Industrial IoT by Unknown

Author:Unknown
Language: eng
Format: epub
ISBN: 9783030425005
Publisher: Springer International Publishing

3.4.3.4 Li-Fi

Li-Fi is an optical communication technology that utilizes light to transmit information between devices, including visible light, ultraviolet light, or infrared signals; LED sources are employed to generate the information-carrying beam. It is an example of a VLC. The spectrum utilized by Li-Fi channels can be significantly larger than the radio frequency spectrum used by Wi-Fi systems, resulting in high throughput where data rates in the multiple Gbps can be achieved in some systems. Li-Fi transmission is impervious to traditional electromagnetic interference thus it can also be used in specific environments such as hospitals. The light switching occurs at a very high speed thus it cannot be noticed by the human eye; also, the light can be dimmed to below human visibility while still emitting enough light to convey information. Li-Fi enjoys smaller round-trip latency than Wi-Fi. A Li-Fi Access Point (AP) can be used for WLAN-like applications to user’s workstations and laptops. Additionally, sensors (whether in the fixture or in the floor environment) can use VLC to communicate information to the lighting control system. The light waves cannot penetrate walls thus the technology is limited to a short range, although full direct line of sight is not necessary since the light is typically reflected off the walls. Applications include, among others, home and building automation, hospital medical systems, vehicles, and industrial automation. While the IEEE 802.15.7 standard does not per se consider the use of optical orthogonal frequency-division multiplexing (O-OFDM) modulation methods, the standard defines the PHY and the MAC layer. The standard defines three PHY layers:The PHY 1 is designed for outdoor environments and supports data rates up to 267 kbps using on-off keying Manchester coding and variable pulse position modulation (VPPM);

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