Lighting and Full-Duplex Communication using

Optical LED technology

Charles LimNov. 24, 2003

Dr. FernandoEE8114

The LED AdvantageThe LED Advantage

Consumes only one fourth or less power Consumes only one fourth or less power than incandescent bulbs.than incandescent bulbs.

25,000 to 50,000 continuous hours of 25,000 to 50,000 continuous hours of lifelife

No RF EMI No RF EMI Very secure compared to RFVery secure compared to RF Robust compared to other lighting Robust compared to other lighting

devicesdevices High data rate capabilityHigh data rate capability

Design ProposalDesign Proposal

How to modulate the LED w/ How to modulate the LED w/ Data?Data?

PLC (Power Line Communications)PLC (Power Line Communications) Use existing power outlets that act similarly to data ports and Use existing power outlets that act similarly to data ports and

networks throughout the house to transfer data from the networks throughout the house to transfer data from the computer to the LED systemcomputer to the LED system

Currently only support low data rates (i.e. a few hundred Currently only support low data rates (i.e. a few hundred kbps)kbps)

Easy to install and cheaper for already installed housesEasy to install and cheaper for already installed houses

PLC (Power Line Communications)PLC (Power Line Communications) Use existing power outlets that act similarly to data ports and Use existing power outlets that act similarly to data ports and

networks throughout the house to transfer data from the networks throughout the house to transfer data from the computer to the LED systemcomputer to the LED system

Currently only support low data rates (i.e. a few hundred Currently only support low data rates (i.e. a few hundred kbps)kbps)

Easy to install and cheaper for already installed housesEasy to install and cheaper for already installed houses

CPU PLC Modem

Power outlet

Power outlet

BPF

Picks up the data

AC/DC

Tx LEDs & IR Rx

Rx LEDs & IR TxDemodulatorMobileTerminalCPU PLC Modem

Power outlet

Power outlet

BPF

AC/DC

Tx LEDs & IR Rx

Rx LEDs & IR TxDemodulatorMobileTerminal

Optical Fiber CommunicationsOptical Fiber Communications Expensive to install for already built houses.Expensive to install for already built houses. Capable of carrying tremendously high data ratesCapable of carrying tremendously high data rates Almost unlimited bandwidth for the home user for both Almost unlimited bandwidth for the home user for both

optical wireless (LED) and optically connected (fiber) optical wireless (LED) and optically connected (fiber) wired applicationswired applications

Better option for pre-built houses where installation of Better option for pre-built houses where installation of fiber will be easier.fiber will be easier.

CPU E-O converter

BPF

Data used to modulate the power

AC/DC

Tx LEDs & IR Rx

Rx LEDs & IR TxDemodulatorMobileTerminalCPU

Fiber connector

BPF

AC/DC

Tx LEDs & IR Rx

Rx LEDs & IR TxDemodulatorMobileTerminal

Fiber connector

O-E converter

Power outletPower outlet

Factors affecting LED Factors affecting LED systemssystems

Thermal TemperatureThermal Temperature Packaging Type and System Packaging Type and System

IntegrationIntegration Multi-path DispersionMulti-path Dispersion Reflectivity of the RoomReflectivity of the Room Downlink/Uplink Data rateDownlink/Uplink Data rate LED PowerLED Power Need for Channel EqualizerNeed for Channel Equalizer

Thermal ManagementThermal Management For LEDs to achieve long lifetimes in the range of For LEDs to achieve long lifetimes in the range of

25,000 to 50,000 hours, the temperature of the junction 25,000 to 50,000 hours, the temperature of the junction must be under 75°C.must be under 75°C.

Also, once the junction temperature reaches over 125°C, Also, once the junction temperature reaches over 125°C, problems with LEDs become a lot more common. problems with LEDs become a lot more common.

Packaging Type Packaging Type Current packages have 300°C. Current packages have 300°C. If assume room temperature 25°C, then minimum If assume room temperature 25°C, then minimum

package thermal resistance is 50°C.package thermal resistance is 50°C.

System IntegrationSystem Integration Unlike incandescent bulbs, LEDs do not radiate wasted Unlike incandescent bulbs, LEDs do not radiate wasted

heat away from the part. It requires the device be heat away from the part. It requires the device be properly cooled.properly cooled.

Design and installation of not only LEDs but the cooling Design and installation of not only LEDs but the cooling system is critical as well for LED systems. system is critical as well for LED systems.

Multi-Path DispersionMulti-Path Dispersion Main issue in optical wireless technology Main issue in optical wireless technology Due to the large amount of lighting LEDs Due to the large amount of lighting LEDs Minimal interference from the white LEDs and IR LED due to Minimal interference from the white LEDs and IR LED due to

spectral separationspectral separation Photodiodes also has spectral separation to minimize Photodiodes also has spectral separation to minimize

interferenceinterference IR and LED Tx linewidth chosen such that minimal IR and LED Tx linewidth chosen such that minimal

interference with photodiodes.interference with photodiodes.

Reflectivity of the roomReflectivity of the room Higher reflectivity means more dispersionHigher reflectivity means more dispersion Depends on color and reflectivity of materials inside roomDepends on color and reflectivity of materials inside room

Downlink/Uplink data rateDownlink/Uplink data rate Receiver and LED system circuitry determined by the Receiver and LED system circuitry determined by the

downlink bandwidth downlink bandwidth Downlink easier to design, larger power from lighting LEDsDownlink easier to design, larger power from lighting LEDs Uplink data rate cannot be very high due to limited IR powerUplink data rate cannot be very high due to limited IR power Uplink bandwidth restriction determined by IR transmitter Uplink bandwidth restriction determined by IR transmitter

and receiver design. and receiver design. Higher data rates = Higher CostHigher data rates = Higher Cost

LED PowerLED Power Higher Power allows for faster data ratesHigher Power allows for faster data rates Limitations in power output design due to government Limitations in power output design due to government

restrictionsrestrictions

Channel EqualizerChannel Equalizer To achieve better data rates and reliability a dynamic To achieve better data rates and reliability a dynamic

channel equalizer is required.channel equalizer is required. Use LMS digital signal processing algorithmUse LMS digital signal processing algorithm LMS block is right after modulator and demodulator for LMS block is right after modulator and demodulator for

both IR and light LEDsboth IR and light LEDs Dynamically adjust downlink/uplink bit rates depending Dynamically adjust downlink/uplink bit rates depending

on current room BERon current room BER Increases reliability of systemIncreases reliability of system Mobility is increasedMobility is increased Higher EfficiencyHigher Efficiency

Signal InterferencesSignal Interferences

Simple RS232 LED Downlink Simple RS232 LED Downlink SystemSystem

Part of the project is to demonstrate a Part of the project is to demonstrate a simple LED system and to prove it is feasiblesimple LED system and to prove it is feasible TX CircuitTX Circuit

Consists of 10 super bright white LEDs driven by a 5V DC Consists of 10 super bright white LEDs driven by a 5V DC power supply and modulated by a RS232 Line Driver IC power supply and modulated by a RS232 Line Driver IC connected to a computer serial port.connected to a computer serial port.

RX CircuitRX Circuit Consists of 3 visible light photodiodes and a comparator which Consists of 3 visible light photodiodes and a comparator which

detects optical signals and converts it to rs232 voltage levelsdetects optical signals and converts it to rs232 voltage levels

TX RX Whit

eLEDs

Detector

Circuit

FREE SPACE

ConclusionConclusion This project achieves Lighting and This project achieves Lighting and

communication using Optical wireless communication using Optical wireless communication. communication.

Through more research and design, optical Through more research and design, optical wireless communications will eventually wireless communications will eventually achieve:achieve: Reliable high data rate transfers Reliable high data rate transfers No RF interference No RF interference Mobility and securityMobility and security Minimal multi-path distortionMinimal multi-path distortion Higher power efficiency, lower transmit and receive Higher power efficiency, lower transmit and receive

powerpower Integrating Lighting and communication for homeIntegrating Lighting and communication for home

Conclusion……Conclusion……Future of Wireless communication ……….

ReferencesReferences [1] Bala Balasingam, Charles Lim, Gajendran Wignarajah, [1] Bala Balasingam, Charles Lim, Gajendran Wignarajah,

Jeyacanthan Nesarajah, Sarmila Selvaratnam, “Lighting and Jeyacanthan Nesarajah, Sarmila Selvaratnam, “Lighting and Communication from the same source”, 2003 ICUE (International Communication from the same source”, 2003 ICUE (International Conference for Upcoming Engineers)Conference for Upcoming Engineers)

[2] Toshihiko Komine, Masao Nakagawa, “Integrated system of [2] Toshihiko Komine, Masao Nakagawa, “Integrated system of white LED visible-light communication and power-line white LED visible-light communication and power-line communication”, 2002 IEEEcommunication”, 2002 IEEE

[3] Yuichi Tanaka, Shinichirou Haruyama, Masao Nakagawa, [3] Yuichi Tanaka, Shinichirou Haruyama, Masao Nakagawa, “Wireless Optical Transmissions with white colored LED for “Wireless Optical Transmissions with white colored LED for Wireless Home Links” , 2000 IEEEWireless Home Links” , 2000 IEEE

[4] Tsunemasa Taguchi, Yamaguchi University, “Light Gets Solid”, [4] Tsunemasa Taguchi, Yamaguchi University, “Light Gets Solid”, OE Magazine, The Monthly Publication of SPIE October 2003OE Magazine, The Monthly Publication of SPIE October 2003

[5] Srinath Aanegola, Jim Petroski, Emil Radkov, GELcore LLC, “Let [5] Srinath Aanegola, Jim Petroski, Emil Radkov, GELcore LLC, “Let There Be Light”, OE Magazine, The Monthly Publication of SPIE There Be Light”, OE Magazine, The Monthly Publication of SPIE October 2003 October 2003