978-1-5090-1081-3/17/$31.00 ©2017 IEEE

2017 International Siberian Conference on Control and Communications (SIBCON)

LED-Based Visible Light Communication and

Positioning Technology and SoCs Tian Lang, Zening Li, Gang Chen and Albert Wang (aw@ece.ucr.edu)

Center for Ubiquitous Communications by Light, University of California, Riverside, CA 92521, USA

Abstract— The rapid deployment of high-energy-efficiency,

solid-state light emission diode (LED) lighting devices, replacing

the conventional luminaires devices, brings unprecedented

opportunities for alternative optical wireless communication and

navigation applications. This paper reviews the state-of-the-art of

LED-based visible light communications (VLC) and positioning

(VLP) technologies with a focus on system-on-a-chip (SoC)

integrated circuit (IC) designs.

Index Terms—Visible light communication, VLC, visible light

positioning, VLP, LED, optical wireless, rolling shutter, system-

on-a-chip, SoC, IC.

I. LED ILLUMINATION

With recent revolution on illumination technology, the

widely used incandescent and compact florescent light (CFL)

bulbs are being quickly replaced by solid-state Light Emitting

Diode (LED) devices. LED is a green lighting technology

featuring high energy efficiency of 120 lumens per watt today

and possibly 200 lumens per watt by 2020, compared clearly

more favorable than incandescent bulbs (~15 lumens per watt)

and CFLs (~73 lumens per watt) [1]. LED bulbs also have

much longer lifespan, at least 3 fold longer than traditional

bulbs. LED’s other advantages include compact form factor,

being “cold” and higher color rendering, making LEDs the

clear choice as the next-generation illuminating devices.

Solid-state LEDs can be switched ON/OFF at tens of MHz

without flickering to human eyes, which is equivalent to

modulation in communications. Therefore, LEDs can be used

to realize visible light communications, which makes the

dream of communicate as you see become a reality. The

revolutionary LED-based VLC technology has many

advantages over traditional RF-based wireless technologies [2-

5]: First, the unlicensed and unrestricted optical spectrum

offers a bandwidth up to 300THz, orders of magnitude wider

than the RF spectrum, hence, making wireless streaming at

multi-Gbps possible. Second, the radiation of visible light is

largely harmless and hence allows more emission power to

boost data rates and distance. Third, unable to penetrate walls,

VLC has higher security by nature. Fourth, being interference-

free, VLC technology can co-exist with and complement

existing RF technologies. Fifth, LEDs are much cheaper than

multi-GHz RF devices. Importantly, VLC communication can

take full use of the existing LED light infrastructure around the

world to realize “free” wireless applications. In addition to

VLC, LED enables visible light positioning, which addresses

many limiting factors inherent to RF-based navigation

technologies, such as the popular global positioning system

(GPS). LED-based VLP technology hence opens a door for

unlimited indoor and outdoor ranging and navigation

applications, such as smart traffics and smart hospitals [6-12].

II. VLC SYSTEM IN SOC

The interests in VLC technology have grown rapidly ever

since researchers from Keio University published their result

on a white LED in home network access method [13]. The

waves of VLC research led to the formation of Visible Light

Communication Consortium (VLCC) in Japan in 2003 [14] and

spreads globally [6-12]. Two standards, Visible Light

Communication System Standard and Visible Light ID System

Standard were proposed by VLCC in 2007. In Europe, hOME

Gigabit Access project (OMEGA) [15], sponsored by

European Union, has shown VLC as an alternative way to

support RF communication network in 2009. IEEE Standard

802.15.7 was established for VLC communications in 2011

[16], which standardizes VLC’s the links and physical layer

design specifications for system designs.

A. VLC Architecture

A VLC system has two main parts, a transmitter and a

receiver. Fig. 1 illustrates a typical VLC system diagram. A

simple transmitter consists of an LED luminaire, a driver

circuit and a modulation circuit, which modulates the data onto

the fast intensity switching light emitted from the LED. For the

LED luminaire, there are two methods to produce a white light,

blue LED with phosphor or Red-Green-Blue (RGB) LEDs

combination. The former method utilizes the blue light and the

yellow phosphor combination to produce a white light, which

is the most common method due to its simplicity and low cost.

The latter method utilizes the mixing of red, green and blue

lights to render a white, which is not as cost effective. The

driver and modulation circuit modulates the input electrical

signal and convert it into optical output signal. One of the VLC

design constraints is not to affect the primary function of the

LED bulb as an illumination device, as such, the performance

of VLC functions will be affected in general.

The receiver of a VLC system contains the optical receiver

and a demodulation circuit. There are two types of optical

receiver, photodetector (PD) and imaging sensor. PD devices

are commonly used in VLC systems. The current generated

depends on the received light intensity. Due to the lack of

phase information in the received visible light signal, intensity

modulation/direct detection (IMDD) scheme is typically used.

The imaging sensor is also called a camera sensor (CMOS or

CCD). It is available in almost mobile devices today, which has

the potential to make the VLC implementation as easy as

simply installing a VLC App without any optical receiver add-

2017 International Siberian Conference on Control and Communications (SIBCON)

on, provided the LED-based illumination infrastructure has

already enabled VLC modulation.

Fig. 1. A simplified block diagram of a conceptual VLC system.

B. VLC SoC Designs

Global research efforts on the VLC technology has resulted

in many demonstration of VLC testbed systems of varying

wireless streaming performance. So far, reported VLC systems

are bulky because of using commercial off-the-shelf (COST)

devices [2-8]. Unfortunately, while such COST-based VLC

testbeds are good for quick feasibility studies, they are

impractical for real-world applications and also have

fundamental limitation on VLC performance. It is apparent that

in order for LED-based VLC applications become a true reality,

IC-based system-on-a-chip (SoC) and/or system-in-a-package

(SiP) design is a must, which is an emerging challenge in VLC

system research. In [12], Dong reported the first single-chip

custom-designed VLC transceiver IC that successfully driven

an LED-based VLC system to stream data. This single-chip

VLC IC consists of opto-electrical signal conversion, filtering,

bandwidth enhancement, low-noise pre-amplification, power

amplification, and analog-to-digital conversion and digital

signal processing (DSP) functions.

1) Discrete Transceiver Design for VLC System

Fig. 2 depicts a typical VLC system allowing both host-

slave broadcasting (LED bulb to users) and peer-to-peer full-

duplex transceiving (user to user). The transmitting path

includes buffers, coding and OFDM modulation for better

signal quality, a pre-equalizer for wider bandwidth, driver and

DC biasing for large LED array, DEMUX to handle LED array

signals, and digital-to-analog convertor (DAC) and global

clock synchronization. The receiving channel consists of pre-

amplifier and main amplifier, high/low pass filters, ADC to

convert the received analog signals into digital, decoding and

demodulation to recover signal information, a post-equalizer to

enlarge receiver bandwidth, clock synchronization and CDR

(clock and data recovery) circuit to recover both clock and data

from incoming signals. Two types of photo sensors may be

used: a large PD array and a CMOS imager. A MUX circuit is

used for PD array to fuse the received parallel signals. MAC

blocks will be used for access control for multi-users. LVDS

can be used to remove background noises. On-chip ESD

protection is needed for real-world VLC products.

2) VLC Transceiver IC Design

[12] reports a SoC IC for the VLC transceiver as illustrated

in Fig. 3, which was designed and fabricated in a foundry

180nm BCDMOS technology. The VLC transceiver IC

consists of a LED luminaire transmitter, equalization control

unit, Manchester encoding and decoding block, phase lock

loop (PLL), voltage and current reference, and optical receiver.

It was designed to realize up to 64bit digital control for test

multiplexer control by the I2C protocol, I2C slave and 8 digital

registers. There are a total of 25 IO pads, which includes two

for testing mux outputs and two for I2C programming

interfaces. The IC die is 2mmX2mm and uses BGA bonding.

S2D

LED Driver

PLL

Manchester

Clock & Data

Recovery Recovered Clock

Manchester

Encoding

Comparator

LED Driver

Interface

Equalization

Control

Recovered Data

Data

Clock

Voltage &

Current

Reference

LA TIA

PLL_outI

2C Interface

Digital Logic

And Control

SCL

SDA

TIA

_ou

tp

TIA

_o

utn

Co

mp

_o

ut

DSP

Photodiode

LED

sw

VLC Transceiver

Fig.3. Illustration of the fully integrated transceiver SoC IC for LED-based

VLC system in 180nm BCDMOS [12].

Fig. 4 depicts the hierarchy of the VLC transceiver SoC IC.

The VLC transceiver can be categorized in 3 main functional

parts: IO pad-ring, Analog and Digital portions. The Analog

portion includes 4 blocks, which are transmitter, PLL, bandgap

and receiver. The transmitter block has Manchester encoder,

delay cells, equalizer and LED Driver. The receiver comprises

4 blocks, which are front-end, linear amplifiers, comparator

and Manchester decoder. The Digital portion includes I2C

slaves, I2C registers, signal start and stop detection, and a

counter. The IO Pad-ring portion has power on reset (POR)

designed to set the initial value of all of the digital logics and

power supply detection. The communication between I2C

master and slave is ensured by I2C buffer via I2C bus lines.

On-chip electrostatic discharge (ESD) protection is designed

for each IO pad. This VLC transceiver IC allows simultaneous

illumination and communication by LED. On the transmitter

side, pre-equalization and multi-stage amplifier enhance the

modulation bandwidth limited by the LEDs. The signal

waveform received through the visible light transmitted from

the LED luminaire is 12 MHz. On the receiver side, VLC-

specific TIA and comparator were designed. This VLC

transceiver SoC operates over a bandwidth of 50 MHz.

Fig. 2 Illustration of a LED/imager based full duplex VLC wireless system.

US

B Biasing

ClockSignal

1:N

DE

MU

X

TX

MACBuffer Coding DAC

OFDM

ModulationDriver

Pre-

Equalizer

M:1

MU

X

Pre-AmpAmp

Filter

DeMod De-Coding ADCRX

MAC

Post-

Equalizer

CDR LEDArray

PINArray

1:N

DE

MU

X

TX

MACBufferCodingDAC

OFDM

ModulationDriver

Pre-

Equalizer

Pre-Amp Amp

US

B

CDR

Filter

DeModDe-CodingADCRX

MAC

Biasing

Post-

Equalizer

Clock

Signal

LEDArray

2017 International Siberian Conference on Control and Communications (SIBCON)

Digital_TopAnalog_TopIO Padring

VLC_Transceiver

POR

ESD Padring

I2C Buffer

Test Mux Buffer

I2C Slave

I2C Register

Start_stop_det

Counters, etc.

Transmitter PLL Bandgap Receiver

Machester Encoder

Equalizer

Front-end

Linear Amplifiers

LED Driver

Comparator

VCO

PFD/CP

Divider

FilterManchester

Decoder

Power Domain

Delay Cells

Fig.4. Hierarchy of the VLC transceiver SoC in 180nm BCDMOS [12].

III. VISIBLE LIGHT POSITIONING SYSTEM

RF-based positioning technology has its limitation. For

example, GPS does not work indoor. RF wireless technologies

may be prohibited in certain environments, such as hospitals.

LED-based VLP technology may have many indoor/outdoor

ranging and navigation applications in addition to VLC

functions, for example, for smart traffics and smart hospitals.

A. VLP System

The positioning functionality of LED-based VLC is rapidly

developed with its unique advantages over its RF counterparts,

such as cellular, WiFi, Bluetooth and RFID. One advantage is

the utilization of visible light’s line of sight (LOS) property,

which enables the PD receiver to detect the rotation and

location of the target based on the information from a set of

reference LEDs. This advantage reduces the uncertainty caused

by hardware and antenna orientation. Another benefit from the

LOS property is that the multi-path effect can be ignored due to

its IMDD method compared to RF positioning techniques. The

deployment of VLP systems utilizing the LED illumination

infrastructure lays the ground for many positioning

applications, for example, asset and personnel tracking.

B. VLP Tracking Methods

Various tracking techniques using LED-based VLP

technology were developed. Fig. 5 shows a simple Proximity

method in which the grids are separated due to the difference

of three different signals. The simplicity of this method comes

with its limitation, i.e., the tracking precision depends heavily

on the grid density of its reference points [17]. This VLP

positioning technique is useful for smart hospitals to realize

asset and personnel tracking in real time.

Another technique is the scene analysis technique that

functions in two phases [18]. In phase one, it collects needed

finger prints such as on received signal strength (RSS), time of

arrival (TOA) and time difference of arrival (TDOA). In phase

two, the routine matches the real time data with those collected

fingerprints in phase one. This method is simple for signal

processing that requires matching only. However, fingerprint

collection sets the limit for many tracking applications. [19]

presents a triangulation method based on RSS, which utilizes

the method of angulation and multilateration. By using

multilateration, the position of the target is measured indirectly

from references such as TOA, RSS and TDOA. By using

angulation, the target location can be estimated by its relative

angle with respect to the reference.

Fig.5. A simple proximity method for VLP smart tracking [17].

C. Rolling Shutter Enabled Multi-View Geometry Positioning

Fig. 6 shows a new rolling shutter enabled positioning

method for a LED VLP tracking system for smart hospitals

[17]. The LED luminaires are individually modulated with a

unique frequency as their optical tags. Optical beacon can be

broadcasted via each LED operating at a unique frequency, so

that the smartphone camera can retrieve it from a reflected

surface by analyzing rolling shutter effect. It can also acquire

the beacon information from LED directly. The rolling shutter

effect works with the dark and white bands seen by the

smartphone camera from the modulated LED lights. The image

is processed to extract the frequency component corresponding

to different LEDs. These striped images will be processed to

retrieve different frequency illuminated by these LEDs. The

actual position of an object can be calculated by these acquired

frequency information and compared with a pre-installed map

of the setting, therefore, realizes asset/personnel tracking in

real time. This new LED-based VLP smart tracking method

utilizes both the multi-camera vision triangulation algorithm

and rolling shutter effect, and the multi-view geometry. The

design focus is to determine the offset between two camera

frames in order to derive the target position. Both

accelerometer and gyroscope sensors can be utilized to monitor

the pose changes between two frames. The relative position

and pose of the device are tracked over the entire positioning

process. Based on the relative position and pose of the previous

frames, the current camera frames are estimated in the global

frame. The estimation inaccuracy due to shot noises from the

sensors, approximation error, or temporary blocking of the

LED light can be resolved by using two-stage Kalman filter

[20]. Therefore, the new LED VLP smart tracking system is

able to utilize only one detected LED with known position and

built-in smartphone sensors, such as motion, position and

2017 International Siberian Conference on Control and Communications (SIBCON)

environment sensor, to track actual position even when the

optical link is temporarily blocked or the LED moves out of the

FOV of the camera momentarily [17].

Fig.6. Illustration of the new LED VLC smart tracking system [17].

IV. VLC AND VLP APPLICATIONS

The LED-based VLC and VLP technology is an alternative

solution for RF wireless communications and positioning. The

followings are a few application examples demonstrated [14].

1) Indoor Wireless Networking: The existing indoor LED

light infrastructures can be retrofitted to realize full duplex

wireless streaming. Due to the extremely wide bandwidth of

visible light, VLC communication can be a viable wireless

solution for big data communications. Fig. 7 shows a full

duplex LED VLC testbed at the UC-Light Center of University

of California [21], capable of streaming HD videos while

allowing wireless communications between the two terminals.

Fig. 8 shows a VLC system using the VLC transceiver SoC

designed in 180 BCDMOS technology for visible light

streaming [17].

2) Outdoor VLC Networking: Urban development can use

outdoor LED-based VLC systems to realize smart city

applications. For example, the LED display boards, street lights

and LED signs can be redesigned to form a grand wireless

network for a city, a community, airport buildings, sports

arenas, large parking structures and shopping centers,

essentially making the smart city concept a reality.

3) Smart Hospitals: Modern hospitals requires high-volume

information communications (e.g., for telemedicine) and real-

time asset and personnel management. RF wireless is not the

solution due to many limitations. Build the VLC/VLP

functions into the existing LED light infrastructure will achieve

high-throughput wireless streaming and accurate

asset/personnel tracking, hence, making smart hospital a reality.

Fig. 9 shows a demo of a VLC system at the Loma Linda

Medical Center designed by the UC-Light Center [14].

4) Smart Traffics:

Adding the VLC/VLP functions to street lights, street signs,

LED displays, and the head/tail lights of vehicles, will make a

huge real-time traffic data monitoring and collection network,

which can be used to realize truly smart traffic control

everywhere and anytime. Fig. 10 shows a demo VLP/VLC

vehicle at the UC-Light Center that features VLP navigation

and VLC wireless communications simultaneously.

V. SUMMARY

We review the basics and state-of-the-art of the new LED-

based VLC and VLP technologies and systems. Designs of

VLC/VLP SoCs are discussed for real-world applications. The

VLC/VLP technology opens a door to unlimited wireless

applications, including high-throughput wireless streaming for

big data applications, smart cities, smart hospitals and real-time

smart traffic control.

ACKNOWLEDGMENT

This work was partially supported by the MRPI Program of

California, National Science Foundation and the Department of

Defense of the USA.

Fig. 7 A dual-user LED VLC system for HD video streaming [14].

Fig. 8 A demo at the UC-Light Center uses the VLC SoC IC designed in an 180nm BCDMOS to realize visible light communication [14].

2017 International Siberian Conference on Control and Communications (SIBCON)

Fig. 9 Demo of a VLC system at the Loma Linda Medical Center [14].

Fig. 10 A demo vehicle with VLP navigation and VLC communications [14].

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