Xianbo Li

Visible Light Communication System Design and Link Budget Analysis

This paper presents, for the first time, a systematic approach to visible light communication (VLC) transceiver design based on an analytical optical wireless link budget study. To obtain the signal-to-noise ratio at the receiver, the received signal power is predicted by modeling the transmitted optical power and the channel path loss, while the input-referred noise is estimated by characterizing the noise contribution from each of the receiver building blocks. Based on the targeted bit error rate (BER) and communication distance, a VLC transceiver using discrete components and a fully integrated CMOS VLC transmitter compliant with the IEEE 802.15.7 Standard have been designed and tested. Experimental results show that the measured BER agrees well with the proposed model for both the systems, validating our design approach and the link budget analysis.

A Fully Integrated IEEE 802.15.7 Visible Light Communication Transmitter With On-Chip 8-W 85% Efficiency Boost LED Driver

This paper presents the first IEEE 802.15.7 PHY-I standard compliant visible light communication (VLC) transmitter and LED driver SoC for location-based applications using standard white LED lights as beacons or broadcasters. Implemented in a 0.35μm CMOS process with 20-V high-voltage device, the mixed-signal SoC integrates a baseband DSP unit, a VLC modulator, and a switching boost converter with an on-chip power MOSFET. Designed to drive an array of up to 4×5 LEDs using batteries, the boost converter generates an output at 6-20 V from an input at 3-5V with a 92% peak efficiency and an 8-W rating. Measured VLC data rate up to 266 kb/s with 211-1 PRBS inputs is achieved at a PER of <;10% and transmission efficiency of 5 nJ/bit. The LED driver can simultaneously support nine dimming levels and VLC.

Design and Characterization of Active Matrix LED Microdisplays With Embedded Visible Light Communication Transmitter

This paper presents the design and characterization of the first active matrix light-emitting diode (AMLED) microdisplay with an embedded visible light communication (VLC) transmitter, enabling LED digital signage for location-based applications such as information broadcasters and indoor positioning beacons. The driver system-on-a-chip (SoC) integrates four identical macro-cells, each containing a pixel driver array, a row driver, a column driver, and a first-in first-out memory, to drive a wide quarter-VGA (WQVGA) display featuring 400 × 240 blue micro-LED (μLED) pixels fabricated on a single gallium nitride (GaN) substrate. The size of each μLED pixel is 30 × 30 μm2. At the system level, pulse-width modulation (PWM) superimposed with on-off keying modulation is proposed to accomplish grayscale control for display and simultaneously transmit VLC signal by modulating the μLED array. At the circuit level, a pixel driver cell composed of three transistors and one capacitor (3T1C) with a novel VLC function is employed to implement the control scheme. Flip-Chip bonding is adopted to establish connections between the WQVGA microdisplay and the AMLED driver SoC. Implemented in a 0.5-μm 2P3M CMOS process, the driver SoC enables a high-resolution microdisplay module to achieve 4-bit grayscale at a 100-Hz frame rate, while supporting 1.25-Mb/s VLC for a bit error rate <;10-5 up to 25-cm distance without a lens. When using optical lenses, the VLC distance is extended to >500 cm.

An AMLED microdisplay driver SoC with built-in 1.25-Mb/s VLC transmitter

This paper presents the first active matrix LED (AMLED) microdisplay driver with built-in visible light communication (VLC) transmitter. The wide quarter-VGA (WQVGA) display features 400×240 pixels of 30×30 μm2 micro-LEDs (μLED) on a single GaN IC flip-chip bonded to the proposed driver SoC. Pulse-width modulation (PWM) superimposed with on-off keying (OOK) modulation are employed for controlling the display grayscale and modulating the pixels with VLC data simultaneously. Implemented in 0.5-μm CMOS, the SoC enables a microdisplay module featuring 4-bit grayscale at 100-Hz frame rate while achieving 1.25-Mb/s lensless VLC up to 25 cm.

Recent advancements in visible light communication modulator SoCs

This paper presents two advanced visible light communication (VLC) modulator system-on-chips (SoCs). The first is an IEEE 802.15.7 PHY-I standard compliant VLC transmitter. The second is an active matrix LED microdisplay with embedded VLC function.