Recently, there have been many attempts to converge LED with IT technology. Among them, Visible Light
Communication (VLC), which is the convergence of illumination and communication, has emerged. In VLC system,
both lighting and communication can be simultaneously implemented. By considering both terms together,
VPPM(Variable Pulse Position Modulation) modulation scheme is proposed by the IEEE 802.15.7 standard group. It
uses binary PPM (Pulse Position Modulation) for communication and PWM (Pulse Width Modulation) for dimming
control. In this paper, we introduce the implementation of VLC demonstration system based on VPPM modulation
scheme. By changing the pulse width of VPPM signal, we can support 25%, 50% and 75% dimming. In addition, our
VLC demonstration system provides a new power system using solar cell. By receiving the VPPM modulated visible
light signal in the receiver end, we turn on the receiver power and start the system operation to decode the transmitted
signal. By using ATmega128 8bit Micro Controller Unit (MCU) by ATMEL and Q3 XLamp XP-E LEDs of Cree, our
system provides about 2kbps data rate with 2.5kHz optical rate in more than 30cm distance. By implementing DM S/W,
we show the bit error rate (BER) and achievable data rate (ADR) of our demonstration system.
In this paper, we propose a brand new communication concept, called as "vision communication" based on LED array
and image sensor. This system consists of LED array as a transmitter and digital device which include image sensor such
as CCD and CMOS as receiver. In order to transmit data, the proposed communication scheme simultaneously uses the
digital image processing and optical wireless communication scheme. Therefore, the cognitive communication scheme is
possible with the help of recognition techniques used in vision system. By increasing data rate, our scheme can use LED
array consisting of several multi-spectral LEDs. Because arranged each LED can emit multi-spectral optical signal such
as visible, infrared and ultraviolet light, the increase of data rate is possible similar to WDM and MIMO skills used in
traditional optical and wireless communications. In addition, this multi-spectral capability also makes it possible to avoid
the optical noises in communication environment. In our vision communication scheme, the data packet is composed of
Sync. data and information data. Sync. data is used to detect the transmitter area and calibrate the distorted image
snapshots obtained by image sensor. By making the optical rate of LED array be same with the frame rate (frames per
second) of image sensor, we can decode the information data included in each image snapshot based on image
processing and optical wireless communication techniques. Through experiment based on practical test bed system, we
confirm the feasibility of the proposed vision communications based on LED array and image sensor.
Recently, indoor LED lighting can be considered for constructing green infra with energy saving and additionally
providing LED-IT convergence services such as visible light communication (VLC) based location awareness and
navigation services. For example, in case of large complex shopping mall, location awareness to navigate the destination
is very important issue. However, the conventional navigation using GPS is not working indoors. Alternative location
service based on WLAN has a problem that the position accuracy is low. For example, it is difficult to estimate the
height exactly. If the position error of the height is greater than the height between floors, it may cause big problem.
Therefore, conventional navigation is inappropriate for indoor navigation. Alternative possible solution for indoor
navigation is VLC based location awareness scheme. Because indoor LED infra will be definitely equipped for providing
lighting functionality, indoor LED lighting has a possibility to provide relatively high accuracy of position estimation
combined with VLC technology. In this paper, we provide a new VLC based positioning system using visible LED lights
and image sensors. Our system uses location of image sensor lens and location of reception plane. By using more than
two image sensor, we can determine transmitter position less than 1m position error. Through simulation, we verify the
validity of the proposed VLC based new positioning system using visible LED light and image sensors.
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