Master of Science (MS), Ohio University, 2009, Electrical Engineering (Engineering and Technology)

The thesis provides statistical characterization and modeling of wireless channel transitions in both indoor and outdoor environments based on narrowband and wideband measurements. We characterize delay dispersion characteristics of the wireless channel as it transits from a line of sight (LOS) to a non-line of sight (NLOS) region. For the narrowband indoor channel transition measurements, received power levels versus frequency were measured in the 900 MHz unlicensed ISM frequency band. The narrow band channel results quantify some fading characteristics versus frequency and distance, and we also estimate values for the “power correlation” bandwidth. The power correlation values of 0.5 were observed for bandwidths of approximately 7 MHz. For the wideband channel transition measurements, power delay profiles (PDP) were measured in indoor and outdoor environments in the 5 GHz frequency band. Several delay spread parameters - root mean square delay spread, delay window, and channel impulse response X, dB (CIRX,dB) duration - were obtained for LOS and NLOS regions from the measured PDPs, and we quantify example changes in these parameters due to the transition. As expected, the delay spread parameters for NLOS regions are larger than those for LOS regions. Root mean-square delay spreads were found to increase from approximately 9 ns to 18 ns in going from LOS to NLOS regions, respectively. Wideband channel models were also developed for both regions for a bandwidth of 50 MHz. The channel models define tap amplitude fading distributions and parameters, tap energies, and Markov tap persistence parameters.

Committee: David W Matolak (Advisor); Jeffrey Dill (Committee Member); Trent Skidmore (Committee Member); Sergio Lopez (Committee Member) Subjects: Electrical Engineering; Engineering; Technology

Doctor of Philosophy (PhD), Ohio University, 2020, Electrical Engineering & Computer Science (Engineering and Technology)

In this dissertation, the problem of trajectory design for autonomous wheeled ground vehicles are investigated. Several line-of-sight (LOS) based trajectory design approaches are developed to solve the problem in various practical scenarios. For path planning of on-road driving, a LOS pure pursuit guidance (PPG) path planner is designed. Stability analysis for LOS PPG along a general reference path is conducted based on Lyapunov stability theory. By using the theoretical analysis results, a design guideline for the selection of the guidance parameters is derived. The geometric interpretation of LOS PPG for general guidance parameters is provided. Then, for a given feasible, collision-free path, the problem of converting the geometric path to a time-parameterized trajectory is studied. A novel receding-horizon type sub-optimal path-to-trajectory conversion algorithm is developed which is able to take into account dynamic constraints and has high computational efficiency. For the problem of path planning for autonomous car-like ground vehicle parking, a novel four-phase path planning algorithm is developed. The algorithm is able to cope with various parking scenarios in a unified, scalable manner with low computational cost. The four-phase algorithm is extended to standard N-trailer parking and a novel cascade path planning algorithm is developed. Besides the advantages inherited from the four-phase algorithm, the cascade algorithm for standard N-trailer parking is able to prevent jackknife phenomenon.

Committee: Jim Zhu (Advisor); Douglas Lawrence (Committee Member); Robert Williams II (Committee Member); Frank Van Graas (Committee Member); Xiaoping Shen (Committee Member); Sergio Ulloa (Committee Member) Subjects: Automotive Engineering; Electrical Engineering; Engineering

Master of Science (MS), Ohio University, 2018, Electrical Engineering (Engineering and Technology)

Building a Multiple Input Multiple Output (MIMO) channel to face real-world fading and noise efficiently needs good diversity and coding techniques. Alamouti coding provided a great launch pad to open up this area and made the MIMO technology affordable in day-to-day mobile and wireless communications. In this thesis, testing the MIMO system on different fading channels provided a great insight into how direct and scattering components affect the Bit Error Rate performance of the MIMO system. A 4x4 MIMO system is tested using a full code rate codeword on different fading channels by varying Rician factor (K). The thesis concluded that the 4x4 MIMO with referred codeword is performing better than 2x2 Alamouti STBC when Rician Factor k>8dB in indoor channels. In this thesis, by testing the referred 4x4 MIMO with other relative codewords, the importance of complex symbols handling and code rate is shown. The results help demonstrate the coding gain and spectral efficiency of test 4x4 MIMO. As people are interested in cloud computing and store more information online, hiking speed from Mobile devices to Base station also becomes essential.

Committee: Dill Jeffrey (Advisor) Subjects: Aeronomy; Communication; Electrical Engineering; Engineering; Information Science; Information Systems; Information Technology; Inservice Training; Mathematics; Technology

Master of Science (MS), Ohio University, 2016, Electrical Engineering (Engineering and Technology)

A vehicle-to-vehicle follower design based on RC Unmanned Ground Vehicle (UGV) is presented in this thesis. To achieve the desired performance for two-vehicle leader-follower, a 3DOF path trajectory tracking controller with a close-loop guidance controller are used, which consider both the kinematics and the dynamics characteristics of the vehicle model. In our research, we use a Trajectory Linearization Control (TLC) to achieve the path tracking, and a PID controller to guide the preceding vehicle. To this end, the following objectives have been achieved. First, a 3DOF kinematics and dynamics vehicle model has been built. Second, an Adaptive Cruise Control (ACC) Trajectory Linearizaton Control (ACCTLC) scheme is presented. Third, a Vehicle-to-Vehicle following Trajectory Linearizaiton Control is proposed. MATLAB/SIMULINK simulation testing of 3DOF control algorithm is presented, which verifies the algorithm. Future work include implementing the current controller design by installing those algorithms to the real RC car; as well as adding lane constraint to the current work; and adding obstacle avoidance to develop fully autonomous ground vehicle.

Committee: Michael Braasch (Advisor); Jim Zhu (Committee Co-Chair) Subjects: Electrical Engineering

PhD, University of Cincinnati, 2009, Engineering : Electrical Engineering

Large clock offsets and clock drifts impose many difficulties on wireless sensor network localization. Radio frequency (RF) ranging methods such as time-of-arrival (TOA) and time-difference-of-arrival (TDOA) are difficult to be implemented in such cases due to tight timing synchronization requirements. The differential-time- difference-of-arrival (dTDOA) method is proposed to overcome the problem of asynchronous clock offsets and clock drifts.Using the underlying dTDOA method, this thesis investigates two kinds of sensor localization applications that differ in system settings and RF ranging signals: wireless sensor network self-localization and non-GNSS (Global Navigation Satellite System) localization using signals of opportunity. For wireless sensor network self-localization, a number of theorems and a set of methods for determination of relative locations of all sensors are proposed. A linearization method and maximum likelihood estimation (MLE) methods for sensor location estimation are derived, and the linear approximate solution given by the linearization method is used to initialize the MLEs. The methods can achieve sensor localization using a single round of asynchronous TOA measurements, and thus greatly reduces the communication burden and timing constraint. Non-GNSS localization techniques that use signals of opportunity (e.g. TV/AM broadcast signals with known locations) without aid of satellite-based location systems (e.g. GPS) are promising, since they use readily available strong signals in a wide frequency range that are not susceptible to blockage or jamming. However, problems such as large asynchronous clock offsets among receivers and large broadcast signal frequency offsets arise because commercial broadcast signals are not dedicated for ranging purposes. The dTDOA positioning method is used to overcome the problems of biased broadcast signal frequencies and asynchronous receiver clocks. The proposed method eliminates the need for synchronous re (open full item for complete abstract)

Committee: H. Howard Fan PhD (Committee Chair); Ali Minai PhD (Committee Member); Dharma Agrawal PhD (Committee Member); Qing-An Zeng PhD (Committee Member); Patrick Garrett PhD (Committee Member) Subjects: Electrical Engineering