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Review

Advancements and Challenges of Visible Light Communication in Intelligent Transportation Systems: A Comprehensive Review

by
Prokash Sikder
1,
M. T. Rahman
1,* and
A. S. M. Bakibillah
2,*
1
Department of Computer Science and Engineering, University of Asia Pacific, Dhaka 1205, Bangladesh
2
Department of Systems and Control Engineering, School of Engineering, Institute of Science Tokyo, Tokyo 152-8552, Japan
*
Authors to whom correspondence should be addressed.
Photonics 2025, 12(3), 225; https://doi.org/10.3390/photonics12030225
Submission received: 30 December 2024 / Revised: 17 February 2025 / Accepted: 27 February 2025 / Published: 28 February 2025
(This article belongs to the Special Issue Advancements in Optical Wireless Communication (OWC))
Browse Figures
Versions Notes

Abstract

:
Visible Light Communication (VLC) has the potential to advance Intelligent Transportation Systems (ITS). This study explores the current advancements of VLC in ITS applications that may enhance traffic flow, road safety, and vehicular communication performance. The potential, benefits, and current research trends of VLC in ITS applications are discussed first. Then, the state-of-the-art VLC technologies including overall concept, IEEE communication protocols, hybrid VLC systems, and software-defined adaptive MIMO VLC systems, are discussed. We investigated different potential applications of VLC in ITS, such as signalized intersection and ramp metering control, collision warning and avoidance, vehicle localization and detection, and vehicle platooning using vehicle–vehicle (V2V), infrastructure–vehicle (I2V), and vehicle–everything (V2X) communications. Besides, VLC faces several challenges in ITS applications, and these concerns, e.g., environmental issues, communication range issues, standards and infrastructure integration issues, light conditions and integration issues are discussed. Finally, this paper discusses various advanced techniques to enhance VLC performance in ITS applications, such as machine learning-based channel estimation, adaptive beamforming, robust modulation schemes, and hybrid VLC integration. With this review, the authors aim to inform academics, engineers, and policymakers about the status and challenges of VLC in ITS. It is expected that, by applying VLC in ITS, mobility will be safer, more efficient, and sustainable.

1. Introduction

1.1. Background and Potential of VLC in ITS

For the past few decades, continuous efforts have been made by researchers and policymakers to enhance transportation operations in terms of efficiency, safety, and environmental effects [1,2]. Using data and communication technology, intelligent transportation systems may provide a viable solution to reduce traffic congestion and accidents, improve traffic flows, and enhance sustainability [2]. However, traditional radio frequency (RF) communication, a cornerstone of ITS, has considerable limitations in urban areas with dense populations [3,4]. The electromagnetic interference (EMI), spectrum congestion, and security issues are some of the downsides of RF technology [5]. Interference from electromagnetic fields caused by electrical devices and other wireless systems can lower the quality and dependability of RF signals and the ever-increasing demand for RF capacity results in restricted channel availability. RF transmission is susceptible to eavesdropping and jamming, which creates security threats [6]. Recently, VLC arrived with numerous advantages due to its resilience to electromagnetic interference. VLC runs in an unregulated spectrum, which allows it to escape the congestion and spectrum inefficiencies associated with RF communication [7]. As a result, it is possible to provide communication channels that are more dependable and secure for ITS applications [8].
The integration of VLC in ITS enables various communication scenarios, including V2V, V2I, and I2V communications [9]. VLC systems address the practical requirements of ultra-low latency transmission of short packets, which are essential for ITS applications, such as autonomous braking and car platooning [10]. Some experimental analyses have been conducted to characterize the field of view (FOV) in VLC systems for ITS applications, emphasizing the need for optical and extended FOV analyses to support V2I and I2V communications in vehicular environments [11]. VLC-based networking’s scalability and its difficulties have been emphasized, underscoring the necessity of effectively utilizing VLC as a network technology to facilitate V2V communication in ITS [12]. Furthermore, the evaluation of VLC technology has highlighted its potential in ITS and suggested possible uses in vehicular communications [13,14]. VLC has been found to contain intrinsic security features, including spatial confinement and directional propagation, which emphasize its potential for safe V2V communication in some situations [15]. Moreover, the high-bandwidth properties of micro-light-emitting diodes (LEDs) have made their usage in VLC increasingly popular [16], which enables V2I and V2V communication in ITS.
VLC technology’s capacity to facilitate V2V communication in vehicle safety applications has been demonstrated, highlighting its potential to improve safety-critical situations [17]. There is potential for expanding V2V communication in ITS thanks to innovative methods, such as using LED current pulse position modulation (PPM) to increase the range of V2V–VLC communication links [17,18]. The potential for V2V communication in ITS has been indicated by the analysis and experimentation of wireless optical communications to support information-sharing applications using VLC communications [19]. Performance and diversity aspects, which are essential for dependable V2V communication in ITS, are highlighted with inclusive modelling of V2V–VLC systems [20,21]. The development of noise-adaptive VLC receivers has been suggested, indicating advancements in addressing challenges for V2V communication in automotive applications [22]. The security performance analysis of NOMA-assisted underwater VLC systems has shown the potential for secure V2V communication in challenging environments, such as underwater applications [23]. Additionally, optimization of bi-directional hybrid VLC/RF-based Internet of Things (IoT) systems was proposed in [24], combining VLC and RF for potential benefits in V2V communication for future 6G applications [25].
The evaluation of a new RF technology and VLC for platooning applications has been emphasized, indicating the potential for VLC V2V communications [26]. According to a proposed performance analysis method for adaptive OFDM modulation techniques in VLC vehicular communication networks, V2V communication may be supported in realistic noise situations [27]. The classification of full-duplex VLC channels for city tunnels has been studied for the potential of V2I and V2V communication in challenging vehicular environments [28]. The feasibility of obstacle awareness forwarding schemes in V2V VLC networks has been proposed, emphasizing the spatial flexibility of VLC networks for V2V communication in various circumstances [29]. A software-defined multi-element VLC architecture has been proposed, indicating the potential for high throughput and energy-efficient V2V communication in ITS [30,31]. The choice of VLC technology depends on specific ITS application requirements, including data rate needs [7], coverage range, cost constraints, and environmental conditions. Each technology offers unique benefits that can be harnessed to address the diverse challenges faced in the deployment of ITS [32], contributing to more efficient, safe, and sustainable transportation systems.

1.2. Benefits of VLC over RF and Other Technologies

For ITS applications, VLC emerges as a tempting alternative to RF communication by using LEDs to modulate light pulses for data transmission, offering several significant advantages. Additionally, laser diodes (LDs) provide higher data rates and longer transmission distances compared to LEDs [33], making them ideal for high-performance ITS applications, like long-range vehicle-to-infrastructure communication [34]. Recent advancements in LD technology have improved power efficiency and reduced costs, enhancing their suitability for long-range ITS applications [35]. The advantages of VLC are as follows:
(i) Immunity to electromagnetic interference: VLC is very useful in locations with significant wireless communication activities, (e.g., densely populated urban areas) because VLC is immune to electromagnetic interference [36,37].
(ii) Usage of unregulated spectrum: To avoid the congestion and spectrum inefficiency associated with RF communication, VLC operates in an unregulated light spectrum [36]. As a result, it is possible to provide more dependable and secure communication channels for ITS applications [12].
(iii) Enhanced security: Compared to RF communication, VLC is naturally more secure against security threats and hacking because the propagation of light in VLC cannot penetrate solid obstacles [38,39].
(iv) Cost-effectiveness: VLC is a cost-effective solution that uses the existing lighting infrastructure and doesn’t require a license to operate [40]. Therefore, it is an affordable communication option for ITS. Compatibility with existing infrastructure further enhances its effectiveness in transportation systems [41].
(v) High data rate: Recent developments in modulation techniques and optical components have allowed VLC systems to achieve gigabit-per-second data rates, which open the door for next-generation wireless communication systems [42]. Thus, VLC can handle the growing demands of data intensive ITS applications.
(vi) Energy efficiency: According to [43], VLC is used for illumination and communication together, providing energy efficiency and presenting a communication option for ITS that is both sustainable and environmentally friendly.
Therefore, VLC is a promising technology for addressing the communication requirements of ITS because it offers immunity to interference, operation in an unregulated spectrum, economic prospects, enhanced security, cost-effectiveness, high data rate potential, energy efficiency, and minimal impact on health.

1.3. Current Research Trends of VLC in ITS

Several studies have demonstrated the feasibility and potential of VLC in ITS applications [44,45]. Additionally, researchers have explored the impact of environmental factors (such as sunlight, fog, rain, and snow) on VLC in ITS applications to provide a broad understanding of the practical challenges and limitations [46]. Specifically, fog releases water droplets into the atmosphere, which have the same properties as rain and can scatter, absorb, and weaken the light signal. Saturation of optical receivers due to direct sunlight is a serious challenge in outdoor VLC system design for vehicle applications, reducing maximum communication range and causing performance deterioration when transmitter and receiver are in proximity. The extra layer of snow on devices like the VLC transmitter or receiver introduces additional barriers that impede or weaken the light signal and reduce the communication performance of VLC systems. The growing interest in VLC in ITS applications is evidenced by the increasing number of research works, prototypes, field trials, and standardization activities [47]. Current research trends in VLC for ITS applications are given in Table 1.

1.4. Contributions and Assessment with Existing Reviews

This review offers a comprehensive and up-to-date analysis of the burgeoning field of VLC in ITS, distinguishing itself from previous studies by providing a more granular exploration of the interplay between VLC technology advancements and their practical implementation in ITS. While prior research has often focused on theoretical frameworks or specific application case studies, this review delves deeper into the intricacies of integrating VLC into real-world transportation systems. A key contribution lies in the emphasis on the role of emerging technologies, such as micro-LEDs, in driving VLC performance and expanding their capabilities in ITS. By examining the challenges posed by environmental factors and proposing practical solutions, this review offers valuable insights for researchers and practitioners seeking to optimize VLC systems for outdoor environments. Furthermore, this review offers a more holistic perspective by systematically exploring the various communication types employed in VLC-based ITS. This approach enables a more nuanced understanding of technology’s potential to address ITS challenges. By providing a comprehensive overview of the current state-of-the-art, identifying key research gaps, and outlining future research directions, this review serves as a valuable resource for academic and industry practitioners seeking to advance the field of VLC in ITS. Table 2 shows a comparison of this review with other recent reviews on VLC.

1.5. Organization of the Paper

The paper is structured as follows. Section 2 describes state-of-the-art VLC technologies including the concept of VLC systems, VLC protocols in ITS, hybrid VLC technology, and software-defined adaptive MIMO VLC. Section 3 describes advancements of VLC in ITS applications, such as signalized intersections and merging roads, cooperative collision warning/avoidance systems, vehicle localization and detection systems, and vehicle platooning systems. Section 4 discusses the challenges and limitations of VLC in ITS applications with environmental factors, limited range and non-line-of-sight communication, standardization and integration with existing infrastructure, and light conditions and sensitivity. Section 5 discusses advanced techniques for enhancing VLC performance with machine learning-based channel estimation, adaptive beamforming, robust modulation schemes, and hybrid VLC–RF integration. Section 6 provides future research directions, and Section 7 provides the conclusion.

2. State-of-the-Art VLC Technologies

2.1. Concept of VLC System in ITS

VLC is a cutting-edge technology that leverages the visible light spectrum for wireless data transmission. Operating within the wavelength range of 400 to 800 THz (780–375 nm), VLC offers a promising alternative to traditional RF communication for ITS applications [56]. At the core of a VLC system, there are three essential components. First, LEDs serve as transmitters, and the primary function is illumination, which can be rapidly modulated to encode data. Their energy efficiency, long lifespan, and ability to adjust have quickly made them ideal for this purpose [57]. Second, photodetectors act as receivers, transforming the incoming modulated light into electrical signals. This conversion enables the extraction of the primary data. Photodiodes and avalanche photodiodes are commonly employed for this task [58]. Moreover, cameras can be used as receivers, since they are available in vehicles and suitable for precise location estimation [59]. Cameras can capture the light signal transmitted in a VLC system, in which the light source is modulated to transport data, and cameras serve as the receiver to decode the information. The third component is the communication channel, which is simply the air. The modulated light is then transmitted through the air and captured by photo-detectors. However, factors such as distance, ambient light, and obstructions can significantly impact the quality of data transmission [60]. Thus, channel modeling is essential for designing, analyzing, and optimizing VLC systems, like in other communication systems.
Numerous studies have emerged under the assumption that automotive and streetlight LED sources follow a Lambertian emission model [61,62,63]. While Lambertian emission is useful for interior VLC communication, it does not fit the lighting characteristics of vehicle lights and streetlights with their asymmetrical distributions [13]. Most car lights, particularly headlights, have a specified asymmetrical radiation pattern in which the light is directed more fiercely towards the road surface on the driver’s side to avoid blinding oncoming traffic. Streetlights have tight beam angles in the vertical plane to focus light onto road surfaces, and wide beam angles in the horizontal plane to enhance the distance illuminated along the road. Some recent studies have designed VLC channel models considering asymmetrical patterns of vehicle lights and streetlights [64,65].
Advanced modulation techniques, including duobinary, quadrature phase shift keying (QPSK) [66], and index modulation-aided OFDM, have been developed to enhance data transmission rates [67]. Moreover, recent advancements in carrier synchronization and clock recovery algorithms have significantly improved the overall performance of VLC systems by optimizing modulation and demodulation processes [68]. In essence, VLC harnesses the potential of LEDs as both light sources and data carriers. LED-based streetlights, traffic lights, and automotive exterior lighting make VLC a viable wireless communication solution for vehicular networks. Ongoing research focuses on developing high-efficiency LED drivers and integrating LED driving circuits with communication circuits to further optimize VLC systems and expand their applications [64,69]. Figure 1 illustrates the concept of VLC technology for V2V and I2V (or V2I) communications in ITS applications. VLC provides high-bandwidth communication in direct connection using an LoS link. Vehicles can also communicate or receive information via an NLoS link when the signal from a car is reflected onto an obstacle and reaches the destination car. Moreover, RF links may serve as a complementary solution for NLoS scenarios, such as when vehicles are obstructed by buildings or other obstacles. The use of streetlights as VLC access points creates a decentralized communication infrastructure, minimizing latency and network congestion. The VLC system consists of both LoS and NLoS links for sharing information [70]. The total channel gain is the sum of the LoS channel gain and NLoS channel gain. LoS communication can further benefit car-following behavior, emergency braking, and platooning of autonomous vehicles [71,72,73,74], whereas NLoS communication can improve lane-changing behavior, overtaking, merging of AVs, and autonomous parking [75,76,77,78].

2.2. VLC Protocols in ITS

A wide variety of IEEE standards, such as 802.11bb, 802.15.13, 802.15.4, ITU-T G.9991, ITS-G5, 802.15.7-802.11p and 802.15.7-2018, are defined for optical wireless communication protocols that are pertinent to ITS applications [47]. The IEEE 802.15.7 standard concerns wireless communication in vehicular environments and is compliant with ultra-low latency relaying VLC systems, which are crucial for safety-critical ITS applications [10,18]. The IEEE 802.11p protocol is significant for dedicated short-range communications (DSRC) systems in ITS applications [47]. This protocol serves as a supplementary protocol to 802.11 in order to meet the relevant applications of ITS in DSRC systems [79]. IEEE 802.11bb is a line-of-sight light-based wireless networking standard from the 802.11 family of standards that defines an interoperable communications protocol for Li-Fi devices [80]. The IEEE 802.15.13 is a standard for high-speed optical wireless communication, enabling multi-gigabit data rates using light wavelengths [80]. The IEEE 802.15.4 standard is relevant for wireless personal area networks (WPANs), including wireless sensor networks and IoT devices, and can also be considered for ITS [81]. ITU-T G.9991 is a standard for indoor line-of-sight optical networking [82]. The European Telecommunications Standards Institute (ETSI) group for ITS contributes to the advancement of communication systems for intelligent vehicles (ITS-G5), particularly in Europe [83]. The IEEE 802.15.7-2018 standard is a pivotal communication protocol for VLC, specifically designed to support short-range optical wireless communication for local and metropolitan area networks [84]. This standard provides access to several hundred terahertz of unlicensed spectrum, immunity to electromagnetic interference, and noninterference with radio frequency systems. Key aspects of the IEEE 802.15.7-2018 standard include the following:
➢
Physical Layer (PHY): Defines three different PHY layers to cater to varied data rates and distances.
➢
Medium Access Control (MAC) Layer: Ensures efficient use of the communication medium by managing access and avoiding collisions.
➢
Support for Mobility: Designed to handle the challenges associated with mobile receivers, which is critical for ITS applications.
➢
Data Security: Provides encryption mechanisms to ensure secure communication, which is vital for ITS data integrity. Specifically, it provides additional security by allowing the user to see the communication channel, this communication augmenting and complementing existing services.
Table 3 provides the current standard communication protocols relevant to ITS.
A robust MAC layer that manages channel access and prevents data collisions is provided by the IEEE 802.15.7-2018 and 802.15.7-2011 standards. Using TDMA and CSMA/CA protocols [85], the MAC layer ensures reliable data transmission in environments with multiple active VLC devices. These standards provide Multiple Physical layers to accommodate diverse ITS applications. These layers support varying data rates and transmission distances, enabling efficient communication between vehicles and infrastructure while meeting the bandwidth requirements of pedestrian signaling systems. Security is essential for ITS applications due to sensitive data. Strong data encryption is provided by IEEE 802.15.7, which uses AES and secure key management to secure communication and prohibit unauthorized access, interception, and data modification. In summary, ITS needs IEEE 802.15.7-2018 for visible light communication, as it ensures reliable, efficient, and secure communication.

2.3. Hybrid VLC Technologies

Through the utilization of a wide variety of light sources and hybrid systems, VLC technology has the potential to effectively improve performance and meet specific challenges associated with ITS. The purpose of hybrid VLC–RF systems is to develop a communication network for ITS that is more durable and reliable by combining the strengths of both VLC and RF technologies. VLC can be utilized for high-speed, short-range communication in hybrid systems, while RF can be employed as a backup or additional communication medium in situations where VLC signals are hindered or when illumination conditions are not suitable. Data transfer can be ensured without interruption by using RF communication, which can take over perfectly in tunnels or adverse weather circumstances. Specifically, in ITS environments, vehicles can communicate with the cellular base station using cellular V2X or VLC–RF communications to receive information on traffic states and decide their desired actions, e.g., platooning, path planning, optimal motion planning, etc., in a centralized/decentralized manner. Also, VLC–RF communication links can be established with roadside infrastructure, e.g., lamp posts, where direct communication with the base station is infeasible, and vehicles can receive necessary information locally from nearby roadside lamp posts. The concept of hybrid VLC–RF communication in ITS is shown in Figure 2. Moreover, the hybrid system supported by a free-space optics/visible light communication (FSO-VLC) system can be applied to ITS applications. Huang et al. [86] designed a hybrid optical wireless network based on FSO-VLC heterogeneous interconnection for future space-air-ground-ocean (SAGO)-integrated communication, particularly in radio-frequency-sensitive (RF) or security-required environments. This hybrid technique utilizes VLC’s fast data rates and other security features for reliable communication [87]. Consequently, it enhances the system’s overall performance and dependability in challenging and dynamic ITS environments [88]. Combining the advantages of both technologies, hybrid VLC–RF networks offer reliable and large-capacity channels for communication. In densely populated areas where interference and spectrum crowding are major problems, this combination is helpful. Hybrid networks can improve overall network performance, lower latency, and increase connection [89].

2.4. Software-Defined Adaptive MIMO VLC

Multiple Input Multiple Output (MIMO) VLC is a software-defined adaptive system for optical wireless communication that utilizes different techniques, such as orthogonal frequency division multiplexing (OFDM), dimming control, hybrid VLC–RF systems, light fidelity (Li-Fi), and free-space optics (FSO) [90]. Several LEDs and photodetectors are also used in this technique to establish numerous active communication channels [91], which improves the system’s dependability and robustness, increasing data transmission rates [92]. This system’s flexibility allows it to optimize in real-time based on user needs and changing environmental conditions, making it suitable for ITS applications. In complex ITS environments, VLC systems can further provide high data speeds, reliable communication, and dynamic adaptability by integrating software-defined adaptive MIMO. Researchers developed 4 × 4, 8 × 8, and 16 × 16 MIMO VLC testbeds that can dynamically adjust their transmission parameters depending on channel conditions to show a real-world implementation of an adaptive MIMO VLC system. The system switched between spatial multiplexing for high data rates and spatial variety by using a set of silicon photodiodes as receivers and a range of high-brightness LEDs as transmitters in standard settings [65]. At the receiver, Zero-Forcing (ZF) and MMSE-based detection are used to reduce interference and improve reliability. According to experimental results, the system automatically adjusted its parameters to maintain a bit error rate (BER) below 10−3 under ideal circumstances and a data flow up to 60 Gbps [93]. This implementation demonstrated the feasibility of adaptive MIMO VLC for high-speed wireless communication, paving the way for next-generation LiFi networks [94].

3. Advancements of VLC in ITS Applications

With an emphasis on improving safety, streamlining transportation management, and optimizing traffic flow, ITS has become a key component of modern transportation [47,95,96]. The integration of VLC into ITS is examined in this study, along with how it might be used to address important issues in vehicular networks. This study explores the potential of VLC in ITS applications, such as driver localization and recognition, cooperative collision warning and avoidance, ramp metering, traffic signal synchronization, and vehicle platooning to help develop intelligent and robust transportation systems.

3.1. Signalized Intersections and Merging Roads

Since intersections and merging roads are one of the main causes of traffic bottlenecks on urban roads, an innovative strategy to improve traffic management and reduce traffic congestion at urban intersections is the incorporation of VLC technology into traffic light synchronization [97]. Specifically, the traffic flow can be enhanced and trip times can be decreased at urban intersections by controlling traffic signals using V2I or I2V VLC applications. Traffic lights with VLC capabilities can interact with cars to dynamically modify signal timings in response to real-time traffic circumstances. This can enhance overall traffic efficiency, mitigating traffic bottlenecks and idling time at intersections. Effective traffic signal synchronization depends on the exact localization capacity of VLC [98], which enables precise vehicle identification and traffic flow analysis [99]. VLC technology can also be used in ramp metering control systems to control the flow of cars entering highways from merging roads. VLC-enabled ramp meters can reduce congestion and enhance highway traffic flow by regulating the rate of vehicle entry via communication with oncoming cars. By preventing bottlenecks and guaranteeing a more equitable allocation of traffic throughout the road network, this real-time communication improves the effectiveness, capacity, and security of highway operations [100].

3.2. Cooperative Collision Warning/Avoidance System

This application shows how VLC can be used to deliver precise and timely traffic updates, improving driver awareness and avoiding collisions. Vehicles with VLC receivers can obtain real-time information regarding traffic conditions, vehicle states, accidents, and roadworks via V2V or I2V communications by embedding VLC transmitters in other vehicles and roadside infrastructure. Vehicles can communicate with each other regarding their positions, speeds, and trajectories to coordinate operations. Such a V2V VLC system can advance the cooperative adaptive cruise control (CACC) of automated vehicles to warn drivers when safety gaps are below the minimum requirements, or to avoid collisions by applying emergency braking. Moreover, when a road is blocked due to traffic accidents, drivers can avoid clogged roads, make better decisions, and enhance overall traffic flow with immediate VLC-based communications [19]. In ITS, cooperative collision avoidance systems based on VLC have been studied to improve vehicle safety by using cutting-edge modulation techniques to extend the range of vehicular VLC communications. This real-time data exchange is essential for the advancement of advanced driver assistance systems (ADAS) and autonomous driving, which improves road safety [101].

3.3. Localization and Vehicle Platooning System

VLC technology uses light signals from LED-based infrastructure to provide accurate vehicle localization. For applications like parking assistance, car tracking, and automated navigation, precise localization is essential. Advanced features like autonomous driving and improved situational awareness in connected vehicle systems are made possible by VLC’s ability to supply high-resolution localization data [102]. VLC technology has been proposed for vehicle platooning, offering a promising solution to enhance the coordination and communication among vehicles in platoons. Within the platoon, VLC can provide inter-vehicle communication, allowing for the sharing of information on lane changes, braking, speed adjustments, etc. These guarantees can coordinate movements and improve platoon operations. Recently, a lightweight V2V optical wireless communication and sensing framework known as Vehicle Talk has been developed to improve communication robustness and lower system latency for platooning [103]. Platooning can increase road capacity, decrease aerodynamic drag, and improve fuel efficiency by keeping vehicles close to one another [104].

4. Challenges and Limitations of VLC in ITS Applications

There are some challenges and limitations of visible light communication in outdoor environments. Such issues should be considered when designing a VLC system for ITS applications.

4.1. Environmental Factors

VLC systems are vulnerable to weather conditions, including fog, rain, and snow, particularly outdoors. Due to the dispersion and attenuation of light signals, these conditions can have a significant impact on the reliability of data transmission. Although theoretical models have shed light on how these parameters affect signal strength, a thorough experimental validation of these effects is required to fully comprehend VLC performance in real-world circumstances. For example, fog causes signal attenuation and reduction in communication range by scattering light, which lowers visibility. Likewise, absorption and scattering caused by rain and snow further reduce SNR and the dependability of data transmission. These unfavourable circumstances make it difficult for VLC systems to operate consistently in ITS applications where continuous communication is essential for efficiency and safety.

4.2. Limited Range and Non-Line-of-Sight Communication

The limited visibility and non-line-of-sight communication of VLC present another major obstacle for ITS applications. Compared to RF systems, VLC systems usually have a shorter communication range. The main cause of this restriction is the fact that visible light moves in linear patterns and is vulnerable to barriers. As a result, non-line-of-sight communication, where the transmitter and receiver are not in direct line of sight, can be challenging to achieve with VLC [105]. The limited range of VLC also poses challenges for applications in large-scale ITS deployments, where extensive coverage is required. Additionally, the need for line-of-sight communication can be a limitation in scenarios where obstacles or environmental conditions obstruct the direct transmission of visible light signals, thereby hindering the effectiveness of VLC for ITS applications [39].

4.3. Standardization and Integration with Existing Infrastructure

Standardization and integration with existing infrastructure present significant challenges for the adoption of VLC in ITS applications. The lack of standardized protocols and communication standards for VLC in the context of ITS can hinder interoperability and compatibility with existing transportation systems. This can lead to difficulties in integrating VLC-based communication with the current infrastructure, including traffic management systems, V2I or I2V communications, and other ITS components [14]. Moreover, the integration of VLC with existing infrastructure may require substantial modifications and investments to accommodate the specific requirements of VLC-based communication. This can include the installation of VLC transmitters and receivers, as well as the implementation of supporting infrastructure, such as lighting fixtures and optical access points. The lack of standardized guidelines and protocols for such integration can impede the seamless deployment of VLC for ITS applications [106].

4.4. Light Conditions and Sensitivity

The ambient light level has a significant impact on VLC system performance. Significant interference can be introduced by elements like sunshine and artificial illumination, which lowers the signal-to-noise ratio (SNR) and affects the dependability and quality of data transmission. Sunlight interference is a major problem that can have a big impact on a VLC systems’ performance.
Signal deterioration and decreased communication reliability may result from interference [11,12]. Similarly, artificial lighting from sources such as streetlamps or headlights can create interference, complicating the ability to maintain a stable VLC communication link [107]. These ambient light sources contribute to higher levels of noise in the channel, which in turn leads to increased bit error rates and data loss. Figure 3 illustrates various factors influencing the VLC transmission link, which can be addressed using different modulation schemes and coding techniques.

5. Advanced Techniques for Enhancing VLC Performance

5.1. Machine Learning-Based Channel Estimation

One of the main challenges to the VLC link is maintaining high-quality communication in adverse environments, where factors like vehicle movements, environmental interference, and obstacles can degrade signal quality. Traditional channel estimation techniques may not adapt well to such variations. However, machine learning-based channel estimation can learn from real-time data and dynamically predict the best parameters for optimal signal transmission [108]. By applying supervised or reinforcement learning algorithms, VLC systems can be trained to estimate the channel state and adapt to changing conditions in real-time. This reduces the need for constant recalibration, allowing for more stable communication in vehicular environments. To further increase system robustness, machine learning can help enhance modulation and error correction systems.

5.2. Adaptive Beamforming

Another cutting-edge signal processing method that can greatly enhance VLC performance is adaptive beamforming. By directing light beams toward receivers (such as cars or infrastructure), the transmitter in VLC systems, usually an LED array, can increase signal strength in those directions and lessen interference. Adaptive beamforming enables VLC systems to dynamically modify the transmitted light’s intensity and direction according to the receiver’s position and the obstructions in its immediate environment [109]. This is especially helpful when cars move quickly or in crowded urban areas [110]. Even in the presence of transient obstacles, adaptive beamforming helps to preserve communication by continuously adjusting the beam’s direction. Different adaptive beamforming techniques have been proposed in the literature. Sang et al. [103] developed optimal and robust secure beamforming techniques for multiple-input single-output (MISO) VLC systems considering both NLoS channel gain and inter-symbol interference (ISI). Delwar et al. [6] designed a hemispherical visible light transmitter for multi-users, employing optical beamforming (OB) techniques for VLC systems.

5.3. Noise Cancellation and Adaptive Filtering

Robust noise cancellation approaches can be used to filter out undesired background light to lessen the impacts of ambient light interference [111]. To retain the best possible signal quality, adaptive filtering algorithms can constantly modify the VLC receiver’s sensitivity depending on the current illumination circumstances. VLC systems can make real-time adjustments to lessen the effects of ambient noise by continuously measuring the amount of light in the surrounding area.

5.4. Robust Modulation Schemes

To increase resistance against fluctuations in ambient light, VLC systems can incorporate robust modulation strategies, like Orthogonal Frequency Division Multiplexing (OFDM) and Pulse Position Modulation (PPM) [112]. Certain modulation techniques can better preserve signal integrity because they are less susceptible to noise. Even in nonideal lighting circumstances, data can be reliably transferred by combining robust modulation with error-correcting codes [113].

5.5. Exploring Faster Light Sources

The usage of LDs is one promising way to get around LEDs’ bandwidth restrictions. Compared to LEDs, LDs have considerably higher bandwidth modulation, enabling faster data transfer. LDs can modulate light at significantly higher frequencies, which leads to faster data rates than LEDs, which have slower switch times. LDs are also more energy efficient and provide superior directional control, which makes them suitable for applications that need high-speed data transfer or long-range communication. VLC systems can overcome present bandwidth limitations and achieve data transmission speeds that are on par with or faster than other communication technologies by combining faster light sources, such as LDs, with sophisticated modulation algorithms, such as DMT and CAP.

5.6. Hybrid VLC–RF Integration

The development of hybrid VLC–RF systems can guarantee continuous communication by enabling a smooth transition between VLC and RF technologies in the event of a loss of LoS. VLC can manage short-range, high-bandwidth communication under clear LoS conditions [114] but, in NLoS situations, RF can take over to provide continuous coverage and increase the communication range [115]. Combining the benefits of both systems, this hybrid method not only reduces the LoS dependency but also makes the ITS communication system more robust and adaptable [116].

6. Future Research Directions

Future research could focus on several areas to improve the performance and application of VLC systems. One important area is improving adaptability to environmental conditions, especially in areas where light waves fluctuate significantly. Researchers could investigate advanced adaptive beamforming techniques to help direct signals more efficiently, reducing interference from surrounding light sources and improving reliability in fluctuating environments. Developing self-optimizing VLC networks that automatically adjust parameters, such as power levels, modulation schemes, and beam direction based on different factors, e.g., obstacles, weather, or interference from nearby light sources, could be potential future research works. Advanced algorithms for dynamic route management could be developed to maintain high-quality communication in urban or highly obstructed areas. The development of high-precision positioning systems that enable precise localization of transmitters and receivers in intricate, highly dynamic settings should be a priority for researchers when VLC technology enters practical use cases, like autonomous vehicle networks. Real-time traffic management and V2X communications could be enhanced by integrating VLC with other sensor systems, such as radar and LiDAR, which could provide complementary benefits [117].
Further work is also needed to enhance the performance of VLC systems based on hybrid modulation algorithms, particularly in high ambient light conditions. The hybrid VLC–RF and VLC-FSO frameworks ought to integrate noise-resistant modulation approaches suitable for adjustment in different light conditions, with adaptive filtering strategies. Integrating machine learning-based anticipatory noise filtering algorithms is an intriguing method that may enable VLC systems to predict and compensate for changing ambient illumination. Improving VLC’s interoperability with other communication technologies, such as Wi-Fi, 5G, and traditional RF-based systems, would also require more effort [118]. The seamless transitions between communication modalities with low latency will enable a fully hybrid communication infrastructure that takes advantage of each system’s capabilities. This would considerably increase their immunity to interference and improve communication quality in dynamic lighting circumstances.
Standard LED bulbs may be unsuitable for high-speed data transfer, necessitating specialized LEDs with faster response times, which can be more costly. Photo-detectors used in VLC receivers must be sensitive enough to detect faint modulated light signals, which might increase the cost of the receiver device. Additional optical filters may be required to reduce interference from ambient light, particularly in bright areas, which increases system cost. Integrating VLC capabilities into existing lighting systems may necessitate changes to fixtures and wiring, increasing the overall cost of deployment. The primary cost constraints in VLC for ITS applications are the need for specialized LED fixtures with high modulation capabilities, complex receiver designs, the potential need for additional optical filters to mitigate interference from ambient light, and the cost of integrating VLC functionality into existing lighting infrastructure, particularly when RGB LEDs are used for color control, which can be more expensive than standard white LEDs. To minimize the cost of the receiver, more economical photodetector technologies should be investigated, using efficient modulation techniques to maximize data transfer while consuming minimal power. Developing industry standards for VLC systems may result in reduced component costs in practical ITS applications.
Improved NLoS communication is another crucial topic. Future research should concentrate on improving the techniques that allow VLC systems to perform well in situations where obstructions prevent direct line-of-sight, such as in urban environments or complex traffic situations. Depending on surroundings, these devices may dynamically switch between light-based and RF communication, guaranteeing continuous connectivity. For instance, the system might seamlessly transition to RF communication when fog, heavy rain, or obstructions impair VLC performance. Furthermore, field studies employing reflecting surfaces, such as buildings, cars, and road signs in real-world settings, will offer important insights into how VLC systems can overcome the inherent drawbacks of LoS communication.
Strong cybersecurity is crucial as VLC systems are increasingly employed in ITS applications. VLC systems are still susceptible to threats, such as jamming, spoofing, and signal interception, etc. Therefore, creating sophisticated cybersecurity measures will be essential to safeguarding private information and guaranteeing the integrity of communication networks. Particularly in crucial ITS applications, researchers should develop cutting-edge encryption techniques that protect VLC broadcasts, making them impervious to online attacks and guaranteeing secure and dependable communication. The effectiveness of VLC should be better assessed in future research by focusing on field testing in real-world driving conditions, such as high-speed freeways, signalized intersections, merging roads with ramp metering, crowded urban areas, and tunnels, where a variety of infrastructures, including various kinds of streetlights, traffic signals, and road layouts should be considered for an accurate performance evaluation.
Finally, even though VLC has demonstrated a great deal of promise, several potential future paths could expand its functionality in ITS applications. These include addressing cybersecurity issues to safeguard vital data in ITS environments, integrating VLC with the IoT for better communication amongst connected and automated vehicles, utilizing artificial intelligence (AI) to optimize communication protocols and system management, and investigating the application of VLC for intelligent vehicles [119]. To improve the efficacy, security, and reach of VLC systems within ITS and ultimately open the door to safer, more intelligent, and more effective transportation networks, each of these domains offers distinct difficulties as well as valuable probabilities.

7. Conclusions

This paper presents an extensive review of integrating Visible Light Communication (VLC) technology into Intelligent Transportation Systems (ITS). It systematically examines the potential of VLC to enhance traffic efficiency, safety, and overall system performance, drawing on an analysis of current literature. VLC offers significant benefits over traditional RF-based communication technologies, including high data rates, low latency, and built-in security. Moreover, the application of VLC in several ITS scenarios, such as signalized intersections, ramp metering, cooperative collision warning/avoidance, vehicle localization, and platooning are also discussed. It also emphasizes the importance of different communication types (I2V, V2V, and V2I) for realizing the full potential of VLC. However, the paper also identifies challenges that must be addressed for widespread VLC adoption in ITS, including environmental factors, limited range, and security concerns. Future research should aim to develop robust and adaptive VLC systems, explore hybrid VLC–RF solutions, and address issues of standardization and interoperability. Integrating VLC with emerging technologies, like IoT, AI, and cybersecurity, could significantly transform ITS. By overcoming current challenges and leveraging future opportunities, VLC can play a pivotal role in creating intelligent, sustainable, and safe transportation systems.

Author Contributions

Conceptualization, P.S., M.T.R. and A.S.M.B.; methodology, P.S., M.T.R. and A.S.M.B.; validation, M.T.R. and A.S.M.B.; investigation, M.T.R. and A.S.M.B.; resources, M.T.R. and A.S.M.B.; writing—original draft preparation, P.S.; writing—review and editing, M.T.R. and A.S.M.B. All authors have read and agreed to the published version of the manuscript.

Funding

This research received no external funding.

Institutional Review Board Statement

Not applicable.

Informed Consent Statement

Not applicable.

Acknowledgments

Authors would like to thank the Institute of Energy, Environment, Research and Development (IEERD), UAP, for providing research facilities.

Conflicts of Interest

The authors declare no conflicts of interest. The funders had no role in the design of the study; in the collection, analyses, or interpretation of data; in the writing of the manuscript, or in the decision to publish the results.

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Figure 1. The concept of visible light communication for V2V and V2I (or I2V) in ITS applications. The VLC system consists of both LoS and NLoS links for sharing information.
Figure 1. The concept of visible light communication for V2V and V2I (or I2V) in ITS applications. The VLC system consists of both LoS and NLoS links for sharing information.
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Figure 2. The hybrid VLC–RF systems in ITS applications. The vehicles can communicate with a cellular based station using VLC–RF communications or cellular V2X. When there is a sudden incident, the vehicle can communicate with other vehicles in the next lane for a lane change action via cellular V2X communication.
Figure 2. The hybrid VLC–RF systems in ITS applications. The vehicles can communicate with a cellular based station using VLC–RF communications or cellular V2X. When there is a sudden incident, the vehicle can communicate with other vehicles in the next lane for a lane change action via cellular V2X communication.
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Figure 3. Factors influencing the VLC transmission link.
Figure 3. Factors influencing the VLC transmission link.
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Table 1. Current Research trends in VLC for ITS applications.
Table 1. Current Research trends in VLC for ITS applications.
Paper Title, Authors, and Year Intelligent transportation system using wireless optical communication: a comparative study (El-Garhy et al., 2024) [48] Channel performance analysis of visible light communication technology on the internet of vehicles (Liu et al., 2023) [49] Outdoor VLC in ITS: its impact on snow and rain (Zaki et al., 2019) [46]A visible light communications framework for intelligent transportation systems [50].
Research ObjectivesCompare the VLC systems and hybrid FSO/VLC systems in ITS. Analyze the impact of vehicle speed of VLC V2V and V2I scenarios.Analyze the impact of weather conditions on VLC for ITS applications.Develop a VLC framework for ITS to reduce congestion and improve navigation.
MethodsExperimental setup and simulations are used to measure the bit error rate (BER), signal-to-noise ratio (SNR), and coverage distance for both standalone VLC and hybrid FSO/VLC.Used the Green-Shields simulation model to relate vehicle speed, density, and traffic light heights.Theoretical analysis and simulations are conducted.Built a VLC traffic light system with transmitters and receivers and a new code division multiple access (CDMA) method to handle more users and tested its performance in simulations.
FindingsHybrid FSO/VLC provides a reliable communication link over a longer distance (900 m) with min BER and reliable SNR.Lower vehicle speeds improve VLC service quality in both V2I and V2V scenarios.Environmental factors can cause significant signal attenuation, which impacts on performance, such as data rate and SNR.Provide real-time traffic conditions and improve traffic management. The new CDMA scheme enhanced data rates in VLC.
StrengthsHybrid FSO/VLC in ITS for extended coverage and reliability.Provide insights into the relationship between vehicle motion and VLC service quality for speed-density relationships.Analyze crucial weather factors for VLC-based ITS applications.Design CDMA-VLC to improve data handling and reduce traffic congestion.
WeaknessesEnvironmental conditions are not addressed. The integration with existing ITS infrastructure and technologies is not discussed.Whether factors or relative motion between vehicles are not considered.
Limited theoretical analysis and validation. 		Limited to theoretical analysis and experimental validation.Weather, obstructions, and signal interference are not addressed and lacks discussion on integration with existing ITS technologies or infrastructure.
Table 2. Comparison of recent review papers on VLC.
Table 2. Comparison of recent review papers on VLC.
Authors and YearFocusKey FindingsAdvantagesChallengesNoveltyFuture Directions
Yu et al., 2021 [51]VLC system components and applications.VLC system performance, prospective applications in IoT, vehicle, and underwater networks.High data rate, energy-efficient, integration with IoT devices.Limited range, line of sight (LoS) requirement, environmental sensitivity.Detail review of VLC system components.Improve VLC performance and explore new applications in emerging fields.
Rehman et al., 2019 [9]System perspective of VLC technology.High-speed VLC, energy-efficiency, communication security and challenges.Secure communication, high data rates, and low energy consumption.Interference from ambient light, weather effects, and deployment cost.Evaluation of system-level challenges and benefits.Overcome environmental challenges and improve system robustness.
Yosef et al., 2024 [52]NOMA- VLC for vehicular communication.It enhances spectral efficiency, system capacity, and lower power consumption. NOMA-VLC provides an unoccupied spectrum, faster data rates, and minimal interference. LED nonlinearities, power allocation, and equitable distribution among users.Application of NOMA in VLC on V2V communication.Further research on power allocation, MIMO-NOMA, and LED nonlinearity mitigation.
Shaaban et al., 2021 [52]VLC technology in ITS, specifically for V2V and V2I.LDs outperform LEDs in terms of data rate, transmission distance, and efficiency due to their higher quantum efficiency.Low electromagnetic interference, high data security, high data rates, reduce energy consumption.Environmental factors, unwanted light. Low modulation bandwidth of LEDs.Focus on LD-based illumination in V2V and V2I communications.Further research to overcome challenges in outdoor environments. Investigate hybrid VLC–RF system. Expand applications in vehicle and underwater communications.
Geng et al., 2022 [53]Provides a comprehensive survey of VLC technologies and their applications.Advances in channel modeling, light modulation, physical layer, and security. Machine learning (ML) applied in various aspects of VLC systems.High data rate and unregulated spectrum, dual functionality, enhanced security.Flickering and dimming issues in light modulation. Interference and noise in the optical channel. Limited transmission distance.Integration of ML in VLC systems for performance enhancement.Further research to mitigate channel noise and interference. Improve modulation techniques to increase data rates and reduce flickering.
Nagarajan et al., 2023 [54]Evaluate the feasibility of a V2LC and interference. Examine V2LC’s performance.Reduced interference:
Less packet loss: multiple paths to vehicles help avoid collisions during data transmission.		Handles high bandwidth. Improving safety-critical and high-speed communication for UAVs.Existing challenges in traditional VLC systems.Utilizing intelligent reflecting surfaces (IRSs) in VLC systems, and intelligent mirror arrays (IMAs).Using UAVs with VLC capabilities as a solution to challenges of using RF-based UAVs for wireless networking.
Gupta et al., 2024 [55]Applications and challenges of VLC in various domains.VLC has applications in healthcare, aviation, indoor positioning, vehicular communication, etc.High data rates, increased security, low interference, and energy efficiency.Limited range, requirement of LoS link, ambient noise, and compatibility with existing systems.Review of global standards and diverse applications.Adopt challenges like interference mitigation, power consumption, and standardization for widespread adoption.
This review VLC in ITS communication systems.LED current overdriving and variable PPM are used to improve communication range for ITS applications.High data rates, energy efficiency, low latency, suitability for ITS applications.Environmental sensitivity, line-of-sight requirement, and interference.Emphasis on unique techniques like LED and variable pulse position modulation.Explore practical implementations and further improve VLC resilience to environmental factors. Integrate VLC with other communication technologies for robust ITS.
Table 3. Standard communication protocols relevant to ITS applications.
Table 3. Standard communication protocols relevant to ITS applications.
Communication ProtocolDescription
IEEE 802.15.7-2018VLC standard, suitable for ultra-low latency repaying and ITS applications.
IEEE 802.11pDSRC protocol for vehicular environments, often used as a supplement to 802.11
ITS-G5ETSI standard specifically designed for ITS communication systems.
IEE 802.15.4WPAN standard, relevant for IoT devices and sensor networks in ITS.
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Sikder, P.; Rahman, M.T.; Bakibillah, A.S.M. Advancements and Challenges of Visible Light Communication in Intelligent Transportation Systems: A Comprehensive Review. Photonics 2025, 12, 225. https://doi.org/10.3390/photonics12030225

AMA Style

Sikder P, Rahman MT, Bakibillah ASM. Advancements and Challenges of Visible Light Communication in Intelligent Transportation Systems: A Comprehensive Review. Photonics. 2025; 12(3):225. https://doi.org/10.3390/photonics12030225

Chicago/Turabian Style

Sikder, Prokash, M. T. Rahman, and A. S. M. Bakibillah. 2025. "Advancements and Challenges of Visible Light Communication in Intelligent Transportation Systems: A Comprehensive Review" Photonics 12, no. 3: 225. https://doi.org/10.3390/photonics12030225

APA Style

Sikder, P., Rahman, M. T., & Bakibillah, A. S. M. (2025). Advancements and Challenges of Visible Light Communication in Intelligent Transportation Systems: A Comprehensive Review. Photonics, 12(3), 225. https://doi.org/10.3390/photonics12030225

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