Design of PAM-8 VLC Transceiver System Employing Neural Network-Based FFE and Post-Equalization
Abstract
:1. Introduction
- (1)
- A high-speed PAM-8 VLC transceiver system is proposed and simulated through the cooperation of MATLAB and Cadence. The AFEs of the transmitter and receiver, LED model, channel models, and PD model are all designed and implemented in Cadence, while the digital baseband, binary-weighted DAC in the transmitter, and flash ADC in the receiver are implemented in MATLAB.
- (2)
- NN-based equalization schemes are proposed and adopted as both the pre- and post-equalizations in the PAM-8 VLC system. In the transmitter, an FFE is implemented through a traditional NN in the baseband with the benefit of higher accuracy of the tap weights. In the receiver, an RBF-NN is proposed and adopted as the post-equalization, which is utilized to compensate for channel loss and solve the problems of modulation bandwidth limitation. With the combination of an NN-based FFE with passive equalizers serving as pre-equalization and the RBF-NN as post-equalization, the highest achievable data rate with a 3 m free-space channel is 3.6 Gbps.
- (3)
- Different communication channels are taken into consideration and compared. The proposed NN-enabled VLC transceiver system is also applied to realize underwater VLC. An underwater channel model is designed and analyzed for simulating the performance of underwater VLC with the same transceiver. This underwater VLC system is compared with experimental results and verifies the feasibility of the proposed hybrid equalization scheme in an underwater channel.
2. Analysis of Models and Limitations in VLC Systems
2.1. µ-LED Model
2.2. PD Model
2.3. Free-Space Channel Model and Underwater Channel Model
2.4. Bandwidth Limitation and Nonlinearity
3. Analysis of Equalization Methods
3.1. Passive Equalizer
3.2. FFE
3.3. DNN and RBF-NN
4. Architecture of VLC Transceiver Circuits
4.1. Transmitter in VLC System
4.2. Receiver in VLC System
5. Simulation Results and Discussion
5.1. Pre-equalization Performance Evaluation
5.2. Post-Equalization Performance Evaluation
5.3. Training Performance Evaluation
5.4. Comparison of Other VLC Systems with Neural Network
6. Conclusions
Author Contributions
Funding
Data Availability Statement
Conflicts of Interest
References
- Hale, W.K. Frequency assignment: Theory and applications. Proc. IEEE 1980, 68, 1497–1514. [Google Scholar] [CrossRef]
- Komine, T.; Nakagawa, M. Fundamental analysis for visible-light communication system using LED lights. IEEE Trans. Consum. Electron. 2004, 50, 100–107. [Google Scholar] [CrossRef]
- Pathak, P.H.; Feng, X.; Hu, P.; Mohapatra, P. Visible light communication, networking, and sensing: A survey, potential and challenges. IEEE Commun. Surv. Tuts. 2015, 17, 2047–2077. [Google Scholar] [CrossRef]
- Minh, H.L.; O’Brien, D.; Faulkner, G.; Zeng, L.; Lee, K.; Jung, D.; Oh, Y. 80 Mbit/s visible light communications using pre-equalized white LED. In Proceedings of the 2008 34th European Conference on Optical Communication (ECOC), Brussels, Belgium, 21–25 September 2008; pp. 1–2. [Google Scholar]
- Hussain, B.; Li, X.; Che, F.; Yue, C.P.; Wu, L. Visible light communication system design and link budget analysis. J. Lightw. Technol. 2015, 33, 5201–5209. [Google Scholar] [CrossRef]
- Chun, H.; Manousiadis, P.; Rajbhandari, S.; Vithanage, D.A.; Faulkner, G.; Tsonev, D.; McKendry, J.J.D.; Videv, S.; Xie, E.; Gu, E.; et al. Visible light communication using a blue GaN μLED and fluorescent polymer color converter. IEEE Photon. Technol. Lett. 2014, 26, 2035–2038. [Google Scholar] [CrossRef] [Green Version]
- Ferreira, R.X.G.; Xie, E.; McKendry, J.J.D.; Rajbhandari, S.; Chun, H.; Faulkner, G.; Kelly, A.E.; Gu, E.; Penty, R.V.; White, I.H.; et al. High bandwidth GaN-based micro-LEDs for multi-Gb/s visible light communications. IEEE Photon. Technol. Lett. 2016, 28, 2023–2026. [Google Scholar] [CrossRef] [Green Version]
- Li, X.; Cheng, C.; Zhang, C.; Wei, Z.; Wang, L.; Fu, H.Y.; Yang, Y. Net 4 Gb/s underwater optical wireless communication system over 2 m using a single-pixel GaN-based blue mini-LED and linear equalization. Opt. Lett. 2022, 47, 1976–1979. [Google Scholar] [CrossRef]
- Islim, M.S.; Ferreira, R.X.; He, X.; Xie, E.; Videv, S.; Viola, S.; Watson, S.; Bamiedakis, N.; Penty, R.V.; White, I.H.; et al. Towards 10 Gb/s orthogonal frequency division multiplexing-based visible light communication using a GaN violet micro-LED. Photon. Res. 2017, 5, A35–A43. [Google Scholar] [CrossRef]
- Zhang, Z.; Lai, Y.; Lv, J.; Liu, P.; Teng, D.; Wang, G.; Liu, L. Over 700 MHz −3 dB bandwidth UOWC system based on blue HV-LED with T-bridge pre-equalizer. IEEE Photon. J. 2019, 11, 7903812. [Google Scholar] [CrossRef]
- Li, X.; Bamiedakis, N.; Guo, X.; McKendry, J.J.D.; Xie, E.; Ferreira, R.; Gu, E.; Dawson, M.D.; Penty, R.V.; White, I.H. Wireless visible light communications employing feed-forward pre-equalization and PAM-4 modulation. J. Lightw. Technol. 2016, 34, 2049–2055. [Google Scholar] [CrossRef]
- Chen, H.; Niu, W.; Zhao, Y.; Zhang, J.; Chi, N.; Li, Z. Adaptive deep-learning equalizer based on constellation partitioning scheme with reduced computational complexity in UVLC system. Opt. Express 2021, 29, 21773–21782. [Google Scholar] [CrossRef]
- Wang, Y.; Tao, L.; Huang, X.; Shi, J.; Chi, N. 8-Gb/s RGBY LED-based WDM VLC system employing high-order CAP modulation and hybrid post equalizer. IEEE Photon. J. 2015, 7, 7904507. [Google Scholar]
- Khalid, A.M.; Cossu, G.; Corsini, R.; Choudhury, P.; Ciaramella, E. 1-Gb/s Transmission over a phosphorescent white LED by using rate-adaptive discrete multitone modulation. IEEE Photon. J. 2012, 4, 1465–1473. [Google Scholar] [CrossRef] [Green Version]
- Amran, N.A.; Soltani, M.D.; Yaghoobi, M.; Safari, M. Deep learning based signal detection for OFDM VLC systems. In Proceedings of the 2020 IEEE International Conference on Communications Workshops (ICC Workshops), Dublin, Ireland, 7–11 June 2020; pp. 1–6. [Google Scholar]
- Chen, H.; Zhao, Y.; Hu, F.; Chi, N. Nonlinear resilient learning method based on joint time-frequency image analysis in underwater visible light communication. IEEE Photon. J. 2020, 12, 7901610. [Google Scholar] [CrossRef]
- Lu, X.; Lu, C.; Yu, W.; Qiao, L.; Liang, S.; Lau, A.P.T.; Chi, N. Memory-controlled deep LSTM neural network post-equalizer used in high-speed PAM VLC system. Opt. Express 2019, 27, 7822–7833. [Google Scholar] [CrossRef] [Green Version]
- Shi, M.; Zhao, Y.; Yu, W.; Chen, Y.; Chi, N. Enhanced performance of PAM7 MISO underwater VLC system utilizing machine learning algorithm based on DBSCAN. IEEE Photon. J. 2019, 11, 7905013. [Google Scholar] [CrossRef]
- Che, F.; Wu, L.; Hussain, B.; Li, X.; Yue, C.P. A fully integrated IEEE 802.15.7 visible light communication transmitter with on-chip 8-W 85% efficiency boost LED driver. J. Lightw. Technol. 2016, 34, 2419–2430. [Google Scholar] [CrossRef]
- Wu, L.; Li, X.; Chong, W.H.; Liu, Z.; Che, F.; Hussain, B.; Lau, K.M.; Yue, C.P. An AMLED microdisplay driver SoC with built-in 1.25-Mb/s VLC transmitter. In Proceedings of the 2015 Symposium on VLSI Circuits (VLSI Circuits), Kyoto, Japan, 17–19 June 2015; pp. C328–C329. [Google Scholar]
- Li, X.; Hussain, B.; Wang, L.; Jiang, J.; Yue, C.P. Design of a 2.2-mW 24-Mb/s CMOS VLC receiver SoC with ambient light rejection and post-equalization for Li-Fi applications. J. Lightw. Technol. 2018, 36, 2366–2375. [Google Scholar] [CrossRef]
- Kosman, J.; Almer, O.; Abbas, T.A.; Dutton, N.; Walker, R.; Videv, S.; Moore, K.; Haas, H.; Henderson, R. 29.7 A 500 Mb/s −46.1 dBm CMOS SPAD receiver for laser diode visible-light communications. In Proceedings of the 2019 IEEE International Solid- State Circuits Conference (ISSCC), San Francisco, CA, USA, 17–21 February 2019; pp. 468–470. [Google Scholar]
- Li, X.; Ghassemlooy, Z.; Zvanovec, S.; Alves, L. An equivalent circuit model of a commercial LED with an ESD protection component for VLC. IEEE Photon. Technol. Lett. 2021, 33, 777–779. [Google Scholar] [CrossRef]
- Cheung, W.; Edwards, P.; French, G. Determination of LED equivalent circuits using network analyzer measurements. In Proceedings of the 1998 Conference on Optoelectronic and Microelectronic Materials and Devices (COMMAD), Perth, WA, Australia, 14–16 December 1998; pp. 232–235. [Google Scholar]
- Wang, C.; Yu, H.Y.; Zhu, Y.J. A long distance underwater visible light communication system with single photon avalanche diode. IEEE Photon. J. 2016, 8, 7906311. [Google Scholar] [CrossRef]
- Mobley, C.D.; Gentili, B.; Gordon, H.R.; Jin, Z.; Kattawar, G.W.; Morel, A.; Reinersman, P.; Stamnes, K.; Stavn, R.H. Comparison of numerical models for computing underwater light fields. Appl. Opt. 1993, 32, 7484–7504. [Google Scholar] [CrossRef] [PubMed]
- Chen, H.; Chen, X.; Lu, J.; Liu, X.; Shi, J.; Zheng, L.; Liu, R.; Zhou, X.; Tian, P. Toward long-distance underwater wireless optical communication based on a high-sensitivity single photon avalanche diode. IEEE Photon. J. 2020, 12, 7902510. [Google Scholar] [CrossRef]
- Zeng, Z.; Fu, S.; Zhang, H.; Dong, Y.; Cheng, J. A survey of underwater optical wireless communications. IEEE Commun. Surv. Tut. 2017, 19, 204–238. [Google Scholar] [CrossRef]
- Proakis, J.G. Digital Communication, 5th ed.; McGraw Hill: Boston, MA, USA, 2008; p. 602. [Google Scholar]
- Bergh, A.A.; Dean, P.J. Light-emitting diodes. Proc. IEEE 1972, 60, 156–223. [Google Scholar] [CrossRef]
- Dimitrov, S.; Sinanovic, S.; Haas, H. Signal shaping and modulation for optical wireless communication. J. Lightw. Technol. 2012, 30, 1319–1328. [Google Scholar] [CrossRef]
- Ahmad, S.T.; Kumar, K.P. Radial basis function neural network nonlinear equalizer for 16-QAM coherent optical OFDM. IEEE Photon. Technol. Lett. 2016, 28, 2507–2510. [Google Scholar] [CrossRef]
- Razavi, B. Design of Integrated Circuits for Optical Communications, 2nd ed.; John Wiley & Sons: Hoboken, NJ, USA, 2012. [Google Scholar]
- Chen, R.Y.; Yang, Z. CMOS transimpedance amplifier for visible light communications. IEEE Trans. Very Large Scale Integr. Syst. 2015, 23, 2738–2742. [Google Scholar] [CrossRef]
- Chi, N.; Zhao, Y.; Shi, M.; Zou, P.; Lu, X. Gaussian kernel-aided deep neural network equalizer utilized in underwater PAM8 visible light communication system. Opt. Express 2018, 26, 26700–26712. [Google Scholar] [CrossRef]
VLC Link | Parameters | Typical Value |
---|---|---|
Transmitter (μ-LED Model) | Total Power Half-power Angle −3 dB Bandwidth | 20 W 50° ~50 MHz |
Receiver (PD Model S5973-01) | PD Area Photosensitivity Dark Current Terminal Capacitance Field-of-view Angle −3 dB Bandwidth | 0.12 mm2 0.51 A/W 100 pA 1.6 pF 30° 1 GHz |
Free-Space Channel | Link Range Emission Angle α Receiving Angle β | 0.1–5 m 0° 0° |
Underwater Channel | Link Range Water Type Absorption Coefficient a(λ) [28] Scattering Coefficient b(λ) [28] Tank Attenuation Coefficient [27] | 0.1–5 m Clear sea water 0.114 m−1 0.037 m−1 0.265 m−1 |
Type of NN | Activation Function | Approximation Approach | Neuron Layers |
---|---|---|---|
RBF-NN | Gaussian Kennel Function | Local Approximation | 3 |
DNN | Sigmoid Function | Universal Approximation | >3 |
Specifications of VLC System | [12] | [15] | [16] | [17] | [35] | This Work | |
---|---|---|---|---|---|---|---|
System Architecture | Channel Type | Water | Free-Space | Water | Free-Space | Water | Free-Space and Water |
Channel Length | 1.2 m | 3 m | 1.2 m | 1.2 m | 1.2 m | 3 m and 1.2 m | |
LED Bandwidth | 200 MHz | / | 200 MHz | 15 MHz | 200 MHz | 50 MHz | |
PD Bandwidth | 250 MHz | / | 250 MHz | 200 MHz | 250 MHz | 1 GHz | |
Pre-EQ | Passive EQ | / | Passive EQ | Passive EQ | Passive EQ | Passive EQ with FFE | |
Post-EQ | NN-based EQ | NN-based EQ | NN-based EQ | NN-based EQ | NN-based EQ | NN-based EQ | |
AFE Type | Discrete Components | Discrete Components | Discrete Components | Discrete Components | Discrete Components | Integrated Circuits | |
Implementation | Experiment | Matlab Simulation | Experiment | Experiment | Experiment | Matlab Simulation | |
Specifications of NNs | Type of NN | CV-NN | LSTM | TFDN | LSTM | GKDNN | RBF-NN |
Iterations | / | / | / | 400 | 2000 | 1200 | |
Data Transmission | Data Rate | 2.85 Gbps | / | 2.85 Gbps | 1.15 Gbps | 1.5 Gbps | 3.6 Gbps and 4.2 Gbps |
Modulation Scheme | 64-QAM | DCO-OFDM | 64-QAM | PAM-7 and PAM-8 | PAM-8 | PAM-8 |
Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations. |
© 2022 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https://creativecommons.org/licenses/by/4.0/).
Share and Cite
Xu, B.; Min, T.; Yue, C.P. Design of PAM-8 VLC Transceiver System Employing Neural Network-Based FFE and Post-Equalization. Electronics 2022, 11, 3908. https://doi.org/10.3390/electronics11233908
Xu B, Min T, Yue CP. Design of PAM-8 VLC Transceiver System Employing Neural Network-Based FFE and Post-Equalization. Electronics. 2022; 11(23):3908. https://doi.org/10.3390/electronics11233908
Chicago/Turabian StyleXu, Bo, Tianxin Min, and Chik Patrick Yue. 2022. "Design of PAM-8 VLC Transceiver System Employing Neural Network-Based FFE and Post-Equalization" Electronics 11, no. 23: 3908. https://doi.org/10.3390/electronics11233908
APA StyleXu, B., Min, T., & Yue, C. P. (2022). Design of PAM-8 VLC Transceiver System Employing Neural Network-Based FFE and Post-Equalization. Electronics, 11(23), 3908. https://doi.org/10.3390/electronics11233908