近年來，人們逐漸依賴室內定位及導航技術，定位的需求及應用也越來越多，因此，定位的精準度是非常重要的，必須解決發射器與接收器之間的量測誤差，當訊號受到多重路徑干擾 (Multipath Interference) 的影響，所量測的訊號抵達時間將會比實際訊號抵達時間還要長，這將會造成訊號抵達時間容易被誤差所影響並降低定位準確性，為了解決這些問題，我們透過建構一個簡單且便宜的室內光波定位來實現高精準度室內定位。

因為室內環境中不能沒有燈光，而且展頻碼 (Spread Spectrum Code) 可以用來做抗雜訊的機器人定位，所以在本研究當中，我們利用最大長度序列碼 (M-sequence code) 來實現室內光波定位系統，透過發光二極體的閃爍將不同發射器的訊號調變成最大長度序列碼，利用訊號擷取技術去得到每一個發射器與機器人之間的訊號飛行時間，然後挑選相對比較近的三個發射器當作定位資訊，透過訊號抵達時間差 (Time Difference of Arrival, TDOA) 計算出機器人可能位置，再藉由基因演算法 (Genetic Algorithm, GA) 來得到更精準的機器人位置。最後再進一步分析並探討最大長度序列編碼擷取功能對定位精確度的影響。

In recent years, people gradually dependent on indoor positioning and navigation. The demands and applications of positioning are becoming more and more. Therefore, the accuracy of positioning is very important, and the measurement error between transmitters and receiver must be solved. As the interference of multipath, the estimated signal arrival-time will be larger than real signal arrival-time. As the result, the signal arrival-time is easily influenced by errors and decreases the accuracy of positioning. In order to solve the problems, we through construct a simple and cheap indoor lightwave positioning to implement the high precision indoor positioning.

Because the indoor environment cannot without lighting and Spread Spectrum codes can locate the position of the robot receiver against noise interference. In our research, we used maximal-length sequence code (M-sequence code) to achieve indoor lightwave positioning system. The signals from different transmitters will be modulated into a series of maximal-length sequence code by LED light blinking. Using signal acquisition technique to obtain the time of flight between each transmitter and the robot receiver. Then choosing three transmitters among five closest to the robot for more reliable positioning information. The robot positioning is first calculated by Time Difference of Arrival (TDOA) and then GA optimization is applied for more accurate robot location. Finally, the effects of access function of M-sequence codes on positioning accuracy are further analyzed.

[1] K. Deepika and J. Usha, "Investigations and implications on location tracking using RFID with Global Positioning Systems, " 3rd International Conference on Computer and Information Sciences (ICCOINS), Kuala Lumpur, pp. 242-247, August 2016.
[2] Evennou, Frédéric, and François Marx, "Advanced integration of WiFi and inertial navigation systems for indoor mobile positioning," Eurasip journal on applied signal processing, pp. 164-164, January 2006.
[3] S. S. Saab and Z. S. Nakad, "A Standalone RFID Indoor Positioning System Using Passive Tags," IEEE Transactions on Industrial Electronics, vol. 58, no. 5, pp. 1961-1970, May 2011.
[4] Y. Wang, Xu Yang, Yutian Zhao, Yue Liu and L. Cuthbert, "Bluetooth positioning using RSSI and triangulation methods," the 10th IEEE Consumer Communications and Networking Conference (CCNC), Las Vegas, NV, pp. 837-842, January 2013.
[5] M. Hazas and A. Hopper, "Broadband ultrasonic location systems for improved indoor positioning," IEEE Transactions on Mobile Computing, vol. 5, no. 5, pp. 536-547, May 2006.
[6] E. Aitenbichler and M. Muhlhauser, "An IR local positioning system for smart items and devices," the 23rd International Conference on Distributed Computing Systems Workshops, pp. 334-339, May 2003.
[7] Kuo Wen-Hsing et al., "An intelligent positioning approach: RSSI-based indoor and outdoor localization scheme in ZigBee networks," IEEE International Conference on Machine Learning and Cybernetics, vol. 6, pp. 2754-2759, July 2010.
[8] S. Gezici et al., "Localization via ultra-wideband radios: a look at positioning aspects for future sensor networks," IEEE Signal Processing Magazine, vol. 22, no. 4, pp. 70-84, July 2005.
[9] T. Gigl, G. J. M. Janssen, V. Dizdarevic, K. Witrisal and Z. Irahhauten, "Analysis of a UWB Indoor Positioning System Based on Received Signal Strength," the 4th Workshop on Positioning, Navigation and Communication, Hannover, pp. 97-101, March 2007.
[10] Zhang, Weizhi, MI Sakib Chowdhury, and Mohsen Kavehrad. "Asynchronous indoor positioning system based on visible light communications." Optical Engineering, vol. 53, no. 4, pp. 045105-1~045105-9, April 2014.
[11] Ye-Sheng Kuo, Pat Pannuto, Ko-Jen Hsiao, and Prabal Dutta. “Luxapose: indoor positioning with mobile phones and visible light,” Mobile Computing and Networking, pp. 447-458, September 2014.
[12] H. Liu, H. Darabi, P. Banerjee and J. Liu, "Survey of Wireless Indoor Positioning Techniques and Systems," IEEE Transactions on Systems, Man, and Cybernetics, Part C (Applications and Reviews), vol. 37, no. 6, pp. 1067-1080, Nov. 2007.
[13] Y. Itagaki, A. Suzuki and T. Iyota, "Indoor positioning for moving objects using a hardware device with spread spectrum ultrasonic waves," International Conference on Indoor Positioning and Indoor Navigation (IPIN), Sydney, NSW, pp. 1-6 , November 2012.
[14] Trong-Hop Do, and Myungsik Yoo. "TDOA-based indoor positioning using visible light." Photonic Network Communications, vol. 27, no.2, pp. 80-88, January 2014.
[15] M. N. Borenovic, M. I. Simic, A. M. Neskovic, M. M. Petrovic, “Enhanced Cell-ID + TA GSM Positioning Technique,” Int. Conf. on in Computer as a Tool, vol. 2, pp. 1176-1179, Nov. 2005.
[16] K. Kaemarungsi and P. Krishnamurthy, "Properties of indoor received signal strength for WLAN location fingerprinting," the 1st International Conference on Mobile and Ubiquitous Systems: Networking and Services, MOBIQUITOUS, pp. 14-23, August 2004.
[17] S. Mazuelas et al., "Robust Indoor Positioning Provided by Real-Time RSSI Values in Unmodified WLAN Networks," IEEE Journal of Selected Topics in Signal Processing, vol. 3, no. 5, pp. 821-831, Oct. 2009.
[18] D. Niculescu and Badri Nath, "Ad hoc positioning system (APS) using AOA," the 22nd Annual Joint Conference of the IEEE Computer and Communications Societies (IEEE INFOCOM), vol. 3, pp. 1734-1743, April 2003.
[19] Dempster, A. G., "Dilution of precision in angle-of-arrival positioning systems." Electronics Letters, vol. 42, no. 5, pp. 291-292, March 2006.
[20] Shen, Junyang, Andreas F. Molisch, and Jussi Salmi, "Accurate passive location estimation using TOA measurements," IEEE Transactions on Wireless Communications, vol. 11, no. 6, pp. 2182-2192, June 2012.
[21] Thomas Q. Wang, Y. Ahmet Sekercioglu, Adrian Neild, and Jean Armstrong, “Position accuracy of time-of-arrival based ranging using visible light with application in indoor localization systems,” IEEE journal of Lightwave Technology, vol. 31, no. 20, Oct. 2013.
[22] S. Li, J. Hua, G. Zhong, W. Lu and B. Jiang, "A TSOA based localization algorithm in wireless networks," the 11th IEEE Conference on Industrial Electronics and Applications (ICIEA), Hefei, pp. 526-530, June 2016.
[23] A. Makki, A. Siddig, M. Saad, J. R. Cavallaro, and C. J. Bleakley, "Indoor Localization Using 802.11 Time Differences of Arrival," IEEE Transactions on Instrumentation and Measurement, vol. 65, no. 3, pp. 614-623, March 2016.
[24] S. Y. Jung, S. Hann, and C. S. Park, "TDOA-based optical wireless indoor localization using LED ceiling lamps," IEEE Transactions on Consumer Electronics, vol. 57, no. 4, pp. 1592-1597, November 2011.
[25] J. K. Werner and B. Markus, “Using Pseudo-random Codes for Mobile Robot Sonar Sensing,” the 3rd IFAC Symposium on Intelligent Autonomous Vehicles (IAV’98), Madrid, Spain, pp. 231-236, March 25-27, March 1998.
[26] E. Trevisani and A. Vitaletti, “Cell-ID location technique, limits and benefits: an experimental study,” Proc. IEEE Workshop on Mobile Computing Systems and Applications, pp. 51-60, Dec. 2004.
[27] W. H. Foy, “Position-location solutions by Taylor series estimation,” IEEE Transactions on Aerospace and Electronic Systems, vol. AES-12, no. 2, pp. 187-194, Mar. 1976.
[28] S. Venkatraman and J. Caffery, “Hybrid TOA/AOA techniques for mobile location in non-line-of-sight environments,” IEEE Wireless Communications and Networking Conference, pp. 274-278 Vol.1, March 2004.
[29] D. Torrieri, “Statistical theory of passive location systems,” IEEE Trans. Aerosp. Electron. Syst., vol. AES-20, pp. 183–197, Mar. 1984.
[30] Yanrong Hu and S. X. Yang, "A knowledge based genetic algorithm for path planning of a mobile robot," Proceedings IEEE International Conference on Robotics and Automation (ICRA '04), vol. 5, pp. 4350-4355, April 2004.
[31] Romoozi, Mojtaba, and Hossein Ebrahimpour-Komleh, "A positioning method in wireless sensor networks using genetic algorithms," Physics Procedia, vol. 33, pp. 1042-1049, May 2012.