Journal of Communications and Information Networks
Vol.2, No.4, Dec. 2017
DOI: 10.1007/s41650-017-0042-6
Research paper
Undersampled differential phase shift on-off
keying for optical camera communications
Niu Liu, Julian Cheng, Jonathan Francis Holzman
School of Engineering, The University of British Columbia, Kelowna, B.C., V1V 1V7, Canada
Abstract: OCC (Optical Camera Communication) has been proposed in recent years as a new technique
for visible light communications. This paper introduces the implementation and experimental demonstra-
tion of an OCC system. Phase uncertainty and phase slipping caused by camera sampling are the two
major challenges for OCC. In this paper, we propose a novel modulation scheme called undersampled
differential phase shift on–off keying to encode binary data bits without exhibiting any flicker to human
eyes. The phase difference between two consecutive samples conveys one-bit information, which can be
decoded by a low-frame-rate camera receiver. Error detection techniques are introduced to enhance the
reliability of the system. We present the hardware and software design of the proposed system, which is
implemented with a Xilinx FPGA and a Logitech commercial camera. Experimental results demonstrate
that a bit-error rate of 10
−5
can be achieved with 7.15 mW received signal power over a link distance of 15 cm.
Keywords: image sensor, light-emitting diode, optical camera communication, undersampled differential
phase shift on-off keying, visible light communication
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Citation: N. Liu, J. L. Cheng, J. F. Holzman. Undersampled differential phase shift on-off keying for optical
camera communications [J]. Journal of communications and information networks, 2017, 2(4): 47-56.
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1 Introduction
In recent years, the LED (Light-Emitting Diode) has
become the light source of choice for sustainable il-
lumination. LEDs are quickly replacing incandes-
cent lamps, given their improved brightness, lower
energy consumption, and longer lifespan. It is es-
timated that by replacing all existing light sources
with LEDs, the world electricity energy consumption
can be dramatically reduced by 50%
[1]
. The devel-
opment of LED illumination technology also offers
great opportunities for data transmission. Relevant
research of VLC (Visible Light Communication) with
LEDs originated in Japan around 2003 with the es-
tablishment of the VLCC (Visual Light Communi-
cation Consortium). Since then, VLC has attracted
significant research and development interests.
The first VLC standard, IEEE 802.15.7, was ini-
tiated in 2008 and completed in 2011. However,
VLC products have not emerged into the market-
place to any great extent. This perhaps largely re-
sults from the need to integrate VLC systems into
existing portable smart devices. OCC offers a means
for this integration
[2,3]
. Given the significant poten-
tial for OCC, an amendment is being made to the
VLC standard by the IEEE 802.15.7r1 OWC task
group. This revision is expected to be published
by 2018. There is an immense interest to integrate
OCC technology into billions of existing smart de-
vices, without requiring significant hardware modifi-
cation.
It should be noted, however, that challenges still
Manuscript received May 31, 2017; accepted Jun. 23, 2017