, it implies a considerable challenge to fulfill the deadline requirements with sufficient reliability for proper functionality of distributed control applications. However, by taking advantage of cooperative communications, increased reliability can be achieved with little or no additional delay. Reducing the delay until a message is successfully received is a two-fold problem: providing channel access with a predictable maximum delay and maximizing the reliability of each transmission, once granted by the medium access method. To this end, this thesis proposes a framework that provides a bounded channel access delay and handles the co-existence of both time-triggered and event-driven messages encountered in distributed control applications. In addition, the thesis proposes and evaluates an efficient message dissemination technique based on relaying that maximizes the reliability given a certain deadline, or alternatively determines the delay required to achieve a certain reliability threshold for both unicast and broadcast scenarios. Numerical results, which are verified by Monte-Carlo simulations, show significant improvements with the proposed relaying scheme as compared to a conventional scheme without cooperation, providing more reliable message delivery given a fixed number of available time-slots. It also becomes clear in which situations relaying is preferable and in which situations pure retransmissions are preferable, as the relay selection algorithm will always pick the best option. The relay selection algorithm has a reasonable complexity and can be used by both routing algorithms and relaying scenarios in any time-critical application as long as it is used together with a framework that enables predictable channel access. In addition, it can be implemented on top of commercially available transceivers. / ACDC

User demand for faster access to more data is at a historic high and rising. One of the enabling technologies that makes the information age possible is fiber-optic communications, where light is used to carry information from one place to another over optical fiber. Since the technology was first shown to be feasible in the 1970s, it has been constantly evolving with each new generation of fiber-optic systems achieving higher data rates than its predecessor. Today, the most promising approach for further increasing data rates is digital signal processing (DSP)-based coherent optical transmission with multi-level modulation. As multi-level modulation formats are very susceptible to noise and distortions, forward error correction (FEC) is typically used in such systems. However, FEC has traditionally been designed for additive white Gaussian noise (AWGN) channels, whereas fiber-optic systems also have other impairments. For example, there is relatively high phase noise (PN) from the transmitter and local oscillator (LO) lasers. The contributions of this thesis are in two areas. First, we use a unified approach to analyze theoretical performance limits of coherent optical receivers and microwave receivers, in terms of signal-to-noise ratio (SNR) and bit error rate (BER). By using our general framework, we directly compare the performance of ten coherent optical receiver architectures and five microwave receiver architectures. In addition, we put previous publications into context, and identify areas of agreement and disagreement between them. Second, we propose straightforward methods to select codes for systems with PN. We focus on Bose-Chaudhuri-Hocquenghem (BCH) codes with simple implementations, which correct pre-FEC BERs around 10−3. Our methods are semi-analytical, and need only short pre-FEC simulations to estimate error statistics. We propose statistical models that can be parameterized based on those estimates. Codes can be selected analytically based on our models. / <p>QC 20150528</p>

A Geographic Information System (GIS) viewshed is the result of a function that determines, given a terrain model, which areas on a map can be seen from a given point(s), line or area. In the communications industry, this function has been used to model radio wave coverages and to site transceiver towers for cellular phones. However, there are errors involved with this function and, without the requisite data, it cannot account for building heights that may affect visibility in urban areas. This paper examines the ability to accurately show line-of-sight (LOS) radio wave coverages in order to establish the viability of replacing existing field methods with GIS viewshed analysis. An origin point capable of supporting a line-of-sight radio wave transmitter was chosen from within the Virginia Tech campus study area. A viewshed analysis was performed with ESRI's ArcView GIS, using this site as the observation point and a 30-meter resolution Digital Elevation Model (DEM) from the US Geological Survey. To check the accuracy of the viewshed, we transmitted at 27.5 GHz, a LOS frequency that has properties common in the wireless telecommunications industry. We also transmitted at 900 MHz from the same point to provide a comparison of the 27.5 GHz frequency to a non-line-of-sight radio wave.The data was recorded and then entered into the GIS where the visibility attribute of each point was compared to the viewshed's prediction of visibility. After this comparison, footprints and heights of campus buildings were included in the model, by adding them to the ground heights of the DEM. Another viewshed analysis was performed using the same origin site and the new building height DEM as the elevation grid. This second viewshed was compared with the recorded visibility attribute and signal strength data. The use of more complete surface data was shown to have a more positive correlation with the recorded data than the previous model. The comparison of these two viewsheds demonstrated how well the viewshed function can represent real-world visibility and showed that the accuracy of the viewshed function is dependent on the accuracy of the elevation model. The signal strength attribute enabled us to create a communications viewshed, or 'commshed'. The commshed consists of all data points that received a signal strong enough to carry data. The building viewshed and commshed were then compared to see to what degree the 27.5 GHz frequency deviates from true line-of-sight paths. There were slightly fewer points in the commshed than points 'in view' in the viewshed model due to the frequency's small wavelength and the lack of vegetation data in the elevation grid. However, when a power margin is added to the transmitter strength in order to overcome unpredictable conditions, the commshed's predictive accuracy increases as well. This means that for LOS radio systems running under normal operating conditions, the viewshed is an excellent predictor of receiving areas. A 900 MHz commshed was also created so that we could study the relationship between a line-of-sight radio wave and a wave that is not blocked by structures. This comparison showed that, as expected, a viewshed is a better predictor of LOS radio waves than non-LOS waves. The data sets and analysis presented here should help communications companies ascertain the best way to incorporate GIS and the viewshed function into their wave coverage mapping and tower siting processes. / Master of Science

No description available.

International Telemetering Conference Proceedings / October 20-23, 2003 / Riviera Hotel and Convention Center, Las Vegas, Nevada / Test and training ranges have sought the holy grail of large-scale range interconnectivity for many years. The ability to test at any range and transmit the information to the engineers at the home base and control the mission without sending the entire test team to a remote location improves the test schedules, reduces the cost of testing and improves the testing capabilities. New opportunities of interconnecting ranges are changing the business of open air range testing and the resulting capabilities. Two predominant opportunities will be discussed in this paper. First, is taking advantage of the fiber glut that the US is currently experiencing along with opportunities for government-acquired assets to service the testing community. This approach provides the government the ability to fiber-optically create a virtual test range and provide full interconnectivity of all data. Second is to take advantage of the existing networks such as the Defense Research Engineering Network (DREN) to make efficient on-demand type connectivity where, otherwise, it would be cost prohibitive.

Abstract The impact of technology has been rapidly changing the economy and environment in these past two decades. Both manufacturing and service companies which intend to maintain the viability of their organizations have to adapt in such an environment. For a long time, services have been perceived as being technologically backward and to take little initiative with respect to innovate. In general services were presumed to be laggards in adopting new technology, and to be largely passive adopter of major innovations; however, it was recognized that there are some exceptionally dynamic services – such as telecommunications. Service sector firms play important roles in innovation, not the least in the creative use and diffusion of technologies; but also serve as important sources and agents for the transfer of technological and organizational knowledge to all sectors. In innovation, knowledge plays a big role in gaining competitive advantage. There is a more fundamental need to understand how organizations create new knowledge in order to produce new products or services. Hence, the need – organizational knowledge – is growing in this turbulent economy of accelerated technological change. To create knowledge in an organization usually lies in an individual’s knowledge. This is called as tacit knowledge and is a significant point to innovate. Nonaka and Takeuchi (1995) had pointed out that an individual knowledge gets articulated and amplified into and throughout the organization. Moreover, there is a one way to bring about continuous innovation is to look outside and into the future, anticipating changes in the market, technology, competition, or product. The service sectors have been innovating gradually in Indonesia and Taiwan, particular in telecommunications after liberalized. In 2002, the Indonesia’s economy grew 3.66 percent from the previous year which the highest growth occurring in the transportation and communication sectors by 7.83 percent. In addition, the telecoms sector in Taiwan will contribute 63.1 billion new Taiwan dollars (1.9 billion US dollars) to Taiwan’s GDP annually over the next five years when the telecommunication market is fully liberalized. In this study will discuss about the innovation of cellular telecommunication services in Indonesia and Taiwan. By analyzing the service innovation process in MMS and Video Streaming from Indosat and Chunghwa, to figure out: 1. Where the new innovation concept comes from; 2. How they define theirs customer interface; and 3. How they develop theirs employees’ skills to deliver service. We also examine the linking between the company background and innovation. This could be their establishment time, objectives, macro economy point of view, and so on. It might be crucial points to encourage them to innovate. Key Words: service innovation, telecommunications service, innovation process / The impact of technology has been rapidly changing the economy and environment in these past two decades. Both manufacturing and service companies which intend to maintain the viability of their organizations have to adapt in such an environment. For a long time, services have been perceived as being technologically backward and to take little initiative with respect to innovate. In general services were presumed to be laggards in adopting new technology, and to be largely passive adopter of major innovations; however, it was recognized that there are some exceptionally dynamic services – such as telecommunications. Service sector firms play important roles in innovation, not the least in the creative use and diffusion of technologies; but also serve as important sources and agents for the transfer of technological and organizational knowledge to all sectors. In innovation, knowledge plays a big role in gaining competitive advantage. There is a more fundamental need to understand how organizations create new knowledge in order to produce new products or services. Hence, the need – organizational knowledge – is growing in this turbulent economy of accelerated technological change. To create knowledge in an organization usually lies in an individual’s knowledge. This is called as tacit knowledge and is a significant point to innovate. Nonaka and Takeuchi (1995) had pointed out that an individual knowledge gets articulated and amplified into and throughout the organization. Moreover, there is a one way to bring about continuous innovation is to look outside and into the future, anticipating changes in the market, technology, competition, or product. The service sectors have been innovating gradually in Indonesia and Taiwan, particular in telecommunications after liberalized. In 2002, the Indonesia’s economy grew 3.66 percent from the previous year which the highest growth occurring in the transportation and communication sectors by 7.83 percent. In addition, the telecoms sector in Taiwan will contribute 63.1 billion new Taiwan dollars (1.9 billion US dollars) to Taiwan’s GDP annually over the next five years when the telecommunication market is fully liberalized. In this study will discuss about the innovation of cellular telecommunication services in Indonesia and Taiwan. By analyzing the service innovation process in MMS and Video Streaming from Indosat and Chunghwa, to figure out: 1. Where the new innovation concept comes from; 2. How they define theirs customer interface; and 3. How they develop theirs employees’ skills to deliver service. We also examine the linking between the company background and innovation. This could be their establishment time, objectives, macro economy point of view, and so on. It might be crucial points to encourage them to innovate. Key Words: service innovation, telecommunications service, innovation process

Telecommunication sector is one of the most developing in last 20 years. The speed of the progress in inventing new technologies has to be balanced by proper radio spectrum management since radio spectrum is a scarce resource. The methods of assignment used in past such as beauty contests or lotteries are no longer those that rule the sector. To keep pace with new technologies, spectrum auctions were presented as a new method that ensures the best results for state. Since the companies are competing for the licenses, final price is getting higher and thereby higher revenues go to the state treasury. In this thesis the behavior of final price in the spectrum auctions was examined. In the end of the work, recommendations to NRAs were presented to conclude the results of the empirical examination. Powered by TCPDF (www.tcpdf.org)

The purpose of this study was to explore salient issues in the Ethiopian telecommunications sector. In doing so, the research investigated the institutional history and origins of state-monopoly of telecommunications in Ethiopia from the first ministerial level communications-related institution, the Ministry of Posts, Telegraph and Telephone, to Ethio-Telecom presently. Using a theoretical framework informed by political economy of communications, development studies and political science, the study explored the foundations, rationales and implications of contesting ideologies in the Ethiopian telecommunications sector involving the Ethiopian state and the International Monetary Fund (IMF). The study also explored the extent to which, and why, the Ethiopian public endorses/denounces state monopoly of the telecommunications sector. It also investigated the premises on which Sino-Ethiopian partnerships in the Ethiopian telecommunications sector are laid. A triangulated, multi-method research approach involving document analysis, online survey and semi-structured interviewing was employed in this study. World Bank documents and other secondary resources were analyzed to chronicle the institutional history of telecommunications in Ethiopia. IMF reports and Ethiopian People's Revolutionary Democratic Front economic programs and political manifestos were carefully examined to address contesting liberalization discourses pertinent to the Ethiopian telecommunications sector. An online survey was administered to collect public opinion about, among other things, state monopoly of telecommunications in Ethiopia. Ethiopian government officials, IMF country representatives, Ethio-Telecom consultants and other important figures were interviewed to explore the pros and cons of Sino-Ethiopian relations in the Ethiopian telecommunications sector as well. The study revealed that a host of different factors, most notably the rise of China as an alternative global economic power, have shifted Ethiopia's preference of global development partnership from West to East including in telecommunications infrastructure development. Growing concerns over state monopoly of telecommunications were reported by users, particularly in relation to lack of quality of services and fear of surveillance. / 2015-03-29