Lighting and Full-Duplex Communication using Optical LED technology

1. Lighting and Full-Duplex Communication using Optical LED technology Dr. Fernando EE8114 Charles Lim Nov. 24, 2003

2. The LED Advantage • Consumes only one fourth or less power than incandescent bulbs. • 25,000 to 50,000 continuous hours of life • No RF EMI • Very secure compared to RF • Robust compared to other lighting devices • High data rate capability

3. Design Proposal

4. Picks up the data Power outlet Power outlet BPF BPF Tx LEDs & IR Rx Tx LEDs & IR Rx AC/DC AC/DC CPU CPU Mobile Terminal Mobile Terminal PLC Modem PLC Modem Demodulator Demodulator Rx LEDs & IR Tx Rx LEDs & IR Tx Power outlet Power outlet How to modulate the LED w/ Data? • PLC (Power Line Communications) • Use existing power outlets that act similarly to data ports and networks throughout the house to transfer data from the computer to the LED system • Currently only support low data rates (i.e. a few hundred kbps) • Easy to install and cheaper for already installed houses • PLC (Power Line Communications) • Use existing power outlets that act similarly to data ports and networks throughout the house to transfer data from the computer to the LED system • Currently only support low data rates (i.e. a few hundred kbps) • Easy to install and cheaper for already installed houses

5. Data used to modulate the power Fiber connector O-E converter BPF BPF Tx LEDs & IR Rx Tx LEDs & IR Rx AC/DC AC/DC Power outlet Power outlet CPU CPU Mobile Terminal Mobile Terminal E-O converter Demodulator Demodulator Rx LEDs & IR Tx Rx LEDs & IR Tx Fiber connector • Optical Fiber Communications • Expensive to install for already built houses. • Capable of carrying tremendously high data rates • Almost unlimited bandwidth for the home user for both optical wireless (LED) and optically connected (fiber) wired applications • Better option for pre-built houses where installation of fiber will be easier.

6. Factors affecting LED systems • Thermal Temperature • Packaging Type and System Integration • Multi-path Dispersion • Reflectivity of the Room • Downlink/Uplink Data rate • LED Power • Need for Channel Equalizer

7. Thermal Management • For LEDs to achieve long lifetimes in the range of 25,000 to 50,000 hours, the temperature of the junction must be under 75°C. • Also, once the junction temperature reaches over 125°C, problems with LEDs become a lot more common. • Packaging Type • Current packages have 300°C. • If assume room temperature 25°C, then minimum package thermal resistance is 50°C. • System Integration • Unlike incandescent bulbs, LEDs do not radiate wasted heat away from the part. It requires the device be properly cooled. • Design and installation of not only LEDs but the cooling system is critical as well for LED systems.

8. Multi-Path Dispersion • Main issue in optical wireless technology • Due to the large amount of lighting LEDs • Minimal interference from the white LEDs and IR LED due to spectral separation • Photodiodes also has spectral separation to minimize interference • IR and LED Tx linewidth chosen such that minimal interference with photodiodes. • Reflectivity of the room • Higher reflectivity means more dispersion • Depends on color and reflectivity of materials inside room • Downlink/Uplink data rate • Receiver and LED system circuitry determined by the downlink bandwidth • Downlink easier to design, larger power from lighting LEDs • Uplink data rate cannot be very high due to limited IR power • Uplink bandwidth restriction determined by IR transmitter and receiver design. • Higher data rates = Higher Cost

9. LED Power • Higher Power allows for faster data rates • Limitations in power output design due to government restrictions • Channel Equalizer • To achieve better data rates and reliability a dynamic channel equalizer is required. • Use LMS digital signal processing algorithm • LMS block is right after modulator and demodulator for both IR and light LEDs • Dynamically adjust downlink/uplink bit rates depending on current room BER • Increases reliability of system • Mobility is increased • Higher Efficiency

10. Signal Interferences

11. Simple RS232 LED Downlink System • Part of the project is to demonstrate a simple LED system and to prove it is feasible • TX Circuit • Consists of 10 super bright white LEDs driven by a 5V DC power supply and modulated by a RS232 Line Driver IC connected to a computer serial port. • RX Circuit • Consists of 3 visible light photodiodes and a comparator which detects optical signals and converts it to rs232 voltage levels White LEDs FREE SPACE Detector Circuit TX RX

12. Conclusion • This project achieves Lighting and communication using Optical wireless communication. • Through more research and design, optical wireless communications will eventually achieve: • Reliable high data rate transfers • No RF interference • Mobility and security • Minimal multi-path distortion • Higher power efficiency, lower transmit and receive power • Integrating Lighting and communication for home

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

14. References • [1] Bala Balasingam, Charles Lim, Gajendran Wignarajah, Jeyacanthan Nesarajah, Sarmila Selvaratnam, “Lighting and Communication from the same source”, 2003 ICUE (International Conference for Upcoming Engineers) • [2] Toshihiko Komine, Masao Nakagawa, “Integrated system of white LED visible-light communication and power-line communication”, 2002 IEEE • [3] Yuichi Tanaka, Shinichirou Haruyama, Masao Nakagawa, “Wireless Optical Transmissions with white colored LED for Wireless Home Links” , 2000 IEEE • [4] Tsunemasa Taguchi, Yamaguchi University, “Light Gets Solid”, OE Magazine, The Monthly Publication of SPIE October 2003 • [5] Srinath Aanegola, Jim Petroski, Emil Radkov, GELcore LLC, “Let There Be Light”, OE Magazine, The Monthly Publication of SPIE October 2003