Abstract

As we approach the era of sixth-generation (6G) wireless networks, the trajectory of wireless communication is undergoing a significant transformation. Beyond its traditional role in data transmission, 6G networks are expected to integrate advanced sensing and localization capabilities, marking a shift toward networks that actively interact with their environment. This evolution is driven by the growing demands of the Internet of Things (IoT) era, where networks require not only high-speed communication but also real-time environmental awareness. In this context, Optical Wireless Communication (OWC) emerges as a key technology. OWC, leveraging LEDs and lasers, offers advantages such as low interference, narrow beamwidth, and high accuracy in localization, making it ideal for applications like indoor navigation, robotic operations, and augmented reality. Furthermore, hybrid networks combining OWC and Radio Frequency (RF) technologies hold the potential to revolutionize sectors like transportation, healthcare, and industrial automation by offering real-time communication and sensing. Fiber optics also play a pivotal role in Joint Communication and Sensing (JCS), supporting both data transmission and environmental sensing. This paper explores the integration of OWC, RF, and fiber technologies, highlighting the challenges of line-of-sight requirements, ambient light interference, and the need for seamless integration with existing wireless systems. Additionally, it discusses the promising future of hybrid networks, including advancements in 3D positioning, predictive resource management, and the application of artificial intelligence to enhance sensing and localization accuracy. By examining the potential and obstacles of combining optical and RF technologies, this paper provides a comprehensive view of the future of wireless networks, which will transform into adaptive, environment-aware systems capable of delivering both communication and sensing functions with high efficiency and precision.

Keywords: Optical Wireless Communication (OWC), Radio Frequency (RF), Joint Communication and Sensing (JCS), Hybrid Networks, 6G Networks, Fiber Optic, Sensing, Localization, Smart Cities, Real-time Communication

Introduction

The current trajectory of wireless communication technology is leading us to the next milestone, the sixth generation, or 6G, of networks. Historically, wireless networks have been at the forefront of delivering robust mobile broadband and ever increasing data rates. However, we are witnessing a transformative phase in the evolution of these networks, a phase that expands the traditional focus from pure data transmission to a multifaceted approach that includes sensing and localization capabilities [1]. These functions, previously on the fringes of network design and capability, are now taking center stage. The IoT era requires networks that not only transmit data, but also have a high level of awareness of their operating environment.

Such integration aims to transform passive networks into active systems capable of interacting with and adapting to their environment in real time. It should be noted that this integration has already influenced standardization activities, including IEEE 802.11 [2]. In this context, OWC is expected to play an important role in these advanced functionalities of future communication networks. In particular, the integration of optical wireless (OW) and RF technology in hybrid networks offers a promising solution to the challenges of current and future communication needs [3].

OWC uses LEDs and lasers to transmit data and can offer benefits such as reduced interference and low latency, which are critical for real-time processing and rapid data transfer. A defining characteristic of this technology is its narrow beamwidth, which can significantly improve angle-of-arrival measurements, making it ideal for applications that require pinpoint accuracy in localization efforts, such as indoor navigation systems, advanced robotic operations and augmented reality scenarios. The potential applications for OWC are thus diverse and hold great promise for several sectors. In transportation, for example, it could revolutionize the way vehicles communicate with each other and with infrastructure, improving traffic flow and safety. In industrial environments, it could enable more accurate asset tracking, better process monitoring, and predictive maintenance through real-time sensing. In healthcare, the use of this technology could lead to improved patient monitoring systems, smarter management of medical devices, and improved delivery of care services.

The convergence of OW and RF systems could further enhance these applications by leveraging the strengths of each technology. RF technology, with its proven long-range and obstacle penetration capabilities, complements the high speed and precision of OWC. By taking advantage of both optical and RF technologies, hybrid networks can provide robust, reliable and highly accurate wireless communication solutions. As wireless technologies have evolved, fiber has emerged as a powerful medium for joint communication and sensing (JCS), providing a complementary solution to hybrid OW and RF systems. Fiber optic technology is known for its unparalleled ability to transmit data over long distances with high bandwidth and minimal signal degradation. Beyond communications, these fibers can serve as distributed sensors capable of detecting temperature changes, pressure fluctuations and acoustic vibrations along their length. In the context of JCS, research efforts can be grouped into two primary themes. The first theme revolves around the development of networks that can simultaneously support communication and sensing functions, enabling a single piece of infrastructure to handle multiple tasks, which can lead to cost savings and increased efficiency. The second theme focuses on environmentally aware communications, where networks use their sensing capabilities to enhance their performance.

By actively responding to environmental changes, these networks can maintain consistent quality of service even in the face of disturbances or obstacles, making them self-optimizing and resilient. This contribution aims to provide a thorough examination of how the integration of OW technology with RF systems can enhance the sensing and localization capabilities inherent in wireless networks. We will discuss the research frontiers in the areas of simultaneous communication and sensing, as well as environment-aware communications, shedding light on the future possibilities of hybrid OW and RF technology. This integration is expected to reshape the landscape of wireless networks, transforming them from passive data channels to active entities aware of the ever-growing ecosystem.

State of the art

A fundamental aspect of current advances is addressing the inherent compatibility and potential conflicts between communication and sensing functions. Both domains, RF and OWC, share a confluence of advantages such as bandwidth reuse and the synergistic use of MIMO technologies. These shared advantages lay the groundwork for the development of systems that leverage both communication and sensing capabilities, albeit with inherent challenges related to waveform trade-offs and sensor performance metrics.

The use of OWC, particularly through VLC and IR techniques, has led to advances in 3D sensing and localization, as shown in Fig. 1. Innovations such as spatial modulation (SM) for improved 3D indoor positioning exemplify the progress made in achieving high spectral efficiency and interference-free transmission [4]. However, these advances are not without challenges, particularly the line-of-sight (LoS) requirement and susceptibility to ambient light interference. It should also be noted that the role of SM in JCS, particularly within the framework of OW, emerges as a key innovation in the proposed 3D indoor visible light positioning algorithm [5]. The confluence of OWC and RF technologies in hybrid networks has ushered in sophisticated strategies for proactive resource allocation.

By leveraging accurate knowledge of user locations, these networks can optimize resource allocation to improve both user experience and network efficiency [6]. This paradigm shift toward predictive resource management highlights the need for innovative solutions that accurately predict user mobility and seamlessly integrate disparate technologies. In parallel with developments in OWC, fiber optic technologies have emerged as a formidable medium for both long-distance communication and sensing. The application of AI and ML methodologies has significantly enhanced the capabilities of fiber optic sensors, facilitating the detection of minute environmental changes with unprecedented precision [7]. This dual functionality extends the utility of fiber optics beyond telecommunications, paving the way for its application in environmental monitoring, infrastructure security, and beyond. OWC technologies, particularly VLC and optical sensing, play a key role in advancing traffic control systems and facilitating the integration of autonomous vehicles, as shown in Fig. 2. The dual use of LED based lighting for illumination and data transmission offers a promising avenue for improving vehicular communication, navigation, 17 and overall traffic efficiency [8]. Despite the potential, challenges related to LoS requirements, optical interference, and integration with existing communication networks remain to be addressed.

Challenges and promising works

The integration of OWC and fiber technologies into future 6G wireless networks, while promising, presents a number of challenges that require concerted research and development efforts. Overcoming these challenges is critical to realizing the full potential of these technologies to enhance communication, sensing and localization capabilities in various sectors, including IoT, smart cities, healthcare and intelligent transportation systems.

• Addressing the LoS requirement: A significant challenge in deploying OWC systems, particularly VLC, is the inherent LoS requirement between Txs and Rxs. This limitation limits the effectiveness of the system in environments with potential obstacles or non-direct paths, such as indoor spaces with complex layouts or urban environments with numerous obstacles. Future work should focus on innovative solutions to mitigate LoS limitations, including the development of advanced reflective materials, relay systems, and beam steering techniques to improve signal range and reliability.

• Overcoming ambient light interference: The performance of OWC systems, especially in outdoor or well-lit indoor environments, can be severely degraded by ambient light sources. This interference can degrade the SNR, which affects the reliability and efficiency of data transmission. Research into advanced modulation schemes, filtering techniques and adaptive algorithms capable of dynamically compensating for ambient light variations is essential to mitigate these effects.

• Integration with existing wireless technologies: Seamless integration of OWC and optical fiber technologies with existing RF-based communication systems is a significant challenge. This integration is critical to ensuring interoperability and maximizing the coverage, reliability and efficiency of nextgeneration wireless networks. Future work must address the development of hybrid network architectures, standardized communication protocols, and cross-layer optimization strategies to ensure smooth coexistence with existing technologies.

• Scalability and cost-effectiveness: As the applications of OWC and optical fiber technologies expand, ensuring the scalability and cost effectiveness of these systems becomes imperative. Research should aim to develop cost-effective manufacturing processes for OWC and fiber optic components, as well as scalable network deployment strategies that can meet growing demands without exponential cost increases. This includes the exploration of novel materials, energy efficient devices and automated deployment methods.

• Improving sensing and localization accuracy: While OWC and optical fiber technologies offer significant potential for improving sensing and localization capabilities, achieving high levels of accuracy and reliability in diverse environments remains a challenge. Future research should focus on advanced algorithms and signal processing techniques that leverage AI and ML to improve the accuracy and robustness of sensing and localization functions under varying environmental conditions and in the presence of obstacles.

• Security and privacy concerns: The use of OWC and optical fiber technologies for communication and sensing raises pertinent security and privacy concerns. The broadcast nature of optical signals and the potential sensitivity of sensed data require robust security protocols and encryption techniques to protect against unauthorized access and data breaches. Future work must address these concerns by developing secure communication frameworks and appropriate algorithms tailored to the unique characteristics of OWC and fiber optic systems.

Conclusion

This paper explored the potential of Optical Wireless Communication (OWC) and its integration with Radio Frequency (RF) technology for Joint Communication and Sensing (JCS) in future wireless networks. As 6G networks evolve, the convergence of communication and sensing is becoming increasingly important, with OWC providing unique advantages such as high data rates, low interference, and precise localization capabilities. By combining OWC with RF systems, hybrid networks can leverage the strengths of both technologies to enhance performance in various applications, including smart cities, transportation, healthcare, and industrial automation. We also examined the role of fiber optic technology in JCS, emphasizing its ability to support both long-distance data transmission and environmental sensing. The challenges associated with these technologies, including line-of-sight requirements, ambient light interference, and the need for seamless integration with existing RF-based systems, were discussed. Addressing these challenges will be crucial to fully realizing the potential of OWC and RF in joint communication and sensing. In conclusion, the integration of optical and RF technologies represents a promising path forward for 6G networks, transforming them from passive data carriers into intelligent, adaptive systems capable of real-time communication and environmental awareness. This advancement will not only improve network efficiency but also open new possibilities for innovative applications across multiple sectors. Future research should focus on overcoming existing technical challenges and further optimizing hybrid OWC-RF systems for a seamless, high-performance wireless experience.

Acknowledgement

The authors would like to thank all the members of the Newfocus Special Interest Group on Joint Communication & Sensing and, specifically, Milica Petkovic, Anna Maria Vegni, A´ lvaro Herna´ndez, Manuela Vieira, Manuel A. Veira, Nobby Stevens, Venceslav Kafedziski, Alexis Dowhuszko and George K. Karagiannidis for proofreading sharing their view on this contribution.