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Visible Light Communication

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by

Hemant Sharma

on 31 October 2012

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Transcript of Visible Light Communication

Visible Light
Communication White Light LED Complex Modulation Method 600 TB/month PPM: Pulse Position Modulation
FSK: Frequency Shift Keying
OFDM: Orthogonal Frequency
Division Multiplexing 1.4 million 5 billion Capacity Efficiency Availability Security Electromagnetic Spectrum Comparison General Lightning Solution Incandescent bulb
First industrial light source
5% light, 95% heat
Few thousand hours of life Fluorescent lamp
White light
25% light
10,000s hours Solid-state light emitting diode (LED)
Compact
50% light
More than 50,000 hours lifespan New technology, expensive and short life time. It is, however, very potential Popular for today general lighting, efficient and cheap Well-known technology, limited use, problem with balancing each R, G, B component to create white light RGB Blue Chip+Phosphor OLED VLC Transciever In an OFDM system, a high data rate serial data stream is split up into a set of low rate sub-streams
The parallel data transmission offers possibilities for alleviating problem of intersymbol interference (ISI) in serial comm.
The total channel bandwidth is divided into a number of orthogonal frequency subchannels. Applications Under water communications System Indoor broadcasting system. Inside Airplane Communication Vehicle to vehicle messaging Thank You Q n A Presented By:
Jitender Yadav PPM: Pulse Position Modulation Pulse-position modulation of the data 1, 0, 1, 0,0, 1, 1, 1, 0, 0, 1, 0, 1, 1, 0, 1 is modulated into a succession of pulses with SC-4PPM and SC-2PPM. Frequency Shift Keying In FSK data is represented by varying the frequency of carrier wave. OFDM VLC Standards JEITA CP-1221 Japan Electronics and Information Technology Industries Association Restricts the wave length of all emitted light to be within a range of 380 nm to 750 nm
Suggests using Sub Carrier - Pulse Modulation
Defines three major frequency ranges
15 kHz to 40 kHz
40 kHz to 1 MHz
> 1 MHz Japan Electronics and Information Technology Industries Association JEITA CP-1222 Supposed to be used only for communication purposes
Restricts the sub carrier frequency to 28.8 kHz
Suggests using Sub Carrier - 4 PPM as Modulation Scheme IEEE 802.15 TG7 The IEEE has formed Task Group 7 which is supposed to write a PHY and MAC standard for VLC
Physical Layer (PHY) defines the electrical and physical specifications for devices
Media Access Control (MAC) data communication protocol sub-layer provides addressing and channel access control mechanisms LOCALISATION Can be used for estimating one's loction
Proposes a scenario for Visually Challenged people Radio waves do not propagate for a long distance under water It is demonstrated that the flashlight visible light transmitter was able to transmit signals for 30 meter distance
Full transcript