水下无线光通信系统研究及其 FPGA 实现

相比于传统的水下无线系统，水下无线光通信（UWOC）展示出了其多方面的优势，诸如具有高带宽、高传输速率、抗干扰能力强、低延时、低功耗以及安全好等，对满足未来实时，高带宽高速率要求下的水下无线通信提供了极具潜力的技术方案。有效地优化水下无线光通信系统，提升系统传输速率以及适配具体场景的应用，对研究水下无线光通信有非常重要的意义。目前，水下无线光通信已成为海洋探测系统的重要技术之一，对其通信速率和系统结构性能的研究引起了国内外众多学者的关注。

本文主要从水下光通信系统的光源、调制方案以及系统硬件设计与实现来展开实践研究。作为热门且性能优异的发光器件，Micro-LED有着电流密度高、发光效率高以及响应速度快等优势，适合水下光通信系统的搭建。根据实验制备高性能Micro-LED光源器件，并结合开发灵活的现场可编程门阵列（FPGA）芯片，设计并搭建了脉冲位置调制（PPM）方案和正交频分复用调制（OFDM）方案的水下无线光通信系统。在文章中，测试Micro-LED等光源性能，获得单颗Micro-LED的最高-3dB调制带宽为177MHz。其次，阐述了系统实现的框架，并利用Xilinx的ISE开发软件设计PPM方案的系统各模块，其中包括误差测试模块。利用仿真软件对FPGA发射机和接收机的实现结果进行了验证。通过仿真和实验测试，我们实现并演示了一个基于FPGA的50Mbps UWOC系统，该系统采用PPM调制方案并利用Micro-LED作为光源。此外，提出了以Micro-LED作为光源的OFDM调制的UWOC系统设计方案，并参照IEEE802.11a协议规定对系统发射端和接收端的各个模块进行设计。由仿真和验证结果可得，该OFDM调制方案的系统在信号传输为32Mbps下各模块功能均可正确工作。

[1] 毕重人. 我国海洋传统优势产业转型升级问题研究[D]. 北京交通大学, 2020.
[2] 孙久文, 高宇杰. 中国海洋经济发展研究[J]，区域经济评论, 2021(01): 38-47.
[3] 韩东, 贺寅, 陈立军, et al. 水下通信技术及其难点[J]，科技创新与应用, 2021(01): 155-159.
[4] Murgod T R, Sundaram S M. Survey on underwater optical wireless communication: perspectives and challenges[J]. Indonesian Journal of Electrical Engineering and Computer Science, 2019, 13(1): 138.
[5] Zhaoquan Z, Shu F, Huihui Z, et al. A Survey of Underwater Optical Wireless Communications[J]. COMST, 2017, 19(1): 204-238.
[6] Liu Tengda Z H U J Z Y. Review on FPGA-Based Accelerators in Deep Learning[J]. Jisuanji kexue yu tansuo, 2021, 15(11): 2093-2104.
[7] Shan J, Lazarescu M T, Cortadella J, et al. Fast Energy-Optimal Multikernel DNN-Like Application Allocation on Multi-FPGA Platforms[J]. TCAD, 2022, 41(4): 1186-1190.
[8] Srinivasa Rao P, Yedukondalu K. Hardware implementation of digital image skeletonization algorithm using FPGA for computer vision applications[J]. Journal of visual communication and image representation, 2019, 59: 140-149.
[9] 揭应平. FPGA芯片设计及其应用分析[J]. Applications of IC, 2017, 34(12): 37-41.
[10] 田雨晨. FPGA芯片设计及其应用[J]. 数字通信世界, 2019(4): 228.
[11] Cox W C, Jr. A 1 Mbps Underwater Communication System Using a 405 nm Laser Diode and Photomultiplier Tube, 2008.
[12] Simpson J A, Cox W C, Krier J R, et al. 5 Mbps optical wireless communication with error correction coding for underwater sensor nodes: IEEE, 2010: 1-4.
[13] Nakamura K, Mizukoshi I, Hanawa M. Optical wireless transmission of 405 nm, 1.45 Gbit/s optical IM/DD-OFDM signals through a 4.8 m underwater channel[J]. OPT EXPRESS, 2015, 23(2): 1558-1566.
[14] Jingpeng L, Zhaorui G, Bing Z, et al. A design of underwater wireless laser communication system based on PPM modulating method: IEEE, 2016: 1-6.
[15] 林奥博. 基于FPGA的水下OFDM无线可见光通信系统[D]. 浙江大学, 2017.
[16] Wang P, Li C, Xu Z. A Cost-Efficient Real-Time 25 Mb/s System for LED-UOWC: Design, Channel Coding, FPGA Implementation, and Characterization[J]. JLT, 2018, 36(13): 2627-2637.
[17] Wang J, Tian C, Yang X, et al. Underwater wireless optical communication system using a 16-QAM modulated 450-nm laser diode based on an FPGA[J]. Appl Opt, 2019, 58(16): 4553.
[18] Li J, Yang B, Ye D, et al. A Real-Time, Full-Duplex System for Underwater Wireless Optical Communication: Hardware Structure and Optical Link Model[J]. Access, 2020, 8: 109372-109387.
[19] Zhang Y, Zhang M, Zhou H, et al. A Long Distance Real-time DPSK Visible Light Communication System Based on FPGA[C]. 2019 18th International Conference on Optical Communications and Networks (ICOCN), 2019: 1-3.
[20] Pramono S, Hamka M, Hanifa A, et al. Design and Development of Bit Error Measurement using FPGA for Visible Light Communication[J], 2021.
[21] Kang J, Wang L, Yue C P. Design of a Real-Time Visible Laser Light Communication System with Basedband in FPGA for High Definition video Transmission: IEEE, 2019: 179-180.
[22] Qingyuan H, Min Z, Weishu X, et al. FPGA-based 120Mbps online visible light communication system with RGB LEDs: IEEE, 2016: 1-3.
[23] Farhat Z A, Ahfayd M H, Mather P J, et al. Practical implementation of duobinary pulse position modulation using FPGA and visible light communication: IEEE, 2017: 253-256.
[24] Lu M, Xiao S, Zhang L, et al. Real-time VLC system integrated with positioning beacon transmission based on 2ASK-CE-OFDM coding[J]. Optics communications, 2019, 452: 252-257.
[25] Lihui Y, Min W, Junfei F, et al. The high-speed optical OFDM transmitter based on FPGA. Stevenage, UK: Stevenage, UK: IET, 2013: 368-371.
[26] Ahfayd M H, Farhat Z A, Sibley M J N, et al. Visible light communication based system using high power LED and dicode pulse position modulation technique: IEEE, 2017: 1-4.
[27] Aobo L, Weichao L, Jing X, et al. Underwater wireless optical communication using a directly modulated semiconductor laser: IEEE, 2015: 1-4.
[28] Xu J, Lin A, Yu X, et al. Underwater Laser Communication Using an OFDM-Modulated 520-nm Laser Diode[J]. LPT, 2016, 28(20): 2133-2136.
[29] Oubei H M, Duran J R, Janjua B, et al. 4.8 Gbit/s 16-QAM-OFDM transmission based on compact 450-nm laser for underwater wireless optical communication[J]. OPT EXPRESS, 2015, 23(18): 23302-23309.
[30] Richard W. Spinrad K L C M J P. Ocean optics [electronic resource][M]. New York : Oxford: New York : Oxford University PressOxford : Clarendon Press, 1994, 1994.
[31] Anguita D, Brizzolara D, Parodi G, et al. Optical wireless underwater communication for AUV: Preliminary simulation and experimental results[C]: 1-5.
[32] Morel A, Gentili B, Claustre H, et al. Optical Properties of the "Clearest" Natural Waters[J]. Limnology and oceanography, 2007, 52(1): 217-229.
[33] Duntley S Q J J O T O S O A. Light in the Sea[J], 1963, 53(2): 214-233.
[34] Saeed N, Celik A, Al-Naffouri T Y, et al. Underwater optical wireless communications, networking, and localization: A survey[J]. Ad hoc networks, 2019, 94: 101935.
[35] He G, Lv Z, Qiu C, et al. Performance Evaluation of 520nm Laser Diode Underwater Wireless Optical Communication Systems in the Presence of Oceanic Turbulence[J]. SID International Symposium Digest of technical papers, 2020, 51(S1): 47-50.
[36] Ji R, Wang S, Liu Q, et al. High-Speed Visible Light Communications: Enabling Technologies and State of the Art[J]. Applied sciences, 2018, 8(4): 589.
[37] He G, Lv Z, Qiu C, et al. 21.3: The Influence of NLOS on Underwater Wireless Optical Communication System Using an InGaN‐based Micro‐LED and NRZ‐OOK Modulation[J]. SID International Symposium Digest of technical papers, 2021, 52(S2): 286-288.
[38] Chi N, Shi M, Zhao Y, et al. LED-based high-speed visible light communications[C]: 105590I-105590I-8.
[39] Gabriel C, Khalighi M, Bourennane S, et al. Investigation of suitable modulation techniques for underwater wireless optical communication[C]: 1-3.
[40] 丁凌琦 穆道生 蒋. OFDM技术应用现状分析[J]. Computer Engineering & Software, 2016, 37(10): 130-134.
[41] 张万东 戴鸿鹏 刘理 陈. 4G通信系统中OFDM技术的分析[J]. Telecom World, 2017(20): 9-10.
[42] Simon J, Prabakaran N. Optimal wavelets with Binary Phase Shift Keying modulator utilized simulation analysis of 4G/5G OFDM systems[J]. INT J COMMUN SYST, 2021, 34(9): n/a.
[43] 杨昉. OFDM原理与标准 : 通信技术的演进[M]. 北京: 北京 : 电子工业出版社,2013, 2013.
[44] Huang Y, Hsiang E-L, Deng M-Y, et al. Mini-LED, Micro-LED and OLED displays: present status and future perspectives[J]. Light, science & applications, 2020, 9(1): 105-105.
[45] Lin R, Liu X, Zhou G, et al. InGaN Micro‐LED Array Enabled Advanced Underwater Wireless Optical Communication and Underwater Charging[J]. Advanced optical materials, 2021, 9(12): 2002211-n/a.
[46] Liu Z, Lin C-H, Hyun B-R, et al. Micro-light-emitting diodes with quantum dots in display technology[J]. Light Sci Appl, 2020, 9(1): 83-83.
[47] IEEE Standard for Telecommunications and Information Exchange Between Systems - LAN/MAN Specific Requirements - Part 11: Wireless Medium Access Control (MAC) and physical layer (PHY) specifications: High Speed Physical Layer in the 5 GHz band[J]. IEEE Std 802.11a-1999, 1999: 1-102.