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Visible light communication


  • 1. Khulna University of Engineering & TechnologyVisible Light Communication:Opportunities, Challenges andthe path to market.Written by:Aleksandar Jovicic, Junyi Li, andTom RichardsonPresented by: Shuvo Raj PaulRoll Number: 10031109/27/2014 1

2. Contents Introduction. Visible light & its spectrum. Motivation: Why visible light is used for communicationpurpose? The VLC communication process based on intensitymodulation. LED modulation characteristics. VLC link capacity for typical office desk-level illumination. Integration with power line communication (PLC) for the VLCdownlink. Integration with the uplink technology such as Wi-Fi. Conclusion.9/27/2014 2 3. What isVisible Light Communication ?The visible light communication (VLC)refers to the communication technologywhich utilizes the visible light source as asignal transmitter, the air as a transmissionmedium, and the appropriate photodiode asa signal receiving component.9/27/2014 3 4. Visible LightVisible light is thus by definition comprisedof visually-perceivable electromagnetic waves.The visible spectrum covers wave lengthsfrom 380 nm to 750 nm.Visible Light Spectrum9/27/2014 4 5. Why Visible light communication is needed ??? The visible light spectrum is unlicensed & creates anopportunity for low-cost broadband communication. VLC signals in adjacent rooms or apartment units would notinterfere with each other & data security is ensured. The front-end components of both transmitters andreceivers are relatively simple and cheap devices. The human eye cannot perceive the amplitude modulationof light as long as the frequency of modulation is above theso-called flicker fusion threshold.9/27/2014 5 6. THE VLC COMMUNICATION PROCESS BASED ONINTENSITY MODULATIONFig-1: The VLC radio transmitter and receiver based onintensity modulation/direct detection.9/27/2014 6 7. LED MODULATION CHARACTERISTICS:Fig-2: Frequency response of high-powered BRLUX-2670 LED &BRLUX-560 LED.9/27/2014 7 8. VLC link capacity for typical office desk-level illumination.Typical office desk-levellighting is between 400 and1000 lux. At 600 lux thecapacity of the link is around150 Mb/s.Fig-3. VLC link capacity as a function of received illuminancein lux. 600 lux is typical office desk-level illumination.9/27/2014 8 9. INTEGRATION WITH POWER LINECOMMUNICATION (plc) FOR THE VLC DOWNLINK.Since LEDs need a certainDC voltage to turn on, theycant run directly off of the60 Hz power cycle thatswhy bridge-rectifier or AC-to-DC converter is usedinside their power suppliesthat regulate the currentsupplied to the LED.Fig-4: The modifications to the LED lamp or fixture that are required toenable high data rate VLC signal transmission.9/27/2014 9 10. INTEGRATION WITH THE UPLINK TECHNOLOGYSUCH AS Wi-Fi.Fig-5: The uplink can use an out-of-band technology such asWi-Fi. The Hy-Fi router manages the VLC downlink and Wi-Fiuplink on a per user basis.9/27/2014 10 11. CHALLENGES IN COMMERCIALIZATIONOF VLC.Fig-6: Low Data Rate (LDR) Visible Light Communication that usessimple, power-efficient ON-OFF signaling can be decoded by thesmartphone camera sensor.9/27/2014 11 12. ConclusionVisible light communication can supplement radiofrequency communication and improve wirelessnetwork performance wherever short range linksare used such as in a home or office for downlinkInternet access or for device-to device file transfersand video streaming. It requires no additionalhardware in mobile devices. this use case is themost promising first step in the commercializationof VLC.9/27/2014 12 13. Thank you foryourkind attention9/27/2014 13