隨著全球導航衛星系統技術發展成熟，許多設施與系統均需高度依賴其定位、導航與授時服務。尤其定位服務更是重要，舉凡緊急救援、智慧城市、物聯網等，皆須可靠的無線定位服務。然而全球衛星導航系統主要發展於美國、俄羅斯、中國與歐盟各國，其餘國家於定位上並無自主性，且其訊號於到達地面時相對微弱且易受到干擾，為了避免定位服務受此些限制，目前有基於以非導航的機會訊號進行無線定位之系統。
至今仍有許多企業持續致力於低軌道衛星星系計畫，因此，本研究著重於低軌道衛星訊號無線定位系統。利用訊號到達時間與到達頻率兩量測量，分別以線性化最小平方法以及卡爾曼濾波器，進行靜態物體與動態物體之定位分析，估測位置相關參數，並以數值模擬的理論性能界限驗證系統的效能。另外，於定位計算過程中，同時考慮接收機時鐘誤差以及時鐘飄移之影響。
本論文進行低軌道衛星之軌道模擬，取得衛星與接收機之虛擬距離及都卜勒頻移，作為訊號到達時間與到達頻率兩量測量於定位計算，藉由不同情境之模擬，驗證低軌道衛星訊號無線定位技術於不同環境下之定位性能，並與全球定位系統進行比較。

With the full development of the Global Navigation Satellite System (GNSS), many systems and infrastructure have highly relied on positioning, navigation, and timing (PNT) services. Positioning service is especially essential. There are a variety of systems, such as emergency rescue, smart city, and Internet of Things (IoT), relying on reliable wireless positioning technology. However, GNSS is mainly developed by the United States, Russia, China, and the European Union, there is no positioning autonomy in other countries. Additionally, GNSS signals could become relatively weak on the ground and susceptible to interference. To account for the limitations of GNSS, other non-navigational signals of opportunity (SOOP) can be used to achieve geolocation wireless positioning as well.
Enterprises such as Boeing, OneWeb, and SpaceX have been committed to broadband LEO satellite Internet constellation. Therefore, the thesis focused on the LEO satellite-based wireless positioning system. The positioning analysis is conducted by Linearization-based Least Squares (LLS) and extended Kalman Filtering (EKF) approaches based on the time of arrival (TOA) and frequency of arrival (FOA) measurements under static and dynamic conditions, respectively. The relevant theoretical bounds are provided by way of numerical simulations to verify the positioning performance. Additionally, the clock bias and drifts of the receiver have also been considered.
Through simulations in LEO satellite orbits, the pseudoranges and Doppler frequency shifts between the satellites and the receiver are obtained as the measurements to compute the position. The performance of the LEO satellite-based wireless positioning technique is demonstrated by different scenario simulations and compared with the GNSS.

[1] Merry, Laura A., Ramsey M. Faragher, and Steve Scheding. "Comparison of opportunistic signals for localisation." IFAC Proceedings Volumes 43.16 (2010): 109-114.
[2] Raquet, John, and Richard K. Martin. "Non-GNSS radio frequency navigation." 2008 IEEE International Conference on Acoustics, Speech and Signal Processing. IEEE, 2008.
[3] McEllroy, Jonathan A. Navigation using signals of opportunity in the AM transmission band. AIR FORCE INST OF TECH WRIGHT-PATTERSON AFB OH SCHOOL OF ENGINEERING, 2006.
[4] Thevenon, Paul, et al. "Positioning using mobile TV based on the DVB‐SH standard." Navigation 58.2 (2011): 71-90.
[5] Xu, Wen, et al. "Maximum likelihood TOA and OTDOA estimation with first
arriving path detection for 3GPP LTE system." Transactions on Emerging
Telecommunications Technologies 27.3 (2016): 339-356.
[6] Faragher, Ramsey M., and Robert K. Harle. "Towards an efficient, intelligent, opportunistic smartphone indoor positioning system." NAVIGATION, Journal of the Institute of Navigation 62.1 (2015): 55-72.
[7] Misra, P., and P. Enge. "Global Positioning System: Signals, Measurements, and Performance, revised second ed." (2012).
[8] Parkinson, Bradford, et al. "A history of satellite navigation." Proceedings of the 51st Annual Meeting of The Institute of Navigation (1995). 1995.
[9] Maine, Kris, Carrie Devieux, and Pete Swan. "Overview of IRIDIUM satellite network." Proceedings of WESCON'95. IEEE, 1995.
[10] Dietrich, Fred J., Paul Metzen, and Phil Monte. "The Globalstar cellular satellite system." IEEE Transactions on antennas and propagation 46.6 (1998): 935-942.
[11] Hara, Todd. "ORBCOMM low earth orbit mobile satellite communication system: US Armed Forces applications." Proceedings of MILCOM'93-IEEE Military Communications Conference. Vol. 2. IEEE, 1993.
[12] "Orbcomm Communications Satellite Constellation," [Online]. Available: https://www.aerospace-technology.com/projects/orbcomm/. [Accessed 2021].
[13] Tan, Zizhong, et al. "New method for positioning using IRIDIUM satellite signals of opportunity." IEEE access 7 (2019): 83412-83423.
[14] Tan, Zizhong, et al. "Positioning Using IRIDIUM Satellite Signals of Opportunity in Weak Signal Environment." Electronics 9.1 (2020): 37.
[15] Hsu, Wu-Hung, and Shau-Shiun Jan. "Assessment of using Doppler shift of LEO satellites to aid GPS positioning." 2014 IEEE/ION Position, Location and Navigation Symposium-PLANS 2014. IEEE, 2014.
[16] Levanon, Nadav. "Quick position determination using 1 or 2 LEO satellites." IEEE Transactions on Aerospace and electronic Systems 34.3 (1998): 736-754.
[17] Levanon, Nadav. "Instant active positioning with one LEO satellite." Navigation 46.2 (1999): 87-95.
[18] Vasavada, Yash, et al. "User location determination using delay and Doppler measurements in LEO satellite systems." MILCOM 2017-2017 IEEE Military Communications Conference (MILCOM). IEEE, 2017.
[19] Khalife, Joe J., and Zaher M. Kassas. "Receiver design for Doppler positioning with LEO satellites." ICASSP 2019-2019 IEEE International Conference on Acoustics, Speech and Signal Processing (ICASSP). IEEE, 2019.
[20] Ardito, Christian T., et al. "Performance evaluation of navigation using LEO satellite signals with periodically transmitted satellite positions." Proceedings of the 2019 International Technical Meeting of The Institute of Navigation. 2019.
[21] Morales, Joshua J., et al. "Inertial navigation system aiding with Orbcomm LEO satellite Doppler measurements." Proceedings of the 31st International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GNSS+ 2018). 2018.
[22] Morales, Joshua, Joe Khalife, and Zaher M. Kassas. "Simultaneous tracking of Orbcomm LEO satellites and inertial navigation system aiding using Doppler measurements." 2019 IEEE 89th Vehicular Technology Conference (VTC2019-Spring). IEEE, 2019.
[23] Nguyen, Ngoc Hung, and Kutluyil Doğançay. "Algebraic solution for stationary emitter geolocation by a LEO satellite using Doppler frequency measurements." 2016 IEEE International Conference on Acoustics, Speech and Signal Processing (ICASSP). IEEE, 2016.
[24] Zhao, Junhui, Lei Li, and Yi Gong. "Joint navigation and synchronization in LEO dual-satellite geolocation systems." 2017 IEEE 85th Vehicular Technology Conference (VTC Spring). IEEE, 2017.
[25] Chen, Xi, Menglu Wang, and Lei Zhang. "Analysis on the performance bound of Doppler positioning using one LEO satellite." 2016 IEEE 83rd Vehicular Technology Conference (VTC Spring). IEEE, 2016.
[26] Ellis, Patrick, Donald Van Rheeden, and Farid Dowla. "Use of doppler and doppler rate for RF geolocation using a single LEO satellite." IEEE Access 8 (2020): 12907-12920.
[27] Lawrence, D., et al. "Navigation from LEO: Current capability and future
promise." GPS World Magazine 28.7 (2017): 42-48.
[28] Reid, Tyler G., et al. "Leveraging commercial broadband leo constellations for navigating." Proceedings of the 29th International Technical Meeting of the Satellite Di-vision of the Institute of Navigation (Ion Gnss+ 2016). 29th International Technical Meeting of the Satellite Division of the Institute of Navigation (Ion Gnss+ 2016), Portland, Oregon. Vol. 12. 2016.
[29] Zhu, Feng, et al. "Terminal location method with NLOS exclusion based on unsupervised learning in 5G‐LEO satellite communication systems." International Journal of Satellite Communications and Networking 38.5 (2020): 425-436.
[30] 莊智清, 電子導航: 全華科技, 2012.
[31] Myung, In Jae. "Tutorial on maximum likelihood estimation." Journal of mathematical Psychology 47.1 (2003): 90-100.
[32] "NORAD Two-Line Element Sets Current Data," [Online]. Available: https://celestrak.com/NORAD/elements/. [Accessed 2021].
[33] Ali, Irfan, Naofal Al-Dhahir, and John E. Hershey. "Doppler characterization for LEO satellites." IEEE transactions on communications 46.3 (1998): 309-313.
[34] Kay, Steven M., and Steven M. Kay. Fundamentals of statistical signal processing: estimation theory. Vol. 1. Englewood Cliffs, NJ: Prentice-hall, 1993.
[35] Chang, Cheng, and Anant Sahai. "Cramér-Rao-type bounds for localization." EURASIP Journal on Advances in Signal Processing 2006 (2006): 1-13.
[36] Levy, Larry J. "The Kalman filter: navigation's integration workhorse." GPS World 8.9 (1997): 65-71.
[37] Kalman, Rudolph Emil. "A new approach to linear filtering and prediction problems." (1960): 35-45.