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Modern communication systems have traditionally exploited three parts of the electromagnetic spectrum: radio waves region, infrared region and visible region, where the evolution in these ranges is always accompanied by the appropriation of new electromagnetic phenomena to build devices with better characteristics. In these three regions great advances have been conducted in recent years. For this reason, in this issue, we call for papers concerning to the major challenges that these technologies may face in the coming years.

In this paper, we introduce the Matrix‐MMC propagation model for indoor wireless optical channels. This proposed method is evolved from the modified Monte Carlo (MMC)–based ray tracing algorithm, but in addition to the properties of MMC, it has the capability of capturing reflection phenomena implying changes on wavelength (eg, fluorescence, phosphorescence, or iridescence) with a simplified analytical expression. The model provides unprecedented information about the mechanism of surface reflection in a visible light communication channel, which influences the propagation of the light waves, that depends on wavelength.

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Nowadays, with the incursion of solid state lighting technology in our daily life, visible light communication (VLC) systems are becoming more important. This fact has generated a lot of attention on VLC to provide solutions on multiple applications where this technology can be exploited. At the same time, the growing of automation processes has created the necessity of knowing the localization of different objects and devices. Indoor localization based on radio frequency signals is one of the most used techniques (Wi‐Fi, Bluetooth, UWB, RFID, etc); however, VLC is a new and interesting method, which is gaining enormous research attention. Moreover, there are environments where the use of RF technologies is restricted or even prohibited. In such cases, VLC technology becomes an interesting alternative to solve this problem. In this paper, we design and implement a novel VLC‐based indoor localization system that combines the application of a VLC scheme for downlink and an ultrasonic communication for the uplink. Practical localization experiments are carried out in an actual office room environment, and results show a localization accuracy of 4 cm on average for direct links and 10 cm for indirect links.