Measurements of vibrations, such as sound hitting an object or running a motor, are widely used in industry and research. Traditional methods need either direct contact with the object or a laser vibrometer. Although computer vision methods have been applied to solve this problem, high speed cameras are usually preferred. This study employs a consumer level rolling shutter camera for extracting main frequency components of small vibrations. A rolling shutter camera exposes continuously over time on the vertical direction of the sensor, and produces images with shifted rows of objects. We utilize the rolling shutter effect to boost our capability to extract vibration frequencies higher than the frame rate. Assuming the vibration amplitude of the target results in a horizontal fronto-parallel component in the image, we compute the displacement of each row from a reference frame by our novel phase matching approach in the complex-valued Shearlet transform domain. So far the only way to process rolling shutter video for vibration extraction is with the Steerable Pyramid in a motion magnification framework. However, the Shearlet transform is well localized in scale, location and orientation, and hence better suited to vibration extraction than the Steerable Pyramid used in the high speed video approach. Using our rolling shutter approach, we manage to recover signals from 75Hz to 500Hz from videos of 30fps. We test our method by controlled experiments with a loudspeaker. We play sounds with certain frequency components and take videos of the loudspeaker's surface. Our approach recovers chirp signals as well as single frequency signals from rolling shutter videos. We also test with music and speech. Both experiments produce identifiable recovered audio.

This work describes the design and implementation details of a reliable group communication mechanism. The mechanism guarantees that messages will be received by all the operational members of the group or by none of them (atomicity). In addition, the sequence of messages will be the same at each of the recipients (order). The message ordering property can be used to simplify distributed database systems and distributed processing algorithms. The proposed mechanism continues to operate despite process, host and communication link failures (survivability). Survivability is essential in fault-tolerant applications. / Science, Faculty of / Computer Science, Department of / Graduate

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<p>Solid-state LED lighting is a promising technology to improve the energy efficiency of general illumination. The inherent modulation bandwidth of these devices can be exploited to provide a dual role as a communication device. This method of communication is termed visible light communications (VLC).</p> <p>Due to dispersive nature of the VLC channel, orthogonal frequency division multiplexing (OFDM) has been proposed to allow multi-user communication while mitigating the effects of inter-symbol interference (ISI). However, OFDM is in general not compatible with intensity modulation and direct detection (IM/DD) channels since it has both positive and negative amplitudes. Various techniques have been proposed that provide compatible optical OFDM signaling such as DC-biased OFDM, asymmetrically clipped optical OFDM (ACO-OFDM), and pulse amplitude modulated discrete multi-tone (PAM-DMT).</p> <p>This thesis develops spectrally factorized optical OFDM (SFO-OFDM) as a framework to implement OFDM on optical intensity channels. The drawbacks of conventional methods are mitigated in SFO-OFDM. Contrary to ACO-OFDM and PAM-DMT, the proposed technique uses all the available bandwidth for data modulation and does not require reserved subcarriers. Simulation results verify that SFO-OFDM has gain both in optical power efficiency and peak-to-average power ratio compared to conventional optical OFDM schemes.</p> <p>Furthermore in this thesis, a new receiver design for ACO-OFDM and PAM-DMT is proposed. Unlike conventional receivers that ignore the structure of the transmitted signal, the new detector exploits this structure to improve the optical power efficiency. By observing the time domain samples, a simple pairwise maximum likelihood detector is developed and used to remove half of the noise power. It is also shown by simulation results that employing the proposed detector design leads to a significant gain in optical power efficiency.</p> / Master of Applied Science (MASc)