Search

Accurate and high-speed object movement tracking systems often face significant challenges due to signal instability caused by the object's movement and rotation. To address these issues, we present STABack, a novel object tracking system using backscatter tags and accelerometer sensors, designed for high-accuracy, high-speed movement tracking. We developed an amplitude stabilization algorithm which uses envelope detection to reduce the impact of high-frequency movement on the signal, and uses dynamic threshold output to lower the BER in backscatter demodulation. Our method reduces the BER by 0.3757 compared to the regular demodulation method, resulting in a final BER of 0.07. Our evaluation of the STABack prototype shows that it achieves a median distance measurement accuracy of 6.45 cm with a standard deviation of 6.95 cm, under the condition of a speed of 120 cm. The attitude angle estimation's mean error is under 7 degrees. The system's accuracy in detecting the target object's trajectory is as high as 99%, and it can still decode with a bit error rate of no more than 0.034 at a speed of 166 cm/s. The power consumption of our system prototype is only 38.54 μW based on our experimental results. Overall, our results demonstrate that STABack can accurately estimate the movement and rotation of target objects in unstable backscatter channels. [ABSTRACT FROM AUTHOR]

Recent works have achieved considerable success in improving the concurrency of backscatter network. However, they do not optimize the balance between throughput and spectrum occupancy, both of which serve as pivotal parameters in concurrent transmissions. Moreover, these works also introduce complex components on tag thereby increasing both power consumption and deployment costs. In this article, we propose Spray, a tag-lightweight system to achieve high throughput and narrow-band occupancy with low power. The key idea is to incorporate an agile channel allocating and scheduling mechanism into the backscatter network. This approach allows for efficient spectrum utilization and concurrency without the need for energy-intensive components. To optimize throughput in the presence of the challenge of harmonic interference, we introduce a novel algorithm that determines the channels with an optimal combination of central frequencies and bandwidths. Additionally, we propose a fair scheduling strategy to ensure equitable transmission opportunities for all tags. We prototype the Spray tag using commercial off-the-shelf components and implement the excitation and receiver with software-defined radio platform. Our evaluation shows that the system supports 30 parallel tags transmitting in the bandwidth of 600 kHz and the throughput can reach more than 280 kbps. [ABSTRACT FROM AUTHOR]

We report room-temperature observations of the quantum conductance corrections caused by the weak localization in graphene films synthesized using solid-state-source chemical vapor deposition. Both Raman spectroscopy and Hall measurements showed strong disorder in the samples with a low mobility of ∼430 cm2/V s. The emergence of weak localization at room temperature arises from the competition between the valley-dependent scattering and the thermal dephasing in such low-quality samples, although quantum effects normally appear in the samples that have an ideal structure at cryogenic temperatures. The large disorder in our low-mobility samples unexpectedly preserved the quantum mechanical weak localization. [ABSTRACT FROM AUTHOR]