MPhil Thesis Presentation
Techniques for Improving Li-Fi Data Rate for Display Systems with Visible Light Communication Capability

by Liusheng SUN

 :  19 Sep 2017 (Tue)
 :  2pm
Venue  :  Room 4475 (Lifts 25 &26), 4/F Academic Building, HKUST

Examination Committee
Prof Ross MURCH, ECE/HKUST (Chairperson)
Prof Patrick YUE, ECE/HKUST (Thesis Supervisor)
Visible light communication (VLC) using LEDs has recently attracted a great deal of research interest in Light-Fidelity (Li-Fi) applications. Previous studies mainly focus on the applications of simultaneous illumination and VLC. However, there are many LED-based displays, including LCD displays with LED backlights, OLED displays, and micro-LED displays, which can be exploited for the deployment of VLC using LEDs as transmitters. This thesis presents two decoding algorithms for Li-Fi data recovery and a VLC transmitter system-on-chip (SoC) with bandwidth improving techniques, focusing on simultaneous display and VLC applications.
The main challenge of VLC data recovery from a display is the varying received signal strength caused by changes in the displayed images or videos. This work proposes two Adaptive Threshold Decoding (ATD) algorithms which dynamically adjust the decision threshold voltage: Preamble-based ATD, utilizing the preamble sequence, and Section-based ATD, utilizing the characteristics of OOK modulation and Manchester encoding. The measured BER of a 4-frame/s micro-LED display is improved from 6.9×10-2 to 4.4×10-4 using the Preamble-based ATD algorithm compared with the conventional Constant Threshold Decision scheme, which is further improved to 3.6×10-4 by using Section-based ATD.
The proposed transmitter SoC is a second-generation active matrix light-emitting diode (AMLED) micro-display driver, simultaneously supporting display and VLC. The AMLED driver, consisting of a row driver, a column driver and proposed micro-LED pixel drivers, is flip-chip bonded with a blue gallium nitride (GaN) micro-LED array with 36×64 pixels, each measuring 40×40 μm2. Implemented in a 0.18-μm CMOS process, the AMLED micro-display with the proposed pixel driver can achieve a 20-Mb/s bit rate at 10 cm without a lens, which is four times as large as the 5-Mb/s modulation bit rate in the first generation.
*** ALL ARE WELCOME !! ***