Optical Wireless Communication Channels Research Articles

Beyond 10 Gbps in Hostile Underwater Optical Wireless Communication Channel Conditions Using Polarisation Division Multiplexing

Beyond 10 Gbps in Hostile Underwater Optical Wireless Communication Channel Conditions Using Polarisation Division Multiplexing

PERFORMANCE ANALYSIS OF OPTICAL WIRELESS COMMUNICATION SYSTEM DESIGNED BY USING DIFFERENT FILTERS

Free space optical communication (FSO) technology, which has been developing in recent years, is advantageous compared to other wireless communication technologies due to its features such as high bandwidth, low latency, and high security. Since the FSO system is sensitive to atmospheric events, it needs various signal processing and filtering techniques to reduce the deterioration in the quality of the signal. The FSO free space channel has several channel types, such as the scattered channel and the optical wireless communication (OWC) channel. In this study, comparisons were made using various filters in an FSO system designed using the optical wireless communication (OWC) transmission channel model, and the system was analyzed based on the results obtained.

High modulation effects on hybrid optical fiber links and OWC Channel based on optical DP-QSK transceiver systems

Abstract This study clarified the simulation of the high modulation effects on hybrid optical fiber links and OWC channel based on optical DP-QSK transceiver systems. The optimum lighted signal power band with the spectral wavelength after optical wireless communication channel is clarified. Total lighted form band power after optical fiber cable channel is studied. Total lighted form band power form after optical wireless communication channel is shown in numerical values. The total electrical band power form after optical DPSK receiver based optical fiber cable channel is demonstrated. Total base electrical band power form after optical DPSK receiver based optical wireless communication channel is clarified. Base band signal base form per noise base band form ratio is studied and numerical clarified after optical DPSK receiver against propagation length for both OFC and OWC channels. Total lighted base form power versus propagation length based both OFC and OWC channels is demonstrated. Optimum lighted form base power band form with time after optical fiber cable channel is studied. The max lighted form base power band form with time after optical wireless communication channel is simulated. Optimum lighted signal power band with the spectral wavelength after optical fiber cable channel is demonstrated. The total base electrical band form power after optical DPSK receiver is clarified numerically against propagation length for both OFC and OWC channels.

Impact of Intense Modulation on Soliton Power Propagation across Optical Fiber and Optical Wireless Channels

The optical pulse generator model in Optisystem 20 is utilized to generate an optical soliton pulse. The performance evaluation of highly modulated soliton power transmission is carried out on both optical fiber and optical wireless communication channels. The evaluation considers a flow rate of 40 Gbps and a link distance, which is not specified in the provided context. Among the proposed modulation schemes, which include CPFSK, FSK, and PSK, CPFSK demonstrates superior performance for both communication channels. Increasing the number of bits per symbol enhances the bit error rate (BER) at the fiber or wireless channel, as received by the optical receiver, for different modulation schemes, except for the CPFSK scheme. Thus, it is evident that the CPFSK modulation scheme is more efficient and outperforms other modulation schemes for various communication channels. Hence, it is evident that the CPFSK modulation scheme exhibits superior efficiency and outperforms other modulation schemes for a variety of communication channels.

Modeling and oblique transmission characteristics of an underwater wireless optical communication channel based on ocean depth layering.

Underwater wireless optical communication is widely considered in the field of underwater communication due to its high bandwidth and low latency. In a real transmission link, the temperature and salinity of seawater, chlorophyll concentration, and bubble density vary with ocean depth. Therefore, the depth of the optical transmitter in seawater and the tilt angle of the beam will exhibit different beam transmission characteristics. In this paper, an underwater oblique-range layered channel model considering the combined effects of dynamic turbulence, absorption, and scattering is developed based on real data of seawater at different depths measured by the Global Ocean Observing Buoy Argo and the Woods Hole Oceanographic Institution BCO-DMO. The effects of transmission distance, transmitter tilt angle, and transmitter depth on the oblique-range transmission characteristics of the beam in seawater are discussed. The simulation results show that, at the same transmission distance, the beam centroid displacement increases with an increase in transmitter depth only when the transmitter is located above the interior of the thermocline. When the transmitter is located below the interior of the thermocline, the influence of the transmitter tilt angle on the beam centroid displacement decreases. This indicates that at different depths within the interior of the thermocline, the optical beam transmission characteristics exhibit significant variations.

Method for evaluation of the optical uniformity distribution in the white LEDs-based visible light communication applications

The uniformity characteristic of emitted radiation in VLC applications is a factor that can affect the efficiency of a detector and the overall efficiency of the VLC system. In this paper, we theoretically investigate the optical uniformity characteristic of using LEDs in VLC applications in terms of the parameter of the emission angle of LEDs and the spatial distribution of LEDs. The result indicates that the optical uniformity can be controlled at a high level by controlling the emission angle of the LED or distributing the LEDs in the room's space. Full Text: PDF References E.-F. Schubert, J.-K. Kim, "Solid-State Light Sources Getting Smart", Science 308, 1274 (2005). CrossRef N. Narendran, Y. Gu, "Life of LED-based white light sources", J. Display Technol. 1, 167 (2005). CrossRef E. Schubert, Light-Emitting Diodes (Cambridge, Cambridge Univ. Press 2006). CrossRef C.C. Sun, Q.K. Nguyen, T.X. Lee, S.K. Lin, C.S. Wu, T.H. Yang, Y.W. Yu, "Active thermal-fuse for stopping blue light leakage of white light-emitting diodes driven by constant current", Sci. Reports 12, 12433 (2022). CrossRef Z. Ghassemlooy, W. Popoola, S. Rajbhandari. Optical Wireless Communications System and Channel Modelling with MATLAB (Florida, CRC Press, Taylor & Francis Group, 2013). CrossRef A. Burton, H. Le Minh, Z. Ghasemlooy, S. Rajbhandari, "A study of LED lumination uniformity with mobility for visible light communications", IEEE 2012 Int. Workshop on Opt. Wireless Comm. (IWOW), Pisa, Italy, 2012. CrossRef M.S.M. Gismalla, M.F.L. Abdullah, M.I. Niass, B. Das, W.A. Mabrouk. "Effect of optical attocells deployment on the RMSD spread in indoor visible light communication systems", Int. J. Commun Syst. e4349 (2020). CrossRef C. Wang, J. Wang, J. Zhang, J. Wang, H. Du, J. Wang, "Research on uniform illumination distribution of indoor visible light communication", Proc. SPIE 12062, AOPC 2021: Optoelectronics and Nanophotonics (2021). CrossRef M.V. Bhalerao, M. Sumathi, S.S. Sonavane. "Line of sight model for visible light communication using Lambertian radiation pattern of LED", Int. J. Comm. Systems (2016). CrossRef J.F. Zang, Y. Piao. "Research on visible light communication system based on white LEDs", Proc. SPIE 10255, (2016). CrossRef M. Oliveira, F.C.B. Tosta, D.E.F. Guillen, P.P. Monteiro, A.A.P. Poh, "Theoretical and Experimental Analysis of LED Lamp for Visible Light Communications", Wireless Personal Communications 125, 3461(2022). CrossRef J.P. Ding, C. Lin, J.T. Wang, H. Yang, "Effects of Optical Beams on MIMO Visible Light Communication Channel Characteristics", Sensors 22, 216 (2022). CrossRef X. Zhang , N. Zhao, F. Al-Turjman, M.B. Khan, X. Yang. "An Optimization of the Signal-to-Noise Ratio Distribution of an Indoor Visible Light Communication System Based on the Conventional Layout Model", Sustainability 12, 9006 (2020). CrossRef A. Kaewpukdee, P. Uthansakul, "Characteristic of Line-of-Sight in Infrastructure-to-Vehicle Visible Light Communication Using MIMO Technique", Materials Continua 74, 1026 (2023). CrossRef

Research on Underwater Wireless Optical Communication Channel Model and Its Application

Underwater wireless optical communication (UWOC) is an emerging technology with wide-ranging applications in marine exploration, offshore industries, environmental monitoring, and underwater robotics. In order to investigate the application of UWOC in environments of different water quality, this study establishes a model of an optical communication channel and analyzes the impact of water quality on communication range. Our experimental design is employed to validate the effectiveness of the model and analyze the sources of model errors. Furthermore, this research introduces the concept of an “effective communication space” for underwater optical wireless communication and constructs an experimental platform to test the effective communication space under various water quality conditions. In addition, the application methods and workflow of wireless optical communication on underwater mobile platforms are discussed, and field tests are conducted in a practical lake environment to verify the application value of the effective communication space. This research offers valuable guidance for advancing the study and engineering applications of UWOC technology.

Effect of water-waves on recognition of speech signals transmitted over a wireless optical communication channel

In many sea-exploration scenarios, a wireless optical communication link between an onshore station and a floating marine structure or between a floating buoy and an underwater vehicle is required. In order to establish high-quality wireless optical communication, the effect of sea-waves must be taken into consideration. In this work, we investigate the influence of surface water waves having various amplitudes, frequencies and waveforms on the quality of an analog speech signal transmitted over a wireless optical communication link. Such investigation is also carried out on an encrypted speech signal. The quality of the speech signals is determined by utilizing a deep learning neural network that is trained to recognize ten speech commands and produces classification probabilities. In our experiments, either the detector or the light source is non-stationary as a result of the water-waves, thus distorting the received analog signal. We also show a method of deriving the frequency of the water waves by using a remote tracking unit based on micro-electro-mechanical systems (MEMS) mirrors.

Bit and Power Loading Algorithms for Nonlinear Optical Wireless Communication Channels

Bit and Power Loading Algorithms for Nonlinear Optical Wireless Communication Channels

Tradeoff Between Diversity and Multiplexing Gains in Block Fading Optical Wireless Channels

The diversity-multiplexing tradeoff (DMT) provides a fundamental performance metric for different multiple-input multiple-output (MIMO) schemes in wireless communications. In this paper, we explore the block fading optical wireless communication (OWC) channels and characterize the DMT in the presence of both optical peak- and average-power constraints. Three different fading distributions are considered, which reflect different channel conditions. In each channel condition, we obtain the optimal DMT when the block length is sufficiently large, and we also derive the lower and upper bounds of the DMT curve when the block length is small. These results are dramatically different from the existing DMT results in radio-frequency (RF) channels. These differences may be due to the fact that the optical input signal is real and bounded, while its RF counterpart is usually complex and unbounded.

Statistical channel modeling of intensity fluctuations in a turbulent underwater wireless optical communication system

Subject of study. The statistical modeling of received intensity fluctuations due to temperature-induced turbulence and the random presence of air bubbles in an underwater wireless optical communication channel is presented. Aim of study. Temperature-induced turbulence and air bubbles induce severe intensity fluctuations in the received optical signal, which degrade the underwater wireless optical communication link performance. Method. Therefore, to characterize the turbulent water channel, an experimental setup has been designed in the laboratory that considers uniform and gradient-based temperature variations along with variable-sized bubble populations. To estimate the effect of these random variations in the water channel, a statistical approach has been followed, which characterizes the nature of the recorded observations. Main results. It is observed that the behavior of random irradiance fluctuations due to uniform and gradient-based temperature variations in the underwater wireless optical communication link follows a single-lobe Gaussian distribution. Moreover, with the incorporation of air bubbles, the received irradiance fluctuations no longer follow a single-lobe Gaussian distribution but follow a multi-lobe Gaussian distribution, i.e., the Gaussian mixture model, which is the weighted sum of the Gaussian distribution. The accuracy of the proposed underwater wireless optical communication link models is verified by conducting the goodness of fit test; the observed confidence interval of 95% authenticates the proposed model. Also, the performance of the Gaussian-mixture-model-based underwater wireless optical communication link has been evaluated in terms of bit error rate, and the acceptable bit error rate levels between 1014 and 1010 have been observed. The proposed underwater wireless optical communication with Gaussian mixture model completely depicts thermally uniform, gradient-based nonuniform, and variable air bubble populations in the ocean. Practical significance. The Gaussian mixture model can further be utilized by the researchers to estimate numerous performance parameters of the turbulent underwater wireless optical communication links using advanced modulation schemes and diversity techniques and paves a valuable way to address the future aspects of research in this area.

Efficient employment of optical sources integrated with both light detectors and free space communication modulated channel under ambient conditions effects

Abstract The paper simulates the efficient employment of light sources integrated with both light detectors and free space communication channel under ambient condition effects. The modified duobinary non return to zero line coding system based optical wireless communication channel under light or dense fog level effects. Max. Q factor against OWC reach is simulated at light and dense fog level for the suggested with the previous model. The study emphasis that the OWC length has been reached to 65 km at light fog level and the OWC length has been reached to 5 km at dense Fog level with acceptable signal power. The total light power and total electrical power are illustrated at light and dense fog levels. Max. Q factor and min. BER after receiver based OWC are clarified at light and dense fog levels.

Effect of bioluminescence on the performance of an underwater optical wireless communication channel

The performance of an underwater wireless optical communication channel (UWOC) is affected by the ambient noise in the water medium. However, no major studies have estimated the spectral bioluminescence upwelling radiance (BLu) numerically with the inputs of measured bioluminescence potential (BP) in oceanic conditions. This study presents a numerical model to estimate the BLu in open ocean and coastal waters and to investigate the UWOC channel performance in terms of the bit error rate (BER) in presence of bioluminescence using Monte Carlo numerical technique. The simulation results suggested that the BER performance degrades in the presence of bioluminescence and can be improved with a narrower receiver FOV. Further, the impact of bioluminescence on the BER performance of the UWOC system at different operational depths is investigated under typical system specifications (APD/PMT, FOV, and receiver aperture). The simulation results showed that BER at different operational depths is more sensitive in open ocean waters than in coastal turbid water with the bioluminescence signal. The results demonstrate that the PMT improves the UWOC channel performance better than the APD. Besides, these results revealed that the BP stimulation at multiple depths deteriorates the BER performance heavily in comparison to the BP stimulation at single depth in the real sea environment. The results presented in this study provide valuable insights and information for accurate design and development of the UWOC system for the enhanced bioluminescence background noise conditions.

Performance Comparison of Different Rotated QAM Based DMT Schemes in Underwater Optical Wireless Communication

In the paper, different rotated QAM-based DMT schemes are proposed and experimentally demonstrated. To overcome the severe high-frequency fading in the underwater optical wireless communication (UOWC) channel, a deviation correction-based maximum likelihood detection (DC-MLD) is introduced into the rotated-QAM scheme. It can improve the precision of the de-rotated process and achieve a better performance than the MLD. Besides, other rotated-QAM schemes using machine learning, including k-means clustering, support vector machine (SVM), and logistic regression (LR), are investigated. These schemes do not need channel state information to achieve the de-rotated process. Meanwhile, the training overhead and execution time of SVM and LR are compared. The experimental results show that, after 5-m air and 4.2-m water channel, compared with the 16QAM DMT, the rotated-16QAM DMT can improve more than 2.5dB received optical power (ROP) sensitivity at the bit error rate (BER) of 1e-3 under the data rate of 3 Gb/s. Meanwhile, the proposed rotated-16QAM scheme with DC-MLD can save more 0.8dB ROP than that with MLD at BER of 2e-4. Besides, it has better performance than the rotated-16QAM DMT with k-means, LR, and SVM.

RIS-Assisted Visible Light Communication Systems: A Tutorial

Recent intensive and extensive development of the fifth-generation (5G) of cellular networks has led to their deployment throughout much of the world. As part of this implementation, one of the challenges that must be addressed is the skip-zone problem, which occurs when objects such as trees, people, animals, and vehicles obstruct the transmission of signals. In free-space optical (FSO) and radio frequency (RF) systems, dead zones are most often caused by buildings and trees, while in visible light communications (VLC), obstructions are caused by individuals moving around a room or objects placed in the room. A signal obstruction can significantly reduce the signal-to-noise ratio in RF and indoor VLC systems, whereas in FSO systems, where the transmitted signals are directional, the obstruction can completely disrupt data transmission. Therefore, the skip-zone dilemma must be resolved to ensure the smooth and efficient operation of 5G and beyond networks. By placing a relay between a transmitter and a receiver, the effects of obstacles can be mitigated. As a result, the signal from the transmitter will reach the receiver. In recent years, reconfigurable intelligent surfaces (RISs) that are more efficient than relays have become widely accepted as a method of mitigating skip-zones and providing reconfigurable radio environments. However, there have been limited studies of RISs for optical wireless communication (OWC) systems. Through the RIS technology, OWC and RF communication channels can be reconfigured. This paper aims to provide a comprehensive tutorial on indoor VLC systems utilizing RIS technology. The article discusses the basics of VLC and RISs and reintroduces RISs for OWC systems, focusing on RIS-assisted indoor VLC systems. We also provide a comprehensive overview of optical RISs and examine the differences between optical RISs, RF-RISs, and optical relays. Furthermore, we discuss in detail how RISs can be used to overcome line-of-sight blockages and the device orientation issue in VLC systems while revealing key challenges such as RIS element orientation design, RIS elements to access point/user assignment design, and RIS array positioning design problems that need to be studied. Moreover, we discuss and propose several research problems on integrating optical RISs with other emerging technologies, including non-orthogonal multiple access, multiple-input multiple-output systems, physical layer security, and simultaneous lightwave and power transfer in VLC systems. Finally, we highlight other important research directions that can further improve the performance of RIS-assisted VLC systems.

Corrections to “On the Capacity of Intensity-Modulation Direct-Detection Gaussian Optical Wireless Communication Channels: A Tutorial”

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Visible-light wireless communication system performance signature improvement for high bit rate transmission system

Abstract This paper deals with the visible-light communication (VLC) network system improvement for high bit rate transmission system. The previous model use the visualizer analyzer for the estimate of bit error rate in which the maxi. Q factor is reached to 2.51. The previous study is used free space channel over along length of 200 km by the optical wireless communication (OWC) channel with available data rates of 4 Gb/s. This presented model has a transmission rate of 10 Gb/s which has a maximum Q factor of 6.34 at the same operating parameters by using CW laser as an optical source and Mach–Zehnder modulator with two cascades optical wireless communication (OWC) channel.

Various transmission codes for the control of bit error rate in both optical wired and wireless communication channels

Abstract This study clarifies the data error rates optimization for OFC/OWC channels based on different transmission codes. These codes that are namely multi bits/symbol digital pulse interval modulation (DPIM), multi bits/symbol pulse position modulation (PPM), nonreturn to zero inverted (NRZI), 4 bit data symbol/5 bit code (4B5B), and Manchester for upgrading optical wired/wireless communication systems. The optical power through OFC/OWC channels, S/N ratio, the output power at the receiver side are stimulated with high bit transmission rates. The effects of coding complexity on the Q-factor, BER, optical power, and electrical received power are also stimulated using both DPIM and PPM coding.

Two Types of Mixed Orthogonal Frequency Division Multiplexing (X-OFDM) Waveforms for Optical Wireless Communication

Intensity modulation and direct detection (IM-DD) based optical wireless communication (OWC), requires the modulated signal to be real and non-negative. To satisfy the requirements, this paper proposes two types of mixed orthogonal frequency division multiplexing (X-OFDM) waveforms. The Hermitian symmetry (HS) characteristic of the sub-carriers in the frequency domain, guarantees the signal in the time domain to be real, which reduces the spectral efficiency to 1/2. For the odd sub-carriers in the frequency domain, the signal in the time domain after the inverse fast fourier transform (IFFT) is antisymmetric. For the even sub-carriers in the frequency domain, the signal in the time domain after the IFFT is symmetric. Based on the antisymmetric and symmetric characteristics, the two types of X-OFDM waveforms are designed to guarantee the signal in the time domain to be non-negative. With <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$M$ </tex-math></inline-formula> sub-carriers in the frequency domain, the generated signal in the time domain has <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$3M/2$ </tex-math></inline-formula> points, which further reduces the spectral efficiency to 1/3. The numerical simulations show that, the two types of X-OFDM waveforms greatly enhance the power efficiency considering the OWC channel with the signal-dependent noise and/or the signal-independent noise.

Water-Wave Effect on the Encryption and Deep-Learning-Based Recognition of a Speech Signal Transmitted Over a Wireless Optical Communication Channel

Water-Wave Effect on the Encryption and Deep-Learning-Based Recognition of a Speech Signal Transmitted Over a Wireless Optical Communication Channel