COL 11(10), 102201(2013) CHINESE OPTICS LETTERS October 10, 2013
Range-rate tradeof fs in the communication between LED
traffic lights and vehicles
Jinguo Quan (
???
III
)
1,2∗
, Weihao Liu (
444
ÓÓÓ
)
2
, Shuang Jin (
777
WWW
)
2
, and Yan Zhang (
ÜÜÜ
ñññ
)
1
1
Key Laboratory of Network Oriented Intelligent Computation, Shenzhen Graduate School,
Harbin Institute of Technology, Shenzhen 518055, China
2
Division of Information Science and Technology, Shenzhen Graduate School,
Tsinghua University, Shenzhen 518055, China
∗
Corresponding author: quanjg@gmail.com
Received June 3, 2013; accepted August 2, 2013; posted online September 29, 2013
Visible light communication between light emitting diode (LED) traffic lights and vehicles with a receiving
photodiode front-end is developed for intelligent transportation systems. In this letter, the communication
data rates for different ranges are evaluated. The data rates are based on real scenarios of the background
noise and path losses and are experimentally obtained with a testing system built upon commercial off-
the-shelf components. Comparisons of range-rate performance for different average noise levels are also
conducted with the use of red/yellow/green LED lights. Results show that achieving the data rates of
kilobits per second at a communication range of hundred meters is possible under the ordinary noise
scenario, a finding that is highly significant for practical applications.
OCIS codes: 220.0220, 350.0350.
doi: 10.3788/COL201311.102201.
As fourth generation light sources, light emitting diodes
(LEDs) have ga ined increasing po pularity in a variety of
applications from lighting to traffic signaling. LEDs have
shown superiority over traditional incandescent and flu-
orescent lamps. LEDs have high energy efficiency, long
life expectancy, little out-of-visible band optical ra dia-
tion, and easy maintenance. They are als o environmen-
tally friendly. Nowadays, traditional incandescent traffic
light lamps have been increasing ly replaced by LED light
sources.
Besides the advantages of lighting, LED can also be
modulated by input signals because of their semicon-
ductor prop e rty that is ideal for information transmis-
sion in outdoor vehicle communications. Since the vis-
ible light communication (VLC) between LED traffic
lights and vehicles has been proposed fo r intelligent trans-
portation systems
[1−3]
, extensive efforts have b e e n made
for traffic light-vehicle VLC base d on either photodi-
ode detectors
[4−6]
or imag e sensor detectors
[7,8]
. Im-
age se ns ors are generally capable of parallel transmission
and robustness against interfering light, whereas pho-
todiode sensors have lar ge modulation bandwidth and
less res ponse time. Researchers from Nagoya Univer-
sity performed experiments to demonstrate the excellent
LED tracking capability of photodiode-based systems
[4]
.
However, data from field exp e riments on the path loss
and background noise of photodiode-based traffic light-
vehicle VLC systems under practical scenarios remain in-
sufficient. Systematic a nalyses based o n empirical results
are also lacking.
In this letter, we conduct field experimental measure-
ment of real solar radiation noise and path loss in a
photodiode-based tr affic light–vehicle VLC system. Bas-
ing from the expe rimental results, we further examine
the range-rate pe rformance of a communication system
built upon commercial off-the-shelf components. The
range-rate performance is investigated to understand the
communication capability of a photodiode-based outdoor
VLC system. The results obtained from this study will
be highly significant for practical applications.
Figure 1 shows the general block diagram used in the
exp erimental measurement. To obtain the background
noise interference and line of s ight (LOS) path loss under
real scenarios, the experimental setups are rearrange d ac-
cordingly.
To measure background noise, the transmitter part is
removed from the system, as shown in Fig. 1. The re-
ceiver demodulation part is replaced by measurement de-
vices, which include a power meter and a spectrum an-
alyzer. In this way, both optical power and frequency
sp e ctrum of the background interfering light are empiri-
cally obtained.
To measure path loss, a signal generator with constant
signal amplitude replaces the transmitter modulation and
combines with the DC bias to drive the LED traffic light
lamp. In the receiver side, the spectrum analyzer records
the received signal. The carrier to noise density ratio of
the receiver is therefore determined when the transmitted
signal is a sine wave with a single frequency sin(ω
0
t + φ).
Then, the path loss can be obta ined from the transmitted
signal power and noise intensity.
Fig. 1. Block diagram of the experimental measurement.
1671-7694/2013/102201(4) 102201-1
c
2013 Chinese Optics Letters
资源评论
