No, it isn’t a typo for WiFi missed by the Editor...it really is LiFi, and it stands for Light Fidelity.
A while back, I wrote a piece about cutting-edge work taking place in the modulation of LED light bulbs for communications purposes. Since that time, LEDs have become even more capable, and you have probably noticed that they have come down in cost.
LEDs of certain wavelengths have been used in fiber optic communication, but these use a dedicated glass or plastic waveguide. Free-space lasers have been used for certain point-to-point communications; but is using a light bulb for network communications really feasible and likely to find a place in our future?
Let’s go back to fiber optics for communications. In security, its key properties are total noise immunity, high bandwidth over extended distances, optical isolation, and additional system topology options, such as star-configured RS-485 networks. Can a light bulb compare?
LiFi employs visible light emitted by LED bulbs to communicate. It was invented by Harald Haas of the University of Edinburgh, Scotland, back in 2011, when he demonstrated for the first time that pulsing the light from a single LED bulb would allow more transmitted data than that sent from a cellular tower. Take a look his brief Ted talk at www.ted.com/talks/harald_haas_wireless_data_from_every_light_bulb.
Editor’s Note: SD&I first introduced readers to LiFi back in Sept. 2015. Check out that article for more insights at www.securityinfowatch.com/12103850.
LiFi in Action
Optical communication uses light modulation to send data. LiFi modulation is too fast for us to notice or be annoyed by. While bulbs need to stay energized, they can be dimmed to be unnoticeable while still putting out enough energy to be detected by a compatible receiver.
As an example of how this might work, a company called VLNComm has announced a standing lamp product that can be directly connected to a LAN. In this case, a power line adapter is used to allow Ethernet signals to be carried over power wiring, with necessary electronics in the light bulb to perform the necessary E/O signal conversion. Communication with the LED bulb from end-devices is via a receiver connected to a USB port.
This approach will be limited in terms of number of users, and bandwidth will likely be limited by the capability of the power line converter, but this may still be sufficient for home or small office use. The company promises lighting panels with direct LAN connections for larger environments with multiple users. Last March, VLNComm received a $1 million grant under DOE’s SBIR program to assist in the commercialization of their technology.
puriLiFi Ltd., the company begun by LiFi founder Haas, offers the LiFi-X system with the stated advantages of multiple access, roaming, complete mobility and ease of use. End-devices also rely on a USB transceiver, which works with LiFi-X access points to provide rollover as the device moves around. Access points support both PoE and power line communications.
This “light infrastructure” is based on a concept called an “atto-cell” – admittedly a new term for me. Think of it as the area illuminated by a cone of light, and any devices in that area capable of receiving enough direct or reflected light to be sensed by its optical receiver. A published article by Haas for SPIE pegged the coverage of an atto-cell at 1-10 square meters at a distance of 3 meters. So, imagine a miniature cellular-like network where the LED bulb or panel is the gateway to the network.
Target Applications
IEEE 802.15 is a working group for Wireless Specialty Networks. Optical Wireless Communication (OWC) technology is now being addressed within the IEEE 802.15.7r1 (revision 1) OWC Task Group (TG), which has defined the term LiFi.
They have identified target applications to include indoor office/home applications, conference rooms, general offices, shopping centers, airports, railways, hospitals, museums, aircraft cabins, and libraries. The group is requiring such elements as dimming control, coexistence with other light fixtures, multiple transmitters (MIMO), 1-30 ms latency, and certain data rate thresholds. Thus, at the end of the day, there will be a robust standard in place, allowing orderly product development and interoperability.
Besides being interesting from a pure technology standpoint, many advantages are promised:
- LED light bulbs have high intensities and can achieve very large data rates, but are not known to cause eye damage;
- Immunity from electrical noise and radio-frequency interference;
- No reliance or impingement on the RF portion of the spectrum;
- 400-800 THz frequency range of visible light, enabling unlimited modulation possibilities;
- Combined lighting controls and communications – energy and space efficient;
- Potential high density of access points with many bulbs in a lighting array, enabling the servicing of many users;
- Data security in enclosed areas;
- Potential use in asset or people tracking in an indoor environment by measuring the trip times of transmitted and received pulses from individual bulbs and then triangulating position; and
- Reported speeds of 3.5 Gbps per color, allowing an RGB LED to reach 10.5 Gbps – meaning speeds from device to access point will outpace most network infrastructure capability.
A number of manufacturers are already on board with 802.15.7, including Philips, Panasonic, Siemens, Huawei, Casio, and China Telecom. pureLiFi (see www.pureLiFi.com) appears to be amenable to OEM partnerships.
I see a number of potential applications in the security arena, particularly as alternatives to wireless devices; however, just as every PoE system must have a UPS, if you are relying on the lighting infrastructure, you will want to make sure that the lights stay on (or have a back-up plan).
Ray Coulombe is Founder and Managing Director of SecuritySpecifiers.com and RepsForSecurity.com. Reach him at [email protected], through LinkedIn at www.linkedin.com/in/raycoulombe or on Twitter, @RayCoulombe.
