[LINK] Light based wireless networks

[Stephen Loosley]

Light based wireless networks: LiFi spec OK'd as Wi-Fi complement


By Thomas Claburn Fri 14 Jul 2023


IEEE 802.11bb, an amendment to the Wi-Fi specification that supports 
wireless networking using visible and infrared light instead of the 
radio spectrum, was approved last month by the electrical engineering body.

The IEEE 802.11bb Light Communication Global standard, referred to as 
LiFi, describes the necessary changes to physical layers (PHY) and the 
medium access control layer (MAC) to allow 802.11 wireless networking 
via light source modulation that, mercifully, people can't see.

The LiFi spec calls for bidirectional transmission in the 800nm to 
1,000nm band of the electromagnetic spectrum, with a minimum throughput 
of 10 Mb/s and a maximum of 9.6 Gb/s at the MAC data service access point.

As a point of comparison, Wi-Fi operates over wavelengths of 120mm (2.4 
GHz) and 60mm (5 GHz), with transmission speeds that depend on the 
version. Wi-Fi 6 (like LiFi) tops out at 9.6 Gb/s.

On Thursday this week, pureLiFi, based in Scotland, UK, and Fraunhofer 
HHI, based in Germany, celebrated the LiFi spec's approval, saying the 
new standard sets the stage for LiFi systems to interoperate with Wi-Fi 
networks.

"The IEEE 802.11bb standard is a critical step to enable 
interoperability between multiple vendors," said Volker Jungnickel from 
Fraunhofer HHI, who served as technical editor of the task group, in a 
statement. "It allows for the first time LiFi solutions inside the Wi-Fi 
ecosystem."

According to Jungnickel, interoperability with Wi-Fi is necessary to 
support the development of novel LiFi applications.

Initially, LiFi is being positioned as a complement to Wi-Fi systems, an 
option that provides a way to add extra bandwidth without increasing 
network congestion or interference. The shiny new technology also has 
potential as a way to thin cable thickets.

"LiFi can replace cables by short-range optical wireless links and 
connect numerous sensors and actuators to the Internet," said 
Jungnickel. "We believe that this will create a future mass market."

Network backhaul is preferably power-over-Ethernet (POE) for new 
installations or power line communications (PLC) for retrofits.

With a LiFi attachment such as the pureLiFi's Light Antenna ONE plugged 
into a laptop, the computer should be able to send and receive data at a 
rate of more than 1 Gb/s.

Since LiFi access points have a limited field of view, it's possible to 
set up environments where pools of LED light provide network access only 
to those within them.

Some of pureLiFi's systems work without visible light, via infrared 
transmission. Other components require some level of illumination for 
transmission. These work at low light levels – about 10 percent of 
maximum. That translates to 60 lux, where 400 lux represents the UK 
minimum standard for reading, according to the company.

One of the rationales for LiFi is security. According to pureLiFi, the 
technology is "inherently secure" – walls serve as firewalls since light 
does not pass through them – and is already being used at military 
facilities.

"Light's line-of-sight propagation enhances security by preventing wall 
penetration, reducing jamming and eavesdropping risks, and enabling 
centimeter-precision indoor navigation," said Dominic Schulz, lead of 
LiFi development at Fraunhofer HHI, in a statement.

pureLiFi suggests that being able to see into a room with active LiFi 
via a telescopic lens would not provide a data interception opportunity. 
The biz claims such lenses have a narrow field of view and could only 
see an uplink or downlink light source, not both.

"Even with a telescope, any signal detected would typically be too low 
in energy for successful decoding/demodulation," the company insists, as 
if daring security researchers to prove otherwise. ®

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