At 12:30 p.m. in Avery 103, Andrew Mittleider will present his thesis titled “Analysis, Optimization, and Implementation of a UAV-Based Wireless Power Transfer System.”
Abstract: Wireless power transfer is rapidly advancing in its ability to efficiently transfer power to a variety of devices. As the efficiency increases, more applications for these systems arise. Since magnetic resonant wireless power transfer can only transfer a small amount of power, most current applications only focus on powering low-powered devices. Wireless Sensor Networks are composed of many low-powered nodes which currently require human interaction to remain powered. We propose recharging a low-powered Wireless Sensor Network (WSN) with a magnetic resonant wireless power transfer system attached to a quadrotor Unmanned Aerial Vehicle (UAV).
This thesis addresses three main challenges with this method of powering a WSN.
First, quadrotor UAVs are small and have limited payload capacities. Since a larger power transfer system generally results in better power transfer range and efficiency, we optimize the parameters of a wireless power transfer system for the small UAV. We show that, compared to our previous work, the power transfer coils’ quality factor can be nearly doubled while retaining the same mass. Second, the UAV needs very precise control to transfer power to a small WSN node. We use a the sensed magnetic field from the Wireless Power Transfer system coupled with a simulated optical flow system to show that we can localize to within 21 cm to transfer 3.38 W to the sensor node. Last, the UAV has significant power limits of its own. We show that by optimizing the speed of travel and optimizing the mass of the UAV’s battery, we can increase the range of the UAV from 3 km in the worst case to 9.3 km in the optimal case.
Committee members: Dr. Carrick Detweiler and Dr. Sebastian Elbaum (Advisors), Dr. Jitender Deogun and Dr. Anita Sarma
At 2 p.m. in Avery 347, Yaoxin Liang will present his thesis titled “Secret Key Generation for Symmetric Crytosystem in Wireless Networks.”
Abstract: Secure wireless communication requires the establishment of a secure channel, which is challenging and costly in a lot of scenarios. To provide secret keys for symmetric cryptosystems in wireless networks, previous research has studied the pairwise secret key generation based on the shared information between legitimate entities by exploiting the characteristics of the wireless channel. However, most of the variables they use are measured in the time domain, and heavily depend on the dynamic environments to get enough entropy. Fast key generation is impossible with stationary entities when the environment is relatively stable. To release this constraint, we choose the pairwise radio power spectrum as an alternative, i.e., the radio signal strength (RSS) measurements in the frequency domain, collected at two ends of a link to extract the keys. To our best knowledge, this variable is for the first time utilized in the secret key generation to get two highly correlated bit streams as “fuzzy'' secret keys and advances the RSS measurements in the time domain in prior research.
Committee members: Dr. Ziguo Zhong (Advisor), Dr. Lisong Xu and Hongfeng Yu
At 4 p.m. in room 112A of the Schorr Center, Jihoon Yun will present his thesis titled “Harnessing Constructive Interference for Localization in Indoor Environments.”
Abstract: Wireless network localization using Radio Signal Strength (RSS) is considered a classic option in many scenarios because of its convenience and economic feasibility. However, this localization method is easily affected by various influences, such as unknown radio path loss factors, multi- path effects, hardware discrepancies, antenna orientation, and so forth. Among these, multi- path effects have a profound effect on uni-channel RSS measurements in the ”microscale”, defined as a small region within several wavelengths of the radio signal and thus degrade to the accuracy of transitional localization methods based on uni-channel fingerprinting. In response to the above limitation, this thesis introduces Harnessing Constructive Interference (HCI), a system for indoor positioning using the phenomenon of constructive interference. The key observation behind the HCI is that peak RSS measurements in the frequency domain, which are results of the constructive interference, feature a relatively small dynamic range. Utilizing this observation, we propose the HCI design to improve the performance of the location estimate. In addition, we provide three profiling methods: symmetric, asymmetric with Spline interpolation and Whittaker-Shannon interpolation to reduce the system overhead. To evaluate, the proposed designs have been implemented on the NU platform and experiments were carried out in three different environments with 56 sampling positions, 5 anchor nodes, and a collective number of 1,447,800 RSS measurements. By comparing with two representative algorithms, e.g., RADAR and HORUS, it is shown that the proposed HCI system significantly reduces localization errors.
Committee members: Dr. Ziguo Zhong (Advisor), Dr. Changbum Ahn and Dr. Massimiliano Pierobon