Willy Anugrah Cahyadi

Experimental Demonstration of VLC-Based Vehicle-to-Vehicle Communications Under Fog Conditions

Vehicle-to-vehicle (V2V) communication using visible light communication (VLC) technology under fog conditions is presented. Fog is known as one of the most detrimental atmospheric conditions that causes outdoor optical wireless communications to be unreliable. The effect of the fog conditions is experimentally analyzed in the VLC-based V2V system. Recognizing the least attenuation coefficient and a taillight color of a vehicle, a red light-emitting diode (LED) was employed in the experiment. In addition, a Fresnel lens and multiple photodiodes are utilized to efficiently counteract the impairment caused by fog. The experimental results demonstrate that the proposed VLC-based V2V system offers a reliable V2V data transmission over the fog-impaired optical channel with a relatively high signal-to-noise ratio (SNR), even under a heavy-fog condition.

Mobile Phone Camera-Based Indoor Visible Light Communications With Rotation Compensation

Downlink visible light communication (VLC) using a mobile phone camera is presented. The proposed scheme consists of an 8 × 8 light-emitting diode (LED) array for data transmission and eight white LEDs for an adequate level of illumination. The white LEDs are also used to acquire camera focus and light metering. Moreover, an efficient rotation compensation feature is provided in the form of a special header frame called keyframe to allow multiple users to receive the data simultaneously at 90°, 180°, and 270° orientations. Unlike conventional LED allocation methods for the rotation compensation, this keyframe-based method improves the data rate significantly. The experimental results demonstrate that the data rate achieves up to 1280 bps, whereas the theoretical simulations exhibit a potential data rate of up to 5120 bps using the identical LED array. The proposed scheme can be considered to be an efficient short-range camera-based VLC in an indoor environment with advanced features such as illumination, relatively high data rate, and robust camera rotation compensation for multiuser access.

Patient monitoring using Visible Light uplink data transmission

Patient health monitoring technology presents great potential for future healthcare applications and Radio Frequency (RF) communication is the most popular medium for its implementation. This paper presents a static indoor patient monitoring scheme using uplink Visible Light Communication (VLC) suitable for hospital environments. VLC is considered instead of RF communication because of health concerns regarding continuous RF exposure to patients for health monitoring. The proposed scheme is designed for transmitting uplink patient data using VLC through On-Off Keying (OOK) modulation. Experiments were conducted with several body-sensors data transmitted using predefined headers. The experiment results show that the proposed VLC based patient monitoring scheme can offer accurate monitoring data transmission with minimal interference with the help of space diversity.

Optical Camera Communication: Motion over Camera

OCC is a pragmatic version of VLC based on a smart device camera that allows easier implementation of various services in smart devices. This article presents a flexible and novel motion detection scheme over a smart device camera in OCC. The motion detection is conducted in conjunction with a static downlink optical camera communication, where a mobile phone front camera is employed as the receiver and an 8 x 8 dot matrix LED as the transmitter. In addition to the 8 x 8 dot matrix LED for data transmission, 10 white LEDs are also employed for providing illumination, acquiring camera focus, and light metering. The motion detection or MoC is designed to detect the users finger movement through the OCC link via the camera. A simple but efficient quadrant division based motion detection algorithm is proposed for reliable and accurate detection of motion. The experiment and simulation results demonstrate that the proposed scheme is able to detect motion with a success probability of up to 96 percent in the mobile phone camera based OCC. It is envisioned that the proposed motion detection can facilitate cost-effective and convenient smart home environments in the OCC, where the provision of illumination and short-range wireless communications has already been addressed.

Efficient road surface detection using visible light communication

This paper presents an efficient road surface detection technique based on visible light communication (VLC). It uses light emitting diodes (LED) based car headlamps to illuminate the road surface and capture the diffuse and specular reflections from the road surface. Experiments are conducted indoors to validate its detection scheme and accuracy. Moreover, the proposed VLC based road surface detection is found to accurately estimate the level of wetness on wet roads.

Experimental demonstration of LED-based vehicle to vehicle communication under atmospheric turbulence

Visible light communication (VLC) has been extensively studied for vehicle-to-vehicle (V2V) communication due to its inherent benefits. The effect of atmospheric turbulence, particularly in rainy condition, on the V2V communication using VLC is examined. The experiments for the V2V communication system was implemented with a modified fixed decision threshold (MFDT) scheme in the presence of rain drops. In the proposed study, a red light emitting diode (LED) representing the taillight of a vehicle is employed for transmitting signal and a photodiode is used to recover the transmitted the data using MFDT. It is demonstrated that the proposed V2V communication using VLC under the rainy condition is accurate and reliable with the help of MFDT.

VLC physical layer design based on Pulse Position Modulation (PPM) for stable illumination

Visible Light Communication (VLC) is promising new technology to be applied in the lighting system infrastructure. This communication function should not interfere with the existing lighting system. In order to prevent from this interference, the utilized modulation scheme should have a limited dynamic range to avoid flickering and dimming effect. We propose Pulse Position Modulation (PPM) technique in our VLC system due to its very minimum dynamic range feature. This paper describes the design and analysis of VLC physical layer using PPM scheme to obtain a stable illumination. The design of physical layer consists of analog front end (AFE) circuit and the data processing which is implemented in microcontroller and FPGA. Based on the test results of our VLC system using low cost photo detector, the system is able to provide stable illumination while reaching the maximum data transfer rate of 20 kbps.

An Assistive VLC Technology for Smart Home Devices Using EOG

In recent years, assistive technology has been an emerging area of research to improve the quality of life, especially for the disabled and elderly people. In this paper, a novel electro-oculogram (EOG) signal based assistive visible light communication (VLC) in a smart home environment is presented. The eye movement is captured using silver chloride (AgCl) surface electrodes placed around eyes. The captured signal is further processed and transmitted using a VLC link to control smart home devices. To validate the proposed EOG-VLC based smart device control scheme, experiments were conducted. For the ease of the experiments, instead of an actual smart home device, we employed a digital door lock to verify its accurate control operation. Experiment results demonstrate that the proposed smart device control scheme operates accurately and reliably. Therefore, since the proposed scheme is based on a less hazardous VLC link, it is envisioned that the scheme can pave the way for greener and safer smart homes, particularly benefiting disabled and elderly people.

Dual camera-based split shutter for high-rate and long-distance optical camera communications

Smartphones have been very versatile communication devices. Cameras fitted in smartphones are primarily used to capture photographs and for relevant multimedia functions. Recently, smartphone cameras have been studied for short-range wireless communications. Camera-based optical wireless communication, termed optical camera communication (OCC), is a form of visible light communication. In the OCC, a camera is employed as the receiver, while either a light emitting diode or a liquid crystal display (LCD) is used as the transmitter. This paper proposes a downlink OCC scheme with a dual camera (receiver) and an LCD (transmitter) is employed, using a unique capture method called split shutter method. The split shutter method combined with dual camera offers a significantly increased capture rate as well as increased coverage distance. Experiments were conducted to verify the proposed dual camera-based split shutter OCC scheme. Compared with a standard camera shutter, it is found that the proposed method effectively increases the transmission rate by a factor of two under identical experimental conditions, achieving a maximum of 11,520 bits per second and a distance of up to 2 m using a 1280×720  pixels camera resolution. When compared with conventional rolling shutter OCCs, the proposed method offers four times farther the coverage distance at an identical resolution. It is also demonstrated that the data rate can be further increased when a larger number of transmitters are employed.

SOC design and FPGA implementation of Digital TV receiver

This paper proposes a System-on-chip (SoC) Architecture Design for real-time Digital TV receiver. The SoC includes RF interface, a Host Processor, a Physical Layer and Ethernet interface. The Physical Layer itself consists of Baseband Processing modules based on DVB-T standard which includes 2048-point FFT/IFFT, Channel Decoder, Synchronizer, Equalizer, Demodulator, etc. The SoC utilizes a 32-bit RISC based processor acting as the Host Processor. Both Processor and Physical layer works on 32 MHz clock cycle to ensure low power consumption. A real-time OS based on eCos is also used for controlling the Physical Layer and interfaces in a real-time basis. The system is implemented using FPGA and has been verified capable of receiving a realtime video transmitted by a standard digital TV transmitter/modulator.