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.

Optical wireless communications (OWC) are emerging as cost-effective and practical solutions to the congested radio frequency-based wireless technologies. As part of OWC, optical camera communications (OCC) have become very attractive, considering recent developments in cameras and the use of fitted cameras in smart devices. OCC together with visible light communications (VLC) is considered within the framework of the IEEE 802.15.7m standardization. OCCs based on both organic and inorganic light sources as well as cameras are being considered for low-rate transmissions and localization in indoor as well as outdoor short-range applications and within the framework of the IEEE 802.15.7m standardization together with VLC. This paper introduces the underlying principles of OCC and gives a comprehensive overview of this emerging technology with recent standardization activities in OCC. It also outlines the key technical issues such as mobility, coverage, interference, performance enhancement, etc. Future research directions and open issues are also presented.

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.

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 user's 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.

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.

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.