可見光通訊技術 ( Visible Light Communication, VLC ) 是目前正在發展中一種傳遞資料的通訊技術。本文以光通訊不對稱剪裁正交分頻多工調變 ( ACO-OFDM ) 做為調變方法並結合扮演未來照明主流的 LED 燈具所發出來的光為媒介，探討室內資料傳輸的通訊技術。
VLC 可使用的頻寬 ( 400THz到790THz )，相較於射頻 ( 3kHz到300GHz ) 大很多，且具有快速脈衝響應。另外，其高度的傳輸安全性、隱蔽性，以及能適應於電磁波干擾環境，亦是它的優點之一。儘管 LED 具有高頻寬及快速脈衝響應的特性，但是傳輸距離的影響及傳輸環境中光的干擾，卻會造成傳送資料在傳遞中遭遇通道效應而產生誤差。因此解決通道所造成的失真，為本篇論文的研究重點。
本論文使用光通訊不對稱剪裁正交分頻多工調變做為調變方法，據以設計可見光通訊的同步以及 DHT-based 等化器。對同步符碼偏移和時脈偏移之估測及補償與等化器通道之估測及資料補償，提出有效解決方法。本論文提出使用哈特利轉換指數型增益和相角之自動增益控制與載波回復頻域等化器 ( AGC-CR ) 電路結合可外部控制增益座標軸數位旋轉計數器電路，以 Matlab 與C 語言模擬，並以 Verilog 硬體描述語言實現電路最後使用 TSMC-90 nm 製程來實現所設計之電路，以驗證所提出之電路設計措施的有效性。

Visible Light Communication (VLC) is a developing communications technology for data delivery. This paper uses ACO-OFDM as modulation combining with the light form LED lighting applications, which are likely to become the predominant lighting equipment in the future.
　　 The bandwidth that which VLC uses (400THz~790THz) is wider than RF (3kHz~300GHz) and VLC also has a fast impulse response. Other advantages of VLC include high security of transmission and adaptability to Electro Magnetic Interference. However, even though VLC has a wider bandwidth and a fast impulse response, it can be interfered by distance and surrounding light during transmission. Thus, it will cause error during data transmission when channel effects occur. In particular, this paper focuses on solving distortion caused by the channel effects.
　　This paper uses ACO-OFDM as modulation, designing a Visible Light Communication Synchronization and DHT-based Equalizer. Providing an effective solution to symbol boundary detection, and the estimation and compensate of sampling clock offset, and the channel effect detection and data recovering of frequency equalizer. This research proposes combining using Discrete Hartley transform to Auto-gain control and Carrier recovery (AGC-CR) with exponential gain and phase against Modified Gain Control-Coordinate Rotation Digital Computer (MGC-CORDIC). Simulations are done by using Matlab and C language, along with utilized Verilog HDL to design the circuit, and realizing the proposed circuit in TSMC-90nm to verify the performance.

[1] J. Armstrong and A. J. Lowery, "Power efficient optical OFDM, "Electron. Lett., vol. 42, issue 6. pp. 370-372, 16 March 2006.
[2] J. Lowery, L. B. Du, and J. Armstrong, “Performance of optical OFDM in ultralong-haul WDM lightwave systems,” J. Lightw. Technol., vol. 25, no. 1, pp. 131–138, Jan. 2008.
[3] J. Armstrong and B. J. C. Schmidt, "Comparison of asymmetrically clipped optical OFDM and DC-biased optical OFDM in AWGN," IEEE Communications Letters, vol. 12, pp. 343-345, 2008.
[4] J. Armstrong and B. J. C. Schmidt, “Comparison of asymmetrically clipped optical OFDM and DC-biased optical OFDM in AWGN,” IEEE Commun. Lett., vol. 12, pp. 343–345, 2008.
[5] F. Delgado, I. Quintana, J. Rufo, J.A. Rabadan, Crisanto Quintana, and R. Perez-Jimenez, “ Design and Implementation of an Ethernet-VLC Interface for Broadcast Transmissions,” IEEE COMMUNICATIONS LETTERS, VOL. 14, NO. 12, DECEMBER 2010.
[6] 蕭建堯, “應用於可見光通訊之OFDM接收機設計與實現,” 中央大學, 電機工程學系碩士論文, 2014.
[7] H. Elgala†, R. Mesleh† and H. Haas†*, “Practical Considerations for Indoor Wireless Optical System Implementation using OFDM,” Institute for Digital Communications, Joint Research Institute for Signal and Image Processing.
[8] Jian Dang, Zaichen Zhang, and Liang Wu, “A Novel Receiver for ACO-OFDM in Visible Light Communication,” IEEE Communications Letters, Accepted for publication.
[9] Liang Chen, Brian Krongold and Jamie Evans, “Performance Evaluation of Optical OFDM Systems with Nonlinear Clipping Distortion,” IEEE Communications Society subject matter experts for publication in the IEEE ICC 2009 proceedings
[10] Svilen Dimitrov, Sinan Sinanovic and Harald Haas,” Double-sided Signal Clipping in ACO-OFDM Wireless Communication Systems,” IEEE Communications Society subject matter experts for publication in the IEEE ICC 2011 proceedings.
[11] D. Matiae, “OFDM as a possible modulation technique for multimedia application in the range of mm wave,” TUD-TVS, Oct. 1998
[12] Peled and A. Ruiz, “Frequency domain data transmission using reduced computational complexity algorithms,” in Proc. IEEE International Conference on ICASSP, vol. 5, April, 1980, pp. 964-967.
[13] Kwonhyung Lee and Hyuncheol Park, “Channel Model and Modulation Schemes for Visible Light Communications,” IEEE Circuits and Systems (MWSCAS), 2011 IEEE 54th International Midwest Symposium, 7-10 Aug. 2011.
[14] Michael Speth, Stefan A. Fechtel, Gunnar Fock, and Heinrich Meyr, “Optimum Receiver Design for Wireless Broad-Band Systems Using OFDM—Part I,” IEEE Transactions on Communications, Vol.47, no. 11, November 1999.
[15] Floyd M. Gardner, “Interpolation in Digital Modems – Part II: Implementation and Performance,” IEEE Transactions on communications VOL. 41, NO. 6, June 1993.
[16] Floyd M. Gardner, “Interpolation in Digital Modems – Part II: Implementation and Performance,” IEEE Transactions on communications VOL. 41, NO. 6, June 1993.
[17] R. Andraka, “A survey of CORDIC algorithms for FPGA based computers,” Andraka Consulting Group, Inc, North Kingstown, 1998.
[18] 陳右昀, “應用於PLC系統之AGC-CR通道等化技術,” 中央大學, 電機工程學系碩士論文, 2008.
[19] P. B. Denyer and D. Renshaw, “VLSI Signal Processing; A Bit-Serial Approach,” Addison-Wesley Longman Publishing Co., Boston, MA, USA, 1985.
[20] Xie Zhang, Kaiyun Cui, Minyu Yao, Hongming Zhang, Zhengyuan Xu, “Experimental Characterization of Indoor Visible Light Communication Channels,” Communication Systems, Networks & Digital Signal Processing (CSNDSP), Poznan, 2012.
[21] Chih-Feng Wu, Muh-Tian Shiue, Chrong-Kuang Wang, “DHT-Based Frequency-Domain Equalizer for DMT Systems,” 13th European Signal Processing Conference, September 4-8, 2005 Antalya, EUSIPCO 2005.
[22] Ching-Yuan Yang and Yu Lee, “A PWM and PAM signaling hybrid technology for serial-link Transceivers,” IEEE Transaction Instrumentation and Measurement (USA), 57, 1058–1070.
[23] H. Elgala , R. Mesleh , H. Haas and B. Pricope, “OFDM Visible Light Wireless Communication Based on White LEDs,” Proc. of the 64th IEEE Vehicular Technology Conference (VTC), pp.2185 -2189 2007
[24] J.-H. Choi, E.-B. Cho, T.-G. Kang, and C. G. Lee, “Pulse width modulation based signal format for visible light communications,” Technical Digest of 15th Optoelectronics and Communications Conference (OECC 2010), Sapporo, Japan, pp. 276-277, 2010.
[25] M. Z. Afgani , H. Haas , H. Elgala and D. Knipp, “Visible light communication using OFDM,” Proc. IEEE 2nd Int. Conf. Testbeds Res. Infrastructures Develop. Netw. Communities, pp.129 -134 2006.
[26] T. Komine and M. Nakagawa, “Fundamental analysis for visible-light communication system using LED lightings,” IEEE Trans. Consum. Electron., vol. 50, no. 1, pp.100 -107 2004.
[27] Y. Tanaka , T. Komine, S. Haruyama and M. Nakagawa, “Indoor visible communication utilizing plural white LEDs as lighting,” Proc. 12th IEEE Int. Symp. Pers. Indoor Mobile Radio Commun., vol. 2, pp.81 -85 2001.
[28] J. R. Barry, “Wireless Infrared Communications,” Kluwer Academic Publishers, 1994.
[29] H. Park and J. R. Barry, “Modulation analysis for wireless infrared communications,” Proc. IEEE Int. Conf. Communications, Seattle, WA, Jun. 1995.
[30] 陳培炘, “利用實數運算核心之哈特萊轉換OFDM調變/解調變器,” 中央大學, 電機工程學系碩士論文, 2008.
[31] J. Grubor , S. Randel , K. D. Langer and J. W. Walewski, “Broadband information broadcasting using LED-based interior lighting,” J. Lightw. Technol., vol. 26, no. 24, pp.3883 -3892 2008.
[32] T. Komine, J. H. Lee, S. Haruyama, and M. Nakagawa, “Adaptive equalization system for visible light wireless communication utilizing multiple white LED lighting equipment,” IEEE Trans. Wireless Commun., vol. 8, no. 6, Jun. 2009.
[33] G. A. Mahdiraji and E. Zahedi, “Comparison of selected digital modulation schemes (OOK, PPM and DPIM) for wireless optical communications,” in SCOReD Conference, June 2006, pp. 5-10, Selangor, Malaysia.
[34] Rakhi Thakur, Kavita Khare et al, “Frame Detection For Synchronization In OFDM,” International Journal of Engineering Science and Technology (IJEST) Vol. 3 No. 7 July 2011pp 5955-5957.
[35] Hany Elgala, Student Member, IEEE, Raed Mesleh, Member, IEEE and Harald Haas, Member, IEEE, “Indoor Broadcasting via White LEDs and OFDM,” IEEE Transactions on Consumer Electronics, Vol. 55, No. 3, AUGUST 2009.
[36] Toshihiko Komine, Student Member, IEEE, and Masao Nakagawa, Member, IEEE “Fundamental Analysis for Visible-Light Communication System using LED Lights,” IEEE Transactions on Consumer Electronics, Vol. 50, No. 1, FEBRUARY 2004