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Light Signals: Li-Fi offers a promising approach to wireless communications

April 07, 2017
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The exponential increase in wireless data traffic over the past few years has led to clogging of the radio spectrum, making it difficult to access consistent and high speed signals. Light fidelity (Li-Fi) offers a promising solution to this problem.

Li-Fi is a wireless technology that makes use of visible light spectrum, in place of radio frequency spectrum, to transmit data at terabit per second speeds — more than 100 times the speed of wireless fidelity or Wi-Fi. The use of light spectrum for Li-Fi overcomes the issues in traditional wireless communications such as spectrum shortage and network disruption on account of interference.

Although the concept of Li-Fi emerged in the last decade, the proofs of concept to test commercial deployments started emerging only in 2015. Li-Flame, described as the world’s first true Li-Fi system, was displayed at the Mobile World Congress in Barcelona in March 2015. Li-Fi is also being tested in Dubai by the UAE-based telecommunications provider, du and Zero1. du claims to have successfully provided internet, audio and video streaming over a Li-Fi connection. Reportedly, Apple is also planning to build future iPhones with Li-Fi capabilities.

Working of Li-Fi

A Li-Fi system requires two components for functioning - a light source equipped with a signal processing unit and at least one device with a photodiode able to receive light signals. The light source could be a fluorescent or light emitting diode (LED) bulb. Since a robust Li-Fi system requires extremely high rates of light output, LED bulbs are the most suitable for Li-Fi. LED bulbs are semi-conductor devices and can amplify light intensity and switch rapidly. LED bulbs can therefore modulate thousands of signals and this modulation is imperceptible to the human eye.

The changes in the light intensity from the LED bulbs are interpreted and converted into electrical current by the receiving photodiode device. Once these electronic signals are demodulated, they are converted into a continuous stream of binary data comprising audio, video, and web applications suitable to be consumed by any internet-enabled device.

Li-Fi can work during the night time as well. The stream of photons from the LED bulbs can be reduced to a minimal level that will not produce visible light but dense enough to carry data.

Applications of Li-Fi

Since the visible light spectrum is much safer than the radio frequency spectrum, Li-Fi can be used in electromagnetic sensitive areas such as aircraft cabins, hospitals and nuclear power plants. It can also easily work under water, where Wi-Fi fails completely, and hence can help in undertaking military and navigational operations.

Li-Fi can also be immensely beneficial in traffic management. Vehicles having LED-based headlights and tail lamps can communicate with each other and prevent accidents by exchanging information. Moreover, each traffic and street light post can be converted into access points to convert roadsides into wireless hotspots.

Li-Fi versus Wi-Fi

Both Wi-Fi and Li-Fi transmit data over the electromagnetic spectrum, but whereas Wi-Fi utilises radio waves, Li-Fi uses visible light. Due to the burgeoning data traffic, the radio frequency spectrum used for Wi-Fi is close to full capacity. On the other hand, Li-Fi has almost no limitations on capacity since the visible light spectrum is 10,000 times larger than the entire radio frequency spectrum. Moreover, this spectrum is unregulated by the government. In addition, Li-Fi can achieve about 1,000 times the data density of Wi-Fi, since light can be contained in an area.

Also, since light rays are unable to pass through walls and similar structures, Li-Fi provides more security to the network and eliminates the risk of signal leakage to eavesdropping.

However, a key drawback of Li-Fi is that since visual light cannot pass through opaque objects and needs line of sight for communication, its range will remain very restricted to start with. Also, it is likely to face interference from external light sources, such as sunlight and bulbs, and obstructions in the path of transmission, and hence may cause interruptions in communication.

Another major challenge is the lack of a Li-Fi ecosystem. There is a need to convert existing smartphones into Li-Fi-enabled ones by the use of a converter/adapter. Also, an integrated chip that has both light-to-electrical conversion and data-processing capability (Wi-Fi/Bluetooth) needs to be developed.

Future prospects

Going forward, using Li-Fi, every LED lamp (both indoor and outdoor) can be converted into a hotspot to achieve universal broadband communication between devices. Also, it presents another unique possibility wherein the smartphone will not only receive data through Li-Fi, but will also receive power to charge itself.

While Li-Fi is not expected to completely replace Wi-Fi any time soon, the two technologies could be used complementarily to create more efficient, green and future-proof access networks. According to various industry estimates, the potential market for Li-Fi solutions is expected to be around $100 billion by 2022.

By Puneet Kumar Arora


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