Thesis (Ph. D.)--Ohio State University, 1974. / Includes bibliographical references (leaves 313-322). Available online via OhioLINK's ETD Center.

Thesis (M.Eng.)--University of Louisville, 2007. / Title and description from thesis home page (viewed May 9, 2007). Department of Computer Engineering and Computer Science. "Spring 2007." Includes bibliographical references (p. 41-42).

Thesis (M.S.)--University of Texas at Dallas, 2008. / Includes vita. Includes bibliographical references (leaves 57-60)

This thesis investigates the performance of free-space optical (FSO) communication systems in a turbulent atmosphere employing optical amplifiers (OAs) to extend transmission reach and wavelength-division multiplexing (WDM) to improve capacity. This system performance is considered in the presence of amplified spontaneous emission (ASE) noise, scintillation, beam spreading, atmospheric attenuation and interchannel crosstalk. In this work, the modulation scheme used is the on-off keying non-return-to-zero and the main performance metric employed is the average bit error rate (BER). Various performance evaluation methods are used to estimate system performance. Analysis of single link, cascaded OA and WDM FSO communication systems are given and the implications of using both adaptive (to channel state) and non-adaptive decision threshold schemes are analysed. The benefits of amplifier saturation, for example in the form of effective scintillation reduction when a non-adaptive decision threshold scheme is utilised at the receiver for different atmospheric turbulence regimes, are presented. Monte Carlo simulation techniques are used to model the probability distributions of system parameters such as the optical signal power, amplified spontaneous emission noise, optical signal to noise ratio and the average bit error rate due to scintillation. It is found that the performance of an adaptive decision threshold is superior to a non-adaptive decision threshold for both saturated and fixed gain preamplified receivers and the ability of a saturated gain OA to suppress scintillation is only meaningful for system performance when a non-adaptive decision threshold is used at the receiver. In a saturated gain preamplified system, the optimum non-adaptive decision threshold is investigated. An OA cascade can be successfully used to extend reach in FSO communication systems and specific system implementations are presented. The optimal cascade scheme with a non-adaptive receiver would use frequent low gain saturated amplification although this has a cost implication. Furthermore, a saturated gain amplified WDM FSO system with a non-adaptive decision threshold is superior to a non-amplified WDM FSO system with an adaptive decision threshold.

The C and Ku bands that have been the backbone of satellite telephony and data networks in the past are limited in the amount of bandwidth they provide. Consequently, some broadband Internet services have started to move into the Ka band in order to utilise the bandwidth at these higher frequencies. The use of higher frequencies led to fade mitigation design considerations that had not previously been necessary, as fixed power margins had been sufficient to guarantee high availability. This thesis reviews the majority of fade mitigation techniques that are available and simulates a scenario with several combined in a hybrid scheme. The simulations were made possible by several innovative components, including a near-optimum short-term fade predictor, a procedure capable of simulating the effect of site diversity with a single time series of attenuation and a dual-channel protocol structure that is able to increase availability of control information at V band. The near-optimum short-term fade predictor is compared with several other short-term fade predictors and is shown to perform better in terms of the root-mean-square error and by the cumulative distribution of over-predictions. Also noteworthy is the fact that predictors based on fade slope perform very poorly when compared with signal processing and statistical methods of prediction. The procedure capable of producing the effects of site diversity on a single time series of attenuation is described. The results of this procedure are compared with the ITU-R model for site diversity improvement and an acceptable fit is shown. A dual-channel protocol structure capable of increasing control information availability at V band is presented and the availability of this scheme is compared to the availability of current fixed-margin C and Ku band satellite links. While the availability at V band improves via this technique, it does not improve enough to compare favourably with that found in the lower frequency bands. A software turbo decoder capable of decoding the DVB-RCS turbo code is also described in this work since this was not available through other means. The fade dynamics at V band are reviewed and compared with the ITU-R models. The fade slope model gives a good visual fit but the fade duration model is very inaccurate. Finally, the simulation results show that high availability satellite communication is possible at V band, critically, if both site diversity and frequency diversity are available to mitigate the hub and VSAT fading respectively. Signal processing and power control are also found to be complementary techniques.

Thesis (Masters Diploma(Technology) - Cape Technikon, Cape Town, 1996 / ESKOM control a massive power grid in a vast geographical area in the R.S.A.. This power originates at the power stations, from where it is distributed to the users. All the power generated is pumped into a National Power Grid. The backbone of the network consists of the following supply voltages: • 765 kV • 400 kV • 132 kV These voltages are stepped down locally at substations to lower voltages for the customers. Bigger customers (e.g. Municipalities, Mines, etc.) are bulk users and use high voltages. Lower voltages range from 220V up to 66kV. In order to ensure a good service to all power user customers ESKOM must be able to identify power failures and other abnormal conditions as quickly as possible and react fast to restore power again. When supervising a power grid good communication systems are essential. Communications systems serve as links between the following functional systems: • Contacting personnel with radio (Mobile or Handheld) • Contacting personnel \\ith pagers (Digital or Analogue) • Receiving up to date information on the SCADA network • Protection on power lines and transformers (Fault conditions) Without good telecommunication ESKOM will not be able to control the national grid efficiently. The Telecommunication Department fulfil a vital role ensuring that the National Grid functions at its optimum. It is normally impossible to do an accurate measurement of the power level in dBm or dBv on a communication line while an RTU is communicating to the MASTER. This is mainly because the duration of the data burst on the communication line is less than the sample time required by the level meters available. The time duration on a TELKOR PUTU general poll is 250ms. With the available digital meters (e.g. W & G SPM33A) it is totally impossible to get a power level reading because the sampling time of the instrument is I second. With the analogue meters available (e.g. W&G SPM09, SPM31) it is possible to get a reading, but this normally between 2 dBm and 4 dBm Iow, because of the dynamic behaviour of the moving coil. Thus before the pointer of the meter has reached the correct level, the burst of data has stopped This is characterised by three quantities: 1. The inertia (1) of the moving coil about its axis of rotation. 2. The opposing torque (S) developed by the coil suspension 3. The damping constant (D) A solution is to sample the receive and transmit levels during polling with an electronic circuit and feed it into an ADC connected to a Microcontroller (e.g. 8031 family). The Microcontroller will do all the converting and mathematical functions and will output a value through a DAC. This output value will be a current (mA) value directly proportional to the input level (e.g. -20dBm to OdBm = 0 to 5mA). These RX and IX level values can be fed into analogue inputs of the RTU. This realtime measurement of the levels on communication lines will be available at the SCADA master. These values can then be trended and if a downward trend is observed, maintenance can be done on the line before a failure. This should result in higher availability of the SCADA network.

M.Comm. / This study consists of two parts. There is a theory part and a research part. The first part of the theory encompasses effectiveness and efficiency of project management within the telecommunication company. The theory focuses on project management in general and the management tasks of the project manager that can improve the effectiveness and efficiency. This part focuses on projects versus operations, the flow of power, organisational structure, projects versus functional management, delegation, project life cycle, formal and informal project management, the use of computers, quotations, quality, the project manager and the law. The second part of the theory focuses on management tasks of the project manager such as attributes and skills, the task of the project manager, project planning, co-operation, meetings, leadership, communication, conflicts, co-ordination and motivation. The research is focused on the effectiveness and efficiency of project management within the telecommunication company. The final part gives suggestions to solve all the problems that are present in the company.

M.Comm. / Most modern and even not so modern businesses are currently investing in the hire or purchase of private access branch exchange (PABX) equipment. Usually the main concern is one of reduced costs to the company, since the internal calls between users on the same PABX are not routed via the public telecommunications operator (Telkom) and therefore free of charge [ James, 1997: 17 ]. Larger companies are experiencing the problem that their offices are distributed countrywide. They can install PABX equipment at each regional office, but this will only allow the employees within the regional office to communicate via internal calls. These organisationssoon realise the need for a voice network that provide them with the capability to communicate internally on a country-wide and in some cases, even a worldwide scale. A private voice network can be established by following two routes. If the company is relatively small and cannot afford its own transmission infrastructure in the form of openwire routes. coaxial cables. microwave routes, satellite routes and the associated multiplexers and flexible multiplexers. then they can lease transmission infrastructure from the public telecommunications operator (Telkom) and pay rental and other associated charges for usage thereof If the company can afford the capital investment in its own transmission infrastructure, it will be capable of communicating on a countrywide basis without relying on the service provided by the public telecommunications operator. In most cases, however, the latter option is illegal, due to regulatory protection of the national telecommunications operator. as stipulated by the telecommunications act (103/1996). In some cases, like the Transnet group, legislation requires the use of a private telecommunications network. The reason for this was that a major catastrophe in the transport industry might result due to problems with the telecommunications facilities. In that case, the public telecommunications operator would not accept any responsibility for the consequences of the break in communications. Transtel is the business unit that acts as a "private telecommunications operator" for the Transnet group . Transtel provides both voice and data communications to its clients within the Transnet group . In this case the main concern is not one of reduced costs, and therefore Transtel is implementing a tariff structure similar to that of the public telecommunications operator. The problem of providing voice communications between geographically distributed offices must be solved reliably and efficiently by the private voice network implemented by Transtel to serve the Transnet group. This implies that Transtel have the challenging responsibility to implement a managed voice network, in order to ensure better service levels than can be obtained from Telkom. The next problem that faces the private telecommunications operators for organisations with several business units and a plethora of departments, is that the costs for telecommunications facilities must be broken down into separate amounts per business unit and per department. This breakdown of costs must also reflect actual usage of the communications network and the billing systems must have the capability to generate detailed reports on network usage, as requested. In organisations like Transnet, where lower costs were not the primary objective of the private communications network, usage of the private network as well as usage of a combination of the private and public network, is being billed back to the department that uses the service. In short, the private telecommunications operator must rely on highly efficient and reliable billing systems to keep track of network costs and clients, since it operates as a separate business unit within the group and have to show a return on the investment on network technology [ Wasnick, 1998 : 26 ]. Inevitably, the private communications operator will need to ensure its clients of superior telecommunications services, and in many cases formal service level agreements will define the acceptable service level from the client's point of view. In order to place the private operator in a position to honour the service level agreements, its networks and especially its voice network must be managed by a global, integrated network management system. The network management system must be global in the sense that it manages all the resources in the voice network as well as resources in other networks that are utilised by the voice network. In order to facilitate optimal service levels, the network management system must be fully integrated with the rest of the operator's information technology infrastructure. It is, however, not enough to have a network management system in place that can cater for all the technical network management needs of the organisation. The organisational structure, management philosophies and business processes must also be adapted, in order to fully utilise the potential benefit of the technical network management functionality [ Sutherland, 1998 : 8 ]. A multi-faceted approach to voice network management will ensure that bi-directional information flow and a balance is established between the technical network side, the business side and the organisational structure, as depicted in Figure 1.1. A major disadvantage will be overcome by focusing on the total telecommunications environment, rather than emphasising the business environment, the technical environment or the organisation. No modern telecommunications operator will be able to survive in the highly competitive environment without a strong business focus integrated with technical excellence and supported by an appropriate organisation structure.

The landscape of television is changing. Modern Internet enabled sets are now capable computing devices offering new forms of connectivity and interaction to viewers. One development enabled by this transition is the distribution of auxiliary content to a portable computing device, such as a mobile phone or tablet, working in concert with the television. These configurations are enabled by second screen applications that provide relevant content in synchronisation with the programme on a nearby television set. This thesis extends the notion of second screen to arrangements that incorporate multiple mobile devices working with the television, utilised by collocated groups of participants. Herein these arrangements are referred to as ‘many-screen’ television. Two many-screen applications were developed for the augmentation of sports programming in preparation of this thesis; the Olympic Companion and MarathOn Multiscreen Applications. Both of these applications were informed by background literature on second screen television and wider issues in HCI multiscreen research. In addition, the design of both applications was inspired by the needs of traditional and online broadcasters, through an internship with BBC Research and Development and involvement in a YouTube sponsored project. Both the applications were evaluated by collocated groups of users in formative user studies. These studies centred on how users share and organise what to watch, incorporate activity within the traditionally passive television viewing experience and the integration of user-generated video content in a many-screen system. The primary contribution of this thesis is a series of industry validated guidelines for the design of many-screen applications. The guidelines highlight issues around user awareness devices, content and other user’s actions, the balance between communal and private viewing and the appropriation of user-generated content in many-screen watching.

With recent developments in the Global Satellite Navigation Systems (GNSS), the applications and services of positioning and navigation have developed rapidly worldwide. Location-based services (LBS) have become a big application which provide position related services to the mass market. As LBS applications become more popular, positioning services and capacity are demanded to cover all types of environment with improved accuracy and reliability. While GNSS can provide promising positioning and navigation solutions in open outdoor environments, it does not work well when inside buildings, in tunnels or under canopy. Positioning in such difficult environments have been known as the indoor positioning problem. Although the problem has been looked into for more than a decade, there currently no solution that can compare to the performance of GNSS in outdoor environments. This thesis introduces a collaborative indoor positioning solution based on particle filtering which integrates multiple sensors, e.g. inertial sensors, Wi-Fi signals, map information etc., and multiple local users which provide peer-to-peer (P2P) relative ranging measurements. This solution addresses three current problems of indoor positioning. First of all is the positioning accuracy, which is limited by the availability of sensors and the quality of their signals in the environment. The collaborative positioning solution integrates a number of sensors and users to provide better measurements and restrict measurement error from growing. Secondly, the reliability of the positioning solutions, which is also affected by the signal quality. The unpredictable behaviour of positioning signals and data could lead to many uncertainties in the final positioning result. A successful positioning system should be able to deal with changes in the signal and provide reliable positioning results using different data processing strategies. Thirdly, the continuity and robustness of positioning solutions. While the indoor environment can be very different from one another, hence applicable signals are also different, the positioning solution should take into account the uniqueness of different situations and provide continuous positioning result regardless of the changing datWith recent developments in the Global Satellite Navigation Systems (GNSS), the applications and services of positioning and navigation have developed rapidly worldwide. Location based services (LBS) have become a big application which provide position related services to the mass market. As LBS applications become more popular, positioning services and capacity are demanded to cover all types of environment with improved accuracy and reliability. While GNSS can provide promising positioning and navigation solutions in open outdoor environments, it does not work well when inside buildings, in tunnels or under canopy. Positioning in such difficult environments have been known as the indoor positioning problem. Although the problem has been looked into for more than a decade, there currently no solution that can compare to the performance of GNSS in outdoor environments. This thesis introduces a collaborative indoor positioning solution based on particle filtering which integrates multiple sensors, e.g. inertial sensors, Wi-Fi signals, map information etc., and multiple local users which provide peer-to-peer (P2P) relative ranging measurements. This solution addresses three current problems of indoor positioning. First of all is the positioning accuracy, which is limited by the availability of sensors and the quality of their signals in the environment. The collaborative positioning solution integrates a number of sensors and users to provide better measurements and restrict measurement error from growing. Secondly, the reliability of the positioning solutions, which is also affected by the signal quality. The unpredictable behaviour of positioning signals and data could lead to many uncertainties in the final positioning result. A successful positioning system should be able to deal with changes in the signal and provide reliable positioning results using different data processing strategies. Thirdly, the continuity and robustness of positioning solutions. While the indoor environment can be very different from one another, hence applicable signals are also different, the positioning solution should take into account the uniqueness of different situations and provide continuous positioning result regardless of the changing data. The collaborative positioning aspect is examined from three aspects, the network geometry, the network size and the P2P ranging measurement accuracy. Both theoretical and experimental results indicate that a collaborative network with a low dilution of precision (DOP) value could achieve better positioning accuracy. While increasing sensors and users will reduce DOP, it will also increase computation load which is already a disadvantage of particle filters. The most effective collaborative positioning network size is thus identified and applied. While the positioning system measurement error is constrained by the accuracy of the P2P ranging constraint, the work in this thesis shows that even low accuracy measurements can provide effective constraint as long as the system is able to identify the different qualities of the measurements. The proposed collaborative positioning algorithm constrains both inertial measurements and Wi-Fi fingerprinting to enhance the stability and accuracy of positioning result, achieving metre-level accuracy. The application of collaborative constraints also eliminate the requirement for indoor map matching which had been a very useful tool in particle filters for indoor positioning purposes. The wall constraint can be replaced flexibly and easily with relative constraint. Simulations and indoor trials are carried out to evaluate the algorithms. Results indicate that metre-level positioning accuracy could be achieved and collaborative positioning also gives the system more flexibility to adapt to different situations when Wi-Fi or collaborative ranging is unavailable. The collaborative positioning aspect is examined from three aspects, the network geometry, the network size and the P2P ranging measurement accuracy. Both theoretical and experimental results indicate that a collaborative network with a low dilution of precision (DOP) value could achieve better positioning accuracy. While increasing sensors and users will reduce DOP, it will also increase computation load which is already a disadvantage of particle filters. The most effective collaborative positioning network size is thus identified and applied. While the positioning system measurement error is constrained by the accuracy of the P2P ranging constraint, the work in this thesis shows that even low accuracy measurements can provide effective constraint as long as the system is able to identify the different qualities of the measurements. The proposed collaborative positioning algorithm constrains both inertial measurements and Wi-Fi fingerprinting to enhance the stability and accuracy of positioning result, achieving metre-level accuracy. The application of collaborative constraints also eliminate the requirement for indoor map matching which had been a very useful tool in particle filters for indoor positioning purposes. The wall constraint can be replaced flexibly and easily with relative constraint. Simulations and indoor trials are carried out to evaluate the algorithms. Results indicate that metre-level positioning accuracy could be achieved and collaborative positioning also gives the system more flexibility to adapt to different situations when Wi-Fi or collaborative ranging is unavailable.