**2. Li fi technology**

The idea of Li-Fi was first given by Harald Haas from University of Edinburgh, UK, in his TED Global talks on Visible Light Communications. According to him Visible Light Communication is very simple, if the LED is on, the transmitted data is digit 1, if it is off, the transmitted data is digit 0. The LEDs can be switched on and off very quickly, which gives better opportunity for transmitting data. So the requirement in LEDs and a controller that code data into those LEDs (**Figure 1**) [1].

Depending on the data to be encoded or transmitted, the LED flicker rate is varied. Enhancements to be made in this method are like using combinations of red, green and blue LEDs or using parallel data transmission LED array to change the light's frequency with each frequency encoding a different data channel. By the above advancement it is possible to achieve a theoretical value of speed up to 10 Gbps, i.e. downloading a 1Gb file in just 30 seconds irrespective of the file format. It can be used in places such as hospitals, traffic signals and in modern medical instruments. Li-Fi can also be used underwater where 6 Wi-Fi [2].

In transportation applications, Vehicle-to-vehicle (V2V) communications are deliberated to play an important role in in the next decade to improve road safety and road capacity [1]. In recent years, V2V has been implemented using the mainstream technology called as Dedicated Short Range Communications (DSRC), a 5.9 GHz radio frequency (RF) technology. However, the conventional RF communications based V2V communications often agonized from low packet reception rate and long delay in high vehicle density scenarios, due to interference made by the huge number of nodes in the same network [3]. On the other hand, it is very difficult to visually identify the location of the transmitter sending a message is frequently difficult, as RF based transmissions are usually Omni directional and latest technologies have inadequate accuracy to support this. For vehicle localization, the most common technology used is GPS. However, the positioning error occurred in GPS devices is often more than 10 m creates it hard to find the transmitting vehicles when they are in close locations [4].

**Figure 1.** *Block diagram of Li-Fi.*

*Vehicle Collision Avoidance System Using Li-Fi DOI: http://dx.doi.org/10.5772/intechopen.98616*
