Smart phones, tablets, and the rise of the Internet of Things are driving an insatiable demand for wireless capacity. This demand requires networking and Internet infrastructures to evolve to meet the needs of current and future multimedia applications. Wireless HetNets will play an important role toward the goal of using a diverse spectrum to provide high quality-of-service, especially in indoor environments where most data are consumed. An additional tier in the wireless HetNets concept is envisioned using indoor gigabit small-cells to offer additional wireless capacity where it is needed the most. The use of light as a new mobile access medium is considered promising. In this article, we describe the general characteristics of WiFi and VLC (or LiFi) and demonstrate a practical framework for both technologies to coexist. We explore the existing research activity in this area and articulate current and future research challenges based on our experience in building a proof-of-concept prototype VLC HetNet.

Visible light communications (VLC) is an emerging field of optical communications that focuses on the part of the electromagnetic spectrum that humans can see. Much existing work in optical communications exists, mainly optimized for capacity and transmission performance in fiber and free-space with biases toward spectrum that minimizes attenuation in the medium. However, the use of the visible spectrum has gained interest due to its availability and the ease at which it can be modulated using light emitting diodes (LEDs). Recent demand factors due to the burgeoning mobile industry and the rapid evolution of LED-based lighting are also driving this interest. Here, and in this special issue, we outline the context of VLC, its unique benefits, and describe the state of the art research contributions of the assembled papers.

Advances in solid-state lighting (SSL) are enabling LEDs to be the dominant source for future human-made light. The adoption of LEDs is expected to significantly reduce energy consumption and facilitate precise intensity and color control of illuminated spaces. SSL also makes possible the use of visible light communications (VLC), in which data are emitted from luminaires through subtle intensity variations. This article focuses on the impact of lighting requirements on VLC systems, especially as found in indoor deployment scenarios. We also consider dimming control and its impact on color quality in the context of measured vs. perceived light levels.

Wireless network data consumption is experiencing drastic increases due to growing demands of mobile services and applications. Deployed networks using Radio Frequency (RF) communications are characterized by a shared medium, limited available spectrum and limited ability to scale with increasing demand. Directional communications, including Visible Light Communications (VLC), can limit contention in controlled environments and provide scalability through spatial reuse of the medium. This solution can provide massive aggregate data capacity in indoor scenarios if properly distributed. In this paper we propose an indoor hybrid system that integrates WiFi and VLC luminaries. Our system utilizes (i) broadcast VLC channels to supplement RF communications and (ii) a handover mechanism between WiFi and VLC to dynamically distribute resources and optimize system throughput. This approach offers the bandwidth density benefits of VLC, provides a non-intrusive RF back-channel, maintains compatibility with conventional RF devices, and demonstrates excellent scalability. Analytical and simulation results show improvements in aggregate performance (i.e., throughput and delay) of the hybrid, when compared to either system acting alone.

Interactive multimedia systems are rapidly evolving from marketing hype and research prototypes to commercial deployments.We survey the technological issues for designing a large-scale, distributed, interactive multimedia system.