13.Hybrid TOA AOA Based Mobile Localization with and without Tracking in CDMA Cellular Networks

13.Hybrid TOA AOA Based Mobile Localization with and without Tracking in CDMA Cellular Networks

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Hybrid TOA/AOA-based Mobile Localization With and Without Tracking in CDMA Cellular Networks Victoria Ying Zhang, Albert Kai-sun Wong, Kam Tim Woo and Robin Wentao Ouyang Department of Electronic and Computer Engineering The Hong Kong University of Science and Technology Clear Water Bay, Hong Kong victoria@ust.hk, eealbert@ust.hk, eetim@ust.hk, oywtece@ust.hk Abstract- This paper proposes a hybrid TOA/AOA (Time of Arrival/Angle of Arrival)-based localization algorithm for Code Division Multiple Access (CDMA) networks. The algorithm extends the Taylor Series Least Square (TS-LS) method originally developed for TOA-based systems to incorporate AOA measurements. In addition, tracking algorithms utilizing velocity and acceleration measurements are investigated. Simulation results illustrate that the proposed TOA/AOA TS-LS can provide better performance than conventional schemes in localization accuracy and in reduced likelihood of encountering non- convergence problem compared with TOA TS-LS. Tracking algorithms using the Extended and Unscented Kalman Filter (EKF and UKF) can track the objects relatively well, further decreasing the positioning error. UKF is found to provide closer tracking of the trajectory than EKF, for it truly captures the statistical mean and variance of the noises. Keywords-Extended Kalman Filter (EKF); Positioning; Taylor Series Least Square (TS-LS); Tracking; Unscented Kalman Filter (UKF) I. INTRODUCTION Accurate location finding techniques for people and terminals have received considerable attention over the past decade, especially since the localization accuracy becomes mandatory in the Enhanced-911 (E-911) services by Federal Communication Commission (FCC) [1]. Undoubtedly, the Global Positioning System (GPS) is the most well known location technology in use today. Increasingly popular among mobile terminals is the use of Assisted-GPS (AGPS), which greatly reduces the GPS time-to-first-fix. In [2], we described a complete AGPS-based tracking system for elderly individuals. The system has been shown to work quite well in the outdoor environment, with continuous terminal battery operation of no less than 7-10 days if position fixes are performed infrequently. Even for an AGPS-enabled system, it remains attractive that the widely deployed Code Division Multiple Access (CDMA) cellular networks can be used to perform network-based localization. Power consumption for AGPS fixes is much lower than for GPS, but still each AGPS fix consumes several minutes of standby current. This means that fixes cannot be performed too frequently, often resulting in insufficient data to provide an accurate picture of the user mobility pattern. Network-based localization by the cellular network alleviates the terminal of intensive processing and thus reduces the power consumption. It can either be used by itself or in conjunction with AGPS to fill the void of GPS denied cases and time gap between infrequent AGPS fixes.
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13.Hybrid TOA AOA Based Mobile Localization with and without Tracking in CDMA Cellular Networks

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