Visible Light Communication: Concept, Technology ...wcnc2013.ieee-wcnc.org/WCNC.T10.Slides.pdf ·...

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Visible Light Communication: Concept, Technology,

Challenges and Possibilities Navin Kumar (PhD)

MIEEE, IET(UK), IAEG(HK), IE, IETE(India)

CMR Institute of Technology, Bangalore -India

Jiao Tong University Shanghai

3/25/2013

2

Agenda

Introduction

Optical Wireless

Visible Light Communication

Infrared

Free Space Optics

Basic Components and Configuration

Motivation

LED Advancement

Agenda …

3

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Characteristics

Applications

Technical Details

Architecture and VLC System

Modelling Development

Prototype, Testing & Results

Progress & Current Status

Conclusion

Introduction

Visible Light Communication ?

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0 1 0

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0

1 0 1

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1 0

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1 0 0 1

1 0 1

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0 1

1 1

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Tx

Rx

Communication using visible light Wirelessly.

Introduction: History

Smoke signals of the ancient tribes

The use of fire or lamp

Beacon fire, lighthouse, ship-to-ship comm.

5 3/25/2013 Traffic Signal

Information delivery using mirror reflection (Heliograph): is a wireless solar telegraph that signals using Morse code flashes of sunlight reflected by a mirror. Traffic light : R/G/B color multiplexing (Walk/Stop)

Introduction: History …

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Alexander Grahm Bell’s Photophone (1880)

Optical source: sunlight Modulation: vibrating mirror Receiver: parabolic mirror Distance: 700 ft (213m)

Source: http://www.freespaceoptic.com/

In 1920, somewhat by accident, Losev foresaw the usage of optical links to relay information.

In 1969, Gfeller presented “Wireless In-House Data Communication via Diffuse Infrared Radiation”. It became the stepping stone to VLC.

Facts, Figures, and Trends of Wireless Networks and Technology

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Several Technologies move in the same direction

4G Many

Access Networks

5G

Introduction

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Introduction

Wireless data transmission via optical carriers: opportunity, many yet unexplored.

Optical Wireless Communication (OWC): Significant technical and operational advantages.

OWC, in some applications:

–a powerful alternative to radio frequency (RF) and,

–complementary to existing RF wireless systems. 9 3/25/2013

Frequency Spectrum

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1024 1022 1020 1018 1016 1014 1012 1010 108 106 104 102 100 ν(Hz)

λ(m)10-16 10-14 10-12 10-10 10-8 10-6 10-4 10-2 100 102 104 106 108

Increasing Frequency(ν)

Increasing Wavelength(λ)

380nm 780nm

γ rays X rays UVMicrowaveIR FM AM

Radiowave

Longwave

Visible Spectrum

Licensing Area/ISMSpecial purposed Area

Non-Licensing Area

1024 1022 1020 1018 1016 1014 1012 1010 108 106 104 102 100 ν(Hz)

λ(m)10-16 10-14 10-12 10-10 10-8 10-6 10-4 10-2 100 102 104 106 108

Increasing Frequency(ν)

Increasing Wavelength(λ)

380nm 780nm

γ rays X rays UVMicrowaveIR FM AM

Radiowave

Longwave

Visible Spectrum

Licensing Area/ISMSpecial purposed Area

Non-Licensing Area

Low Frequency (High wavelength)

Large Coverage Mobility

High Frequency (Small wavelength)

High Bandwidth Security

IrDA : 334THz(900nm) to 353THz (850nm)

Introduction …

Variations of OWC can be employed in a diverse range of communication applications:

–very short-range (on the order of millimetres) optical interconnects within integrated circuits

–outdoor inter-building links (on the order of kilometres)

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Optical Wireless Communication and Systems

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Usually, OWC includes:

–Infrared (IR): for short range [Kahn & Barry, 1997],

- approximately 1 to 400 THz frequency

band,

(Much of the energy from the Sun arrives on Earth in the form of infrared radiation).

J. M. Kahn, and. J. R. Barry, "Wireless infrared communications," Proc. of the IEEE, pp. 265-298, 1997.

OWC – Infrared …

Used for -night vision equipment when there is insufficient visible light to see.

• Infrared imaging (capturing invisible infrared images and making them visible)

• as heating source

• IR data transmission in short-range communication

• These devices usually conform to standards published by IrDA, (Infrared Data Association).

• Remote controls, etc.

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OWC – Free Space Optics

Free-Space Optics communication: for longer range

This line-of-sight technology approach uses invisible beams (193.5GHz and 382.2GHz: 1550 nm, 785 nm) of light to provide optical bandwidth connections.

–A technology that can be installed license-free worldwide,

–can be installed in less than a day.

–Offers optical fiber like bandwidth and data speed

–Normally so called, Wide band Home Access or Last Mile Access Network

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FSO: Applications

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Fig.: A Simple Point-to-point FSO Connection

Fig.: FSO Corporate Networks

FSO: Applications

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FSO: System Requirement and Design Issues Tracking

The requirements for tracking systems in carrier-class free-space optics systems.

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Scintillation and atmospheric effects Scintillation effects and techniques for mitigating the detrimental effects of scintillation.

Power Control and Eyesafety The benefits of power control for long-term laser reliability and eyesafety

FSO: System Requirement and Design Issues

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Fig.: Atmospheric Issues

FSO: System Requirement and Design Issues ….

Ex.: Attenuation because of Fog/Snow storm

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Taken from - Scott Bloom, The Physics of Free-space optics, white paper AirFiber Inc.

FSO: Overall Functional Blocks

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Transmitter Laser, Lens, Driver

Receiver

Photo Detector Front End Amplifier

Tracking

Microprocessor based tracking/alignment system

Fig.: Overall FSO Block Diagram

BASIC COMPONENTS: OPTICAL WIRELESS

Transmitter

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Optics

Array of sources can also be used

Source

LED or Laser diode Eye safety regulation means that high power requires sources to be modified Three ranges:

Visible (used for both illumination and data transmission) Near infrared

700nm>Wavelength<1400nm- Low cost Wavelength>1400nm- Eye safe

OWC – Basic Components …

Receiver consists of:

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Photo Detector

- Optical power to photo current

Input radiation

Photodetector (or array of detectors)

Optical filter

Supported by: Optical filter

Rejects ‘out-of-band’ ambient illumination noise

Concentrator

AMP

Amplifier and following processing

Concentrator or Lens Collection of radiation

Preamplifier (or number of preamplifiers) normally Transimpedance

Amp. and signal processing

OWC Configuration

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Lin

e-o

f-sig

ht

(LoS)

Non LoS

BASIC CONFIGURATION: LoS OR DIFFUSE

Configuration Characteristics

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Diffuse -Multipaths from Transmitter to Receiver Robust to blocking

o Large coverage

- Path loss More - Subject to multipath dispersion

LoS - Single path from Transmitter to Receiver

No dispersion Path loss Less

o Very high bandwidth available

Difficult to provide coverage

OWC Characteristics

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MERITS - Very High Bandwidth

o 200THz carrier frequency

-Secure (LoS) -Cost Effective -Interference

o Suitable for RF sensitive

environments

-Potential for low power

Problems and possible Solutions - Noise from ambient light

o Optical filtering o Electrical filtering in receiver

- Less sensitive than radio - Link Blocking

o Geometrical solutions o Diffuse channels o Combine with RF

- Available components optimised for fibre-optic applications

o Higher performance available if optimised for OW

Development

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Optimal Integration into 4G Infrastructures

Emerging Area Visible Light Communication

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Visible Light Communication (VLC)

That is, Communications of information using light (visible to the human eyes).

VLC offers short/medium range data communication

Visible Light Communication is a Novel kind of Optical Wireless Communication which uses visible light (400THz to 790THz) from Light Emitting Diodes (LEDs) as a medium for data communication.

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VLC Motivation

Intrinsic Characteristic of VLC •Visibility •No interference /No regulation

Environmental trend •Energy saving •Green Technology

Communication Community trend •Ubiquitous (Connected anywhere, anytime) •Security

LED Advancement •LED technical evolution (efficiency, brightness) •LED illumination infrastructure

Advancement in LEDs Technology.

Mostly in terms of Illumination

characterisitics & Switching speed.

LEDs as brighter as our conventional lights (Fluorescent or Incadescent lamp)

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VLC Motivation …

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VLC Motivation – LED Illumination

0

20

40

60

80

100

120

140

160

180

200

2 7 1020

3040

47

115

136

186

200lm/WLuminous Efficacy

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VLC Motivation –LED Advancement

Therefore, Visible Light emitted from LED can be modulated to send information data i.e. Simultaneous operation of Lighting and Switching.

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VLC Motivation…

Free Spectrum (Best things in life are free )

At the same time, LEDs can switch at high rate (over 10 MHz) [as such they are Semiconductor devices]

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VLC Motivation – LED Applications

Illumination moving from incandescent/ fluorescent to solid state sources (LEDs) - Predicted to become predominant method for room illumination - Used extensively in traffic systems (traffic signals, rear light cluster) - Headlight is being also used - Extra wireless capacity available at (potentially) low cost

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LED- The VLC Source

Single chip LED spectrum

Red Green Blue Higher cost Higher bandwidth For WDM Modulation without colour shift

Blue LED & Phosphor Low cost Phosphor limits bandwidth Modulation can cause colour shift

General Characteristics:

Ubiquitous: Omni-presence.

Harmless for human body and electronic devices.

Available visible light bandwidth is about 300THz. It is considerably larger than the current available radio frequency bandwidth (about 300GHz)

Achievable at Low Cost and on Existing Infrastructure or with slight modification

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VLC Characteristics

Ambient interference:

Obstacles: Must obtain a Line-of-Sight (LoS).

Interferences from other visible light sources (sun, bulbs…)

Also suffer from the multi-path effect as light reflects.

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VLC Characteristics

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VLC Characteristics: Relative Advantages and Disadvantages with Radio and Infrared (IR) Communication Parameters Radio Infrared VLC

Bandwidth Around 300GHz Few 100 THz 300 THz

Data Rate Few 100 Mbps Few 10 Mbps Dependent on distance and limited by LED switching speed

Spectrum Regulation

Licensed Regulated & Licensed Not licensed

Safety Issue Susceptible to the biological damages to humans by the electromagnetic wave.

Eye safety problem No danger to eyes or biological effect. Easily used with medical instruments or even on airplane.

Usage Everywhere with cell phones and the wireless LAN, etc

Notebook, Cell Phone, PC etc.

Getting popularity

Suitability Wide applications and popularity. Restricted in Hospital and airplane

Short range (mostly indoor)

Short & Medium, both indoor and outdoor

Implementation and cost

Complex, Costly Easier, cost effective Cost effective, Used on existing infrastructure or with slight modification

Security Many complex algorithm needed

May be secured (very short distance)

Secured (What you see is what you transmit)

Complex and Challenging VLC Can be a supplementary and not replacement to Radio

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RF or Optical Link?

OW OW

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VLC Applications

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VLC Applications

Indoor

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VLC Applications …

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VLC Applications: Indoor

LiFi Configuration

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VLC Applications: Indoor …

Music Broadcast Parallel Transmission (Taken from Nakagawa Lab, Japan)

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VLC Applications: Outdoor

UNDERWATER

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VLC Applications: Outdoor

Intelligent Transportation Systems

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VLC Applications: Outdoor

5m

7m

3m

30mLED Lights

A scenario of VLC in ITS Ubiquitous Communication with Road Illumination

Intelligent Transportation Systems

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VLC Applications: Outdoor

What’s behind the bend?

Integration of VLC with ITS

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VLC Applications: ITS-Road Safety

VLC For Advanced Driver Assistance Systems

SMART LIGHTING

MOBILE CONNECTIVITY

HAZARDOUS ENVIRONMENTS

VEHICLE & TRANSPORTATION

DEFENCE & SECURITY

HOSPITALS & HEALTHCARE

WiFi SPECTRUM RELIEF

AVIATION

UNDERWATER COMMUNICATIONS

LOCATION BASED SERVICES 3/25/2013 50

Summary of Top 10 Applications: VLC

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The System and Technique: VLC

Technical Details

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Overall Architecture

Fig. A VLC System (Overall Architecture)

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VLC Transmitter and Receiver

Emitter Characteristics and Model:

LED (Lambertian Model):

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VLC Modelling

where θ is the viewing angle and E0(d) is the irradiance (W/m^2), also given in luminous flux (lm) on the axis at a distance d from the LED.

Fig.: Lambertian Emitter Source

(1)

The number m is given by the half power angle, θ1/2 an angle provided by the manufacturer, defined as the view angle when irradiance is half of the value at 0°.

The relation between θ1/2 and m can be expressed,

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VLC Emitter Model …

(2)

(3)

Radiation Pattern

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VLC Emitter Model

Fig.: Radiation Pattern for different m Fig.: Normalized Radiation Pattern for different m

Multiple Emitting Sources

Single Circular Ring case:

Multiple ring case:

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LED Emitter Model …

(4)

(5)

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Emitter Circuit

V = Vcc = +24VR1 = 15KΩR2 = 490 ΩR3 = 850ΩRin1 = 51ΩRin2 = 300ΩCin = 100nFQ(β) = 102.64

+

V+V+

Vdata

R1

R2 R3

Rin1

Rin2 Cin

Q

HB-LED

Discrete Current-sink Optoelectronic Emitter

Topology

ID@ different Frequency (a)@ 100KHz (b) @ 1 MHz (c) @ 10MHz (d) Constant Value

Vdata

Logic high

(3v) 38.1 mA 39.0 mA 40.0 mA 34.6. mA

Logic Low

(0V) 10.4 μA 12.6 μA 42.9 μA

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Performance: Switching

0 2,5 5 7,5 100

10

20

30

40

50a) f = 100kHz

[ms]

[mA]

0 0,25 0,5 0,75 10

10

20

30

40

50b) f = 1MHz

[us]

[mA]

0 25 50 75 1000

10

20

30

40

50c) f = 10MHz

[ns]

[mA]

0 0,1 0,2 0,3 0,4 0,50

10

20

30

40

50d) constant value

[s]

[mA]

Optoelectronic Emitter- time domain Response at Different Frequencies

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Performance

Optoelectronics Emitter- gain/phase Response (ID⁄IRin2 )

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VLC Receiver Model

The RECEIVER is defined by the active area and is a function of field of view and incident angle.

where Ad is the area of the detector

σ is the angle of incident

FOV is the field of view

Photo Detector

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Receiver Circuit

Block Diagram of Optoelectronic VLC Receiver

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Receiver Circuit …

Preamplifier Topology

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Pre-Receiver Circuit Response

Phase/Gain plot for different values of RF and CPD

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Receiver Circuit

Photo Detector

Transimpedance Front-End Preamplifier

Low Pass Filter(2nd Order) High Pass Filter

(3rd Order)

Output Amplifier, ADC Driver, Voltage Limiting

Impedance Matching

SMA Connector

Output

Receiver Circuit Diagram (OrCAD Captured Schematic)

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Response of Overall Receiver

1 10 100 1k 10k 100k 1M 10M 100M 1G

-100

-50

0

50

100

Gain (Vout/Iin)

[Hz]

[dB]

1 10 100 1k 10k 100k 1M 10M 100M 1G-360

-270

-180

-90

0

90

[Hz]

[º] Phase (Vout/Iin)

Response curve of Overall Receiver

Both Possibilities

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VLC Modelling - Indoor

Typical Arrangement in a room

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VLC Modelling - Indoor

1m

2.15m 3.15m

5m

From One Single LED

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Experimental Measurement

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Experimental Measurement

LED Modulation Received Signal Appox. 2Mbps

Signal–to–noise ratio distribution in the room

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Simulation Performance

SNR 35 – 50 dB

Data rate over 1 Mbps

MULTILANE ROAD Traffic Light Set-up

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Traffic Light Arrangement for the Channel Model: Outdoor (ITS)

Important Parameters

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Traffic Light Arrangement for the Channel Model ….

Channel Gain vs Distance

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Channel Gain over Distance.

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Field Programmable Gate Array & Hardware Implementation

PN Code

Sequence Corr. Pk

Partial Corr. Pk

Observations

Novel Designed

+1+1+1-1-1 -1+1-1-1+1

±10

±2

-DC Balanced -Low resources -Easy Implementation -PG = 10dB

Barker +1+1+1-1-1-1+1-1-1+1-1

±11

±1

-Nearly DC Bal. -High Resource -Complex -PG = 10.4dB

PN Code

Input Data

MicroBlaze

DPLB

IPLBILMB

DLMB INTR

BRAM

INTC UART

LMB

LMB

PLBClock

IRQ Lines

50 MHzMB

PLBLMB

SIK

DataBuffer

+Frame

Processing

Binary

DSSS EMITTER CORE

AWGN(channel SNR

simulation)

Bipolar to

Unipolar

Output to Optoelectronics

GPIO

Frame

Processing

ClockManager

Unipolar to Bipolar

ADC

GPIO

Output Data

MicroBlaze

DPLB

IPLB ILMB

DLMBINTR

BRAM

INTCUART

LMB

LMB

PLB Clock

IRQ Lines

50 MHzMBPLBLMB

DSSS RECEIVER CORE

Input from Optoelectronics

SYNC

Matched Filter

PN Code

Treshold Detector

PER Bipolar to Unipolar

EMITTER ARCHITECTURE RECEIVER ARCHITECTURE

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VLC Prototype Development

OPTOELECTRONICS AND FPGA DEVELOPMENT

VLC Receiver

OPTOELECTRONICS & FPGA

Receiver

FPGA Rx

FPGA Tx

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VLC Prototype Development and Experimental Set up

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VLC Prototype: Experiment- Laboratory Test

(1) Domingos Terra, Navin Kumar, Nuno Lourenço, Luis Nero Alves, and Rui L. Aguiar,” Design, Development and Performance Analysis of DSSS-based Transceiver for VLC”, IEEE EUROCON, Lisbon, Apr. 2011

(2) Navin Kumar, Domingos Terra; Nuno Lourenço; Luis Nero Alves, and Rui L. Aguiar,” Visible Light Communication for Intelligent Transportation in Road Safety Application”, IEEE IWCMC 2011, Vehicular Communications Symposium, Istanbul, Jul 2011.

Traffci Light Emitter FPGA Rx

Software Running Laptop

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Experiment- Laboratory Test

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Experiment Outdoor

Bright Sky, Directly Under Sun at Noon time – Detector facing the Sun

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Experiment: Pavilion (60 x 40m)

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Experimental Results

0.0E+0

2.0E-6

4.0E-6

6.0E-6

8.0E-6

1.0E-5

1.2E-5

1.4E-5

1.6E-5

1.8E-5

2.0E-5

0 10 20 30 40 50 60 70

Receiv

ed

Po

wer (

W/

cm

2)

Distance (m)

Received Average Power over Distance

Axial Distance Received Power

Received Power at 3.5m Offset

from Axis

Received Average Power

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Experimental Results …

0

10

20

30

40

50

60

70

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100

0 2 4 6 8 10

Messag

e H

it [%

]

Signal-to-Noise ratio [dB]

25 Chars

50 Chars

100 Chars

256 Chars

Message

Received Message

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Experimental Results …

0

20

40

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100

0 10 20 30 40

Messag

e H

it [%

]

Distance [m]

Outdoor Night

Outdoor Night - Height Offset

Outdoor DayLight

Environment Test

(2,5m)

Percentage of Received Message

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Experimental Results …

Packet Error Rate

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Experimental Results …

1,0E-7

1,0E-6

1,0E-5

1,0E-4

1,0E-3

1,0E-2

1,0E-1

1,0E0

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Pac

ket

Erro

r R

ate

Distance (m)

Environment Test:

Control: Dark (Height Offset 1,65m)

Outdoor Bright Sun Light

Outdoor: Night

Packet Error Rate

2003: The Visible Light Communications Consortium (VLCC) is established between major Japanese companies to develop, plan, research and standardise Japan’s own visible light communication systems.

Its brief is to develop, test, investigate, plan and standardise ubiquitous high-speed biologically-friendly VLC LED systems.

21 members

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Progress & Current Status

www.vlcc.net

2007: The standardisation work undertaken by VLCC leads to the creation of the Japan Electronics and Information Technology Industries Association’s JEITA standards (2007) for a “visible light ID system”.

VLCC is also involved in preparing and publicising proposals for safe visible light communication technology standards for a variety of applications and fields of industry.

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Progress and Current Status …

2008: EU-funded OMEGA project seeks to develop global standards for home networks, including the use of optical wireless using infrared and VLC technology.

2009: Research continuing in Japan to increase viable communication distances for VLC to hundreds of meters.

–Such work will allow the transmission of information by light from billboards, and from new generations of traffic lights to automobiles and trains

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Progress and Current Status …

2009-12: IEEE 802.15 WPAN™ Task Group 7 (TG7) Visible Light Communication

–The IEEE 802.15.7 Visible Light Communication Task Group has completed a PHY and MAC standard for Visible Light Communications (VLC).

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Progress and Current Status …

http://www.ieee802.org/15/pub/TG7.html

2010: The data transmission speeds of VLC systems are shown to be rapidly improving, with a frequency-modulated white LED being shown by Siemens researchers and the Heinrich Hertz Institute in Berlin to be capable of transmitting information over 5 meters at a rate of 500 Mbps, significantly faster than present Wi-Fi technologies (that can operate at rates of up to 150 Mbps).

2010: Demonstration undertaken successfully in Japan showing the combination of VLC with indoor Global Positioning System (GPS).

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Progress and Current Status …

A £5M Research Programme on Visible Light Communications…

–‘Ultra-parallel visible light communications (UP-VLC)’,

–Collaboration between leading research groups at the Universities of Strathclyde, Edinburgh, St Andrews, Oxford and Cambridge.

–Its basis is the >1Gb/s modulation capability recently shown for individual micro-sized gallium nitride LEDs

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Current Status …

http://gow.epsrc.ac.uk/NGBOViewGrant.aspx?GrantRef=EP/K00042X/1 .

LiFi

Noise Sources

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Challenges & Opportunities

–Minimizing the effect of external noise (artificial or natural)

–Ambient lights effect

–Interference minimization

Uplink design

Long range communication (LoS link required), and many more ....

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Challenges & opportunities ..

High data rate (limitation of LED/photo diode switching)

–Different modulation including Optical MIMO

–Adaptive Modulation technique for different applications

–Using Equalization

Front end with gain control

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Challenges & Opportunities ..

V-LAN

–V-LAN on aeroplane

–Ubiquitous high data rate communication

Integration with Infrastructure

–RF/VLC Integration

–UP Link / Retrofitting

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Challenges & Opportunities …

VLC is cost effective and secured transmission system.

VLC Offers many challenging, novel and potential applications (both Indoor and outdoor).

Offers relief to RF based system

Need to be exploited further

System though has many challenges.

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Conclusion

Thank You for Your

Attention !

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Jiao Tong University Shanghai

3/25/2013 100

Contact: navin_kum3@yahoo.com, navin.k@cmrit.ac.in

Jiao Tong University Shanghai

Jiao Tong University Shanghai