A Survey on WIFI and LIFI technologies

ANIL B C1 D JANARDHANA2 CHAYADEVI M L3 Asst Prof, Dept of ISE Asst Prof, Dept of ISE Assoc Prof & Head, Dept of ISE

Jssateb, Bengaluru.India Jssateb, Bengaluru,india Jssateb, Bengaluru,India [email protected] [email protected] [email protected]

Abstract— Communication is one of the important attribute in developing area of internet. There are so many communication networks used in internet to transfer data and to communicate in that Wi-Fi and Li-Fi are two major wireless networks. The Wi-Fi stands for Wireless Fidelity and this technology is completely established in 1999 and it is used to provide internet access to devices that are within the range of wireless network that is connected to the network Wi-Fi uses radio waves for data transfer. The Li-Fi stands for Light Fidelity is completely established in 2011 and still research is going on this technology and it is a visible light communication that uses LED’s for data transfer. Keywords—Li-Fi, Wi-Fi, LED (Light Emitting Diode), wireless communication.

I. INTRODUCTION

Data transfer from one place to another is one of the most important aspect in our daily activities . There are so many computer networks are available to transfer data in that wireless network is type of computer network that uses wireless data connections for connecting nodes. The history of wireless networks is in 1971 ALOHA net was introduced it is a seminal packet radio system that connected Hawaii islands with a radio network. In 1991 2G cell phone network was introduced it is an network to transfer data from cell phones to nodes. In June 1997 802.11 "Wi-Fi" protocol was introduced and in 1999 803.11 “Wi-Fi “was completely established.

II. Wi-Fi

Wi-Fi networking is possible because of radio signals. These radio signals transmitted from Wi-Fi antennas are picked up by Wi-Fi receivers, such as computers and cell phones that are equipped with Wi-Fi cards. Whenever, a computer receives any of

the signals(as shown in the figure 1) within the range of a Wi-Fi network, which is usually 300 -500 feet for antennas, the Wi-Fi card reads the signals and thus creates an internet connection between the user and the network without the use of a cord.[6]

Fig 1:Wi-FI Radio signals [6]

A. Wi-Fi Standards The 802.11 standard is defined through several specifications of WLANs. It defines an over the air interface between a wireless client and a base station or between two wireless clients. There are several specifications in the 802.11 family • 802.11: This pertains to wireless LANs and

provides 1 or 2 Mbps transmission in the 2.4 GHz band using either frequency hopping spread spectrum (FHSS) or direct-sequence spread spectrum (DSSS).

• 802.11a: This is an extension to 802.11 that pertains to wireless LANs and goes as fast as 54 Mbps in the 5 GHz band. 802.11a employs the orthogonal frequency division multiplexing

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(OFDM) encoding scheme as opposed to either FHSS or DSSS.

• 802.11b: The 802.11 high rates Wi-Fi is an

extension to 802.11 that pertains to wireless LANs and yields a connection as fast as 11 Mbps transmission (with a fallback to 5.5, 2, and 1 Mbps depending on strength of signal) in the 2.4-GHz band. The 802.11b specification uses only DSSS. Note that 802.11b was actually an amendment to the original 802.11 standard added in 1999 to permit wireless functionality to be analogous to hard-wired Ethernet connections.

• 802.11g: This pertains to wireless LANs and provides 20+ Mbps in the 2.4-GHz band.[6]

• 802.11n: The more advanced can transmit a maximum of 140 megabits of data per second and uses a frequency level of 5GHz.

B. Advantages of Wi-Fi • Convenience: The wireless nature of such

networks allows users to access network resources from nearly any convenient location within their primary networking environment.

• Mobility: With the emergence of public wireless networks, users can access the internet even outside their normal work environment.

• Productivity: Users connected to a wireless network can maintain a nearly constant affiliation with their desired network as they move from place to place. For a business, this implies that an employee can potentially be more productive as his or her work can be accomplished from any convenient location.

• Deployment: Initial setup of an infrastructure-based wireless network requires little more than a single access point. Wired networks, on the other hand, have the additional cost and complexity of actual physical cables being run to numerous locations.

• Expandability: Wireless networks can serve a suddenly-increased number of clients with the existing equipment. In a wired network, additional clients would require additional wiring.

• Cost: Wireless networking hardware is at worst a modest increase from wired counterparts. This potentially increased cost is almost always more than outweighed by the

savings in cost and labor associated to running physical cables.[9]

C. Disadvantages of Wi-Fi

• Security: To combat this consideration, wireless networks may choose to utilize some of the various encryption technologies available. Some of the more commonly utilized encryption methods, however, are known to have weaknesses that a dedicated adversary can compromise.

• Range: The typical range of a common 802.11g network with standard equipment is on the order of tens of meters. While sufficient for a typical home, it will be insufficient in a larger structure. To obtain additional range, repeaters or additional access points will have to be purchased. Costs for these items can add up quickly.

• Reliability: Like any radio frequency transmission, wireless networking signals are subject to a wide variety of interference, as well as complex propagation effects that are beyond the control of the network administrator.

• Speed: The speed on most wireless networks varies from 1-54 Mbps is far slower than even the slowest common wired networks (100Mbps up to several Gbps). However, in specialized environments, the throughput of a wired network might be necessary.[9]

III. Li-Fi

The term LIGHT FIEDILITY was first introduced by an professor Harald Haas at the University of Edinburgh in the UK. The current wireless networks that connect us to the internet are very slow when multiple devices are connected. As the number of devices that access the internet increases, the fixed bandwidth available makes it more and more difficult to enjoy high data transfer rates and connect to a secure network. But, radio waves are just a small part of the spectrum available for data transfer. A solution to this problem is by the use of Li-Fi. Li-Fi stands for Light-Fidelity. Li-Fi is transmission of data through illumination by taking the fiber out of fiber optics by sending data through an LED light bulb as shown in figure 2 that varies in intensity faster than the human eye can follow.[1]

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Fig 2: Li-Fi Bulb[10] A VLC (Visible Llight Communication) light source could comprise of a fluorescent or light emitting diode (LED) bulb. Since a robust Li-Fi system requires extremely high rates of light output, LED bulbs are most ideal for implementing Li-Fi. LED is a semiconductor light source, which implies that LED light bulbs can amplify light intensity and switch rapidly. Therefore, LED cells can modulate thousands of signals without the human eye ever noticing. In turn, the changes in light intensity from the LED light source are interpreted and converted as electrical current by the receiving photodiode device. Once the electronic signal is demodulated, it is converted into a continuous stream of binary data comprising of audio, video, web, and application information to be consumed by any Internet-enabled device. There is ample room for growing innovation in Li-Fi technology. Like conventional broadband and Wi-Fi, Li-Fi can also function as a bidirectional communication system. By interchanging visible light and infrared light from a photo detector, a mobile device connected to that photo detector can send data back to the light source for uplink. Also, multi-colored RGB (Red/Green/Blue) LED's at retina size could be engineered to send and receive a wider range of signals than single-colored phosphor-coated white LED's.[2] LEDs can be switched on and off to generate digital strings of different combination of 1s and 0s. To generate a new data stream, data can be encoded in the light by varying the flickering rate of the LED. The LEDs can be used as a sender or source, by modulating the LED light with the data signal. The LED output appears constant to the human eye by virtue of the fast flickering rate of the LED. Communication rate greater than 100 Mbps is possible by using high speed LEDs with the help of various multiplexing techniques [4]. VLC data rate can be increased by parallel data transmission using

an array of LEDs where each LED transmits a different data stream. The Li-Fi emitter system consists of 4 primary subassemblies [7]: • Bulb

• RF power amplifier circuit (PA)

• Printed circuit board (PCB)

• Enclosure

Fig 3: Block diagram of Li-Fi sub-assemblies [2] The PCB controls the electrical inputs and outputs of the lamp and houses the microcontroller used to manage different lamp functions. A RF (radio-frequency) signal is generated by the solid-state PA and is guided into an electric field about the bulb. The high concentration of energy in the electric field vaporizes the contents of the bulb to a plasma state at the bulb‘s center; this controlled plasma generates an intense source of light. All of these subassemblies is shown in Fig. 3 are contained in an aluminum enclosure. [3].

IV. IMPLEMENTATION OF LI-FI

Li-Fi is typically implemented using white LED light bulbs at the downlink transmitter. These devices are normally used for illumination only by applying a constant current. However, by fast and subtle variations of the current, the optical output can be made to vary at extremely high speeds. This very property of optical current is used in Li-Fi setup. The operational procedure is very simple-, if the LED is on, you transmit a digital 1, if it’s off you transmit a 0. The LEDs can be switched on and off very quickly, which gives nice opportunities for

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transmitting data. Hence all that is required is some LEDs and a controller that code data into those LEDs. All one has to do is to vary the rate at which the LED’s flicker depending upon the data we want to encode. Further enhancements can be made in this method, like using an array of LEDs for parallel data transmission, or using mixtures of red, green and blue LEDs to alter the light’s frequency with each frequency encoding a different data channel. Such advancements promise a theoretical speed of 10Gbps meaning one can download a full high-definition film in just 30 seconds.[2].Architecture of Li-Fi model is shown in the figure 5..

Fig 5: Architecture of Li-Fi[11]

A. Advantages of Li-Fi • Capacity: Light has 10000 times wider

bandwidth than radio waves [5]. Also, light sources are already installed. So, Li-Fi has got better capacity and also the equipments are already available.

• Efficiency: Data transmission using Li-Fi is very cheap. LED lights consume less energy and are highly efficient.

• Availability: Availability is not an issue as light sources are presents everywhere. There are billions of light bulbs worldwide; they just need to be replace with LEDs for proper transmission of data.

• Security: Light waves do not penetrate through walls. So, they can‘t be intercepted and misused.

B. Applications of LIFI

• Education system. • Medical Application. • Cheaper Internet in Aircrafts. • Underwater application. • Disaster management.(Earthquake/hurricane) • Applications in sensitive area. (Nuclear power plants) • Traffic management • Green information technology. (No side effects on birds) • Replacement for other technologies. (Bluetooth, infrared, Wi-Fi, etc. are banned).[2]

C. Limitations of LI-Fi

• For instance light cannot pass through walls. • You cannot enjoy internet without light source

(sun or bulb). • Li-Fi's biggest drawback apart from walls is

inability to provide uninterrupted internet outdoor (Even during day) Sun light would interfere with its signal.[7]

D. Li-Fi versus Wi-Fi

TABLE 1: Li-Fi versus Wi-Fi [8].

Parameters Li-Fi Wi-Fi Speed High High Range Low Medium Data density High Low Security High Medium Reliable Medium Medium Power available High Low Transmit/receiver power High Medium Ecological impact Low Medium Device to device connectivity High High Obstacle interference High Low Bill of materials High Medium Market maturity Low High

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V. CONCLUSION

There are so many wireless technologies used across the world in that Wi-Fi and Li-Fi are two technologies .Wi-Fi is usd widely and efficiently in each and every environment but recent days many research is going on Li-Fi technology Li-Fi is certainly not useless, but it has certain inherent limits for the technology. Li-Fi may not be able to replace conventional radios altogether, but it could turbo charge the development of wireless television and make it easier to throw a wireless signal across an entire house. At present, finding the ideal position for a wireless router is something of a divine art. If the signal could be passed via VLC from Point A to Point B inside a home, small local routers at both points could create local fields with less chance of overlapping and interfering with each other. Large scale areas that are saturated with radio signals or that doesn’t permit them for security reasons could use Li-Fi as an alternate high-speed wireless network solution.

ACKNOWLEDGEMENT

We would like to acknowledge the contribution of all the people who have helped in reviewing this paper we would also like to thank our families and friends who supported us in the course of writing this paper.

REFERENCES [1] Rahul R sharma, “LIFI Technology,”

Int.J.Computer Technology & Applications,Vol 5 (1),150-154.

[2] Dhakane Vikas Nivrutti, Ravi Ramchandra Nimbalkar,” Light-Fidelity: A Reconnaissance of Future Technology” International Journal of Advanced Research in Computer Science and Software Engineering, Volume 3, Issue 11, November 2013.

[3] An IEEE Standard for Visible Light Communicationsvisiblelightcomm.com, dated April 2011.Tsonev, D.; Sinanovic, S.; Haas, Harald (15 September 2013). "Complete Modeling of Nonlinear Distortion in OFDM-Based Optical Wireless Communication". IEEE Journal of Lightwave Technology 31 (18): 3064– 3076.doi:10.1109/JLT.2013.2278675

[4] Iain Thomson (18 October 2013). "Forget Wi-Fi, boffins’ get 150Mbps Li-Fi connection from a light bulb: Many (Chinese) hands make light work". The Register. Retrieved 22 October 2013.

[5] Haas, Harald (July 2011). "Wireless data from every light bulb". TED Global. Edinburgh, Scotland.

[6] http://www.tutorialspoint.com/wifi/wifi_working_concepts.htm

[7] http://www.lifi.com/pdfs/techbriefhowlifiworks.pdf

[8] http://www.techtreme.com/internet/li-fi-vs-wi-fi-how-it-works/

[9] http://ipoint-tech.com/wireless-networking-wi-fi-advantages-and-disadvantages-to-wireless-networking/

[10] https://recombu.com/digital/article/china-lifi-kits-150mbps-broadband-speeds-over-led-bulbs_M12309.html.

[11] http://www.slideshare.net/sibasishsamantha/li-fi-29425716.

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