Visible Light Communication (VLC) is an emerging field in Optical Wireless Communication (OWC) which utilizes the superior modulation bandwidth of Light Emitting Diodes (LEDs) to transmit data. In modern day communication systems, the most popular frequency band is Radio Frequency (RF) mainly due to little interference and good coverage. However, the rapidly dwindling RF spectrum along with increasing wireless network traffic has substantiated the need for greater bandwidth and spectral relief. By combining illumination and communication, VLC provides ubiquitous communication while addressing the shortfalls and limitations of RF communication. This paper provides a comprehensive survey on VLC with an emphasis on challenges faced in indoor applications over the period 1979-2014. VLC is compared with infrared (IR) and RF systems and the necessity for using this beneficial technology in communication systems is justified. The advantages of LEDs compared to traditional lighting technologies are discussed and comparison is done between different types of LEDs currently available. Modulation schemes and dimming techniques for indoor VLC are discussed in detail. Methods needed to improve VLC system performance such as filtering, equalization, compensation, and beamforming are also presented. The recent progress made by various research groups in this field is discussed along with the possible applications of this technology. Finally, the limitations of VLC as well as the probable future directions are presented.

VLC is an emerging optical wireless communication technology that can be added as a complementary feature into existing lighting infrastructures for alleviating pressure on the rapidly dwindling radio frequency spectrum. Although LEDs have been traditionally used as transmitters in VLC, the growing urgency for higher data rates in the gigabit class range has deviated focus toward the consideration of LDs as potential sources for VLC due to their unique features of high modulation bandwidth, efficiency, and beam convergence. This article focuses on the principles of LD-based VLC systems, highlighting the operational characteristics and link configurations. The unique features of LDs compared to LEDs are discussed alongside the communication and illumination aspects of different classifications of LD-VLC. The challenges in terms of practical implementation and the potential applications that might arise from this communication technology are also discussed.

As a new generation green lighting source, the light emitting diode (LED) is rapidly replacing traditional incandescent and fluorescent light sources. Apart from providing energy savings, the use of LED lighting technology creates scope for an innovative optical wireless communication technology known as visible light communication (VLC), which takes advantage of the superior modulation capability of LEDs to transmit data through a wireless channel. VLC is capable of concurrently providing communication as well as illumination. For making commercial implementation of VLC feasible, it is necessary to incorporate it with dimming schemes that will provide energy savings, moods, and increase the aesthetic value of the place using this technology. However, general dimming techniques have an adverse effect on communication since they limit the achievable data rate of a VLC link. This drives the necessity of formulating efficient dimming techniques, which will create a balance between the two most basic functions of VLC: illumination and communication. This paper focuses on dimming mechanisms that can be implemented in VLC systems to save energy and provide precise illumination control. The motivation behind this control mechanism, current challenges in practical implementation, driver circuitry, recent progress, and future prospects are also concisely presented.

Missing data in Intelligent Transportation Systems (ITS) could lead to possible errors in the analyses of traffic data. Applying Artificial Intelligence (AI) in these circumstances can mitigate such problems. Past works focused only on specific data imputation methods, such as tensor factorization or a specific neural network model. While there are review papers covering singular topics regarding missing data, there are none in the field of traffic, to the best of our knowledge, that introduces the process of missing data collection and the viability of the traffic data collected while also broadly covering the popularly used models of recent years. This has led to non-uniformity of the terms used in missing data imputation, limited research in areas where datasets are not available, and a narrowed view of the methods used for data imputation. Hence, this paper aims to standardize the terms used in missing data classifications, look into the limitations of using available public or private datasets for urban traffic research, and discuss popular statistical and data-driven methods used by recent AI and ITS papers. It was found that tensor decomposition-based methods are the most popular for missing data imputation, followed by Generative Adversarial Networks and Graph Neural Networks, all of which rely on a large training dataset. Meanwhile, Probability Principle Component Analysis (PPCA) methods provide valuable insights via traffic analysis and are used for real-time traffic imputation. This paper also highlights the need for more efficient and reliable methods for traffic data collection, such as online APIs.

The year-by-year increase in electricity consumption significantly affects all nations today from environmental, social, and economic perspectives. Various studies show that, among the contributors of this increase, power consumption of the equipment forming the Internet infrastructure is significant. Consequently, considerable attention is given to finding solutions to reduce power consumption of the systems that run the Internet. Current literature suggests that the optical backbone network is responsible for the majority of the consumed power, particularly at high traffic loads. This highlights the importance of formulating solutions to reduce power consumption in backbone networks. In this paper, we provide a comprehensive survey of the most relevant research efforts on minimizing power consumption of backbone networks. We categorize our review into four broad approaches: network redesign, traffic engineering, power-aware networking, and load-adaptive operation. We highlight the findings of relevant studies and provide an analysis of their limitations. We also evaluate the technological differences of similar work and identify a number of future directions. Finally, we demonstrate that the adoption of these technologies is gathering pace among prominent research bodies, device manufacturers, and network operators.