TRANSMISSION PERFORMANCE OPTIMIZATION IN FIBER-WIRELESS ACCESS NETWORKS USING MACHINE LEARNING TECHNIQUES

The objective of this dissertation is to enhance the transmission performance in the fiber-wireless access network through mitigating the vital system limitations of both analog radio over fiber (A-RoF) and digital radio over fiber (D-RoF), with machine learning techniques being systematically implemented. The first thrust is improving the spectral efficiency for the optical transmission in the D-RoF to support the delivery of the massive number of bits from digitized radio signals. Advanced digital modulation schemes like PAM8, discrete multi-tone (DMT), and probabilistic shaping are investigated and implemented, while they may introduce severe nonlinear impairments on the low-cost optical intensity-modulation-direct-detection (IMDD) based D-RoF link with a limited dynamic range. An efficient deep neural network (DNN) equalizer/decoder to mitigate the nonlinear degradation is therefore designed and experimentally verified. Besides, we design a neural network based digital predistortion (DPD) to mitigate the nonlinear impairments from the whole link, which can be integrated into a transmitter with more processing resources and power than a receiver in an access network. Another thrust is to proactively mitigate the complex interferences in radio access networks (RANs). The composition of signals from different licensed systems and unlicensed transmitters creates an unprecedently complex interference environment that cannot be solved by conventional pre-defined network planning. In response to the challenges, a proactive interference avoidance scheme using reinforcement learning is proposed and experimentally verified in a mmWave-over-fiber platform. Except for the external sources, the interference may arise internally from a local transmitter as the self-interference (SI) that occupies the same time and frequency block as the signal of interest (SOI). Different from the conventional subtraction-based SI cancellation scheme, we design an efficient dual-inputs DNN (DI-DNN) based canceller which simultaneously cancels the SI and recovers the SOI.Ph.D

Wideband QAM-over-SMF/turbulent FSO downlinks in a PON architecture for ubiquitous connectivity

[EN] We propose and investigate for the first time a seamless millimeter-wave (mmW) radio-over-fiber (RoF) and radio-over-free-space optics (FSO)-based downlink for use in a passive optical network architecture using 4-, 16- and 64-quadrature amplitude modulation (QAM) for broadband wireless access (BWA) networks. The proposed system is implemented in both experiment and simulation to realize continuous and ubiquitous coverage in urban and rural areas. We outline, a proof-of-concept demonstration of 4-, 16- and 64-QAMs at data rates of 34, 67 and 100 Mb/s, respectively transmitted over a 15 km standard single-mode fiber (SMF), which is then optically up-converted to 25 GHz for transmission over a 10 km of SMF and a 2 m of FSO channel under a non-uniform turbulent condition. We show the measured error vector magnitude (EVM) values of 13, 9.2 and 7.3% for 4-, 16- and 64-QAM, respectively, which are below the corresponding standard EVM requirements and therefore confirm the practicality of the proposed hybrid system. Depending on the data rates, each modulation can be adaptively configured. We report a simulation of a 10 Gb/s 4- and 64-QAM hybrid RoF-FSO downlink under an extended non-uniform turbulence regime to verify the feasibility of the proposed scheme for use in practical applications. By implementing the decision-directed carrier phase recovery and linear electrical equalization, EVMs can be efficiently reduced below the required limits. We further evaluate the proposed system performance in terms of the bit error rates, constellation diagrams, received optical and mmW powers. Using state-of-the-art K-band power amplifiers and conical horn antennas, the maximum wireless transmission distance is estimated to be about 135 m for use in the last-mile BWA networks.This work was supported in part by the Ministry of Education, Youth and Sports of Czech Republic (CZ.02.2.69/0.0/0.0/16_027/0008465), and in part by European Cooperation in Science and Technology COST CA16220 and CTU project SGS20/166/OHK3/3T/13.Nguyen, D.; Vallejo-Castro, L.; Bohata, J.; Ortega Tamarit, B.; Ghassemlooy, Z.; Zvanovec, S. (2020). Wideband QAM-over-SMF/turbulent FSO downlinks in a PON architecture for ubiquitous connectivity. Optics Communications. 475:1-9. https://doi.org/10.1016/j.optcom.2020.126281S19475Li, X., Yu, J., Zhang, Z., Xiao, J., & Chang, G.-K. (2015). Photonic vector signal generation at W-band employing an optical frequency octupling scheme enabled by a single MZM. Optics Communications, 349, 6-10. doi:10.1016/j.optcom.2015.03.044Kawanishi, T. (2019). THz and Photonic Seamless Communications. Journal of Lightwave Technology, 37(7), 1671-1679. doi:10.1109/jlt.2019.2897042Li, X., Yu, J., & Chang, G.-K. (2020). Photonics-Aided Millimeter-Wave Technologies for Extreme Mobile Broadband Communications in 5G. Journal of Lightwave Technology, 38(2), 366-378. doi:10.1109/jlt.2019.2935137Wang, H.-Y., Cheng, C.-H., Tsai, C.-T., Chi, Y.-C., & Lin, G.-R. (2019). 28-GHz Wireless Carrier Heterodyned From Orthogonally Polarized Tri-Color Laser Diode for Fading-Free Long-Reach MMWoF. Journal of Lightwave Technology, 37(13), 3388-3400. doi:10.1109/jlt.2019.2916787Khalighi, M. A., & Uysal, M. (2014). Survey on Free Space Optical Communication: A Communication Theory Perspective. IEEE Communications Surveys & Tutorials, 16(4), 2231-2258. doi:10.1109/comst.2014.2329501. KORUZA Transceivers, [Online]. Available: http://www.koruza.net/.Dat, P. T., Bekkali, A., Kazaura, K., Wakamori, K., Suzuki, T., Matsumoto, M., … Komaki, S. (2009). Studies on characterizing the transmission of RF signals over a turbulent FSO link. Optics Express, 17(10), 7731. doi:10.1364/oe.17.007731Y. Alfadhli, et al. Real-time FPGA demonstration of hybrid bi-directional MMW and FSO fronthaul architecture, in: 2019 Optical Fiber Communications Conference and Exhibition, OFC 2019 - Proceedings, 2019, p. W2A.39.P.T. Dat, A. Kanno, K. Inagaki, T. Umezawa, N. Yamamoto, T. Kawanishi, Hybrid optical wireless-mmWave: ultra high-speed indoor communications for beyond 5G, in: IEEE INFOCOM 2019 - IEEE Conference on Computer Communications Workshops, INFOCOM WKSHPS, 2019, pp. 1003–1004.Esmail, M. A., Ragheb, A., Fathallah, H., & Alouini, M.-S. (2017). Investigation and Demonstration of High Speed Full-Optical Hybrid FSO/Fiber Communication System Under Light Sand Storm Condition. IEEE Photonics Journal, 9(1), 1-12. doi:10.1109/jphot.2016.2641741Nguyen, D.-N., Bohata, J., Komanec, M., Zvanovec, S., Ortega, B., & Ghassemlooy, Z. (2019). Seamless 25 GHz Transmission of LTE 4/16/64-QAM Signals Over Hybrid SMF/FSO and Wireless Link. Journal of Lightwave Technology, 37(24), 6040-6047. doi:10.1109/jlt.2019.2945588Vallejo, L., Komanec, M., Ortega, B., Bohata, J., Nguyen, D.-N., Zvanovec, S., & Almenar, V. (2020). Impact of Thermal-Induced Turbulent Distribution Along FSO Link on Transmission of Photonically Generated mmW Signals in the Frequency Range 26–40 GHz. IEEE Photonics Journal, 12(1), 1-9. doi:10.1109/jphot.2019.2959227Alimi, I. A., Teixeira, A. L., & Monteiro, P. P. (2018). Toward an Efficient C-RAN Optical Fronthaul for the Future Networks: A Tutorial on Technologies, Requirements, Challenges, and Solutions. IEEE Communications Surveys & Tutorials, 20(1), 708-769. doi:10.1109/comst.2017.2773462N. Iiyama, S.-Y. Kim, T. Shimada, S. Kimura, N. Yoshimoto, Co-existent downstream scheme between OOK and QAM signals in an optical access network using software-defined technology, in: OFC/NFOEC 2012 - Optical Fiber Communication and the National Fiber Optic Engineers Conference, vol. 1, 2012, p. JTh2A.53.Yeh, C.-H., Lin, W.-P., Luo, C.-M., Xie, Y.-R., Chang, Y.-J., & Chow, C.-W. (2019). Utilizing Single Lightwave for Delivering Baseband/FSO/MMW Traffics Simultaneously in PON Architecture. IEEE Access, 7, 138927-138931. doi:10.1109/access.2019.2940898Van Veen, D. T., Houtsma, V. E., Gnauck, A. H., & Iannone, P. (2015). Demonstration of 40-Gb/s TDM-PON Over 42-km With 31 dB Optical Power Budget Using an APD-Based Receiver. Journal of Lightwave Technology, 33(8), 1675-1680. doi:10.1109/jlt.2015.2399271Rodríguez, S., Rommel, S., Vegas Olmos, J. J., & Monroy, I. T. (2017). Reconfigurable radio access unit to dynamically distribute W-band signals in 5G wireless access networks. Optical Switching and Networking, 24, 21-24. doi:10.1016/j.osn.2016.10.002Jianjun Yu, Zhensheng Jia, Yi, L., Su, Y., Gee-Kung Chang, & Ting Wang. (2006). Optical millimeter-wave generation or up-conversion using external modulators. IEEE Photonics Technology Letters, 18(1), 265-267. doi:10.1109/lpt.2005.862006Ma, J., Yu, J., Yu, C., Xin, X., Zeng, J., & Chen, L. (2007). Fiber Dispersion Influence on Transmission of the Optical Millimeter-Waves Generated Using LN-MZM Intensity Modulation. Journal of Lightwave Technology, 25(11), 3244-3256. doi:10.1109/jlt.2007.907794Wang, Y., Yu, J., Li, X., Xu, Y., Chi, N., & Chang, G.-K. (2015). Photonic Vector Signal Generation Employing a Single-Drive MZM-Based Optical Carrier Suppression Without Precoding. Journal of Lightwave Technology, 33(24), 5235-5241. doi:10.1109/jlt.2015.2499042Karinou, F., Stojanovic, N., Daly, A., Neumeyr, C., & Ortsiefer, M. (2016). 1.55-μm Long-Wavelength VCSEL-Based Optical Interconnects for Short-Reach Networks. Journal of Lightwave Technology, 34(12), 2897-2904. doi:10.1109/jlt.2015.2505359Almonacil, S., Jenneve, P., Ramantanis, P., & Layec, P. (2018). A Novel Constellation Phase Rotation Method to Reduce Transmitter Noise in Metro Links. IEEE Photonics Technology Letters, 30(16), 1459-1462. doi:10.1109/lpt.2018.2853645Li, L., Zhang, R., Liao, P., Cao, Y., Song, H., Zhao, Y., … Willner, A. E. (2019). Mitigation for turbulence effects in a 40-Gbit/s orbital-angular-momentum-multiplexed free-space optical link between a ground station and a retro-reflecting UAV using MIMO equalization. Optics Letters, 44(21), 5181. doi:10.1364/ol.44.005181Kanno, A., Dat, P. T., Kuri, T., Hosako, I., Kawanishi, T., Yoshida, Y., … Kitayama, K. (2012). Coherent Radio-Over-Fiber and Millimeter-Wave Radio Seamless Transmission System for Resilient Access Networks. IEEE Photonics Journal, 4(6), 2196-2204. doi:10.1109/jphot.2012.222818