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Photonics
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Advanced Technologies in Optical Wireless Communications
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Advanced Technologies in Optical Wireless Communications

A special issue of Photonics (ISSN 2304-6732). This special issue belongs to the section "Optical Communication and Network".

Deadline for manuscript submissions: 15 March 2025 | Viewed by 12218

Special Issue Editors

Dr. Cuiwei He

E-Mail Website
Guest Editor
School of Information Science, Japan Advanced Institute of Science and Technology (JAIST), 1 Chome-1 Asahidai, Nomi, Ishikawa 923-1211, Japan
Interests: optical wireless communications; visible light communications; visible light positioning; modulation/demodulation techniques; digital signal processing; photon-counting receiver; machine learning; fluorescent antenna
Special Issues, Collections and Topics in MDPI journals
Dr. Chen Chen

E-Mail Website
Guest Editor
School of Microelectronics and Communication Engineering, Chongqing University, Chongqing 400044, China
Interests: visible light communication and positioning; advanced modulation; multiple access and multiplexing
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

Optical wireless communication (OWC) is an innovative technology that combines the advantages of optical fiber and radio frequency (RF) communication, enabling high-speed broadband mobile transmission without the requirement for licensing the used optical frequency band. Additionally, OWC exhibits resistance to electromagnetic interference, providing robust confidentiality. As a result, there is a significant increase in interest in developing OWC technologies for a range of wireless applications, notably indoor LiFi and underwater OWC.

To boost the transmission data rate and/or enhance the reliability of different OWC systems, researchers are exploring various techniques. For example, there is a growing trend in recent research towards employing data-driven machine learning techniques in various OWC scenarios to enhance transmission performance. Moreover, many research groups are actively developing advanced transceiver devices, such as micro LEDs, VCSELs and photodetectors, specifically designed for OWC. These devices can support extremely high transmission bandwidth and, therefore, very high transmission data rates. Furthermore, there is a growing interest in novel interdisciplinary research that explores the application of advanced optical materials in OWC to enhance transmission performance. With the ongoing development of crucial techniques, we eagerly anticipate OWC playing a significant role in the future 6G network.

This Special Issue aims to publish high-quality papers that study emerging important technologies in OWC. Research areas may include (but are not limited to) the following topics:

  • Transmitter/receiver technologies for OWC;
  • Advanced signal processing in OWC;
  • Optical MIMO and spatial modulation;
  • High-quality OWC experiments;
  • Advanced optical materials in OWC;
  • Photon counting receivers in OWC;
  • Machine learning and neural networks in OWC;
  • Indoor localization and positioning;
  • Underwater optical wireless systems;
  • Vehicle-to-vehicle OWC.

Dr. Cuiwei He
Dr. Chen Chen
Guest Editors

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All submissions that pass pre-check are peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Photonics is an international peer-reviewed open access monthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 2400 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

  • optical wireless communications
  • visible light communication
  • indoor localization and positioning
  • LiFi
  • modulation/demodulation
  • machine learning
  • photon counting

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Published Papers (10 papers)

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Research

16 pages, 3824 KiB  
Article
A Hybrid Network Integrating MHSA and 1D CNN–Bi-LSTM for Interference Mitigation in Faster-than-Nyquist MIMO Optical Wireless Communications
by Minghua Cao, Qing Yang, Genxue Zhou, Yue Zhang, Xia Zhang and Huiqin Wang
Photonics 2024, 11(10), 982; https://doi.org/10.3390/photonics11100982 - 19 Oct 2024
Viewed by 903
Abstract
To mitigate inter-symbol interference (ISI) caused by Faster-than-Nyquist (FTN) technology in a multiple input multiple output (MIMO) optical wireless communication (OWC) system, we propose an ISI cancellation algorithm that combines multi-head self-attention (MHSA), a one-dimensional convolutional neural network (1D CNN), and bi-directional long [...] Read more.
To mitigate inter-symbol interference (ISI) caused by Faster-than-Nyquist (FTN) technology in a multiple input multiple output (MIMO) optical wireless communication (OWC) system, we propose an ISI cancellation algorithm that combines multi-head self-attention (MHSA), a one-dimensional convolutional neural network (1D CNN), and bi-directional long short-term memory (Bi-LSTM). This hybrid network extracts data features using 1D CNN and captures sequential information with Bi-LSTM, while incorporating MHSA to comprehensively reduce ISI. We analyze the impact of antenna numbers, acceleration factors, wavelength, and turbulence intensity on the system’s bit error rate (BER) performance. Additionally, we compare the waveform graphs and amplitude–frequency characteristics of FTN signals before and after processing, specifically comparing sampled values of four-pulse-amplitude modulation (4PAM) signals with those obtained after ISI cancellation. The simulation results demonstrate that within the Mazo limit for selecting acceleration factors, our proposal achieves a 7 dB improvement in BER compared to the conventional systems without deep learning (DL)-based ISI cancellation algorithms. Furthermore, compared to systems employing a point-by-point elimination adaptive pre-equalization algorithm, our proposal exhibits comparable BER performance to orthogonal transmission systems while reducing computational complexity by 31.15%. Full article
(This article belongs to the Special Issue Advanced Technologies in Optical Wireless Communications)
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13 pages, 4548 KiB  
Article
Deep Learning-Assisted High-Pass-Filter-Based Fixed-Threshold Decision for Free-Space Optical Communications
by Yan Gao, Qian-Wen Jing, Min-Fang Liu, Wen-Hao Zong and Yan-Qing Hong
Photonics 2024, 11(7), 599; https://doi.org/10.3390/photonics11070599 - 26 Jun 2024
Viewed by 1301
Abstract
This paper proposes a deep learning (DL)-assisted high-pass-filter (HPF)-based fixed-threshold decision (FTD) for free-space optical (FSO) communication. HPF is applied to reduce the scintillation effect by filtering out the low-frequency components of the received signal. However, the performance is limited owing to the [...] Read more.
This paper proposes a deep learning (DL)-assisted high-pass-filter (HPF)-based fixed-threshold decision (FTD) for free-space optical (FSO) communication. HPF is applied to reduce the scintillation effect by filtering out the low-frequency components of the received signal. However, the performance is limited owing to the signal distortion from HPF and remnant scintillation effect due to insufficient filtering. Therefore, the DL model is adopted to improve the performance of HPF-based scintillation effect compensation. The multilayer perceptron (MLP) model is used to adaptively select the peak frequency component of the received signal as the optimized cutoff frequency of HPF. Furthermore, recurrent neural network (RNN) and long short-term memory (LSTM) models are cascaded after HPF to compensate for the remnant scintillation effect and recover the signal distortion without the optimization of HPF cutoff frequency. The simulation was conducted under different turbulence channels and data rates. Simulation results showed that MLP-assisted adaptive optimized cutoff frequency and cascaded LSTM and HPF methods were close to the adaptive-threshold decision with precise channel state information under various turbulence channel degrees. Full article
(This article belongs to the Special Issue Advanced Technologies in Optical Wireless Communications)
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18 pages, 5745 KiB  
Article
Impact of Crystal Orientation on Modulation Bandwidth: Towards GaN LED-Based High-Speed Visible Light Communication
by Md Jahid Faruki, Krishnendu Bera and Nemai Karmakar
Photonics 2024, 11(6), 542; https://doi.org/10.3390/photonics11060542 - 5 Jun 2024
Cited by 1 | Viewed by 1092
Abstract
Light-emitting diodes (LEDs) with high modulation bandwidth are required for high-speed visible light communication applications. Crystal orientation in the GaN LED structure plays a key factor in its modulation bandwidth as the recombination lifetime is highly dependent on crystal orientation owing to the [...] Read more.
Light-emitting diodes (LEDs) with high modulation bandwidth are required for high-speed visible light communication applications. Crystal orientation in the GaN LED structure plays a key factor in its modulation bandwidth as the recombination lifetime is highly dependent on crystal orientation owing to the Quantum-Confined Stark Effect (QCSE). In this study, six different crystal orientation multi-quantum well (MQW) GaN LEDs are simulated to understand the impact of heterostructure orientation on modulation bandwidth, radiative recombination rates, and emission intensity. The results of this study demonstrate that semi-polar 101¯3¯ MQW LEDs provide the highest bandwidth in the current density range of 9–20 kA/cm2 compared to the other five orientations. For instance, the semi-polar 101¯3¯-based LED offers a modulation bandwidth of 912.7 MHz at 20 kA/cm2 current density. These results suggest that the semi-polar 101¯3¯ orientation-based LED has the potential to support a high-speed visible light communication system. Full article
(This article belongs to the Special Issue Advanced Technologies in Optical Wireless Communications)
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17 pages, 8171 KiB  
Article
Integrated Mobile Visible Light Communication and Positioning Systems Based on Decision Feedback Channel Estimation
by Ruoxuan Wang, Yuzhe Sun, Zhongxu Liu, Mingyi Gao and Xiaodi You
Photonics 2024, 11(6), 537; https://doi.org/10.3390/photonics11060537 - 4 Jun 2024
Cited by 1 | Viewed by 859
Abstract
Visible light communication (VLC) and visible light positioning (VLP) systems are usually designed separately to prevent mutual interference, while terminal mobility often introduces challenges that can degrade their performance. In this paper, we propose an integrated visible light communication and positioning (VLCP) scheme [...] Read more.
Visible light communication (VLC) and visible light positioning (VLP) systems are usually designed separately to prevent mutual interference, while terminal mobility often introduces challenges that can degrade their performance. In this paper, we propose an integrated visible light communication and positioning (VLCP) scheme designed for mobile scenarios, encompassing both multiple-input–single-output (MISO) and multiple-input–multiple-output (MIMO) configurations. This scheme integrates both functionalities into a unified system. Utilizing decision feedback channel estimation (DFCE), we effectively estimate the dynamic channel state information (CSI) for both VLC and VLP, thereby potentially enhancing both communication and positioning performance. Simulation results across various routes verify the effectiveness of the proposed scheme. It is observed that when the terminal moves at 1 m/s, the VLCP scheme with DFCE can maintain reliable transmission quality, ensuring bit error rates (BERs) consistently below 1.3 × 10−2. Additionally, the mean positioning errors remain within the centimeter range in different routes, not exceeding 4.3 cm and 15.5 cm in the MISO and MIMO scenarios, respectively. Full article
(This article belongs to the Special Issue Advanced Technologies in Optical Wireless Communications)
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13 pages, 5958 KiB  
Article
Single-Source VLCP System Based on Solar Cell Array Receiver and Right-Angled Tetrahedron Trilateration VLP (RATT-VLP) Algorithm
by Dawei Xie, Zhongxu Liu and Changyuan Yu
Photonics 2024, 11(6), 536; https://doi.org/10.3390/photonics11060536 - 4 Jun 2024
Cited by 2 | Viewed by 670
Abstract
A significant deployment limitation for visible light communication and positioning (VLCP) systems in energy- and light-source-restricted scenarios is the reliance of photodetectors (PDs) on external power supplies, compromising sustainability and complicating receiver charging. Solar cells (SCs), capable of harvesting and converting environmental light [...] Read more.
A significant deployment limitation for visible light communication and positioning (VLCP) systems in energy- and light-source-restricted scenarios is the reliance of photodetectors (PDs) on external power supplies, compromising sustainability and complicating receiver charging. Solar cells (SCs), capable of harvesting and converting environmental light into electrical energy, offer a promising alternative. Consequently, we first propose an indoor VLCP system that utilizes an SC array as the receiver, alongside a right-angled tetrahedron trilateration visible light positioning (RATT-VLP) algorithm based on a single light source and multiple receivers. The proposed system uses an SC array in place of PDs, utilizing binary phase shift keying (BPSK) signals for simultaneous communication and positioning. In experiments, we verified the system’s error-free communication rate of 1.21 kbps and average positioning error of 3.40 cm in a 30 cm × 30 cm area, indicating that the system can simultaneously satisfy low-speed communication and accurate positioning applications. This provides a viable foundation for further research on SC-based VLCP systems, facilitating potential applications in environments like underwater wireless communication, positioning, and storage tank inspection. Full article
(This article belongs to the Special Issue Advanced Technologies in Optical Wireless Communications)
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22 pages, 1619 KiB  
Article
Optimisation of the Transmitter Layout in a VLP System Using an Aperture-Based Receiver
by José Miguel Menéndez and Heidi Steendam
Photonics 2024, 11(6), 517; https://doi.org/10.3390/photonics11060517 - 28 May 2024
Viewed by 880
Abstract
In this paper, we consider a visible light positioning (VLP) system, where an array of photo diodes combined with apertures is used as a directional receiver and a set of inexpensive and energy-efficient light-emitting diodes (LEDs) is used as transmitters. The paper focuses [...] Read more.
In this paper, we consider a visible light positioning (VLP) system, where an array of photo diodes combined with apertures is used as a directional receiver and a set of inexpensive and energy-efficient light-emitting diodes (LEDs) is used as transmitters. The paper focuses on the optimisation of the layout of the transmitter, i.e., the number and placement of the LEDs, to meet the wanted position estimation accuracy levels. To this end, we evaluate the Cramer–Rao bound (CRB), which is a lower bound on the mean-squared error (MSE) of the position estimate, to analyse the influence of the LEDs’ placement. In contrast to other works, where only the location of the LEDs was considered and/or the optimisation was carried out through simulations, in this work, the optimisation is carried out analytically and considers all the parameters involved in the VLP system as well as the illumination. Based on our results, we formulate simple rules of thumb with which we can determine the spacing between LEDs and the minimum number of LEDs, as well as their position on the ceiling, while also taking into account the requirements for the illumination. Full article
(This article belongs to the Special Issue Advanced Technologies in Optical Wireless Communications)
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14 pages, 18406 KiB  
Article
Interference Mitigation in VLC Systems using a Variable Focus Liquid Lens
by Krishnendu Bera and Nemai Karmakar
Photonics 2024, 11(6), 506; https://doi.org/10.3390/photonics11060506 - 26 May 2024
Viewed by 1007
Abstract
The field of view (FOV) is an important parameter of a visible light communication (VLC) receiver. A variable FOV can be useful to mitigate interference from neighboring cells in a multi-cell VLC network. The existing works on dynamic FOV VLC receivers have used [...] Read more.
The field of view (FOV) is an important parameter of a visible light communication (VLC) receiver. A variable FOV can be useful to mitigate interference from neighboring cells in a multi-cell VLC network. The existing works on dynamic FOV VLC receivers have used a mechanical iris to control the receiver’s FOV, making the VLC receiver bulky, slow, and power-consuming. In this article, an electronically controlled variable focus liquid lens is used to vary the FOV of the receiver dynamically. A low-cost microcontroller-based feedback control system controls the effective FOV of the receiver to reject signals from unwanted transmitters, thus maximizing the signal-to-interference plus noise ratio (SINR) of the received signal. Experimental results show that the proposed technique effectively improves SINR performance in a multi-cell VLC network. To the best of the authors’ knowledge, this is the first reported work to utilize an electronically controlled compact liquid lens for designing a dynamic FOV VLC receiver. Full article
(This article belongs to the Special Issue Advanced Technologies in Optical Wireless Communications)
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14 pages, 1987 KiB  
Article
Design of the Light Source Layout Optimization Strategy Based on Region Partition and Pre-Bias Compensation for Indoor Visible Light Communication Systems
by Qiong Zhao, Weilin Zhang, Jiacheng Fan and Lijun Deng
Photonics 2023, 10(12), 1344; https://doi.org/10.3390/photonics10121344 - 6 Dec 2023
Viewed by 1469
Abstract
Optimization of the light source layout is an important issue for indoor visible light communication systems, as it affects the received optical power distribution and user perception. In this paper, we propose a local optimization strategy for the light source layout that balances [...] Read more.
Optimization of the light source layout is an important issue for indoor visible light communication systems, as it affects the received optical power distribution and user perception. In this paper, we propose a local optimization strategy for the light source layout that balances optimization effectiveness with optimization efficiency. First, we divide the optimization region into multiple sub-regions with different sizes and optimization priorities, where the sizes and optimization priorities of the individual sub-regions are determined based on the effect minimization principle among the sub-regions. We then calculate the pre-bias factor based on the equivalent mapping, which can compensate for the effect of the light sources in the latter optimized sub-region on the source layout optimization in the current sub-region. Finally, we search for the coordinate of a single light source for each sub-region using the variance of the squared distance between the projection of the light source on the receiving plane and the received point as a fitness function. Simulation results show that the proposed optimization strategy performs well when the vertical distance between the ceiling and the receiving plane is not less than 2.85 m. Full article
(This article belongs to the Special Issue Advanced Technologies in Optical Wireless Communications)
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15 pages, 416 KiB  
Article
Tolerance-Aided Interference Degradation for Optical OFDM in Power-Constrained Systems
by Yan Gao and Jie Lian
Photonics 2023, 10(11), 1206; https://doi.org/10.3390/photonics10111206 - 29 Oct 2023
Viewed by 1038
Abstract
Optical wireless communications (OWCs) are power-efficient for providing short-range and high-speed data transmission. In this paper, we propose an interference degradation algorithm for power-constrained OWC systems when using orthogonal frequency division multiplexing (OFDM). In this algorithm, we introduce a decision tolerance at the [...] Read more.
Optical wireless communications (OWCs) are power-efficient for providing short-range and high-speed data transmission. In this paper, we propose an interference degradation algorithm for power-constrained OWC systems when using orthogonal frequency division multiplexing (OFDM). In this algorithm, we introduce a decision tolerance at the receiver that can be optimally designed to reduce interference caused by peak power clipping distortion and decrease additive noise collected by the photodetectors. Although the recently proposed clipping-enhanced optical OFDM (CEO-OFDM) can transmit clipped information through extra signal frames, reconstructing the received signal introduces more noise. Using the proposed decision tolerance, we can determine whether the signals in the extra frame are required for data reconstruction. By optimally choosing the decision tolerance, the bit error rate (BER) performance is enhanced compared to those of DCO, ACO, and CEO-OFDM. Additionally, the proposed algorithm offers a wider dynamic modulation index range than DCO, ACO, and CEO-OFDM at the same BER. Using the tested parameters, the proposed algorithm with 64-QAM achieves a similar best BER performance as DCO, ACO, and CEO-OFDM using 32-QAM. Therefore, the proposed algorithm achieves a higher data rate than those of the other compared techniques. Full article
(This article belongs to the Special Issue Advanced Technologies in Optical Wireless Communications)
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13 pages, 3531 KiB  
Article
Performance Analysis of Soft-Switching FSO/THz-RF Dual-Hop AF-NOMA Link Based on Cognitive Radio
by Rongpeng Liu, Ziyang Wang, Xuerui Wang, Jingwei Lu, Yawei Wang, Yizhou Zhuo, Ruihuan Wu, Zhongchao Wei and Hongzhan Liu
Photonics 2023, 10(10), 1086; https://doi.org/10.3390/photonics10101086 - 27 Sep 2023
Cited by 1 | Viewed by 1320
Abstract
This paper presents a promising solution to address the scarcity of spectrum resources and enhance spectrum efficiency in the context of cognitive radio (CR)-based soft-switching free-space optical (FSO)/terahertz (THz) radio frequency (RF) dual-hop amplify-and-forward (AF)–non-orthogonal multiple access (ROMANO) links. The impact of maximum [...] Read more.
This paper presents a promising solution to address the scarcity of spectrum resources and enhance spectrum efficiency in the context of cognitive radio (CR)-based soft-switching free-space optical (FSO)/terahertz (THz) radio frequency (RF) dual-hop amplify-and-forward (AF)–non-orthogonal multiple access (ROMANO) links. The impact of maximum tolerable interference power in the primary network, transmit power in the secondary transmitter, and maximum relay transmission power on the link are thoroughly studied. The numerical results ultimately validate the effectiveness of this link in improving performance, and a comparative analysis is conducted with the without-CR scheme, highlighting the distinctive characteristics of the proposed link. Full article
(This article belongs to the Special Issue Advanced Technologies in Optical Wireless Communications)
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Planned Papers

The below list represents only planned manuscripts. Some of these manuscripts have not been received by the Editorial Office yet. Papers submitted to MDPI journals are subject to peer-review.

Title: High performance Series/Parallel Boost/Buck DC/DC Converter as a Visible Light Communication HB-LED Driver based on the Split Power
Authors: Daniel G. Aller1; Diego G. Lamar2*; Juan R. García-Mere2; Marta M. Hernando2; Juan Rodriguez2; Javier Sebastian2
Affiliation: 1-Airbus Crisa (an Airbus Defense and Space Company), Madrid, Spain [email protected] 2-Power Supplies Group - Electrical Engineering Department of the University of Oviedo, Gijon, Spain; [email protected], [email protected], [email protected], [email protected] and [email protected]. *Correspondence: [email protected]
Abstract: This work proposes a High-Brightness LED (HB-LED) driver for Visible Light Communication (VLC) based on two converters, a high frequency Buck DC/DC converter and a low frequency Boost DC/DC converter, connected in series regarding the LED load. A VLC system needs to fulfill two different tasks: biasing the LED and generating the communication signal. These two tasks have typically different power requirement, the bias power is 3/4, while the communication power is 1/4 of the total power. And the requirements of both are different: the communication signal requires a high frequency and a fast output response, while the biasing control requires a converter with slow output voltage response. The proposed topology takes advantage of the differences between the two tasks and reaches high efficiency and high communication perfor-mance by means of splitting the power between the two DC/DC converters. A high frequency Buck DC/DC converter generates the communication signal, while the low frequency Boost DC/DC converter is in charge of biasing the LEDs. This technique allows to process most of the DC biasing power by the low frequency converter (reaching high efficiency) and keeping the high frequency converter delivering the communication power (reaching high communication per-formance). As experimental results, the proposed VLC HB-LED driver is built and validated by reproducing a 64-QAM with a bit rate up to 1.5 Mbps, reaching a 91.5% of overall efficiency

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