1. Reema Abdulraziq Supervisors: Dr.Mohammad Saleh Dr.Mohammad Smirat
Li-Fi Technology
Reema Abdulraziq
Supervisors:
Dr.Mohammad Saleh
Dr.Mohammad Smirat

2. Introduction
Li-Fi stands for “Light Fidelity” is found by the German physics Harald Haas in 2011.
It is faster and gives better bandwidth, efficiently and security than Wi-Fi.
It is used in the areas that can replace the Wi-fi router.
It transmit data via visible Light.

3. Introduction(Cont.)
Its name referred to the “visible light communication” technology.
The idea of the Li-fi was got from the lamp attempts by Haas.
The Li-fi is considered as a solutions of the Wi-Fi challenges.

4. Wi-Fi vs Li-Fi * Li-Fi and Wi-Fi can be compared in term of: Capacity
Efficiency
Availability
security

5. Wi-Fi vs Li-Fi(Cont.)

6. Li-Fi features On-off time toxicity free band High speed Airlines
underwater
Traffic control
street lambs

7. Light Emitting Diode

8. Components of LED
LED lamp
ballast
housing
others

9. How the Li-fi works
Li-Fi uses Light emitting diode (LED) for the data transition.
This is done by switching this LED on and off faster that the human eye can detect since it is considered that it is continuously on.
By this switching the data will be sent as binary code( 0s and 1s) to be stored in an LEDs array.

10. How the Li-Fi works(Cont.)
The photo detector(i.e. Light sensitive device) receives this signals(binary code) and converts it back to the original data.
This process is called the “Visible Light Communication (VLC)”.
In some cases that data may not be visible for the user, this will motivate to the dimming the Light for some period of time.

11. Li-Fi standard Li-Fi standard is IEEE 802.15 in 2011.
This standard determines the component of the Visible Light Communication (VLC) :
- Mobile to Mobile (M2M).
- Fixed to Mobile (F2M).
- infrastructure to Mobile(I2M).

12. Li-Fi standard(Cont.)
It determines also the focus of VLC on the data transmission range respect with the speed of transmission.
Data rate are supported from 100 Mbps to 100 kbps using different modulation techniques.

13. Li-Fi modulation techniques
On-off Keying(OOK).
Variable Pulse Position Modulation(VPPM).
Color Shift Keying (CSK).
Sub-Carrier Inverse PPM (SCIPPM).
Frequency Shift Keying(FSK).
SIM-OFDM(Sub-Carrier Index OFDM).

14. VLC communication(Overview)
VLC transmitter(i.e. LED)
VLC receiver(i.e. photodector and image sensor).
VLC modes of communication(i.e. infrastructure-to device and device-to-device communications).

15. VLC layers with OSI layers

16. The physical layer This layer same as the OSI layer.
It defines the electrical and physical specifications of hardware used.
The communication is done with small units of data called as “packets”.
This layer contains three different types with different data rates as PHY_1 and PHY_2 and PHY_3.

17. The physical layer(Cont.)
PHY_1 is low data rate (12 to 267 kpbs) , it is used for outdoor operation.
PHY_2 has moderate data rate of 1.25 to 96 Mpbs, it is used for indoor operations.
PHY_3 has a high data rate of 12 to 96 Mpbs , it is used for lighting and detectors.

18. Indoor operation Hospital wards Waste-collection facilities
High schools

19. Outdoor Light operations(applications)

20. Data link layer
It is used for sending and receiving the data bits over the communication layer.
It has two sub-layers:
- Optical wireless Logic Link control (OWLC)
- Optical wireless Media Access Control (OWMAC)

21. Li-Fi frame modes

22. The frame structure
PHY frame:

23. The frame structure(Cont.)
MAC frame:

24. Link layer
Medium Access Control(MAC).
Cell design and coordinator.

25. Medium access Control(MAC)
VLC topologies
Multiple Access Control schemes

26. VLC topologies
peer-to-peer
star
broadcast

27. Multiple Access Control schemes
Carrier Sense Multiple Access(CSMA)
Orthogonal Frequency Division Multiple Access(OFDM)
Code Division Multiple Access (CDMA)

28. Applications Hospitals Car(traffic) communication Underwater Airlines
street lamps
Power plants
traffic lights

29. Vehicle-to-Vehicle communication via LED

30. Traffic light

31. Advantages and limitations
There are three main Li-Fi advantages:
- high speed data transmission
- security
- low cost
while its limitations are :
- The short range.
- It does not guarantee the receiving process.

32. Pure Li-Fi advantages Full duplex communication Full mobility
Multiple users
Secure
Safe
Flexible deployments
Extensive range of wireless communication applications
A cost-effective delivery of light and data via a single infrastructure

33. Pure Li-Fi access point
Support for Power over Ethernet (PoE) or Power Line Communications (PLC)
Simple installation
Connect to a wide range of LED light fixture to form an atto-cell 
Multiple access
Handover control enables seamless switching between APs

34. Pure Li-Fi station USB 2.0 powered
Supports handover, allowing user to move maintain their wireless session

35. Li-Fi simulations There are three main simulators for the Li-Fi:
- OptSim
- NS3
- Proteus ISIS

36. Li-Fi vs Wi-Fi in term of the reliabilty
Li-Fi is not in the similar reliability compared the Wi-Fi for several reasons:
1. it is based on optical antenna(i.e. Field of view (FOV)), varies from one device to another.
- This variety will affect transmission reliability.
2. According FOV is unknown, this will cause an interference between devices that will makes the traditional access protocol in VLC unreliable.

37. IEEE 802.15.7 PHY uses Manchester Run Length Limited(RLL).
RLL avoids the long runs of light on and light off that will affect the flicker.
- in term of data recovery detection problem.
Binary information is considered as two symbols High and Low which refer to the light presence and absent, respectively

38. IEEE (cont.)
In this standard the bit “1” (i.e. the light on) can be implemented as “Low-High” while the bit “0” as “High-Low”.
Example: two nodes, A and B:
- When A is idle when it transmit Low symbol then it can receive a data from B.
- This process is done as follows:

39. IEEE (cont.)
A will receive a high symbol from B which will create the “1” symbol in the chart of the binary code( 0s and 1s).
There are two assumption:
- B received a high symbol and transmit it to A.
- A receive this symbol, thus we can build that the bit “0” and predict to receive a Low in the next step, so the bit “0” is “high-Low” and “1” as “Low-high”

40. IEEE (cont.)

41. IEEE 802.15.7(cont.) However, there is a receiving problem
(i.e. Node A doesn’t expect to receive a symbol only if it transmit Low one because Node B can predict the Low symbol of “0” rather than the “1”).
In contrast, it becomes as a benefit of reduce the cost that will assume the node A has half of its data as “0” and the other as “1” since the B node will deal with the half of the A node data.

42. VLC advantages
1. Using OOK modulation technique, in off state will allow another device to transmit its data without the emission of the light.
- This will increase the system performance when increasing its throughput.
2. in LED-LED communication, one LED is used for both transmit and recieve the data.

43. VLC challenge and the solution
This communication have two challenges in how to build one LED with different FOVs and without additional optical components.
It is solved by using Carrier Sense Multiple Access/Collision Detection and Hidden avoidance(CSMA/CD & HA).

44. CSMA/CD & HA
This allows only one device to use on Light emitting diodes to transmit and receive the data that will reduce the occurred interference.
The frame is sent, the goal is to exploit this frame to build an optical channel then without using the light.

45. CSMA/CD & HA(cont.)
the optical channel play a significant role in term of :
1) transmission and receiving the data and the same time at the same channel.
2) allows for different FOVs without any interference occurs due its ability to make the channel more robust.

46. CSMA/CD & HA(cont.)
The following steps determine how this process is done to avoid the interference between the node:
1. sense the channel.
2. if the channel is clear, the frame is transmitted.
3. While is the channel is busy, a MAC will build a back off counter and the frame is transmitted when this counter becomes zero.

47. CSMA/CD & HA(cont.)

48. Hardware

49. Videos links Li-Fi https://www.youtube.com/watch?v=iHWIZsIBj3Q
Pure Li-Fi

50. Videos links(Cont.) Traffic Light simulation
visible light communication-Audio transmission

51. Videos links(Cont.)
Video- Lightweight Visible Light Communication for Indoor Positioning