| الوصف: |
Innovative sensing modalities for wearable devices continue to emerge with the advancement of microelectromechanical systems and material science. Compared to conventional sensing modalities, these are either more accurate or more energy efficient. In keeping with this trend, this thesis introduces innovative sensing modalities, aiming to quantitatively improve on accuracy or energy consumption and finally lead to qualitatively difference in working scenarios. The contributions of this thesis are three-folded. Firstly, via implementing a new type of highly sensitive, stretchable, optical transparent, and low-cost strain sensor, we addressed the problem of human posture detection with casual loose-fitting smart garments. We developed a smart garment system—E-Jacket—by attaching novel sensors to an off-the-shelf casual jacket. In addition to the novel highly sensitive strain sensor, we implemented a state-of-the-art human activity recognition tool, the combination of a convolutional neural network and a long short-term memory recurrent network. Our evaluation showed that the E-Jacket can achieve up to 91.7, 84.4, and 88.4 per cent detection accuracy, respectively, for these three case studies. Second, we developed H2B, which is a system for securely pairing wearable devices by generating a shared secret key from interpulse interval between heartbeats. In the H2B system, we implemented cost- and energy-efficient piezoelectric sensors to replacing conventional electrocardiogram or photoplethysmogram sensors. To handle the high rate of bit mismatch, we also proposed a novel compressive sensing-based reconciliation method that can be adopted on all kinds of symmetric key generation systems. Our results showed that H2B has a pairing success rate of 95.6 per cent. Third, we explored the feasibility of using KEHs to collect gait signals for device authentication and symmetric secret keys generation continuously. Based on preliminary analysis, we developed KEHKey, a gait-based authentication and key generation system that uses KEH to replace accelerometers. Our results showed that KEHKey is able to generate the same key for two KEH-embedded devices at a speed of 12.57 bps, while reducing energy consumption by 59 per cent, compared to accelerometer-based methods, which makes it suitable for continuous operation. |