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light fidelity (LiFi)

Light Fidelity (LiFi) is a concept that uses modulated visible light to transmit data over short distances. This concept is also known as Visible Light Communication

(VLC). However, the term LiFi for Light Fidelity is likely to prevail. LiFi technology transmits data in the visible wavelength range between 375 nm and 750 nm.or in the near-infrared range

between 750 nm and 1500 nm.Light is emitted using VCSEL lasers or high-power LEDs from ceiling lights or wall lights as transmitting devices and photodiodes as receiving devices that demodulate the received light. Transmitting devices and receiving devices in a line of sight

are stationary. However, the light signals can be reflected from ceilings and walls and received by the receiving devices without a line of sight.Transmission through walls or fixtures is not possible


With good alignment of the light transmission, high data rates can be transmitted with LiFi. These are dependent on the signal source. Data rates of 5 Gbit/s can be achieved with light emitting diodes, 10 Gbit/s with micro LEDs and 100 Gbit/s with laser diodes

. Standardized data rates are between 1 Gbit/s and 6 Gbit/s.

Block diagram of a LiFi transmission

Block diagram of a LiFi transmission

LiFi can also be used where radio signals could cause problems due to electromagnetic compatibility. The concept supports point-to-point (P2P), point-to-multipoint

(P2MP), and multipoint-to-multipoint connections. Inresearch facilities, LiFi has been used to achieve data transmission rates of well over one hundred gigabits per second. In practice, data rates of up to 1 Gbit/s are achieved, limited by the opto-electronic components used for light modulation

and demodulation. LiFi is addressed by several standardization bodies.

For example, by IEEE 802.15.7, by the ITU-T in Recommendation G.VLC, and by the IEEE project groups 802.15.13 and 802.11BB.

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Englisch: light fidelity - LiFi
Updated at: 11.12.2020
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