In the context of an increasing interest toward reducing the number of traffic accidents and of associated victims, communication-based vehicle safety applications have emerged as one of the best solutions to enhance road safety. In this area, visible light communications (VLC) have a great potential for applications due to their relatively simple design for basic functioning, efficiency, and large geographical distribution. This paper addresses the issues related to the VLC usage in vehicular communication applications, being the first extensive survey dedicated to this topic. Although VLC has been the focus of an intensive research during the last few years, the technology is still in its infancy and requires continuous efforts to overcome the current challenges, especially in outdoor applications, such as the automotive communications. This paper is aimed at providing an overview of several research directions that could transform VLC into a reliable component of the transportation infrastructure. The main challenges are identified and the status of the accomplishments in each direction is presented, helping one to understand what has been done, where the technology stands and what is still missing. The challenges for VLC usage in vehicle applications addressed by this survey are: 1) increasing the robustness to noise; 2) increasing the communication range; 3) enhancing mobility; 4) performing distance measurements and visible light positioning; 5) increasing data rate; 6) developing parallel VLC; and 7) developing heterogeneous dedicated short range communications and VLC networks. Addressing and solving these challenges lead to the perspective of fully demonstrating the high potential of VLC, and therefore, to enable the VLC usage in road safety applications. This paper also proposes several future research directions for the automotive VLC applications and offers a brief review on the associated standardization activities.

Current Challenges for Visible Light Communications Usage in Vehicle Applications: A Survey

The field of visible light communications (VLC) has gained significant interest over the last decade, in both fibre and free-space embodiments. In fibre systems, the availability of low cost plastic optical fibre (POF) that is compatible with visible data communications has been a key enabler. In free-space applications, the availability of hundreds of THz of the unregulated spectrum makes VLC attractive for wireless communications. This paper provides an overview of the recent developments in VLC systems based on gallium nitride (GaN) light-emitting diodes (LEDs), covering aspects from sources to systems. The state-of-the-art technology enabling bandwidth of GaN LEDs in the range of >400 MHz is explored. Furthermore, advances in key technologies, including advanced modulation, equalisation, and multiplexing that have enabled free-space VLC data rates beyond 10 Gb/s are also outlined.

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A review of gallium nitride LEDs for multi-gigabit-per-second visible light data communications

The fifth generation (5G) mobile networks are envisaged to enable a plethora of breakthrough advancements in wireless technologies, providing support of a diverse set of services over a single platform. While the deployment of 5G systems is scaling up globally, it is time to look ahead for beyond 5G systems. This is mainly driven by the emerging societal trends, calling for fully automated systems and intelligent services supported by extended reality and haptics communications. To accommodate the stringent requirements of their prospective applications, which are data-driven and defined by extremely low-latency, ultra-reliable, fast and seamless wireless connectivity, research initiatives are currently focusing on a progressive roadmap towards the sixth generation (6G) networks, which are expected to bring transformative changes to this premise. In this article, we shed light on some of the major enabling technologies for 6G, which are expected to revolutionize the fundamental architectures of cellular networks and provide multiple homogeneous artificial intelligence-empowered services, including distributed communications, control, computing, sensing, and energy, from its core to its end nodes. In particular, the present paper aims to answer several 6G framework related questions: What are the driving forces for the development of 6G? How will the enabling technologies of 6G differ from those in 5G? What kind of applications and interactions will they support which would not be supported by 5G? We address these questions by presenting a comprehensive study of the 6G vision and outlining seven of its disruptive technologies, i.e., mmWave communications, terahertz communications, optical wireless communications, programmable metasurfaces, drone-based communications, backscatter communications and tactile internet, as well as their potential applications. Then, by leveraging the state-of-the-art literature surveyed for each technology, we discuss the associated requirements, key challenges, and open research problems. These discussions are thereafter used to open up the horizon for future research directions.

A Prospective Look: Key Enabling Technologies, Applications and Open Research Topics in 6G Networks

Indoor wireless traffic is evolving at a staggering pace, and is quickly depleting radio spectrum resources. Optical wireless communication (OWC) offers powerful solutions for resolving this imminent capacity crunch of radio-based wireless networks. OWC is not intended to fully replace radio wireless techniques such as WiFi, but to complement these and offload their high traffic loads. After discussing OWC's application domains, this paper gives a tutorial overview of two major directions in OWC: wide-coverage visible light communication which builds on LED illumination techniques and shares capacity among multiple devices, and communication with narrow 2-D steered infrared beams which offers unshared high capacity to devices individually. In addition, supporting techniques for wide field-of-view receivers, device localization, bidirectional hybrid optical/radio networks, and bidirectional all-optical wireless networks are discussed.

Indoor Optical Wireless Systems: Technology, Trends, and Applications

Optical wireless communication (OWC) is an excellent complementary solution to its radio frequency (RF) counterpart. OWC technologies have been demonstrated to be able to support high traffic generated by massive connectivity of the Internet of Things (IoT) and upcoming 5th generation (5G) wireless communication systems. As the characteristics of OWC and RF are complementary, a combined application is regarded as a promising approach to support 5G and beyond communication systems. Hybrid RF/optical and optical/optical wireless systems offer an excellent solution for recovering the limitations of individual systems as well as for providing positive features of each of the technologies. An RF/optical wireless hybrid system consists both RF and optical-based wireless technologies, whereas an optical/optical wireless hybrid system consists two or more types of OWC technologies. The co-deployment of wireless systems can improve system performance in terms of throughput, reliability, and energy efficiency of individual networks. This study surveys the state of the art and key research directions regarding optical wireless hybrid networks, being the first extensive survey dedicated to this topic. We provide a technology overview of existing literature on optical wireless hybrid networks, such as RF/optical and optical/optical systems. We consider the RF-based macrocell, small cell, wireless fidelity, and Bluetooth, as well as optical-based visible light communication, light fidelity, optical camera communication, and free-space optical communication technologies for different combinations of hybrid systems. Moreover, we consider underwater acoustic communication for hybrid acoustic/optical systems. The opportunities brought by hybrid systems are presented in detail. We outline important challenges that need to be addressed for successful deployment of optical wireless hybrid network systems for 5G and IoT paradigms.

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Optical Wireless Hybrid Networks: Trends, Opportunities, Challenges, and Research Directions

Wireless technologies based on radio frequencies (RFs) have always dominated other types of wireless technologies up until now. However, the recent proliferation of media-rich smart devices has pushed the RF spectrum usage to its limit. Therefore RF band expansion towards the optical spectrum is imminent in commercial scale. Indeed, the research on wireless communications using the optical spectrum has gained tremendous ground during the past couple of decades and standardised, respectively, by infrared data association for infrared communication and IEEE 802.15.7 for visible light communication. However, only few shortcomings of the IEEE 802.15.7 standard have led to the development of a revised version, called IEEE 802.15.7r1. This article provides an insight on the activity of the proposed revision of IEEE 802.15.7r1. The proposed revision version targets communication systems that mainly use either image sensors or cameras, known as the optical camera communications (OCC). Leveraging the existing infrastructure, OCC systems will be able to provide ubiquitous coverage in both indoors and outdoors. The authors present their survey focusing on the key technology consideration in IEEE 802.15.7r1, current research status, impairments, enhancements and futuristic application scenarios of the OCC systems.

https://ietresearch.onlinelibrary.wiley.com/doi/epdf/10.1049/iet-opt.2014.0151

Survey on optical camera communications: challenges and opportunities

Stereo-vision-based cooperative-vehicle positioning using OCC and neural networks

Indoor positioning technique is one of the key research issues due to highly demandable market value to provide Location Based Services (LBS) using smart phone. In optical camera communication (OCC) case one of the main advantages in indoor navigation system is LED itself can transmit location information along with unique feature of a camera to detect location using photogrammetry. However due to nonlinear and highly complicated relationship between 3D scenery and pictured 2D image need to develop complex mathematical model to estimate position of camera using photogrammetry. Neural network can be used to learn this complicated relationship without developing any complex mathematical model. We have used feed forward neural network to estimate camera position using coordinate information transmitted by LED.

Neural network based indoor positioning technique in optical camera communication system

Visible light communication (VLC) using light emitting diodes (LEDs) has become a benchmark for high speed data communications, especially in indoor applications. In order to achieve high data rate for VLC system, multiple input multiple output (MIMO) is a feasible option. However, contemporary MIMO-VLC system lacks from diversity and experiences performance variation through different optical channels. In order to achieve receiver diversity and mitigate performance variation, we propose maximal ratio combining (MRC) method to improve VLC receiver performance. Simulation results demonstrate performance improvement in terms of received power and bit error rate.

Receiver performance improvement utilizing diversity in MIMO VLC

As visible light communication (VLC) system continues to promising solution of spectrum shortage, resource allocation is becoming a concern in IEEE 802.15.7 wireless personal area network (WPAN) research. Due to the improper utilization of non-overlapping channels such networks suffer from the co-channel interference and hence system performance is degraded. In this paper, we propose a resource allocation scheme that selects non-overlapping channels having best signal-to-interference plus noise-ratio (SINR) and acting indirectly on the interference levels. Our proposed scheme assigns the visible light multicolor logical channels such that the co-channel interference is minimized. The numerical analysis shows that the interference aware channel assignment scheme can effectively reduce the dropping probability and increase the utilization of large visible light bandwidth.

Nirzhar Saha

Papers

Survey on optical camera communications: challenges and opportunities

Stereo-vision-based cooperative-vehicle positioning using OCC and neural networks

Neural network based indoor positioning technique in optical camera communication system

Receiver performance improvement utilizing diversity in MIMO VLC

Interference-aware optical resource allocation in visible light communication