Photon Netw Commun (2013) 25:60–72
Analysis of the effects of LED direction on the performance
of visible light communication system
Trong-Hop Do · Junho Hwang · Myungsik Yoo
Received: 2 January 2012 / Accepted: 5 December 2012 / Published online: 16 December 2012
© Springer Science+Business Media New York 2012
Abstract Visible light communication (VLC) is expected
to be the next generation of indoor wireless communication.
A VLC system uses many LED chips, and its performance
is greatly affected by the direction of light-emitting diodes
(LEDs). Normally, the LEDs are directed vertically down-
ward to the ﬂoor. In this paper, we introduce an LED layout
scheme in which the LEDs tilt toward the room corners. The
effects of changing LED direction on system performance,
including illuminance, received power, and SNR, are ana-
lyzed. The analysis is then veriﬁed by the simulations.
Keywords Light-emitting diodes · Photo diodes · Signal-
to-noise ratio · Illuminance · Angle
In recent years, lighting technology has developed rapidly.
White light-emitting diodes (LEDs) with many desired prop-
erties such as low power consumption, low voltage, long life-
time, small size, and cool operation are promised to be the
lighting devices of the future.
Besides being used as lighting devices, white LEDs have
been studied as optical wireless communication devices.
Similar to infrared light, the visible light radiated from white
LEDs can also be used to transmit data. For example, digital
data can be represented by the presence or absence of light as
in the case of on-off keying modulation. Furthermore, visible
light is still safe for human health even when the transmitted
power is very high. Therefore, not only can a visible light
communication (VLC) system supply high power lighting,
T.-H. Do · J. Hwang · M. Yoo (
School of Electronic Engineering, Soongsil University, Seoul, Korea
it can also supply a broadband link for wireless communi-
cation. Because of these merits, visible light communication
is said to be one of the candidates for the next generation of
indoor wireless data transmission systems .
In [1–6], the VLC system has been proposed and evalu-
ated. From then on, there have been many efforts to enhance
the performance of VLC system. [7–10] proposed equal-
izations method applied for the transmitter or receiver to
improve the data rate. Usually, a VLC system use many
LED chips. In [1–10], the LEDs are all placed on the ceiling
and directed vertically downward to the ﬂoor. Our previous
work  proposed an LED layout in which the LEDs tilt
toward the room corners at different angles. By simulation,
we showed that the performance of VLC system, including
illuminance, received power, and SNR, is greatly affected by
the direction of LEDs. Especially, by tilting LEDs toward
the room corners, the SNR which is directly proportional to
the link quality provided by VLC system can be increased. In
this paper, we analyze the effects of changing LED direction,
which is then veriﬁed by simulations.
The rest of the paper is organized as follows: In Sect. 2,we
explain the lighting design and the tilted LED layout scheme.
The basis performance of VLV system will be introduced in
Sect. 3. The effects of changing LED direction on system
performance are analyzed in Sect. 4. We show the simula-
tion results and verify the analysis in Sect. 5. Finally, the
conclusion is made in Sect. 6.
2 Room model and LED layout scheme
2.1 Basis room model and LED placement
Our VLC system is modeled in a room measuring 5×5×3m
A2×2 lighting equipment grid with communication function