LED-to-LEDVisibleLightCommunication.pdfVIP

An LED-to-LED Visible Light Communication System with Software-Based Synchronization 1,2 2 2 1 Stefan Schmid , Giorgio Corbellini , Stefan Mangold , Thomas R. Gross 1ETH Zurich, 2Disney Research Zurich Motivation – Networking Toys ? Requirements: ? Low bit rate communication ? Short distances ? Cost-effective ? LED-to-LED communication: ? Fulfills requirements ? Communication is visible ? No radio waves ? Reuses already existing components ? Low-complexity 2 Outline ? Motivation ? Technology ? LED as a Transmitter ? LED as a Receiver ? Synchronization ? Implementation and Platform ? Evaluation ? Conclusions 3 Transmitter ? On-off keying ? LED on ? symbol ONE ? LED off ? symbol ZERO ? Requirements: ? No flickering ? Constant brightness ? Example: Encode 1 bit directly with a symbol ? 1-byte message: 1000 0001 ? ON OFF OFF OFF OFF OFF OFF ON ? Long OFF-sequence changes the perceived brightness ? Even longer OFF-sequence introduces flickering 4 Manchester Coding ? 0 ? 1 0 ?ONE ZERO ? 1 ? 0 1 ? ZERO ONE ? Uniform distribution of ONE and ZERO symbols ? Redundancy 5 LEDs as Light Receivers ? LEDs can be used as light receivers [Dietz et al, 2003] ? LED used as a receiver: ? Reduces complexity ? Cost-effective ? Limited light sensitivity But ? Short range communication ? Low data rates still possible P. Dietz, W. Yerazunis, and D. Leigh, “Very low-cost sensing and communication using bidirecti