Optical wireless MIMO communication

This thesis provides an in-depth investigation and evaluation of infrared optical wireless MIMO communication systems to be applied in both indoor and outdoor environment. The principle objective of the research is to demonstrate both the advantages and disadvantages of the optical wireless MIMO systems using different modulation types. The first part provided analyses of important OW configurations using APD receivers using WMC model and SISO, MISO, SIMO and MIMO configuration. Thus, an analytical expression for 2-1 MISO, 1-2 SIMO and MIMO was successfully developed. This part also illustrates the coding gains possible using diversity schemes for APD OW systems. In the presence of strong fading, the SISO approach is rendered virtually useless, whereas diversity offers acceptable BER values. The results underpin the approach of this thesis, where indoor PIN diode based experimental measurements confirm the gains offered by diversity. In the second part of the work, several optical wireless MIMO systems applicable for the indoor environment are developed for three different modulation types, OOK modulation, PPM modulation and SIR-RZI modulation. These modulations are used in optical MIMO systems are studied for which, mathematical models that evaluate the BER performance of the MIMO system for different axis displacement and for different distances between transmitters and receivers. Based on the results, the PPM system has been shown to present the best BER performance, including high interference-resistance capability. A group of new mathematical models have been evaluated, which demonstrates a high level of correlation with the results derived from empirical models at 93%. Thus, the mathematical models developed and used for the specified evaluation appear to correspond reasonably well, and can be applied in future research on these aspects

Baud sampling bit synchroniser for channels with data dependent noise

A bit synchronisation algorithm for channels with data dependent noise which operates with one sample per symbol is presented. The algorithm uses the same information as the Mueller and Muller (M&M) algorithm, and is optimised for operation with data dependent noise. The performance is derived and it is shown that signfkant improvements over the M&M algorithm can be obtained in practical optical channels

Detection Statistics Of Multiple-Pulse Optical Signals Through Atmospheric Turbulence

Statistics are studied for signal detection in optical communication systems operating through the atmosphere. Optical communication systems with which this study is concerned are those that employ intensity modulation and direct detection. Atmospheric turbulence, which is fluctuations in the atmosphere\u27s optical index of refraction, is a hindrance to optical wireless communications because of the signal fades, called scintillation, it causes at the optical receiver. In order to mitigate the deteriorative effect of turbulence on the communications system, the signal length and detection threshold for the signal detector must be properly chosen. In this study, mathematical models for photoelectron generation in the receiver\u27s photodiode and for the atmospheric turbulence channel enable the derivation or numerical calculation of the probability of miss, which is crucial for determining the signal length and detection threshold. The two commonly used types of photodiodes are the p-i-n photodiode and the avalanche photodiode. A light source of constant intensity impinging upon a photodiode will generate a photoelectron count which is a Poisson process for a p-i-n and a follows the McIntyre-Conradi distribution for an avalanche photodiode. In this study, the Webb distribution will be used as an approximation for the McIntyre-Conradi distribution. When the light intensity is itself a random process, as is the case for the received optical intensity after traveling through atmospheric turbulence, the photoelectron count will be a doubly (or conditional) stochastic process. To model the effect atmospheric turbulence, three different probability distributions are utilized to describe the received optical intensity. These are the lognormal distribution, valid for weak turbulence, the gamma-gamma distribution, valid for a range of turbulence strengths and the exponential distribution, valid for the saturation regime of signal scintillation. With these models, the probability of miss is derived or numerically calculated. Simulations are provided to verify derived formulae for the probability of miss. Applying results in this study, a system designer can determine appropriate signal length and detection threshold settings in order to meet system specifications for signal detection

Photovoltaics as high-speed optical wireless communication receiver

With an ever-growing network of billions of interconnected smart devices in the era of the Internet of Things, high-speed communication has inspired research into the use of low energy and high-speed free-space optical (FSO) communication systems. In FSO communication, light-emitting diodes (LEDs) and lasers are used for wireless data transmission in indoor and outdoor environments and photodiodes are used as data receivers. But these receivers have two main disadvantages – they require an external power source to operate, and their small active area makes alignment challenging. A promising solution to these problems is the use of solar panels as data receivers. As photovoltaic (PV) panels have a larger active area compared to that of conventional photodiodes, they relax the strict alignment requirements and can also simultaneously harvest energy from sunlight. The current work investigates the use of Si-based off-the-shelf PV panels as FSO receivers to build an energy-neutral and high-speed FSO system. As solar panels were never built as optical data communication receivers, they have a very small communication bandwidth compared to photodiodes. In this work, a theoretical model of the solar panel is provided and, using analogue equalization, the usable communication bandwidth of a solar panel is extended. PV panels were primarily designed to harvest energy from sunlight. Using the analytical model, simultaneous energy harvesting, and data communication performances are evaluated. Moreover, the trade-off between the energy harvesting and data communication capability of the solar panel is shown. Furthermore, the use of different spectrally efficient modulation techniques such as direct current optical orthogonal frequency division multiplexing (DCO-OFDM) and discrete multitone pulse-amplitude modulation (DMT-PAM) are compared when used with a solar panel as an optical receiver. It has been found that each modulation scheme is usable under different applications. Using the simulated results from the analytical model an FSO prototype was designed and developed, demonstrating the use of solar panels as the receivers. A receiver circuit to interface the solar panel with the FSO system was designed and developed to demonstrate the data communication and energy harvesting performance. Data rates as high as 75 Mb/s is demonstrated using DCO-OFDM and offline processing using an off-the-shelf Si-based solar panel. The PV panel-based FSO system was used to provide internet access to two residential properties on a remote island in the northern part of Scotland. The performance of the prototype was carefully studied under various weather conditions. Furthermore, the maximum user throughput achieved by the prototype is 28.3 Mb/s with the simultaneous energy harvesting capability of up to 4.5 W. Lastly, the design of a custom-built solar panel is proposed which doubles the data rates shown in this work and can be implemented alongside a small-scale to large-scale solar energy harvesting infrastructure

MSFC Skylab Orbital Workshop, volume 5

The various programs involved in the development of the Skylab Orbital Workshop are discussed. The subjects considered include the following: (1) reliability program, (2) system safety program, (3) testing program, (4) engineering program management, (5) mission operations support, and (6) aerospace applications

Space Transportation System and associated payloads: Glossary, acronyms, and abbreviations

A collection of acronyms in everyday use concerning shuttle activities is presented. A glossary of terms pertaining to the Space Transportation System is included

Space Transportation System and associated payloads: Glossary, acronyms, and abbreviations

A collection of acronyms now in everyday use in the Shuttle world are listed. It is a combination of lists that were prepared at the Kennedy and Johnson Space Centers and by the Air Force

Space transportation system and associated payloads: Glossary, acronyms, and abbreviations

A collection of some of the acronyms and abbreviations now in everyday use in the shuttle world is presented. It is a combination of lists that were prepared at Marshall Space Flight Center and Kennedy and Johnson Space Centers, places where intensive shuttle activities are being carried out. This list is intended as a guide or reference and should not be considered to have the status and sanction of a dictionary

Geology at ANU (1959-2009)

This history was undertaken to celebrate the 50th anniversary of the Geology Department at ANU, and to honour its founding professor David A. Brown. It includes contributions from some 100 former students outlining their career successes. This history was compiled by Dr Mike Rickard, a staff member of the Department of Geology from 1963 to 1997, who also served as Head of Department for seven years. He graduated BSc and PhD from Imperial College London in 1957 and has specialised in mapping the structure of mountain chains in Ireland, Canada, Norway, and southern South America. He also mapped volcanic rocks for the Geological Survey of Fiji. He taught Structural Geology and Tectonics and has supervised field work in south eastern and central Australia. After retirement he has taught U3A courses in Earth Science

Geology at ANU (1959-2009)

This history was undertaken to celebrate the 50th anniversary of the Geology Department at ANU, and to honour its founding professor David A. Brown. It includes contributions from some 100 former students outlining their career successes. This history was compiled by Dr Mike Rickard, a staff member of the Department of Geology from 1963 to 1997, who also served as Head of Department for seven years. He graduated BSc and PhD from Imperial College London in 1957 and has specialised in mapping the structure of mountain chains in Ireland, Canada, Norway, and southern South America. He also mapped volcanic rocks for the Geological Survey of Fiji. He taught Structural Geology and Tectonics and has supervised field work in south eastern and central Australia. After retirement he has taught U3A courses in Earth Science